ipv6: drop non loopback packets claiming to originate from ::1

We lack a saddr check for ::1. This causes security issues e.g. with acls
permitting connections from ::1 because of assumption that these originate
from local machine.

Assuming a source address of ::1 is local seems reasonable.
RFC4291 doesn't allow such a source address either, so drop such packets.

Reported-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Florian Westphal <fw@strlen.de>
Acked-by: Eric Dumazet <edumazet@google.com>
Acked-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv6/ip6_input.c b/net/ipv6/ip6_input.c
index aacfb4b..c45b12b 100644 (file)
--- a/net/ipv6/ip6_input.c
+++ b/net/ipv6/ip6_input.c
@@ -122,11 +122,14 @@ int ipv6_rcv(struct sk_buff *skb, struct net_device *dev, struct packet_type *pt
                        max_t(unsigned short, 1, skb_shinfo(skb)->gso_segs));
        /*
         * RFC4291 2.5.3
+        * The loopback address must not be used as the source address in IPv6
+        * packets that are sent outside of a single node. [..]
         * A packet received on an interface with a destination address
         * of loopback must be dropped.
         */
-       if (!(dev->flags & IFF_LOOPBACK) &&
-           ipv6_addr_loopback(&hdr->daddr))
+       if ((ipv6_addr_loopback(&hdr->saddr) ||
+            ipv6_addr_loopback(&hdr->daddr)) &&
+            !(dev->flags & IFF_LOOPBACK))
                goto err;
 
        /* RFC4291 Errata ID: 3480