ui: add deb and github_deb usage instructions (#113)

## Why

The `deb` and `github_deb` repository types had no tailored "How do I use this?" snippets in the UI — they fell through to the generic default (curl-a-file-by-path), which does not tell a user how to actually wire the repo into apt. This adds real, end-to-end-validated apt instructions mirroring how the existing package types (rpm, npm, etc.) are handled.

## How

- Adds a `case 'deb':` to `buildSnippets` that branches on `isLocal`: a flat real apt repo served at `/api/v1/local/<name>/ ./` with `[trusted=yes]` plus a publish-a-.deb snippet for locals, and a caching-proxy `deb <proxy> <suite> <component>` form (upstream-signed, no `[trusted=yes]`) for remotes.
- Adds a `case 'github_deb':` emitting the metadata-only flat form `deb [trusted=yes] <proxy>/ ./`, whose index is synthesized from a GitHub repo's release .deb assets.
- Reuses the existing `url`/`proxy`/`isLocal` helpers and matches the surrounding case style; leaves the rpm and other cases untouched.

Reviewed-on: #113
Co-authored-by: unkin-agent <unkin-agent@unkin.net>
Co-committed-by: unkin-agent <unkin-agent@unkin.net>

README.md

@@ -111,6 +111,71 @@ resource "artifactapi_remote_github_rpm" "acme-tools" {
 The repo is multi-arch (no `$basearch` needed) — `dnf` selects matching packages
 from the synthesized metadata.
 
+### GitHub authentication
+
+Anonymous GitHub is capped at **60 requests/hour** and cannot read private
+repositories. Configure a **server-level GitHub credential** to raise the ceiling
+to roughly **5000 requests/hour** and to read private-repo release assets. The
+credential is a process-wide machine identity applied by default to *every*
+outbound GitHub request — the releases scan, the ranged asset-header fetches, and
+the generic-github byte proxy that streams private release assets.
+
+The credential is read from the environment (deliver it from a Vault or
+Kubernetes secret). It is **never** stored per-remote in the database, **never**
+returned by any API, and **never** logged. Configure **exactly one** mode.
+
+**Precedence.** A remote's own `username`/`password` credential still wins for
+that remote's requests; the server credential is the default for everything else.
+With no credential configured at all, requests stay anonymous (current behavior).
+Partial configuration (e.g. an App id with no private key) is a **startup error**
+— artifactapi fails closed rather than silently falling back to anonymous.
+
+Both modes share the syncer's single global rate limiter, so a token simply
+raises the effective GitHub ceiling; the default limiter settings stay safe.
+
+#### Mode 1 — Personal Access Token (minimum viable, recommended for free accounts)
+
+Set `GITHUB_TOKEN`. It is sent as `Authorization: Bearer <token>`.
+
+Recommended free-account setup — a **fine-grained PAT** scoped to just the target
+repositories:
+
+1. GitHub → *Settings → Developer settings → Personal access tokens →
+   Fine-grained tokens → Generate new token*.
+2. Limit *Repository access* to the specific repo(s) serving releases.
+3. Grant repository permissions **Contents: Read-only** and **Metadata:
+   Read-only** (Metadata is mandatory and auto-selected).
+
+A classic PAT with the `repo` scope also works but is broader than necessary.
+
+```bash
+GITHUB_TOKEN=github_pat_xxxxxxxx
+```
+
+#### Mode 2 — GitHub App installation token (proper machine identity)
+
+A GitHub App is not tied to a personal account and can be created and installed on
+free personal repos. artifactapi mints a short-lived RS256 **JWT** from the app
+private key, exchanges it at `POST /app/installations/{id}/access_tokens` for a
+~1-hour **installation access token**, caches that token, and refreshes it a few
+minutes before expiry (thread-safe, single-flighted).
+
+1. GitHub → *Settings → Developer settings → GitHub Apps → New GitHub App*.
+2. Under *Permissions → Repository permissions* grant **Contents: Read-only**
+   (Metadata: Read-only is implied).
+3. Generate a **private key** (downloads a PEM) and note the **App ID**.
+4. *Install* the App on the account and select the target repositories, then read
+   the **Installation ID** from the installation URL
+   (`.../settings/installations/<installation-id>`).
+
+```bash
+GITHUB_APP_ID=123456
+GITHUB_APP_INSTALLATION_ID=7654321
+GITHUB_APP_PRIVATE_KEY_PATH=/etc/artifactapi/github-app.pem
+# or inline PEM (e.g. mounted from a secret):
+# GITHUB_APP_PRIVATE_KEY="-----BEGIN RSA PRIVATE KEY-----\n...\n-----END RSA PRIVATE KEY-----"
+```
+
 ## Terraform
 
 Remotes and virtuals are managed by Terraform. Each package type has its own resource:
@@ -277,6 +342,11 @@ S3 client supports MinIO, Ceph RGW, and AWS S3 (via minio-go).
 | `GITHUB_SYNC_BURST` | `5` | Token-bucket burst for the shared limiter |
 | `GITHUB_SYNC_WORKERS` | `3` | Concurrent `github_rpm` scan workers |
 | `GITHUB_SYNC_POLL_INTERVAL` | `60` | Base scheduler tick in seconds; per-remote cadence is its `mutable_ttl`, enforced by the DB lease |
+| `GITHUB_TOKEN` | | Server-level GitHub PAT (fine-grained or classic), sent as `Authorization: Bearer`. Applies to every GitHub request; per-remote creds override it. See [GitHub authentication](#github-authentication) |
+| `GITHUB_APP_ID` | | GitHub App id (App auth mode; mutually exclusive with `GITHUB_TOKEN`) |
+| `GITHUB_APP_INSTALLATION_ID` | | GitHub App installation id |
+| `GITHUB_APP_PRIVATE_KEY` | | GitHub App private key, inline PEM |
+| `GITHUB_APP_PRIVATE_KEY_PATH` | | GitHub App private key, file path (alternative to inline PEM) |
 
 ## Development
 

e2e-docker/local_test.go

@@ -8,6 +8,8 @@ import (
 	"strings"
 	"testing"
 	"time"
+
+	"git.unkin.net/unkin/artifactapi/internal/testsupport"
 )
 
 func uploadFile(t *testing.T, repo, filePath string, body []byte, contentType string) {
@@ -91,3 +93,46 @@ func TestLocalRPMRepodata(t *testing.T) {
 		t.Fatalf("repomd.xml not a valid repodata document: %s", s)
 	}
 }
+
+// TestLocalDebRepo uploads a .deb and validates that the flat apt index
+// (Packages / Release) is generated automatically from the parsed control
+// stanza (the deb-local analog of rpm repodata generation).
+func TestLocalDebRepo(t *testing.T) {
+	createRepo(t, `{"name":"local-deb","package_type":"deb","repo_type":"local"}`)
+	defer deleteRepo(t, "local-deb")
+
+	deb := testsupport.MinimalDeb("e2e-testpkg", "1.0.0", "amd64")
+	uploadFile(t, "local-deb", "e2e-testpkg_1.0.0_amd64.deb", deb, "application/vnd.debian.binary-package")
+
+	// The index is generated asynchronously after upload; poll for it.
+	resp, body := getEventually(t, api("/api/v1/local/local-deb/Packages"), 15*time.Second)
+	if resp.StatusCode != http.StatusOK {
+		t.Fatalf("Packages: status %d: %s", resp.StatusCode, body)
+	}
+	pkgs := string(body)
+	for _, want := range []string{"Package: e2e-testpkg", "Version: 1.0.0", "Architecture: amd64", "Filename: pool/e2e-testpkg_1.0.0_amd64.deb", "SHA256:"} {
+		if !strings.Contains(pkgs, want) {
+			t.Fatalf("Packages missing %q:\n%s", want, pkgs)
+		}
+	}
+
+	resp, body = doRequest(t, http.MethodGet, api("/api/v1/local/local-deb/Release"), nil, "")
+	if resp.StatusCode != http.StatusOK {
+		t.Fatalf("Release: status %d: %s", resp.StatusCode, body)
+	}
+	rel := string(body)
+	for _, want := range []string{"Architectures: amd64", "SHA256:", "Packages"} {
+		if !strings.Contains(rel, want) {
+			t.Fatalf("Release missing %q:\n%s", want, rel)
+		}
+	}
+
+	// The .deb downloads back byte-identical from its pool path.
+	resp, body = doRequest(t, http.MethodGet, api("/api/v1/local/local-deb/pool/e2e-testpkg_1.0.0_amd64.deb"), nil, "")
+	if resp.StatusCode != http.StatusOK {
+		t.Fatalf("download deb: status %d: %s", resp.StatusCode, body)
+	}
+	if !bytes.Equal(body, deb) {
+		t.Fatalf("deb content mismatch")
+	}
+}

go.mod

@@ -9,11 +9,13 @@ require (
 	github.com/go-chi/chi/v5 v5.3.0
 	github.com/google/uuid v1.6.0
 	github.com/jackc/pgx/v5 v5.10.0
+	github.com/klauspost/compress v1.19.2
 	github.com/minio/minio-go/v7 v7.2.0
 	github.com/redis/go-redis/v9 v9.20.0
 	github.com/testcontainers/testcontainers-go v0.42.0
 	github.com/testcontainers/testcontainers-go/modules/postgres v0.42.0
 	github.com/testcontainers/testcontainers-go/modules/redis v0.42.0
+	github.com/ulikunitz/xz v0.5.16
 	golang.org/x/crypto v0.51.0
 	golang.org/x/time v0.15.0
 	gopkg.in/yaml.v3 v3.0.1
@@ -51,7 +53,6 @@ require (
 	github.com/jackc/pgpassfile v1.0.0 // indirect
 	github.com/jackc/pgservicefile v0.0.0-20240606120523-5a60cdf6a761 // indirect
 	github.com/jackc/puddle/v2 v2.2.2 // indirect
-	github.com/klauspost/compress v1.18.6 // indirect
 	github.com/klauspost/cpuid/v2 v2.2.11 // indirect
 	github.com/klauspost/crc32 v1.3.0 // indirect
 	github.com/lucasb-eyer/go-colorful v1.4.0 // indirect

go.sum

@@ -85,8 +85,8 @@ github.com/jackc/pgx/v5 v5.10.0 h1:VhSvgU2jSli8o3AqIEOTJr7rZwAEUVo4E4XhR94Zfr0=
 github.com/jackc/pgx/v5 v5.10.0/go.mod h1:mal1tBGAFfLHvZzaYh77YS/eC6IX9OWbRV1QIIM0Jn4=
 github.com/jackc/puddle/v2 v2.2.2 h1:PR8nw+E/1w0GLuRFSmiioY6UooMp6KJv0/61nB7icHo=
 github.com/jackc/puddle/v2 v2.2.2/go.mod h1:vriiEXHvEE654aYKXXjOvZM39qJ0q+azkZFrfEOc3H4=
-github.com/klauspost/compress v1.18.6 h1:2jupLlAwFm95+YDR+NwD2MEfFO9d4z4Prjl1XXDjuao=
-github.com/klauspost/compress v1.18.6/go.mod h1:cwPg85FWrGar70rWktvGQj8/hthj3wpl0PGDogxkrSQ=
+github.com/klauspost/compress v1.19.2 h1:hMRETovs/pu/dVWN7zIT1PGG8t509MwT6bO7XSi26R8=
+github.com/klauspost/compress v1.19.2/go.mod h1:cwPg85FWrGar70rWktvGQj8/hthj3wpl0PGDogxkrSQ=
 github.com/klauspost/cpuid/v2 v2.0.1/go.mod h1:FInQzS24/EEf25PyTYn52gqo7WaD8xa0213Md/qVLRg=
 github.com/klauspost/cpuid/v2 v2.2.11 h1:0OwqZRYI2rFrjS4kvkDnqJkKHdHaRnCm68/DY4OxRzU=
 github.com/klauspost/cpuid/v2 v2.2.11/go.mod h1:hqwkgyIinND0mEev00jJYCxPNVRVXFQeu1XKlok6oO0=
@@ -189,6 +189,8 @@ github.com/tklauser/go-sysconf v0.3.16 h1:frioLaCQSsF5Cy1jgRBrzr6t502KIIwQ0MArYI
 github.com/tklauser/go-sysconf v0.3.16/go.mod h1:/qNL9xxDhc7tx3HSRsLWNnuzbVfh3e7gh/BmM179nYI=
 github.com/tklauser/numcpus v0.11.0 h1:nSTwhKH5e1dMNsCdVBukSZrURJRoHbSEQjdEbY+9RXw=
 github.com/tklauser/numcpus v0.11.0/go.mod h1:z+LwcLq54uWZTX0u/bGobaV34u6V7KNlTZejzM6/3MQ=
+github.com/ulikunitz/xz v0.5.16 h1:ld6NyySjx5lowVKwJvMRLnW5nxKX/xnpSiFYZ/Lxur0=
+github.com/ulikunitz/xz v0.5.16/go.mod h1:H9Rt/W6/Qj27PGauhQc6nfCDy7vHpzsOThBSaYDoEhw=
 github.com/xo/terminfo v0.0.0-20220910002029-abceb7e1c41e h1:JVG44RsyaB9T2KIHavMF/ppJZNG9ZpyihvCd0w101no=
 github.com/xo/terminfo v0.0.0-20220910002029-abceb7e1c41e/go.mod h1:RbqR21r5mrJuqunuUZ/Dhy/avygyECGrLceyNeo4LiM=
 github.com/yusufpapurcu/wmi v1.2.4 h1:zFUKzehAFReQwLys1b/iSMl+JQGSCSjtVqQn9bBrPo0=

internal/api/v2/remotes.go

@@ -12,18 +12,20 @@ import (
 )
 
 // Primer enqueues a background metadata prime for a newly created remote so the
-// create call never blocks on a derive. *rpm.Syncer satisfies it.
+// create call never blocks on a derive. *rpm.Syncer and *deb.Syncer satisfy it.
 type Primer interface {
 	EnqueuePrime(remote models.Remote)
 }
 
 type RemotesHandler struct {
-	db     *database.DB
-	primer Primer
+	db      *database.DB
+	primers map[models.PackageType]Primer
 }
 
-func NewRemotesHandler(db *database.DB, primer Primer) *RemotesHandler {
-	return &RemotesHandler{db: db, primer: primer}
+// NewRemotesHandler wires the handler to the per-type metadata primers. primers
+// may be nil; a package type with no registered primer simply skips priming.
+func NewRemotesHandler(db *database.DB, primers map[models.PackageType]Primer) *RemotesHandler {
+	return &RemotesHandler{db: db, primers: primers}
 }
 
 func (h *RemotesHandler) Routes() chi.Router {
@@ -84,10 +86,10 @@ func (h *RemotesHandler) create(w http.ResponseWriter, r *http.Request) {
 		http.Error(w, err.Error(), http.StatusInternalServerError)
 		return
 	}
-	// Prime a github_rpm remote's metadata in the background so its first
-	// repodata request is served from cache instead of a cold on-demand derive.
-	if h.primer != nil && remote.PackageType == models.PackageGitHubRPM {
-		h.primer.EnqueuePrime(remote)
+	// Prime a metadata-only remote (github_rpm/github_deb) in the background so
+	// its first index request is served from cache instead of a cold derive.
+	if primer := h.primers[remote.PackageType]; primer != nil {
+		primer.EnqueuePrime(remote)
 	}
 	writeJSON(w, http.StatusCreated, remote)
 }

internal/config/env.go

@@ -44,6 +44,18 @@ type Config struct {
 	GitHubSyncBurst        int
 	GitHubSyncWorkers      int
 	GitHubSyncPollInterval int
+
+	// Server-level GitHub machine credential, applied by default to every
+	// outbound GitHub request (releases scan, ranged asset fetches, and the
+	// generic-github byte proxy for private assets). Delivered via env/secret
+	// only — never stored per-remote, never returned by an API, never logged.
+	// Configure exactly one mode: a Personal Access Token, or a GitHub App
+	// (id + installation id + private key). Partial App config fails at startup.
+	GitHubToken             string
+	GitHubAppID             string
+	GitHubAppInstallationID string
+	GitHubAppPrivateKey     string
+	GitHubAppPrivateKeyPath string
 }
 
 func (c *Config) DatabaseDSN() string {
@@ -105,6 +117,12 @@ func Load() (*Config, error) {
 		GitHubSyncBurst:        syncBurst,
 		GitHubSyncWorkers:      syncWorkers,
 		GitHubSyncPollInterval: syncPoll,
+
+		GitHubToken:             getenv("GITHUB_TOKEN", ""),
+		GitHubAppID:             getenv("GITHUB_APP_ID", ""),
+		GitHubAppInstallationID: getenv("GITHUB_APP_INSTALLATION_ID", ""),
+		GitHubAppPrivateKey:     getenv("GITHUB_APP_PRIVATE_KEY", ""),
+		GitHubAppPrivateKeyPath: getenv("GITHUB_APP_PRIVATE_KEY_PATH", ""),
 	}
 
 	return cfg, nil

internal/database/deb_github_sync.go

@@ -0,0 +1,70 @@
+package database
+
+import (
+	"context"
+	"errors"
+	"time"
+
+	"github.com/jackc/pgx/v5"
+
+	"git.unkin.net/unkin/artifactapi/pkg/models"
+)
+
+// ListGitHubDebRemotes returns every github_deb remote so the syncer can sweep
+// them on each poll tick.
+func (db *DB) ListGitHubDebRemotes(ctx context.Context) ([]models.Remote, error) {
+	rows, err := db.Pool.Query(ctx, `SELECT `+remoteCols+` FROM remotes WHERE package_type = $1 ORDER BY name`, models.PackageGitHubDeb)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+
+	var remotes []models.Remote
+	for rows.Next() {
+		var r models.Remote
+		if err := scanRemote(rows, &r); err != nil {
+			return nil, err
+		}
+		remotes = append(remotes, r)
+	}
+	return remotes, rows.Err()
+}
+
+// ClaimGitHubDebSyncLease atomically claims the per-remote sync lease. It
+// succeeds only when the remote is due (never synced, or synced longer than
+// freshness ago) and no live lease is held by another replica. A zero freshness
+// (prime scans) ignores the recency gate. The returned etag is the stored
+// releases-list ETag, shared across replicas.
+func (db *DB) ClaimGitHubDebSyncLease(ctx context.Context, remoteName, owner string, freshness, lease time.Duration) (bool, string, error) {
+	row := db.Pool.QueryRow(ctx, `
+		INSERT INTO github_deb_sync_state AS s (remote_name, sync_lease_owner, sync_lease_expires)
+		VALUES ($1, $2, now() + make_interval(secs => $4))
+		ON CONFLICT (remote_name) DO UPDATE
+			SET sync_lease_owner   = $2,
+			    sync_lease_expires = now() + make_interval(secs => $4)
+			WHERE (s.last_synced_at IS NULL OR s.last_synced_at < now() - make_interval(secs => $3))
+			  AND (s.sync_lease_expires IS NULL OR s.sync_lease_expires < now())
+		RETURNING s.etag
+	`, remoteName, owner, freshness.Seconds(), lease.Seconds())
+
+	var etag string
+	if err := row.Scan(&etag); err != nil {
+		if errors.Is(err, pgx.ErrNoRows) {
+			return false, "", nil
+		}
+		return false, "", err
+	}
+	return true, etag, nil
+}
+
+// ReleaseGitHubDebSyncLease records the completed scan and frees the lease. Only
+// the owning replica may release; last_synced_at advances so the next poll waits
+// a full freshness window, and etag is persisted for the next conditional request.
+func (db *DB) ReleaseGitHubDebSyncLease(ctx context.Context, remoteName, owner, etag string, syncedAt time.Time) error {
+	_, err := db.Pool.Exec(ctx, `
+		UPDATE github_deb_sync_state
+		   SET last_synced_at = $3, etag = $4, sync_lease_owner = '', sync_lease_expires = NULL
+		 WHERE remote_name = $1 AND sync_lease_owner = $2
+	`, remoteName, owner, syncedAt, etag)
+	return err
+}

internal/database/deb_github_sync_test.go

@@ -0,0 +1,90 @@
+package database
+
+import (
+	"testing"
+	"time"
+
+	"git.unkin.net/unkin/artifactapi/pkg/models"
+)
+
+func seedGitHubDebRemote(t *testing.T, name string) {
+	t.Helper()
+	if err := testDB.CreateRemote(ctx(), &models.Remote{
+		Name: name, PackageType: models.PackageGitHubDeb, RepoType: models.RepoTypeRemote,
+		BaseURL: "https://api.github.com/repos/acme/tools", ReleasesRemote: "github", MutableTTL: 3600,
+	}); err != nil {
+		t.Fatalf("seed github_deb remote: %v", err)
+	}
+}
+
+// TestGitHubDebSyncLease exercises the real SQL: exactly one replica may hold the
+// lease, the recency window blocks a too-soon periodic re-claim, and a prime
+// (freshness 0) bypasses recency but still respects a live lease.
+func TestGitHubDebSyncLease(t *testing.T) {
+	requireDB(t)
+	name := "ghdeb-lease-" + time.Now().Format("150405.000000")
+	seedGitHubDebRemote(t, name)
+
+	const lease = 15 * time.Minute
+	freshness := time.Hour
+
+	claimed, etag, err := testDB.ClaimGitHubDebSyncLease(ctx(), name, "replica-1", freshness, lease)
+	if err != nil || !claimed {
+		t.Fatalf("replica-1 first claim: claimed=%v err=%v", claimed, err)
+	}
+	if etag != "" {
+		t.Fatalf("initial etag should be empty, got %q", etag)
+	}
+
+	claimed2, _, err := testDB.ClaimGitHubDebSyncLease(ctx(), name, "replica-2", freshness, lease)
+	if err != nil {
+		t.Fatalf("replica-2 claim err: %v", err)
+	}
+	if claimed2 {
+		t.Fatal("replica-2 claimed while replica-1 holds the lease")
+	}
+
+	if err := testDB.ReleaseGitHubDebSyncLease(ctx(), name, "replica-1", `"etag-1"`, time.Now()); err != nil {
+		t.Fatalf("release: %v", err)
+	}
+
+	claimed3, _, err := testDB.ClaimGitHubDebSyncLease(ctx(), name, "replica-2", freshness, lease)
+	if err != nil {
+		t.Fatalf("replica-2 recency claim err: %v", err)
+	}
+	if claimed3 {
+		t.Fatal("periodic claim succeeded inside the freshness window")
+	}
+
+	claimed4, etag4, err := testDB.ClaimGitHubDebSyncLease(ctx(), name, "replica-2", 0, lease)
+	if err != nil || !claimed4 {
+		t.Fatalf("prime claim: claimed=%v err=%v", claimed4, err)
+	}
+	if etag4 != `"etag-1"` {
+		t.Fatalf("prime claim etag = %q, want persisted \"etag-1\"", etag4)
+	}
+}
+
+func TestListGitHubDebRemotes(t *testing.T) {
+	requireDB(t)
+	name := "ghdeb-list-" + time.Now().Format("150405.000000")
+	seedGitHubDebRemote(t, name)
+	seedRemote(t, "generic-"+time.Now().Format("150405.000000"))
+
+	remotes, err := testDB.ListGitHubDebRemotes(ctx())
+	if err != nil {
+		t.Fatalf("list: %v", err)
+	}
+	found := false
+	for _, r := range remotes {
+		if r.PackageType != models.PackageGitHubDeb {
+			t.Fatalf("non-github_deb remote returned: %s (%s)", r.Name, r.PackageType)
+		}
+		if r.Name == name {
+			found = true
+		}
+	}
+	if !found {
+		t.Fatalf("seeded remote %q not returned", name)
+	}
+}

internal/database/deb_metadata.go

@@ -0,0 +1,57 @@
+package database
+
+import (
+	"context"
+
+	"git.unkin.net/unkin/artifactapi/internal/provider"
+)
+
+func (db *DB) InsertDebMetadata(ctx context.Context, meta *provider.DebMetadata) error {
+	_, err := db.Pool.Exec(ctx, `
+		INSERT INTO deb_metadata (
+			repo_name, file_path, content_hash,
+			name, version, architecture, control,
+			size, md5, sha256
+		) VALUES ($1,$2,$3,$4,$5,$6,$7,$8,$9,$10)
+		ON CONFLICT (repo_name, file_path) DO NOTHING
+	`,
+		meta.RepoName, meta.FilePath, meta.ContentHash,
+		meta.Name, meta.Version, meta.Architecture, meta.Control,
+		meta.Size, meta.MD5, meta.SHA256,
+	)
+	return err
+}
+
+func (db *DB) DeleteDebMetadata(ctx context.Context, repoName, filePath string) error {
+	_, err := db.Pool.Exec(ctx, `DELETE FROM deb_metadata WHERE repo_name = $1 AND file_path = $2`, repoName, filePath)
+	return err
+}
+
+func (db *DB) ListDebMetadataEntries(ctx context.Context, repoName string) ([]provider.DebMetadata, error) {
+	rows, err := db.Pool.Query(ctx, `
+		SELECT repo_name, file_path, content_hash,
+			name, version, architecture, control,
+			size, md5, sha256
+		FROM deb_metadata
+		WHERE repo_name = $1
+		ORDER BY name, version, architecture
+	`, repoName)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+
+	var result []provider.DebMetadata
+	for rows.Next() {
+		var m provider.DebMetadata
+		if err := rows.Scan(
+			&m.RepoName, &m.FilePath, &m.ContentHash,
+			&m.Name, &m.Version, &m.Architecture, &m.Control,
+			&m.Size, &m.MD5, &m.SHA256,
+		); err != nil {
+			return nil, err
+		}
+		result = append(result, m)
+	}
+	return result, rows.Err()
+}

internal/database/postgres.go

@@ -164,6 +164,24 @@ func (db *DB) migrate() error {
 		ALTER TABLE rpm_metadata ADD COLUMN IF NOT EXISTS conflicts JSONB DEFAULT '[]';
 		ALTER TABLE rpm_metadata ADD COLUMN IF NOT EXISTS obsoletes JSONB DEFAULT '[]';
 
+		CREATE TABLE IF NOT EXISTS deb_metadata (
+			id              BIGSERIAL PRIMARY KEY,
+			repo_name       TEXT NOT NULL,
+			file_path       TEXT NOT NULL,
+			content_hash    TEXT NOT NULL,
+			name            TEXT NOT NULL,
+			version         TEXT NOT NULL,
+			architecture    TEXT NOT NULL,
+			control         TEXT NOT NULL,
+			size            BIGINT DEFAULT 0,
+			md5             TEXT DEFAULT '',
+			sha256          TEXT DEFAULT '',
+			created_at      TIMESTAMPTZ DEFAULT NOW(),
+			UNIQUE(repo_name, file_path)
+		);
+
+		CREATE INDEX IF NOT EXISTS idx_deb_metadata_repo ON deb_metadata(repo_name);
+
 		CREATE TABLE IF NOT EXISTS github_rpm_sync_state (
 			remote_name        TEXT PRIMARY KEY,
 			etag               TEXT DEFAULT '',
@@ -172,6 +190,14 @@ func (db *DB) migrate() error {
 			sync_lease_expires TIMESTAMPTZ
 		);
 
+		CREATE TABLE IF NOT EXISTS github_deb_sync_state (
+			remote_name        TEXT PRIMARY KEY,
+			etag               TEXT DEFAULT '',
+			last_synced_at     TIMESTAMPTZ,
+			sync_lease_owner   TEXT DEFAULT '',
+			sync_lease_expires TIMESTAMPTZ
+		);
+
 		CREATE TABLE IF NOT EXISTS signing_keys (
 			purpose             TEXT PRIMARY KEY,
 			private_key_armor   TEXT NOT NULL,

internal/githubauth/app.go

@@ -0,0 +1,199 @@
+package githubauth
+
+import (
+	"context"
+	"crypto"
+	"crypto/rand"
+	"crypto/rsa"
+	"crypto/sha256"
+	"crypto/x509"
+	"encoding/base64"
+	"encoding/json"
+	"encoding/pem"
+	"errors"
+	"fmt"
+	"io"
+	"net/http"
+	"strings"
+	"sync"
+	"time"
+)
+
+const (
+	defaultAPIBase = "https://api.github.com"
+
+	// jwtLifetime is how long the app JWT is valid. GitHub caps it at 10 minutes;
+	// 9 leaves headroom for clock skew.
+	jwtLifetime = 9 * time.Minute
+	// jwtBackdate backdates iat to tolerate the app server's clock running behind
+	// GitHub's, which otherwise rejects the JWT.
+	jwtBackdate = 60 * time.Second
+	// refreshSkew refreshes the installation token this long before it expires so
+	// a request never races an expiry.
+	refreshSkew = 5 * time.Minute
+)
+
+type httpDoer interface {
+	Do(*http.Request) (*http.Response, error)
+}
+
+// appCredential mints installation access tokens for a GitHub App. It signs a
+// short-lived RS256 JWT with the app private key, exchanges it for a ~1h
+// installation token, caches that token, and refreshes it shortly before expiry.
+// Refreshes are single-flighted by holding the mutex across the exchange, so
+// concurrent callers coalesce onto one HTTP request and reuse the cached token.
+type appCredential struct {
+	appID          string
+	installationID string
+	key            *rsa.PrivateKey
+	apiBase        string
+	client         httpDoer
+
+	mu     sync.Mutex
+	token  string
+	expiry time.Time
+}
+
+func newAppCredential(opts Options) (*appCredential, error) {
+	if opts.AppID == "" {
+		return nil, errors.New("github app: GITHUB_APP_ID is required")
+	}
+	if opts.InstallationID == "" {
+		return nil, errors.New("github app: GITHUB_APP_INSTALLATION_ID is required")
+	}
+	pemBytes, err := loadPrivateKeyPEM(opts)
+	if err != nil {
+		return nil, err
+	}
+	key, err := parseRSAPrivateKey(pemBytes)
+	if err != nil {
+		return nil, err
+	}
+
+	apiBase := opts.apiBaseURL
+	if apiBase == "" {
+		apiBase = defaultAPIBase
+	}
+	client := opts.httpClient
+	if client == nil {
+		client = &http.Client{Timeout: 30 * time.Second}
+	}
+
+	return &appCredential{
+		appID:          opts.AppID,
+		installationID: opts.InstallationID,
+		key:            key,
+		apiBase:        strings.TrimRight(apiBase, "/"),
+		client:         client,
+	}, nil
+}
+
+// Token returns a cached installation token, refreshing it under a single-flight
+// lock when it is missing or within refreshSkew of expiry.
+func (a *appCredential) Token(ctx context.Context) (string, error) {
+	a.mu.Lock()
+	defer a.mu.Unlock()
+	if a.token != "" && time.Now().Before(a.expiry.Add(-refreshSkew)) {
+		return a.token, nil
+	}
+	if err := a.refreshLocked(ctx); err != nil {
+		return "", err
+	}
+	return a.token, nil
+}
+
+func (a *appCredential) refreshLocked(ctx context.Context) error {
+	jwt, err := mintJWT(a.appID, a.key, time.Now())
+	if err != nil {
+		return fmt.Errorf("github app: mint jwt: %w", err)
+	}
+
+	u := fmt.Sprintf("%s/app/installations/%s/access_tokens", a.apiBase, a.installationID)
+	req, err := http.NewRequestWithContext(ctx, http.MethodPost, u, nil)
+	if err != nil {
+		return err
+	}
+	req.Header.Set("Authorization", "Bearer "+jwt)
+	req.Header.Set("Accept", "application/vnd.github+json")
+	req.Header.Set("X-GitHub-Api-Version", "2022-11-28")
+
+	resp, err := a.client.Do(req)
+	if err != nil {
+		return fmt.Errorf("github app: token exchange: %w", err)
+	}
+	defer resp.Body.Close()
+	body, _ := io.ReadAll(io.LimitReader(resp.Body, 1<<20))
+	if resp.StatusCode != http.StatusCreated && resp.StatusCode != http.StatusOK {
+		// Never echo the body verbatim — it can contain sensitive material.
+		return fmt.Errorf("github app: token exchange status %d", resp.StatusCode)
+	}
+
+	var out struct {
+		Token     string    `json:"token"`
+		ExpiresAt time.Time `json:"expires_at"`
+	}
+	if err := json.Unmarshal(body, &out); err != nil {
+		return fmt.Errorf("github app: decode token response: %w", err)
+	}
+	if out.Token == "" {
+		return errors.New("github app: token exchange returned an empty token")
+	}
+	a.token = out.Token
+	a.expiry = out.ExpiresAt
+	if a.expiry.IsZero() {
+		// Defensive: assume the documented ~1h lifetime if GitHub omits it.
+		a.expiry = time.Now().Add(time.Hour)
+	}
+	return nil
+}
+
+// mintJWT builds and RS256-signs a GitHub App JWT (iss=app id, backdated iat,
+// ≤10m exp) using stdlib crypto — no third-party JWT dependency.
+func mintJWT(appID string, key *rsa.PrivateKey, now time.Time) (string, error) {
+	header := map[string]string{"alg": "RS256", "typ": "JWT"}
+	claims := map[string]any{
+		"iat": now.Add(-jwtBackdate).Unix(),
+		"exp": now.Add(jwtLifetime).Unix(),
+		"iss": appID,
+	}
+	hb, err := json.Marshal(header)
+	if err != nil {
+		return "", err
+	}
+	cb, err := json.Marshal(claims)
+	if err != nil {
+		return "", err
+	}
+	signingInput := b64url(hb) + "." + b64url(cb)
+	digest := sha256.Sum256([]byte(signingInput))
+	sig, err := rsa.SignPKCS1v15(rand.Reader, key, crypto.SHA256, digest[:])
+	if err != nil {
+		return "", err
+	}
+	return signingInput + "." + b64url(sig), nil
+}
+
+func b64url(b []byte) string {
+	return base64.RawURLEncoding.EncodeToString(b)
+}
+
+// parseRSAPrivateKey accepts PKCS#1 ("RSA PRIVATE KEY") and PKCS#8 ("PRIVATE
+// KEY") PEM, covering both GitHub App key export formats.
+func parseRSAPrivateKey(pemBytes []byte) (*rsa.PrivateKey, error) {
+	block, _ := pem.Decode(pemBytes)
+	if block == nil {
+		return nil, errors.New("github app: private key is not valid PEM")
+	}
+	if key, err := x509.ParsePKCS1PrivateKey(block.Bytes); err == nil {
+		return key, nil
+	}
+	keyAny, err := x509.ParsePKCS8PrivateKey(block.Bytes)
+	if err != nil {
+		return nil, errors.New("github app: private key is not a supported RSA PKCS#1/PKCS#8 key")
+	}
+	rsaKey, ok := keyAny.(*rsa.PrivateKey)
+	if !ok {
+		return nil, errors.New("github app: private key is not an RSA key")
+	}
+	return rsaKey, nil
+}

internal/githubauth/app_test.go

@@ -0,0 +1,207 @@
+package githubauth
+
+import (
+	"context"
+	"crypto"
+	"crypto/rand"
+	"crypto/rsa"
+	"crypto/sha256"
+	"crypto/x509"
+	"encoding/base64"
+	"encoding/json"
+	"encoding/pem"
+	"fmt"
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"sync"
+	"testing"
+	"time"
+)
+
+func testRSAKeyPEM(t *testing.T) string {
+	t.Helper()
+	key, err := rsa.GenerateKey(rand.Reader, 2048)
+	if err != nil {
+		t.Fatalf("generate key: %v", err)
+	}
+	der := x509.MarshalPKCS1PrivateKey(key)
+	return string(pem.EncodeToMemory(&pem.Block{Type: "RSA PRIVATE KEY", Bytes: der}))
+}
+
+// appFixture serves the installation-token exchange endpoint, records requests,
+// verifies the presented JWT against the app public key, and returns tokens with
+// a controllable expiry.
+type appFixture struct {
+	srv       *httptest.Server
+	pub       *rsa.PublicKey
+	mu        sync.Mutex
+	exchanges int
+	lastJWT   string
+	expiresAt func() time.Time
+	tokenSeq  int
+}
+
+func newAppFixture(t *testing.T, pemKey string) *appFixture {
+	t.Helper()
+	block, _ := pem.Decode([]byte(pemKey))
+	key, err := x509.ParsePKCS1PrivateKey(block.Bytes)
+	if err != nil {
+		t.Fatalf("parse test key: %v", err)
+	}
+	f := &appFixture{
+		pub:       &key.PublicKey,
+		expiresAt: func() time.Time { return time.Now().Add(time.Hour) },
+	}
+	mux := http.NewServeMux()
+	mux.HandleFunc("/app/installations/456/access_tokens", func(w http.ResponseWriter, r *http.Request) {
+		auth := r.Header.Get("Authorization")
+		jwt := strings.TrimPrefix(auth, "Bearer ")
+		f.mu.Lock()
+		f.exchanges++
+		f.lastJWT = jwt
+		f.tokenSeq++
+		seq := f.tokenSeq
+		exp := f.expiresAt()
+		f.mu.Unlock()
+		w.Header().Set("Content-Type", "application/json")
+		w.WriteHeader(http.StatusCreated)
+		json.NewEncoder(w).Encode(map[string]any{
+			"token":      fmt.Sprintf("ghs_installation_%d", seq),
+			"expires_at": exp.UTC().Format(time.RFC3339),
+		})
+	})
+	f.srv = httptest.NewServer(mux)
+	t.Cleanup(f.srv.Close)
+	return f
+}
+
+func (f *appFixture) verifyJWT(t *testing.T) {
+	t.Helper()
+	f.mu.Lock()
+	jwt := f.lastJWT
+	f.mu.Unlock()
+	parts := strings.Split(jwt, ".")
+	if len(parts) != 3 {
+		t.Fatalf("jwt not three-part: %q", jwt)
+	}
+	signingInput := parts[0] + "." + parts[1]
+	sig, err := base64.RawURLEncoding.DecodeString(parts[2])
+	if err != nil {
+		t.Fatalf("decode sig: %v", err)
+	}
+	digest := sha256.Sum256([]byte(signingInput))
+	if err := rsa.VerifyPKCS1v15(f.pub, crypto.SHA256, digest[:], sig); err != nil {
+		t.Fatalf("jwt signature invalid: %v", err)
+	}
+	var claims struct {
+		Iss string `json:"iss"`
+		Iat int64  `json:"iat"`
+		Exp int64  `json:"exp"`
+	}
+	cb, _ := base64.RawURLEncoding.DecodeString(parts[1])
+	if err := json.Unmarshal(cb, &claims); err != nil {
+		t.Fatalf("decode claims: %v", err)
+	}
+	if claims.Iss != "123" {
+		t.Fatalf("iss = %q, want 123", claims.Iss)
+	}
+	if claims.Exp-claims.Iat > int64((10*time.Minute)/time.Second) {
+		t.Fatalf("jwt lifetime exceeds 10m: iat=%d exp=%d", claims.Iat, claims.Exp)
+	}
+	if claims.Iat > time.Now().Unix() {
+		t.Fatalf("iat not backdated: %d", claims.Iat)
+	}
+}
+
+func newAppCred(t *testing.T, f *appFixture, pemKey string) *appCredential {
+	t.Helper()
+	c, err := newAppCredential(Options{
+		AppID:          "123",
+		InstallationID: "456",
+		PrivateKeyPEM:  pemKey,
+		apiBaseURL:     f.srv.URL,
+		httpClient:     f.srv.Client(),
+	})
+	if err != nil {
+		t.Fatalf("newAppCredential: %v", err)
+	}
+	return c
+}
+
+func TestApp_MintsJWTAndExchangesForInstallationToken(t *testing.T) {
+	pemKey := testRSAKeyPEM(t)
+	f := newAppFixture(t, pemKey)
+	c := newAppCred(t, f, pemKey)
+
+	tok, err := c.Token(context.Background())
+	if err != nil {
+		t.Fatalf("token: %v", err)
+	}
+	if tok != "ghs_installation_1" {
+		t.Fatalf("token = %q, want ghs_installation_1", tok)
+	}
+	if f.exchanges != 1 {
+		t.Fatalf("exchanges = %d, want 1", f.exchanges)
+	}
+	f.verifyJWT(t)
+}
+
+func TestApp_CachesInstallationToken(t *testing.T) {
+	pemKey := testRSAKeyPEM(t)
+	f := newAppFixture(t, pemKey)
+	c := newAppCred(t, f, pemKey)
+
+	for i := 0; i < 5; i++ {
+		if _, err := c.Token(context.Background()); err != nil {
+			t.Fatalf("token: %v", err)
+		}
+	}
+	if f.exchanges != 1 {
+		t.Fatalf("exchanges = %d, want 1 (token should be cached)", f.exchanges)
+	}
+}
+
+func TestApp_RefreshesNearExpiry(t *testing.T) {
+	pemKey := testRSAKeyPEM(t)
+	f := newAppFixture(t, pemKey)
+	// Token expires within refreshSkew, so every call must re-exchange.
+	f.expiresAt = func() time.Time { return time.Now().Add(2 * time.Minute) }
+	c := newAppCred(t, f, pemKey)
+
+	t1, err := c.Token(context.Background())
+	if err != nil {
+		t.Fatalf("token 1: %v", err)
+	}
+	t2, err := c.Token(context.Background())
+	if err != nil {
+		t.Fatalf("token 2: %v", err)
+	}
+	if f.exchanges != 2 {
+		t.Fatalf("exchanges = %d, want 2 (near-expiry token must refresh)", f.exchanges)
+	}
+	if t1 == t2 {
+		t.Fatalf("expected a fresh token after refresh, both = %q", t1)
+	}
+}
+
+func TestApp_ConcurrentTokenSingleFlights(t *testing.T) {
+	pemKey := testRSAKeyPEM(t)
+	f := newAppFixture(t, pemKey)
+	c := newAppCred(t, f, pemKey)
+
+	var wg sync.WaitGroup
+	for i := 0; i < 20; i++ {
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+			if _, err := c.Token(context.Background()); err != nil {
+				t.Errorf("token: %v", err)
+			}
+		}()
+	}
+	wg.Wait()
+	if f.exchanges != 1 {
+		t.Fatalf("exchanges = %d, want 1 (concurrent calls must coalesce)", f.exchanges)
+	}
+}

internal/githubauth/credential.go

@@ -0,0 +1,106 @@
+// Package githubauth provides the process-wide GitHub machine credential used to
+// authenticate every outbound GitHub request (releases scan, ranged asset header
+// fetches, and the generic-github byte proxy for private assets). The credential
+// is delivered via env/secret only — it is never stored per-remote in the DB,
+// never returned by any API, and never logged.
+package githubauth
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"os"
+	"strings"
+	"sync"
+)
+
+// Credential yields a bearer token for GitHub requests. Token may block to mint
+// or refresh (the GitHub App path); an empty string means "no auth", which only
+// happens when no credential is configured.
+type Credential interface {
+	Token(ctx context.Context) (string, error)
+}
+
+// Options is the raw, env-sourced auth configuration. Exactly one mode may be
+// configured: a static token, or a GitHub App (id + installation id + private
+// key). Partial App configuration is an error (fail closed); no fields at all is
+// fine and yields a nil credential (anonymous, current behavior).
+type Options struct {
+	// Token is a Personal Access Token (fine-grained or classic) sent verbatim
+	// as "Authorization: Bearer <token>".
+	Token string
+
+	// GitHub App fields. PrivateKeyPEM and PrivateKeyPath are alternatives; the
+	// inline PEM wins when both are set.
+	AppID          string
+	InstallationID string
+	PrivateKeyPEM  string
+	PrivateKeyPath string
+
+	// apiBaseURL overrides https://api.github.com for tests. Empty uses the real
+	// endpoint. httpClient likewise overrides the default client for tests.
+	apiBaseURL string
+	httpClient httpDoer
+}
+
+// New builds the process credential from options, validating that auth is either
+// fully configured or fully absent. It returns (nil, nil) when nothing is set.
+func New(opts Options) (Credential, error) {
+	hasToken := opts.Token != ""
+	hasAppField := opts.AppID != "" || opts.InstallationID != "" ||
+		opts.PrivateKeyPEM != "" || opts.PrivateKeyPath != ""
+
+	switch {
+	case !hasToken && !hasAppField:
+		return nil, nil // no auth configured — anonymous is fine
+	case hasToken && hasAppField:
+		return nil, errors.New("github auth: both a token and GitHub App fields are set; configure exactly one")
+	case hasToken:
+		return staticToken{token: opts.Token}, nil
+	default:
+		return newAppCredential(opts)
+	}
+}
+
+// staticToken is a fixed PAT credential.
+type staticToken struct{ token string }
+
+func (s staticToken) Token(context.Context) (string, error) { return s.token, nil }
+
+// server is the process-wide credential set once at startup. A nil value means
+// no server credential (anonymous). Access is guarded so a late SetServer in a
+// test is race-free.
+var (
+	serverMu sync.RWMutex
+	server   Credential
+)
+
+// SetServer installs the process credential. Call once during startup.
+func SetServer(c Credential) {
+	serverMu.Lock()
+	server = c
+	serverMu.Unlock()
+}
+
+// Server returns the process credential, or nil if none is configured.
+func Server() Credential {
+	serverMu.RLock()
+	defer serverMu.RUnlock()
+	return server
+}
+
+// loadPrivateKeyPEM resolves the App private key bytes from the inline PEM or a
+// file path, without ever returning the key material in an error message.
+func loadPrivateKeyPEM(opts Options) ([]byte, error) {
+	if strings.TrimSpace(opts.PrivateKeyPEM) != "" {
+		return []byte(opts.PrivateKeyPEM), nil
+	}
+	if opts.PrivateKeyPath != "" {
+		b, err := os.ReadFile(opts.PrivateKeyPath)
+		if err != nil {
+			return nil, fmt.Errorf("github app: read private key file: %w", err)
+		}
+		return b, nil
+	}
+	return nil, errors.New("github app: no private key configured")
+}

internal/githubauth/credential_test.go

@@ -0,0 +1,77 @@
+package githubauth
+
+import (
+	"context"
+	"testing"
+)
+
+func TestNew_NoConfigIsAnonymous(t *testing.T) {
+	c, err := New(Options{})
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if c != nil {
+		t.Fatalf("expected nil credential when nothing configured, got %T", c)
+	}
+}
+
+func TestNew_TokenMode(t *testing.T) {
+	c, err := New(Options{Token: "ghp_example"})
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	tok, err := c.Token(context.Background())
+	if err != nil {
+		t.Fatalf("token: %v", err)
+	}
+	if tok != "ghp_example" {
+		t.Fatalf("token = %q, want ghp_example", tok)
+	}
+}
+
+func TestNew_TokenAndAppConflict(t *testing.T) {
+	_, err := New(Options{Token: "ghp_example", AppID: "123"})
+	if err == nil {
+		t.Fatal("expected error when both token and app fields are set")
+	}
+}
+
+func TestNew_PartialAppFailsClosed(t *testing.T) {
+	cases := map[string]Options{
+		"app id without key":  {AppID: "123", InstallationID: "456"},
+		"key without app id":  {InstallationID: "456", PrivateKeyPEM: testRSAKeyPEM(t)},
+		"app id without inst": {AppID: "123", PrivateKeyPEM: testRSAKeyPEM(t)},
+	}
+	for name, opts := range cases {
+		t.Run(name, func(t *testing.T) {
+			if _, err := New(opts); err == nil {
+				t.Fatalf("expected fail-closed error for %q", name)
+			}
+		})
+	}
+}
+
+func TestNew_AppModeParsesKey(t *testing.T) {
+	c, err := New(Options{
+		AppID:          "123",
+		InstallationID: "456",
+		PrivateKeyPEM:  testRSAKeyPEM(t),
+	})
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if _, ok := c.(*appCredential); !ok {
+		t.Fatalf("expected *appCredential, got %T", c)
+	}
+}
+
+func TestNew_AppModeRejectsBadKey(t *testing.T) {
+	_, err := New(Options{
+		AppID:          "123",
+		InstallationID: "456",
+		PrivateKeyPEM:  "-----BEGIN RSA PRIVATE KEY-----\nnope\n-----END RSA PRIVATE KEY-----",
+	})
+	if err == nil {
+		t.Fatal("expected error for malformed private key")
+	}
+}

internal/provider/deb/deb.go

@@ -0,0 +1,447 @@
+package deb
+
+import (
+	"archive/tar"
+	"bufio"
+	"bytes"
+	"compress/gzip"
+	"context"
+	"crypto/md5"
+	"crypto/sha256"
+	"encoding/hex"
+	"errors"
+	"fmt"
+	"io"
+	"log/slog"
+	"net/http"
+	"path"
+	"regexp"
+	"strconv"
+	"strings"
+	"time"
+
+	"github.com/klauspost/compress/zstd"
+	"github.com/ulikunitz/xz"
+
+	"git.unkin.net/unkin/artifactapi/internal/auth"
+	"git.unkin.net/unkin/artifactapi/internal/provider"
+	"git.unkin.net/unkin/artifactapi/internal/storage"
+	"git.unkin.net/unkin/artifactapi/pkg/models"
+)
+
+func init() {
+	provider.Register(&Provider{})
+}
+
+// mutableRe marks the apt index surface (both the flat local repo and a proxied
+// Debian/Ubuntu mirror's dists/ tree) so the caching engine revalidates it
+// instead of freezing it like an immutable .deb.
+var mutableRe = []*regexp.Regexp{
+	regexp.MustCompile(`(^|/)Packages(\.gz|\.xz|\.bz2)?$`),
+	regexp.MustCompile(`(^|/)Sources(\.gz|\.xz|\.bz2)?$`),
+	regexp.MustCompile(`(^|/)Release$`),
+	regexp.MustCompile(`(^|/)InRelease$`),
+	regexp.MustCompile(`(^|/)Release\.gpg$`),
+	regexp.MustCompile(`(^|/)Contents-`),
+	regexp.MustCompile(`^dists/`),
+	regexp.MustCompile(`/by-hash/`),
+}
+
+type Provider struct{}
+
+func (p *Provider) Type() models.PackageType { return models.PackageDeb }
+
+func (p *Provider) Classify(path string) provider.Mutability {
+	for _, re := range mutableRe {
+		if re.MatchString(path) {
+			return provider.Mutable
+		}
+	}
+	return provider.Immutable
+}
+
+func (p *Provider) ContentType(path string) string {
+	switch {
+	case strings.HasSuffix(path, ".deb"):
+		return "application/vnd.debian.binary-package"
+	case strings.HasSuffix(path, ".gz"):
+		return "application/gzip"
+	case strings.HasSuffix(path, ".xz"):
+		return "application/x-xz"
+	case strings.HasSuffix(path, "Packages"), strings.HasSuffix(path, "Release"),
+		strings.HasSuffix(path, "InRelease"), strings.HasSuffix(path, "Sources"):
+		return "text/plain"
+	}
+	return "application/octet-stream"
+}
+
+func (p *Provider) UpstreamURL(remote models.Remote, path string) string {
+	return strings.TrimRight(remote.BaseURL, "/") + "/" + strings.TrimLeft(path, "/")
+}
+
+func (p *Provider) RewriteResponse(_ []byte, _ models.Remote, _ string) ([]byte, error) {
+	return nil, nil
+}
+
+func (p *Provider) AuthHeaders(_ context.Context, remote models.Remote) (http.Header, error) {
+	return auth.BasicHeaders(remote), nil
+}
+
+func (p *Provider) ValidateUpload(filePath string) (storagePath, contentType string, err error) {
+	filename := filePath
+	if idx := strings.LastIndex(filePath, "/"); idx >= 0 {
+		filename = filePath[idx+1:]
+	}
+
+	if !strings.HasSuffix(strings.ToLower(filename), ".deb") {
+		return "", "", fmt.Errorf("file must be a .deb package")
+	}
+
+	return "pool/" + filename, "application/vnd.debian.binary-package", nil
+}
+
+func (p *Provider) UploadResponse(storagePath, contentHash string, sizeBytes int64) map[string]any {
+	filename := strings.TrimPrefix(storagePath, "pool/")
+	return map[string]any{
+		"filename":     filename,
+		"content_hash": contentHash,
+		"size_bytes":   sizeBytes,
+	}
+}
+
+func (p *Provider) AfterUpload(ctx context.Context, repoName, storagePath, contentHash string, blobs provider.BlobReader, db provider.MetadataStore) {
+	s3Key := storage.BlobKey(strings.TrimPrefix(contentHash, "sha256:"))
+
+	reader, blobSize, err := blobs.Download(ctx, s3Key)
+	if err != nil {
+		slog.Error("deb metadata: download failed", "repo", repoName, "path", storagePath, "error", err)
+		return
+	}
+	defer reader.Close()
+
+	raw, err := io.ReadAll(reader)
+	if err != nil {
+		slog.Error("deb metadata: read failed", "repo", repoName, "path", storagePath, "error", err)
+		return
+	}
+
+	control, err := extractControl(raw)
+	if err != nil {
+		slog.Error("deb metadata: parse failed", "repo", repoName, "path", storagePath, "error", err)
+		return
+	}
+	fields := parseControlFields(control)
+
+	sum := md5.Sum(raw)
+	meta := &provider.DebMetadata{
+		RepoName:     repoName,
+		FilePath:     storagePath,
+		ContentHash:  contentHash,
+		Name:         fields["Package"],
+		Version:      fields["Version"],
+		Architecture: fields["Architecture"],
+		Control:      strings.TrimRight(control, "\n"),
+		Size:         blobSize,
+		MD5:          hex.EncodeToString(sum[:]),
+		SHA256:       strings.TrimPrefix(contentHash, "sha256:"),
+	}
+
+	if meta.Name == "" {
+		slog.Error("deb metadata: control missing Package field", "repo", repoName, "path", storagePath)
+		return
+	}
+
+	if err := db.InsertDebMetadata(ctx, meta); err != nil {
+		slog.Error("deb metadata: insert failed", "repo", repoName, "path", storagePath, "error", err)
+		return
+	}
+
+	slog.Info("deb metadata: parsed", "repo", repoName, "name", meta.Name, "version", meta.Version, "arch", meta.Architecture)
+}
+
+func (p *Provider) AfterDelete(ctx context.Context, repoName, storagePath string, db provider.MetadataDeleter) error {
+	if err := db.DeleteDebMetadata(ctx, repoName, storagePath); err != nil {
+		slog.Error("deb metadata: delete failed", "repo", repoName, "path", storagePath, "error", err)
+		return err
+	}
+	slog.Info("deb metadata: deleted", "repo", repoName, "path", storagePath)
+	return nil
+}
+
+// extractControl reads a .deb (an ar archive), locates the control.tar.* member,
+// decompresses it, and returns the raw ./control paragraph. Pure Go: no dpkg.
+func extractControl(deb []byte) (string, error) {
+	members, err := readAr(deb)
+	if err != nil {
+		return "", err
+	}
+
+	var name string
+	var data []byte
+	for _, m := range members {
+		if strings.HasPrefix(m.name, "control.tar") {
+			name = m.name
+			data = m.data
+			break
+		}
+	}
+	if data == nil {
+		return "", errors.New("no control.tar member in .deb")
+	}
+
+	tarBytes, err := decompress(name, data)
+	if err != nil {
+		return "", err
+	}
+
+	return readControlParagraph(tarBytes)
+}
+
+// readControlParagraph scans a decompressed control.tar and returns the raw
+// ./control paragraph. Shared by the local upload path (extractControl) and the
+// github_deb ranged-prefix parser.
+func readControlParagraph(controlTar []byte) (string, error) {
+	tr := tar.NewReader(bytes.NewReader(controlTar))
+	for {
+		hdr, err := tr.Next()
+		if err == io.EOF {
+			break
+		}
+		if err != nil {
+			return "", fmt.Errorf("read control.tar: %w", err)
+		}
+		clean := strings.TrimPrefix(hdr.Name, "./")
+		if clean == "control" {
+			b, err := io.ReadAll(tr)
+			if err != nil {
+				return "", fmt.Errorf("read control file: %w", err)
+			}
+			return string(b), nil
+		}
+	}
+	return "", errors.New("no ./control in control.tar")
+}
+
+func decompress(name string, data []byte) ([]byte, error) {
+	switch {
+	case strings.HasSuffix(name, ".gz"):
+		zr, err := gzip.NewReader(bytes.NewReader(data))
+		if err != nil {
+			return nil, err
+		}
+		defer zr.Close()
+		return io.ReadAll(zr)
+	case strings.HasSuffix(name, ".xz"):
+		xr, err := xz.NewReader(bytes.NewReader(data))
+		if err != nil {
+			return nil, err
+		}
+		return io.ReadAll(xr)
+	case strings.HasSuffix(name, ".zst"):
+		zr, err := zstd.NewReader(bytes.NewReader(data))
+		if err != nil {
+			return nil, err
+		}
+		defer zr.Close()
+		return io.ReadAll(zr)
+	case strings.HasSuffix(name, ".tar"):
+		return data, nil
+	}
+	return nil, fmt.Errorf("unsupported control.tar compression: %s", name)
+}
+
+type arMember struct {
+	name string
+	data []byte
+}
+
+// readAr parses the (trivial) Unix ar archive that wraps a .deb. Each member has
+// a 60-byte header; the size field is decimal ASCII and data is padded to an
+// even offset.
+func readAr(data []byte) ([]arMember, error) {
+	const magic = "!<arch>\n"
+	if len(data) < len(magic) || string(data[:len(magic)]) != magic {
+		return nil, errors.New("not an ar archive")
+	}
+	off := len(magic)
+
+	var members []arMember
+	for off+60 <= len(data) {
+		hdr := data[off : off+60]
+		off += 60
+
+		name := strings.TrimRight(string(hdr[0:16]), " ")
+		name = strings.TrimSuffix(name, "/")
+		size, err := strconv.ParseInt(strings.TrimSpace(string(hdr[48:58])), 10, 64)
+		if err != nil {
+			return nil, fmt.Errorf("bad ar size for %q: %w", name, err)
+		}
+		if off+int(size) > len(data) {
+			return nil, fmt.Errorf("truncated ar member %q", name)
+		}
+		members = append(members, arMember{name: name, data: data[off : off+int(size)]})
+		off += int(size)
+		if size%2 == 1 {
+			off++
+		}
+	}
+	return members, nil
+}
+
+// parseControlFields reads the single-line fields of an RFC822-style control
+// paragraph. Continuation lines (leading whitespace) belong to the previous
+// field and are ignored here since only Package/Version/Architecture are read.
+func parseControlFields(control string) map[string]string {
+	fields := map[string]string{}
+	sc := bufio.NewScanner(strings.NewReader(control))
+	sc.Buffer(make([]byte, 0, 64*1024), 1024*1024)
+	for sc.Scan() {
+		line := sc.Text()
+		if line == "" || line[0] == ' ' || line[0] == '\t' {
+			continue
+		}
+		idx := strings.IndexByte(line, ':')
+		if idx < 0 {
+			continue
+		}
+		key := strings.TrimSpace(line[:idx])
+		if _, seen := fields[key]; seen {
+			continue
+		}
+		fields[key] = strings.TrimSpace(line[idx+1:])
+	}
+	return fields
+}
+
+// normalizeIndexPath collapses apt's verbatim dist prefix from a flat-repo
+// request. For `deb ... <repo>/ ./`, apt appends the "./" dist literally and asks
+// for "./Packages" (and "./Release", "./InRelease"); dot-segments must be
+// collapsed so the index matcher sees "Packages". A no-op for pool/*.deb paths.
+func normalizeIndexPath(p string) string {
+	return strings.TrimPrefix(path.Clean("/"+p), "/")
+}
+
+func (p *Provider) ServeLocalIndex(w http.ResponseWriter, r *http.Request, files provider.FileStore, repoName, reqPath string) bool {
+	path := normalizeIndexPath(reqPath)
+	switch path {
+	case "Packages", "Packages.gz", "Release":
+	default:
+		return false
+	}
+
+	reader, ok := files.(provider.DebMetadataReader)
+	if !ok {
+		http.Error(w, "deb metadata not available", http.StatusInternalServerError)
+		return true
+	}
+
+	metas, err := reader.ListDebMetadataEntries(r.Context(), repoName)
+	if err != nil {
+		if errors.Is(err, context.Canceled) || errors.Is(err, context.DeadlineExceeded) {
+			slog.Warn("deb: metadata read canceled", "repo", repoName, "error", err)
+			http.Error(w, "metadata read canceled", http.StatusServiceUnavailable)
+			return true
+		}
+		http.Error(w, err.Error(), http.StatusInternalServerError)
+		return true
+	}
+
+	switch path {
+	case "Packages":
+		w.Header().Set("Content-Type", "text/plain")
+		w.WriteHeader(http.StatusOK)
+		w.Write(generatePackages(metas))
+	case "Packages.gz":
+		w.Header().Set("Content-Type", "application/gzip")
+		w.WriteHeader(http.StatusOK)
+		w.Write(gzipBytes(generatePackages(metas)))
+	case "Release":
+		w.Header().Set("Content-Type", "text/plain")
+		w.WriteHeader(http.StatusOK)
+		w.Write(generateRelease(metas))
+	}
+	return true
+}
+
+func (p *Provider) GenerateLocalIndex(ctx context.Context, files provider.FileStore, repoName, path string) ([]byte, error) {
+	return nil, fmt.Errorf("deb local index generation for virtual repos not supported")
+}
+
+// generatePackages emits the flat-repo Packages file: each package's raw control
+// stanza followed by the apt-required Filename/Size/MD5sum/SHA256 fields, blank
+// line separated.
+func generatePackages(metas []provider.DebMetadata) []byte {
+	var b bytes.Buffer
+	for _, m := range metas {
+		b.WriteString(strings.TrimRight(m.Control, "\n"))
+		b.WriteString("\n")
+		fmt.Fprintf(&b, "Filename: %s\n", m.FilePath)
+		fmt.Fprintf(&b, "Size: %d\n", m.Size)
+		if m.MD5 != "" {
+			fmt.Fprintf(&b, "MD5sum: %s\n", m.MD5)
+		}
+		if m.SHA256 != "" {
+			fmt.Fprintf(&b, "SHA256: %s\n", m.SHA256)
+		}
+		b.WriteString("\n")
+	}
+	return b.Bytes()
+}
+
+func generateRelease(metas []provider.DebMetadata) []byte {
+	packages := generatePackages(metas)
+	packagesGz := gzipBytes(packages)
+
+	arches := uniqueArches(metas)
+
+	var b bytes.Buffer
+	fmt.Fprintf(&b, "Date: %s\n", time.Now().UTC().Format(time.RFC1123Z))
+	fmt.Fprintf(&b, "Architectures: %s\n", strings.Join(arches, " "))
+	b.WriteString("Acquire-By-Hash: no\n")
+
+	b.WriteString("MD5Sum:\n")
+	writeReleaseEntry(&b, md5Hex(packages), len(packages), "Packages")
+	writeReleaseEntry(&b, md5Hex(packagesGz), len(packagesGz), "Packages.gz")
+
+	b.WriteString("SHA256:\n")
+	writeReleaseEntry(&b, sha256Hex(packages), len(packages), "Packages")
+	writeReleaseEntry(&b, sha256Hex(packagesGz), len(packagesGz), "Packages.gz")
+
+	return b.Bytes()
+}
+
+func writeReleaseEntry(b *bytes.Buffer, hash string, size int, name string) {
+	fmt.Fprintf(b, " %s %d %s\n", hash, size, name)
+}
+
+func uniqueArches(metas []provider.DebMetadata) []string {
+	seen := map[string]bool{}
+	var out []string
+	for _, m := range metas {
+		a := m.Architecture
+		if a == "" || seen[a] {
+			continue
+		}
+		seen[a] = true
+		out = append(out, a)
+	}
+	return out
+}
+
+func gzipBytes(data []byte) []byte {
+	var buf bytes.Buffer
+	gz := gzip.NewWriter(&buf)
+	gz.Write(data)
+	gz.Close()
+	return buf.Bytes()
+}
+
+func md5Hex(data []byte) string {
+	h := md5.Sum(data)
+	return hex.EncodeToString(h[:])
+}
+
+func sha256Hex(data []byte) string {
+	h := sha256.Sum256(data)
+	return hex.EncodeToString(h[:])
+}

internal/provider/deb/deb_test.go

@@ -0,0 +1,408 @@
+package deb
+
+import (
+	"archive/tar"
+	"bytes"
+	"compress/gzip"
+	"context"
+	"fmt"
+	"io"
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"testing"
+
+	"github.com/klauspost/compress/zstd"
+	"github.com/ulikunitz/xz"
+
+	"git.unkin.net/unkin/artifactapi/internal/provider"
+	"git.unkin.net/unkin/artifactapi/internal/testsupport"
+	"git.unkin.net/unkin/artifactapi/pkg/models"
+)
+
+type fakeBlobReader struct{ data []byte }
+
+func (f fakeBlobReader) Download(_ context.Context, _ string) (io.ReadCloser, int64, error) {
+	return io.NopCloser(bytes.NewReader(f.data)), int64(len(f.data)), nil
+}
+
+type errBlobReader struct{}
+
+func (errBlobReader) Download(_ context.Context, _ string) (io.ReadCloser, int64, error) {
+	return nil, 0, io.ErrUnexpectedEOF
+}
+
+// fakeDebStore satisfies provider.MetadataStore (both insert methods) and
+// records the deb row that AfterUpload writes.
+type fakeDebStore struct{ inserted *provider.DebMetadata }
+
+func (f *fakeDebStore) InsertRPMMetadata(context.Context, *provider.RPMMetadata) error { return nil }
+func (f *fakeDebStore) InsertDebMetadata(_ context.Context, m *provider.DebMetadata) error {
+	f.inserted = m
+	return nil
+}
+
+type fakeDebReader struct{ metas []provider.DebMetadata }
+
+func (f fakeDebReader) ListDebMetadataEntries(context.Context, string) ([]provider.DebMetadata, error) {
+	return f.metas, nil
+}
+func (f fakeDebReader) ListFilesByPrefix(context.Context, string, string) ([]provider.FileEntry, error) {
+	return nil, nil
+}
+func (f fakeDebReader) ListPackages(context.Context, string) ([]string, error) { return nil, nil }
+
+type errDebReader struct{}
+
+func (errDebReader) ListDebMetadataEntries(context.Context, string) ([]provider.DebMetadata, error) {
+	return nil, io.ErrUnexpectedEOF
+}
+func (errDebReader) ListFilesByPrefix(context.Context, string, string) ([]provider.FileEntry, error) {
+	return nil, nil
+}
+func (errDebReader) ListPackages(context.Context, string) ([]string, error) { return nil, nil }
+
+func TestDebPureFuncs(t *testing.T) {
+	p := &Provider{}
+	if p.Type() != models.PackageDeb {
+		t.Errorf("type = %q", p.Type())
+	}
+	if out, _ := p.RewriteResponse(nil, models.Remote{}, "http://p"); out != nil {
+		t.Error("deb never rewrites")
+	}
+	if got := p.UpstreamURL(models.Remote{BaseURL: "https://mirror/"}, "/dists/bookworm/Release"); got != "https://mirror/dists/bookworm/Release" {
+		t.Errorf("upstream url %q", got)
+	}
+	h, _ := p.AuthHeaders(context.Background(), models.Remote{Username: "u", Password: "p"})
+	if h.Get("Authorization") == "" {
+		t.Error("auth header")
+	}
+}
+
+func TestDebClassify(t *testing.T) {
+	p := &Provider{}
+	tests := []struct {
+		path string
+		want provider.Mutability
+	}{
+		{"pool/foo_1.0_amd64.deb", provider.Immutable},
+		{"Packages", provider.Mutable},
+		{"Packages.gz", provider.Mutable},
+		{"Release", provider.Mutable},
+		{"InRelease", provider.Mutable},
+		{"Release.gpg", provider.Mutable},
+		{"dists/bookworm/main/binary-amd64/Packages", provider.Mutable},
+		{"dists/bookworm/Release", provider.Mutable},
+		{"dists/bookworm/main/by-hash/SHA256/abc", provider.Mutable},
+		{"dists/bookworm/main/Contents-amd64.gz", provider.Mutable},
+	}
+	for _, tt := range tests {
+		if got := p.Classify(tt.path); got != tt.want {
+			t.Errorf("Classify(%q) = %v, want %v", tt.path, got, tt.want)
+		}
+	}
+}
+
+func TestDebContentType(t *testing.T) {
+	p := &Provider{}
+	for path, want := range map[string]string{
+		"pool/foo_1.0_amd64.deb":              "application/vnd.debian.binary-package",
+		"dists/bookworm/main/bin/Packages.gz": "application/gzip",
+		"dists/bookworm/main/bin/Packages.xz": "application/x-xz",
+		"Packages":                            "text/plain",
+		"Release":                             "text/plain",
+		"InRelease":                           "text/plain",
+		"pool/other":                          "application/octet-stream",
+	} {
+		if got := p.ContentType(path); got != want {
+			t.Errorf("ContentType(%q) = %q, want %q", path, got, want)
+		}
+	}
+}
+
+func TestDebValidateUpload(t *testing.T) {
+	p := &Provider{}
+	sp, ct, err := p.ValidateUpload("dir/foo_1.0_amd64.deb")
+	if err != nil || sp != "pool/foo_1.0_amd64.deb" || ct != "application/vnd.debian.binary-package" {
+		t.Errorf("sp=%q ct=%q err=%v", sp, ct, err)
+	}
+	if _, _, err := p.ValidateUpload("foo.rpm"); err == nil {
+		t.Error("expected error for non-deb")
+	}
+	resp := p.UploadResponse("pool/foo_1.0_amd64.deb", "sha256:abc", 42)
+	if resp["filename"] != "foo_1.0_amd64.deb" || resp["content_hash"] != "sha256:abc" || resp["size_bytes"] != int64(42) {
+		t.Errorf("upload response %v", resp)
+	}
+}
+
+func TestDebAfterUpload(t *testing.T) {
+	data := testsupport.MinimalDeb("e2e-testpkg", "1.2.3", "amd64")
+	store := &fakeDebStore{}
+	(&Provider{}).AfterUpload(context.Background(), "myrepo", "pool/e2e-testpkg_1.2.3_amd64.deb",
+		"sha256:deadbeef", fakeBlobReader{data: data}, store)
+
+	m := store.inserted
+	if m == nil {
+		t.Fatal("no metadata inserted")
+	}
+	if m.Name != "e2e-testpkg" || m.Version != "1.2.3" || m.Architecture != "amd64" {
+		t.Errorf("unexpected metadata: %+v", m)
+	}
+	if m.Size != int64(len(data)) {
+		t.Errorf("Size = %d, want %d", m.Size, len(data))
+	}
+	if m.SHA256 != "deadbeef" {
+		t.Errorf("SHA256 = %q, want deadbeef", m.SHA256)
+	}
+	if m.MD5 == "" {
+		t.Error("MD5 not computed")
+	}
+	if !strings.Contains(m.Control, "Package: e2e-testpkg") {
+		t.Errorf("raw control not stored: %q", m.Control)
+	}
+	// The raw stanza is stored verbatim (no trailing newline) so Packages can
+	// reproduce it faithfully.
+	if strings.HasSuffix(m.Control, "\n") {
+		t.Error("control should be trimmed of trailing newline")
+	}
+}
+
+func TestDebAfterUploadErrors(t *testing.T) {
+	// Download failure: no insert, no panic.
+	store := &fakeDebStore{}
+	(&Provider{}).AfterUpload(context.Background(), "r", "p", "sha256:x", errBlobReader{}, store)
+	if store.inserted != nil {
+		t.Error("no metadata should be inserted on download error")
+	}
+	// Not a .deb (ar) archive.
+	store2 := &fakeDebStore{}
+	(&Provider{}).AfterUpload(context.Background(), "r", "p", "sha256:x", fakeBlobReader{data: []byte("not a deb")}, store2)
+	if store2.inserted != nil {
+		t.Error("no metadata should be inserted on parse error")
+	}
+}
+
+func TestDebControlDecompression(t *testing.T) {
+	// The control tarball may be gzip, xz, or zstd (goreleaser/nfpm emit gzip or
+	// xz); each must round-trip to the same control stanza.
+	for _, tc := range []struct {
+		name   string
+		member string
+		comp   func([]byte) []byte
+	}{
+		{"gzip", "control.tar.gz", gzipBytes},
+		{"xz", "control.tar.xz", xzBytes},
+		{"zstd", "control.tar.zst", zstdBytes},
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			deb := buildDeb("pkg", "9.9", "arm64", tc.member, tc.comp)
+			control, err := extractControl(deb)
+			if err != nil {
+				t.Fatalf("extractControl: %v", err)
+			}
+			fields := parseControlFields(control)
+			if fields["Package"] != "pkg" || fields["Version"] != "9.9" || fields["Architecture"] != "arm64" {
+				t.Errorf("fields = %v", fields)
+			}
+		})
+	}
+}
+
+func TestDebParseControlContinuationLines(t *testing.T) {
+	control := "Package: p\nVersion: 1\n" +
+		"Description: short\n very long\n .\n more\n" +
+		"Architecture: all\n"
+	f := parseControlFields(control)
+	if f["Package"] != "p" || f["Version"] != "1" || f["Architecture"] != "all" {
+		t.Errorf("continuation lines corrupted parse: %v", f)
+	}
+	if f["Description"] != "short" {
+		t.Errorf("Description folded continuation into value: %q", f["Description"])
+	}
+}
+
+func TestDebServeLocalIndex(t *testing.T) {
+	p := &Provider{}
+	reader := fakeDebReader{metas: []provider.DebMetadata{
+		{Name: "aaa", Version: "1.0", Architecture: "amd64", FilePath: "pool/aaa_1.0_amd64.deb",
+			Control: "Package: aaa\nVersion: 1.0\nArchitecture: amd64", Size: 100, MD5: "md5aaa", SHA256: "sha256aaa"},
+		{Name: "bbb", Version: "2.0", Architecture: "arm64", FilePath: "pool/bbb_2.0_arm64.deb",
+			Control: "Package: bbb\nVersion: 2.0\nArchitecture: arm64", Size: 200, MD5: "md5bbb", SHA256: "sha256bbb"},
+	}}
+
+	serve := func(path string) *httptest.ResponseRecorder {
+		w := httptest.NewRecorder()
+		r := httptest.NewRequest(http.MethodGet, "/"+path, nil)
+		if !p.ServeLocalIndex(w, r, reader, "myrepo", path) {
+			t.Fatalf("ServeLocalIndex returned false for %q", path)
+		}
+		return w
+	}
+
+	// Packages lists both packages with their apt fields.
+	w := serve("Packages")
+	body := w.Body.String()
+	if w.Code != 200 {
+		t.Fatalf("Packages code %d", w.Code)
+	}
+	for _, want := range []string{
+		"Package: aaa", "Package: bbb",
+		"Filename: pool/aaa_1.0_amd64.deb", "Size: 100", "MD5sum: md5aaa", "SHA256: sha256aaa",
+		"Filename: pool/bbb_2.0_arm64.deb", "Size: 200",
+	} {
+		if !strings.Contains(body, want) {
+			t.Errorf("Packages missing %q:\n%s", want, body)
+		}
+	}
+	// Stanzas are blank-line separated.
+	if !strings.Contains(body, "SHA256: sha256aaa\n\n") {
+		t.Errorf("stanzas not blank-line separated:\n%s", body)
+	}
+
+	// Packages.gz decompresses to exactly the plain Packages bytes.
+	w = serve("Packages.gz")
+	if w.Code != 200 {
+		t.Fatalf("Packages.gz code %d", w.Code)
+	}
+	zr, err := gzip.NewReader(bytes.NewReader(w.Body.Bytes()))
+	if err != nil {
+		t.Fatalf("Packages.gz not gzip: %v", err)
+	}
+	plain, _ := io.ReadAll(zr)
+	if !bytes.Equal(plain, []byte(body)) {
+		t.Error("Packages.gz does not decompress to Packages")
+	}
+
+	// Release lists arches and both index files under MD5Sum/SHA256.
+	w = serve("Release")
+	rel := w.Body.String()
+	if w.Code != 200 {
+		t.Fatalf("Release code %d", w.Code)
+	}
+	for _, want := range []string{"Date:", "Architectures: amd64 arm64", "Acquire-By-Hash: no", "MD5Sum:", "SHA256:", " Packages\n", " Packages.gz\n"} {
+		if !strings.Contains(rel, want) {
+			t.Errorf("Release missing %q:\n%s", want, rel)
+		}
+	}
+
+	// Unsigned trust model: no InRelease / Release.gpg served here.
+	for _, path := range []string{"InRelease", "Release.gpg", "pool/aaa_1.0_amd64.deb"} {
+		w := httptest.NewRecorder()
+		r := httptest.NewRequest(http.MethodGet, "/"+path, nil)
+		if p.ServeLocalIndex(w, r, reader, "myrepo", path) {
+			t.Errorf("ServeLocalIndex should return false for %q", path)
+		}
+	}
+}
+
+// Real apt appends the flat-repo dist "./" verbatim, so it requests "./Packages"
+// / "./Release" (curl pre-normalizes /./ which masks this). The handler must
+// collapse the dot-segment and return the same bytes as the un-prefixed request.
+func TestDebServeLocalIndexAptDotSegment(t *testing.T) {
+	p := &Provider{}
+	reader := fakeDebReader{metas: []provider.DebMetadata{
+		{Name: "aaa", Version: "1.0", Architecture: "amd64", FilePath: "pool/aaa_1.0_amd64.deb",
+			Control: "Package: aaa\nVersion: 1.0\nArchitecture: amd64", Size: 100, MD5: "md5aaa", SHA256: "sha256aaa"},
+	}}
+
+	serve := func(path string) *httptest.ResponseRecorder {
+		w := httptest.NewRecorder()
+		r := httptest.NewRequest(http.MethodGet, "/"+path, nil)
+		if !p.ServeLocalIndex(w, r, reader, "myrepo", path) {
+			t.Fatalf("ServeLocalIndex returned false for %q", path)
+		}
+		return w
+	}
+
+	// Packages is deterministic: require exact byte identity.
+	if plain, dotted := serve("Packages"), serve("./Packages"); plain.Code != 200 || dotted.Code != 200 {
+		t.Fatalf("Packages: plain=%d dotted=%d, want 200/200", plain.Code, dotted.Code)
+	} else if !bytes.Equal(plain.Body.Bytes(), dotted.Body.Bytes()) {
+		t.Error("./Packages body differs from Packages body")
+	}
+
+	// Release carries a Date: header stamped from time.Now(); compare the rest.
+	plain, dotted := serve("Release"), serve("./Release")
+	if plain.Code != 200 || dotted.Code != 200 {
+		t.Fatalf("Release: plain=%d dotted=%d, want 200/200", plain.Code, dotted.Code)
+	}
+	if stripDate(plain.Body.String()) != stripDate(dotted.Body.String()) {
+		t.Error("./Release body differs from Release body (ignoring Date)")
+	}
+}
+
+func stripDate(s string) string {
+	var out []string
+	for _, line := range strings.Split(s, "\n") {
+		if strings.HasPrefix(line, "Date:") {
+			continue
+		}
+		out = append(out, line)
+	}
+	return strings.Join(out, "\n")
+}
+
+func TestDebServeMetadataError(t *testing.T) {
+	p := &Provider{}
+	for _, path := range []string{"Packages", "Packages.gz", "Release"} {
+		w := httptest.NewRecorder()
+		r := httptest.NewRequest(http.MethodGet, "/"+path, nil)
+		p.ServeLocalIndex(w, r, errDebReader{}, "repo", path)
+		if w.Code != 500 {
+			t.Errorf("%s with failing reader = %d, want 500", path, w.Code)
+		}
+	}
+}
+
+func TestDebGenerateLocalIndexUnsupported(t *testing.T) {
+	if _, err := (&Provider{}).GenerateLocalIndex(context.Background(), fakeDebReader{}, "r", "Packages"); err == nil {
+		t.Error("expected unsupported error")
+	}
+}
+
+// buildDeb assembles an ar .deb whose control member uses the given name and
+// compressor, so the decompression branches can be exercised directly.
+func buildDeb(name, version, arch, member string, comp func([]byte) []byte) []byte {
+	control := "Package: " + name + "\nVersion: " + version + "\nArchitecture: " + arch + "\n"
+	controlTar := comp(tarSingle("./control", []byte(control)))
+
+	var buf bytes.Buffer
+	buf.WriteString("!<arch>\n")
+	arWrite(&buf, "debian-binary", []byte("2.0\n"))
+	arWrite(&buf, member, controlTar)
+	arWrite(&buf, "data.tar.gz", gzipBytes(tarSingle("./x", []byte("x"))))
+	return buf.Bytes()
+}
+
+func tarSingle(name string, data []byte) []byte {
+	var buf bytes.Buffer
+	tw := tar.NewWriter(&buf)
+	tw.WriteHeader(&tar.Header{Name: name, Mode: 0o644, Size: int64(len(data)), Typeflag: tar.TypeReg})
+	tw.Write(data)
+	tw.Close()
+	return buf.Bytes()
+}
+
+func arWrite(buf *bytes.Buffer, name string, data []byte) {
+	fmt.Fprintf(buf, "%-16s%-12s%-6s%-6s%-8s%-10d`\n", name, "0", "0", "0", "100644", len(data))
+	buf.Write(data)
+	if len(data)%2 == 1 {
+		buf.WriteByte('\n')
+	}
+}
+
+func xzBytes(data []byte) []byte {
+	var buf bytes.Buffer
+	w, _ := xz.NewWriter(&buf)
+	w.Write(data)
+	w.Close()
+	return buf.Bytes()
+}
+
+func zstdBytes(data []byte) []byte {
+	var buf bytes.Buffer
+	w, _ := zstd.NewWriter(&buf)
+	w.Write(data)
+	w.Close()
+	return buf.Bytes()
+}

internal/provider/deb/github.go

@@ -0,0 +1,724 @@
+package deb
+
+import (
+	"context"
+	"crypto/sha256"
+	"encoding/hex"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io"
+	"log/slog"
+	"net/http"
+	"net/url"
+	"regexp"
+	"strconv"
+	"strings"
+	"sync"
+	"time"
+
+	"golang.org/x/time/rate"
+
+	"git.unkin.net/unkin/artifactapi/internal/githubauth"
+	"git.unkin.net/unkin/artifactapi/internal/provider"
+	"git.unkin.net/unkin/artifactapi/pkg/models"
+)
+
+// gitHubProvider is the process-wide singleton for github_deb. The background
+// Syncer binds its shared rate limiter and work queue onto this instance so the
+// request path and the syncer drive the same derive machinery.
+var gitHubProvider = newGitHubProvider()
+
+func init() {
+	provider.Register(gitHubProvider)
+}
+
+// Tuning knobs for the no-precache control fetch. A .deb is an ar archive whose
+// control.tar member sits right after the tiny debian-binary member, so a small
+// front prefix reliably covers it.
+const (
+	defaultHeaderRangeInitial = 32 << 10 // 32 KiB — covers control.tar of almost every .deb
+	defaultHeaderRangeMax     = 16 << 20 // 16 MiB — give up past this and skip the asset
+	defaultReleasePageCap     = 10       // 100 releases/page * 10 pages
+
+	defaultScanTimeout  = 10 * time.Minute
+	defaultServeTimeout = 30 * time.Second
+	defaultColdWait     = 8 * time.Second
+)
+
+// GitHubProvider is a metadata-only remote: it scans a GitHub repo's releases
+// for .deb assets, derives per-asset control metadata via a ranged prefix fetch
+// (never downloading whole packages), synthesizes a flat apt repository from that
+// cached metadata, and redirects package downloads to a backend "releases_remote"
+// (the generic github.com remote) that serves the actual bytes.
+type GitHubProvider struct {
+	client *http.Client
+
+	headerInitial int64
+	headerMax     int64
+	pageCap       int
+	scanTimeout   time.Duration
+	serveTimeout  time.Duration
+	coldWait      time.Duration
+
+	limiter *rate.Limiter
+	syncer  *Syncer
+
+	serverCred githubauth.Credential
+
+	mu       sync.Mutex
+	scanning map[string]bool
+	lastScan map[string]time.Time
+}
+
+func newGitHubProvider() *GitHubProvider {
+	return &GitHubProvider{
+		client:        &http.Client{},
+		headerInitial: defaultHeaderRangeInitial,
+		headerMax:     defaultHeaderRangeMax,
+		pageCap:       defaultReleasePageCap,
+		scanTimeout:   defaultScanTimeout,
+		serveTimeout:  defaultServeTimeout,
+		coldWait:      defaultColdWait,
+		scanning:      map[string]bool{},
+		lastScan:      map[string]time.Time{},
+	}
+}
+
+func (p *GitHubProvider) limiterWait(ctx context.Context) error {
+	if p.limiter == nil {
+		return nil
+	}
+	return p.limiter.Wait(ctx)
+}
+
+func (p *GitHubProvider) Type() models.PackageType { return models.PackageGitHubDeb }
+
+func (p *GitHubProvider) Classify(path string) provider.Mutability {
+	switch path {
+	case "Packages", "Packages.gz", "Release", "InRelease", "Release.gpg":
+		return provider.Mutable
+	}
+	return provider.Immutable
+}
+
+func (p *GitHubProvider) ContentType(path string) string {
+	switch {
+	case strings.HasSuffix(path, ".deb"):
+		return "application/vnd.debian.binary-package"
+	case strings.HasSuffix(path, ".gz"):
+		return "application/gzip"
+	case path == "Packages" || path == "Release" || path == "InRelease":
+		return "text/plain"
+	}
+	return "application/octet-stream"
+}
+
+func (p *GitHubProvider) UpstreamURL(remote models.Remote, path string) string {
+	return strings.TrimRight(remote.BaseURL, "/") + "/" + strings.TrimLeft(path, "/")
+}
+
+func (p *GitHubProvider) RewriteResponse(_ []byte, _ models.Remote, _ string) ([]byte, error) {
+	return nil, nil
+}
+
+func (p *GitHubProvider) AuthHeaders(ctx context.Context, remote models.Remote) (http.Header, error) {
+	return p.githubHeaders(ctx, remote, false)
+}
+
+// ServeRemote answers a request against a github_deb remote. It refreshes the
+// derived metadata (bounded by mutable_ttl), serves a synthesized flat apt repo
+// (Packages/Packages.gz/Release), 404s the signed index variants (the repo is
+// consumed via [trusted=yes]), and 302-redirects .deb downloads to the backend
+// releases_remote. Returns false only for paths it does not own.
+func (p *GitHubProvider) ServeRemote(w http.ResponseWriter, r *http.Request, remote models.Remote, reqPath, proxyBaseURL string, store provider.RemoteMetadataStore) bool {
+	p.onRequest(remote, store)
+
+	// apt appends the flat-repo dist "./" verbatim, so it asks for "./Packages"
+	// etc.; collapse the dot-segment before matching the synthesized index.
+	path := normalizeIndexPath(reqPath)
+
+	switch path {
+	case "Packages", "Packages.gz", "Release":
+		p.serveIndex(w, r, remote, path, store)
+		return true
+	case "InRelease", "Release.gpg":
+		// Unsigned flat repo: apt consumes it with [trusted=yes]. Signal absence
+		// so apt falls back to the plain Release without waiting on a signature.
+		http.Error(w, "not found", http.StatusNotFound)
+		return true
+	}
+
+	if strings.HasSuffix(path, ".deb") {
+		if remote.ReleasesRemote == "" {
+			http.Error(w, "github_deb remote has no releases_remote configured for downloads", http.StatusInternalServerError)
+			return true
+		}
+		loc := strings.TrimRight(proxyBaseURL, "/") + "/api/v1/remote/" + remote.ReleasesRemote + "/" + strings.TrimLeft(path, "/")
+		http.Redirect(w, r, loc, http.StatusFound)
+		return true
+	}
+
+	return false
+}
+
+func (p *GitHubProvider) serveIndex(w http.ResponseWriter, r *http.Request, remote models.Remote, path string, store provider.RemoteMetadataStore) {
+	// Serve on a context detached from the inbound request so a client disconnect
+	// never cancels the metadata DB read and surfaces as a 500.
+	sctx, cancel := context.WithTimeout(context.WithoutCancel(r.Context()), p.serveTimeout)
+	defer cancel()
+
+	if p.syncer != nil && !p.ensurePrimed(sctx, remote, store) {
+		w.Header().Set("Retry-After", "5")
+		http.Error(w, "metadata is being prepared, retry shortly", http.StatusServiceUnavailable)
+		return
+	}
+
+	reader, ok := store.(provider.DebMetadataReader)
+	if !ok {
+		http.Error(w, "deb metadata not available", http.StatusInternalServerError)
+		return
+	}
+	metas, err := reader.ListDebMetadataEntries(sctx, remote.Name)
+	if err != nil {
+		if errors.Is(err, context.Canceled) || errors.Is(err, context.DeadlineExceeded) {
+			http.Error(w, "metadata read canceled", http.StatusServiceUnavailable)
+			return
+		}
+		http.Error(w, err.Error(), http.StatusInternalServerError)
+		return
+	}
+
+	switch path {
+	case "Packages":
+		w.Header().Set("Content-Type", "text/plain")
+		w.WriteHeader(http.StatusOK)
+		w.Write(generatePackages(metas))
+	case "Packages.gz":
+		w.Header().Set("Content-Type", "application/gzip")
+		w.WriteHeader(http.StatusOK)
+		w.Write(gzipBytes(generatePackages(metas)))
+	case "Release":
+		w.Header().Set("Content-Type", "text/plain")
+		w.WriteHeader(http.StatusOK)
+		w.Write(generateRelease(metas))
+	}
+}
+
+// onRequest keeps a remote's derived metadata fresh off the request path.
+func (p *GitHubProvider) onRequest(remote models.Remote, store provider.RemoteMetadataStore) {
+	if p.syncer != nil {
+		p.syncer.enqueue(remote, false)
+		return
+	}
+	p.refresh(remote, store)
+}
+
+// ensurePrimed returns true once the remote has at least one cached row. On an
+// empty cache it enqueues a prime and polls briefly for it to land.
+func (p *GitHubProvider) ensurePrimed(ctx context.Context, remote models.Remote, store provider.RemoteMetadataStore) bool {
+	if !p.cacheEmpty(ctx, store, remote.Name) {
+		return true
+	}
+	if p.syncer != nil {
+		p.syncer.enqueue(remote, true)
+	}
+
+	deadline := time.Now().Add(p.coldWait)
+	for time.Now().Before(deadline) {
+		select {
+		case <-ctx.Done():
+			return false
+		case <-time.After(400 * time.Millisecond):
+		}
+		if !p.cacheEmpty(ctx, store, remote.Name) {
+			return true
+		}
+	}
+	return false
+}
+
+func (p *GitHubProvider) cacheEmpty(ctx context.Context, store provider.RemoteMetadataStore, name string) bool {
+	reader, ok := store.(provider.DebMetadataReader)
+	if !ok {
+		return false
+	}
+	rows, err := reader.ListDebMetadataEntries(ctx, name)
+	if err != nil {
+		return false
+	}
+	return len(rows) == 0
+}
+
+// refresh brings the derived metadata up to date without coupling the scan to
+// the inbound request (legacy inline path used without a syncer / in unit tests).
+func (p *GitHubProvider) refresh(remote models.Remote, store provider.RemoteMetadataStore) {
+	ttl := time.Duration(remote.MutableTTL) * time.Second
+	if ttl <= 0 {
+		ttl = 5 * time.Minute
+	}
+
+	p.mu.Lock()
+	last, ok := p.lastScan[remote.Name]
+	fresh := ok && time.Since(last) < ttl
+	if fresh || p.scanning[remote.Name] {
+		p.mu.Unlock()
+		return
+	}
+	p.scanning[remote.Name] = true
+	p.mu.Unlock()
+
+	if p.cacheEmpty(context.Background(), store, remote.Name) {
+		p.runScan(remote, store)
+		return
+	}
+	go p.runScan(remote, store)
+}
+
+func (p *GitHubProvider) runScan(remote models.Remote, store provider.RemoteMetadataStore) {
+	defer func() {
+		p.mu.Lock()
+		delete(p.scanning, remote.Name)
+		p.mu.Unlock()
+	}()
+
+	ctx, cancel := context.WithTimeout(context.Background(), p.scanTimeout)
+	defer cancel()
+
+	if err := p.scan(ctx, remote, store); err != nil {
+		slog.Error("github_deb: release scan failed", "remote", remote.Name, "error", err)
+		return
+	}
+
+	p.mu.Lock()
+	p.lastScan[remote.Name] = time.Now()
+	p.mu.Unlock()
+}
+
+// scan runs a full unconditional derive. Retained for the legacy inline refresh
+// path and existing tests; the syncer uses scanWithState.
+func (p *GitHubProvider) scan(ctx context.Context, remote models.Remote, store provider.RemoteMetadataStore) error {
+	_, _, err := p.scanWithState(ctx, remote, store, "")
+	return err
+}
+
+// scanWithState derives metadata incrementally. It sends the prior releases-list
+// ETag as a conditional request: a 304 means nothing changed. On a 200 it diffs
+// the release assets against the cache, derives only new/changed assets, prunes
+// assets that disappeared, and returns the new ETag.
+func (p *GitHubProvider) scanWithState(ctx context.Context, remote models.Remote, store provider.RemoteMetadataStore, etag string) (newEtag string, changed bool, err error) {
+	releases, newEtag, notModified, err := p.fetchReleases(ctx, remote, etag)
+	if err != nil {
+		return etag, false, err
+	}
+	if notModified {
+		return etag, false, nil
+	}
+
+	reader, ok := store.(provider.DebMetadataReader)
+	if !ok {
+		return newEtag, false, errors.New("store does not support deb metadata reads")
+	}
+	existing, err := reader.ListDebMetadataEntries(ctx, remote.Name)
+	if err != nil {
+		return newEtag, false, err
+	}
+	existingByPath := make(map[string]provider.DebMetadata, len(existing))
+	for _, m := range existing {
+		existingByPath[m.FilePath] = m
+	}
+
+	allow, err := compilePatterns(remote.Patterns)
+	if err != nil {
+		return newEtag, false, err
+	}
+
+	seen := map[string]bool{}
+	for _, rel := range releases {
+		if rel.Draft {
+			continue
+		}
+		for _, asset := range rel.Assets {
+			if !strings.HasSuffix(strings.ToLower(asset.Name), ".deb") {
+				continue
+			}
+			if !matchesAny(allow, asset.Name) {
+				continue
+			}
+			fp := assetPath(asset)
+			if fp == "" {
+				continue
+			}
+			seen[fp] = true
+
+			if cur, ok := existingByPath[fp]; ok {
+				if asset.Digest == "" || cur.ContentHash == asset.Digest {
+					continue
+				}
+				_ = store.DeleteDebMetadata(ctx, remote.Name, fp)
+			}
+
+			meta, err := p.deriveAsset(ctx, remote, asset, fp)
+			if err != nil {
+				slog.Warn("github_deb: derive asset failed", "remote", remote.Name, "asset", asset.Name, "error", err)
+				continue
+			}
+			if err := store.InsertDebMetadata(ctx, meta); err != nil {
+				slog.Error("github_deb: insert metadata failed", "remote", remote.Name, "asset", asset.Name, "error", err)
+				continue
+			}
+			slog.Info("github_deb: derived asset", "remote", remote.Name, "name", meta.Name, "version", meta.Version, "arch", meta.Architecture)
+		}
+	}
+
+	for fp := range existingByPath {
+		if !seen[fp] {
+			_ = store.DeleteDebMetadata(ctx, remote.Name, fp)
+		}
+	}
+	return newEtag, true, nil
+}
+
+type ghRelease struct {
+	TagName string    `json:"tag_name"`
+	Draft   bool      `json:"draft"`
+	Assets  []ghAsset `json:"assets"`
+}
+
+type ghAsset struct {
+	Name               string `json:"name"`
+	Size               int64  `json:"size"`
+	BrowserDownloadURL string `json:"browser_download_url"`
+	Digest             string `json:"digest"`
+}
+
+// fetchReleases lists a repo's releases, sending the prior ETag as If-None-Match
+// on page 1 so an unchanged repo short-circuits to notModified. Every call waits
+// on the shared limiter first.
+func (p *GitHubProvider) fetchReleases(ctx context.Context, remote models.Remote, etag string) (all []ghRelease, newEtag string, notModified bool, err error) {
+	base := strings.TrimRight(remote.BaseURL, "/") + "/releases"
+	for page := 1; page <= p.pageCap; page++ {
+		u := fmt.Sprintf("%s?per_page=100&page=%d", base, page)
+		req, err := http.NewRequestWithContext(ctx, http.MethodGet, u, nil)
+		if err != nil {
+			return nil, "", false, err
+		}
+		hdr, err := p.githubHeaders(ctx, remote, true)
+		if err != nil {
+			return nil, "", false, err
+		}
+		copyHeaders(req, hdr)
+		if page == 1 && etag != "" {
+			req.Header.Set("If-None-Match", etag)
+		}
+
+		if err := p.limiterWait(ctx); err != nil {
+			return nil, "", false, err
+		}
+		resp, err := p.client.Do(req)
+		if err != nil {
+			return nil, "", false, err
+		}
+		if page == 1 && resp.StatusCode == http.StatusNotModified {
+			io.Copy(io.Discard, resp.Body)
+			resp.Body.Close()
+			return nil, etag, true, nil
+		}
+		body, err := io.ReadAll(resp.Body)
+		respEtag := resp.Header.Get("ETag")
+		resp.Body.Close()
+		if err != nil {
+			return nil, "", false, err
+		}
+		if resp.StatusCode != http.StatusOK {
+			return nil, "", false, fmt.Errorf("github releases API %s: status %d", u, resp.StatusCode)
+		}
+		if page == 1 {
+			newEtag = respEtag
+		}
+		var releases []ghRelease
+		if err := json.Unmarshal(body, &releases); err != nil {
+			return nil, "", false, fmt.Errorf("decode releases: %w", err)
+		}
+		if len(releases) == 0 {
+			break
+		}
+		all = append(all, releases...)
+		if len(releases) < 100 {
+			break
+		}
+	}
+	return all, newEtag, false, nil
+}
+
+func (p *GitHubProvider) deriveAsset(ctx context.Context, remote models.Remote, asset ghAsset, fp string) (*provider.DebMetadata, error) {
+	control, err := p.fetchControl(ctx, remote, asset.BrowserDownloadURL)
+	if err != nil {
+		return nil, err
+	}
+	fields := parseControlFields(control)
+
+	meta := &provider.DebMetadata{
+		RepoName:     remote.Name,
+		FilePath:     fp,
+		Name:         fields["Package"],
+		Version:      fields["Version"],
+		Architecture: fields["Architecture"],
+		Control:      strings.TrimRight(control, "\n"),
+		Size:         asset.Size,
+	}
+	if meta.Name == "" {
+		return nil, errors.New("control missing Package field")
+	}
+
+	// The Packages SHA256 must be the sha256 of the whole .deb. Prefer GitHub's
+	// asset digest so we never download the body; only when it is absent (or not
+	// sha256) do we stream the asset once. MD5sum is left unset — apt verifies the
+	// download against SHA256 alone under [trusted=yes].
+	if h, ok := sha256FromDigest(asset.Digest); ok {
+		meta.ContentHash = "sha256:" + h
+		meta.SHA256 = h
+	} else {
+		h, err := p.computeSHA256(ctx, remote, asset.BrowserDownloadURL)
+		if err != nil {
+			return nil, fmt.Errorf("compute sha256: %w", err)
+		}
+		meta.ContentHash = "sha256:" + h
+		meta.SHA256 = h
+	}
+
+	return meta, nil
+}
+
+// fetchControl pulls only the front of the .deb with a ranged GET and extracts
+// the control paragraph from it. control.tar sits right after the tiny
+// debian-binary member, so a small prefix suffices; a prefix that truncates the
+// control member doubles the range and retries.
+func (p *GitHubProvider) fetchControl(ctx context.Context, remote models.Remote, downloadURL string) (string, error) {
+	n := p.headerInitial
+	for {
+		body, full, err := p.rangeGet(ctx, remote, downloadURL, n)
+		if err != nil {
+			return "", err
+		}
+		control, complete, perr := controlFromPrefix(body)
+		if perr != nil {
+			return "", fmt.Errorf("parse deb control: %w", perr)
+		}
+		if complete {
+			return control, nil
+		}
+		if full || n >= p.headerMax {
+			return "", fmt.Errorf("control.tar not found within %d bytes of %s", n, downloadURL)
+		}
+		n *= 2
+		if n > p.headerMax {
+			n = p.headerMax
+		}
+	}
+}
+
+// controlFromPrefix parses the ar members present in a front prefix of a .deb.
+// It returns the ./control paragraph once control.tar.* is fully covered
+// (complete=true); a prefix too short to cover it returns complete=false so the
+// caller can widen the range. Later members (data.tar.*) are ignored.
+func controlFromPrefix(prefix []byte) (control string, complete bool, err error) {
+	const magic = "!<arch>\n"
+	if len(prefix) < len(magic) {
+		return "", false, nil
+	}
+	if string(prefix[:len(magic)]) != magic {
+		return "", false, errors.New("not an ar archive")
+	}
+	off := len(magic)
+	for {
+		if off+60 > len(prefix) {
+			return "", false, nil
+		}
+		hdr := prefix[off : off+60]
+		off += 60
+		name := strings.TrimSuffix(strings.TrimRight(string(hdr[0:16]), " "), "/")
+		size, err := strconv.ParseInt(strings.TrimSpace(string(hdr[48:58])), 10, 64)
+		if err != nil {
+			return "", false, fmt.Errorf("bad ar size for %q: %w", name, err)
+		}
+		if strings.HasPrefix(name, "control.tar") {
+			if off+int(size) > len(prefix) {
+				return "", false, nil
+			}
+			tarBytes, err := decompress(name, prefix[off:off+int(size)])
+			if err != nil {
+				return "", false, err
+			}
+			c, err := readControlParagraph(tarBytes)
+			if err != nil {
+				return "", false, err
+			}
+			return c, true, nil
+		}
+		if off+int(size) > len(prefix) {
+			return "", false, nil
+		}
+		off += int(size)
+		if size%2 == 1 {
+			off++
+		}
+	}
+}
+
+// rangeGet returns the first n bytes of downloadURL. full is true when the
+// response body was shorter than n (i.e. we already have the whole object).
+func (p *GitHubProvider) rangeGet(ctx context.Context, remote models.Remote, downloadURL string, n int64) ([]byte, bool, error) {
+	req, err := http.NewRequestWithContext(ctx, http.MethodGet, downloadURL, nil)
+	if err != nil {
+		return nil, false, err
+	}
+	hdr, err := p.githubHeaders(ctx, remote, false)
+	if err != nil {
+		return nil, false, err
+	}
+	copyHeaders(req, hdr)
+	req.Header.Set("Range", fmt.Sprintf("bytes=0-%d", n-1))
+
+	if err := p.limiterWait(ctx); err != nil {
+		return nil, false, err
+	}
+	resp, err := p.client.Do(req)
+	if err != nil {
+		return nil, false, err
+	}
+	defer resp.Body.Close()
+	if resp.StatusCode != http.StatusOK && resp.StatusCode != http.StatusPartialContent {
+		return nil, false, fmt.Errorf("range GET %s: status %d", downloadURL, resp.StatusCode)
+	}
+
+	body, err := io.ReadAll(io.LimitReader(resp.Body, n))
+	if err != nil {
+		return nil, false, err
+	}
+	full := int64(len(body)) < n
+	return body, full, nil
+}
+
+func (p *GitHubProvider) computeSHA256(ctx context.Context, remote models.Remote, downloadURL string) (string, error) {
+	req, err := http.NewRequestWithContext(ctx, http.MethodGet, downloadURL, nil)
+	if err != nil {
+		return "", err
+	}
+	hdr, err := p.githubHeaders(ctx, remote, false)
+	if err != nil {
+		return "", err
+	}
+	copyHeaders(req, hdr)
+
+	if err := p.limiterWait(ctx); err != nil {
+		return "", err
+	}
+	resp, err := p.client.Do(req)
+	if err != nil {
+		return "", err
+	}
+	defer resp.Body.Close()
+	if resp.StatusCode != http.StatusOK {
+		return "", fmt.Errorf("GET %s: status %d", downloadURL, resp.StatusCode)
+	}
+
+	h := sha256.New()
+	if _, err := io.Copy(h, resp.Body); err != nil {
+		return "", err
+	}
+	return hex.EncodeToString(h.Sum(nil)), nil
+}
+
+// assetPath is the package's location relative to github.com — the path the
+// backend releases_remote (base https://github.com) proxies. It doubles as the
+// deb_metadata key and the Filename field in the Packages index, so a .deb
+// download resolves back to this remote and redirects to the backend.
+func assetPath(asset ghAsset) string {
+	u, err := url.Parse(asset.BrowserDownloadURL)
+	if err != nil {
+		return ""
+	}
+	return strings.TrimPrefix(u.Path, "/")
+}
+
+func sha256FromDigest(digest string) (string, bool) {
+	if strings.HasPrefix(digest, "sha256:") {
+		return strings.TrimPrefix(digest, "sha256:"), true
+	}
+	return "", false
+}
+
+// githubHeaders builds the outbound headers for a GitHub request, attaching a
+// bearer credential when one is available. A per-remote credential wins; absent
+// that, the process-wide server credential is used; absent both, the request is
+// unauthenticated.
+func (p *GitHubProvider) githubHeaders(ctx context.Context, remote models.Remote, api bool) (http.Header, error) {
+	h := http.Header{}
+	if api {
+		h.Set("Accept", "application/vnd.github+json")
+		h.Set("X-GitHub-Api-Version", "2022-11-28")
+	}
+	tok, err := p.githubToken(ctx, remote)
+	if err != nil {
+		return nil, err
+	}
+	if tok != "" {
+		h.Set("Authorization", "Bearer "+tok)
+	}
+	return h, nil
+}
+
+// githubToken resolves the bearer token for a remote. Precedence: a per-remote
+// credential (password, then username) overrides the server credential.
+func (p *GitHubProvider) githubToken(ctx context.Context, remote models.Remote) (string, error) {
+	if remote.Password != "" {
+		return remote.Password, nil
+	}
+	if remote.Username != "" {
+		return remote.Username, nil
+	}
+	if c := p.serverCredential(); c != nil {
+		return c.Token(ctx)
+	}
+	return "", nil
+}
+
+func (p *GitHubProvider) serverCredential() githubauth.Credential {
+	if p.serverCred != nil {
+		return p.serverCred
+	}
+	return githubauth.Server()
+}
+
+func copyHeaders(req *http.Request, h http.Header) {
+	for k, vals := range h {
+		for _, v := range vals {
+			req.Header.Add(k, v)
+		}
+	}
+}
+
+func compilePatterns(patterns []string) ([]*regexp.Regexp, error) {
+	var out []*regexp.Regexp
+	for _, p := range patterns {
+		re, err := regexp.Compile(p)
+		if err != nil {
+			return nil, fmt.Errorf("invalid pattern %q: %w", p, err)
+		}
+		out = append(out, re)
+	}
+	return out, nil
+}
+
+func matchesAny(res []*regexp.Regexp, s string) bool {
+	if len(res) == 0 {
+		return true
+	}
+	for _, re := range res {
+		if re.MatchString(s) {
+			return true
+		}
+	}
+	return false
+}

internal/provider/deb/github_test.go

@@ -0,0 +1,462 @@
+package deb
+
+import (
+	"bytes"
+	"compress/gzip"
+	"context"
+	"crypto/sha256"
+	"encoding/hex"
+	"encoding/json"
+	"fmt"
+	"io"
+	"net/http"
+	"net/http/httptest"
+	"strconv"
+	"strings"
+	"sync"
+	"testing"
+	"time"
+
+	"git.unkin.net/unkin/artifactapi/internal/provider"
+	"git.unkin.net/unkin/artifactapi/internal/testsupport"
+	"git.unkin.net/unkin/artifactapi/pkg/models"
+)
+
+// fakeStore is an in-memory provider.RemoteMetadataStore + DebMetadataReader
+// keyed by file_path, mirroring the (repo_name, file_path) uniqueness of the
+// real deb_metadata table.
+type fakeStore struct {
+	mu   sync.Mutex
+	rows map[string]provider.DebMetadata
+}
+
+func newFakeStore() *fakeStore { return &fakeStore{rows: map[string]provider.DebMetadata{}} }
+
+func (f *fakeStore) InsertDebMetadata(_ context.Context, m *provider.DebMetadata) error {
+	f.mu.Lock()
+	defer f.mu.Unlock()
+	if _, ok := f.rows[m.FilePath]; ok {
+		return nil // ON CONFLICT DO NOTHING
+	}
+	f.rows[m.FilePath] = *m
+	return nil
+}
+
+func (f *fakeStore) DeleteDebMetadata(_ context.Context, _, filePath string) error {
+	f.mu.Lock()
+	defer f.mu.Unlock()
+	delete(f.rows, filePath)
+	return nil
+}
+
+func (f *fakeStore) InsertRPMMetadata(context.Context, *provider.RPMMetadata) error { return nil }
+func (f *fakeStore) DeleteRPMMetadata(context.Context, string, string) error        { return nil }
+func (f *fakeStore) ListRPMMetadataEntries(context.Context, string) ([]provider.RPMMetadata, error) {
+	return nil, nil
+}
+
+func (f *fakeStore) ListDebMetadataEntries(ctx context.Context, _ string) ([]provider.DebMetadata, error) {
+	if err := ctx.Err(); err != nil {
+		return nil, err
+	}
+	f.mu.Lock()
+	defer f.mu.Unlock()
+	out := make([]provider.DebMetadata, 0, len(f.rows))
+	for _, m := range f.rows {
+		out = append(out, m)
+	}
+	return out, nil
+}
+
+// githubFixture serves the releases API and the .deb asset downloads (with Range
+// support) for a set of packages. digest controls whether the asset carries a
+// sha256 digest (no-download path) or not (compute path).
+type githubFixture struct {
+	srv         *httptest.Server
+	debBytes    map[string][]byte
+	rangeHit    map[string]int
+	fullHit     map[string]int
+	etag        string
+	releasesHit int
+	notModHit   int
+	releaseAuth string
+	assetAuth   string
+	mu          sync.Mutex
+}
+
+func newGitHubFixture(t *testing.T, withDigest bool) *githubFixture {
+	t.Helper()
+	f := &githubFixture{
+		debBytes: map[string][]byte{},
+		rangeHit: map[string]int{},
+		fullHit:  map[string]int{},
+	}
+	f.debBytes["demo_1.2-3_amd64.deb"] = testsupport.MinimalDeb("demo", "1.2-3", "amd64")
+
+	mux := http.NewServeMux()
+	mux.HandleFunc("/repos/acme/tools/releases", func(w http.ResponseWriter, r *http.Request) {
+		page := r.URL.Query().Get("page")
+		if page != "" && page != "1" {
+			w.Write([]byte("[]"))
+			return
+		}
+		f.mu.Lock()
+		f.releasesHit++
+		f.releaseAuth = r.Header.Get("Authorization")
+		etag := f.etag
+		if etag != "" && r.Header.Get("If-None-Match") == etag {
+			f.notModHit++
+			f.mu.Unlock()
+			w.WriteHeader(http.StatusNotModified)
+			return
+		}
+		f.mu.Unlock()
+		if etag != "" {
+			w.Header().Set("ETag", etag)
+		}
+		var assets []map[string]any
+		for name := range f.debBytes {
+			a := map[string]any{
+				"name":                 name,
+				"size":                 len(f.debBytes[name]),
+				"browser_download_url": f.srv.URL + "/acme/tools/releases/download/v1.2-3/" + name,
+			}
+			if withDigest {
+				sum := sha256.Sum256(f.debBytes[name])
+				a["digest"] = "sha256:" + hex.EncodeToString(sum[:])
+			}
+			assets = append(assets, a)
+		}
+		rel := []map[string]any{{"tag_name": "v1.2-3", "draft": false, "assets": assets}}
+		json.NewEncoder(w).Encode(rel)
+	})
+	mux.HandleFunc("/acme/tools/releases/download/", func(w http.ResponseWriter, r *http.Request) {
+		name := r.URL.Path[strings.LastIndex(r.URL.Path, "/")+1:]
+		body, ok := f.debBytes[name]
+		if !ok {
+			http.Error(w, "not found", 404)
+			return
+		}
+		rng := r.Header.Get("Range")
+		f.mu.Lock()
+		f.assetAuth = r.Header.Get("Authorization")
+		if rng != "" {
+			f.rangeHit[name]++
+		} else {
+			f.fullHit[name]++
+		}
+		f.mu.Unlock()
+
+		if rng == "" {
+			w.WriteHeader(200)
+			w.Write(body)
+			return
+		}
+		var end int
+		fmt.Sscanf(rng, "bytes=0-%d", &end)
+		if end >= len(body)-1 {
+			end = len(body) - 1
+		}
+		w.Header().Set("Content-Range", fmt.Sprintf("bytes 0-%d/%d", end, len(body)))
+		w.Header().Set("Content-Length", strconv.Itoa(end+1))
+		w.WriteHeader(http.StatusPartialContent)
+		w.Write(body[:end+1])
+	})
+	f.srv = httptest.NewServer(mux)
+	t.Cleanup(f.srv.Close)
+	return f
+}
+
+func (f *githubFixture) remote() models.Remote {
+	return models.Remote{
+		Name:           "acme-deb",
+		PackageType:    models.PackageGitHubDeb,
+		BaseURL:        f.srv.URL + "/repos/acme/tools",
+		ReleasesRemote: "github",
+		MutableTTL:     3600,
+	}
+}
+
+func newTestProvider() *GitHubProvider {
+	p := newGitHubProvider()
+	p.headerInitial = 32 // force the ranged-fetch retry loop against the tiny fixture
+	p.headerMax = 1 << 20
+	return p
+}
+
+const demoPath = "acme/tools/releases/download/v1.2-3/demo_1.2-3_amd64.deb"
+
+func TestGitHubScanDerivesControlFromPrefixAndDigest(t *testing.T) {
+	fx := newGitHubFixture(t, true)
+	p := newTestProvider()
+	store := newFakeStore()
+
+	if err := p.scan(context.Background(), fx.remote(), store); err != nil {
+		t.Fatalf("scan: %v", err)
+	}
+
+	metas, _ := store.ListDebMetadataEntries(context.Background(), "acme-deb")
+	if len(metas) != 1 {
+		t.Fatalf("want 1 metadata row, got %d", len(metas))
+	}
+	m := metas[0]
+	if m.Name != "demo" || m.Version != "1.2-3" || m.Architecture != "amd64" {
+		t.Fatalf("bad control fields: %+v", m)
+	}
+	if m.FilePath != demoPath {
+		t.Fatalf("FilePath = %q, want %q", m.FilePath, demoPath)
+	}
+	if int(m.Size) != len(fx.debBytes["demo_1.2-3_amd64.deb"]) {
+		t.Fatalf("Size = %d, want %d", m.Size, len(fx.debBytes["demo_1.2-3_amd64.deb"]))
+	}
+	sum := sha256.Sum256(fx.debBytes["demo_1.2-3_amd64.deb"])
+	if m.SHA256 != hex.EncodeToString(sum[:]) {
+		t.Fatalf("SHA256 = %q, want digest", m.SHA256)
+	}
+	if m.ContentHash != "sha256:"+hex.EncodeToString(sum[:]) {
+		t.Fatalf("ContentHash = %q", m.ContentHash)
+	}
+	if m.MD5 != "" {
+		t.Fatalf("MD5 should be unset for metadata-only derive, got %q", m.MD5)
+	}
+	if fx.fullHit["demo_1.2-3_amd64.deb"] != 0 {
+		t.Fatalf("expected no full download when digest present, got %d", fx.fullHit["demo_1.2-3_amd64.deb"])
+	}
+	if fx.rangeHit["demo_1.2-3_amd64.deb"] == 0 {
+		t.Fatalf("expected ranged control fetch")
+	}
+	if !strings.Contains(m.Control, "Package: demo") {
+		t.Fatalf("raw control not captured: %q", m.Control)
+	}
+}
+
+func TestGitHubChecksumComputedWhenDigestAbsent(t *testing.T) {
+	fx := newGitHubFixture(t, false)
+	p := newTestProvider()
+	store := newFakeStore()
+
+	if err := p.scan(context.Background(), fx.remote(), store); err != nil {
+		t.Fatalf("scan: %v", err)
+	}
+	metas, _ := store.ListDebMetadataEntries(context.Background(), "acme-deb")
+	if len(metas) != 1 {
+		t.Fatalf("want 1 row, got %d", len(metas))
+	}
+	sum := sha256.Sum256(fx.debBytes["demo_1.2-3_amd64.deb"])
+	if metas[0].SHA256 != hex.EncodeToString(sum[:]) {
+		t.Fatalf("computed checksum mismatch: %q", metas[0].SHA256)
+	}
+	if fx.fullHit["demo_1.2-3_amd64.deb"] == 0 {
+		t.Fatalf("expected a full download to compute sha256 when digest absent")
+	}
+}
+
+func TestGitHubServeRemoteIndexAndRedirect(t *testing.T) {
+	fx := newGitHubFixture(t, true)
+	p := newTestProvider()
+	store := newFakeStore()
+	remote := fx.remote()
+	const proxyBase = "https://artifactapi.example"
+
+	// Release is served and triggers the initial scan.
+	rec := httptest.NewRecorder()
+	req := httptest.NewRequest(http.MethodGet, "/api/v1/remote/acme-deb/Release", nil)
+	if !p.ServeRemote(rec, req, remote, "Release", proxyBase, store) {
+		t.Fatal("ServeRemote did not handle Release")
+	}
+	if rec.Code != 200 || !strings.Contains(rec.Body.String(), "Architectures:") {
+		t.Fatalf("Release bad: code=%d body=%s", rec.Code, rec.Body.String())
+	}
+	if !strings.Contains(rec.Body.String(), "amd64") {
+		t.Fatalf("Release missing arch: %s", rec.Body.String())
+	}
+
+	// Packages carries the package with a Filename that is the github-relative
+	// download path (so it resolves back to this remote and redirects).
+	rec = httptest.NewRecorder()
+	req = httptest.NewRequest(http.MethodGet, "/x", nil)
+	if !p.ServeRemote(rec, req, remote, "Packages", proxyBase, store) {
+		t.Fatal("ServeRemote did not handle Packages")
+	}
+	pkgs := rec.Body.String()
+	if !strings.Contains(pkgs, "Package: demo") {
+		t.Fatalf("Packages missing package: %s", pkgs)
+	}
+	if !strings.Contains(pkgs, "Filename: "+demoPath) {
+		t.Fatalf("Packages missing/incorrect Filename: %s", pkgs)
+	}
+	if !strings.Contains(pkgs, "SHA256: ") {
+		t.Fatalf("Packages missing SHA256: %s", pkgs)
+	}
+	if strings.Contains(pkgs, "MD5sum:") {
+		t.Fatalf("Packages should omit empty MD5sum: %s", pkgs)
+	}
+
+	// Packages.gz decompresses to the same content.
+	rec = httptest.NewRecorder()
+	req = httptest.NewRequest(http.MethodGet, "/x", nil)
+	if !p.ServeRemote(rec, req, remote, "Packages.gz", proxyBase, store) {
+		t.Fatal("ServeRemote did not handle Packages.gz")
+	}
+	gz, err := gzip.NewReader(rec.Body)
+	if err != nil {
+		t.Fatalf("gzip: %v", err)
+	}
+	unz, _ := io.ReadAll(gz)
+	if !strings.Contains(string(unz), "Package: demo") {
+		t.Fatalf("Packages.gz missing package: %s", unz)
+	}
+
+	// InRelease/Release.gpg 404 (unsigned, consumed via [trusted=yes]).
+	for _, sp := range []string{"InRelease", "Release.gpg"} {
+		rec = httptest.NewRecorder()
+		req = httptest.NewRequest(http.MethodGet, "/x", nil)
+		if !p.ServeRemote(rec, req, remote, sp, proxyBase, store) {
+			t.Fatalf("ServeRemote did not handle %s", sp)
+		}
+		if rec.Code != http.StatusNotFound {
+			t.Fatalf("%s want 404, got %d", sp, rec.Code)
+		}
+	}
+
+	// A .deb request redirects to the backend releases_remote.
+	rec = httptest.NewRecorder()
+	req = httptest.NewRequest(http.MethodGet, "/api/v1/remote/acme-deb/"+demoPath, nil)
+	if !p.ServeRemote(rec, req, remote, demoPath, proxyBase, store) {
+		t.Fatal("ServeRemote did not handle .deb")
+	}
+	if rec.Code != http.StatusFound {
+		t.Fatalf("want 302, got %d", rec.Code)
+	}
+	wantLoc := proxyBase + "/api/v1/remote/github/" + demoPath
+	if got := rec.Header().Get("Location"); got != wantLoc {
+		t.Fatalf("Location = %q, want %q", got, wantLoc)
+	}
+}
+
+// Real apt appends the flat-repo dist "./" verbatim, so the metadata-only remote
+// receives "./Packages" / "./Release"; ServeRemote must collapse the dot-segment
+// and synthesize the same index as the un-prefixed request.
+func TestGitHubServeRemoteAptDotSegment(t *testing.T) {
+	fx := newGitHubFixture(t, true)
+	p := newTestProvider()
+	store := newFakeStore()
+	remote := fx.remote()
+	const proxyBase = "https://artifactapi.example"
+
+	serve := func(path string) *httptest.ResponseRecorder {
+		rec := httptest.NewRecorder()
+		req := httptest.NewRequest(http.MethodGet, "/api/v1/remote/acme-deb/"+path, nil)
+		if !p.ServeRemote(rec, req, remote, path, proxyBase, store) {
+			t.Fatalf("ServeRemote did not handle %q", path)
+		}
+		return rec
+	}
+
+	// Packages is deterministic: byte-identical to the un-prefixed request.
+	plain, dotted := serve("Packages"), serve("./Packages")
+	if plain.Code != 200 || dotted.Code != 200 {
+		t.Fatalf("Packages: plain=%d dotted=%d, want 200/200", plain.Code, dotted.Code)
+	}
+	if !strings.Contains(dotted.Body.String(), "Package: demo") {
+		t.Fatalf("./Packages missing synthesized body: %s", dotted.Body.String())
+	}
+	if !bytes.Equal(plain.Body.Bytes(), dotted.Body.Bytes()) {
+		t.Error("./Packages body differs from Packages body")
+	}
+
+	// Release carries a time.Now() Date: header; compare the rest.
+	rPlain, rDotted := serve("Release"), serve("./Release")
+	if rPlain.Code != 200 || rDotted.Code != 200 {
+		t.Fatalf("Release: plain=%d dotted=%d, want 200/200", rPlain.Code, rDotted.Code)
+	}
+	if stripDate(rPlain.Body.String()) != stripDate(rDotted.Body.String()) {
+		t.Error("./Release body differs from Release body (ignoring Date)")
+	}
+}
+
+// A canceled inbound request must still serve the warm cache (detached context),
+// not turn the metadata read into a 500.
+func TestGitHubServeRemoteCanceledRequestServesCache(t *testing.T) {
+	fx := newGitHubFixture(t, true)
+	p := newTestProvider()
+	store := newFakeStore()
+	remote := fx.remote()
+
+	if err := p.scan(context.Background(), remote, store); err != nil {
+		t.Fatalf("warm scan: %v", err)
+	}
+	p.mu.Lock()
+	p.lastScan[remote.Name] = time.Now()
+	p.mu.Unlock()
+
+	ctx, cancel := context.WithCancel(context.Background())
+	cancel()
+	rec := httptest.NewRecorder()
+	req := httptest.NewRequest(http.MethodGet, "/api/v1/remote/acme-deb/Packages", nil).WithContext(ctx)
+
+	if !p.ServeRemote(rec, req, remote, "Packages", "https://x", store) {
+		t.Fatal("ServeRemote did not handle Packages")
+	}
+	if rec.Code != http.StatusOK {
+		t.Fatalf("canceled request must serve cache, not error; got code=%d body=%s", rec.Code, rec.Body.String())
+	}
+	if !strings.Contains(rec.Body.String(), "Package: demo") {
+		t.Fatalf("expected Packages served from cache, got %s", rec.Body.String())
+	}
+}
+
+func TestGitHubServeRemoteRedirectRequiresReleasesRemote(t *testing.T) {
+	fx := newGitHubFixture(t, true)
+	p := newTestProvider()
+	store := newFakeStore()
+	remote := fx.remote()
+	remote.ReleasesRemote = ""
+
+	rec := httptest.NewRecorder()
+	req := httptest.NewRequest(http.MethodGet, "/x", nil)
+	if !p.ServeRemote(rec, req, remote, demoPath, "https://x", store) {
+		t.Fatal("expected handled")
+	}
+	if rec.Code != http.StatusInternalServerError {
+		t.Fatalf("want 500 when releases_remote unset, got %d", rec.Code)
+	}
+}
+
+func TestGitHubScanPrunesRemovedAssets(t *testing.T) {
+	fx := newGitHubFixture(t, true)
+	p := newTestProvider()
+	store := newFakeStore()
+
+	if err := p.scan(context.Background(), fx.remote(), store); err != nil {
+		t.Fatalf("scan: %v", err)
+	}
+	if rows, _ := store.ListDebMetadataEntries(context.Background(), "acme-deb"); len(rows) != 1 {
+		t.Fatalf("want 1 row after first scan, got %d", len(rows))
+	}
+
+	delete(fx.debBytes, "demo_1.2-3_amd64.deb")
+	if err := p.scan(context.Background(), fx.remote(), store); err != nil {
+		t.Fatalf("rescan: %v", err)
+	}
+	if rows, _ := store.ListDebMetadataEntries(context.Background(), "acme-deb"); len(rows) != 0 {
+		t.Fatalf("want 0 rows after prune, got %d", len(rows))
+	}
+}
+
+func TestGitHubAssetPatternFilter(t *testing.T) {
+	fx := newGitHubFixture(t, true)
+	fx.debBytes["other_9_arm64.deb"] = testsupport.MinimalDeb("other", "9", "arm64")
+	p := newTestProvider()
+	store := newFakeStore()
+	remote := fx.remote()
+	remote.Patterns = []string{`^demo_.*_amd64\.deb$`}
+
+	if err := p.scan(context.Background(), remote, store); err != nil {
+		t.Fatalf("scan: %v", err)
+	}
+	rows, _ := store.ListDebMetadataEntries(context.Background(), "acme-deb")
+	if len(rows) != 1 || rows[0].Name != "demo" {
+		t.Fatalf("pattern filter failed, rows=%+v", rows)
+	}
+}

internal/provider/deb/syncer.go

@@ -0,0 +1,238 @@
+package deb
+
+import (
+	"context"
+	"crypto/rand"
+	"encoding/hex"
+	"log/slog"
+	"os"
+	"sync"
+	"time"
+
+	"golang.org/x/time/rate"
+
+	"git.unkin.net/unkin/artifactapi/internal/provider"
+	"git.unkin.net/unkin/artifactapi/pkg/models"
+)
+
+const (
+	syncLeaseDuration    = 15 * time.Minute
+	defaultSyncFreshness = 5 * time.Minute
+	jobQueueDepth        = 256
+)
+
+// SyncStore is the persistence surface the deb syncer needs: the metadata cache
+// it primes plus the shared sync-state coordination (remote enumeration and the
+// per-remote lease). *database.DB satisfies it.
+type SyncStore interface {
+	provider.RemoteMetadataStore
+	ListGitHubDebRemotes(ctx context.Context) ([]models.Remote, error)
+	ClaimGitHubDebSyncLease(ctx context.Context, remoteName, owner string, freshness, lease time.Duration) (claimed bool, etag string, err error)
+	ReleaseGitHubDebSyncLease(ctx context.Context, remoteName, owner, etag string, syncedAt time.Time) error
+}
+
+// SyncConfig tunes the shared syncer. Zero values fall back to safe defaults.
+type SyncConfig struct {
+	RatePerSec   float64
+	Burst        int
+	Workers      int
+	PollInterval time.Duration
+}
+
+type syncJob struct {
+	remote models.Remote
+	prime  bool
+}
+
+// Syncer is the single per-process background worker that keeps every github_deb
+// remote's derived metadata fresh. It owns a deduped work queue, a pool of
+// workers, and a global token-bucket rate limiter shared across all remotes and
+// bound onto the github_deb provider. Periodic checks are gated by a shared DB
+// lease so, across replicas, only one performs each scan.
+type Syncer struct {
+	store   SyncStore
+	prov    *GitHubProvider
+	limiter *rate.Limiter
+	cfg     SyncConfig
+	owner   string
+
+	jobs   chan syncJob
+	mu     sync.Mutex
+	active map[string]bool
+}
+
+// NewSyncer builds the syncer bound to the process-wide github_deb provider
+// singleton. Call Run to start it.
+func NewSyncer(store SyncStore, cfg SyncConfig) *Syncer {
+	return newSyncer(store, gitHubProvider, cfg)
+}
+
+func newSyncer(store SyncStore, prov *GitHubProvider, cfg SyncConfig) *Syncer {
+	if cfg.RatePerSec <= 0 {
+		cfg.RatePerSec = 1
+	}
+	if cfg.Burst <= 0 {
+		cfg.Burst = 5
+	}
+	if cfg.Workers <= 0 {
+		cfg.Workers = 3
+	}
+	if cfg.PollInterval <= 0 {
+		cfg.PollInterval = 60 * time.Second
+	}
+
+	lim := rate.NewLimiter(rate.Limit(cfg.RatePerSec), cfg.Burst)
+	s := &Syncer{
+		store:   store,
+		prov:    prov,
+		limiter: lim,
+		cfg:     cfg,
+		owner:   leaseOwner(),
+		jobs:    make(chan syncJob, jobQueueDepth),
+		active:  map[string]bool{},
+	}
+	prov.limiter = lim
+	prov.syncer = s
+	return s
+}
+
+// Run starts the worker pool and the periodic scheduler and blocks until ctx is
+// canceled, at which point it drains in-flight scans and returns.
+func (s *Syncer) Run(ctx context.Context) {
+	slog.Info("github_deb syncer started",
+		"rate_per_sec", s.cfg.RatePerSec, "burst", s.cfg.Burst,
+		"workers", s.cfg.Workers, "poll_interval", s.cfg.PollInterval, "owner", s.owner)
+
+	var wg sync.WaitGroup
+	for i := 0; i < s.cfg.Workers; i++ {
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+			s.worker(ctx)
+		}()
+	}
+
+	ticker := time.NewTicker(s.cfg.PollInterval)
+	defer ticker.Stop()
+
+	s.schedule(ctx)
+	for {
+		select {
+		case <-ctx.Done():
+			wg.Wait()
+			slog.Info("github_deb syncer stopped")
+			return
+		case <-ticker.C:
+			s.schedule(ctx)
+		}
+	}
+}
+
+// schedule enqueues a periodic check for every github_deb remote. The DB lease
+// enforces the per-remote mutable_ttl cadence and cross-replica coordination.
+func (s *Syncer) schedule(ctx context.Context) {
+	remotes, err := s.store.ListGitHubDebRemotes(ctx)
+	if err != nil {
+		slog.Error("github_deb syncer: list remotes", "error", err)
+		return
+	}
+	for _, r := range remotes {
+		s.enqueue(r, false)
+	}
+}
+
+// EnqueuePrime queues an immediate background prime for a freshly created remote.
+func (s *Syncer) EnqueuePrime(remote models.Remote) {
+	if s == nil {
+		return
+	}
+	s.enqueue(remote, true)
+}
+
+// enqueue adds a job unless the remote is already queued or in-flight, coalescing
+// duplicate requests down to one scan. It never blocks.
+func (s *Syncer) enqueue(remote models.Remote, prime bool) {
+	s.mu.Lock()
+	if s.active[remote.Name] {
+		s.mu.Unlock()
+		return
+	}
+	s.active[remote.Name] = true
+	s.mu.Unlock()
+
+	select {
+	case s.jobs <- syncJob{remote: remote, prime: prime}:
+	default:
+		s.mu.Lock()
+		delete(s.active, remote.Name)
+		s.mu.Unlock()
+	}
+}
+
+func (s *Syncer) worker(ctx context.Context) {
+	for {
+		select {
+		case <-ctx.Done():
+			return
+		case job := <-s.jobs:
+			s.process(ctx, job)
+		}
+	}
+}
+
+// process claims the shared lease and, if won, runs an incremental scan. Losing
+// the claim (another replica scanning, or not yet due) is a no-op.
+func (s *Syncer) process(ctx context.Context, job syncJob) {
+	defer func() {
+		s.mu.Lock()
+		delete(s.active, job.remote.Name)
+		s.mu.Unlock()
+	}()
+
+	freshness := time.Duration(job.remote.MutableTTL) * time.Second
+	if freshness <= 0 {
+		freshness = defaultSyncFreshness
+	}
+	if job.prime {
+		freshness = 0
+	}
+
+	claimed, etag, err := s.store.ClaimGitHubDebSyncLease(ctx, job.remote.Name, s.owner, freshness, syncLeaseDuration)
+	if err != nil {
+		slog.Error("github_deb syncer: claim lease", "remote", job.remote.Name, "error", err)
+		return
+	}
+	if !claimed {
+		return
+	}
+
+	scanCtx, cancel := context.WithTimeout(ctx, s.prov.scanTimeout)
+	defer cancel()
+
+	newEtag, changed, scanErr := s.prov.scanWithState(scanCtx, job.remote, s.store, etag)
+	releaseEtag := etag
+	if scanErr == nil {
+		releaseEtag = newEtag
+	} else {
+		slog.Error("github_deb syncer: scan failed", "remote", job.remote.Name, "error", scanErr)
+	}
+
+	relCtx, relCancel := context.WithTimeout(context.WithoutCancel(ctx), 10*time.Second)
+	defer relCancel()
+	if err := s.store.ReleaseGitHubDebSyncLease(relCtx, job.remote.Name, s.owner, releaseEtag, time.Now()); err != nil {
+		slog.Warn("github_deb syncer: release lease", "remote", job.remote.Name, "error", err)
+	}
+
+	if scanErr == nil && changed {
+		slog.Info("github_deb syncer: refreshed", "remote", job.remote.Name, "prime", job.prime)
+	}
+}
+
+// leaseOwner is a per-replica identity for the lease: hostname plus a random
+// suffix so restarts and colocated replicas never collide.
+func leaseOwner() string {
+	host, _ := os.Hostname()
+	var b [6]byte
+	_, _ = rand.Read(b[:])
+	return host + "-" + hex.EncodeToString(b[:])
+}

internal/provider/deb/syncer_test.go

@@ -0,0 +1,300 @@
+package deb
+
+import (
+	"context"
+	"net/http"
+	"net/http/httptest"
+	"sync"
+	"testing"
+	"time"
+
+	"golang.org/x/time/rate"
+
+	"git.unkin.net/unkin/artifactapi/internal/provider"
+	"git.unkin.net/unkin/artifactapi/internal/testsupport"
+	"git.unkin.net/unkin/artifactapi/pkg/models"
+)
+
+// fakeSyncStore is an in-memory SyncStore: the metadata cache (via the embedded
+// fakeStore) plus the shared sync-state lease, whose claim mirrors the atomic
+// semantics of the real SQL (recency gate AND no live lease).
+type fakeSyncStore struct {
+	*fakeStore
+
+	mu         sync.Mutex
+	remotes    []models.Remote
+	leaseOwner map[string]string
+	leaseExp   map[string]time.Time
+	lastSynced map[string]time.Time
+	etags      map[string]string
+}
+
+func newFakeSyncStore() *fakeSyncStore {
+	return &fakeSyncStore{
+		fakeStore:  newFakeStore(),
+		leaseOwner: map[string]string{},
+		leaseExp:   map[string]time.Time{},
+		lastSynced: map[string]time.Time{},
+		etags:      map[string]string{},
+	}
+}
+
+func (f *fakeSyncStore) ListGitHubDebRemotes(_ context.Context) ([]models.Remote, error) {
+	f.mu.Lock()
+	defer f.mu.Unlock()
+	return append([]models.Remote(nil), f.remotes...), nil
+}
+
+func (f *fakeSyncStore) ClaimGitHubDebSyncLease(_ context.Context, name, owner string, freshness, lease time.Duration) (bool, string, error) {
+	f.mu.Lock()
+	defer f.mu.Unlock()
+	now := time.Now()
+	ls, hasLS := f.lastSynced[name]
+	exp, hasExp := f.leaseExp[name]
+	freshOK := !hasLS || now.Sub(ls) >= freshness
+	leaseOK := !hasExp || exp.Before(now)
+	if freshOK && leaseOK {
+		f.leaseOwner[name] = owner
+		f.leaseExp[name] = now.Add(lease)
+		return true, f.etags[name], nil
+	}
+	return false, "", nil
+}
+
+func (f *fakeSyncStore) ReleaseGitHubDebSyncLease(_ context.Context, name, owner, etag string, syncedAt time.Time) error {
+	f.mu.Lock()
+	defer f.mu.Unlock()
+	if f.leaseOwner[name] != owner {
+		return nil
+	}
+	f.lastSynced[name] = syncedAt
+	f.etags[name] = etag
+	delete(f.leaseOwner, name)
+	delete(f.leaseExp, name)
+	return nil
+}
+
+func testSyncConfig() SyncConfig {
+	return SyncConfig{RatePerSec: 1000, Burst: 100, Workers: 1, PollInterval: time.Hour}
+}
+
+// (a) A 304 conditional response must derive nothing: no asset fetches and
+// changed=false, so an unchanged repo is nearly free.
+func TestSyncerConditionalNotModifiedSkipsDerive(t *testing.T) {
+	fx := newGitHubFixture(t, true)
+	fx.etag = `"v1"`
+	p := newTestProvider()
+	store := newFakeStore()
+	remote := fx.remote()
+
+	etag1, changed, err := p.scanWithState(context.Background(), remote, store, "")
+	if err != nil {
+		t.Fatalf("first scan: %v", err)
+	}
+	if !changed || etag1 != `"v1"` {
+		t.Fatalf("first scan changed=%v etag=%q, want true and \"v1\"", changed, etag1)
+	}
+	priorRange := fx.rangeHit["demo_1.2-3_amd64.deb"]
+	if priorRange == 0 {
+		t.Fatal("first scan should have fetched the asset control")
+	}
+
+	etag2, changed2, err := p.scanWithState(context.Background(), remote, store, etag1)
+	if err != nil {
+		t.Fatalf("second scan: %v", err)
+	}
+	if changed2 {
+		t.Fatal("304 scan must report changed=false")
+	}
+	if etag2 != etag1 {
+		t.Fatalf("etag changed across 304: %q -> %q", etag1, etag2)
+	}
+	if fx.notModHit != 1 {
+		t.Fatalf("want exactly one 304 releases response, got %d", fx.notModHit)
+	}
+	if got := fx.rangeHit["demo_1.2-3_amd64.deb"]; got != priorRange {
+		t.Fatalf("304 scan re-fetched asset control: %d -> %d", priorRange, got)
+	}
+}
+
+// (b) On a real change, only the newly added asset is derived.
+func TestSyncerIncrementalDerivesOnlyNewAsset(t *testing.T) {
+	fx := newGitHubFixture(t, true)
+	fx.etag = `"v1"`
+	p := newTestProvider()
+	store := newFakeStore()
+	remote := fx.remote()
+
+	if _, _, err := p.scanWithState(context.Background(), remote, store, ""); err != nil {
+		t.Fatalf("first scan: %v", err)
+	}
+	demoRange := fx.rangeHit["demo_1.2-3_amd64.deb"]
+
+	fx.debBytes["other_9_arm64.deb"] = testsupport.MinimalDeb("other", "9", "arm64")
+	fx.etag = `"v2"`
+
+	if _, changed, err := p.scanWithState(context.Background(), remote, store, `"v1"`); err != nil || !changed {
+		t.Fatalf("second scan changed=%v err=%v", changed, err)
+	}
+
+	rows, _ := store.ListDebMetadataEntries(context.Background(), remote.Name)
+	if len(rows) != 2 {
+		t.Fatalf("want 2 cached rows after incremental derive, got %d", len(rows))
+	}
+	if got := fx.rangeHit["demo_1.2-3_amd64.deb"]; got != demoRange {
+		t.Fatalf("already-cached asset was re-fetched: %d -> %d", demoRange, got)
+	}
+	if fx.rangeHit["other_9_arm64.deb"] == 0 {
+		t.Fatal("newly added asset was not derived")
+	}
+}
+
+// (c) The shared limiter caps the request rate.
+func TestRateLimiterCapsRequestRate(t *testing.T) {
+	fx := newGitHubFixture(t, true)
+	p := newTestProvider()
+	p.limiter = rate.NewLimiter(rate.Every(120*time.Millisecond), 1)
+	remote := fx.remote()
+
+	start := time.Now()
+	for i := 0; i < 3; i++ {
+		if _, _, _, err := p.fetchReleases(context.Background(), remote, ""); err != nil {
+			t.Fatalf("fetchReleases %d: %v", i, err)
+		}
+	}
+	if elapsed := time.Since(start); elapsed < 200*time.Millisecond {
+		t.Fatalf("rate limiter did not throttle: 3 calls took %v, want >= 200ms", elapsed)
+	}
+}
+
+// (d) Concurrent enqueues for the same remote coalesce to a single queued job.
+func TestSyncerEnqueueDedup(t *testing.T) {
+	store := newFakeSyncStore()
+	p := newTestProvider()
+	s := newSyncer(store, p, testSyncConfig())
+	remote := models.Remote{Name: "acme-deb", PackageType: models.PackageGitHubDeb, MutableTTL: 3600}
+
+	var wg sync.WaitGroup
+	for i := 0; i < 10; i++ {
+		wg.Add(1)
+		go func() { defer wg.Done(); s.enqueue(remote, false) }()
+	}
+	wg.Wait()
+
+	if got := len(s.jobs); got != 1 {
+		t.Fatalf("want exactly 1 coalesced job, got %d", got)
+	}
+}
+
+// (e) Prime-on-create enqueues a prime job.
+func TestSyncerEnqueuePrime(t *testing.T) {
+	store := newFakeSyncStore()
+	p := newTestProvider()
+	s := newSyncer(store, p, testSyncConfig())
+	remote := models.Remote{Name: "acme-deb", PackageType: models.PackageGitHubDeb, MutableTTL: 3600}
+
+	s.EnqueuePrime(remote)
+	select {
+	case job := <-s.jobs:
+		if !job.prime || job.remote.Name != "acme-deb" {
+			t.Fatalf("bad prime job: %+v", job)
+		}
+	default:
+		t.Fatal("EnqueuePrime did not enqueue a job")
+	}
+}
+
+// (f) A held lease prevents a second replica from scanning.
+func TestSyncerLeasePreventsSecondReplica(t *testing.T) {
+	fx := newGitHubFixture(t, true)
+	fx.etag = `"v1"`
+	store := newFakeSyncStore()
+	p := newTestProvider()
+	s := newSyncer(store, p, testSyncConfig())
+	remote := fx.remote()
+
+	claimed, _, err := store.ClaimGitHubDebSyncLease(context.Background(), remote.Name, "replica-1", time.Duration(remote.MutableTTL)*time.Second, syncLeaseDuration)
+	if err != nil || !claimed {
+		t.Fatalf("replica-1 claim: claimed=%v err=%v", claimed, err)
+	}
+
+	s.process(context.Background(), syncJob{remote: remote})
+
+	if fx.releasesHit != 0 {
+		t.Fatalf("second replica scanned while lease held: %d releases calls", fx.releasesHit)
+	}
+	if rows, _ := store.ListDebMetadataEntries(context.Background(), remote.Name); len(rows) != 0 {
+		t.Fatalf("second replica derived metadata while lease held: %d rows", len(rows))
+	}
+}
+
+// With the syncer wired and the cache empty, an index request enqueues a prime
+// and returns a retryable 503 when it has not landed within the cold wait.
+func TestServeRemoteColdStartReturns503(t *testing.T) {
+	fx := newGitHubFixture(t, true)
+	store := newFakeSyncStore()
+	p := newTestProvider()
+	p.coldWait = 300 * time.Millisecond
+	_ = newSyncer(store, p, testSyncConfig()) // binds p.syncer, but no workers running
+	remote := fx.remote()
+
+	rec := httptest.NewRecorder()
+	req := httptest.NewRequest(http.MethodGet, "/api/v1/remote/acme-deb/Packages", nil)
+	if !p.ServeRemote(rec, req, remote, "Packages", "https://x", store) {
+		t.Fatal("ServeRemote did not handle Packages")
+	}
+	if rec.Code != http.StatusServiceUnavailable {
+		t.Fatalf("cold empty cache must return 503, got %d", rec.Code)
+	}
+	if rec.Header().Get("Retry-After") == "" {
+		t.Fatal("503 should carry Retry-After")
+	}
+	if got := len(p.syncer.jobs); got != 1 {
+		t.Fatalf("cold start did not enqueue a prime, jobs=%d", got)
+	}
+}
+
+// With the cache warm, the same request serves the index immediately (no 503).
+func TestServeRemoteWarmCacheServesImmediately(t *testing.T) {
+	fx := newGitHubFixture(t, true)
+	store := newFakeSyncStore()
+	p := newTestProvider()
+	_ = newSyncer(store, p, testSyncConfig())
+	remote := fx.remote()
+
+	if err := p.scan(context.Background(), remote, store); err != nil {
+		t.Fatalf("warm scan: %v", err)
+	}
+	rec := httptest.NewRecorder()
+	req := httptest.NewRequest(http.MethodGet, "/api/v1/remote/acme-deb/Packages", nil)
+	if !p.ServeRemote(rec, req, remote, "Packages", "https://x", store) {
+		t.Fatal("ServeRemote did not handle Packages")
+	}
+	if rec.Code != http.StatusOK {
+		t.Fatalf("warm cache must serve 200, got %d body=%s", rec.Code, rec.Body.String())
+	}
+}
+
+// A prime job (freshness 0) runs even right after a sync; a periodic job at the
+// same moment is gated by the recency window.
+func TestSyncerPrimeBypassesRecencyPeriodicDoesNot(t *testing.T) {
+	fx := newGitHubFixture(t, true)
+	fx.etag = `"v1"`
+	store := newFakeSyncStore()
+	p := newTestProvider()
+	s := newSyncer(store, p, testSyncConfig())
+	remote := fx.remote()
+
+	var _ provider.RemoteMetadataStore = store
+
+	s.process(context.Background(), syncJob{remote: remote, prime: true})
+	if rows, _ := store.ListDebMetadataEntries(context.Background(), remote.Name); len(rows) != 1 {
+		t.Fatalf("prime did not derive: %d rows", len(rows))
+	}
+	releasesAfterPrime := fx.releasesHit
+
+	s.process(context.Background(), syncJob{remote: remote, prime: false})
+	if fx.releasesHit != releasesAfterPrime {
+		t.Fatalf("periodic scan ran inside recency window: %d -> %d releases calls", releasesAfterPrime, fx.releasesHit)
+	}
+}

internal/provider/generic/generic.go

@@ -4,9 +4,11 @@ import (
 	"context"
 	"encoding/base64"
 	"net/http"
+	"net/url"
 	"path"
 	"strings"
 
+	"git.unkin.net/unkin/artifactapi/internal/githubauth"
 	"git.unkin.net/unkin/artifactapi/internal/provider"
 	"git.unkin.net/unkin/artifactapi/pkg/models"
 )
@@ -59,10 +61,42 @@ func (p *Provider) RewriteResponse(_ []byte, _ models.Remote, _ string) ([]byte,
 	return nil, nil
 }
 
-func (p *Provider) AuthHeaders(_ context.Context, remote models.Remote) (http.Header, error) {
+// AuthHeaders authenticates outbound requests. A per-remote username/password
+// (Basic auth) takes precedence. Otherwise, when the remote points at a GitHub
+// host (e.g. a releases_remote proxying private release assets), the process-wide
+// GitHub credential is attached as a bearer token so private downloads work.
+func (p *Provider) AuthHeaders(ctx context.Context, remote models.Remote) (http.Header, error) {
 	h := http.Header{}
 	if remote.Username != "" {
 		h.Set("Authorization", "Basic "+base64.StdEncoding.EncodeToString([]byte(remote.Username+":"+remote.Password)))
+		return h, nil
+	}
+	if isGitHubHost(remote.BaseURL) {
+		if c := githubauth.Server(); c != nil {
+			tok, err := c.Token(ctx)
+			if err != nil {
+				return nil, err
+			}
+			if tok != "" {
+				h.Set("Authorization", "Bearer "+tok)
+			}
+		}
 	}
 	return h, nil
 }
+
+// isGitHubHost reports whether rawURL targets a GitHub API/download host that
+// accepts the server credential. objects.githubusercontent.com is deliberately
+// excluded: release-asset downloads 302-redirect there with a pre-signed URL
+// that must not carry an Authorization header.
+func isGitHubHost(rawURL string) bool {
+	u, err := url.Parse(rawURL)
+	if err != nil {
+		return false
+	}
+	switch strings.ToLower(u.Hostname()) {
+	case "github.com", "www.github.com", "api.github.com", "codeload.github.com", "uploads.github.com":
+		return true
+	}
+	return false
+}

internal/provider/generic/generic_test.go

@@ -4,11 +4,56 @@ import (
 	"context"
 	"testing"
 
+	"git.unkin.net/unkin/artifactapi/internal/githubauth"
 	"git.unkin.net/unkin/artifactapi/internal/provider"
 	"git.unkin.net/unkin/artifactapi/internal/provider/generic"
 	"git.unkin.net/unkin/artifactapi/pkg/models"
 )
 
+type staticCred string
+
+func (s staticCred) Token(context.Context) (string, error) { return string(s), nil }
+
+func TestProvider_AuthHeaders_GitHubServerCredential(t *testing.T) {
+	githubauth.SetServer(staticCred("ghs_server"))
+	t.Cleanup(func() { githubauth.SetServer(nil) })
+
+	p := &generic.Provider{}
+	h, err := p.AuthHeaders(context.Background(), models.Remote{BaseURL: "https://github.com"})
+	if err != nil {
+		t.Fatalf("auth headers: %v", err)
+	}
+	if h.Get("Authorization") != "Bearer ghs_server" {
+		t.Fatalf("Authorization = %q, want Bearer ghs_server", h.Get("Authorization"))
+	}
+}
+
+func TestProvider_AuthHeaders_NonGitHubHostNoServerCredential(t *testing.T) {
+	githubauth.SetServer(staticCred("ghs_server"))
+	t.Cleanup(func() { githubauth.SetServer(nil) })
+
+	p := &generic.Provider{}
+	h, _ := p.AuthHeaders(context.Background(), models.Remote{BaseURL: "https://example.com/downloads"})
+	if h.Get("Authorization") != "" {
+		t.Fatalf("server credential must not be sent to non-github host, got %q", h.Get("Authorization"))
+	}
+}
+
+func TestProvider_AuthHeaders_PerRemoteOverridesServerCredential(t *testing.T) {
+	githubauth.SetServer(staticCred("ghs_server"))
+	t.Cleanup(func() { githubauth.SetServer(nil) })
+
+	p := &generic.Provider{}
+	h, _ := p.AuthHeaders(context.Background(), models.Remote{
+		BaseURL:  "https://github.com",
+		Username: "user",
+		Password: "pass",
+	})
+	if got := h.Get("Authorization"); got != "Basic dXNlcjpwYXNz" {
+		t.Fatalf("per-remote Basic auth must win, got %q", got)
+	}
+}
+
 func TestProvider_Type(t *testing.T) {
 	p := &generic.Provider{}
 	if p.Type() != models.PackageGeneric {

internal/provider/provider.go

@@ -61,6 +61,7 @@ type PostDeleteHook interface {
 
 type MetadataStore interface {
 	InsertRPMMetadata(ctx context.Context, meta *RPMMetadata) error
+	InsertDebMetadata(ctx context.Context, meta *DebMetadata) error
 }
 
 // RemoteServer lets a remote provider fully answer a request itself instead of
@@ -83,12 +84,37 @@ type RemoteMetadataStore interface {
 
 type MetadataDeleter interface {
 	DeleteRPMMetadata(ctx context.Context, repoName, filePath string) error
+	DeleteDebMetadata(ctx context.Context, repoName, filePath string) error
 }
 
 type RPMMetadataReader interface {
 	ListRPMMetadataEntries(ctx context.Context, repoName string) ([]RPMMetadata, error)
 }
 
+// DebMetadataReader is the read surface the deb LocalIndexer needs to
+// regenerate a flat apt repository (Packages/Release) from stored rows.
+// *database.DB satisfies it; ServeLocalIndex type-asserts the FileStore to it,
+// mirroring how the rpm provider reaches its RPMMetadataReader.
+type DebMetadataReader interface {
+	ListDebMetadataEntries(ctx context.Context, repoName string) ([]DebMetadata, error)
+}
+
+// DebMetadata is the derived per-package metadata for a Debian .deb, carrying
+// the full raw control stanza so the Packages index can be regenerated
+// faithfully alongside the computed size/md5/sha256 apt requires.
+type DebMetadata struct {
+	RepoName     string
+	FilePath     string
+	ContentHash  string
+	Name         string
+	Version      string
+	Architecture string
+	Control      string
+	Size         int64
+	MD5          string
+	SHA256       string
+}
+
 type RPMMetadata struct {
 	RepoName      string
 	FilePath      string

internal/provider/rpm/github.go

@@ -20,6 +20,7 @@ import (
 	rpmlib "github.com/cavaliergopher/rpm"
 	"golang.org/x/time/rate"
 
+	"git.unkin.net/unkin/artifactapi/internal/githubauth"
 	"git.unkin.net/unkin/artifactapi/internal/provider"
 	"git.unkin.net/unkin/artifactapi/pkg/models"
 )
@@ -76,6 +77,10 @@ type GitHubProvider struct {
 	// the shared background work queue instead of an inline per-replica scan.
 	syncer *Syncer
 
+	// serverCred overrides the process-wide GitHub credential for this provider
+	// instance. nil falls back to githubauth.Server(); set directly in tests.
+	serverCred githubauth.Credential
+
 	mu       sync.Mutex
 	scanning map[string]bool
 	lastScan map[string]time.Time
@@ -136,8 +141,8 @@ func (p *GitHubProvider) RewriteResponse(_ []byte, _ models.Remote, _ string) ([
 	return nil, nil
 }
 
-func (p *GitHubProvider) AuthHeaders(_ context.Context, remote models.Remote) (http.Header, error) {
-	return githubHeaders(remote, false), nil
+func (p *GitHubProvider) AuthHeaders(ctx context.Context, remote models.Remote) (http.Header, error) {
+	return p.githubHeaders(ctx, remote, false)
 }
 
 // ServeRemote answers a request against a github_rpm remote. It refreshes the
@@ -414,7 +419,11 @@ func (p *GitHubProvider) fetchReleases(ctx context.Context, remote models.Remote
 		if err != nil {
 			return nil, "", false, err
 		}
-		copyHeaders(req, githubHeaders(remote, true))
+		hdr, err := p.githubHeaders(ctx, remote, true)
+		if err != nil {
+			return nil, "", false, err
+		}
+		copyHeaders(req, hdr)
 		if page == 1 && etag != "" {
 			req.Header.Set("If-None-Match", etag)
 		}
@@ -571,7 +580,11 @@ func (p *GitHubProvider) rangeGet(ctx context.Context, remote models.Remote, dow
 	if err != nil {
 		return nil, false, err
 	}
-	copyHeaders(req, githubHeaders(remote, false))
+	hdr, err := p.githubHeaders(ctx, remote, false)
+	if err != nil {
+		return nil, false, err
+	}
+	copyHeaders(req, hdr)
 	req.Header.Set("Range", fmt.Sprintf("bytes=0-%d", n-1))
 
 	if err := p.limiterWait(ctx); err != nil {
@@ -599,7 +612,11 @@ func (p *GitHubProvider) computeSHA256(ctx context.Context, remote models.Remote
 	if err != nil {
 		return "", err
 	}
-	copyHeaders(req, githubHeaders(remote, false))
+	hdr, err := p.githubHeaders(ctx, remote, false)
+	if err != nil {
+		return "", err
+	}
+	copyHeaders(req, hdr)
 
 	if err := p.limiterWait(ctx); err != nil {
 		return "", err
@@ -638,23 +655,48 @@ func sha256FromDigest(digest string) (string, bool) {
 	return "", false
 }
 
-func githubHeaders(remote models.Remote, api bool) http.Header {
+// githubHeaders builds the outbound headers for a GitHub request, attaching a
+// bearer credential when one is available. A per-remote credential wins; absent
+// that, the process-wide server credential is used; absent both, the request is
+// unauthenticated (anonymous, subject to the 60/hr cap).
+func (p *GitHubProvider) githubHeaders(ctx context.Context, remote models.Remote, api bool) (http.Header, error) {
 	h := http.Header{}
 	if api {
 		h.Set("Accept", "application/vnd.github+json")
 		h.Set("X-GitHub-Api-Version", "2022-11-28")
 	}
-	if tok := githubToken(remote); tok != "" {
+	tok, err := p.githubToken(ctx, remote)
+	if err != nil {
+		return nil, err
+	}
+	if tok != "" {
 		h.Set("Authorization", "Bearer "+tok)
 	}
-	return h
+	return h, nil
 }
 
-func githubToken(remote models.Remote) string {
+// githubToken resolves the bearer token for a remote. Precedence: a per-remote
+// credential (password, then username) overrides the server credential.
+func (p *GitHubProvider) githubToken(ctx context.Context, remote models.Remote) (string, error) {
 	if remote.Password != "" {
-		return remote.Password
+		return remote.Password, nil
 	}
-	return remote.Username
+	if remote.Username != "" {
+		return remote.Username, nil
+	}
+	if c := p.serverCredential(); c != nil {
+		return c.Token(ctx)
+	}
+	return "", nil
+}
+
+// serverCredential returns this provider's server credential, defaulting to the
+// process-wide one installed at startup.
+func (p *GitHubProvider) serverCredential() githubauth.Credential {
+	if p.serverCred != nil {
+		return p.serverCred
+	}
+	return githubauth.Server()
 }
 
 func copyHeaders(req *http.Request, h http.Header) {

internal/provider/rpm/github_auth_test.go

@@ -0,0 +1,134 @@
+package rpm
+
+import (
+	"context"
+	"encoding/json"
+	"strings"
+	"testing"
+
+	"git.unkin.net/unkin/artifactapi/internal/githubauth"
+	"git.unkin.net/unkin/artifactapi/pkg/models"
+)
+
+// staticCred is a test Credential yielding a fixed token.
+type staticCred string
+
+func (s staticCred) Token(context.Context) (string, error) { return string(s), nil }
+
+func TestGitHubServerCredentialAttachedToReleasesAndAssets(t *testing.T) {
+	fx := newGitHubFixture(t, true)
+	p := newTestProvider()
+	p.serverCred = staticCred("ghp_server_secret")
+	store := newFakeStore()
+
+	if err := p.scan(context.Background(), fx.remote(), store); err != nil {
+		t.Fatalf("scan: %v", err)
+	}
+	if got := fx.releaseAuth; got != "Bearer ghp_server_secret" {
+		t.Fatalf("releases Authorization = %q, want Bearer ghp_server_secret", got)
+	}
+	if got := fx.assetAuth; got != "Bearer ghp_server_secret" {
+		t.Fatalf("asset Authorization = %q, want Bearer ghp_server_secret", got)
+	}
+}
+
+func TestGitHubPerRemoteCredentialOverridesServer(t *testing.T) {
+	fx := newGitHubFixture(t, true)
+	p := newTestProvider()
+	p.serverCred = staticCred("ghp_server_secret")
+	store := newFakeStore()
+
+	remote := fx.remote()
+	remote.Password = "ghp_remote_wins"
+
+	if err := p.scan(context.Background(), remote, store); err != nil {
+		t.Fatalf("scan: %v", err)
+	}
+	if got := fx.releaseAuth; got != "Bearer ghp_remote_wins" {
+		t.Fatalf("releases Authorization = %q, want per-remote token to win", got)
+	}
+	if got := fx.assetAuth; got != "Bearer ghp_remote_wins" {
+		t.Fatalf("asset Authorization = %q, want per-remote token to win", got)
+	}
+}
+
+func TestGitHubNoCredentialSendsNoAuthHeader(t *testing.T) {
+	fx := newGitHubFixture(t, true)
+	p := newTestProvider() // serverCred nil, package Server() unset in unit tests
+	store := newFakeStore()
+
+	if err := p.scan(context.Background(), fx.remote(), store); err != nil {
+		t.Fatalf("scan: %v", err)
+	}
+	if fx.releaseAuth != "" {
+		t.Fatalf("expected no Authorization header, got %q", fx.releaseAuth)
+	}
+	if fx.assetAuth != "" {
+		t.Fatalf("expected no asset Authorization header, got %q", fx.assetAuth)
+	}
+	// Requests still succeed anonymously.
+	if rows, _ := store.ListRPMMetadataEntries(context.Background(), "acme-rpm"); len(rows) != 1 {
+		t.Fatalf("anonymous scan should still derive metadata, got %d rows", len(rows))
+	}
+}
+
+func TestGitHubETag304FlowWithAuth(t *testing.T) {
+	fx := newGitHubFixture(t, true)
+	fx.etag = `"v1"`
+	p := newTestProvider()
+	p.serverCred = staticCred("ghp_server_secret")
+	store := newFakeStore()
+
+	etag, changed, err := p.scanWithState(context.Background(), fx.remote(), store, "")
+	if err != nil {
+		t.Fatalf("first scan: %v", err)
+	}
+	if !changed || etag != `"v1"` {
+		t.Fatalf("first scan changed=%v etag=%q, want true and \"v1\"", changed, etag)
+	}
+
+	// Re-scan with the captured ETag: a 304 means no change and no asset fetch.
+	etag2, changed2, err := p.scanWithState(context.Background(), fx.remote(), store, etag)
+	if err != nil {
+		t.Fatalf("second scan: %v", err)
+	}
+	if changed2 {
+		t.Fatal("expected no change on 304")
+	}
+	if etag2 != `"v1"` {
+		t.Fatalf("etag = %q, want preserved \"v1\"", etag2)
+	}
+	if fx.notModHit != 1 {
+		t.Fatalf("expected exactly one 304 response, got %d", fx.notModHit)
+	}
+	// The conditional request still carried the credential.
+	if fx.releaseAuth != "Bearer ghp_server_secret" {
+		t.Fatalf("conditional request Authorization = %q, want the server credential", fx.releaseAuth)
+	}
+}
+
+// TestGitHubCredentialAbsentFromRemoteJSON asserts the server credential never
+// appears in a remote's serialized API representation, and per-remote secrets
+// stay redacted by the models.Remote json:"-" tags.
+func TestGitHubCredentialAbsentFromRemoteJSON(t *testing.T) {
+	githubauth.SetServer(staticCred("ghp_super_secret_server_token"))
+	t.Cleanup(func() { githubauth.SetServer(nil) })
+
+	remote := models.Remote{
+		Name:        "acme-rpm",
+		PackageType: models.PackageGitHubRPM,
+		BaseURL:     "https://api.github.com/repos/acme/tools",
+		Username:    "per_remote_user",
+		Password:    "per_remote_secret",
+	}
+	b, err := json.Marshal(remote)
+	if err != nil {
+		t.Fatalf("marshal remote: %v", err)
+	}
+	js := string(b)
+	for _, secret := range []string{"ghp_super_secret_server_token", "per_remote_secret", "per_remote_user"} {
+		if strings.Contains(js, secret) {
+			t.Fatalf("credential %q leaked into remote JSON: %s", secret, js)
+		}
+	}
+}

internal/provider/rpm/github_test.go

@@ -47,6 +47,9 @@ func (f *fakeStore) DeleteRPMMetadata(_ context.Context, _, filePath string) err
 	return nil
 }
 
+func (f *fakeStore) InsertDebMetadata(context.Context, *provider.DebMetadata) error { return nil }
+func (f *fakeStore) DeleteDebMetadata(context.Context, string, string) error        { return nil }
+
 func (f *fakeStore) ListRPMMetadataEntries(ctx context.Context, _ string) ([]provider.RPMMetadata, error) {
 	// Mirror pgx: a canceled/expired context fails the read. This is what
 	// poisons the repodata response if the read runs on the inbound request.
@@ -73,6 +76,8 @@ type githubFixture struct {
 	etag        string            // when set, served as ETag; matching If-None-Match yields 304
 	releasesHit int               // total releases-list requests (200 + 304)
 	notModHit   int               // releases-list requests answered 304
+	releaseAuth string            // Authorization header seen on the last releases request
+	assetAuth   string            // Authorization header seen on the last asset request
 	mu          sync.Mutex
 }
 
@@ -94,6 +99,7 @@ func newGitHubFixture(t *testing.T, withDigest bool) *githubFixture {
 		}
 		f.mu.Lock()
 		f.releasesHit++
+		f.releaseAuth = r.Header.Get("Authorization")
 		etag := f.etag
 		if etag != "" && r.Header.Get("If-None-Match") == etag {
 			f.notModHit++
@@ -130,6 +136,7 @@ func newGitHubFixture(t *testing.T, withDigest bool) *githubFixture {
 		}
 		rng := r.Header.Get("Range")
 		f.mu.Lock()
+		f.assetAuth = r.Header.Get("Authorization")
 		if rng != "" {
 			f.rangeHit[name]++
 		} else {

internal/provider/rpm/rpm_meta_test.go

@@ -28,6 +28,8 @@ func (f *fakeMetaStore) InsertRPMMetadata(_ context.Context, m *provider.RPMMeta
 	return nil
 }
 
+func (f *fakeMetaStore) InsertDebMetadata(context.Context, *provider.DebMetadata) error { return nil }
+
 type fakeRPMReader struct{ metas []provider.RPMMetadata }
 
 func (f fakeRPMReader) ListRPMMetadataEntries(_ context.Context, _ string) ([]provider.RPMMetadata, error) {

internal/server/server.go

@@ -19,7 +19,9 @@ import (
 	"git.unkin.net/unkin/artifactapi/internal/config"
 	"git.unkin.net/unkin/artifactapi/internal/database"
 	"git.unkin.net/unkin/artifactapi/internal/gc"
+	"git.unkin.net/unkin/artifactapi/internal/githubauth"
 	_ "git.unkin.net/unkin/artifactapi/internal/provider/alpine"
+	"git.unkin.net/unkin/artifactapi/internal/provider/deb"
 	_ "git.unkin.net/unkin/artifactapi/internal/provider/docker"
 	_ "git.unkin.net/unkin/artifactapi/internal/provider/generic"
 	_ "git.unkin.net/unkin/artifactapi/internal/provider/goproxy"
@@ -33,6 +35,7 @@ import (
 	"git.unkin.net/unkin/artifactapi/internal/storage"
 	"git.unkin.net/unkin/artifactapi/internal/tfsign"
 	"git.unkin.net/unkin/artifactapi/internal/virtual"
+	"git.unkin.net/unkin/artifactapi/pkg/models"
 )
 
 type Server struct {
@@ -48,6 +51,7 @@ type Server struct {
 	tfRegistry   *tfregistry.Handler
 	gc           *gc.Collector
 	syncer       *rpm.Syncer
+	debSyncer    *deb.Syncer
 }
 
 func New(cfg *config.Config, version string) (*Server, error) {
@@ -66,6 +70,25 @@ func New(cfg *config.Config, version string) (*Server, error) {
 		return nil, fmt.Errorf("s3: %w", err)
 	}
 
+	// Install the process-wide GitHub credential before any provider makes an
+	// outbound call. A misconfiguration (e.g. App id without a private key) fails
+	// closed here rather than silently falling back to anonymous. No credential
+	// configured is fine — requests stay anonymous.
+	ghCred, err := githubauth.New(githubauth.Options{
+		Token:          cfg.GitHubToken,
+		AppID:          cfg.GitHubAppID,
+		InstallationID: cfg.GitHubAppInstallationID,
+		PrivateKeyPEM:  cfg.GitHubAppPrivateKey,
+		PrivateKeyPath: cfg.GitHubAppPrivateKeyPath,
+	})
+	if err != nil {
+		return nil, fmt.Errorf("github auth: %w", err)
+	}
+	githubauth.SetServer(ghCred)
+	if ghCred != nil {
+		slog.Info("github machine credential configured")
+	}
+
 	engine := proxy.NewEngine(db, redis, s3)
 	localHandler := v2.NewLocalHandler(db, s3)
 	virtEngine := virtual.NewEngine(db, engine)
@@ -76,6 +99,12 @@ func New(cfg *config.Config, version string) (*Server, error) {
 		Workers:      cfg.GitHubSyncWorkers,
 		PollInterval: time.Duration(cfg.GitHubSyncPollInterval) * time.Second,
 	})
+	debSyncer := deb.NewSyncer(db, deb.SyncConfig{
+		RatePerSec:   cfg.GitHubSyncRatePerSec,
+		Burst:        cfg.GitHubSyncBurst,
+		Workers:      cfg.GitHubSyncWorkers,
+		PollInterval: time.Duration(cfg.GitHubSyncPollInterval) * time.Second,
+	})
 
 	// The terraform registry signs with a GPG key. A configured file wins (BYO
 	// key); otherwise artifactapi generates one on first start and persists it in
@@ -108,6 +137,7 @@ func New(cfg *config.Config, version string) (*Server, error) {
 		tfRegistry:   tfRegistry,
 		gc:           collector,
 		syncer:       syncer,
+		debSyncer:    debSyncer,
 	}
 
 	s.router = s.routes()
@@ -137,7 +167,10 @@ func (s *Server) routes() chi.Router {
 	r.Mount("/api/v1", proxyHandler.Routes())
 	r.Mount("/v2", proxyHandler.DockerV2Routes())
 
-	remotesHandler := v2.NewRemotesHandler(s.db, s.syncer)
+	remotesHandler := v2.NewRemotesHandler(s.db, map[models.PackageType]v2.Primer{
+		models.PackageGitHubRPM: s.syncer,
+		models.PackageGitHubDeb: s.debSyncer,
+	})
 	virtualsHandler := v2.NewVirtualsHandler(s.db)
 	healthHandler := v2.NewHealthHandler(s.db, s.cache, s.store)
 	statsHandler := v2.NewStatsHandler(s.db)
@@ -205,6 +238,7 @@ func (s *Server) newHTTPServer() *http.Server {
 func (s *Server) Run(ctx context.Context) error {
 	go s.gc.Run(ctx)
 	go s.syncer.Run(ctx)
+	go s.debSyncer.Run(ctx)
 
 	httpServer := s.newHTTPServer()
 
@@ -226,6 +260,7 @@ func (s *Server) Run(ctx context.Context) error {
 func (s *Server) RunOnListener(ctx context.Context, ln net.Listener) error {
 	go s.gc.Run(ctx)
 	go s.syncer.Run(ctx)
+	go s.debSyncer.Run(ctx)
 
 	httpServer := s.newHTTPServer()
 

internal/testsupport/deb.go

@@ -0,0 +1,61 @@
+package testsupport
+
+import (
+	"archive/tar"
+	"bytes"
+	"compress/gzip"
+	"fmt"
+)
+
+// MinimalDeb builds a valid-enough Debian package in pure Go (no committed
+// binary fixture, no dpkg-deb): an ar archive of debian-binary, a gzip
+// control.tar.gz carrying ./control, and an (empty) gzip data.tar.gz. It is the
+// deb analog of MinimalRPM and is parseable by the deb provider.
+func MinimalDeb(name, version, arch string) []byte {
+	control := fmt.Sprintf(
+		"Package: %s\nVersion: %s\nArchitecture: %s\nMaintainer: e2e <e2e@example.com>\n"+
+			"Section: utils\nPriority: optional\nDescription: minimal test package\n",
+		name, version, arch)
+
+	controlTarGz := gzipBytes(tarSingle("./control", []byte(control)))
+	dataTarGz := gzipBytes(tarEmpty())
+
+	var buf bytes.Buffer
+	buf.WriteString("!<arch>\n")
+	arWrite(&buf, "debian-binary", []byte("2.0\n"))
+	arWrite(&buf, "control.tar.gz", controlTarGz)
+	arWrite(&buf, "data.tar.gz", dataTarGz)
+	return buf.Bytes()
+}
+
+func arWrite(buf *bytes.Buffer, name string, data []byte) {
+	fmt.Fprintf(buf, "%-16s%-12s%-6s%-6s%-8s%-10d`\n", name, "0", "0", "0", "100644", len(data))
+	buf.Write(data)
+	if len(data)%2 == 1 {
+		buf.WriteByte('\n')
+	}
+}
+
+func tarSingle(name string, data []byte) []byte {
+	var buf bytes.Buffer
+	tw := tar.NewWriter(&buf)
+	tw.WriteHeader(&tar.Header{Name: name, Mode: 0o644, Size: int64(len(data)), Typeflag: tar.TypeReg})
+	tw.Write(data)
+	tw.Close()
+	return buf.Bytes()
+}
+
+func tarEmpty() []byte {
+	var buf bytes.Buffer
+	tw := tar.NewWriter(&buf)
+	tw.Close()
+	return buf.Bytes()
+}
+
+func gzipBytes(data []byte) []byte {
+	var buf bytes.Buffer
+	gz := gzip.NewWriter(&buf)
+	gz.Write(data)
+	gz.Close()
+	return buf.Bytes()
+}

pkg/models/package_type.go

@@ -11,11 +11,13 @@ const (
 	PackagePyPI      PackageType = "pypi"
 	PackageNPM       PackageType = "npm"
 	PackageRPM       PackageType = "rpm"
+	PackageDeb       PackageType = "deb"
 	PackageAlpine    PackageType = "alpine"
 	PackagePuppet    PackageType = "puppet"
 	PackageTerraform PackageType = "terraform"
 	PackageGoProxy   PackageType = "goproxy"
 	PackageGitHubRPM PackageType = "github_rpm"
+	PackageGitHubDeb PackageType = "github_deb"
 )
 
 var validPackageTypes = map[PackageType]bool{
@@ -25,11 +27,13 @@ var validPackageTypes = map[PackageType]bool{
 	PackagePyPI:      true,
 	PackageNPM:       true,
 	PackageRPM:       true,
+	PackageDeb:       true,
 	PackageAlpine:    true,
 	PackagePuppet:    true,
 	PackageTerraform: true,
 	PackageGoProxy:   true,
 	PackageGitHubRPM: true,
+	PackageGitHubDeb: true,
 }
 
 func (p PackageType) Valid() bool {

ui/src/components/UsageInstructions.tsx

@@ -208,6 +208,47 @@ go mod download`,
         },
       ];
 
+    case 'deb':
+      return isLocal
+        ? [
+            {
+              title: 'Add the apt repo (real apt repo, flat — Packages/Release auto-generated)',
+              language: 'bash',
+              code: `echo 'deb [trusted=yes] ${url}/api/v1/local/${name}/ ./' | sudo tee /etc/apt/sources.list.d/${name}.list
+sudo apt-get update
+sudo apt-get install <package>`,
+              note: '[trusted=yes]: artifactapi serves the flat repo unsigned (matches the rpm repo\'s gpgcheck=0). The `./` is the flat-repo suite — apt fetches Packages/Release from the repo root.',
+            },
+            {
+              title: 'Publish a .deb (index regenerates automatically)',
+              language: 'bash',
+              code: `curl -fsSL --upload-file ./my-package_1.0_amd64.deb \\
+  ${url}/api/v2/remotes/${name}/files/my-package_1.0_amd64.deb`,
+            },
+          ]
+        : [
+            {
+              title: 'Add the apt repo (caching proxy)',
+              language: 'bash',
+              code: `echo 'deb ${proxy} <suite> <component>' | sudo tee /etc/apt/sources.list.d/${name}.list
+sudo apt-get update
+sudo apt-get install <package>`,
+              note: "Signatures are verified against the upstream mirror's real signed Release through the proxy (no [trusted=yes] needed). Example suite/component: bookworm main.",
+            },
+          ];
+
+    case 'github_deb':
+      return [
+        {
+          title: 'Add the apt repo (metadata-only, from GitHub releases)',
+          language: 'bash',
+          code: `echo 'deb [trusted=yes] ${proxy}/ ./' | sudo tee /etc/apt/sources.list.d/${name}.list
+sudo apt-get update
+sudo apt-get install <package>`,
+          note: "The apt index is synthesized from the configured GitHub repo's release .deb assets; package downloads are redirected to the backing releases remote. Served unsigned, so [trusted=yes].",
+        },
+      ];
+
     case 'generic':
     default:
       return [