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| 1 | +From a4406c7f2e4c522855e5710d55b8778fbcbc2b48 Mon Sep 17 00:00:00 2001 |
| 2 | +From: Evgeny Vereshchagin <evvers@ya.ru> |
| 3 | +Date: Wed, 17 Dec 2025 08:11:23 +0000 |
| 4 | +Subject: [PATCH] core: refuse to create wide-area record browsers when |
| 5 | + wide-area is off |
| 6 | + |
| 7 | +It fixes a bug where it was possible for unprivileged local users to |
| 8 | +crash avahi-daemon (with wide-area disabled) by creating record browsers |
| 9 | +with the AVAHI_LOOKUP_USE_WIDE_AREA flag set via D-Bus (either by calling |
| 10 | +the RecordBrowserNew method directly or by creating hostname/address/service |
| 11 | +resolvers/browsers that create those browsers internally themselves). |
| 12 | + |
| 13 | +``` |
| 14 | +$ gdbus call --system --dest org.freedesktop.Avahi --object-path / --method org.freedesktop.Avahi.Server.ResolveHostName -- -1 -1 yo.local -1 1 |
| 15 | +Error: GDBus.Error:org.freedesktop.DBus.Error.NoReply: Message recipient disconnected from message bus without replying |
| 16 | +``` |
| 17 | +``` |
| 18 | +dbus-protocol.c: interface=org.freedesktop.Avahi.Server, path=/, member=ResolveHostName |
| 19 | +avahi-daemon: wide-area.c:725: avahi_wide_area_scan_cache: Assertion `e' failed. |
| 20 | +==307948== |
| 21 | +==307948== Process terminating with default action of signal 6 (SIGABRT) |
| 22 | +==307948== at 0x4B3630C: __pthread_kill_implementation (pthread_kill.c:44) |
| 23 | +==307948== by 0x4ADF921: raise (raise.c:26) |
| 24 | +==307948== by 0x4AC74AB: abort (abort.c:77) |
| 25 | +==307948== by 0x4AC741F: __assert_fail_base.cold (assert.c:118) |
| 26 | +==307948== by 0x48D8B85: avahi_wide_area_scan_cache (wide-area.c:725) |
| 27 | +==307948== by 0x48C8953: lookup_scan_cache (browse.c:351) |
| 28 | +==307948== by 0x48C8B1B: lookup_go (browse.c:386) |
| 29 | +==307948== by 0x48C9148: defer_callback (browse.c:516) |
| 30 | +==307948== by 0x48AEA0E: expiration_event (timeeventq.c:94) |
| 31 | +==307948== by 0x489D3AE: timeout_callback (simple-watch.c:447) |
| 32 | +==307948== by 0x489D787: avahi_simple_poll_dispatch (simple-watch.c:563) |
| 33 | +==307948== by 0x489D91E: avahi_simple_poll_iterate (simple-watch.c:605) |
| 34 | +==307948== |
| 35 | +``` |
| 36 | + |
| 37 | +wide-area has been disabled by default since |
| 38 | +9c4214146738146e454f098264690e8e884c39bd (v0.9-rc2). |
| 39 | + |
| 40 | +https: //github.com/avahi/avahi/security/advisories/GHSA-mhf3-865v-g5rc |
| 41 | +Signed-off-by: Azure Linux Security Servicing Account <azurelinux-security@microsoft.com> |
| 42 | +Upstream-reference: https://github.com/avahi/avahi/commit/0c013e2e819be3bda74cecf48b5f64956cf8a760.patch |
| 43 | +--- |
| 44 | + avahi-core/browse.c | 5 +++++ |
| 45 | + 1 file changed, 5 insertions(+) |
| 46 | + |
| 47 | +diff --git a/avahi-core/browse.c b/avahi-core/browse.c |
| 48 | +index 0afeba7..d7d541b 100644 |
| 49 | +--- a/avahi-core/browse.c |
| 50 | ++++ b/avahi-core/browse.c |
| 51 | +@@ -583,6 +583,11 @@ AvahiSRecordBrowser *avahi_s_record_browser_prepare( |
| 52 | + AVAHI_CHECK_VALIDITY_RETURN_NULL(server, AVAHI_FLAGS_VALID(flags, AVAHI_LOOKUP_USE_WIDE_AREA|AVAHI_LOOKUP_USE_MULTICAST), AVAHI_ERR_INVALID_FLAGS); |
| 53 | + AVAHI_CHECK_VALIDITY_RETURN_NULL(server, !(flags & AVAHI_LOOKUP_USE_WIDE_AREA) || !(flags & AVAHI_LOOKUP_USE_MULTICAST), AVAHI_ERR_INVALID_FLAGS); |
| 54 | + |
| 55 | ++ if ((flags & AVAHI_LOOKUP_USE_WIDE_AREA) && !server->wide_area_lookup_engine) { |
| 56 | ++ avahi_server_set_errno(server, AVAHI_ERR_NOT_SUPPORTED); |
| 57 | ++ return NULL; |
| 58 | ++ } |
| 59 | ++ |
| 60 | + if (!(b = avahi_new(AvahiSRecordBrowser, 1))) { |
| 61 | + avahi_server_set_errno(server, AVAHI_ERR_NO_MEMORY); |
| 62 | + return NULL; |
| 63 | +-- |
| 64 | +2.45.4 |
| 65 | + |
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