sqlmapproject/sqlmap · error · OperationalError

malformed SCRAM server-first message (%s)

Error message

malformed SCRAM server-first message (%s)

What it means

Error "malformed SCRAM server-first message (%s)" thrown in sqlmapproject/sqlmap.

Source

Thrown at extra/dbwire/postgres.py:259

        elif code == 5:  # MD5 password
            salt = payload[4:8]
            inner = hashlib.md5((password or "").encode("utf-8") + (user or "").encode("utf-8")).hexdigest()
            token = b"md5" + hashlib.md5(inner.encode("ascii") + salt).hexdigest().encode("ascii")
            _send(sock, b"p", token + b"\x00")
        elif code == 10:  # SASL (SCRAM-SHA-256)
            if not hasattr(hashlib, "pbkdf2_hmac"):
                raise NotSupportedError("SCRAM-SHA-256 authentication requires Python >= 2.7.8 (hashlib.pbkdf2_hmac)")
            client_nonce = base64.b64encode(os.urandom(18)).decode("ascii")
            cfirst_bare = "n=,r=%s" % client_nonce
            client_first = "n,," + cfirst_bare
            _send(sock, b"p", b"SCRAM-SHA-256\x00" + struct.pack("!I", len(client_first)) + client_first.encode("ascii"))
        elif code == 11:  # SASLContinue (server-first)
            try:
                server_first = payload[4:].decode("ascii")
                attrs = dict(kv.split("=", 1) for kv in server_first.split(","))
                snonce, salt, iterations = attrs["r"], base64.b64decode(attrs["s"]), int(attrs["i"])
            except (KeyError, ValueError, binascii.Error, UnicodeDecodeError) as ex:
                raise OperationalError("malformed SCRAM server-first message (%s)" % ex)
            # RFC 5802 5.1: the server nonce MUST start with the client nonce and MUST add material of its
            # own. Skipping this lets anything that can answer the TCP connection replay a recorded
            # server-first and drive the exchange - and dbwire has no TLS layer underneath to catch it.
            if not client_nonce or not snonce.startswith(client_nonce) or len(snonce) <= len(client_nonce):
                raise OperationalError("SCRAM server nonce does not extend the client nonce (rogue server?)")
            if iterations < 4096:   # RFC 5802 recommends >= 4096; a tiny count cheapens an offline attack
                raise OperationalError("SCRAM iteration count %d is too low" % iterations)
            salted = hashlib.pbkdf2_hmac("sha256", (password or "").encode("utf-8"), salt, iterations)
            client_key = hmac.new(salted, b"Client Key", hashlib.sha256).digest()
            stored_key = hashlib.sha256(client_key).digest()
            client_final_noproof = "c=biws,r=%s" % snonce
            auth_message = "%s,%s,%s" % (cfirst_bare, server_first, client_final_noproof)
            client_sig = hmac.new(stored_key, auth_message.encode("ascii"), hashlib.sha256).digest()
            proof = base64.b64encode(_xor(client_key, client_sig)).decode("ascii")
            _send(sock, b"p", ("%s,p=%s" % (client_final_noproof, proof)).encode("ascii"))
        elif code == 12:  # SASLFinal (server-final): verify the server too, or the handshake is one-way
            # Without this the client proves itself to the server and simply trusts whatever answers back.
            # ServerSignature = HMAC(ServerKey, AuthMessage) can only be produced by a peer that holds the

View on GitHub (pinned to 0a35b20e39)

When it happens

Trigger: Thrown at extra/dbwire/postgres.py:259 when the library encounters an invalid state.

Common situations: See trigger scenarios.

Understand the failure class

• Parsing and encoding errors: unexpected token, malformed input — why parsers reject input and how to find the real culprit.

AI-assisted analysis of sqlmapproject/sqlmap@0a35b20e39 (2026-08-26). Data as JSON: /api/errors/636ce0347a9ad6ae. Report an issue: GitHub.