feat: deliver Sense audits to Bell (T-016)

Bell/README.md

@@ -1,13 +1,21 @@
-# Bell 事件存储基础
+# Bell 事件存储与内部审计入口
 
-Bell 当前只实现 M3 的事件域基础，不包含可部署 HTTP 服务：
+Bell 当前实现 M3 的事件域基础及 Sense 审计 relay 的最小内部 HTTP 服务：
 
 - Bell 在可信 ingress 内为不含 `id` 的候选事实生成 `evt_` ULID。
 - 最终事件同时通过冻结 v0.1 JSON Schema 与六项代码级断言。
 - PostgreSQL `bell.events` 保存不可变事实；后续 outcome 追加到 `bell.event_outcomes`。
-- `bell_runtime` 只拥有两张表的 `SELECT/INSERT`，没有 `UPDATE/DELETE/TRUNCATE` 或 migration owner 权限。
+- `bell_runtime` 对三张不可变事实表只有 `SELECT/INSERT`，没有 `UPDATE/DELETE/TRUNCATE` 或 migration owner 权限；仅可在短期 `audit_relay_receipts` 表查询、插入和清理过期收据。
+- `cmd/bell-api` 默认只监听 `127.0.0.1:8081`，接收 HMAC 签名的 `/internal/v1/audit-events:batch`，把脱敏设备操作事实追加到 `bell.audit_events`。
+- `(key_id, nonce)` 收据保存 10 分钟；相同摘要重放原结果，不同摘要返回冲突。非回环监听必须配置 TLS 证书和私钥。
 
-Brain→Bell transport、认证、公共事件 API、规则、Alert 和证据对象存储仍需后续任务冻结，不能把 `internal/event` 的 Go 类型当成公共网络协议。
+Brain→Bell transport、公共认证/事件 API、规则、Alert 和证据对象存储仍需后续任务冻结。审计 relay 只服务 Sense，不得把 `internal/event` 的 Go 类型或该 HMAC 适配器当成公共协议。
+
+启动内部 receiver 前必须私下设置 `BELL_DB_DSN` 和仓库外绝对路径 `BELL_AUDIT_KEYS_FILE`。远端监听还必须设置 `BELL_TLS_CERT_FILE`、`BELL_TLS_KEY_FILE`；仓库不保存 DSN、key 或证书：
+
+```powershell
+go -C Bell run ./cmd/bell-api
+```
 
 ## 验证
 

Bell/cmd/bell-api/main.go

@@ -0,0 +1,152 @@
+package main
+
+import (
+	"context"
+	"crypto/tls"
+	"errors"
+	"fmt"
+	"log/slog"
+	"net"
+	"net/http"
+	"os"
+	"os/signal"
+	"path/filepath"
+	"syscall"
+	"time"
+
+	"github.com/jackc/pgx/v5"
+	"github.com/jackc/pgx/v5/stdlib"
+
+	"yovision/bell/internal/audit"
+	"yovision/bell/internal/store"
+)
+
+var version = "dev"
+
+type configuration struct {
+	address string
+	dsn     string
+	keyFile string
+	tlsCert string
+	tlsKey  string
+}
+
+func main() {
+	logger := slog.New(slog.NewJSONHandler(os.Stdout, nil))
+	if err := run(logger); err != nil {
+		logger.Error("Bell stopped", "error", err)
+		os.Exit(1)
+	}
+}
+
+func loadConfiguration() (configuration, error) {
+	value := configuration{
+		address: envOr("BELL_HTTP_ADDR", "127.0.0.1:8081"),
+		dsn:     os.Getenv("BELL_DB_DSN"),
+		keyFile: os.Getenv("BELL_AUDIT_KEYS_FILE"),
+		tlsCert: os.Getenv("BELL_TLS_CERT_FILE"),
+		tlsKey:  os.Getenv("BELL_TLS_KEY_FILE"),
+	}
+	if value.dsn == "" {
+		return configuration{}, errors.New("BELL_DB_DSN is required")
+	}
+	if value.keyFile == "" || !filepath.IsAbs(value.keyFile) {
+		return configuration{}, errors.New("BELL_AUDIT_KEYS_FILE must be an absolute external path")
+	}
+	host, _, err := net.SplitHostPort(value.address)
+	if err != nil {
+		return configuration{}, errors.New("invalid BELL_HTTP_ADDR")
+	}
+	ip := net.ParseIP(host)
+	loopback := host == "localhost" || (ip != nil && ip.IsLoopback())
+	if !loopback && (value.tlsCert == "" || value.tlsKey == "" || !filepath.IsAbs(value.tlsCert) || !filepath.IsAbs(value.tlsKey)) {
+		return configuration{}, errors.New("non-loopback Bell bind requires absolute TLS certificate and key paths")
+	}
+	if (value.tlsCert == "") != (value.tlsKey == "") {
+		return configuration{}, errors.New("Bell TLS certificate and key must be configured together")
+	}
+	return value, nil
+}
+
+func run(logger *slog.Logger) error {
+	cfg, err := loadConfiguration()
+	if err != nil {
+		return err
+	}
+	pgConfig, err := pgx.ParseConfig(cfg.dsn)
+	if err != nil {
+		return errors.New("invalid Bell postgres DSN")
+	}
+	if pgConfig.RuntimeParams == nil {
+		pgConfig.RuntimeParams = make(map[string]string)
+	}
+	pgConfig.RuntimeParams["application_name"] = "yovision-bell"
+	db := stdlib.OpenDB(*pgConfig)
+	db.SetMaxOpenConns(16)
+	db.SetMaxIdleConns(4)
+	db.SetConnMaxLifetime(30 * time.Minute)
+	defer db.Close()
+
+	ctx, stop := signal.NotifyContext(context.Background(), os.Interrupt, syscall.SIGTERM)
+	defer stop()
+	repository, err := store.OpenPostgres(ctx, db)
+	if err != nil {
+		return err
+	}
+	if err := repository.AuditRelayReady(ctx); err != nil {
+		return err
+	}
+	keys, err := audit.LoadKeys(cfg.keyFile)
+	if err != nil {
+		return err
+	}
+	handler, err := audit.NewHandler(repository, keys)
+	if err != nil {
+		return err
+	}
+	mux := http.NewServeMux()
+	mux.Handle(audit.RelayPath, handler)
+	mux.HandleFunc("GET /healthz", func(writer http.ResponseWriter, _ *http.Request) {
+		writeStatus(writer, http.StatusOK, "ok")
+	})
+	mux.HandleFunc("GET /readyz", func(writer http.ResponseWriter, request *http.Request) {
+		if err := repository.AuditRelayReady(request.Context()); err != nil {
+			writeStatus(writer, http.StatusServiceUnavailable, "not_ready")
+			return
+		}
+		writeStatus(writer, http.StatusOK, "ready")
+	})
+	server := &http.Server{Addr: cfg.address, Handler: mux, ReadHeaderTimeout: 5 * time.Second, ReadTimeout: 15 * time.Second, WriteTimeout: 15 * time.Second, IdleTimeout: 60 * time.Second, TLSConfig: &tls.Config{MinVersion: tls.VersionTLS12}}
+	serverErrors := make(chan error, 1)
+	go func() {
+		logger.Info("Bell listening", "address", cfg.address, "version", version, "tls_enabled", cfg.tlsCert != "")
+		if cfg.tlsCert != "" {
+			serverErrors <- server.ListenAndServeTLS(cfg.tlsCert, cfg.tlsKey)
+			return
+		}
+		serverErrors <- server.ListenAndServe()
+	}()
+	select {
+	case <-ctx.Done():
+	case serverErr := <-serverErrors:
+		if !errors.Is(serverErr, http.ErrServerClosed) {
+			return fmt.Errorf("serve Bell HTTP: %w", serverErr)
+		}
+	}
+	shutdownContext, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+	defer cancel()
+	return server.Shutdown(shutdownContext)
+}
+
+func writeStatus(writer http.ResponseWriter, status int, value string) {
+	writer.Header().Set("Content-Type", "application/json")
+	writer.WriteHeader(status)
+	_, _ = fmt.Fprintf(writer, `{"status":%q}`, value)
+}
+
+func envOr(name, fallback string) string {
+	if value := os.Getenv(name); value != "" {
+		return value
+	}
+	return fallback
+}

Bell/cmd/bell-api/main_test.go

@@ -0,0 +1,33 @@
+package main
+
+import (
+	"path/filepath"
+	"testing"
+)
+
+func TestConfigurationRequiresDatabaseAndExternalKey(t *testing.T) {
+	t.Setenv("BELL_DB_DSN", "")
+	t.Setenv("BELL_AUDIT_KEYS_FILE", "")
+	if _, err := loadConfiguration(); err == nil {
+		t.Fatal("missing Bell database was accepted")
+	}
+	t.Setenv("BELL_DB_DSN", "postgres://bell@127.0.0.1/yovision")
+	t.Setenv("BELL_AUDIT_KEYS_FILE", "relative.json")
+	if _, err := loadConfiguration(); err == nil {
+		t.Fatal("relative Bell key file was accepted")
+	}
+}
+
+func TestConfigurationRequiresTLSOutsideLoopback(t *testing.T) {
+	t.Setenv("BELL_DB_DSN", "postgres://bell@127.0.0.1/yovision")
+	t.Setenv("BELL_AUDIT_KEYS_FILE", filepath.Join(t.TempDir(), "keys.json"))
+	t.Setenv("BELL_HTTP_ADDR", "0.0.0.0:8081")
+	if _, err := loadConfiguration(); err == nil {
+		t.Fatal("remote plaintext Bell bind was accepted")
+	}
+	t.Setenv("BELL_TLS_CERT_FILE", filepath.Join(t.TempDir(), "server.crt"))
+	t.Setenv("BELL_TLS_KEY_FILE", filepath.Join(t.TempDir(), "server.key"))
+	if _, err := loadConfiguration(); err != nil {
+		t.Fatalf("remote TLS Bell bind rejected: %v", err)
+	}
+}

Bell/internal/audit/audit.go

@@ -0,0 +1,363 @@
+// Package audit authenticates and validates Sense audit relay batches.
+package audit
+
+import (
+	"bytes"
+	"context"
+	"crypto/hmac"
+	"crypto/sha256"
+	"encoding/base64"
+	"encoding/hex"
+	"encoding/json"
+	"errors"
+	"io"
+	"net/http"
+	"regexp"
+	"strconv"
+	"strings"
+	"time"
+	"unicode/utf8"
+)
+
+const (
+	RelayPath       = "/internal/v1/audit-events:batch"
+	MaxBatchSize    = 100
+	MaxBodyBytes    = 1 << 20
+	HeaderKeyID     = "X-YoVision-Key-Id"
+	HeaderTimestamp = "X-YoVision-Timestamp"
+	HeaderNonce     = "X-YoVision-Nonce"
+	HeaderSignature = "X-YoVision-Signature"
+)
+
+var ErrReplayConflict = errors.New("audit relay replay conflict")
+
+type Actor struct {
+	Type string `json:"type"`
+	ID   string `json:"id"`
+}
+
+type ProjectionVersions struct {
+	QuotaSourceVersion      *int64 `json:"quota_source_version"`
+	AreaPolicySourceVersion *int64 `json:"area_policy_source_version"`
+}
+
+type Event struct {
+	EventID             string             `json:"event_id"`
+	EventType           string             `json:"event_type"`
+	TenantID            string             `json:"tenant_id"`
+	SiteID              string             `json:"site_id"`
+	DeviceID            string             `json:"device_id"`
+	Actor               Actor              `json:"actor"`
+	Reason              *string            `json:"reason"`
+	TraceID             *string            `json:"trace_id"`
+	AggregateGeneration int64              `json:"aggregate_generation"`
+	ProjectionVersions  ProjectionVersions `json:"projection_versions"`
+	Data                json.RawMessage    `json:"data"`
+	OccurredAt          time.Time          `json:"occurred_at"`
+}
+
+type Envelope struct {
+	SchemaVersion int   `json:"schema_version"`
+	Event         Event `json:"event"`
+}
+
+type Result struct {
+	EventID   string  `json:"event_id"`
+	Status    string  `json:"status"`
+	ErrorCode *string `json:"error_code,omitempty"`
+}
+
+type BatchResponse struct {
+	Results []Result `json:"results"`
+}
+
+type Candidate struct {
+	Envelope   Envelope
+	RecordHash [sha256.Size]byte
+	ErrorCode  string
+}
+
+type Repository interface {
+	ProcessAuditBatch(context.Context, string, string, [sha256.Size]byte, []Candidate) ([]Result, error)
+}
+
+type Handler struct {
+	repository Repository
+	keys       map[string][]byte
+	now        func() time.Time
+}
+
+func NewHandler(repository Repository, keys map[string][]byte) (*Handler, error) {
+	if repository == nil || len(keys) == 0 {
+		return nil, errors.New("audit handler dependencies are required")
+	}
+	copyKeys := make(map[string][]byte, len(keys))
+	for id, secret := range keys {
+		if !keyIDPattern.MatchString(id) || len(secret) < 32 {
+			return nil, errors.New("invalid audit handler key")
+		}
+		copyKeys[id] = append([]byte(nil), secret...)
+	}
+	return &Handler{repository: repository, keys: copyKeys, now: time.Now}, nil
+}
+
+func (h *Handler) ServeHTTP(writer http.ResponseWriter, request *http.Request) {
+	if request.Method != http.MethodPost || request.URL.Path != RelayPath {
+		writeError(writer, http.StatusNotFound, "not_found")
+		return
+	}
+	body, err := io.ReadAll(io.LimitReader(request.Body, MaxBodyBytes+1))
+	if err != nil || len(body) > MaxBodyBytes {
+		writeError(writer, http.StatusRequestEntityTooLarge, "payload_too_large")
+		return
+	}
+	keyID := request.Header.Get(HeaderKeyID)
+	timestamp := request.Header.Get(HeaderTimestamp)
+	nonce := request.Header.Get(HeaderNonce)
+	provided := request.Header.Get(HeaderSignature)
+	secret, ok := h.keys[keyID]
+	seconds, timestampErr := strconv.ParseInt(timestamp, 10, 64)
+	nonceBytes, nonceErr := base64.RawURLEncoding.DecodeString(nonce)
+	signatureBytes, signatureErr := base64.RawURLEncoding.DecodeString(provided)
+	if !ok || timestampErr != nil || len(timestamp) < 10 || nonceErr != nil || len(nonceBytes) < 16 || len(nonceBytes) > 48 ||
+		signatureErr != nil || len(signatureBytes) != sha256.Size || absDuration(h.now().UTC().Sub(time.Unix(seconds, 0).UTC())) > 300*time.Second {
+		writeError(writer, http.StatusUnauthorized, "unauthorized")
+		return
+	}
+	expected := signature(secret, canonicalString(request.Method, request.URL.EscapedPath(), timestamp, nonce, body))
+	if !hmac.Equal(signatureBytes, expected) {
+		writeError(writer, http.StatusUnauthorized, "unauthorized")
+		return
+	}
+	candidates, err := decodeCandidates(body)
+	if err != nil {
+		writeError(writer, http.StatusBadRequest, "invalid_batch")
+		return
+	}
+	requestHash := sha256.Sum256(body)
+	results, err := h.repository.ProcessAuditBatch(request.Context(), keyID, nonce, requestHash, candidates)
+	if errors.Is(err, ErrReplayConflict) {
+		writeError(writer, http.StatusConflict, "replay_conflict")
+		return
+	}
+	if err != nil {
+		writeError(writer, http.StatusServiceUnavailable, "temporarily_unavailable")
+		return
+	}
+	writeJSON(writer, http.StatusOK, BatchResponse{Results: results})
+}
+
+func canonicalString(method, path, timestamp, nonce string, body []byte) string {
+	digest := sha256.Sum256(body)
+	return strings.Join([]string{method, path, timestamp, nonce, hex.EncodeToString(digest[:])}, "\n")
+}
+
+func signature(secret []byte, canonical string) []byte {
+	mac := hmac.New(sha256.New, secret)
+	_, _ = mac.Write([]byte(canonical))
+	return mac.Sum(nil)
+}
+
+func absDuration(value time.Duration) time.Duration {
+	if value < 0 {
+		return -value
+	}
+	return value
+}
+
+type rawBatch struct {
+	Events []json.RawMessage `json:"events"`
+}
+
+func decodeCandidates(body []byte) ([]Candidate, error) {
+	decoder := json.NewDecoder(bytes.NewReader(body))
+	decoder.DisallowUnknownFields()
+	var batch rawBatch
+	if err := decoder.Decode(&batch); err != nil || len(batch.Events) < 1 || len(batch.Events) > MaxBatchSize {
+		return nil, errors.New("invalid audit batch")
+	}
+	var trailing any
+	if err := decoder.Decode(&trailing); !errors.Is(err, io.EOF) {
+		return nil, errors.New("invalid audit batch trailing data")
+	}
+	values := make([]Candidate, len(batch.Events))
+	for index, raw := range batch.Events {
+		values[index].RecordHash = sha256.Sum256(raw)
+		if !hasExactEnvelopeShape(raw) {
+			values[index].ErrorCode = "schema_invalid"
+			continue
+		}
+		itemDecoder := json.NewDecoder(bytes.NewReader(raw))
+		itemDecoder.DisallowUnknownFields()
+		if err := itemDecoder.Decode(&values[index].Envelope); err != nil {
+			values[index].ErrorCode = "schema_invalid"
+			continue
+		}
+		values[index].ErrorCode = validateEnvelope(values[index].Envelope)
+	}
+	return values, nil
+}
+
+var (
+	eventIDPattern   = regexp.MustCompile(`^audit_[0-9a-f]{32}$`)
+	logicalIDPattern = regexp.MustCompile(`^[A-Za-z0-9][A-Za-z0-9._:-]{0,127}$`)
+	keyIDPattern     = regexp.MustCompile(`^[A-Za-z0-9][A-Za-z0-9._-]{0,63}$`)
+)
+
+func validateEnvelope(value Envelope) string {
+	event := value.Event
+	if (value.SchemaVersion != 1 && value.SchemaVersion != 2) || !eventIDPattern.MatchString(event.EventID) ||
+		!logicalIDPattern.MatchString(event.TenantID) || !logicalIDPattern.MatchString(event.SiteID) || !logicalIDPattern.MatchString(event.DeviceID) ||
+		event.AggregateGeneration < 1 || event.OccurredAt.IsZero() || strings.TrimSpace(event.Actor.ID) == "" || utf8.RuneCountInString(event.Actor.ID) > 200 ||
+		(event.Actor.Type != "user" && event.Actor.Type != "service" && event.Actor.Type != "system") ||
+		(event.Reason != nil && utf8.RuneCountInString(*event.Reason) > 500) || (event.TraceID != nil && utf8.RuneCountInString(*event.TraceID) > 128) ||
+		(event.ProjectionVersions.QuotaSourceVersion != nil && *event.ProjectionVersions.QuotaSourceVersion < 1) ||
+		(event.ProjectionVersions.AreaPolicySourceVersion != nil && *event.ProjectionVersions.AreaPolicySourceVersion < 1) {
+		return "schema_invalid"
+	}
+	if event.EventType != "device.created" && event.EventType != "device.desired_state.accepted" &&
+		(event.EventType != "device.configuration.accepted" || value.SchemaVersion != 2) {
+		return "schema_invalid"
+	}
+	var data map[string]any
+	if err := json.Unmarshal(event.Data, &data); err != nil || data == nil {
+		return "schema_invalid"
+	}
+	expected := map[string]string{
+		"device.created":                "device_created",
+		"device.desired_state.accepted": "desired_state_accepted",
+		"device.configuration.accepted": "configuration_accepted",
+	}[event.EventType]
+	if data["kind"] != expected || !validateData(event.EventType, data) || containsSensitiveKey(data) {
+		return "payload_invalid"
+	}
+	return ""
+}
+
+func hasExactEnvelopeShape(raw []byte) bool {
+	var envelope map[string]json.RawMessage
+	if err := json.Unmarshal(raw, &envelope); err != nil || !exactRawKeys(envelope, "schema_version", "event") {
+		return false
+	}
+	var event map[string]json.RawMessage
+	if err := json.Unmarshal(envelope["event"], &event); err != nil || !exactRawKeys(event,
+		"event_id", "event_type", "tenant_id", "site_id", "device_id", "actor", "reason", "trace_id",
+		"aggregate_generation", "projection_versions", "data", "occurred_at",
+	) {
+		return false
+	}
+	var actor, projections map[string]json.RawMessage
+	return json.Unmarshal(event["actor"], &actor) == nil && exactRawKeys(actor, "type", "id") &&
+		json.Unmarshal(event["projection_versions"], &projections) == nil && exactRawKeys(projections, "quota_source_version", "area_policy_source_version")
+}
+
+func exactRawKeys(value map[string]json.RawMessage, expected ...string) bool {
+	if len(value) != len(expected) {
+		return false
+	}
+	for _, key := range expected {
+		if _, exists := value[key]; !exists {
+			return false
+		}
+	}
+	return true
+}
+
+func validateData(eventType string, data map[string]any) bool {
+	switch eventType {
+	case "device.created":
+		if !exactAnyKeys(data, "kind", "area_id", "modality", "capabilities", "desired_state") || !logicalIDPattern.MatchString(stringValue(data["area_id"])) {
+			return false
+		}
+		if !member(stringValue(data["modality"]), "video", "radar", "contact", "button", "wearable", "other") || !member(stringValue(data["desired_state"]), "disabled", "enabled") {
+			return false
+		}
+		return validStringSet(data["capabilities"], 16, "video_capture", "audio_capture", "spatial_rule", "telemetry")
+	case "device.desired_state.accepted":
+		if !exactAnyKeys(data, "kind", "previous_desired_state", "desired_state", "changed") {
+			return false
+		}
+		_, changed := data["changed"].(bool)
+		return changed && member(stringValue(data["previous_desired_state"]), "disabled", "enabled") && member(stringValue(data["desired_state"]), "disabled", "enabled")
+	case "device.configuration.accepted":
+		if !exactAnyKeys(data, "kind", "changed", "changed_fields", "area_id") || !logicalIDPattern.MatchString(stringValue(data["area_id"])) {
+			return false
+		}
+		_, changed := data["changed"].(bool)
+		return changed && validStringSet(data["changed_fields"], 5, "name", "area_id", "endpoint_ref", "credential_ref", "profile_token")
+	default:
+		return false
+	}
+}
+
+func exactAnyKeys(value map[string]any, expected ...string) bool {
+	if len(value) != len(expected) {
+		return false
+	}
+	for _, key := range expected {
+		if _, exists := value[key]; !exists {
+			return false
+		}
+	}
+	return true
+}
+
+func stringValue(value any) string {
+	result, _ := value.(string)
+	return result
+}
+
+func member(value string, allowed ...string) bool {
+	for _, candidate := range allowed {
+		if value == candidate {
+			return true
+		}
+	}
+	return false
+}
+
+func validStringSet(value any, maximum int, allowed ...string) bool {
+	items, ok := value.([]any)
+	if !ok || len(items) > maximum {
+		return false
+	}
+	seen := make(map[string]bool, len(items))
+	for _, item := range items {
+		text, ok := item.(string)
+		if !ok || !member(text, allowed...) || seen[text] {
+			return false
+		}
+		seen[text] = true
+	}
+	return true
+}
+
+func containsSensitiveKey(value any) bool {
+	forbidden := map[string]bool{"password": true, "stream_uri": true, "mediamtx_config": true}
+	switch typed := value.(type) {
+	case map[string]any:
+		for key, child := range typed {
+			if forbidden[strings.ToLower(key)] || containsSensitiveKey(child) {
+				return true
+			}
+		}
+	case []any:
+		for _, child := range typed {
+			if containsSensitiveKey(child) {
+				return true
+			}
+		}
+	}
+	return false
+}
+
+func writeError(writer http.ResponseWriter, status int, code string) {
+	writeJSON(writer, status, map[string]string{"error": code})
+}
+
+func writeJSON(writer http.ResponseWriter, status int, value any) {
+	writer.Header().Set("Content-Type", "application/json")
+	writer.Header().Set("Cache-Control", "no-store")
+	writer.WriteHeader(status)
+	_ = json.NewEncoder(writer).Encode(value)
+}

Bell/internal/audit/audit_test.go

@@ -0,0 +1,105 @@
+package audit
+
+import (
+	"bytes"
+	"context"
+	"crypto/sha256"
+	"encoding/base64"
+	"encoding/json"
+	"net/http"
+	"net/http/httptest"
+	"strconv"
+	"testing"
+	"time"
+)
+
+type recordingRepository struct {
+	candidates []Candidate
+	results    []Result
+	err        error
+}
+
+func (r *recordingRepository) ProcessAuditBatch(_ context.Context, _, _ string, _ [sha256.Size]byte, values []Candidate) ([]Result, error) {
+	r.candidates = values
+	return r.results, r.err
+}
+
+func validBody(t *testing.T) []byte {
+	t.Helper()
+	value := map[string]any{"events": []any{map[string]any{
+		"schema_version": 1,
+		"event": map[string]any{
+			"event_id": "audit_00000000000000000000000000000001", "event_type": "device.created",
+			"tenant_id": "tenant", "site_id": "site", "device_id": "camera-1",
+			"actor": map[string]any{"type": "system", "id": "sense"}, "reason": nil, "trace_id": nil,
+			"aggregate_generation": 1,
+			"projection_versions":  map[string]any{"quota_source_version": 1, "area_policy_source_version": 1},
+			"data":                 map[string]any{"kind": "device_created", "area_id": "area", "modality": "video", "capabilities": []any{"video_capture"}, "desired_state": "enabled"},
+			"occurred_at":          "2026-08-11T00:00:00Z",
+		},
+	}}}
+	raw, err := json.Marshal(value)
+	if err != nil {
+		t.Fatal(err)
+	}
+	return raw
+}
+
+func signedRequest(t *testing.T, body, secret []byte, timestamp time.Time, nonce string) *http.Request {
+	t.Helper()
+	request := httptest.NewRequest(http.MethodPost, RelayPath, bytes.NewReader(body))
+	stamp := strconv.FormatInt(timestamp.Unix(), 10)
+	request.Header.Set(HeaderKeyID, "sense-a")
+	request.Header.Set(HeaderTimestamp, stamp)
+	request.Header.Set(HeaderNonce, nonce)
+	request.Header.Set(HeaderSignature, base64.RawURLEncoding.EncodeToString(signature(secret, canonicalString(http.MethodPost, RelayPath, stamp, nonce, body))))
+	return request
+}
+
+func TestHandlerAuthenticatesAndReturnsPerItemResults(t *testing.T) {
+	secret := bytes.Repeat([]byte{3}, 32)
+	repository := &recordingRepository{results: []Result{{EventID: "audit_00000000000000000000000000000001", Status: "accepted"}}}
+	handler, err := NewHandler(repository, map[string][]byte{"sense-a": secret})
+	if err != nil {
+		t.Fatal(err)
+	}
+	now := time.Date(2026, 8, 11, 0, 1, 0, 0, time.UTC)
+	handler.now = func() time.Time { return now }
+	response := httptest.NewRecorder()
+	handler.ServeHTTP(response, signedRequest(t, validBody(t), secret, now, "AAAAAAAAAAAAAAAAAAAAAA"))
+	if response.Code != http.StatusOK || len(repository.candidates) != 1 || repository.candidates[0].ErrorCode != "" {
+		t.Fatalf("valid batch rejected: status=%d candidates=%+v", response.Code, repository.candidates)
+	}
+}
+
+func TestHandlerRejectsStaleOrTamperedRequests(t *testing.T) {
+	secret := bytes.Repeat([]byte{4}, 32)
+	repository := &recordingRepository{}
+	handler, _ := NewHandler(repository, map[string][]byte{"sense-a": secret})
+	now := time.Date(2026, 8, 11, 0, 10, 0, 0, time.UTC)
+	handler.now = func() time.Time { return now }
+	for _, request := range []*http.Request{
+		signedRequest(t, validBody(t), secret, now.Add(-301*time.Second), "BBBBBBBBBBBBBBBBBBBBBB"),
+		signedRequest(t, append(validBody(t), ' '), bytes.Repeat([]byte{5}, 32), now, "CCCCCCCCCCCCCCCCCCCCCC"),
+	} {
+		response := httptest.NewRecorder()
+		handler.ServeHTTP(response, request)
+		if response.Code != http.StatusUnauthorized {
+			t.Fatalf("unsafe request returned %d", response.Code)
+		}
+	}
+}
+
+func TestDecodeCandidatesRejectsSensitiveItemWithoutRejectingBatch(t *testing.T) {
+	body := validBody(t)
+	var value map[string]any
+	_ = json.Unmarshal(body, &value)
+	events := value["events"].([]any)
+	event := events[0].(map[string]any)["event"].(map[string]any)
+	event["data"].(map[string]any)["password"] = "must-not-persist"
+	body, _ = json.Marshal(value)
+	candidates, err := decodeCandidates(body)
+	if err != nil || len(candidates) != 1 || candidates[0].ErrorCode != "payload_invalid" {
+		t.Fatalf("unexpected per-item validation: %+v %v", candidates, err)
+	}
+}

Bell/internal/audit/key.go

@@ -0,0 +1,47 @@
+package audit
+
+import (
+	"bytes"
+	"encoding/base64"
+	"encoding/json"
+	"errors"
+	"io"
+	"os"
+)
+
+type keyDocument struct {
+	Version int `json:"version"`
+	Keys    []struct {
+		KeyID  string `json:"key_id"`
+		Secret string `json:"secret_base64url"`
+	} `json:"keys"`
+}
+
+func LoadKeys(path string) (map[string][]byte, error) {
+	raw, err := os.ReadFile(path)
+	if err != nil {
+		return nil, errors.New("read Bell audit key file")
+	}
+	var document keyDocument
+	decoder := json.NewDecoder(bytes.NewReader(raw))
+	decoder.DisallowUnknownFields()
+	if err := decoder.Decode(&document); err != nil || document.Version != 1 || len(document.Keys) == 0 {
+		return nil, errors.New("invalid Bell audit key file")
+	}
+	var trailing any
+	if err := decoder.Decode(&trailing); !errors.Is(err, io.EOF) {
+		return nil, errors.New("invalid Bell audit key file")
+	}
+	values := make(map[string][]byte, len(document.Keys))
+	for _, item := range document.Keys {
+		secret, err := base64.RawURLEncoding.DecodeString(item.Secret)
+		if err != nil || !keyIDPattern.MatchString(item.KeyID) || len(secret) < 32 {
+			return nil, errors.New("invalid Bell audit key")
+		}
+		if _, exists := values[item.KeyID]; exists {
+			return nil, errors.New("duplicate Bell audit key ID")
+		}
+		values[item.KeyID] = secret
+	}
+	return values, nil
+}

Bell/internal/store/audit_postgres.go

@@ -0,0 +1,138 @@
+package store
+
+import (
+	"bytes"
+	"context"
+	"crypto/sha256"
+	"database/sql"
+	"encoding/json"
+	"errors"
+	"fmt"
+
+	"yovision/bell/internal/audit"
+)
+
+func (p *Postgres) AuditRelayReady(ctx context.Context) error {
+	var version int64
+	if err := p.db.QueryRowContext(ctx, `SELECT COALESCE(MAX(version), 0) FROM bell.schema_migrations`).Scan(&version); err != nil || version < 4 {
+		return errors.New("postgres Bell schema migration v4 is required for audit relay")
+	}
+	var auditSelect, auditInsert, auditUpdate, auditDelete, auditTruncate bool
+	var receiptUse bool
+	if err := p.db.QueryRowContext(ctx, `SELECT
+		has_table_privilege(current_user, 'bell.audit_events', 'SELECT'),
+		has_table_privilege(current_user, 'bell.audit_events', 'INSERT'),
+		has_table_privilege(current_user, 'bell.audit_events', 'UPDATE'),
+		has_table_privilege(current_user, 'bell.audit_events', 'DELETE'),
+		has_table_privilege(current_user, 'bell.audit_events', 'TRUNCATE'),
+		has_table_privilege(current_user, 'bell.audit_relay_receipts', 'SELECT,INSERT,DELETE')`).Scan(
+		&auditSelect, &auditInsert, &auditUpdate, &auditDelete, &auditTruncate, &receiptUse,
+	); err != nil {
+		return errors.New("verify Bell audit relay privileges")
+	}
+	if !auditSelect || !auditInsert || auditUpdate || auditDelete || auditTruncate || !receiptUse {
+		return errors.New("Bell audit relay privileges violate append-only boundary")
+	}
+	return nil
+}
+
+func (p *Postgres) ProcessAuditBatch(
+	ctx context.Context,
+	keyID, nonce string,
+	requestHash [sha256.Size]byte,
+	candidates []audit.Candidate,
+) ([]audit.Result, error) {
+	if len(candidates) < 1 || len(candidates) > audit.MaxBatchSize {
+		return nil, errors.New("invalid audit candidate batch")
+	}
+	tx, err := p.db.BeginTx(ctx, nil)
+	if err != nil {
+		return nil, errors.New("begin Bell audit batch")
+	}
+	defer tx.Rollback()
+	if _, err := tx.ExecContext(ctx, `SELECT pg_advisory_xact_lock(hashtext($1), hashtext($2))`, keyID, nonce); err != nil {
+		return nil, errors.New("lock Bell audit receipt")
+	}
+	if _, err := tx.ExecContext(ctx, `DELETE FROM bell.audit_relay_receipts WHERE expires_at <= clock_timestamp()`); err != nil {
+		return nil, errors.New("expire Bell audit receipts")
+	}
+	var existingHash, existingBody []byte
+	err = tx.QueryRowContext(ctx, `SELECT request_hash, response_body::text
+		FROM bell.audit_relay_receipts WHERE key_id=$1 AND nonce=$2`, keyID, nonce).Scan(&existingHash, &existingBody)
+	if err == nil {
+		if !bytes.Equal(existingHash, requestHash[:]) {
+			return nil, audit.ErrReplayConflict
+		}
+		var response audit.BatchResponse
+		if err := json.Unmarshal(existingBody, &response); err != nil {
+			return nil, errors.New("decode stored Bell audit receipt")
+		}
+		if err := tx.Commit(); err != nil {
+			return nil, errors.New("commit Bell audit replay")
+		}
+		return response.Results, nil
+	}
+	if !errors.Is(err, sql.ErrNoRows) {
+		return nil, errors.New("read Bell audit receipt")
+	}
+	results := make([]audit.Result, 0, len(candidates))
+	for _, candidate := range candidates {
+		if candidate.ErrorCode != "" {
+			code := candidate.ErrorCode
+			results = append(results, audit.Result{EventID: candidate.Envelope.Event.EventID, Status: "rejected", ErrorCode: &code})
+			continue
+		}
+		event := candidate.Envelope.Event
+		payload, err := json.Marshal(event)
+		if err != nil {
+			return nil, errors.New("encode Bell audit fact")
+		}
+		result, err := tx.ExecContext(ctx, `INSERT INTO bell.audit_events(
+			source_system, event_id, schema_version, event_type, tenant_id, site_id,
+			device_id, actor_type, actor_id, reason, trace_id, aggregate_generation,
+			quota_source_version, area_policy_source_version, payload, occurred_at, record_hash
+		) VALUES ('sense',$1,$2,$3,$4,$5,$6,$7,$8,$9,$10,$11,$12,$13,$14::jsonb,$15,$16)
+		ON CONFLICT (source_system,event_id) DO NOTHING`,
+			event.EventID, candidate.Envelope.SchemaVersion, event.EventType, event.TenantID,
+			event.SiteID, event.DeviceID, event.Actor.Type, event.Actor.ID, event.Reason,
+			event.TraceID, event.AggregateGeneration,
+			event.ProjectionVersions.QuotaSourceVersion,
+			event.ProjectionVersions.AreaPolicySourceVersion,
+			payload, event.OccurredAt, candidate.RecordHash[:])
+		if err != nil {
+			return nil, fmt.Errorf("insert Bell audit fact: %w", err)
+		}
+		affected, err := result.RowsAffected()
+		if err != nil {
+			return nil, errors.New("read Bell audit insert result")
+		}
+		if affected == 1 {
+			results = append(results, audit.Result{EventID: event.EventID, Status: "accepted"})
+			continue
+		}
+		var storedHash []byte
+		if err := tx.QueryRowContext(ctx, `SELECT record_hash FROM bell.audit_events
+			WHERE source_system='sense' AND event_id=$1`, event.EventID).Scan(&storedHash); err != nil {
+			return nil, errors.New("read existing Bell audit fact")
+		}
+		if bytes.Equal(storedHash, candidate.RecordHash[:]) {
+			results = append(results, audit.Result{EventID: event.EventID, Status: "duplicate"})
+		} else {
+			code := "id_conflict"
+			results = append(results, audit.Result{EventID: event.EventID, Status: "rejected", ErrorCode: &code})
+		}
+	}
+	encoded, err := json.Marshal(audit.BatchResponse{Results: results})
+	if err != nil {
+		return nil, errors.New("encode Bell audit response")
+	}
+	if _, err := tx.ExecContext(ctx, `INSERT INTO bell.audit_relay_receipts(
+		key_id, nonce, request_hash, response_status, response_body, expires_at
+	) VALUES ($1,$2,$3,200,$4::jsonb,clock_timestamp() + interval '10 minutes')`, keyID, nonce, requestHash[:], encoded); err != nil {
+		return nil, errors.New("insert Bell audit receipt")
+	}
+	if err := tx.Commit(); err != nil {
+		return nil, errors.New("commit Bell audit batch")
+	}
+	return results, nil
+}

Bell/internal/store/audit_postgres_test.go

@@ -0,0 +1,82 @@
+package store
+
+import (
+	"context"
+	"crypto/sha256"
+	"database/sql"
+	"encoding/json"
+	"errors"
+	"os"
+	"testing"
+	"time"
+
+	_ "github.com/jackc/pgx/v5/stdlib"
+
+	"yovision/bell/internal/audit"
+)
+
+func auditCandidate(t *testing.T, eventID, actorID string) audit.Candidate {
+	t.Helper()
+	data := json.RawMessage(`{"kind":"device_created","area_id":"area","modality":"video","capabilities":["video_capture"],"desired_state":"enabled"}`)
+	value := audit.Envelope{SchemaVersion: 1, Event: audit.Event{
+		EventID: eventID, EventType: "device.created", TenantID: "tenant", SiteID: "site", DeviceID: "camera-1",
+		Actor: audit.Actor{Type: "system", ID: actorID}, AggregateGeneration: 1,
+		ProjectionVersions: audit.ProjectionVersions{}, Data: data, OccurredAt: time.Date(2026, 8, 11, 0, 0, 0, 0, time.UTC),
+	}}
+	raw, err := json.Marshal(value)
+	if err != nil {
+		t.Fatal(err)
+	}
+	return audit.Candidate{Envelope: value, RecordHash: sha256.Sum256(raw)}
+}
+
+func TestPostgresAuditBatchReceiptAndImmutableFact(t *testing.T) {
+	dsn := os.Getenv("YOVISION_TEST_BELL_POSTGRES_DSN")
+	if dsn == "" {
+		t.Skip("YOVISION_TEST_BELL_POSTGRES_DSN is not set")
+	}
+	db, err := sql.Open("pgx", dsn)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer db.Close()
+	ctx := context.Background()
+	repository, err := OpenPostgres(ctx, db)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err := repository.AuditRelayReady(ctx); err != nil {
+		t.Fatal(err)
+	}
+
+	requestHash := sha256.Sum256([]byte("request-one"))
+	eventID := "audit_10000000000000000000000000000001"
+	results, err := repository.ProcessAuditBatch(ctx, "sense-a", "AAAAAAAAAAAAAAAAAAAAAA", requestHash, []audit.Candidate{auditCandidate(t, eventID, "sense")})
+	if err != nil || len(results) != 1 || results[0].Status != "accepted" {
+		t.Fatalf("first batch: %+v %v", results, err)
+	}
+	replayed, err := repository.ProcessAuditBatch(ctx, "sense-a", "AAAAAAAAAAAAAAAAAAAAAA", requestHash, []audit.Candidate{auditCandidate(t, eventID, "ignored-by-receipt")})
+	if err != nil || replayed[0].Status != "accepted" {
+		t.Fatalf("receipt replay: %+v %v", replayed, err)
+	}
+	different := sha256.Sum256([]byte("request-two"))
+	if _, err := repository.ProcessAuditBatch(ctx, "sense-a", "AAAAAAAAAAAAAAAAAAAAAA", different, []audit.Candidate{auditCandidate(t, eventID, "sense")}); !errors.Is(err, audit.ErrReplayConflict) {
+		t.Fatalf("expected replay conflict, got %v", err)
+	}
+
+	duplicate, err := repository.ProcessAuditBatch(ctx, "sense-a", "BBBBBBBBBBBBBBBBBBBBBB", different, []audit.Candidate{auditCandidate(t, eventID, "sense")})
+	if err != nil || duplicate[0].Status != "duplicate" {
+		t.Fatalf("event duplicate: %+v %v", duplicate, err)
+	}
+	conflictHash := sha256.Sum256([]byte("request-three"))
+	conflict, err := repository.ProcessAuditBatch(ctx, "sense-a", "CCCCCCCCCCCCCCCCCCCCCC", conflictHash, []audit.Candidate{auditCandidate(t, eventID, "other")})
+	if err != nil || conflict[0].Status != "rejected" || conflict[0].ErrorCode == nil || *conflict[0].ErrorCode != "id_conflict" {
+		t.Fatalf("event conflict: %+v %v", conflict, err)
+	}
+	if _, err := db.ExecContext(ctx, `UPDATE bell.audit_events SET actor_id='mutated' WHERE event_id=$1`, eventID); err == nil {
+		t.Fatal("runtime updated immutable audit fact")
+	}
+	if _, err := db.ExecContext(ctx, `DELETE FROM bell.audit_events WHERE event_id=$1`, eventID); err == nil {
+		t.Fatal("runtime deleted immutable audit fact")
+	}
+}