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From e111def44a7df4624a4aa3f85fe98054bffb6b4f Mon Sep 17 00:00:00 2001
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From: Trent Lloyd <trent@lloyd.id.au>
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Date: Sat, 22 Dec 2018 09:06:07 +0800
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Subject: [PATCH] Drop legacy unicast queries from address not on local link
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When handling legacy unicast queries, ensure that the source IP is
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inside a subnet on the local link, otherwise drop the packet.
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Fixes #145
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Fixes #203
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CVE-2017-6519
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CVE-2018-100084
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---
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avahi-core/server.c | 8 ++++++++
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1 file changed, 8 insertions(+)
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diff --git a/avahi-core/server.c b/avahi-core/server.c
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index a2cb19a8..a2580e38 100644
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--- a/avahi-core/server.c
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+++ b/avahi-core/server.c
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@@ -930,6 +930,7 @@ static void dispatch_packet(AvahiServer *s, AvahiDnsPacket *p, const AvahiAddres
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if (avahi_dns_packet_is_query(p)) {
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int legacy_unicast = 0;
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+ char t[AVAHI_ADDRESS_STR_MAX];
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/* For queries EDNS0 might allow ARCOUNT != 0. We ignore the
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* AR section completely here, so far. Until the day we add
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@@ -947,6 +948,13 @@ static void dispatch_packet(AvahiServer *s, AvahiDnsPacket *p, const AvahiAddres
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legacy_unicast = 1;
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}
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+ if (!is_mdns_mcast_address(dst_address) &&
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+ !avahi_interface_address_on_link(i, src_address)) {
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+
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+ 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);
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+ return;
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+ }
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+
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if (legacy_unicast)
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reflect_legacy_unicast_query_packet(s, p, i, src_address, port);
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