diff options
authorHannes Frederic Sowa <hannes@stressinduktion.org>2013-08-16 13:02:27 +0200
committerDavid S. Miller <davem@davemloft.net>2013-08-20 00:11:24 -0700
commit4b08a8f1bd8cb4541c93ec170027b4d0782dab52 (patch)
parentfd3930f70c8d14008f3377d51ce039806dfc542e (diff)
ipv6: remove max_addresses check from ipv6_create_tempaddr
Because of the max_addresses check attackers were able to disable privacy extensions on an interface by creating enough autoconfigured addresses: <http://seclists.org/oss-sec/2012/q4/292> But the check is not actually needed: max_addresses protects the kernel to install too many ipv6 addresses on an interface and guards addrconf_prefix_rcv to install further addresses as soon as this limit is reached. We only generate temporary addresses in direct response of a new address showing up. As soon as we filled up the maximum number of addresses of an interface, we stop installing more addresses and thus also stop generating more temp addresses. Even if the attacker tries to generate a lot of temporary addresses by announcing a prefix and removing it again (lifetime == 0) we won't install more temp addresses, because the temporary addresses do count to the maximum number of addresses, thus we would stop installing new autoconfigured addresses when the limit is reached. This patch fixes CVE-2013-0343 (but other layer-2 attacks are still possible). Thanks to Ding Tianhong to bring this topic up again. Cc: Ding Tianhong <dingtianhong@huawei.com> Cc: George Kargiotakis <kargig@void.gr> Cc: P J P <ppandit@redhat.com> Cc: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org> Signed-off-by: Hannes Frederic Sowa <hannes@stressinduktion.org> Acked-by: Ding Tianhong <dingtianhong@huawei.com> Signed-off-by: David S. Miller <davem@davemloft.net>
1 files changed, 4 insertions, 6 deletions
diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index da4241c8c7da..498ea99194af 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -1126,12 +1126,10 @@ retry:
if (ifp->flags & IFA_F_OPTIMISTIC)
addr_flags |= IFA_F_OPTIMISTIC;
- ift = !max_addresses ||
- ipv6_count_addresses(idev) < max_addresses ?
- ipv6_add_addr(idev, &addr, NULL, tmp_plen,
- ipv6_addr_scope(&addr), addr_flags,
- tmp_valid_lft, tmp_prefered_lft) : NULL;
- if (IS_ERR_OR_NULL(ift)) {
+ ift = ipv6_add_addr(idev, &addr, NULL, tmp_plen,
+ ipv6_addr_scope(&addr), addr_flags,
+ tmp_valid_lft, tmp_prefered_lft);
+ if (IS_ERR(ift)) {
pr_info("%s: retry temporary address regeneration\n", __func__);