Commit 797e17f ("fixed an invalid access to files array") added a
parent_ndx < 0 guard to send_files() in sender.c, but the visually-
identical block in recv_files() in receiver.c was not updated. A
malicious rsync:// server can therefore drive any connecting client
into the same out-of-bounds dir_flist->files[-1] read followed by a
file_struct dereference in f_name() one line later.
Reach: protocol-30+ default (inc_recurse) makes flist.c:2745 set
parent_ndx = -1 on the first received flist when the sender omits a
leading "." entry; rsync.c flist_for_ndx() does not reject ndx == 0
in that state because the range check evaluates 0 < 0 = false; and
read_ndx_and_attrs() only validates ndx with the ITEM_TRANSFER bit
set, so iflags=ITEM_IS_NEW (or any other non-transfer iflag word)
bypasses the check.
Apply the same guard receiver-side. Confirmed: the same PoC (a
minimal Python rsyncd that handshakes with CF_INC_RECURSE, sends a
no-leading-"." flist, and emits ndx=0 with ITEM_IS_NEW) crashes
unpatched 3.4.2 with SEGV_MAPERR si_addr=0x4101a-class in the
receiver child; with this guard it exits cleanly with code 2
(RERR_PROTOCOL).
The attack surface delta over the sender variant is large:
the original was malicious-client -> daemon, this is
malicious-server -> any rsync client doing a normal rsync://
or remote-shell pull.
Reported by Pratham Gupta (alchemy1729).
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Add a daemon-refuse-compress test that builds a module configured with
'refuse options = compress' and asserts that:
1. an attempted -z transfer to that module fails with an error
mentioning --compress, and
2. the same transfer without -z still succeeds.
This pins down the documented way to disable all compression on a
daemon, which previously had no automated coverage.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
The receiver's three compressed-token decoders --
recv_deflated_token (zlib), recv_zstd_token, and
recv_compressed_token (lz4) -- accumulated rx_token (a 32-bit
signed counter) without overflow checking. A malicious sender
could craft a compressed-token stream that walked rx_token past
INT32_MAX, with careful manipulation leaking process memory
contents to the wire (environment variables, passwords, heap
pointers, library pointers -- significantly weakening ASLR
and facilitating further exploitation).
Cap rx_token at MAX_TOKEN_INDEX = 0x7ffffffe. Fold the
bookkeeping into recv_compressed_token_num() and
recv_compressed_token_run() shared by all three decoders. Reject
negative or out-of-range token values explicitly. Also cap the
simple_recv_token literal-block length at the source: any
wire-supplied length > CHUNK_SIZE is ill-formed (the matching
simple_send_token never writes a chunk larger than CHUNK_SIZE),
so reject before looping on attacker-controlled bytes.
Reach: an authenticated daemon connection with compression
enabled (the default for protocols >= 30 when both peers
advertise it). Disabling compression on the daemon
("refuse options = compress" in rsyncd.conf) is the available
workaround.
Reporter: Omar Elsayed (seks99x).
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
testsuite/chdir-symlink-race.test runs an actual rsync daemon
(via RSYNC_CONNECT_PROG to avoid the network) configured with
"use chroot = no", plants a symlink at module/subdir -> ../outside,
and runs four flavours of attacker-shaped transfer (single-file
poc_chmod, -r push into the symlinked subdir with --size-only and
without, -r push into the module root). All four must leave the
outside-the-module sentinel file's mode AND content unchanged.
Portability:
- file_mode() helper falls back to BSD stat -f %Lp when GNU
stat -c %a is unavailable (macOS, FreeBSD).
- Pre-saved pristine copy + cmp(1) replaces sha1sum, which
differs across platforms (sha1sum / shasum / sha1).
Tests are kept running as root in the user-namespace re-exec
wrapper used by symlink-race tests so the daemon's setuid path
doesn't drop into the test user's identity (which on Linux
would mean the chmod-escape code path can't trigger because
the test user doesn't have CAP_FOWNER over the outside file).
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Three related codex audit findings:
Finding 3a: copy_file()'s source open in util1.c used
do_open_nofollow(), which only rejects a final-component
symlink. A parent-component symlink (e.g. --copy-dest=cd where
cd -> /outside) follows freely and reads outside the module.
Route through secure_relative_open() with O_NOFOLLOW.
Finding 3b: generator.c's in-place backup-file create still
used a bare do_open with O_CREAT, leaving a tiny but reachable
parent-symlink window between the secure unlink (already
through do_unlink_at) and the create. Add do_open_at() that
goes through a secure parent dirfd, and route the call site
through it.
Finding 3c: copy_file()'s destination open in
unlink_and_reopen() had the same bare-do_open pattern; route
through do_open_at as well.
Adds testsuite/copy-dest-source-symlink.test and
testsuite/bare-do-open-symlink-race.test as regression coverage
for both attack shapes.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Add the rest of the path-based syscall wrappers and migrate every
receiver-side caller:
- do_lchown_at, do_rename_at, do_mkdir_at, do_symlink_at,
do_mknod_at, do_link_at, do_unlink_at, do_rmdir_at,
do_utimensat_at, do_stat_at, do_lstat_at
Same shape as do_chmod_at: open each parent under
secure_relative_open(), call the *at() variant against the dirfd,
fall through to the bare path-based syscall in non-daemon /
chrooted / absolute-path / no-parent cases. macOS's
setattrlist-based set_times tier is also routed through the
utimensat_at path on daemon-no-chroot.
Hardenings to secure_relative_open() itself:
- confine basedir resolution under the same kernel mechanism
used for relpath (basedirs from --copy-dest / --link-dest are
sender-controllable in daemon mode)
- reject any '..' component (bare '..', 'foo/..', 'subdir/..')
so the per-component O_NOFOLLOW fallback can't escape
- return the dirfd we built up from the per-component fallback
when the caller passed O_DIRECTORY (otherwise every do_*_at
failed with EINVAL on platforms without RESOLVE_BENEATH)
Adds testsuite/alt-dest-symlink-race.test and
testsuite/secure-relpath-validation.test (with t_secure_relpath
helper) as regression coverage for the new hardenings.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
The receiver's chdir(2) into a destination subdirectory followed
attacker-planted symlinks at every path component. Once CWD
escaped the module, every subsequent path-relative syscall (open,
chmod, lchown, ...) inherited the escape -- defeating
secure_relative_open's RESOLVE_BENEATH anchor against AT_FDCWD,
since the anchor itself was now outside the module.
Route change_dir's relative target through secure_relative_open()
and fchdir() to the resulting dirfd in am_daemon && !am_chrooted
mode, so the chdir step itself can no longer follow a parent-
symlink. Same treatment applied to the CD_SKIP_CHDIR /
set_path_only path so it also can't follow attacker symlinks
during path tracking.
Adds testsuite/sender-flist-symlink-leak.test covering the
sender-side flist resolution variant of the same primitive.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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>
The sender's file open was vulnerable to the same TOCTOU symlink
race as the receiver-side basis-file open. change_pathname() calls
chdir() into subdirectories, which follows symlinks; an attacker
could race to swap a directory for a symlink between the chdir and
the file open, allowing reads of privileged files through the
daemon.
Reconstruct the full relative path (F_PATHNAME + fname) and open
via secure_relative_open() from the trusted module_dir, which
walks each path component without following symlinks. This is
independent of CWD, so the chdir race is neutralised.
CVE-2026-29518.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
CVE-2026-29518: an rsync daemon configured with "use chroot = no"
is exposed to a TOCTOU race on parent path components. A local
attacker with write access to a module can replace a parent
directory component with a symlink between the receiver's check
and its open(), redirecting reads (basis-file disclosure) and
writes (file overwrite) outside the module. Under elevated daemon
privilege this allows privilege escalation. Default
"use chroot = yes" is not exposed.
Add secure_relative_open() in syscall.c. It walks the parent
components under RESOLVE_BENEATH (Linux 5.6+) /
O_RESOLVE_BENEATH (FreeBSD 13+, macOS 15+) / per-component
O_NOFOLLOW elsewhere, anchored at a trusted dirfd, so a parent-
symlink swap is rejected by the kernel. Route the receiver's
basis-file open in receiver.c through it when use_secure_symlinks
is set in clientserver.c rsync_module().
Reporters: Nullx3D (Batuhan SANCAK); Damien Neil; Michael Stapelberg.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
secure_relative_open() has a kernel-enforced "stay below dirfd" path
on Linux 5.6+ (openat2 RESOLVE_BENEATH) and FreeBSD 13+ (openat
O_RESOLVE_BENEATH). On Solaris, OpenBSD, NetBSD, and Cygwin the code
falls back to the per-component O_NOFOLLOW walk, which by design
rejects every directory symlink in the path -- the very case this
test exercises. Mark the test skipped there rather than have it
fail with a known regression that's tracked separately.
macOS is intentionally not in the skip list: although it does not
have O_RESOLVE_BENEATH either, the test passes there in practice;
investigation of the underlying reason is left as follow-up.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
FreeBSD and MacOS have O_RESOLVE_BENEATH as an openat() flag with the same
"must not escape dirfd" semantics as Linux's RESOLVE_BENEATH. The
kernel rejects ".." escapes, absolute symlinks, and symlinks whose
target lies outside dirfd, while still following symlinks that
resolve within it -- the same trade-off that fixes issue #715 on
Linux.
Add a parallel BSD path in secure_relative_open(), gated on
declared. Unlike Linux, BSD doesn't have the header/runtime split
where the symbol can exist without kernel support, so no runtime
fallback is needed: if the flag compiles in, the kernel honours it.
OpenBSD and NetBSD have no equivalent kernel primitive and continue
to use the existing per-component O_NOFOLLOW walk; issue #715
remains visible on those platforms (a userland resolver or
unveil(2)-based fence would be follow-up work).
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
The CVE fix in commit c35e283 made secure_relative_open() walk every
component of relpath with O_NOFOLLOW. That blocks every symlink in the
path, which is stricter than the threat model required: legitimate
directory symlinks within the destination tree (e.g. when using -K /
--copy-dirlinks) are also rejected, breaking delta transfers with
"failed verification -- update discarded". See issue #715.
On Linux 5.6+, openat2(RESOLVE_BENEATH | RESOLVE_NO_MAGICLINKS) gives
us exactly what we want: the kernel rejects any resolution that would
escape the starting directory (via "..", absolute paths, or symlinks
pointing outside dirfd) while still following symlinks that resolve
within it. /proc magic-links are blocked too.
Use openat2 first; fall back to the existing per-component O_NOFOLLOW
walk on ENOSYS (kernel < 5.6). The lexical "../" checks at the head
of the function are kept as defense in depth. The Linux gate is
plain #ifdef __linux__: the runtime ENOSYS fallback covers the only
case that actually matters (header present + old kernel), and any
Linux build environment without linux/openat2.h will fail with a
clear "no such file" error rather than silently disabling the
protection.
Verified manually that openat2(RESOLVE_BENEATH) blocks all four
escape patterns (absolute symlink, ../ symlink, lexical .., absolute
path) while allowing direct and within-tree symlinks. The new
testsuite/symlink-dirlink-basis.test (taken from PR #864 by Samuel
Henrique) exercises the issue #715 regression and passes; full
make check passes 47/47.
Test: testsuite/symlink-dirlink-basis.test (8 scenarios)
Fixes: https://github.com/RsyncProject/rsync/issues/715
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
The Solaris xls() function listed every entry in the file's xattr
directory, which on Solaris includes OS-managed SUNWattr_ro and
SUNWattr_rw pseudo-attributes. SUNWattr_rw embeds the file creation
time, so its bytes naturally differ between the source and destination
files, making the xattrs and xattrs-hlink tests fail with diffs that
have nothing to do with rsync.
Rsync's own listxattr wrapper already filters these out
(lib/sysxattrs.c), so the right fix is to filter them in the test
display too. Other platforms are unaffected because each has its own
xls() branch in the case statement.
With the test now actually passing on Solaris, drop the CI hack that
overwrote testsuite/xattrs.test with a skip stub.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
localtime/localtime_r need /etc/localtime for timezone info.
After chroot this file is inaccessible, causing log timestamps
to fall back to UTC. Calling tzset() before chroot ensures the
timezone data is cached by glibc for subsequent calls.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
this fixes the count passed to the sort of the xattr list. This issue
was reported here:
https://www.openwall.com/lists/oss-security/2026/04/16/2
the bug is not exploitable due to the fork-per-connection design of
rsync, the attack is the equivalent of the user closing the socket
themselves.
Change my_alloc() to use calloc instead of malloc so all fresh
allocations return zeroed memory. Also zero the expanded portion
in expand_item_list() after realloc, since it knows both old and
new sizes. This gives more predictable behaviour in case of bugs
where uninitialised or stale memory is accidentally accessed.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
The len field in the proxy v2 header was declared as signed char,
allowing a negative size to bypass the validation check and cause
a stack buffer overflow when passed to read_buf() as size_t.
This bug was reported by John Walker from ZeroPath, many thanks for
the clear report!
With the current code this bug does not represent a security issue as
it only results in the exit of the forked process that is specific to
the attached client, so it is equivalent to the client closing the
socket, so no CVE for this, but it is good to fix it to prevent a
future issue.
The bundled zlib 1.2.8 used K&R-style function definitions which are
rejected by clang 16+ as hard errors. Convert all 90 functions across
9 files to ANSI-style prototypes.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Glibc 2.43 added C23 const-preserving overloads to various string functions,
which change the return type depending on the constness of the argument(s).
Currently this leads to warnings from calls to strtok() or strchr().
Fix this by properly declaring the respective variable types.
Signed-off-by: Holger Hoffstätte <holger@applied-asynchrony.com>
The AVX2 get_checksum1_avx2_64() read mul_one before initializing it,
which is undefined behavior. Replace the cmpeq/abs trick with
_mm256_set1_epi8(1) to match the SSSE3 and SSE2 versions.
Add a TEST_SIMD_CHECKSUM1 test mode that verifies all SIMD paths
(SSE2, SSSE3, AVX2, and the full dispatch chain) produce identical
results to the C reference, across multiple buffer sizes with both
aligned and unaligned buffers.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Validate that token numbers read from compressed streams are
non-negative. A negative token value would cause the return value
of recv_*_token() to become positive, which callers interpret as
literal data length, but no data pointer is set on this code path.
While this only causes the receiver to crash (which is process-isolated
and only affects the attacker's own connection), it's still undefined
behavior.
Reported-by: Will Sergeant <wlsergeant@gmail.com>
The static buf1 pointer was only allocated when len > len1, but on
first call with len == 0, this condition is false (0 > 0), leaving
buf1 NULL when passed to memcpy().
Fixes#673
this was found by Calum Hutton from Rapid7. It is a real bug, but
analysis shows it can't be leverged into an exploit. Worth fixing
though.
Many thanks to Calum and Rapid7 for finding and reporting this
In 2015, the attr/xattr.h header was fully removed from upstream attr.
In 2020, rsync started preferring the standard header, if it exists:
https://github.com/RsyncProject/rsync/pull/22
But the fix was incomplete. We still looked for the getxattr function in
-lattr, and used it if -lattr exists. This was the case even if the
system libc was sufficient to provide the needed functions. Result:
overlinking to -lattr, if it happened to be installed for any other
reason.
```
checking whether to support extended attributes... Using Linux xattrs
checking for getxattr in -lattr... yes
```
Instead, use a different autoconf macro that first checks if the
function is available for use without any libraries (e.g. it is in
libc).
Result:
```
checking whether to support extended attributes... Using Linux xattrs
checking for library containing getxattr... none required
```
Signed-off-by: Eli Schwartz <eschwartz@gentoo.org>
If poptGetContext returns NULL, perhaps due to OOM,
a NULL pointer is passed into poptReadDefaultConfig()
which in turns SEGVs when trying to dereference it.
This was found using https://github.com/sahlberg/malloc-fail-tester.git
$ ./test_malloc_failure.sh rsync -Pav crash crosh
Signed-off-by: Ronnie Sahlberg <ronniesahlberg@gmail.com>
Int32x32To64 macro internally truncates the arguments to int32,
while time_t is 64-bit on most/all modern platforms.
Therefore, usage of this macro creates a Year 2038 bug.
when we open a file that we don't expect to be a symlink use
O_NOFOLLOW to prevent a race condition where an attacker could change
a file between being a normal file and a symlink
- Put sum2_array into sum_struct to hold an array of sum2 checksums
that are each xfer_sum_len bytes.
- Remove sum2 buf from sum_buf.
- Add macro sum2_at() to access each sum2 array element.
- Throw an error if a sums header has an s2length larger than
xfer_sum_len.
Clang rightfully complains about invoking bomb(..) without a proper prototype:
lib/pool_alloc.c:171:16: warning: passing arguments to a function without a prototype
is deprecated in all versions of C and is not supported in C2x [-Wdeprecated-non-prototype]
(*pool->bomb)(bomb_msg, __FILE__, __LINE__);
^
1 warning generated.
Signed-off-by: Holger Hoffstätte <holger@applied-asynchrony.com>
Replace unsafe generic function pointer cast with proper type cast for
qsort() comparison function. This fixes a potential type mismatch
warning without changing the behavior.
Signed-off-by: Charalampos Mitrodimas <charmitro@posteo.net>
Clang rightfully complains about conflicting prototypes, as both lseek() variants
are redefined:
syscall.c:394:10: warning: a function declaration without a prototype is deprecated
in all versions of C and is treated as a zero-parameter prototype in C2x, conflicting
with a previous declaration [-Wdeprecated-non-prototype]
off64_t lseek64();
^
/usr/include/unistd.h:350:18: note: conflicting prototype is here
extern __off64_t lseek64 (int __fd, __off64_t __offset, int __whence)
^
1 warning generated.
The point of the #ifdef is to build for the configured OFF_T; there is
no reason to redefine lseek/lseek64, which should have been found
via configure.
Signed-off-by: Holger Hoffstätte <holger@applied-asynchrony.com>
The exclude.test file continues to run local copies (which are a special
kind of "push") while the exclude-lsh.test symlink runs a a "pull" using
the lsh.sh script as the "remote" shell.
