61 lines
2.4 KiB
Diff
61 lines
2.4 KiB
Diff
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From 4b08a8f1bd8cb4541c93ec170027b4d0782dab52 Mon Sep 17 00:00:00 2001
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From: Hannes Frederic Sowa <hannes@stressinduktion.org>
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Date: Fri, 16 Aug 2013 11:02:27 +0000
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Subject: ipv6: remove max_addresses check from ipv6_create_tempaddr
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Because of the max_addresses check attackers were able to disable privacy
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extensions on an interface by creating enough autoconfigured addresses:
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<http://seclists.org/oss-sec/2012/q4/292>
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But the check is not actually needed: max_addresses protects the
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kernel to install too many ipv6 addresses on an interface and guards
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addrconf_prefix_rcv to install further addresses as soon as this limit
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is reached. We only generate temporary addresses in direct response of
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a new address showing up. As soon as we filled up the maximum number of
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addresses of an interface, we stop installing more addresses and thus
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also stop generating more temp addresses.
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Even if the attacker tries to generate a lot of temporary addresses
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by announcing a prefix and removing it again (lifetime == 0) we won't
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install more temp addresses, because the temporary addresses do count
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to the maximum number of addresses, thus we would stop installing new
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autoconfigured addresses when the limit is reached.
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This patch fixes CVE-2013-0343 (but other layer-2 attacks are still
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possible).
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Thanks to Ding Tianhong to bring this topic up again.
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Cc: Ding Tianhong <dingtianhong@huawei.com>
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Cc: George Kargiotakis <kargig@void.gr>
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Cc: P J P <ppandit@redhat.com>
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Cc: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
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Signed-off-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
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Acked-by: Ding Tianhong <dingtianhong@huawei.com>
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Signed-off-by: David S. Miller <davem@davemloft.net>
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---
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diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
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index da4241c..498ea99 100644
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--- a/net/ipv6/addrconf.c
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+++ b/net/ipv6/addrconf.c
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@@ -1126,12 +1126,10 @@ retry:
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if (ifp->flags & IFA_F_OPTIMISTIC)
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addr_flags |= IFA_F_OPTIMISTIC;
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- ift = !max_addresses ||
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- ipv6_count_addresses(idev) < max_addresses ?
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- ipv6_add_addr(idev, &addr, NULL, tmp_plen,
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- ipv6_addr_scope(&addr), addr_flags,
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- tmp_valid_lft, tmp_prefered_lft) : NULL;
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- if (IS_ERR_OR_NULL(ift)) {
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+ ift = ipv6_add_addr(idev, &addr, NULL, tmp_plen,
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+ ipv6_addr_scope(&addr), addr_flags,
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+ tmp_valid_lft, tmp_prefered_lft);
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+ if (IS_ERR(ift)) {
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in6_ifa_put(ifp);
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in6_dev_put(idev);
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pr_info("%s: retry temporary address regeneration\n", __func__);
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--
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cgit v0.9.2
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