fix: load uid key from manager config

internal/httpapi/uid.go

@@ -7,10 +7,41 @@ import (
 	"fmt"
 	"strconv"
 	"strings"
+	"sync"
+
+	"golang.org/x/crypto/xtea"
 )
 
 type userID int64
 
+const defaultUIDKey = "la6YsO+bNX/+XIkOqc5Svw=="
+
+var (
+	uidCodecMu sync.RWMutex
+	uidCipher  *xtea.Cipher
+)
+
+func init() {
+	if err := SetUIDKey(defaultUIDKey); err != nil {
+		panic(err)
+	}
+}
+
+func SetUIDKey(encoded string) error {
+	key, err := base64.StdEncoding.DecodeString(strings.TrimSpace(encoded))
+	if err != nil {
+		return fmt.Errorf("invalid uid key: %w", err)
+	}
+	cipher, err := xtea.NewCipher(key)
+	if err != nil {
+		return fmt.Errorf("invalid uid key: %w", err)
+	}
+	uidCodecMu.Lock()
+	uidCipher = cipher
+	uidCodecMu.Unlock()
+	return nil
+}
+
 func (id *userID) UnmarshalJSON(raw []byte) error {
 	value, err := parseUserIDJSON(raw)
 	if err != nil {
@@ -63,7 +94,7 @@ func parseUserID(value string) (int64, error) {
 		if err != nil || len(decoded) < 8 {
 			return 0, fmt.Errorf("invalid user id")
 		}
-		return int64(binary.LittleEndian.Uint64(decoded[:8])), nil
+		return decryptUID(decoded[:8]), nil
 	}
 	return strconv.ParseInt(value, 10, 64)
 }
@@ -72,11 +103,8 @@ func formatUserID(id int64) string {
 	if id == 0 {
 		return ""
 	}
-	src := make([]byte, 8)
-	dst := make([]byte, base64.URLEncoding.WithPadding(base64.NoPadding).EncodedLen(8))
-	binary.LittleEndian.PutUint64(src, uint64(id))
-	base64.URLEncoding.WithPadding(base64.NoPadding).Encode(dst, src)
-	return "usr" + string(dst)
+	encoded := encryptUID(id)
+	return "usr" + base64.URLEncoding.WithPadding(base64.NoPadding).EncodeToString(encoded)
 }
 
 func parseUserIDList(values []userID) []int64 {
@@ -92,3 +120,23 @@ func parseUserIDList(values []userID) []int64 {
 	}
 	return items
 }
+
+func decryptUID(encoded []byte) int64 {
+	dst := make([]byte, 8)
+	uidCodecMu.RLock()
+	cipher := uidCipher
+	uidCodecMu.RUnlock()
+	cipher.Decrypt(dst, encoded[:8])
+	return int64(binary.LittleEndian.Uint64(dst))
+}
+
+func encryptUID(id int64) []byte {
+	src := make([]byte, 8)
+	dst := make([]byte, 8)
+	binary.LittleEndian.PutUint64(src, uint64(id))
+	uidCodecMu.RLock()
+	cipher := uidCipher
+	uidCodecMu.RUnlock()
+	cipher.Encrypt(dst, src)
+	return dst
+}

internal/httpapi/uid_test.go

@@ -22,6 +22,23 @@ func TestUserIDJSONAcceptsIMUserID(t *testing.T) {
 	}
 }
 
+func TestUserIDCodecMatchesIMServer(t *testing.T) {
+	const (
+		publicID = "usrOj2NWDNdlMU"
+		dbID     = int64(1574592702383656960)
+	)
+	got, err := parseUserID(publicID)
+	if err != nil {
+		t.Fatalf("parseUserID: %v", err)
+	}
+	if got != dbID {
+		t.Fatalf("parseUserID(%q)=%d, want %d", publicID, got, dbID)
+	}
+	if formatted := formatUserID(dbID); formatted != publicID {
+		t.Fatalf("formatUserID(%d)=%q, want %q", dbID, formatted, publicID)
+	}
+}
+
 func TestUserIDJSONRejectsNumericID(t *testing.T) {
 	var id userID
 	if err := json.Unmarshal([]byte(`1573862062872858624`), &id); err == nil {