fix: bound DWH credential digest validation

tools/dwh-auth/internal/record/record.go

@@ -111,6 +111,9 @@ func validInstallationID(value string) bool {
 }
 
 func validDigest(value string) bool {
+	if len(value) != 43 {
+		return false
+	}
 	decoded, err := base64.RawURLEncoding.DecodeString(value)
 	return err == nil && len(decoded) == 32 && base64.RawURLEncoding.EncodeToString(decoded) == value
 }