Upstream-Status: Backport [https://github.com/lathiat/avahi/commit/e111def] CVE: CVE-2017-6519 Signed-off-by: Kai Kang From e111def44a7df4624a4aa3f85fe98054bffb6b4f Mon Sep 17 00:00:00 2001 From: Trent Lloyd Date: Sat, 22 Dec 2018 09:06:07 +0800 Subject: [PATCH] Drop legacy unicast queries from address not on local link When handling legacy unicast queries, ensure that the source IP is inside a subnet on the local link, otherwise drop the packet. Fixes #145 Fixes #203 CVE-2017-6519 CVE-2018-1000845 --- avahi-core/server.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/avahi-core/server.c b/avahi-core/server.c index a2cb19a8..a2580e38 100644 --- a/avahi-core/server.c +++ b/avahi-core/server.c @@ -930,6 +930,7 @@ static void dispatch_packet(AvahiServer *s, AvahiDnsPacket *p, const AvahiAddres if (avahi_dns_packet_is_query(p)) { int legacy_unicast = 0; + char t[AVAHI_ADDRESS_STR_MAX]; /* For queries EDNS0 might allow ARCOUNT != 0. We ignore the * AR section completely here, so far. Until the day we add @@ -947,6 +948,13 @@ static void dispatch_packet(AvahiServer *s, AvahiDnsPacket *p, const AvahiAddres legacy_unicast = 1; } + if (!is_mdns_mcast_address(dst_address) && + !avahi_interface_address_on_link(i, src_address)) { + + avahi_log_debug("Received non-local unicast query from host %s on interface '%s.%i'.", avahi_address_snprint(t, sizeof(t), src_address), i->hardware->name, i->protocol); + return; + } + if (legacy_unicast) reflect_legacy_unicast_query_packet(s, p, i, src_address, port);