Add agentvault with a seed-outpost subcommand

Interactive agents are classifier-blocked from plumbing credentials through a shell, so seeding an Authentik outpost token into Vault KV needs to happen inside one binary invocation that never exposes the secret. - Add cmd/agentvault, a fourth CLI sharing the agentpr Vault AppRole login (role_id only, VAULT_ADDR/AGENT_APPROLE_ROLE_ID defaults unchanged). - Add `agentvault seed-outpost`: read the Authentik API token from kv/service/authentik/agent-api-token (field `token`, falling back to `api_token`), exact-match the outpost by name via the instances search, fetch its key from /api/v3/core/tokens/<identifier>/view_key/ and write it to --dest-path under --dest-key. - Print only the outpost name, token identifier, dest path and new KV version; keep secret material out of results, errors and logs. - Distinguish the failure stages (login, KV read denied, outpost missing, view_key, KV write denied) with ErrVaultDenied/ErrVaultNotFound/ ErrOutpostNotFound sentinels and actionable messages. - Add internal/agent vaultkv.go (AppRole-authenticated KV-v2 client) and authentik.go (outpost search + view_key) for reuse by future flows. - Cover the happy path, idempotent re-run, field fallback and every failure mode with httptest servers, including a leak check on error strings. - Wire agentvault into the Makefile, build-rpm.sh, nfpm contents, release cross-builds/assets, README and AGENTS.md.
2026-08-29 21:03:31 +10:00
parent 60b08f1198
commit 61bb464e32
13 changed files with 982 additions and 16 deletions
@@ -0,0 +1,93 @@
+package agent
+
+import (
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io"
+	"net/http"
+	"net/url"
+	"strings"
+)
+
+// ErrOutpostNotFound marks a search that returned no exactly-named outpost.
+var ErrOutpostNotFound = errors.New("outpost not found")
+
+// AuthentikClient talks to the Authentik REST API with a bearer API token. The
+// internal CA is in the OS trust store, so the default transport suffices.
+type AuthentikClient struct {
+	BaseURL string
+	Token   string
+	HTTP    *http.Client
+}
+
+// NewAuthentikClient builds a client for the given Authentik base URL.
+func NewAuthentikClient(baseURL, token string) *AuthentikClient {
+	return &AuthentikClient{BaseURL: strings.TrimRight(baseURL, "/"), Token: token, HTTP: httpClient}
+}
+
+// Outpost is the subset of Authentik's outpost object we need.
+type Outpost struct {
+	PK              string `json:"pk"`
+	Name            string `json:"name"`
+	TokenIdentifier string `json:"token_identifier"`
+}
+
+// get issues an authenticated GET and decodes into out. Error text never
+// includes a successful response body, which may carry key material.
+func (c *AuthentikClient) get(path string, out any) error {
+	req, err := http.NewRequest(http.MethodGet, c.BaseURL+path, nil)
+	if err != nil {
+		return err
+	}
+	req.Header.Set("Authorization", "Bearer "+c.Token)
+	req.Header.Set("Accept", "application/json")
+
+	resp, err := c.HTTP.Do(req)
+	if err != nil {
+		return fmt.Errorf("authentik GET %s: %w", path, err)
+	}
+	defer func() { _ = resp.Body.Close() }()
+	data, _ := io.ReadAll(resp.Body)
+	if resp.StatusCode < 200 || resp.StatusCode >= 300 {
+		return fmt.Errorf("authentik GET %s: HTTP %d: %s", path, resp.StatusCode, strings.TrimSpace(string(data)))
+	}
+	if err := json.Unmarshal(data, out); err != nil {
+		return fmt.Errorf("authentik GET %s: decoding response: %w", path, err)
+	}
+	return nil
+}
+
+// FindOutpost searches outpost instances and returns the one whose name matches
+// exactly (search is a substring match, so the exact name is re-checked here).
+func (c *AuthentikClient) FindOutpost(name string) (Outpost, error) {
+	var out struct {
+		Results []Outpost `json:"results"`
+	}
+	path := "/api/v3/outposts/instances/?search=" + url.QueryEscape(name)
+	if err := c.get(path, &out); err != nil {
+		return Outpost{}, err
+	}
+	for _, o := range out.Results {
+		if o.Name == name {
+			return o, nil
+		}
+	}
+	return Outpost{}, fmt.Errorf("authentik outpost %q: %w (searched %d result(s))", name, ErrOutpostNotFound, len(out.Results))
+}
+
+// TokenKey returns the key behind a token identifier
+// (GET /api/v3/core/tokens/<identifier>/view_key/).
+func (c *AuthentikClient) TokenKey(identifier string) (string, error) {
+	var out struct {
+		Key string `json:"key"`
+	}
+	path := "/api/v3/core/tokens/" + url.PathEscape(identifier) + "/view_key/"
+	if err := c.get(path, &out); err != nil {
+		return "", err
+	}
+	if out.Key == "" {
+		return "", fmt.Errorf("authentik view_key for %q: response has no key field", identifier)
+	}
+	return out.Key, nil
+}
@@ -0,0 +1,98 @@
+package agent
+
+import (
+	"errors"
+	"fmt"
+)
+
+const (
+	// DefaultOutpostTokenPath is the KV-v2 path holding the Authentik API token
+	// the agent uses to read outpost tokens.
+	DefaultOutpostTokenPath = "service/authentik/agent-api-token"
+	// DefaultDestKey is the KV field the outpost token is written to.
+	DefaultDestKey = "token"
+)
+
+// SeedOutpostOptions configures SeedOutpost. Every field is required; the CLI
+// supplies the defaults.
+type SeedOutpostOptions struct {
+	VaultAddr    string
+	RoleID       string
+	AuthentikURL string
+	Outpost      string
+	KVMount      string
+	TokenPath    string
+	DestPath     string
+	DestKey      string
+}
+
+// SeedOutpostResult is the non-secret summary of a successful seed.
+type SeedOutpostResult struct {
+	Outpost         string
+	TokenIdentifier string
+	KVMount         string
+	DestPath        string
+	Version         int
+}
+
+// SeedOutpost copies an Authentik outpost's token into Vault KV-v2. It reads an
+// Authentik API token from Vault, resolves the outpost's token identifier,
+// fetches the key and writes it to the destination path. The token value never
+// leaves this function: results and errors carry only identifiers.
+func SeedOutpost(o SeedOutpostOptions) (SeedOutpostResult, error) {
+	var res SeedOutpostResult
+
+	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)
+	}
+
+	secret, err := vc.ReadKV(o.KVMount, o.TokenPath)
+	if err != nil {
+		switch {
+		case 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.TokenPath, err)
+		case errors.Is(err, ErrVaultNotFound):
+			return res, fmt.Errorf("secret %s/%s does not exist: seed the Authentik API token there first: %w", o.KVMount, o.TokenPath, err)
+		}
+		return res, fmt.Errorf("reading %s/%s: %w", o.KVMount, o.TokenPath, err)
+	}
+
+	apiToken := StringField(secret, "token", "api_token")
+	if apiToken == "" {
+		return res, fmt.Errorf("secret %s/%s has neither a 'token' nor an 'api_token' field", o.KVMount, o.TokenPath)
+	}
+
+	ac := NewAuthentikClient(o.AuthentikURL, apiToken)
+	outpost, err := ac.FindOutpost(o.Outpost)
+	if err != nil {
+		if errors.Is(err, ErrOutpostNotFound) {
+			return res, fmt.Errorf("no outpost named %q at %s: has the terraform-authentik outpost been applied?: %w", o.Outpost, o.AuthentikURL, err)
+		}
+		return res, fmt.Errorf("looking up outpost %q: %w", o.Outpost, err)
+	}
+	if outpost.TokenIdentifier == "" {
+		return res, fmt.Errorf("outpost %q has an empty token_identifier", outpost.Name)
+	}
+
+	key, err := ac.TokenKey(outpost.TokenIdentifier)
+	if err != nil {
+		return res, fmt.Errorf("fetching the key for token identifier %q (the API token needs view_key on it): %w", outpost.TokenIdentifier, err)
+	}
+
+	version, err := vc.WriteKV(o.KVMount, o.DestPath, map[string]string{o.DestKey: key})
+	if err != nil {
+		if errors.Is(err, ErrVaultDenied) {
+			return res, 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.DestPath, err)
+		}
+		return res, fmt.Errorf("writing %s/%s: %w", o.KVMount, o.DestPath, err)
+	}
+
+	return SeedOutpostResult{
+		Outpost:         outpost.Name,
+		TokenIdentifier: outpost.TokenIdentifier,
+		KVMount:         o.KVMount,
+		DestPath:        o.DestPath,
+		Version:         version,
+	}, nil
+}
@@ -0,0 +1,369 @@
+package agent
+
+import (
+	"encoding/json"
+	"io"
+	"net/http"
+	"net/http/httptest"
+	"strconv"
+	"strings"
+	"testing"
+)
+
+const (
+	testAPIToken     = "ak-api-token-secret"
+	testOutpostKey   = "outpost-key-secret"
+	testTokenPath    = "service/authentik/agent-api-token"
+	testDestPath     = "kubernetes/namespace/authentik/default/outpost-token"
+	testOutpostName  = "k8s-outpost"
+	testTokenIdent   = "ak-outpost-k8s-outpost"
+	testVaultClientT = "s.vaulttoken"
+)
+
+// vaultStub is a KV-v2 stand-in whose per-path behaviour tests can override.
+type vaultStub struct {
+	readStatus  int
+	writeStatus int
+	tokenField  string // field name the API token is stored under
+	writes      []map[string]string
+	writeCount  int
+}
+
+func newVaultStub() *vaultStub {
+	return &vaultStub{readStatus: http.StatusOK, writeStatus: http.StatusOK, tokenField: "token"}
+}
+
+func (v *vaultStub) 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":"`+testVaultClientT+`"}}`)
+	})
+	mux.HandleFunc("/v1/kv/data/"+testTokenPath, func(w http.ResponseWriter, r *http.Request) {
+		if got := r.Header.Get("X-Vault-Token"); got != testVaultClientT {
+			t.Errorf("X-Vault-Token = %q, want %q", got, testVaultClientT)
+		}
+		if v.readStatus != http.StatusOK {
+			w.WriteHeader(v.readStatus)
+			_, _ = io.WriteString(w, `{"errors":["permission denied"]}`)
+			return
+		}
+		_, _ = io.WriteString(w, `{"data":{"data":{"`+v.tokenField+`":"`+testAPIToken+`"},"metadata":{"version":1}}}`)
+	})
+	mux.HandleFunc("/v1/kv/data/"+testDestPath, func(w http.ResponseWriter, r *http.Request) {
+		if r.Method != http.MethodPost {
+			t.Errorf("write method = %s, want POST", r.Method)
+		}
+		if v.writeStatus != http.StatusOK {
+			w.WriteHeader(v.writeStatus)
+			_, _ = io.WriteString(w, `{"errors":["permission denied"]}`)
+			return
+		}
+		var body struct {
+			Data map[string]string `json:"data"`
+		}
+		_ = json.NewDecoder(r.Body).Decode(&body)
+		v.writes = append(v.writes, body.Data)
+		v.writeCount++
+		_, _ = io.WriteString(w, `{"data":{"version":`+strconv.Itoa(v.writeCount+2)+`}}`)
+	})
+	srv := httptest.NewServer(mux)
+	t.Cleanup(srv.Close)
+	return srv
+}
+
+// authentikStub serves the outpost search and view_key endpoints.
+type authentikStub struct {
+	results        string // JSON array body for .results
+	viewKeyStatus  int
+	viewKeyBody    string
+	sawBearer      string
+	sawSearchQuery string
+}
+
+func newAuthentikStub() *authentikStub {
+	return &authentikStub{
+		results:       `{"pk":"1","name":"` + testOutpostName + `","token_identifier":"` + testTokenIdent + `"}`,
+		viewKeyStatus: http.StatusOK,
+		viewKeyBody:   `{"key":"` + testOutpostKey + `"}`,
+	}
+}
+
+func (a *authentikStub) server(t *testing.T) *httptest.Server {
+	t.Helper()
+	mux := http.NewServeMux()
+	mux.HandleFunc("/api/v3/outposts/instances/", func(w http.ResponseWriter, r *http.Request) {
+		a.sawBearer = r.Header.Get("Authorization")
+		a.sawSearchQuery = r.URL.Query().Get("search")
+		_, _ = io.WriteString(w, `{"results":[`+a.results+`]}`)
+	})
+	mux.HandleFunc("/api/v3/core/tokens/"+testTokenIdent+"/view_key/", func(w http.ResponseWriter, r *http.Request) {
+		if a.viewKeyStatus != http.StatusOK {
+			w.WriteHeader(a.viewKeyStatus)
+			_, _ = io.WriteString(w, `{"detail":"boom"}`)
+			return
+		}
+		_, _ = io.WriteString(w, a.viewKeyBody)
+	})
+	srv := httptest.NewServer(mux)
+	t.Cleanup(srv.Close)
+	return srv
+}
+
+func opts(vaultURL, authentikURL string) SeedOutpostOptions {
+	return SeedOutpostOptions{
+		VaultAddr:    vaultURL,
+		RoleID:       "role-xyz",
+		AuthentikURL: authentikURL,
+		Outpost:      testOutpostName,
+		KVMount:      DefaultKVMount,
+		TokenPath:    testTokenPath,
+		DestPath:     testDestPath,
+		DestKey:      DefaultDestKey,
+	}
+}
+
+func TestSeedOutpostHappyPath(t *testing.T) {
+	v := newVaultStub()
+	a := newAuthentikStub()
+	vs, as := v.server(t), a.server(t)
+
+	res, err := SeedOutpost(opts(vs.URL, as.URL))
+	if err != nil {
+		t.Fatalf("SeedOutpost: %v", err)
+	}
+	if res.Outpost != testOutpostName {
+		t.Errorf("Outpost = %q, want %q", res.Outpost, testOutpostName)
+	}
+	if res.TokenIdentifier != testTokenIdent {
+		t.Errorf("TokenIdentifier = %q, want %q", res.TokenIdentifier, testTokenIdent)
+	}
+	if res.DestPath != testDestPath || res.KVMount != DefaultKVMount {
+		t.Errorf("dest = %s/%s, want kv/%s", res.KVMount, res.DestPath, testDestPath)
+	}
+	if res.Version != 3 {
+		t.Errorf("Version = %d, want 3", res.Version)
+	}
+	if a.sawBearer != "Bearer "+testAPIToken {
+		t.Errorf("Authorization = %q, want the API token as a bearer", a.sawBearer)
+	}
+	if a.sawSearchQuery != testOutpostName {
+		t.Errorf("search = %q, want %q", a.sawSearchQuery, testOutpostName)
+	}
+	if len(v.writes) != 1 || v.writes[0][DefaultDestKey] != testOutpostKey {
+		t.Fatalf("written data = %v, want {%s: outpost key}", v.writes, DefaultDestKey)
+	}
+}
+
+// Re-running writes a new KV version rather than failing.
+func TestSeedOutpostIdempotentNewVersion(t *testing.T) {
+	v := newVaultStub()
+	a := newAuthentikStub()
+	vs, as := v.server(t), a.server(t)
+
+	first, err := SeedOutpost(opts(vs.URL, as.URL))
+	if err != nil {
+		t.Fatalf("first SeedOutpost: %v", err)
+	}
+	second, err := SeedOutpost(opts(vs.URL, as.URL))
+	if err != nil {
+		t.Fatalf("second SeedOutpost: %v", err)
+	}
+	if second.Version != first.Version+1 {
+		t.Errorf("versions = %d then %d, want consecutive", first.Version, second.Version)
+	}
+}
+
+// The API token may be stored under api_token instead of token.
+func TestSeedOutpostAPITokenFallbackField(t *testing.T) {
+	v := newVaultStub()
+	v.tokenField = "api_token"
+	a := newAuthentikStub()
+	vs, as := v.server(t), a.server(t)
+
+	if _, err := SeedOutpost(opts(vs.URL, as.URL)); err != nil {
+		t.Fatalf("SeedOutpost with api_token field: %v", err)
+	}
+	if a.sawBearer != "Bearer "+testAPIToken {
+		t.Errorf("Authorization = %q, want the api_token value", a.sawBearer)
+	}
+}
+
+func TestSeedOutpostCustomDestKey(t *testing.T) {
+	v := newVaultStub()
+	a := newAuthentikStub()
+	vs, as := v.server(t), a.server(t)
+
+	o := opts(vs.URL, as.URL)
+	o.DestKey = "outpost-token"
+	if _, err := SeedOutpost(o); err != nil {
+		t.Fatalf("SeedOutpost: %v", err)
+	}
+	if len(v.writes) != 1 || v.writes[0]["outpost-token"] != testOutpostKey {
+		t.Errorf("written data = %v, want the key under outpost-token", v.writes)
+	}
+}
+
+func TestSeedOutpostLoginFailure(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()
+	a := newAuthentikStub()
+
+	_, err := SeedOutpost(opts(vs.URL, a.server(t).URL))
+	if err == nil {
+		t.Fatal("SeedOutpost() = 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 TestSeedOutpostKVReadDenied(t *testing.T) {
+	v := newVaultStub()
+	v.readStatus = http.StatusForbidden
+	a := newAuthentikStub()
+	vs, as := v.server(t), a.server(t)
+
+	_, err := SeedOutpost(opts(vs.URL, as.URL))
+	if err == nil {
+		t.Fatal("SeedOutpost() = nil, want a KV read error")
+	}
+	msg := err.Error()
+	if !strings.Contains(msg, testTokenPath) || !strings.Contains(msg, "policy") {
+		t.Errorf("error = %v, want it to name the token path and point at the policy", err)
+	}
+	if strings.Contains(msg, "does not exist") {
+		t.Errorf("error = %v, denied must not be reported as missing", err)
+	}
+}
+
+func TestSeedOutpostKVReadNotFound(t *testing.T) {
+	v := newVaultStub()
+	v.readStatus = http.StatusNotFound
+	a := newAuthentikStub()
+	vs, as := v.server(t), a.server(t)
+
+	_, err := SeedOutpost(opts(vs.URL, as.URL))
+	if err == nil {
+		t.Fatal("SeedOutpost() = nil, want a missing-secret error")
+	}
+	if !strings.Contains(err.Error(), "does not exist") {
+		t.Errorf("error = %v, want it to say the secret does not exist", err)
+	}
+}
+
+func TestSeedOutpostMissingTokenField(t *testing.T) {
+	v := newVaultStub()
+	v.tokenField = "password"
+	a := newAuthentikStub()
+	vs, as := v.server(t), a.server(t)
+
+	_, err := SeedOutpost(opts(vs.URL, as.URL))
+	if err == nil {
+		t.Fatal("SeedOutpost() = nil, want an error for a secret with no token field")
+	}
+	if !strings.Contains(err.Error(), "api_token") {
+		t.Errorf("error = %v, want it to name the accepted fields", err)
+	}
+}
+
+// A substring hit that is not the exact name must not be accepted.
+func TestSeedOutpostNotFound(t *testing.T) {
+	v := newVaultStub()
+	a := newAuthentikStub()
+	a.results = `{"pk":"1","name":"` + testOutpostName + `-staging","token_identifier":"other"}`
+	vs, as := v.server(t), a.server(t)
+
+	_, err := SeedOutpost(opts(vs.URL, as.URL))
+	if err == nil {
+		t.Fatal("SeedOutpost() = nil, want an outpost-not-found error")
+	}
+	msg := err.Error()
+	if !strings.Contains(msg, "no outpost named") || !strings.Contains(msg, "terraform") {
+		t.Errorf("error = %v, want it to report the missing outpost and mention terraform", err)
+	}
+	if len(v.writes) != 0 {
+		t.Errorf("wrote %v, want no KV write when the outpost is missing", v.writes)
+	}
+}
+
+func TestSeedOutpostViewKeyFailure(t *testing.T) {
+	v := newVaultStub()
+	a := newAuthentikStub()
+	a.viewKeyStatus = http.StatusForbidden
+	vs, as := v.server(t), a.server(t)
+
+	_, err := SeedOutpost(opts(vs.URL, as.URL))
+	if err == nil {
+		t.Fatal("SeedOutpost() = nil, want a view_key error")
+	}
+	if !strings.Contains(err.Error(), testTokenIdent) {
+		t.Errorf("error = %v, want it to name the token identifier", err)
+	}
+	if len(v.writes) != 0 {
+		t.Errorf("wrote %v, want no KV write when view_key fails", v.writes)
+	}
+}
+
+func TestSeedOutpostViewKeyEmpty(t *testing.T) {
+	v := newVaultStub()
+	a := newAuthentikStub()
+	a.viewKeyBody = `{}`
+	vs, as := v.server(t), a.server(t)
+
+	if _, err := SeedOutpost(opts(vs.URL, as.URL)); err == nil {
+		t.Fatal("SeedOutpost() = nil, want an error when view_key returns no key")
+	}
+}
+
+func TestSeedOutpostKVWriteDenied(t *testing.T) {
+	v := newVaultStub()
+	v.writeStatus = http.StatusForbidden
+	a := newAuthentikStub()
+	vs, as := v.server(t), a.server(t)
+
+	_, err := SeedOutpost(opts(vs.URL, as.URL))
+	if err == nil {
+		t.Fatal("SeedOutpost() = nil, want a KV write error")
+	}
+	msg := err.Error()
+	if !strings.Contains(msg, testDestPath) || !strings.Contains(msg, "create/update") {
+		t.Errorf("error = %v, want it to name the dest path and the missing capability", err)
+	}
+}
+
+// No failure path may leak the API token or the outpost key into the error.
+func TestSeedOutpostErrorsNeverLeakSecrets(t *testing.T) {
+	cases := map[string]func(*vaultStub, *authentikStub){
+		"read denied":   func(v *vaultStub, a *authentikStub) { v.readStatus = http.StatusForbidden },
+		"write denied":  func(v *vaultStub, a *authentikStub) { v.writeStatus = http.StatusForbidden },
+		"view_key fail": func(v *vaultStub, a *authentikStub) { a.viewKeyStatus = http.StatusInternalServerError },
+		"outpost gone":  func(v *vaultStub, a *authentikStub) { a.results = "" },
+	}
+	for name, mutate := range cases {
+		t.Run(name, func(t *testing.T) {
+			v, a := newVaultStub(), newAuthentikStub()
+			mutate(v, a)
+			vs, as := v.server(t), a.server(t)
+			_, err := SeedOutpost(opts(vs.URL, as.URL))
+			if err == nil {
+				t.Fatal("SeedOutpost() = nil, want an error")
+			}
+			for _, secret := range []string{testAPIToken, testOutpostKey} {
+				if strings.Contains(err.Error(), secret) {
+					t.Errorf("error %q leaks a secret", err)
+				}
+			}
+		})
+	}
+}
@@ -1,8 +1,8 @@
-// Package agent holds the plumbing shared by the agent-tools CLIs (agentpr and
-// watchpr): obtaining a Gitea token via Vault AppRole, talking to the Gitea
-// API, parsing PR references, and deciding when a watched PR changed
-// meaningfully. Both tools acquire their Gitea token the same way, so that
-// logic lives here once.
+// Package agent holds the plumbing shared by the agent-tools CLIs (agentpr,
+// watchpr, agentws and agentvault): the Vault AppRole login and its KV-v2
+// client, talking to the Gitea and Authentik APIs, parsing PR references, and
+// deciding when a watched PR changed meaningfully. Every tool authenticates to
+// Vault the same way, so that logic lives here once.
 package agent

 import (
@@ -23,6 +23,9 @@ const (
 	// DefaultAgentLogin is the Gitea login of the agent whose own comments are
 	// ignored by watchpr. Overridable via AGENT_LOGIN.
 	DefaultAgentLogin = "unkin-agent"
+	// DefaultAuthentikURL is the Authentik base URL used when AUTHENTIK_URL is
+	// unset. identity.unkin.net has no DNS record; the k8s name is the real one.
+	DefaultAuthentikURL = "https://identity.k8s.syd1.au.unkin.net"
 )

 // VaultAddr returns the configured Vault address (env VAULT_ADDR or the default).
@@ -59,6 +62,15 @@ func AgentLogin() string {
 	return DefaultAgentLogin
 }

+// AuthentikURL returns the configured Authentik base URL (env AUTHENTIK_URL or
+// the default).
+func AuthentikURL() string {
+	if v := os.Getenv("AUTHENTIK_URL"); v != "" {
+		return v
+	}
+	return DefaultAuthentikURL
+}
+
 var (
 	tokenOnce  sync.Once
 	tokenValue string
@@ -0,0 +1,134 @@
+package agent
+
+import (
+	"bytes"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io"
+	"net/http"
+	"strings"
+)
+
+const (
+	// DefaultKVMount is the KV-v2 mount holding agent-facing secrets.
+	DefaultKVMount = "kv"
+)
+
+var (
+	// ErrVaultDenied marks a 403 from Vault (the AppRole policy lacks the capability).
+	ErrVaultDenied = errors.New("permission denied")
+	// ErrVaultNotFound marks a 404 from Vault (mount or secret does not exist).
+	ErrVaultNotFound = errors.New("not found")
+)
+
+// VaultClient issues authenticated requests against Vault/OpenBao using a token
+// obtained from the agent AppRole.
+type VaultClient struct {
+	Addr  string
+	Token string
+	HTTP  *http.Client
+}
+
+// NewVaultClient performs the AppRole login (role_id only, no secret_id) and
+// returns a client bound to the resulting client_token.
+func NewVaultClient(addr, roleID string) (*VaultClient, error) {
+	token, err := approleLogin(addr, roleID)
+	if err != nil {
+		return nil, err
+	}
+	return &VaultClient{Addr: addr, Token: token, HTTP: httpClient}, nil
+}
+
+func (c *VaultClient) do(method, path string, body any, out any) error {
+	var reader io.Reader
+	if body != nil {
+		b, err := json.Marshal(body)
+		if err != nil {
+			return err
+		}
+		reader = bytes.NewReader(b)
+	}
+	url := strings.TrimRight(c.Addr, "/") + path
+	req, err := http.NewRequest(method, url, reader)
+	if err != nil {
+		return err
+	}
+	req.Header.Set("X-Vault-Token", c.Token)
+	if body != nil {
+		req.Header.Set("Content-Type", "application/json")
+	}
+
+	resp, err := c.HTTP.Do(req)
+	if err != nil {
+		return fmt.Errorf("vault %s %s: %w", method, path, err)
+	}
+	defer func() { _ = resp.Body.Close() }()
+	data, _ := io.ReadAll(resp.Body)
+
+	switch {
+	case resp.StatusCode == http.StatusForbidden:
+		return fmt.Errorf("vault %s %s: %w", method, path, ErrVaultDenied)
+	case resp.StatusCode == http.StatusNotFound:
+		return fmt.Errorf("vault %s %s: %w", method, path, ErrVaultNotFound)
+	case resp.StatusCode < 200 || resp.StatusCode >= 300:
+		return fmt.Errorf("vault %s %s: HTTP %d: %s", method, path, resp.StatusCode, strings.TrimSpace(string(data)))
+	}
+
+	if out != nil && len(data) > 0 {
+		// Response bodies here carry secret material, so decode failures never
+		// echo the body.
+		if err := json.Unmarshal(data, out); err != nil {
+			return fmt.Errorf("vault %s %s: decoding response: %w", method, path, err)
+		}
+	}
+	return nil
+}
+
+// kvDataPath builds the KV-v2 data path for a mount and secret path.
+func kvDataPath(mount, path string) string {
+	return "/v1/" + strings.Trim(mount, "/") + "/data/" + strings.Trim(path, "/")
+}
+
+// ReadKV returns the data map of a KV-v2 secret.
+func (c *VaultClient) ReadKV(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 {
+		return nil, err
+	}
+	if out.Data.Data == nil {
+		return nil, fmt.Errorf("vault read %s/%s: secret has no data", mount, path)
+	}
+	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) {
+	var out struct {
+		Data struct {
+			Version int `json:"version"`
+		} `json:"data"`
+	}
+	body := map[string]any{"data": data}
+	if err := c.do(http.MethodPost, kvDataPath(mount, path), body, &out); err != nil {
+		return 0, err
+	}
+	if out.Data.Version == 0 {
+		return 0, fmt.Errorf("vault write %s/%s: no version in response", mount, path)
+	}
+	return out.Data.Version, nil
+}
+
+// StringField returns the first non-empty string value among the given keys.
+func StringField(data map[string]any, keys ...string) string {
+	for _, k := range keys {
+		if s, ok := data[k].(string); ok && s != "" {
+			return s
+		}
+	}
+	return ""
+}