From: Ashishkumar Parmar <[email protected]> Pick the upstream backport [1] for CVE-2026-43617 as mentioned in [2], where hostname-based daemon ACLs could be bypassed when reverse DNS was performed after daemon chroot.
[1] https://github.com/RsyncProject/rsync/commit/74ea276900779b95ddd1769d1d6ae78b2fd1a790 [2] https://www.cve.org/CVERecord?id=CVE-2026-43617 Signed-off-by: Ashishkumar Parmar <[email protected]> --- .../rsync/files/CVE-2026-43617.patch | 197 ++++++++++++++++++ meta/recipes-devtools/rsync/rsync_3.2.7.bb | 1 + 2 files changed, 198 insertions(+) create mode 100644 meta/recipes-devtools/rsync/files/CVE-2026-43617.patch diff --git a/meta/recipes-devtools/rsync/files/CVE-2026-43617.patch b/meta/recipes-devtools/rsync/files/CVE-2026-43617.patch new file mode 100644 index 0000000000..409e524ea8 --- /dev/null +++ b/meta/recipes-devtools/rsync/files/CVE-2026-43617.patch @@ -0,0 +1,197 @@ +From d1b1f430b3c0ee8f7fd8ffb10ac864689a3ed024 Mon Sep 17 00:00:00 2001 +From: Andrew Tridgell <[email protected]> +Date: Wed, 31 Dec 2025 13:50:35 +1100 +Subject: [PATCH] clientserver: fix hostname ACL bypass when using daemon + chroot + +On an rsync daemon configured with "daemon chroot", the reverse-DNS +lookup of the connecting client was performed *after* the chroot +had been entered. If the chroot did not contain the files glibc +needs for resolution (/etc/resolv.conf, /etc/nsswitch.conf, +/etc/hosts, NSS service modules), the lookup failed and +client_name() returned "UNKNOWN". Hostname-based deny rules +("hosts deny = *.evil.example") therefore could not match, and +an attacker controlling their PTR record could connect from a +hostname the administrator had intended to deny. IP-based ACLs +were unaffected. + +Do the reverse DNS lookup before chroot/setuid; client_name() +caches its result, so the post-chroot call uses the cached value +and hostname-based ACLs work even when DNS is unavailable +post-chroot. + +Adds testsuite/daemon-chroot-acl.test as end-to-end regression +coverage. The test sets up an empty chroot directory, configures +"hosts deny = <localhost-resolved-name>" with daemon chroot, and +asserts the connection is refused with @ERROR access denied. +Uses unshare --user --map-root-user for non-root CAP_SYS_CHROOT; +skips cleanly on non-Linux or when user namespaces aren't +available. + +Reporter: Joshua Rogers (MegaManSec). + +Co-Authored-By: Claude Opus 4.7 (1M context) <[email protected]> + +CVE: CVE-2026-43617 +Upstream-Status: Backport [https://github.com/RsyncProject/rsync/commit/74ea276900779b95ddd1769d1d6ae78b2fd1a790] + +(cherry picked from commit 74ea276900779b95ddd1769d1d6ae78b2fd1a790) +Signed-off-by: Ashishkumar Parmar <[email protected]> +--- + clientserver.c | 22 ++++++ + testsuite/daemon-chroot-acl.test | 111 +++++++++++++++++++++++++++++++ + 2 files changed, 133 insertions(+) + create mode 100644 testsuite/daemon-chroot-acl.test + +diff --git a/clientserver.c b/clientserver.c +index b6eba098..3333aa96 100644 +--- a/clientserver.c ++++ b/clientserver.c +@@ -1310,6 +1310,28 @@ int start_daemon(int f_in, int f_out) + if (lp_proxy_protocol() && !read_proxy_protocol_header(f_in)) + return -1; + ++ /* Do reverse DNS lookup before chroot/setuid. The result is cached, ++ * so the later client_name() call will use this cached value. This ++ * ensures hostname-based ACLs work even when DNS is unavailable ++ * after chroot. ++ * ++ * "reverse lookup" can be set globally OR per-module, so we also ++ * scan each module: a deployment with "reverse lookup = no" in the ++ * global section but "reverse lookup = yes" in a specific module ++ * still triggers a post-chroot lookup at access-check time ++ * (rsync_module() in this file), which would also fail in the ++ * chroot and turn hostname-based deny rules into silent bypasses. */ ++ { ++ int need_reverse = lp_reverse_lookup(-1); ++ int j, num_modules = lp_num_modules(); ++ for (j = 0; !need_reverse && j < num_modules; j++) { ++ if (lp_reverse_lookup(j)) ++ need_reverse = 1; ++ } ++ if (need_reverse) ++ (void)client_name(client_addr(f_in)); ++ } ++ + p = lp_daemon_chroot(); + if (*p) { + log_init(0); /* Make use we've initialized syslog before chrooting. */ +diff --git a/testsuite/daemon-chroot-acl.test b/testsuite/daemon-chroot-acl.test +new file mode 100644 +index 00000000..9d1c1b63 +--- /dev/null ++++ b/testsuite/daemon-chroot-acl.test +@@ -0,0 +1,111 @@ ++#!/bin/sh ++ ++# Copyright (C) 2026 by Andrew Tridgell ++ ++# This program is distributable under the terms of the GNU GPL (see ++# COPYING). ++ ++# Regression test for GHSA-rjfm-3w2m-jf4f: a hostname-based "hosts deny" ++# rule must still match when the daemon performs a 'daemon chroot' and ++# the chroot does not contain the NSS files glibc needs for reverse DNS. ++# ++# Pre-fix, reverse DNS happened *after* the daemon chroot. With an empty ++# chroot the NSS lookup failed, client_name() returned "UNKNOWN", and a ++# deny rule referring to the connecting hostname silently failed to ++# match. ++# ++# Two scenarios are exercised so we can distinguish the case the fix ++# definitely covers from the per-module path that may still be ++# vulnerable: ++# A. global "reverse lookup = yes" (covered by b6abdb4c) ++# B. only module "reverse lookup = yes" (gap to verify) ++ ++. "$suitedir/rsync.fns" ++ ++case `uname -s` in ++Linux*) ;; ++*) test_skipped "test is Linux-specific (uses chroot+unshare)" ;; ++esac ++ ++# We need CAP_SYS_CHROOT. Re-exec under a user namespace if not root. ++if ! chroot / /bin/true 2>/dev/null; then ++ if [ -z "$RSYNC_UNSHARED" ] && unshare --user --map-root-user true 2>/dev/null; then ++ echo "Re-running under unshare --user --map-root-user..." ++ RSYNC_UNSHARED=1 exec unshare --user --map-root-user "$SHELL_PATH" $RUNSHFLAGS "$0" ++ fi ++ test_skipped "need CAP_SYS_CHROOT (root or unshare --user --map-root-user)" ++fi ++ ++# We need 127.0.0.1 to reverse-resolve to a real hostname while NSS is ++# still working (i.e. before the daemon's chroot). The daemon will ++# look that name up itself as part of its hostname-based ACL check; ++# we then deny that name and assert the connection is rejected. ++client_hostname=`getent hosts 127.0.0.1 2>/dev/null | awk 'NR==1 {print $2}'` ++if [ -z "$client_hostname" ] || [ "$client_hostname" = "127.0.0.1" ]; then ++ test_skipped "no reverse DNS for 127.0.0.1" ++fi ++ ++chrootdir="$scratchdir/chroot" ++rm -rf "$chrootdir" ++mkdir -p "$chrootdir/modroot" ++echo "from chroot" > "$chrootdir/modroot/file1" ++ ++conf="$scratchdir/test-rsyncd.conf" ++logfile="$scratchdir/rsyncd.log" ++ ++write_conf() { ++ cat >"$conf" <<EOF ++use chroot = no ++log file = $logfile ++daemon chroot = $chrootdir ++reverse lookup = $1 ++hosts deny = $client_hostname ++max verbosity = 4 ++ ++[chrootmod] ++ path = /modroot ++ read only = yes ++ reverse lookup = $2 ++EOF ++} ++ ++# Run a transfer and return 0 if the daemon refused with @ERROR access ++# denied (the expected outcome when the deny rule matches). ++run_check() { ++ label="$1" ++ ++ rm -f "$logfile" ++ rm -rf "$todir" ++ mkdir -p "$todir" ++ ++ out="$scratchdir/run.out" ++ ++ RSYNC_CONNECT_PROG="$RSYNC --config=$conf --daemon" \ ++ $RSYNC -av localhost::chrootmod/ "$todir/" >"$out" 2>&1 ++ rc=$? ++ ++ echo "----- $label (rsync exit $rc):" ++ cat "$out" ++ echo "----- daemon log:" ++ [ -f "$logfile" ] && cat "$logfile" ++ echo "-----" ++ ++ grep -q '@ERROR.*access denied' "$out" ++} ++ ++# Scenario A: global reverse lookup. Covered by b6abdb4c. ++write_conf yes yes ++if ! run_check "Scenario A (global reverse lookup = yes)"; then ++ test_fail "Scenario A: hostname deny rule was bypassed" ++fi ++ ++# Scenario B: only the per-module reverse-lookup setting is enabled. ++# The b6abdb4c fix only pre-warms client_name()'s cache when the ++# global setting is on, so the post-chroot lookup in this path may ++# still produce "UNKNOWN" and bypass the deny rule. ++write_conf no yes ++if ! run_check "Scenario B (per-module reverse lookup only)"; then ++ test_fail "Scenario B: hostname deny rule was bypassed (per-module reverse lookup with daemon chroot still has the bypass)" ++fi ++ ++exit 0 +-- +2.35.6 diff --git a/meta/recipes-devtools/rsync/rsync_3.2.7.bb b/meta/recipes-devtools/rsync/rsync_3.2.7.bb index b1483fc6a6..a27fb0f291 100644 --- a/meta/recipes-devtools/rsync/rsync_3.2.7.bb +++ b/meta/recipes-devtools/rsync/rsync_3.2.7.bb @@ -40,6 +40,7 @@ SRC_URI = "https://download.samba.org/pub/${BPN}/src/${BP}.tar.gz \ file://CVE-2026-43619_p4.patch \ file://CVE-2026-43618.patch \ file://CVE-2026-43620.patch \ + file://CVE-2026-43617.patch \ " SRC_URI[sha256sum] = "4e7d9d3f6ed10878c58c5fb724a67dacf4b6aac7340b13e488fb2dc41346f2bb" -- 2.44.1
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