feat: implement T-019 reliable event ingress

Bell/internal/ingress/key.go

@@ -0,0 +1,53 @@
+package ingress
+
+import (
+	"bytes"
+	"encoding/base64"
+	"encoding/json"
+	"errors"
+	"io"
+	"os"
+)
+
+type keyDocument struct {
+	Version int `json:"version"`
+	Keys    []struct {
+		KeyID      string `json:"key_id"`
+		ProducerID string `json:"producer_id"`
+		Secret     string `json:"secret_base64url"`
+	} `json:"keys"`
+}
+
+type Key struct {
+	ProducerID string
+	Secret     []byte
+}
+
+func LoadKeys(path string) (map[string]Key, error) {
+	raw, err := os.ReadFile(path)
+	if err != nil {
+		return nil, errors.New("read Bell event ingress 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 event ingress key file")
+	}
+	var trailing any
+	if err := decoder.Decode(&trailing); !errors.Is(err, io.EOF) {
+		return nil, errors.New("invalid Bell event ingress key file")
+	}
+	values := make(map[string]Key, len(document.Keys))
+	for _, item := range document.Keys {
+		secret, err := base64.RawURLEncoding.DecodeString(item.Secret)
+		if err != nil || !keyIDPattern.MatchString(item.KeyID) || !producerIDPattern.MatchString(item.ProducerID) || len(secret) < 32 {
+			return nil, errors.New("invalid Bell event ingress key")
+		}
+		if _, exists := values[item.KeyID]; exists {
+			return nil, errors.New("duplicate Bell event ingress key ID")
+		}
+		values[item.KeyID] = Key{ProducerID: item.ProducerID, Secret: append([]byte(nil), secret...)}
+	}
+	return values, nil
+}