The t_rename_secure / t_symlink_secure / t_acl unit harnesses (C), the rsyncfns.py
helper library (daemon fixtures, symlink matrix, tree compare, xattr/ACL drivers),
runtests.py, and the rsync_proto/xrsync/cmptree/mkvariety helper scripts that the
security tests build on.
Android's seccomp sandbox traps openat2() with SECCOMP_RET_TRAP, which
raises SIGSYS and kills the process instead of returning ENOSYS, so the
secure resolver cannot simply try openat2() and inspect errno. Add
openat2_usable() in a new android.c: it probes openat2() once behind a
temporary SIGSYS handler and caches the result.
Gate every SYS_openat2 call on openat2_usable(): in the resolver via an
openat2_beneath() wrapper, and in t_chmod_secure's kernel probe directly,
so a blocked openat2 reports ENOSYS and the caller falls back to the
portable O_NOFOLLOW resolver. Only openat2 is gated -- a plain openat()
(e.g. opening an operator-trusted absolute basedir) is left free.
The probe body compiles only on Android -- __ANDROID__ is a Bionic target
macro, so it is set for NDK cross-builds and native Termux alike and unset
everywhere else, where openat2_usable() collapses to a constant 1. Link
android.o into the secure-resolver test helpers too so their self-tests
survive on Termux.
Adapted from PR #909.
To prevent using openat2() in situations where it is not supported, use
#if defined(__linux__) && defined(HAVE_OPENAT2)
in t_chmod_secure.c, just like it was already being done in syscall.c.
Signed-off-by: Markus Mayer <mmayer@broadcom.com>
The chmod-symlink-race test was previously a no-op on Solaris,
OpenBSD, NetBSD, and Cygwin via a case 'uname -s' skip. The skip
was too broad: of the four scenarios the helper exercises, only
the 'legitimate within-tree dir-symlink' one actually needs
RESOLVE_BENEATH-equivalent kernel support. The other three
(attack rejection, plain relative path, top-level file) behave
identically on the per-component O_NOFOLLOW fallback and would
have caught the t_stub.c max_alloc=0 bug fixed in the previous
commit if the test had been allowed to run.
Make the helper probe the running kernel for either
openat2(RESOLVE_BENEATH) on Linux 5.6+ or openat(O_RESOLVE_BENEATH)
on FreeBSD 13+ / macOS 15+ by opening '.' under the requested
confinement. Honour the result:
- If RESOLVE_BENEATH-equivalent confinement is available, the
within-tree symlink scenario must succeed (status quo).
- If not, the per-component O_NOFOLLOW fallback rejects every
symlink including legitimate ones; expect the within-tree
symlink scenario to be rejected (rc != 0) and the file mode
to remain unchanged.
The attack-rejection, plain-path and top-level scenarios are
unchanged: they expect the same outcome on both code paths.
Drop the case-based skip from chmod-symlink-race.test so the test
runs everywhere and the per-component fallback gets the CI
coverage that the SunOS/OpenBSD/NetBSD/Cygwin runners can
provide. HPE NonStop -- which lacks RESOLVE_BENEATH but isn't in
the existing skip list -- is also covered by this change.
CVE-2026-29518's fix routed the receiver's open() through
secure_relative_open(), but every other path-based syscall the
receiver runs on sender-controllable paths is vulnerable to the
same TOCTOU primitive. This commit closes the chmod variant.
Add do_chmod_at() that opens the parent of fname under
secure_relative_open() and uses fchmodat() against the resulting
dirfd. Gate the secure path on am_daemon && !am_chrooted (the same
gate use_secure_symlinks already uses for the receiver basis-file
open), so non-daemon callers and chrooted daemons keep the original
do_chmod() fast path.
Migrate the receiver-side do_chmod() call sites in delete.c,
generator.c, rsync.c, and xattrs.c.
Adds testsuite/chmod-symlink-race.test (with t_chmod_secure helper)
as regression coverage.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Andrew Tridgell