When RDP_ENABLE_NLA=true (service_cfg.nla=true on the topology side),
confirm PROTOCOL_HYBRID on the X.224 Connection Confirm, upgrade the
socket to TLS using a self-signed cert generated at first start by
the entrypoint, then drive a tiny CredSSP loop:
- Read inbound TSRequest DER (bounded to MAX_TSREQUEST_LEN).
- Scan for the NTLMSSP signature, dispatch on message type:
Type 1 -> respond with a hand-built TSRequest carrying our Type 2
challenge. Type 3 -> parse_type3() and emit auth_attempt with the
universal credential SD shape (secret_kind = ntlmssp_v2).
- Hand-built DER: no pyasn1 dependency.
Also folds in a small fix-up to commit 1: SMB SERVER_CHALLENGE was
hardcoded to 0x11..0x88 across the fleet, which would let a scanner
fingerprint every DECNET decky by its NTLM challenge. Both SMB and
RDP now derive the 8-byte challenge from
instance_seed.random_bytes(8, "ntlm_challenge"), giving each decky a
deterministic-but-distinct value. SMB Dockerfile gets the
instance_seed.py copy too (was synced into the build context but not
COPYed into the image).
- decnet/services/rdp.py: optional service_cfg.nla bool flips
RDP_ENABLE_NLA in the compose env.
- decnet/templates/rdp/Dockerfile + entrypoint.sh: openssl install +
per-decky cert generation gated on RDP_ENABLE_NLA.
- 9 NLA unit tests cover the DER reader/builder, _handle_nla round-
trip with Type 1 / Type 3, oversized-DER rejection, and per-
NODE_NAME challenge divergence.
- DEBT.md: DEBT-040 closed; full TS_INFO_PACKET capture documented as
a follow-up if attacker telemetry justifies it.
Replace Twisted-based connection logger with an asyncio handler that
parses the X.224 Connection Request, extracts the mstshash routing
cookie (universal across mstsc / FreeRDP / Hydra / ncrack / MSF
rdp_login), records the rdpNegRequest.requestedProtocols flags, and
answers with a well-formed X.224 Connection Confirm selecting
PROTOCOL_RDP.
Scope-down vs. the original DEBT-040 plan: full TS_INFO_PACKET
extraction would require either Standard-RDP-Security RC4 stream-
cipher implementation (with our own RSA pair + MS-RDPBCGR signing) or
a complete MCS+GCC ASN.1/BER stack for the SSL path — both far
exceed the 150 LoC budget the DEBT cited. The mstshash cookie is the
only piece of credential information that flows in plaintext on the
wire when the attacker speaks RDP, so capturing it is the highest-
value-per-byte signal available without going down either rabbit
hole. Phase 3 (CredSSP/NLA, next commit) is where actual NTLMv2
hashes land.
- Drops Twisted dependency from rdp/Dockerfile; adds ntlmssp.py copy
ahead of the NLA path that consumes it.
- 7 unit tests cover cookie capture, requestedProtocols recording,
CC framing, no-cookie path, and oversized/non-TPKT drops.
