sqlmapproject/sqlmap · error · InterfaceError

invalid backend message length (%d)

Error message

invalid backend message length (%d)

What it means

Error "invalid backend message length (%d)" thrown in sqlmapproject/sqlmap.

Source

Thrown at extra/dbwire/postgres.py:79

# SQLSTATE class (first 2 chars) -> DB-API exception, so callers can distinguish (mirrors psycopg2)
_SQLSTATE_CLASS = {
    "22": DataError, "23": IntegrityError,
    "08": OperationalError, "28": OperationalError, "53": OperationalError,
    "57": OperationalError, "58": OperationalError,
}

def _xor(a, b):
    # byte-wise XOR of two equal-length byte strings (Python 2 and 3 safe)
    if str is bytes:  # Python 2: iterating bytes yields 1-char strings
        return b"".join(chr(ord(x) ^ ord(y)) for x, y in zip(a, b))
    return bytes(x ^ y for x, y in zip(a, b))

def _read_message(sock):
    mtype = recvn(sock, 1)
    (length,) = struct.unpack("!I", recvn(sock, 4))
    if length < 4 or length > _MAX_MESSAGE_LENGTH:
        raise InterfaceError("invalid backend message length (%d)" % length)
    return mtype, recvn(sock, length - 4)

def _send(sock, mtype, payload):
    try:
        sock.sendall((mtype or b"") + struct.pack("!I", len(payload) + 4) + payload)
    except (socket.error, OSError) as ex:
        raise connection_lost(ex)

def _error_message(payload):
    # ErrorResponse/NoticeResponse: series of (byte field-code, cstring value), terminated by a NUL byte.
    # Returns (human message, SQLSTATE). Tolerant of a truncated/unterminated stream (find() not index()).
    fields, off = {}, 0
    while off < len(payload) and payload[off:off + 1] != b"\x00":
        code = payload[off:off + 1]
        end = payload.find(b"\x00", off + 1)
        if end == -1:
            break
        fields[code] = payload[off + 1:end].decode("utf-8", "replace")

View on GitHub (pinned to 0a35b20e39)

When it happens

Trigger: Thrown at extra/dbwire/postgres.py:79 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of sqlmapproject/sqlmap@0a35b20e39 (2026-08-26). Data as JSON: /api/errors/a8231b7f6b4ebba6. Report an issue: GitHub.