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>
40 lines
1.4 KiB
Python
40 lines
1.4 KiB
Python
# SPDX-License-Identifier: GPL-3.0-or-later
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"""reverse_shell — an interpreter with a network socket on its stdio.
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A real reverse shell dups a TCP/UDP socket onto fd 0/1/2 (``nc -e /bin/bash``,
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``bash -i >& /dev/tcp/...``). Interactive shells get a pty, and daemons get
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unix sockets/pipes — neither is a network socket, so requiring the stdio socket
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to appear in the network socket table is what keeps false positives near zero.
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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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def detect(state: SystemState, cfg: Config) -> Iterator[Alert]:
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peer_by_inode = state.net_peer_by_inode
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for proc in state.processes:
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if proc.comm not in cfg.interpreters:
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continue
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inode = proc.stdio_socket_inode()
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if inode is None:
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continue
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peer = peer_by_inode.get(inode)
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if not peer: # unix socket / pipe — benign
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continue
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yield Alert(
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severity=Severity.CRITICAL,
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signature="reverse_shell",
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key=f"rsh:{proc.pid}",
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detail=(
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f"pid={proc.pid} comm={proc.comm} stdio=net-socket "
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f"peer=[{peer}] cmd=[{proc.cmdline[:90]}]"
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),
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pids=(proc.pid,),
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sid=100010,
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classtype="c2-reverse-shell",
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)
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