Single-fork daemonize: the child calls setsid() itself rather than
re-enabling bwrap's own --new-session, which was previously removed
(and stays that way) because it only detaches the deeply-nested
sandboxed command, leaving bwrap/nsenter/slocker-lite itself still
attached to the original session -- not real daemonization. Calling
setsid() in slocker-lite's own forked child, before it execs into
nsenter/bwrap, detaches the whole chain at once, since exec() never
changes session membership -- confirmed via ps -o sid,pgid,tty against
a running daemonized session.
The child also ignores SIGHUP (confirmed to survive exec() into bwrap,
unlike a real handler, which exec() resets) and redirects stdin to
/dev/null and stdout/stderr to a log file under
$XDG_STATE_HOME/slocker-lite/logs/ (session_log_file_path(), new
sibling to the existing session_pid_file_path() in pid_file.{h,cpp}).
The original process blocks briefly on a pipe until the child reports
the real bwrap pid (or exits without doing so), then prints it and
exits -- keeping "pid" meaning the same thing everywhere in this
codebase (the same one --list-processes/-e/--exec already use), rather
than introducing a separate daemon-supervisor pid. run_bwrap() gained
an on_bwrap_pid_known callback (bwrap.{h,cpp}) for this, invoked
alongside the existing session-lock creation at the same instant.
The daemonized child is what runs run_container()'s entire existing
body afterward, including the unmount/cleanup that already ran once
bwrap exits -- no separate watcher/reaper process.
Testing caught a real bug before this was correct: the log file gets
renamed from its initial (daemon-pid-named) filename to the final
<container_name>-<bwrap-pid>.log once the real pid is known, but the
parent had already been told the pre-rename path and was never updated
-- fixed by re-reporting the path over the same pipe after the rename.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Gv3s5jckJKzh6JkMoi2Akz
Both flags are repeatable and share a single ordered EnvSpec list
(env_spec.{h,cpp}) so a later --env or --env-file always overrides an
earlier one for the same name, regardless of which flag set it.
--env-file reads one VAR=VALUE per line, skipping blank lines and
#-comments. resolve_env_specs()'s result is appended after
build_sandbox_env()'s own PATH/HOME/PWD/TERM defaults, letting an
explicit --env override any of them too.
Testing this surfaced a real bug in the environment-at-exec-time
mechanism from the previous change (dropping bwrap's own --clearenv):
since bwrap/nsenter are now exec'd with the same explicitly-built
environment the sandbox sees, a --env PATH=... override broke
execvp()'s ability to even locate bwrap/nsenter themselves (bare-name
PATH lookup happens in the child, using the already-overridden PATH).
Fixed by resolving both to absolute paths via find_in_path(), called
from this process's own unmodified environment before fork() --
confirmed by testing that only the sandboxed command's own lookup is
now affected by a PATH override, not bwrap/nsenter.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Gv3s5jckJKzh6JkMoi2Akz
Validates the given pid against the same tracked-session liveness
check --list-processes/--clean-processes already use, then joins its
namespaces via nsenter and runs a command there in the foreground.
Two things discovered only by testing against a live session, not
assumed up front:
- The tracked pid is bwrap's own outer process. It sets up the
mount/user namespaces itself, then clone()s the actual sandboxed
command into fresh pid/uts/ipc/cgroup namespaces -- clone()'s
namespace flags only ever affect the new child, never the caller,
so the outer process itself never enters those namespaces at all.
exec_in_session() resolves that real child via
/proc/<pid>/task/<pid>/children and joins its namespaces instead,
falling back to the outer pid if that can't be read.
- Rather than nsenter -a (which would hit a known "Invalid argument"
failure re-entering an identical namespace -- this project already
worked around exactly that once, for the containers-storage mount
path), each namespace type is only joined if
/proc/<pid>/ns/<type> actually differs from this process's own.
nsenter also needs --preserve-credentials, or it tries to
setuid/setgid/setgroups to the target's identity, which fails
outright against the setgroups-denied unprivileged user namespace
bwrap creates whenever -r/--run isn't root.
Verified end-to-end: joined shell gets the container's own hostname,
process tree (ps shows only container processes), and root
filesystem; untracked/stale pids error out cleanly without touching
nsenter; Ctrl-C during the joined command doesn't disturb the
original session; no leftover mounts after either exits.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Gv3s5jckJKzh6JkMoi2Akz
Each bwrap session is now recorded under
$XDG_STATE_HOME/slocker-lite/run/<container-name>-<pid> (falling back
to $HOME/.local/state/...), holding an exclusive advisory flock() for
as long as it's running -- so any tool can tell a stale leftover file
apart from a live session by attempting the same non-blocking flock().
The file is removed once the run ends, on every exit path including a
forwarded Ctrl-C.
run_process_foreground() gained an optional on_start(pid) callback,
fired right after fork() succeeds -- the only point the real bwrap pid
is knowable, since exec() (including nsenter handing off to bwrap)
never changes it. run_bwrap() uses this to create/release the session
lock. The container name comes from read_image_ref(), promoted from a
list_oci_images()-only helper to public API in oci_image.h so
run_container() can reuse the same name/tag derivation for a single
image tar.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Gv3s5jckJKzh6JkMoi2Akz
Volume names now reject '/', which lets a -v spec used with -r be told
apart as either an existing named volume or a host directory path. -v
becomes repeatable with -r, each mounting a volume at an absolute
container path; if the host directory is empty and the image already
has content there, it's copied in first (preserving numeric
ownership/permissions/links/xattrs-ACLs, degrading gracefully with a
warning if the host filesystem doesn't support xattrs). The
existence-check and copy run through the same nsenter-wrapped
namespace bwrap itself needs, since a rootless containers-storage
mount's content isn't otherwise visible to this process at all.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Gv3s5jckJKzh6JkMoi2Akz
Reads $XDG_CONFIG_HOME/slocker-lite/config.yaml (falling back to
$HOME/.config/slocker-lite/config.yaml), organized into sections. Only
the "global" section's log-level is supported for now -- other options
are one-shot flags, not standing preferences. An explicit --log-level
on the command line always overrides the config file, the same way
SPDLOG_LEVEL already does.
Uses libyaml directly (yaml_dep was already declared in meson.build but
unused). A missing config file isn't an error; unknown sections/keys
are ignored for forward-compatibility; malformed YAML syntax is a hard
error.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Gv3s5jckJKzh6JkMoi2Akz
bwrap --uid/--gid require --unshare-user, which is never requested
when running as root (since last session's fix), and user namespaces
aren't a near-term option anyway -- the actual Android target doesn't
support them.
--user <name-or-uid> / --group <name-or-gid> work around this:
user_spec.cpp resolves them against the *mounted image's own*
/etc/passwd and /etc/group (names like "git" only mean anything inside
that image's user database), and bwrap.cpp bind-mounts a small helper
into the sandbox to do the actual privilege drop before exec'ing the
real command, since bwrap itself can't switch uid/gid without a user
namespace.
The helper has to be a separate, statically-linked binary
(priv_drop_helper.cpp -> slocker-lite-priv-drop, built with -static)
rather than slocker_lite's own binary: bind-mounting a dynamically
linked executable into an arbitrary container image fails ("error
while loading shared libraries") since that image's own /lib won't
have slocker_lite's dependencies. find_priv_drop_helper() locates it
next to slocker_lite's own binary; run_bwrap() fails fast if it's
missing rather than silently running as root.
Only works without a user namespace (root): under --unshare-user the
sandbox's uid map has only one valid entry, so the helper's own
setuid() fails cleanly there instead of doing nothing silently.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
-r/--run mounts an image, runs a command under bwrap in the
foreground (default /bin/sh, overridable via -- <command> [args...]),
then unmounts and cleans up when it exits. -c/--cleanup deletes a
layer and its ancestor chain from local storage (containers-storage
delete-layer, walking parents via `layer --json`), since -u only ever
unmounted.
bwrap needs to see the merged mount from inside the private namespace
containers-storage mount creates when running rootless; run_bwrap()
locates the live fuse-overlayfs process and runs bwrap via nsenter
into its namespaces. When running as root no such namespace exists
(containers-storage doesn't need to reexec for privilege), so nsenter
fails with EINVAL; detect geteuid() == 0 and skip it automatically
there. -n/--no-nsenter forces it off manually for any other case.
process.cpp gains run_process_foreground() (inherited stdio, for the
interactive bwrap run) and the relocated find_in_path(), now shared
with bwrap.cpp's nsenter lookup.
Also: meson test only ran -m, leaking a layer on every run; it now
runs tests/run_test.py, which drives mount -> umount -> cleanup and
fails if any step does.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Add detect_bwrap_unshare_args(), which probes the running kernel for
which namespace types (user, ipc, pid, net, uts, cgroup) can actually
be unshared and returns the matching bwrap --unshare-xxx flags. Each
probe forks a throwaway child to call unshare() so the calling
process's own namespaces are never touched. Needed because the target
device (Android, stock kernel) only supports a subset of namespace
types, so bwrap must be invoked with just the flags it can honor.
Temporarily wired into -t/--test so it can be exercised on-device
ahead of the real bwrap invocation; will be removed once that lands.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Replace the implicit single-argument invocation with getopt_long-based
flags: -m/--mount (existing mount flow, now explicit), -u/--umount
(unmounts a layer via containers-storage), -t/--test (stub),
-l/--log-level (runtime spdlog level), -h/--help, -V/--version.
--mount now also prints the top layer's ID so it can be passed to
--umount.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
slocker-lite validates an OCI Image Layout tar, imports its layers into
containers-storage's layer store in order, and mounts the assembled image
using fuse-overlayfs, printing the resulting merged path.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
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