merge: testing → main (reconcile 2-week divergence)
This commit is contained in:
296
decnet/templates/smb/server.py
Normal file
296
decnet/templates/smb/server.py
Normal file
@@ -0,0 +1,296 @@
|
||||
#!/usr/bin/env python3
|
||||
"""Minimal honeypot SMB2 server.
|
||||
|
||||
Hand-rolled asyncio framer that does just enough of MS-SMB2 to lure a
|
||||
client through Negotiate → Session Setup (Type1) → Session Setup
|
||||
(Type3), at which point we extract the inner NTLMSSP Type 3 with the
|
||||
shared :func:`ntlmssp.parse_type3` parser and emit a credential SD
|
||||
block. Authentication always fails with STATUS_LOGON_FAILURE — the
|
||||
attacker's hash lands in the Credential table; the attacker does not
|
||||
land on the host.
|
||||
|
||||
References:
|
||||
- MS-SMB2 §2.2.3 NEGOTIATE Request, §2.2.4 NEGOTIATE Response
|
||||
- MS-SMB2 §2.2.5 SESSION_SETUP Request, §2.2.6 SESSION_SETUP Response
|
||||
- MS-NLMP §2.2.1 NTLMSSP messages (CHALLENGE_MESSAGE Type 2)
|
||||
- RFC 1002 §4.3 NetBIOS Session Service framing
|
||||
"""
|
||||
|
||||
from __future__ import annotations
|
||||
|
||||
import asyncio
|
||||
import os
|
||||
import struct
|
||||
|
||||
import instance_seed
|
||||
from ntlmssp import find_ntlmssp, parse_type3
|
||||
from syslog_bridge import syslog_line, write_syslog_file, forward_syslog
|
||||
|
||||
NODE_NAME = os.environ.get("NODE_NAME", "WORKSTATION")
|
||||
SERVICE_NAME = "smb"
|
||||
LOG_TARGET = os.environ.get("LOG_TARGET", "")
|
||||
|
||||
LISTEN_HOST = "0.0.0.0" # nosec B104 — honeypot binds all interfaces by design
|
||||
LISTEN_PORT = 445
|
||||
|
||||
# SMB2 status codes
|
||||
STATUS_SUCCESS = 0x00000000
|
||||
STATUS_MORE_PROCESSING_REQUIRED = 0xC0000016
|
||||
STATUS_LOGON_FAILURE = 0xC000006D
|
||||
|
||||
# SMB2 commands
|
||||
SMB2_NEGOTIATE = 0x0000
|
||||
SMB2_SESSION_SETUP = 0x0001
|
||||
|
||||
SMB2_MAGIC = b"\xfeSMB"
|
||||
NBSS_SESSION_MESSAGE = 0x00
|
||||
|
||||
# Per-instance NTLM challenge: deterministic-per-decky-but-different-
|
||||
# across-the-fleet. Derived from NODE_NAME so two captures from the
|
||||
# same decky reuse the same challenge (lets offline attackers retry
|
||||
# wordlists), while every decky in the fleet differs (looks like a
|
||||
# real population of hosts to a scanner).
|
||||
SERVER_CHALLENGE = instance_seed.random_bytes(8, "ntlm_challenge")
|
||||
SERVER_GUID = instance_seed.random_bytes(16, "smb_server_guid")
|
||||
|
||||
# Read caps; an attacker shouldn't be able to make us allocate
|
||||
# unbounded memory just by lying about NetBIOS frame length.
|
||||
MAX_NBSS_LEN = 1 * 1024 * 1024 # 1 MiB is plenty for SessionSetup blobs
|
||||
|
||||
|
||||
def _log(event_type: str, severity: int = 6, **kwargs) -> None:
|
||||
line = syslog_line(SERVICE_NAME, NODE_NAME, event_type, severity, **kwargs)
|
||||
write_syslog_file(line)
|
||||
forward_syslog(line, LOG_TARGET)
|
||||
|
||||
|
||||
# ── SPNEGO / NTLMSSP Type 2 builder ──────────────────────────────────────────
|
||||
|
||||
|
||||
def _build_ntlmssp_type2(challenge: bytes) -> bytes:
|
||||
"""Build a minimal NTLMSSP CHALLENGE_MESSAGE (MS-NLMP §2.2.1.2).
|
||||
|
||||
Layout (all little-endian):
|
||||
0 "NTLMSSP\\0" 8 bytes
|
||||
8 MessageType=2 u32
|
||||
12 TargetNameFields 8 bytes (Len, MaxLen, Offset)
|
||||
20 NegotiateFlags u32
|
||||
24 ServerChallenge 8 bytes
|
||||
32 Reserved 8 bytes
|
||||
40 TargetInfoFields 8 bytes
|
||||
48 Version 8 bytes
|
||||
56 Payload TargetName + TargetInfo
|
||||
|
||||
We advertise NEGOTIATE_UNICODE | NEGOTIATE_NTLM | NEGOTIATE_TARGET_INFO
|
||||
(0x00828201) which is what real Windows servers send in practice; the
|
||||
attacker's client uses these flags to decide whether to send Unicode
|
||||
field strings in its Type 3 — the parser handles either.
|
||||
"""
|
||||
target = "WORKGROUP".encode("utf-16-le")
|
||||
# AV pair list: NetBIOS computer name + EOL terminator
|
||||
av_name = "WORKGROUP".encode("utf-16-le")
|
||||
target_info = struct.pack("<HH", 1, len(av_name)) + av_name + struct.pack("<HH", 0, 0)
|
||||
|
||||
flags = 0x00828201 # UNICODE | NTLM | TARGET_INFO | always_sign
|
||||
payload = target + target_info
|
||||
target_off = 56
|
||||
info_off = target_off + len(target)
|
||||
|
||||
return (
|
||||
b"NTLMSSP\x00"
|
||||
+ struct.pack("<I", 2) # Type 2
|
||||
+ struct.pack("<HHI", len(target), len(target), target_off)
|
||||
+ struct.pack("<I", flags)
|
||||
+ challenge
|
||||
+ b"\x00" * 8 # reserved
|
||||
+ struct.pack("<HHI", len(target_info), len(target_info), info_off)
|
||||
+ b"\x00" * 8 # version
|
||||
+ payload
|
||||
)
|
||||
|
||||
|
||||
def _wrap_spnego_type2(ntlm_type2: bytes) -> bytes:
|
||||
"""SPNEGO NegTokenResp DER carrying the NTLMSSP Type 2 blob.
|
||||
|
||||
Real Windows wraps Type 2 in an SPNEGO NegTokenResp (RFC 4178). A
|
||||
well-formed wrapping is rarely required by attacker tools (Hydra,
|
||||
Metasploit's smb_login, Impacket scanners all accept a raw Type 2
|
||||
too) — but we ship the SPNEGO envelope so that finicky clients
|
||||
don't bail out before sending Type 3, which is what we actually
|
||||
want on the wire. The DER below hand-encodes a single
|
||||
``NegTokenResp`` with negState=accept-incomplete, supportedMech =
|
||||
NTLMSSP OID, and responseToken = ntlm_type2.
|
||||
"""
|
||||
# NTLMSSP OID = 1.3.6.1.4.1.311.2.2.10 → DER bytes
|
||||
ntlmssp_oid = bytes.fromhex("06 0a 2b 06 01 04 01 82 37 02 02 0a".replace(" ", ""))
|
||||
# negState [0] enum 1 (accept-incomplete)
|
||||
neg_state = bytes.fromhex("a0 03 0a 01 01".replace(" ", ""))
|
||||
# supportedMech [1] OID
|
||||
supported = b"\xa1" + _der_len(len(ntlmssp_oid)) + ntlmssp_oid
|
||||
# responseToken [2] OCTET STRING
|
||||
rt_inner = b"\x04" + _der_len(len(ntlm_type2)) + ntlm_type2
|
||||
response_token = b"\xa2" + _der_len(len(rt_inner)) + rt_inner
|
||||
inner = neg_state + supported + response_token
|
||||
neg_token_resp = b"\x30" + _der_len(len(inner)) + inner # SEQUENCE
|
||||
# NegTokenResp is itself tagged [1] in the outer choice
|
||||
return b"\xa1" + _der_len(len(neg_token_resp)) + neg_token_resp
|
||||
|
||||
|
||||
def _der_len(n: int) -> bytes:
|
||||
if n < 0x80:
|
||||
return bytes([n])
|
||||
body = n.to_bytes((n.bit_length() + 7) // 8, "big")
|
||||
return bytes([0x80 | len(body)]) + body
|
||||
|
||||
|
||||
# ── SMB2 PDU helpers ─────────────────────────────────────────────────────────
|
||||
|
||||
|
||||
def _smb2_header(command: int, status: int, message_id: int, session_id: int = 0) -> bytes:
|
||||
"""SMB2 sync header (64 bytes), MS-SMB2 §2.2.1."""
|
||||
return (
|
||||
SMB2_MAGIC # ProtocolId
|
||||
+ struct.pack("<H", 64) # StructureSize
|
||||
+ struct.pack("<H", 0) # CreditCharge
|
||||
+ struct.pack("<I", status) # Status
|
||||
+ struct.pack("<H", command) # Command
|
||||
+ struct.pack("<H", 1) # CreditResponse
|
||||
+ struct.pack("<I", 0x00000001) # Flags = SERVER_TO_REDIR
|
||||
+ struct.pack("<I", 0) # NextCommand
|
||||
+ struct.pack("<Q", message_id) # MessageId
|
||||
+ struct.pack("<I", 0) # Reserved (sync)
|
||||
+ struct.pack("<I", 0) # TreeId
|
||||
+ struct.pack("<Q", session_id) # SessionId
|
||||
+ b"\x00" * 16 # Signature
|
||||
)
|
||||
|
||||
|
||||
def _negotiate_response(message_id: int) -> bytes:
|
||||
"""SMB2 NEGOTIATE response (MS-SMB2 §2.2.4) — dialect 0x0210 (SMB 2.1)."""
|
||||
body = (
|
||||
struct.pack("<H", 65) # StructureSize
|
||||
+ struct.pack("<H", 0) # SecurityMode
|
||||
+ struct.pack("<H", 0x0210) # DialectRevision = SMB 2.1
|
||||
+ struct.pack("<H", 0) # Reserved
|
||||
+ SERVER_GUID
|
||||
+ struct.pack("<I", 0) # Capabilities
|
||||
+ struct.pack("<I", 0x00010000) # MaxTransactSize
|
||||
+ struct.pack("<I", 0x00010000) # MaxReadSize
|
||||
+ struct.pack("<I", 0x00010000) # MaxWriteSize
|
||||
+ struct.pack("<Q", 0) # SystemTime
|
||||
+ struct.pack("<Q", 0) # ServerStartTime
|
||||
+ struct.pack("<H", 128) # SecurityBufferOffset (header64+body64)
|
||||
+ struct.pack("<H", 0) # SecurityBufferLength
|
||||
+ struct.pack("<I", 0) # Reserved2
|
||||
)
|
||||
return _smb2_header(SMB2_NEGOTIATE, STATUS_SUCCESS, message_id) + body
|
||||
|
||||
|
||||
def _session_setup_response(message_id: int, session_id: int, sec_blob: bytes, status: int) -> bytes:
|
||||
"""SMB2 SESSION_SETUP response (MS-SMB2 §2.2.6) carrying SPNEGO blob."""
|
||||
body = (
|
||||
struct.pack("<H", 9) # StructureSize
|
||||
+ struct.pack("<H", 0) # SessionFlags
|
||||
+ struct.pack("<H", 64 + 8) # SecurityBufferOffset
|
||||
+ struct.pack("<H", len(sec_blob)) # SecurityBufferLength
|
||||
)
|
||||
return _smb2_header(SMB2_SESSION_SETUP, status, message_id, session_id) + body + sec_blob
|
||||
|
||||
|
||||
# ── Connection handler ───────────────────────────────────────────────────────
|
||||
|
||||
|
||||
async def _handle_client(reader: asyncio.StreamReader, writer: asyncio.StreamWriter) -> None:
|
||||
peer = writer.get_extra_info("peername") or ("?", 0)
|
||||
src_ip, src_port = peer[0], peer[1]
|
||||
_log("connection", src_ip=src_ip, src_port=src_port)
|
||||
session_id = 0x1000_0000_0000_0001
|
||||
setup_round = 0
|
||||
try:
|
||||
while True:
|
||||
# NetBIOS Session Service framing: 1 type byte + 3 length bytes
|
||||
hdr = await reader.readexactly(4)
|
||||
if hdr[0] != NBSS_SESSION_MESSAGE:
|
||||
# Session Request / Keepalive / etc — quietly drop.
|
||||
break
|
||||
nb_len = int.from_bytes(hdr[1:4], "big")
|
||||
if nb_len < 64 or nb_len > MAX_NBSS_LEN:
|
||||
break
|
||||
pdu = await reader.readexactly(nb_len)
|
||||
if not pdu.startswith(SMB2_MAGIC):
|
||||
# SMB1 Negotiate or other — not implemented; drop.
|
||||
break
|
||||
command = struct.unpack_from("<H", pdu, 12)[0]
|
||||
message_id = struct.unpack_from("<Q", pdu, 24)[0]
|
||||
if command == SMB2_NEGOTIATE:
|
||||
resp = _negotiate_response(message_id)
|
||||
_send_nbss(writer, resp)
|
||||
elif command == SMB2_SESSION_SETUP:
|
||||
setup_round += 1
|
||||
# Body starts after 64-byte header; parse SecurityBufferOffset/Length
|
||||
if len(pdu) < 64 + 24:
|
||||
break
|
||||
sec_off = struct.unpack_from("<H", pdu, 64 + 12)[0]
|
||||
sec_len = struct.unpack_from("<H", pdu, 64 + 14)[0]
|
||||
blob = pdu[sec_off:sec_off + sec_len] if sec_len else b""
|
||||
if setup_round == 1:
|
||||
# First Session Setup → respond with NTLMSSP Type 2
|
||||
type2 = _build_ntlmssp_type2(SERVER_CHALLENGE)
|
||||
spnego = _wrap_spnego_type2(type2)
|
||||
resp = _session_setup_response(
|
||||
message_id, session_id, spnego, STATUS_MORE_PROCESSING_REQUIRED
|
||||
)
|
||||
_send_nbss(writer, resp)
|
||||
else:
|
||||
# Second Session Setup → contains NTLMSSP Type 3
|
||||
off = find_ntlmssp(blob)
|
||||
if off >= 0:
|
||||
cred = parse_type3(blob[off:])
|
||||
if cred:
|
||||
_log(
|
||||
"auth_attempt",
|
||||
src_ip=src_ip,
|
||||
src_port=src_port,
|
||||
**cred,
|
||||
)
|
||||
# Always fail authentication
|
||||
resp = _session_setup_response(
|
||||
message_id, session_id, b"", STATUS_LOGON_FAILURE
|
||||
)
|
||||
_send_nbss(writer, resp)
|
||||
break
|
||||
else:
|
||||
# We only implement Negotiate + SessionSetup; other commands
|
||||
# could keep an attacker engaged longer but require state we
|
||||
# don't carry. Disconnect.
|
||||
break
|
||||
except (asyncio.IncompleteReadError, ConnectionError):
|
||||
pass
|
||||
except Exception as exc: # noqa: BLE001 — honeypot must never crash the worker
|
||||
_log("error", severity=4, src_ip=src_ip, msg=str(exc))
|
||||
finally:
|
||||
try:
|
||||
writer.close()
|
||||
await writer.wait_closed()
|
||||
except Exception:
|
||||
pass
|
||||
_log("disconnect", src_ip=src_ip, src_port=src_port)
|
||||
|
||||
|
||||
def _send_nbss(writer: asyncio.StreamWriter, smb_pdu: bytes) -> None:
|
||||
nbss = bytes([NBSS_SESSION_MESSAGE]) + len(smb_pdu).to_bytes(3, "big")
|
||||
writer.write(nbss + smb_pdu)
|
||||
|
||||
|
||||
async def _main() -> None:
|
||||
_log("startup", msg=f"SMB server starting as {NODE_NAME}")
|
||||
server = await asyncio.start_server(_handle_client, LISTEN_HOST, LISTEN_PORT)
|
||||
async with server:
|
||||
await server.serve_forever()
|
||||
|
||||
|
||||
if __name__ == "__main__":
|
||||
try:
|
||||
asyncio.run(_main())
|
||||
except KeyboardInterrupt:
|
||||
_log("shutdown")
|
||||
Reference in New Issue
Block a user