A clean laptop reported 988 critical rootkit findings; this server
3786, PID 1 among them. Every one was false, and the cause was our own
systemd hardening.
ProtectProc=invisible hides processes the daemon does not own from its
view of /proc, while kill(pid, 0) keeps answering truthfully because it
is a syscall and not a filesystem lookup. The hidden-process check
compares exactly those two sources, so with that setting every process
on the machine looked concealed. Enumerating processes is this daemon's
job, so it needs the default view.
Removing the setting is not enough on its own — hidepid= on the /proc
mount produces the same blindness and we do not control that. So the
detector now recognises when it cannot see:
- PID 1 is the control. It always exists and nothing hides init; a
rootkit that did would break the machine it is living on. If PID 1
answers kill(1, 0) but is absent from the listing, we are blind and
say so as info rather than crying rootkit.
- A plausibility ceiling of 32. Hiding a handful of processes is the
entire point of a rootkit; hundreds means a broken observer. An
antivirus that reports a critical rootkit finding on every clean
machine teaches people to ignore the one time it is real.
Also in this change, from testing on a real desktop:
- Closing the window hides it to the tray instead of exiting, with a
one-time notification so it does not read as a crash. Quit lives
only in the tray menu and confirms first. The settings already had
close_to_tray and confirm_quit fields wired to nothing; they are
honoured now rather than hardcoded.
- The tray menu and Scan Home sent the literal string "~". A shell
would have expanded it, nothing here did, so the daemon was asked
to scan a directory of that name. It failed silently until the
per-peer readability check made it audible.
- Administrative actions elevate through polkit instead of telling
people to open a terminal. The app tries unprivileged first and
only on a privilege refusal runs `pkexec hound admin-rpc`, which
forwards one request as root. auth_admin_keep, because prompting on
every settings toggle trains people to authenticate without reading
the prompt. This grants what `sudo hound` already grants to people
who could already run sudo — a transport, not a new privilege.
- `hound settings exec-gate on|off` now exists. The install script,
the AppImage banner, the rpm spec, the AUR install file and
llms.txt all told users to run `hound settings set exec_gate true`.
There was no `set` subcommand and no way to enable the execution
gate from the CLI at all: the flagship paid feature was unreachable
and the first thing a new user was told to type returned an error.
A test now asserts every documented command parses.
- `settings show` displays the exec gate state, and no longer prints
its own header twice.
- The CLI help still described ClamAV, which has not been the engine
for some time. So did the socket permission error, which now
explains the `hound` group and the log-out-and-back-in it needs.
368 tests pass.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Installed the .deb on the live server. The daemon did not start, and
everything below is what that one command surfaced.
1. MemoryDenyWriteExecute=yes stopped the service dead.
yara-x compiles rules to WebAssembly and JITs them, so it needs pages
that go writable then executable. With W^X enforced the daemon aborts
at startup: "unable to make memory executable". The unit had passed
systemd-analyze verify, which checks syntax and cannot know this.
Now off, with the reasoning in the unit rather than in a commit
nobody will read: a hardening directive that stops the service is
worse than the exposure it prevents, because the machine ends up with
no antivirus at all. What compensates is spelled out beside it.
2. Hound detected itself.
The goodware gate reported /usr/bin/houndd as Linux.Coinminer.XMRig
and Linux.Rootkit.Preload. Correctly: the built-in pack matches on
"stratum+tcp://", "xmrig", "RTLD_NEXT" and "ld.so.preload", and the
pack was embedded verbatim, so the daemon's own binary contained all
of them.
Not cosmetic. With the execution gate armed, Hound would have refused
to execute itself or quarantined its own binary — a scanner that eats
its own daemon the moment protection is switched on.
The pack is now XOR-masked at build time (build.rs) and unmasked at
startup. Not a secret — the rules are open source — the only job is
keeping the literal bytes out of the executable. Two regression tests:
the embedded blob carries no plaintext rule strings, and a built
daemon binary in target/ carries none either.
3. The postinst copied the built-in pack into /var/lib/hound/rules,
where the daemon compiled it a second time and logged a duplicate
declaration on every start. That directory is for ADDITIONAL packs;
the built-ins live in the binary. Removed from deb, rpm and AUR.
4. The daemon and the CLI disagreed about the socket. systemd gives the
service /run/hound; the CLI looked in $XDG_RUNTIME_DIR and reported
the daemon unreachable — technically true, entirely unhelpful.
default_socket_path() now prefers /run/hound when it exists, the unit
states HOUNDD_SOCK explicitly, and a permission error on the socket
says "try: sudo hound" instead of "Permission denied".
Also: Recommends: clamav-daemon was wrong and apt duly installed clamd,
which took 970 MB of RSS on the live server. clamd is an optional
arm's-length engine, so it is a Suggests. I stopped and disabled the
copy my install pulled in.
Verified on the server after fixing: service active, status reports the
engine and the gate, EICAR caught, rootkit scan clean, and the goodware
gate passes across 3,955 system binaries including the now-installed
houndd.
The gate remains OFF. Turning it on for the host that serves Caddy is a
separate decision.
295 tests pass.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
dev