AGENTS.md

@@ -31,7 +31,7 @@ parsing, watch-state comparison, git worktree helpers).
 cmd/agentpr/main.go      # agentpr CLI (pr create / pr comment / whoami)
 cmd/watchpr/main.go      # watchpr CLI (poll + meaningful-change exit)
 cmd/agentws/main.go      # agentws CLI (new / list / rm / clean / token / credential)
-cmd/agentvault/main.go   # agentvault CLI (seed-outpost)
+cmd/agentvault/main.go   # agentvault CLI (seed-outpost / seed-oauth)
 internal/agent/          # shared plumbing:
   token.go               #   env config + in-process Gitea-token cache
   vault.go               #   AppRole login + read the gitea creds path
@@ -42,6 +42,7 @@ internal/agent/          # shared plumbing:
   vaultkv.go             #   AppRole-authenticated Vault client + KV-v2 read/write
   authentik.go           #   Authentik REST client (outpost search, token view_key)
   seedoutpost.go         #   seed-outpost flow (Authentik token -> Vault KV)
+  seedoauth.go           #   seed-oauth flow (oauth2-proxy credential set in Vault KV)
 go.mod                   # module git.unkin.net/unkin/agent-tools
 Makefile                 # build / test / lint / completions / rpm / version-bump
 packaging/nfpm.yaml      # nfpm spec (envsubst-templated) for the RPM (all binaries)
@@ -148,12 +149,37 @@ printed. Errors are wrapped per stage (login / read denied / outpost missing /
 view_key / write denied) via the `ErrVaultDenied`, `ErrVaultNotFound` and
 `ErrOutpostNotFound` sentinels.
 
+## agentvault seed-oauth
+
+`agentvault seed-oauth --path <kv/path> --client-id <id>` makes a KV-v2 path
+hold a complete oauth2-proxy credential set, in-process:
+
+1. AppRole login (shared `approleLogin`), then a KV-v2 read via
+   `ReadKVOptional` — a 404 or a deleted version means "empty", not an error,
+   so the first seed of a path works.
+2. Desired keys are computed over the existing map: `client_id` from the flag
+   (`kept`/`created`/`updated`), `client_secret` and `cookie_secret` generated
+   from 32 `crypto/rand` bytes only when absent or when `--rotate` is set
+   (`kept`/`created`/`rotated`). `cookie_secret` is base64url so it decodes to
+   exactly the 32 bytes oauth2-proxy demands; `client_secret` is standard
+   base64.
+3. Any other key on the path is carried through unchanged (`preserved`), which
+   is why the write goes through `WriteKVAny` rather than `WriteKV`.
+4. The write is skipped entirely when nothing changed; the command then prints
+   `version: unchanged`.
+
+Only key names, per-key actions and the new KV version are printed. Errors are
+wrapped per stage (login / read denied / write denied) via `ErrVaultDenied`.
+
 ## Gotchas
 
 - `watchpr` exits 0 with no output changes on `--once` (just prints state).
 - The token cache is process-wide (`sync.Once`); tests call the unexported
   `fetchGiteaToken` to avoid it.
 - `agentvault` never puts a secret in an error string: Vault decode failures and
-  Authentik `view_key` responses are reported without their bodies.
+  Authentik `view_key` responses are reported without their bodies, and
+  `seed-oauth` reports key names only.
+- `--rotate` regenerates the `client_secret` too, which then no longer matches
+  the IdP provider unless that is rotated alongside.
 - CI "combined status" comes from `/commits/{sha}/status`; an empty head SHA
   yields an empty state without an API call.

README.md

@@ -162,6 +162,42 @@ Errors name the failing stage: AppRole login, KV read denied (policy not
 applied), outpost not found (terraform not applied), `view_key` failure, or KV
 write denied.
 
+### seed-oauth
+
+Make a Vault KV-v2 path hold a complete oauth2-proxy credential set. It is a
+read-modify-write: `client_id` is set from the flag, `client_secret` and
+`cookie_secret` are generated (32 bytes from `crypto/rand`) only when missing,
+every other key on the path is written back untouched, and nothing is written
+at all when the secret is already correct. `cookie_secret` is base64url so it
+decodes to exactly the 32 bytes oauth2-proxy requires.
+
+```bash
+agentvault seed-oauth \
+  --path kubernetes/namespace/repospawner/default/oauth-credentials \
+  --client-id 4f1c…
+```
+
+```
+path:          kv/kubernetes/namespace/repospawner/default/oauth-credentials
+keys:          client_id, client_secret, cookie_secret
+  client_id:     created
+  client_secret: kept
+  cookie_secret: created
+version:       4
+```
+
+That is the common case: the provider's `client_secret` already lives on the
+path, so only the missing keys are added. A run with nothing to do prints
+`version:       unchanged` and issues no write.
+
+Flags: `--path` and `--client-id` are required; `--kv-mount` (default `kv`) and
+`--rotate` override the rest. `--rotate` regenerates both secrets — only use it
+when the IdP provider's secret is being rotated alongside, since a rotated
+`client_secret` no longer matches the provider.
+
+Errors name the failing stage: AppRole login, KV read denied, or KV write
+denied. Only key names, actions and the KV version are printed.
+
 ## Build & package
 
 ```bash

cmd/agentvault/main.go

@@ -3,11 +3,13 @@
 // with the same Vault AppRole as agentpr (role_id only, no secret_id).
 //
 //	agentvault seed-outpost --outpost <name> --dest-path <kv/path>
+//	agentvault seed-oauth --path <kv/path> --client-id <id>
 package main
 
 import (
 	"fmt"
 	"os"
+	"strings"
 
 	"git.unkin.net/unkin/agent-tools/internal/agent"
 
@@ -33,7 +35,7 @@ func newRootCmd() *cobra.Command {
 		SilenceUsage: true,
 	}
 	root.SetVersionTemplate("{{.Version}}\n")
-	root.AddCommand(newSeedOutpostCmd(), newVersionCmd())
+	root.AddCommand(newSeedOutpostCmd(), newSeedOAuthCmd(), newVersionCmd())
 	return root
 }
 
@@ -73,6 +75,48 @@ func newSeedOutpostCmd() *cobra.Command {
 	return cmd
 }
 
+func newSeedOAuthCmd() *cobra.Command {
+	opts := agent.SeedOAuthOptions{}
+	cmd := &cobra.Command{
+		Use:   "seed-oauth",
+		Short: "Seed an oauth2-proxy credential set into Vault KV",
+		Long: "Make a Vault KV-v2 path hold a complete oauth2-proxy credential set: the\n" +
+			"given client_id, plus a client_secret and a 32-byte cookie_secret that are\n" +
+			"generated only when missing (or with --rotate). Existing keys are preserved\n" +
+			"and nothing is written when the secret is already correct. Secret values are\n" +
+			"never printed or logged.",
+		SilenceUsage: true,
+		RunE: func(cmd *cobra.Command, args []string) error {
+			opts.VaultAddr = agent.VaultAddr()
+			opts.RoleID = agent.RoleID()
+			res, err := agent.SeedOAuth(opts)
+			if err != nil {
+				return err
+			}
+			out := cmd.OutOrStdout()
+			_, _ = fmt.Fprintf(out, "path:          %s/%s\n", res.KVMount, res.Path)
+			_, _ = fmt.Fprintf(out, "keys:          %s\n", strings.Join(res.KeyNames(), ", "))
+			for _, k := range res.Keys {
+				_, _ = fmt.Fprintf(out, "  %-14s %s\n", k.Name+":", k.Action)
+			}
+			if res.Changed {
+				_, _ = fmt.Fprintf(out, "version:       %d\n", res.Version)
+			} else {
+				_, _ = fmt.Fprintf(out, "version:       unchanged\n")
+			}
+			return nil
+		},
+	}
+	f := cmd.Flags()
+	f.StringVar(&opts.Path, "path", "", "KV-v2 path holding the credentials, e.g. kubernetes/namespace/repospawner/default/oauth-credentials (required)")
+	f.StringVar(&opts.ClientID, "client-id", "", "OIDC client id to store (required)")
+	f.StringVar(&opts.KVMount, "kv-mount", agent.DefaultKVMount, "KV-v2 mount holding the path")
+	f.BoolVar(&opts.Rotate, "rotate", false, "Regenerate client_secret and cookie_secret even when they already exist")
+	_ = cmd.MarkFlagRequired("path")
+	_ = cmd.MarkFlagRequired("client-id")
+	return cmd
+}
+
 func newVersionCmd() *cobra.Command {
 	return &cobra.Command{
 		Use:          "version",

cmd/agentvault/main_test.go

@@ -2,6 +2,7 @@ package main
 
 import (
 	"bytes"
+	"encoding/json"
 	"io"
 	"net/http"
 	"net/http/httptest"
@@ -78,6 +79,89 @@ func TestSeedOutpostOutputHasNoSecrets(t *testing.T) {
 	}
 }
 
+const oauthPath = "kubernetes/namespace/repospawner/default/oauth-credentials"
+
+// fakeOAuthVault serves approle login plus a KV-v2 path that already holds a
+// client_secret, and records what gets written back.
+func fakeOAuthVault(t *testing.T, existing map[string]string) (vaultURL string, written *map[string]string) {
+	t.Helper()
+	writes := map[string]string{}
+	mux := http.NewServeMux()
+	mux.HandleFunc("/v1/auth/approle/login", func(w http.ResponseWriter, r *http.Request) {
+		_, _ = io.WriteString(w, `{"auth":{"client_token":"s.vaulttoken"}}`)
+	})
+	mux.HandleFunc("/v1/kv/data/"+oauthPath, func(w http.ResponseWriter, r *http.Request) {
+		if r.Method == http.MethodPost {
+			var body struct {
+				Data map[string]string `json:"data"`
+			}
+			_ = json.NewDecoder(r.Body).Decode(&body)
+			for k, v := range body.Data {
+				writes[k] = v
+			}
+			_, _ = io.WriteString(w, `{"data":{"version":4}}`)
+			return
+		}
+		payload, _ := json.Marshal(map[string]any{"data": map[string]any{"data": existing}})
+		_, _ = w.Write(payload)
+	})
+	srv := httptest.NewServer(mux)
+	t.Cleanup(srv.Close)
+	return srv.URL, &writes
+}
+
+// The command prints key names and the KV version only — never a value.
+func TestSeedOAuthOutputHasNoSecrets(t *testing.T) {
+	const existingSecret = "existing-client-secret-value"
+	vaultURL, written := fakeOAuthVault(t, map[string]string{"client_secret": existingSecret})
+	t.Setenv("VAULT_ADDR", vaultURL)
+	t.Setenv("AGENT_APPROLE_ROLE_ID", "role-xyz")
+
+	var out bytes.Buffer
+	cmd := newRootCmd()
+	cmd.SetOut(&out)
+	cmd.SetErr(&out)
+	cmd.SetArgs([]string{"seed-oauth", "--path", oauthPath, "--client-id", "mediamark-client-id"})
+	if err := cmd.Execute(); err != nil {
+		t.Fatalf("Execute: %v", err)
+	}
+
+	got := out.String()
+	for _, want := range []string{"kv/" + oauthPath, "client_id, client_secret, cookie_secret", "client_secret: kept", "cookie_secret: created", "version:       4"} {
+		if !strings.Contains(got, want) {
+			t.Errorf("output missing %q:\n%s", want, got)
+		}
+	}
+	for key, value := range *written {
+		if key == "client_id" {
+			continue
+		}
+		if strings.Contains(got, value) {
+			t.Fatalf("output leaks the %s value:\n%s", key, got)
+		}
+	}
+	if strings.Contains(got, existingSecret) {
+		t.Fatalf("output leaks the existing client_secret:\n%s", got)
+	}
+}
+
+func TestSeedOAuthRequiresFlags(t *testing.T) {
+	for name, args := range map[string][]string{
+		"no path":      {"seed-oauth", "--client-id", "mediamark-client-id"},
+		"no client-id": {"seed-oauth", "--path", oauthPath},
+	} {
+		t.Run(name, func(t *testing.T) {
+			cmd := newRootCmd()
+			cmd.SetOut(io.Discard)
+			cmd.SetErr(io.Discard)
+			cmd.SetArgs(args)
+			if err := cmd.Execute(); err == nil {
+				t.Fatal("Execute() = nil, want a missing-required-flag error")
+			}
+		})
+	}
+}
+
 func TestSeedOutpostRequiresFlags(t *testing.T) {
 	for name, args := range map[string][]string{
 		"no outpost":   {"seed-outpost", "--dest-path", destPath},

internal/agent/seedoauth.go

@@ -0,0 +1,183 @@
+package agent
+
+import (
+	"crypto/rand"
+	"encoding/base64"
+	"errors"
+	"fmt"
+	"sort"
+)
+
+const (
+	// OAuthClientIDKey, OAuthClientSecretKey and OAuthCookieSecretKey are the
+	// KV fields oauth2-proxy deployments read their credentials from.
+	OAuthClientIDKey     = "client_id"
+	OAuthClientSecretKey = "client_secret"
+	OAuthCookieSecretKey = "cookie_secret"
+
+	// oauthSecretBytes is the raw length of generated secrets. oauth2-proxy
+	// rejects a cookie secret that does not decode to exactly 32 bytes.
+	oauthSecretBytes = 32
+)
+
+// Per-key outcomes reported by SeedOAuth.
+const (
+	ActionCreated   = "created"
+	ActionKept      = "kept"
+	ActionRotated   = "rotated"
+	ActionUpdated   = "updated"
+	ActionPreserved = "preserved"
+)
+
+// SeedOAuthOptions configures SeedOAuth. The CLI supplies the defaults.
+type SeedOAuthOptions struct {
+	VaultAddr string
+	RoleID    string
+	KVMount   string
+	Path      string
+	ClientID  string
+	Rotate    bool
+}
+
+// SeedOAuthKey names a key present in the secret and what happened to it.
+type SeedOAuthKey struct {
+	Name   string
+	Action string
+}
+
+// SeedOAuthResult is the non-secret summary of a seed run. Version is zero when
+// nothing changed and no write was issued.
+type SeedOAuthResult struct {
+	KVMount string
+	Path    string
+	Keys    []SeedOAuthKey
+	Version int
+	Changed bool
+}
+
+// KeyNames returns the key names present in the secret after the run.
+func (r SeedOAuthResult) KeyNames() []string {
+	names := make([]string, 0, len(r.Keys))
+	for _, k := range r.Keys {
+		names = append(names, k.Name)
+	}
+	return names
+}
+
+// SeedOAuth makes a Vault KV-v2 path hold a complete oauth2-proxy credential
+// set: client_id from the caller, plus a client_secret and cookie_secret that
+// are generated only when absent (or when Rotate is set). It is a
+// read-modify-write, so keys it does not own survive untouched, and it writes
+// nothing when the secret is already correct. Secret material never leaves this
+// function: results and errors carry only key names.
+func SeedOAuth(o SeedOAuthOptions) (SeedOAuthResult, error) {
+	var res SeedOAuthResult
+	if o.Path == "" {
+		return res, errors.New("a KV-v2 path is required")
+	}
+	if o.ClientID == "" {
+		return res, errors.New("a client id is required")
+	}
+
+	vc, err := NewVaultClient(o.VaultAddr, o.RoleID)
+	if err != nil {
+		return res, fmt.Errorf("vault approle login failed against %s (check VAULT_ADDR and AGENT_APPROLE_ROLE_ID): %w", o.VaultAddr, err)
+	}
+
+	existing, err := vc.ReadKVOptional(o.KVMount, o.Path)
+	if err != nil {
+		if errors.Is(err, ErrVaultDenied) {
+			return res, fmt.Errorf("reading %s/%s denied: the agent AppRole policy does not grant read on this path (apply the terraform-vault policy change): %w", o.KVMount, o.Path, err)
+		}
+		return res, fmt.Errorf("reading %s/%s: %w", o.KVMount, o.Path, err)
+	}
+
+	data := make(map[string]any, len(existing)+3)
+	for k, v := range existing {
+		data[k] = v
+	}
+
+	var (
+		keys    []SeedOAuthKey
+		changed bool
+	)
+
+	current, _ := existing[OAuthClientIDKey].(string)
+	switch current {
+	case o.ClientID:
+		keys = append(keys, SeedOAuthKey{OAuthClientIDKey, ActionKept})
+	case "":
+		keys = append(keys, SeedOAuthKey{OAuthClientIDKey, ActionCreated})
+		changed = true
+	default:
+		keys = append(keys, SeedOAuthKey{OAuthClientIDKey, ActionUpdated})
+		changed = true
+	}
+	data[OAuthClientIDKey] = o.ClientID
+
+	for _, gen := range []struct {
+		name string
+		enc  *base64.Encoding
+	}{
+		// oauth2-proxy accepts a standard-base64 client secret, but the cookie
+		// secret goes into a cookie and must be URL-safe.
+		{OAuthClientSecretKey, base64.StdEncoding},
+		{OAuthCookieSecretKey, base64.RawURLEncoding},
+	} {
+		current, _ := existing[gen.name].(string)
+		if current != "" && !o.Rotate {
+			keys = append(keys, SeedOAuthKey{gen.name, ActionKept})
+			continue
+		}
+		value, err := randomSecret(gen.enc)
+		if err != nil {
+			return res, fmt.Errorf("generating %s: %w", gen.name, err)
+		}
+		action := ActionCreated
+		if current != "" {
+			action = ActionRotated
+		}
+		data[gen.name] = value
+		keys = append(keys, SeedOAuthKey{gen.name, action})
+		changed = true
+	}
+
+	var others []string
+	for k := range existing {
+		switch k {
+		case OAuthClientIDKey, OAuthClientSecretKey, OAuthCookieSecretKey:
+		default:
+			others = append(others, k)
+		}
+	}
+	sort.Strings(others)
+	for _, k := range others {
+		keys = append(keys, SeedOAuthKey{k, ActionPreserved})
+	}
+
+	res = SeedOAuthResult{KVMount: o.KVMount, Path: o.Path, Keys: keys}
+	if !changed {
+		return res, nil
+	}
+
+	version, err := vc.WriteKVAny(o.KVMount, o.Path, data)
+	if err != nil {
+		if errors.Is(err, ErrVaultDenied) {
+			return SeedOAuthResult{}, fmt.Errorf("writing %s/%s denied: the agent AppRole policy does not grant create/update on this path (apply the terraform-vault policy change): %w", o.KVMount, o.Path, err)
+		}
+		return SeedOAuthResult{}, fmt.Errorf("writing %s/%s: %w", o.KVMount, o.Path, err)
+	}
+	res.Version = version
+	res.Changed = true
+	return res, nil
+}
+
+// randomSecret returns oauthSecretBytes of crypto/rand entropy in the given
+// base64 encoding.
+func randomSecret(enc *base64.Encoding) (string, error) {
+	buf := make([]byte, oauthSecretBytes)
+	if _, err := rand.Read(buf); err != nil {
+		return "", err
+	}
+	return enc.EncodeToString(buf), nil
+}

internal/agent/seedoauth_test.go

@@ -0,0 +1,421 @@
+package agent
+
+import (
+	"encoding/base64"
+	"encoding/json"
+	"io"
+	"net/http"
+	"net/http/httptest"
+	"strconv"
+	"strings"
+	"testing"
+)
+
+const (
+	oauthPath           = "kubernetes/namespace/repospawner/default/oauth-credentials"
+	oauthClientID       = "mediamark-client-id"
+	existingClientSec   = "existing-client-secret-from-authentik"
+	existingCookieSec   = "existing-cookie-secret-value-abcdefghij"
+	oauthExtraKeyValue  = "extra-key-secret-value"
+	oauthVaultClientTok = "s.vaulttoken"
+)
+
+// oauthVaultStub is a KV-v2 stand-in that actually stores what is written, so
+// read-modify-write behaviour can be asserted end to end.
+type oauthVaultStub struct {
+	data        map[string]any
+	exists      bool
+	version     int
+	readStatus  int
+	writeStatus int
+	writes      []map[string]any
+}
+
+func newOAuthVaultStub() *oauthVaultStub {
+	return &oauthVaultStub{readStatus: http.StatusOK, writeStatus: http.StatusOK}
+}
+
+// seed makes the path exist with the given fields at version 1.
+func (v *oauthVaultStub) seed(data map[string]any) *oauthVaultStub {
+	v.data = data
+	v.exists = true
+	v.version = 1
+	return v
+}
+
+func (v *oauthVaultStub) server(t *testing.T) *httptest.Server {
+	t.Helper()
+	mux := http.NewServeMux()
+	mux.HandleFunc("/v1/auth/approle/login", func(w http.ResponseWriter, r *http.Request) {
+		var body map[string]string
+		_ = json.NewDecoder(r.Body).Decode(&body)
+		if _, ok := body["secret_id"]; ok {
+			t.Errorf("secret_id must not be sent")
+		}
+		_, _ = io.WriteString(w, `{"auth":{"client_token":"`+oauthVaultClientTok+`"}}`)
+	})
+	mux.HandleFunc("/v1/kv/data/"+oauthPath, func(w http.ResponseWriter, r *http.Request) {
+		if got := r.Header.Get("X-Vault-Token"); got != oauthVaultClientTok {
+			t.Errorf("X-Vault-Token = %q, want %q", got, oauthVaultClientTok)
+		}
+		switch r.Method {
+		case http.MethodGet:
+			if v.readStatus != http.StatusOK {
+				w.WriteHeader(v.readStatus)
+				_, _ = io.WriteString(w, `{"errors":["permission denied"]}`)
+				return
+			}
+			if !v.exists {
+				w.WriteHeader(http.StatusNotFound)
+				_, _ = io.WriteString(w, `{"errors":[]}`)
+				return
+			}
+			payload, _ := json.Marshal(map[string]any{
+				"data": map[string]any{"data": v.data, "metadata": map[string]any{"version": v.version}},
+			})
+			_, _ = w.Write(payload)
+		case http.MethodPost:
+			if v.writeStatus != http.StatusOK {
+				w.WriteHeader(v.writeStatus)
+				_, _ = io.WriteString(w, `{"errors":["permission denied"]}`)
+				return
+			}
+			var body struct {
+				Data map[string]any `json:"data"`
+			}
+			_ = json.NewDecoder(r.Body).Decode(&body)
+			v.writes = append(v.writes, body.Data)
+			v.data = body.Data
+			v.exists = true
+			v.version++
+			_, _ = io.WriteString(w, `{"data":{"version":`+strconv.Itoa(v.version)+`}}`)
+		default:
+			t.Errorf("unexpected method %s", r.Method)
+		}
+	})
+	srv := httptest.NewServer(mux)
+	t.Cleanup(srv.Close)
+	return srv
+}
+
+func oauthOpts(vaultURL string) SeedOAuthOptions {
+	return SeedOAuthOptions{
+		VaultAddr: vaultURL,
+		RoleID:    "role-xyz",
+		KVMount:   DefaultKVMount,
+		Path:      oauthPath,
+		ClientID:  oauthClientID,
+	}
+}
+
+// actions flattens a result into key -> action for order-independent asserts.
+func actions(res SeedOAuthResult) map[string]string {
+	m := make(map[string]string, len(res.Keys))
+	for _, k := range res.Keys {
+		m[k.Name] = k.Action
+	}
+	return m
+}
+
+func stringField(t *testing.T, data map[string]any, key string) string {
+	t.Helper()
+	s, ok := data[key].(string)
+	if !ok {
+		t.Fatalf("written %s = %v, want a string", key, data[key])
+	}
+	return s
+}
+
+// assertDecodesTo32 fails unless the value is base64 of exactly 32 bytes, which
+// is what oauth2-proxy requires of a cookie secret.
+func assertDecodesTo32(t *testing.T, enc *base64.Encoding, value, name string) {
+	t.Helper()
+	raw, err := enc.DecodeString(value)
+	if err != nil {
+		t.Fatalf("%s is not valid base64: %v", name, err)
+	}
+	if len(raw) != oauthSecretBytes {
+		t.Errorf("%s decodes to %d bytes, want %d", name, len(raw), oauthSecretBytes)
+	}
+}
+
+func TestSeedOAuthFreshCreate(t *testing.T) {
+	v := newOAuthVaultStub()
+	res, err := SeedOAuth(oauthOpts(v.server(t).URL))
+	if err != nil {
+		t.Fatalf("SeedOAuth: %v", err)
+	}
+	if !res.Changed || res.Version != 1 {
+		t.Errorf("Changed=%v Version=%d, want a first write at version 1", res.Changed, res.Version)
+	}
+	for key, want := range map[string]string{
+		OAuthClientIDKey:     ActionCreated,
+		OAuthClientSecretKey: ActionCreated,
+		OAuthCookieSecretKey: ActionCreated,
+	} {
+		if got := actions(res)[key]; got != want {
+			t.Errorf("%s action = %q, want %q", key, got, want)
+		}
+	}
+	if len(v.writes) != 1 {
+		t.Fatalf("%d writes, want exactly 1", len(v.writes))
+	}
+	w := v.writes[0]
+	if got := stringField(t, w, OAuthClientIDKey); got != oauthClientID {
+		t.Errorf("written client_id = %q, want %q", got, oauthClientID)
+	}
+	assertDecodesTo32(t, base64.StdEncoding, stringField(t, w, OAuthClientSecretKey), OAuthClientSecretKey)
+	assertDecodesTo32(t, base64.RawURLEncoding, stringField(t, w, OAuthCookieSecretKey), OAuthCookieSecretKey)
+}
+
+// The mediamark case: a client_secret already issued by Authentik must survive
+// while the missing keys are filled in.
+func TestSeedOAuthPreservesExistingClientSecret(t *testing.T) {
+	v := newOAuthVaultStub().seed(map[string]any{OAuthClientSecretKey: existingClientSec})
+	res, err := SeedOAuth(oauthOpts(v.server(t).URL))
+	if err != nil {
+		t.Fatalf("SeedOAuth: %v", err)
+	}
+	got := actions(res)
+	for key, want := range map[string]string{
+		OAuthClientIDKey:     ActionCreated,
+		OAuthClientSecretKey: ActionKept,
+		OAuthCookieSecretKey: ActionCreated,
+	} {
+		if got[key] != want {
+			t.Errorf("%s action = %q, want %q", key, got[key], want)
+		}
+	}
+	if len(v.writes) != 1 {
+		t.Fatalf("%d writes, want exactly 1", len(v.writes))
+	}
+	if s := stringField(t, v.writes[0], OAuthClientSecretKey); s != existingClientSec {
+		t.Errorf("client_secret was replaced, want the existing value kept")
+	}
+}
+
+func TestSeedOAuthPreservesOtherKeys(t *testing.T) {
+	v := newOAuthVaultStub().seed(map[string]any{
+		OAuthClientIDKey:     oauthClientID,
+		OAuthClientSecretKey: existingClientSec,
+		"redirect_url":       "https://mediamark.unkin.net/oauth2/callback",
+		"extra":              oauthExtraKeyValue,
+	})
+	res, err := SeedOAuth(oauthOpts(v.server(t).URL))
+	if err != nil {
+		t.Fatalf("SeedOAuth: %v", err)
+	}
+	got := actions(res)
+	for _, key := range []string{"redirect_url", "extra"} {
+		if got[key] != ActionPreserved {
+			t.Errorf("%s action = %q, want %q", key, got[key], ActionPreserved)
+		}
+	}
+	if len(v.writes) != 1 {
+		t.Fatalf("%d writes, want exactly 1", len(v.writes))
+	}
+	w := v.writes[0]
+	if stringField(t, w, "extra") != oauthExtraKeyValue {
+		t.Errorf("extra key was not written back unchanged")
+	}
+	if stringField(t, w, "redirect_url") != "https://mediamark.unkin.net/oauth2/callback" {
+		t.Errorf("redirect_url was not written back unchanged")
+	}
+}
+
+func TestSeedOAuthRotateRegenerates(t *testing.T) {
+	v := newOAuthVaultStub().seed(map[string]any{
+		OAuthClientIDKey:     oauthClientID,
+		OAuthClientSecretKey: existingClientSec,
+		OAuthCookieSecretKey: existingCookieSec,
+	})
+	o := oauthOpts(v.server(t).URL)
+	o.Rotate = true
+
+	res, err := SeedOAuth(o)
+	if err != nil {
+		t.Fatalf("SeedOAuth: %v", err)
+	}
+	got := actions(res)
+	for key, want := range map[string]string{
+		OAuthClientIDKey:     ActionKept,
+		OAuthClientSecretKey: ActionRotated,
+		OAuthCookieSecretKey: ActionRotated,
+	} {
+		if got[key] != want {
+			t.Errorf("%s action = %q, want %q", key, got[key], want)
+		}
+	}
+	if len(v.writes) != 1 {
+		t.Fatalf("%d writes, want exactly 1", len(v.writes))
+	}
+	w := v.writes[0]
+	if stringField(t, w, OAuthClientSecretKey) == existingClientSec {
+		t.Errorf("client_secret unchanged under --rotate")
+	}
+	if stringField(t, w, OAuthCookieSecretKey) == existingCookieSec {
+		t.Errorf("cookie_secret unchanged under --rotate")
+	}
+	assertDecodesTo32(t, base64.RawURLEncoding, stringField(t, w, OAuthCookieSecretKey), OAuthCookieSecretKey)
+}
+
+// A complete, correct secret must not produce a new KV version.
+func TestSeedOAuthIdempotentWritesNothing(t *testing.T) {
+	v := newOAuthVaultStub()
+	url := v.server(t).URL
+	if _, err := SeedOAuth(oauthOpts(url)); err != nil {
+		t.Fatalf("first SeedOAuth: %v", err)
+	}
+	res, err := SeedOAuth(oauthOpts(url))
+	if err != nil {
+		t.Fatalf("second SeedOAuth: %v", err)
+	}
+	if res.Changed || res.Version != 0 {
+		t.Errorf("Changed=%v Version=%d, want an unchanged result", res.Changed, res.Version)
+	}
+	if len(v.writes) != 1 {
+		t.Errorf("%d writes, want the second run to write nothing", len(v.writes))
+	}
+	for _, k := range res.Keys {
+		if k.Action != ActionKept {
+			t.Errorf("%s action = %q, want %q", k.Name, k.Action, ActionKept)
+		}
+	}
+}
+
+func TestSeedOAuthClientIDUpdated(t *testing.T) {
+	v := newOAuthVaultStub().seed(map[string]any{
+		OAuthClientIDKey:     "stale-client-id",
+		OAuthClientSecretKey: existingClientSec,
+		OAuthCookieSecretKey: existingCookieSec,
+	})
+	res, err := SeedOAuth(oauthOpts(v.server(t).URL))
+	if err != nil {
+		t.Fatalf("SeedOAuth: %v", err)
+	}
+	if got := actions(res)[OAuthClientIDKey]; got != ActionUpdated {
+		t.Errorf("client_id action = %q, want %q", got, ActionUpdated)
+	}
+	if len(v.writes) != 1 || stringField(t, v.writes[0], OAuthClientIDKey) != oauthClientID {
+		t.Errorf("writes = %v, want the new client_id written", v.writes)
+	}
+}
+
+func TestSeedOAuthLoginFailure(t *testing.T) {
+	mux := http.NewServeMux()
+	mux.HandleFunc("/v1/auth/approle/login", func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(http.StatusBadRequest)
+		_, _ = io.WriteString(w, `{"errors":["invalid role ID"]}`)
+	})
+	vs := httptest.NewServer(mux)
+	defer vs.Close()
+
+	_, err := SeedOAuth(oauthOpts(vs.URL))
+	if err == nil {
+		t.Fatal("SeedOAuth() = nil, want an approle login error")
+	}
+	if !strings.Contains(err.Error(), "approle login failed") {
+		t.Errorf("error = %v, want it to name the approle login", err)
+	}
+}
+
+func TestSeedOAuthReadDenied(t *testing.T) {
+	v := newOAuthVaultStub()
+	v.readStatus = http.StatusForbidden
+
+	_, err := SeedOAuth(oauthOpts(v.server(t).URL))
+	if err == nil {
+		t.Fatal("SeedOAuth() = nil, want a KV read error")
+	}
+	msg := err.Error()
+	if !strings.Contains(msg, oauthPath) || !strings.Contains(msg, "policy") {
+		t.Errorf("error = %v, want it to name the path and point at the policy", err)
+	}
+	if len(v.writes) != 0 {
+		t.Errorf("wrote %v, want no write when the read is denied", v.writes)
+	}
+}
+
+func TestSeedOAuthWriteDenied(t *testing.T) {
+	v := newOAuthVaultStub()
+	v.writeStatus = http.StatusForbidden
+
+	_, err := SeedOAuth(oauthOpts(v.server(t).URL))
+	if err == nil {
+		t.Fatal("SeedOAuth() = nil, want a KV write error")
+	}
+	msg := err.Error()
+	if !strings.Contains(msg, oauthPath) || !strings.Contains(msg, "create/update") {
+		t.Errorf("error = %v, want it to name the path and the missing capability", err)
+	}
+}
+
+// A missing path is normal (first seed), not a not-found error.
+func TestSeedOAuthMissingPathIsNotAnError(t *testing.T) {
+	v := newOAuthVaultStub()
+	if _, err := SeedOAuth(oauthOpts(v.server(t).URL)); err != nil {
+		t.Fatalf("SeedOAuth on a missing path: %v", err)
+	}
+}
+
+func TestSeedOAuthRequiresPathAndClientID(t *testing.T) {
+	v := newOAuthVaultStub()
+	url := v.server(t).URL
+	for name, mutate := range map[string]func(*SeedOAuthOptions){
+		"no path":      func(o *SeedOAuthOptions) { o.Path = "" },
+		"no client id": func(o *SeedOAuthOptions) { o.ClientID = "" },
+	} {
+		t.Run(name, func(t *testing.T) {
+			o := oauthOpts(url)
+			mutate(&o)
+			if _, err := SeedOAuth(o); err == nil {
+				t.Fatal("SeedOAuth() = nil, want a required-input error")
+			}
+		})
+	}
+}
+
+// No failure path may leak stored or generated secret material.
+func TestSeedOAuthErrorsNeverLeakSecrets(t *testing.T) {
+	cases := map[string]func(*oauthVaultStub){
+		"read denied":  func(v *oauthVaultStub) { v.readStatus = http.StatusForbidden },
+		"write denied": func(v *oauthVaultStub) { v.writeStatus = http.StatusForbidden },
+		"read error":   func(v *oauthVaultStub) { v.readStatus = http.StatusInternalServerError },
+		"write error":  func(v *oauthVaultStub) { v.writeStatus = http.StatusInternalServerError },
+	}
+	for name, mutate := range cases {
+		t.Run(name, func(t *testing.T) {
+			v := newOAuthVaultStub().seed(map[string]any{
+				OAuthClientSecretKey: existingClientSec,
+				OAuthCookieSecretKey: existingCookieSec,
+				"extra":              oauthExtraKeyValue,
+			})
+			mutate(v)
+			_, err := SeedOAuth(oauthOpts(v.server(t).URL))
+			if err == nil {
+				t.Fatal("SeedOAuth() = nil, want an error")
+			}
+			for _, secret := range []string{existingClientSec, existingCookieSec, oauthExtraKeyValue} {
+				if strings.Contains(err.Error(), secret) {
+					t.Errorf("error %q leaks a secret", err)
+				}
+			}
+		})
+	}
+}
+
+// The successful result carries key names and a version, never values.
+func TestSeedOAuthResultNeverCarriesSecrets(t *testing.T) {
+	v := newOAuthVaultStub().seed(map[string]any{OAuthClientSecretKey: existingClientSec})
+	res, err := SeedOAuth(oauthOpts(v.server(t).URL))
+	if err != nil {
+		t.Fatalf("SeedOAuth: %v", err)
+	}
+	rendered := strings.Join(append(res.KeyNames(), res.Path, res.KVMount), " ")
+	written := v.writes[0]
+	for _, key := range []string{OAuthClientSecretKey, OAuthCookieSecretKey} {
+		if value := stringField(t, written, key); strings.Contains(rendered, value) {
+			t.Errorf("result leaks the %s value", key)
+		}
+	}
+}

internal/agent/vaultkv.go

@@ -106,8 +106,40 @@ func (c *VaultClient) ReadKV(mount, path string) (map[string]any, error) {
 	return out.Data.Data, nil
 }
 
+// ReadKVOptional is ReadKV but treats a missing secret as empty: a 404 or a
+// deleted version (data: null) yields an empty map, not an error. Callers that
+// read-modify-write a path that may not exist yet use this.
+func (c *VaultClient) ReadKVOptional(mount, path string) (map[string]any, error) {
+	var out struct {
+		Data struct {
+			Data map[string]any `json:"data"`
+		} `json:"data"`
+	}
+	if err := c.do(http.MethodGet, kvDataPath(mount, path), nil, &out); err != nil {
+		if errors.Is(err, ErrVaultNotFound) {
+			return map[string]any{}, nil
+		}
+		return nil, err
+	}
+	if out.Data.Data == nil {
+		return map[string]any{}, nil
+	}
+	return out.Data.Data, nil
+}
+
 // WriteKV writes a KV-v2 secret and returns the version it created.
 func (c *VaultClient) WriteKV(mount, path string, data map[string]string) (int, error) {
+	fields := make(map[string]any, len(data))
+	for k, v := range data {
+		fields[k] = v
+	}
+	return c.WriteKVAny(mount, path, fields)
+}
+
+// WriteKVAny writes a KV-v2 secret whose fields are not all strings (so a
+// read-modify-write can put back values it did not author) and returns the
+// version it created.
+func (c *VaultClient) WriteKVAny(mount, path string, data map[string]any) (int, error) {
 	var out struct {
 		Data struct {
 			Version int `json:"version"`