Three receiver security fixes from the audit:
1. --temp-dir symlink escape (High): file_open_temp_dir() opened the
client-controlled scratch dir with a bare open(), so a symlink planted
under the receive root let a peer redirect receiver scratch files
outside the authorized root. The opened dir is now judged by the REAL
path of its fd (via /proc/self/fd), and any target outside the
authorized receive root is refused with a logged error (EACCES). An
in-root symlink (the EXDEV cross-filesystem fallback case) still works,
and the no-root local batch path is unchanged.
2. setuid/setgid/sticky under SUPER_MODE_OFF (High): the special bits were
applied under --perms (and via --chmod) even when the connection forbade
super-user activities. FileAttrPolicy gains super_permitted, set by
file_attr_policy_from_config() from privilege_super_mode_permitted();
metadata_mode_for_policy(), the symlink path, the special-node creation
path, and the deferred directory-mode apply now strip the special bits
when it is false. Exact rsync semantics are preserved when permitted.
3. daemon umask (Low): daemonize() forced umask(0), so implied parent
directories created without -p were world-writable 0777. Set the
conventional daemon umask 022 instead (rsync never forces 0); -p/-a mode
preservation is unaffected because it restores modes via fchmod.
Tests: new unit tests for file_open_temp_dir confinement and the
masked/unmasked special-bit policy (incl. the --chmod path), a daemon
world-writable-dir regression test, an integration escape test, and a
root-only integration test asserting special bits are masked without
--allow-super. The old cross-filesystem test encoded the vulnerable
behavior (symlink target outside the root) and is replaced by the escape
test; the EXDEV fallback code is retained for in-root links.
Extend _snapshot_tree to record mode, inode, xattrs, directories and
special nodes, and add coverage proving a server-contacting --dry-run
leaves the destination structurally identical for --delay-updates,
--backup, symlinks, hardlinks, FIFOs, and daemon modules (including a
read-only module). Add a regression test for the --read-batch --dry-run
refusal and for a missing/non-directory receive root failing a dry-run
exactly like a real run.
Fix stale version comments (2.20.0/633 -> 2.21.0/637) and RSYNC_COMPAT's
current --protocol value, and add a unit assertion that
--server-port/--port (and --server-host) set the dry-run routing bit.
Every client on loopback shares the 127.0.0.1 identity, so counting them
against 'max connections per host' or the default-on auth lockout lets one
local client deny service to all the others (and makes a shared-NAT/proxy
address a natural DoS vector for remote clients). Use
utils_fd_peer_is_local (fail-closed) in the daemon gate to exempt a
provably local peer from the per-source cap and the auth lockout while
keeping the per-module and global caps. Remote peers are unchanged.
Document the shared-NAT/proxy identity limitation and the loopback
exemption in README/RSYNC_COMPAT/CHANGELOG, update the integration test to
assert the exemption, and fix the README 'auth failure delay' cap (5000,
not 60000).
Wire the shared registry into the accept loop (parent claims a slot before
fork, blocks SIGCHLD across fork+pid publication, and reclaims the dead
child's slot from the SIGCHLD handler so per-module/per-source counts are
released even on SIGKILL). The connection child records the selected module
and normalized peer IP once the config frame names them: an over-cap module
or source is refused at the config gate with an audit log, and a source
that exceeded the auth-failure threshold is refused before a SCRAM
challenge (the counter is shared across children and cleared on success).
The existing global cap and host ACLs are untouched.
- server gate: the --allow-unauthenticated loopback allowance now requires
an actual plaintext connection (!gate_ctx->ssl), so a loopback TLS client
whose cert fails the --client-cn check is refused before any SCRAM
challenge instead of falling through the plaintext opt-in. Keep the
invalid-fd guard as belt-and-braces (unreachable after the policy check).
- test: rewrote test_wrong_client_cn_refused_before_auth_challenge to run
deterministically over 127.0.0.1 with --tls + --allow-unauthenticated and
a CA-valid wrong-CN client cert, asserting the gate refusal log and an
unchanged module tree (no skip).
- docs: --client-cn is mandatory with --tls; dummykey sidecar is secret
material; document all transient-fallback reasons; qualify
--allow-unauthenticated in README and --help so it cannot read as
permitting remote plaintext auth.
- credentials.h: drop stale restrictive-umask claim (fchmod forces exact
0600; only create/write/fsync/link/fchmod failure degrades to ephemeral).
utils_fd_peer_is_local now returns true only when getpeername SUCCEEDS and the
peer address classifies as loopback. A non-socket descriptor (pipe/socketpair)
or any getpeername error is NOT local, so the daemon auth gate fails closed
instead of treating an untestable --stdio pipe as trusted (daemon auth modules
are --daemon-only and the stdio path never loads a daemon config).
server_module_gate now requires --allow-unauthenticated for the loopback
plaintext auth path: a plaintext loopback connection without the operator
opt-in is refused at the config gate BEFORE server_auth_handshake, so no SCRAM
challenge is sent. Remote peers still require verified TLS regardless of the
flag; the handler keeps its defense-in-depth checks.
Docs state the exact policy (verified TLS with matching --client-cn, or
operator-opted-in loopback plaintext), drop the SSH/stdio auth-transport claim
(they are daemon-only), and add the loopback trust-boundary relay caveat and
the CN-only (no SAN) residual. Adds a unit-test negative for pipe/socketpair
and an integration test where a relay observes no challenge when the flag is
absent.
Daemon modules that declare 'auth users' no longer accept credentials over a
remote plaintext connection: server_module_gate refuses at the config gate,
before any SCRAM challenge is sent, unless the connection is verified TLS with
a client certificate matching --client-cn, or a local/SSH transport (loopback
TCP peer or the --stdio pipe). --allow-unauthenticated does not relax this.
The TLS client-CN comparison now uses credentials_secure_equal (S2). Clients
sending --password-file to a non-loopback daemon must use --tls; validate_config
rejects the plaintext case before any network I/O.
Adds utils_sockaddr_is_loopback / utils_fd_peer_is_local / utils_host_is_loopback
helpers with unit tests, a client validation unit test, and integration tests
for the client-side plaintext rejection and the wrong-CN gate refusal.
- file: open -K dirlink referents via a race-safe relative O_NOFOLLOW walk
from the authorized-root fd instead of re-opening an absolute realpath()
result (removes the intermediate-symlink swap TOCTOU).
- transport_ssh: always single-quote the server path, including --old-args,
so no mode can inject shell metacharacters.
- transport_tls: set SSL_OP_NO_COMPRESSION and (guarded) SSL_OP_NO_RENEGOTIATION.
- credentials: reject --password-file/--early-input with any group/other
permission bit; chmod 0600 the affected test fixtures.
- file_store: export file_store_write_sparse() and remove the verbatim
file.c duplicate.
- file_ensure_directory_secure() now chowns a final directory it creates under
--copy-as and fails on error; the symlink parent-creation call site propagates
it. The is_dir branch fails when the confined parent cannot be opened under
--copy-as. Closes the residual wrong-owner gap for synthesized/symlink
parent directories.
- file_restore_symlink_metadata() early NULL return is copy-as-aware.
- Preserve errno across the implicit-parent failure cleanup.
- Neutral skip messages (the clamp, not --no-super, may be responsible).
- Daemon copy-as test tolerates the non-root privilege refusal; usage text lists
--copy-as.
- H3: a daemon module without 'client owner = yes' now also has super-user
device activity forced off (char/block mknod, --write-devices), so a root
daemon can no longer be made to create/write raw devices under AUTO. The
entries are skipped, preserving ordinary -a pushes.
- H1/H2: propagate a failed required --copy-as chown from symlink metadata
restore and implicitly-created parent directories, so the entry (and run)
reports failure instead of a wrong-owner success.
- Docs/help/headers updated for A2/A3 and the device clamp; startup warning
spells out the client-owner risk.
- Tests: daemon device clamp (skipped without opt-in, created with opt-in),
updated --super/--fake-super expectations.
A1: daemon refuses every client-chosen ownership/super-user request
(--numeric-ids/--chown/--usermap/--groupmap/--fake-super/--copy-as/--super)
unless the selected module opts in with 'client owner = yes'.
A2: fake-super owner replay requires an explicit ownership identity policy.
A3: --super no longer implies --numeric-ids (ownership stays opt-in).
A5: a failed --copy-as chown marks the entry failed instead of reporting
success with the wrong owner.
- test_credentials.c: NUL-terminate the overlong-line stack buffer before
make_tmp_file's strlen() (was a stack-buffer-overflow READ under ASan);
still exercises the overlong-rejection path.
- Add redacted protocol string variants (protocol_send_str_redacted /
receive + fd send_str_redacted/receive_str_redacted) and use them for the
daemon auth username/digest so --verbose / LOG_DEBUG_ALL never logs a
replayable credential while other protocol strings keep their debug trace.
- credentials_verify/gate: replace byte-wise-short-circuiting strcmp with a
fixed-length constant-time username compare (closes user-enumeration oracle);
update doc comment to match.
- read_secret_file: preserve password exact bytes (only strip trailing CR/LF)
and burn the stack line buffer; document the whitespace behavior.
- test_server_cli.c: note the parser zero-inits opts on failure.
- Add debug-level daemon test asserting the digest never appears under --verbose.
PROTOCOL_VERSION stays 2.15.0.
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