Ships the load-bearing primitive both Phase 5 (SMB) and Phase 7
(RDP NLA) need: a standalone NTLMSSP Type 3 (AUTHENTICATE_MESSAGE)
parser per MS-NLMP §2.2.1.3.
Surface:
parse_type3(blob) -> dict | None
find_ntlmssp(buf) -> int # locate NTLMSSP\\0 inside SPNEGO outer
Returns the universal Credential SD shape:
username + domain (decoded UTF-16-LE or ASCII per NEGOTIATE_UNICODE)
principal = "DOMAIN\\\\username"
secret_kind = "ntlmssp_v1" (24-byte fixed) or "ntlmssp_v2" (variable)
secret_b64 = base64 of NtChallengeResponse — canonical hashcat input
(-m 5500 v1, -m 5600 v2)
Bounds-checked for untrusted-input safety. Anonymous binds (empty NT
response) return None — no credential to record.
7 unit tests cover NTLMv1/v2 distinction, ASCII vs Unicode strings,
empty-domain shape, malformed signature/type rejection, and SPNEGO-
wrapped find_ntlmssp() lookup.
DEBT-040 opens to track the three remaining protocol framers that
will consume this parser:
- SMB: hand-rolled SMB2 + Session Setup framer (~200 LoC) replacing
Impacket's opaque SimpleSMBServer
- RDP basic auth: TPKT/X.224/MCS framer for legacy plaintext path
(~150 LoC)
- RDP NLA: TLS upgrade + CredSSP TSRequest parser, reuses parse_type3
via the SPNEGO inner blob (~250 LoC)
These are substantial protocol implementations each — landing them
inline with Phase 1-3+6's cred coverage rollout would have inflated
the session beyond reasonable scope. Cred-reuse analytics already work
across the 12 services covered in this session; the deferred three
just round out the fleet.
Replaces the opaque Bounty.bounty_type='credential' path with a
dedicated `credentials` table whose schema is forward-compatible
across every auth-bearing service in the fleet. Hoisted indexed
columns (secret_sha256, principal, service, attacker_ip) carry the
universal reuse-analytics signal; service-specific JSON keys ride
in `fields`. Cross-service reuse queries become an indexed lookup
on secret_sha256 instead of JSON_EXTRACT scans.
Schema decisions baked in (per ANTI):
- New `Credential` table, not extension to Bounty
- Hoisted `principal` column for cross-service principal-reuse
- Standardized JSON keys: every payload carries secret_b64 +
secret_printable + principal universally; service-specific extras
(user, domain, dn, mech, …) ride alongside
The auth-helper SD-block emits the new shape natively. The ingester
forks at _extract_bounty:
- Native shape (SSH/Telnet, future emitters): secret_b64 present →
direct upsert_credential
- Legacy shape (FTP/POP3/IMAP/SMTP today): username + password →
adapter synthesizes secret_{b64,sha256,printable} on the fly,
upserts into the same Credential table. Tracked as DEBT-039;
one-shot bridge until those service templates migrate.
Defense-in-depth across five layers (input validation):
- C helper: bytes outside [0x20, 0x7f) collapse to '?', RFC 5424
escape rules for \\, ", ]; b64 preserves exact bytes
- Ingester native branch: rejects malformed secret_b64 (regex), drops
the credential row but keeps the underlying Log
- Ingester legacy adapter: same printable-ASCII filter as the C
code; sha256 + b64 over the original utf-8 bytes (lossless, even
when secret_printable is sanitized)
- DB column caps with truncation warning; sha256 always over the
full pre-truncation bytes so reuse queries match across truncation
- JSON serialized with ensure_ascii=True so utf8mb4 columns stay
safe even with non-ASCII service-specific keys
Bounty.bounty_type='credential' is no longer written. Pre-v1: no
historical backfill; existing rows stay untouched but unused.
595 tests pass; new tests cover the model + repo (upsert dedup,
null-principal independence, cross-service reuse, filters), both
ingester branches, b64 validation, sanitization preserving the
fingerprinting signal in b64.
Promotes auth-helper.c to decnet/templates/_shared/auth-helper/ and
adds _sync_auth_helper_sources() — mirrors the existing sessrec sync
pattern that keeps shared sources in step with per-template build
contexts.
Telnet's image grows the same multi-stage musl build, COPY of the
static helper into /usr/sbin/auth-helper, and prepended pam_exec line
in /etc/pam.d/login. Pulls in the `login` package (real Debian
PAM-aware /bin/login, replacing busybox's PAM-less applet) and
libpam-modules transitively for pam_exec.so.
Verified inside the rebuilt telnet image:
- /bin/login is the real 53KB Debian binary (PAM-aware)
- /etc/pam.d/login top line is the auth-helper hook
- pam_exec.so present at /usr/lib/x86_64-linux-gnu/security/pam_exec.so
- helper smoke-run emits correct RFC 5424 line for `telnetpw` →
password_b64="dGVsbmV0cHc="
SSH Dockerfile updated to read auth-helper.c from auth-helper/
subdirectory so both templates use the synced layout. The canonical
source lives in _shared/; per-template copies are tracked in git AND
synced at deploy time so a drift on either side rebases on the next
deploy.
Closes the telnet half of DEBT-038's #5 follow-up.
Build login-session into both images as the swapped root shell, add a
quarantine bind mount for telnet (symmetric to SSH), seed transcripts/
dir and service discriminant at entrypoint. Deployer syncs sessrec.c +
Makefile into each build context alongside the existing syslog_bridge
helper. sessrec falls back to /etc/sessrec.service when env is stripped
(busybox /bin/login).
New decnet/templates/_shared/sessrec/ — a small C program installed as the
login shell in SSH / Telnet deckies. Forkpty-relays /bin/bash, records each
chunk as an asciinema v2 event into a shared JSONL day-shard keyed by sid,
and emits one RFC 5424 session_recorded line on exit (direct to PID 1's
stdout, same pattern syslog_bridge.py uses).
Storage: one shard per (decky, UTC day) at
/var/lib/systemd/coredump/transcripts/sessions-YYYY-MM-DD.jsonl. Concurrent
appends are lock-free: each write is chunked below PIPE_BUF so O_APPEND
interleaves atomically. Per-session cap 10 MB with a trunc sentinel; disk-
free precheck (<200 MB) falls through to plain bash with a session_skipped
log event. Attacker src_ip resolves from \$SSH_CONNECTION, getpeername(0),
or utmp in that order. SIGWINCH appends a 'r' resize event so ncurses
replays stay aligned.
Stealth for v1: /etc/passwd shell-swap to /usr/libexec/login-session
(plausible login-machinery path) + prctl comm disguise. Full LD_PRELOAD
argv-zap is deferred — sshd strips LD_PRELOAD from the session env, so
wiring the existing argv_zap.so into this path needs a separate wrapper.
DEBT-033 opened for size-based day-shard rotation; v1's disk-free precheck
covers the worst case but can be blinded by a one-shot disk fill.
