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fix(creds): MQTT regression + secret_kind for hash credentials

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Honest correction to the "every cred-emitting service" claim. Audit
of templates/* found three gaps:

1. MQTT — was working through the legacy adapter, silently dropped
   when Phase 3 (e696c2b) deleted it. Now migrated to encode_secret()
   alongside the others.
2. Postgres — `auth, pw_hash=…` event captures the MD5
   challenge-response the attacker sent. Plaintext irrecoverable, so
   it never fit the (principal, secret_b64=raw_bytes) shape. Lands
   in Credential as secret_kind="postgres_md5_challenge".
3. VNC — `auth_response, response=…hex` event captures the 16-byte
   DES-encrypted challenge. Same situation as Postgres: plaintext
   irrecoverable. Lands as secret_kind="vnc_des_response".

Adds a `secret_kind` discriminator column to Credential (default
"plaintext", indexed). The dedup tuple gains secret_kind so two
credentials with the same sha256 but different kinds are
fundamentally different rows — different challenges produce
different bytes for the same plaintext password, so cross-kind
reuse matches are meaningless and would only confuse analytics.

The model now genuinely covers every cred-emitting service in the
fleet:

  plaintext        SSH, Telnet, FTP, POP3, IMAP, SMTP, Redis, LDAP,
                   MQTT
  postgres_md5_*   Postgres
  vnc_des_response VNC

Username-only services (MySQL/MSSQL — TDS pre-encryption captures
the user but never sees the password byte) intentionally don't feed
Credential — they're recon signals, not cred attempts.

40 tests pass in the touched scope. New cases: secret_kind dedups
independently in the repo; Postgres MD5 + VNC DES emitters thread
through; MQTT round-trips through the native branch.
This commit is contained in:
anti
2026-04-25 06:16:57 -04:00
parent e696c2beb3
commit 6b16c844b6
9 changed files with 165 additions and 8 deletions
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19
decnet/templates/mqtt/server.py
View File

@@ -14,7 +14,12 @@ import random
import struct
import instance_seed as _seed
from syslog_bridge import syslog_line, write_syslog_file, forward_syslog
from syslog_bridge import (
encode_secret,
forward_syslog,
syslog_line,
write_syslog_file,
)
NODE_NAME = os.environ.get("NODE_NAME", "mqtt-broker")
SERVICE_NAME = "mqtt"
@@ -256,7 +261,17 @@ class MQTTProtocol(asyncio.Protocol):
if pkt_type == 1: # CONNECT
info = _parse_connect(payload)
_log("auth", **info)
# Migrate auth event to the universal credential SD shape
# so the ingester's native branch picks up the row. The
# legacy username/password keys are intentionally NOT
# forwarded — encode_secret() supplies secret_printable
# and secret_b64 in their place.
_user = info.get("username", "")
_password = info.get("password", "")
_passthrough = {k: v for k, v in info.items()
if k not in ("username", "password")}
_log("auth", username=_user, principal=_user,
**encode_secret(_password), **_passthrough)
# Decide connection: accept-all > cred list > deny.
cred = (info.get("username", ""), info.get("password", ""))
accepted = (

24
decnet/templates/postgres/server.py
View File

@@ -11,6 +11,7 @@ import os
import struct
import instance_seed as _seed
import base64 as _base64
from syslog_bridge import syslog_line, write_syslog_file, forward_syslog
NODE_NAME = os.environ.get("NODE_NAME", "pgserver")
@@ -137,10 +138,27 @@ class PostgresProtocol(asyncio.Protocol):
self._transport.write(auth_md5)
def _handle_password(self, payload: bytes):
# Postgres MD5 challenge-response: the wire form is the literal
# ASCII string "md5" + 32 hex chars (md5(md5(pw+user)+salt)).
# Plaintext is unrecoverable, so we land this in the Credential
# table as secret_kind="postgres_md5_challenge" — secret_b64
# carries the raw hash bytes (after stripping the "md5" prefix
# and hex-decoding) for content-addressable reuse within-kind.
pw_hash = payload.rstrip(b"\x00").decode(errors="replace")
_log("auth", src=self._peer[0], pw_hash=pw_hash,
username=getattr(self, "_username", ""),
database=getattr(self, "_database", ""))
_hex = pw_hash[3:] if pw_hash.startswith("md5") else pw_hash
try:
_raw = bytes.fromhex(_hex)
except ValueError:
_raw = _hex.encode("utf-8", errors="replace")
_b64 = _base64.b64encode(_raw).decode("ascii")
_user = getattr(self, "_username", "")
_log("auth", src=self._peer[0],
username=_user, principal=_user,
database=getattr(self, "_database", ""),
pw_hash=pw_hash,
secret_kind="postgres_md5_challenge",
secret_printable=pw_hash,
secret_b64=_b64)
user = getattr(self, "_username", "")
msg = f'password authentication failed for user "{user}"'
_seed.jitter_sync(20, 90)

12
decnet/templates/vnc/server.py
View File

@@ -8,6 +8,7 @@ failed". Logs the raw response for offline cracking.
import asyncio
import os
import base64 as _base64
from syslog_bridge import syslog_line, write_syslog_file, forward_syslog
NODE_NAME = os.environ.get("NODE_NAME", "desktop")
@@ -68,7 +69,16 @@ class VNCProtocol(asyncio.Protocol):
return
response = self._buf[:16]
self._buf = self._buf[16:]
_log("auth_response", src=self._peer[0], response=response.hex())
# VNC protocol: 16-byte DES-encrypted challenge. Plaintext
# password is irrecoverable, so we land this credential as
# secret_kind="vnc_des_response" — secret_b64 carries the
# raw 16 bytes for content-addressable within-kind reuse.
_hex = response.hex()
_log("auth_response", src=self._peer[0],
response=_hex,
secret_kind="vnc_des_response",
secret_printable=_hex,
secret_b64=_base64.b64encode(response).decode("ascii"))
# SecurityResult: 1 = failed
self._transport.write(b"\x00\x00\x00\x01")
# Failure reason

17
decnet/web/db/models/logs.py
View File

@@ -72,7 +72,22 @@ class Credential(SQLModel, table=True):
decky_name: str = Field(index=True)
service: str = Field(index=True)
principal: Optional[str] = Field(default=None, index=True, max_length=256)
# Universal lossless secret representations.
# Discriminator for what `secret_b64` actually contains. Default
# ``"plaintext"`` — a recoverable password the attacker sent on the
# wire (SSH/Telnet/FTP/IMAP/POP3/SMTP/Redis/LDAP/MQTT). Other kinds:
# ``"postgres_md5_challenge"`` (md5(md5(pw+user)+salt) hex bytes
# the attacker sent in the Postgres password message — plaintext
# irrecoverable), ``"vnc_des_response"`` (16-byte DES-encrypted
# challenge response — same shape).
#
# Reuse semantics gracefully degrade: same secret_sha256 only
# correlates within a single ``secret_kind``. Cross-kind matches
# are meaningless because different challenges produce different
# bytes for the same plaintext password.
secret_kind: str = Field(default="plaintext", index=True, max_length=32)
# Universal lossless secret representations. For non-plaintext
# kinds, secret_b64 is base64 of the raw attacker-sent bytes (after
# hex-decode for protocols that ship the response as a hex string).
secret_sha256: str = Field(index=True, max_length=64)
secret_b64: Optional[str] = Field(default=None, max_length=2048)
# Best-effort printable form — non-printable bytes collapsed to '?'

3
decnet/web/db/sqlmodel_repo.py
View File

@@ -557,11 +557,13 @@ class SQLModelRepository(BaseRepository):
payload["fields"] = json.dumps(payload["fields"], ensure_ascii=True)
principal = payload.get("principal")
secret_kind = payload.get("secret_kind") or "plaintext"
async with self._session() as session:
stmt = select(Credential).where(
Credential.attacker_ip == payload["attacker_ip"],
Credential.decky_name == payload["decky_name"],
Credential.service == payload["service"],
Credential.secret_kind == secret_kind,
Credential.secret_sha256 == payload["secret_sha256"],
# NULL == NULL is False under SQL — branch the predicate.
(Credential.principal == principal) if principal is not None
@@ -582,6 +584,7 @@ class SQLModelRepository(BaseRepository):
decky_name=payload["decky_name"],
service=payload["service"],
principal=principal,
secret_kind=secret_kind,
secret_sha256=payload["secret_sha256"],
secret_b64=payload.get("secret_b64"),
secret_printable=payload.get("secret_printable"),

2
decnet/web/ingester.py
View File

@@ -246,12 +246,14 @@ async def _ingest_credential_native(
sha256_hex = hashlib.sha256(raw).hexdigest()
principal = fields.get("principal") or fields.get("username")
secret_printable = fields.get("secret_printable")
secret_kind = fields.get("secret_kind") or "plaintext"
await repo.upsert_credential({
"attacker_ip": log_data.get("attacker_ip"),
"decky_name": log_data.get("decky"),
"service": log_data.get("service"),
"principal": _truncate_with_warn(principal, _PRINCIPAL_MAX, "principal"),
"secret_kind": secret_kind,
"secret_sha256": sha256_hex,
"secret_b64": _truncate_with_warn(b64, _SECRET_B64_MAX, "secret_b64"),
"secret_printable": _truncate_with_warn(