From 4b08a8f1bd8cb4541c93ec170027b4d0782dab52 Mon Sep 17 00:00:00 2001 From: Hannes Frederic Sowa Date: Fri, 16 Aug 2013 13:02:27 +0200 Subject: 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: 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 Cc: George Kargiotakis Cc: P J P Cc: YOSHIFUJI Hideaki Signed-off-by: Hannes Frederic Sowa Acked-by: Ding Tianhong Signed-off-by: David S. Miller --- net/ipv6/addrconf.c | 10 ++++------ 1 file changed, 4 insertions(+), 6 deletions(-) (limited to 'net/ipv6') 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)) { in6_ifa_put(ifp); in6_dev_put(idev); pr_info("%s: retry temporary address regeneration\n", __func__); -- cgit From f46078cfcd77fa5165bf849f5e568a7ac5fa569c Mon Sep 17 00:00:00 2001 From: Hannes Frederic Sowa Date: Fri, 16 Aug 2013 13:30:07 +0200 Subject: ipv6: drop packets with multiple fragmentation headers It is not allowed for an ipv6 packet to contain multiple fragmentation headers. So discard packets which were already reassembled by fragmentation logic and send back a parameter problem icmp. The updates for RFC 6980 will come in later, I have to do a bit more research here. Cc: YOSHIFUJI Hideaki Signed-off-by: Hannes Frederic Sowa Signed-off-by: David S. Miller --- net/ipv6/reassembly.c | 5 +++++ 1 file changed, 5 insertions(+) (limited to 'net/ipv6') diff --git a/net/ipv6/reassembly.c b/net/ipv6/reassembly.c index 790d9f4b8b0b..1aeb473b2cc6 100644 --- a/net/ipv6/reassembly.c +++ b/net/ipv6/reassembly.c @@ -490,6 +490,7 @@ static int ip6_frag_reasm(struct frag_queue *fq, struct sk_buff *prev, ipv6_hdr(head)->payload_len = htons(payload_len); ipv6_change_dsfield(ipv6_hdr(head), 0xff, ecn); IP6CB(head)->nhoff = nhoff; + IP6CB(head)->flags |= IP6SKB_FRAGMENTED; /* Yes, and fold redundant checksum back. 8) */ if (head->ip_summed == CHECKSUM_COMPLETE) @@ -524,6 +525,9 @@ static int ipv6_frag_rcv(struct sk_buff *skb) struct net *net = dev_net(skb_dst(skb)->dev); int evicted; + if (IP6CB(skb)->flags & IP6SKB_FRAGMENTED) + goto fail_hdr; + IP6_INC_STATS_BH(net, ip6_dst_idev(skb_dst(skb)), IPSTATS_MIB_REASMREQDS); /* Jumbo payload inhibits frag. header */ @@ -544,6 +548,7 @@ static int ipv6_frag_rcv(struct sk_buff *skb) ip6_dst_idev(skb_dst(skb)), IPSTATS_MIB_REASMOKS); IP6CB(skb)->nhoff = (u8 *)fhdr - skb_network_header(skb); + IP6CB(skb)->flags |= IP6SKB_FRAGMENTED; return 1; } -- cgit From c92a59eca86f5d13ae4d481c3bae6b54609fe006 Mon Sep 17 00:00:00 2001 From: Duan Jiong Date: Thu, 22 Aug 2013 12:07:35 +0800 Subject: ipv6: handle Redirect ICMP Message with no Redirected Header option rfc 4861 says the Redirected Header option is optional, so the kernel should not drop the Redirect Message that has no Redirected Header option. In this patch, the function ip6_redirect_no_header() is introduced to deal with that condition. Signed-off-by: Duan Jiong Acked-by: Hannes Frederic Sowa --- net/ipv6/ndisc.c | 4 +++- net/ipv6/route.c | 21 +++++++++++++++++++++ 2 files changed, 24 insertions(+), 1 deletion(-) (limited to 'net/ipv6') diff --git a/net/ipv6/ndisc.c b/net/ipv6/ndisc.c index 79aa9652ed86..04d31c2fbef1 100644 --- a/net/ipv6/ndisc.c +++ b/net/ipv6/ndisc.c @@ -1369,8 +1369,10 @@ static void ndisc_redirect_rcv(struct sk_buff *skb) if (!ndisc_parse_options(msg->opt, ndoptlen, &ndopts)) return; - if (!ndopts.nd_opts_rh) + if (!ndopts.nd_opts_rh) { + ip6_redirect_no_header(skb, dev_net(skb->dev), 0, 0); return; + } hdr = (u8 *)ndopts.nd_opts_rh; hdr += 8; diff --git a/net/ipv6/route.c b/net/ipv6/route.c index b70f8979003b..8d9a93ed9c59 100644 --- a/net/ipv6/route.c +++ b/net/ipv6/route.c @@ -1178,6 +1178,27 @@ void ip6_redirect(struct sk_buff *skb, struct net *net, int oif, u32 mark) } EXPORT_SYMBOL_GPL(ip6_redirect); +void ip6_redirect_no_header(struct sk_buff *skb, struct net *net, int oif, + u32 mark) +{ + const struct ipv6hdr *iph = ipv6_hdr(skb); + const struct rd_msg *msg = (struct rd_msg *)icmp6_hdr(skb); + struct dst_entry *dst; + struct flowi6 fl6; + + memset(&fl6, 0, sizeof(fl6)); + fl6.flowi6_oif = oif; + fl6.flowi6_mark = mark; + fl6.flowi6_flags = 0; + fl6.daddr = msg->dest; + fl6.saddr = iph->daddr; + + dst = ip6_route_output(net, NULL, &fl6); + if (!dst->error) + rt6_do_redirect(dst, NULL, skb); + dst_release(dst); +} + void ip6_sk_redirect(struct sk_buff *skb, struct sock *sk) { ip6_redirect(skb, sock_net(sk), sk->sk_bound_dev_if, sk->sk_mark); -- cgit