All three were found by review and reproduced before fixing. Each let a run
report success while proving nothing -- the shape this harness exists to
prevent.
A reused prefix defeated dropped-write detection entirely. Run 1's files were
still there when run 2's manifest was taken, so the manifest reported writes
that never happened and the fixture pair diffed CLEAN. The doc's own examples
demonstrated that workflow. A non-empty prefix is now refused -- not deleted,
since the path is user-supplied -- and the examples use distinct prefixes.
A missing bwrap was swallowed. trace_prefix_bwrap_argv returned 1, but the
caller reads it through `mapfile < <(...)` and a process substitution's status
is discarded, so runner ended up empty and the run continued with no sandbox
and no uid 0. Same swallow as the grep-status one fixed earlier, one layer up.
bwrap is now probed in validate_requirements, before anything runs.
The absolute-path scan only fired when no --bind-abs was given at all, so
binding one path and missing three produced no warning. It now runs whenever
--prefix is given and reports only what is not already covered. Fixing that
surfaced a second defect: --bind-abs on a FILE aborted with "Can't mkdir
/etc/profile: Not a directory", and binding its parent reintroduced the
wholesale /etc shadowing this change had already measured as harmful ($SUDO_USER
collapsing to /home//, the real /etc/profile unreadable). Files are now bound
file-over-file, seeded with a copy so a script that greps before appending sees
real content.
Also measured rather than argued: the XDG redirect. A new fixture run with a
real XDG_DATA_HOME pointing at a decoy shows all four writes landing in the
prefix and the decoy empty -- the rsync --delete data-loss path, proven closed
without running install_leechblock.sh. And no-prefix output was diffed against
cdf2a55 from a detached worktree: byte-identical, so existing baselines hold.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_011w2Pj4Ek3ZNMQVYcFHgXDY
Shell redirections are builtins, so no PATH stub can intercept
`cat > /etc/modprobe.d/x.conf`. That left installer scripts unverifiable:
stub cp/chmod/ln and the trace is nearly empty, don't and the run rewrites
the live system.
--prefix redirects HOME and every XDG_* base into a temp tree. XDG_DATA_HOME
is exported explicitly, not left to default off HOME: install_leechblock.sh
reads it directly and then runs `rsync -a --delete` at it.
--bind-abs binds hardcoded absolutes via bwrap --unshare-user --uid 0, leaf
directories only. uid 0 is load-bearing beyond permissions: common.sh's
require_root does `exec sudo "$0"`, and under the sudo stub that truncated
the whole run to one recorded call -- a trace that diffs clean against any
split. Binding /etc wholesale was measured to shadow /etc/passwd, collapse
$SUDO_USER to /home//, and mask a nested bind, so the scanner never emits it.
The trace gains a manifest of every file written, with content hashes. That
section is the point: with it, a dropped write in the fixture pair is a
one-line diff; with it stripped, the two traces are identical, i.e. the old
harness passed that broken split. Hashes normalize the prefix to @PREFIX@
because install_usage_monitoring.sh writes an unquoted heredoc that bakes
$HOME into the artifact.
Verified: ~/.config/systemd/user, ~/.local/bin, ~/.local/share and
/etc/modprobe.d byte-identical before and after; usage-report units still 2.
The three prior regressions are now committed fixtures rather than ad-hoc --
one was silently neutered mid-change when a trailing echo added for SC2034
became the function's last statement and turned exit 1 into exit 0.
Stub generation moved to lib/ because --prefix pushed the harness to 252
lines, over the cap it exists to serve.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_011w2Pj4Ek3ZNMQVYcFHgXDY
