authforge/pam/TESTING.md

Testing pam_authforge_pending.so

This module gates first-login enrollment. Its full behavior is impossible to exercise from a unit test because PAM modules run inside a real PAM stack that needs root to install. The recipe below runs in a VM or container with libpam0g-dev and pamtester installed.

Build + install

sudo apt-get install -y libpam0g-dev libargon2-dev pamtester
sudo make -C pam install
sudo install -D -m 0644 pam/test/authforge.pamd /etc/pam.d/authforge

libargon2-dev is required for the recovery-mode verification path (Phase 12).

make install drops the .so into /usr/lib/$(dpkg-architecture -qDEB_HOST_MULTIARCH)/security/.

Smoke test 1: pending flag present → denied

sudo mkdir -p /var/lib/authforge/pending
sudo touch /var/lib/authforge/pending/$USER
pamtester -v authforge "$USER" authenticate
# Expect: "Account setup incomplete..." printed and a non-zero exit code.

Smoke test 2: pending flag cleared → falls through

sudo rm /var/lib/authforge/pending/$USER
pamtester -v authforge "$USER" authenticate
# Expect: success (the test PAM stack file falls through to pam_unix after
# our PAM_IGNORE; pamtester will prompt for the user's password).

Smoke test 3: path-traversal regression

The guard in safe_user rejects names that break the path-as-identifier invariant: empty strings, ., .., anything containing / or NUL. Anything else passes through — including unusual but legitimate names that contain .. as a substring (LDAP / federated identities can produce these). The loop below mixes both classes; the assertions live in the comments:

for u in "../etc" "a/b" "" "." ".." "x..y"; do
    pamtester -v authforge "$u" authenticate 2>&1 | head -3
    echo "---"
done
# Expect rejected (logged "rejected unsafe username"): ../etc, a/b, "", ., ..
# Expect passed through (no rejection log; pam_unix runs and prompts):  x..y

Keeping x..y in the loop is intentional — it documents the boundary and acts as a regression test against accidental over-rejection if the guard is ever tightened.

Future hardening (deferred — not blocking v1): the guard is a cheap pre-filter, not the authoritative boundary. A belt-and-suspenders pattern would be canonicalize-then-verify: build the per-user path, resolve it via fs::canonicalize (Rust) / realpath (C), and confirm the resolved path is still under the expected parent directory. That covers symlink shenanigans and any future ..-substring attack surface uniformly. Track as a Phase 17 item.

The module logs via pam_syslog without setting its own openlog ident, so journal entries inherit the calling process's syslog identifier: pamtester here, sudo / sshd / gdm / login in production. The module name appears in the message body, so the always-works query is to grep for the literal string:

journalctl --since "10 minutes ago" --no-pager | grep authforge_pending

For pamtester runs specifically, journalctl -t pamtester works too. Older systems that route pam_syslog to /var/log/auth.log show the same lines there.

Smoke test 4: recovery-code path (Phase 12)

The module's recovery branch activates when invoked with mode=recovery in the PAM stack. The pam-auth-update profile rendered by Phase 4 puts this line first in the auth stack — a successful recovery code short-circuits the rest of the auth chain via [success=done default=ignore].

To exercise it manually with pamtester against a custom stack:

# 1. Issue a code via the daemon and stash the plaintext.
CODE=$(sudo authforgectl recovery generate "$USER" | tr -d '\n')
echo "issued $CODE"

# 2. Build a PAM stack file that runs ONLY the recovery-mode module.
sudo tee /etc/pam.d/authforge-recovery <<'EOF'
auth [success=done default=ignore] pam_authforge_pending.so mode=recovery
auth required                       pam_deny.so
EOF

# 3. Verify a matching code authenticates.
echo "$CODE" | pamtester -v authforge-recovery "$USER" authenticate
# Expect: PAM_SUCCESS, /var/lib/authforge/recovery/$USER deleted, and
# /var/lib/authforge/pending/$USER now contains re_enroll: true.

# 4. Verify a non-matching code falls through to pam_deny.
echo "$CODE" | pamtester -v authforge-recovery "$USER" authenticate
# Expect: failure (pam_deny) — the recovery file was already consumed.

# 5. Cleanup.
sudo rm /etc/pam.d/authforge-recovery /var/lib/authforge/pending/$USER

The recovery file is at /var/lib/authforge/recovery/<user> mode 0600. The two-line format is <expires_unix>\n<argon2id-PHC>\n.

CI status

CI cannot run pamtester against a real PAM stack without root and a VM, so this is the last manual gate before the Phase 14 PPA build. The CI pipeline only verifies that make -C pam produces a valid ELF.