package/avahi: add upstream security fix

Fixes CVE-2017-6519: avahi-daemon in Avahi through 0.6.32 and 0.7
inadvertently responds to IPv6 unicast queries with source addresses
that are not on-link, which allows remote attackers to cause a denial
of service (traffic amplification) and may cause information leakage
by obtaining potentially sensitive information from the responding
device via port-5353 UDP packets.

Signed-off-by: Artem Panfilov <panfilov.artyom@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
(cherry picked from commit 1e17adf1c5)
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/avahi/0001-Drop-legacy-unicast-queries-from-address-not-on-loca.patch

@@ -0,0 +1,48 @@
+From e111def44a7df4624a4aa3f85fe98054bffb6b4f Mon Sep 17 00:00:00 2001
+From: Trent Lloyd <trent@lloyd.id.au>
+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-2018-100084
+
+Backported from: e111def44a7df4624a4aa3f85fe98054bffb6b4f
+Signed-off-by: Artem Panfilov <panfilov.artyom@gmail.com>
+---
+ 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);
+ 
+-- 
+2.19.1
+