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Add baseline reconciliation: accept audited drift with a reason

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Implements the v0.9 roadmap item from the approved design spec. Operators
accept a specific FIM/package/listener/SUID drift item with a mandatory
reason; the ack suppresses that one alert only while the live state still
matches the recorded fingerprint. Content kinds (fim/pkgfile) re-alert on
further change; identity kinds (listener/suid) retire on TTL or revoke.

- reconcile.py: ReconcileStore (mtime-cached, fails closed on missing/corrupt
  store), fingerprint builders, and the filter_alerts chokepoint.
- CLI: baseline accept/revoke/list with --reason/--expires/--force/--stale/--json.
- Wired at the daemon sweep + eBPF chokepoint, fim-check, and /api/integrity.
- RECONCILE_V1 schema, config knob, COMMAND_REFERENCE/SCHEMAS/OPERATIONS/ROADMAP
  docs, and reconcile unit/CLI/integration tests.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
This commit is contained in:
Luna 2026-06-27 10:33:55 -07:00
parent 3d2047fde2
commit dbbe35b3fc
18 changed files with 1155 additions and 28 deletions
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# SPDX-License-Identifier: GPL-3.0-or-later
"""Baseline reconciliation — accept legitimate drift with an audited reason.
The daemon re-alerts on every sweep for drift it cannot distinguish from an
attack: a config file the operator edited, a service that started after boot, a
package-installed SUID binary. Rebuilding baselines silently folds the change in
with no record of *why*; permanent config allowlists carry no per-item reason
and never expire.
This module is the missing middle ground. An operator *accepts* a specific,
identified drift item with a mandatory reason; the acknowledgement suppresses
that one alert **only while the live state still matches the accepted
fingerprint**. The moment the item changes again (or its TTL expires) the ack
goes stale and the alert returns. Every acceptance records who, when, why, and
the exact fingerprint, in a single queryable store.
No other module is aware of ack semantics: detectors keep emitting alerts and
``ReconcileStore.filter_alerts`` drops the acknowledged ones at a chokepoint.
Scope: ``fim``/``pkgfile`` acks are content-bound (they go stale automatically
when the file changes); ``listener``/``suid`` acks are identity-bound (a
different port/comm or path is a new, unrelated alert, so only TTL expiry or an
explicit revoke staleness them). eBPF-only signatures with no baseline concept
are out of scope.
"""
from __future__ import annotations
import json
import os
import re
from dataclasses import dataclass
from datetime import datetime, timedelta, timezone
from pathlib import Path
from . import schemas
from .alert import Alert
from .config import Config
KINDS = ("fim", "pkgfile", "listener", "suid")
# Map an alert dedup key back to the (kind, target) an ack is filed under. The
# prefixes are the stable keys minted by the FIM detector and the
# new_listener/new_suid detectors.
_KEY_PREFIXES = (
("fim:pkg:", "pkgfile"),
("fim:mod:", "fim"),
("fim:add:", "fim"),
("fim:del:", "fim"),
("lis:", "listener"),
("suid:", "suid"),
)
def alert_identity(key: str) -> tuple[str | None, str | None]:
"""Resolve an alert key to ``(kind, target)``, or ``(None, None)`` if the
signature has no baseline concept and can never be acknowledged."""
for prefix, kind in _KEY_PREFIXES:
if key.startswith(prefix):
return kind, key[len(prefix):]
return None, None
_DURATION_RE = re.compile(r"^(\d+)([dhm])$")
def parse_duration(text: str) -> timedelta:
"""Parse ``7d`` / ``12h`` / ``30m`` into a timedelta. Raises ValueError."""
m = _DURATION_RE.match(text.strip())
if not m:
raise ValueError(
f"invalid duration {text!r}; use forms like 7d, 12h, 30m")
n = int(m.group(1))
unit = m.group(2)
return {"d": timedelta(days=n),
"h": timedelta(hours=n),
"m": timedelta(minutes=n)}[unit]
def build_fingerprint(kind: str, target: str, live) -> dict:
"""Build the kind-specific fingerprint compared on each sweep.
``live`` is the live observation for the target: a FIM scan entry dict for
``fim`` (``None`` when the path is absent), a list of pacman reason strings
for ``pkgfile``, and ignored for the identity kinds.
"""
if kind == "fim":
entry = live or {}
return {k: entry.get(k) for k in ("sha256", "mode", "uid", "gid")}
if kind == "pkgfile":
return {"reasons": sorted(live or [])}
if kind == "listener":
return {"key": target}
if kind == "suid":
return {"path": target}
raise ValueError(f"unknown reconciliation kind: {kind}")
def current_actor() -> str:
"""Best-effort operator identity for the audit record."""
try:
return os.getlogin()
except OSError:
return (os.environ.get("SUDO_USER") or os.environ.get("USER")
or os.environ.get("LOGNAME") or "unknown")
def _utcnow() -> datetime:
return datetime.now(timezone.utc)
def _iso(dt: datetime) -> str:
return dt.astimezone(timezone.utc).isoformat()
@dataclass
class Record:
kind: str
target: str
fingerprint: dict
reason: str
actor: str
accepted_at: str
expires_at: str | None = None
status: str = "ok"
@property
def identity(self) -> tuple[str, str]:
return (self.kind, self.target)
def expiry(self) -> datetime | None:
if not self.expires_at:
return None
try:
return datetime.fromisoformat(self.expires_at)
except ValueError:
return None
def to_dict(self) -> dict:
d = {
"kind": self.kind,
"target": self.target,
"fingerprint": self.fingerprint,
"reason": self.reason,
"actor": self.actor,
"accepted_at": self.accepted_at,
"status": self.status,
}
if self.expires_at:
d["expires_at"] = self.expires_at
return d
@classmethod
def from_dict(cls, d: dict) -> "Record":
return cls(
kind=d["kind"],
target=d["target"],
fingerprint=d.get("fingerprint") or {},
reason=d.get("reason", ""),
actor=d.get("actor", "unknown"),
accepted_at=d.get("accepted_at", ""),
expires_at=d.get("expires_at"),
status=d.get("status", "ok"),
)
class ReconcileStore:
"""Owns the acknowledgement store: I/O, fingerprint checks, alert filtering.
Loaded through an mtime cache so the daemon never re-reads or re-parses an
unchanged file. Fails closed: a missing or corrupt store applies no acks and
every alert flows through normally.
"""
# path -> (mtime, parsed record dicts). Shared so repeated loads of an
# unchanged file skip the disk read and JSON parse entirely.
_CACHE: dict[str, tuple[float, list[dict]]] = {}
def __init__(self, cfg: Config, records: dict[tuple[str, str], Record]):
self.cfg = cfg
self._records = records
self._dirty = False
# -- locating / loading ------------------------------------------------
@staticmethod
def store_path(cfg: Config) -> Path:
return Path(cfg.reconcile_store) if cfg.reconcile_store \
else cfg.log_dir / "reconciliation.json"
@classmethod
def invalidate_cache(cls) -> None:
cls._CACHE.clear()
@classmethod
def load(cls, cfg: Config) -> "ReconcileStore":
path = cls.store_path(cfg)
try:
mtime = path.stat().st_mtime
except OSError:
return cls(cfg, {})
cached = cls._CACHE.get(str(path))
if cached and cached[0] == mtime:
raw = cached[1]
else:
raw = cls._read_records(path)
cls._CACHE[str(path)] = (mtime, raw)
records: dict[tuple[str, str], Record] = {}
for d in raw:
try:
rec = Record.from_dict(d)
except (KeyError, TypeError):
continue
records[rec.identity] = rec
return cls(cfg, records)
@staticmethod
def _read_records(path: Path) -> list[dict]:
try:
data = json.loads(path.read_text())
except (OSError, ValueError):
return [] # fail closed: corrupt store applies no acks
recs = data.get("records") if isinstance(data, dict) else None
return recs if isinstance(recs, list) else []
# -- mutation ----------------------------------------------------------
def accept(self, kind: str, target: str, fingerprint: dict, reason: str,
actor: str, expires_at: datetime | None = None) -> bool:
"""Record (or update) an acceptance. Returns True if one already existed."""
existed = (kind, target) in self._records
self._records[(kind, target)] = Record(
kind=kind, target=target, fingerprint=fingerprint,
reason=reason, actor=actor, accepted_at=_iso(_utcnow()),
expires_at=_iso(expires_at) if expires_at else None, status="ok",
)
self._write()
return existed
def revoke(self, kind: str, target: str) -> bool:
"""Drop an acceptance. Returns False if the target wasn't present."""
if (kind, target) in self._records:
del self._records[(kind, target)]
self._write()
return True
return False
# -- queries -----------------------------------------------------------
def list(self, stale_only: bool = False, live_fps: dict | None = None,
now: datetime | None = None) -> list[Record]:
"""All records, re-evaluating staleness against TTL and any supplied
live state. Persists newly detected transitions (the lazy write-back).
TTL expiry is always authoritative. A content-bound (fim/pkgfile) ack is
only re-checked when ``live_fps`` actually carries that kind's data; with
no live data the command didn't look, so the persisted status stands
rather than being fabricated stale.
"""
now = now or _utcnow()
live_fps = live_fps or {}
for rec in self._records.values():
self._refresh_listed(rec, live_fps, now)
self.flush_stale()
out = [r for r in self._records.values()
if not stale_only or r.status == "stale"]
return sorted(out, key=lambda r: (r.kind, r.target))
# -- filtering (the daemon/web/CLI chokepoint) -------------------------
def filter_alerts(self, alerts: list[Alert], live_fps: dict | None = None,
now: datetime | None = None) -> list[Alert]:
"""Drop alerts that a still-valid acknowledgement covers.
Acks whose live fingerprint diverged or whose TTL lapsed are marked
stale in memory (written back lazily) and their alert flows through.
"""
live_fps = live_fps or {}
now = now or _utcnow()
out: list[Alert] = []
for a in alerts:
kind, target = alert_identity(a.key)
rec = self._records.get((kind, target)) if kind else None
if rec is None or not self._refresh(rec, live_fps, now):
out.append(a)
return out
# -- staleness ---------------------------------------------------------
def _refresh(self, rec: Record, live_fps: dict, now: datetime) -> bool:
"""Re-evaluate one record; update its cached status. Returns True if the
ack is still valid (alert should be suppressed)."""
valid = self._is_valid(rec, live_fps, now)
status = "ok" if valid else "stale"
if rec.status != status:
rec.status = status
self._dirty = True
return valid
@staticmethod
def _is_valid(rec: Record, live_fps: dict, now: datetime) -> bool:
expiry = rec.expiry()
if expiry and now >= expiry:
return False
if rec.kind in ("fim", "pkgfile"):
live = (live_fps.get(rec.kind) or {}).get(rec.target)
return build_fingerprint(rec.kind, rec.target, live) == rec.fingerprint
return True # identity kinds: presence + unexpired is enough
def _refresh_listed(self, rec: Record, live_fps: dict,
now: datetime) -> None:
"""Status re-evaluation for ``list``: TTL is authoritative, but a
content kind with no supplied live data keeps its persisted status."""
expiry = rec.expiry()
if expiry and now >= expiry:
status = "stale"
elif rec.kind in ("fim", "pkgfile"):
if rec.kind not in live_fps:
return # not checked this run; leave the recorded status as-is
live = (live_fps.get(rec.kind) or {}).get(rec.target)
status = "ok" if build_fingerprint(
rec.kind, rec.target, live) == rec.fingerprint else "stale"
else:
status = "ok" # identity kind, unexpired
if rec.status != status:
rec.status = status
self._dirty = True
# -- persistence -------------------------------------------------------
def flush_stale(self) -> None:
"""Write pending in-memory stale transitions back to disk, if any."""
if self._dirty:
self._write()
def _write(self) -> None:
path = self.store_path(self.cfg)
path.parent.mkdir(parents=True, exist_ok=True)
payload = {
"schema": schemas.RECONCILE_V1,
"records": [r.to_dict() for r in
sorted(self._records.values(),
key=lambda r: (r.kind, r.target))],
}
tmp = path.with_name(path.name + ".tmp")
tmp.write_text(json.dumps(payload, indent=2))
os.replace(tmp, path)
self._dirty = False
# Drop the cache entry so the next load re-reads the file we just wrote.
self._CACHE.pop(str(path), None)