0eb5077551
Closes polling's blind spot (processes that exit between sweeps) with a real
eBPF probe and a declarative, data-driven detection engine — inspired by Snort
(rule language, signature IDs) and OSSEC (host-IDS framing).
New events/ subpackage:
- bcc_source.py : eBPF C tracing execve (filename, argv[1..2], ppid, uid,
parent comm) over a perf buffer, loaded via bcc; lazy import
+ available()/try-except so it fails closed to poll-only when
bcc/root/BTF are absent — a broken probe never downs the daemon
- exec_event.py : the ExecEvent type
- rules.py : ExecRule (sid/msg/severity/classtype + path/exec/parent/argv
conditions) and ExecRuleEngine; 4 shipped rules (fileless exec
100001, reverse-shell argv 100002, web/DB→shell RCE 100003,
curl|sh 100004); operators add more via exec_rules_file TOML
- monitor.py : runs the source on a thread, routes events through the engine
Integration:
- daemon starts the monitor, shares a lock-guarded cooldown with the sweep
loop, and feeds event alerts into the same snapshot pipeline
- Alert gains Snort-style sid + classtype; retrofitted onto all 7 poll
detectors; snapshots and JSON now carry them
- config: ebpf_exec_monitor (default on, degrades), exec_rules_file
- systemd: opt-in ebpf.conf drop-in (relaxes MemoryDenyWriteExecute + widens
caps for bcc's JIT) so the base unit stays hardened for poll-only
- sentinel-redteam: ebpf_exec drill (short-lived /tmp exec + /dev/tcp argv the
poller can't see); footer now uses the Python CLI
Tests: +14 cases for the rule engine (each default rule match/non-match, rule
validation, parent-exclude). 39/39 pass. Graceful non-root degradation verified.
NOTE: the eBPF C follows bcc's execsnoop pattern but could not be run here
(BPF needs root); it wants a root smoke-test on a real host.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
42 lines
1.3 KiB
Python
42 lines
1.3 KiB
Python
# SPDX-License-Identifier: GPL-3.0-or-later
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"""deleted_exe — a process running from a deleted or memfd-backed binary.
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Fileless malware unlinks its dropper (or runs straight from ``memfd``) so there
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is nothing on disk to scan. The kernel still labels the ``/proc/<pid>/exe``
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symlink ``(deleted)`` or ``memfd:``. Normal-path deleted exes (a daemon still
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running after a package upgrade) are ignored — only attacker-controlled/fileless
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locations alert.
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"""
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from __future__ import annotations
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from collections.abc import Iterator
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from ..alert import Alert, Severity
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from ..config import Config
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from ..system import SystemState
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_SUSPICIOUS_PREFIXES = ("/tmp/", "/dev/shm/", "/var/tmp/", "/run/")
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def _is_fileless(exe: str) -> bool:
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if "memfd:" in exe:
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return True
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if "(deleted)" not in exe:
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return False
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return exe.startswith(_SUSPICIOUS_PREFIXES)
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def detect(state: SystemState, cfg: Config) -> Iterator[Alert]:
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for proc in state.processes:
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exe = proc.exe
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if not exe or not _is_fileless(exe):
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continue
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yield Alert(
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severity=Severity.CRITICAL,
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signature="deleted_exe",
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key=f"del:{proc.pid}",
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detail=f"pid={proc.pid} comm={proc.comm} exe=[{exe}]",
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pids=(proc.pid,),
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sid=100012,
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classtype="fileless-execution",
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)
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