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Message-ID: <52271D15.1000806@cn.fujitsu.com>
Date: Wed, 04 Sep 2013 19:44:21 +0800
From: Duan Jiong <duanj.fnst@...fujitsu.com>
To: davem@...emloft.net
CC: duanj.fnst@...fujitsu.com, netdev@...r.kernel.org,
hannes@...essinduktion.org
Subject: [PATCH v5] ipv6:introduce function to find route for redirect
From: Duan Jiong <duanj.fnst@...fujitsu.com>
RFC 4861 says that the IP source address of the Redirect is the
same as the current first-hop router for the specified ICMP
Destination Address, so the gateway should be taken into
consideration when we find the route for redirect.
There was once a check in commit
a6279458c534d01ccc39498aba61c93083ee0372 ("NDISC: Search over
all possible rules on receipt of redirect.") and the check
went away in commit b94f1c0904da9b8bf031667afc48080ba7c3e8c9
("ipv6: Use icmpv6_notify() to propagate redirect, instead of
rt6_redirect()").
The bug is only "exploitable" on layer-2 because the source
address of the redirect is checked to be a valid link-local
address but it makes spoofing a lot easier in the same L2
domain nonetheless.
Thanks very much for Hannes's help.
Signed-off-by: Duan Jiong <duanj.fnst@...fujitsu.com>
---
Changes for v5:
1.check dst.error when look up route for redirect.
net/ipv6/ah6.c | 2 +-
net/ipv6/esp6.c | 2 +-
net/ipv6/icmp.c | 2 +-
net/ipv6/ipcomp6.c | 2 +-
net/ipv6/ndisc.c | 3 +-
net/ipv6/route.c | 81 ++++++++++++++++++++++++++++++++++++++++++++++++++----
6 files changed, 81 insertions(+), 11 deletions(-)
diff --git a/net/ipv6/ah6.c b/net/ipv6/ah6.c
index bb02e17..73784c3 100644
--- a/net/ipv6/ah6.c
+++ b/net/ipv6/ah6.c
@@ -628,7 +628,7 @@ static void ah6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
return;
if (type == NDISC_REDIRECT)
- ip6_redirect(skb, net, 0, 0);
+ ip6_redirect(skb, net, skb->dev->ifindex, 0);
else
ip6_update_pmtu(skb, net, info, 0, 0);
xfrm_state_put(x);
diff --git a/net/ipv6/esp6.c b/net/ipv6/esp6.c
index aeac0dc..d3618a7 100644
--- a/net/ipv6/esp6.c
+++ b/net/ipv6/esp6.c
@@ -447,7 +447,7 @@ static void esp6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
return;
if (type == NDISC_REDIRECT)
- ip6_redirect(skb, net, 0, 0);
+ ip6_redirect(skb, net, skb->dev->ifindex, 0);
else
ip6_update_pmtu(skb, net, info, 0, 0);
xfrm_state_put(x);
diff --git a/net/ipv6/icmp.c b/net/ipv6/icmp.c
index 7cfc8d2..73681c2 100644
--- a/net/ipv6/icmp.c
+++ b/net/ipv6/icmp.c
@@ -92,7 +92,7 @@ static void icmpv6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
if (type == ICMPV6_PKT_TOOBIG)
ip6_update_pmtu(skb, net, info, 0, 0);
else if (type == NDISC_REDIRECT)
- ip6_redirect(skb, net, 0, 0);
+ ip6_redirect(skb, net, skb->dev->ifindex, 0);
if (!(type & ICMPV6_INFOMSG_MASK))
if (icmp6->icmp6_type == ICMPV6_ECHO_REQUEST)
diff --git a/net/ipv6/ipcomp6.c b/net/ipv6/ipcomp6.c
index 7af5aee..5636a91 100644
--- a/net/ipv6/ipcomp6.c
+++ b/net/ipv6/ipcomp6.c
@@ -76,7 +76,7 @@ static void ipcomp6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
return;
if (type == NDISC_REDIRECT)
- ip6_redirect(skb, net, 0, 0);
+ ip6_redirect(skb, net, skb->dev->ifindex, 0);
else
ip6_update_pmtu(skb, net, info, 0, 0);
xfrm_state_put(x);
diff --git a/net/ipv6/ndisc.c b/net/ipv6/ndisc.c
index 04d31c2..70abece 100644
--- a/net/ipv6/ndisc.c
+++ b/net/ipv6/ndisc.c
@@ -1370,7 +1370,8 @@ static void ndisc_redirect_rcv(struct sk_buff *skb)
return;
if (!ndopts.nd_opts_rh) {
- ip6_redirect_no_header(skb, dev_net(skb->dev), 0, 0);
+ ip6_redirect_no_header(skb, dev_net(skb->dev),
+ skb->dev->ifindex, 0);
return;
}
diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index 8d9a93e..36ddf3e 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -1157,6 +1157,77 @@ void ip6_sk_update_pmtu(struct sk_buff *skb, struct sock *sk, __be32 mtu)
}
EXPORT_SYMBOL_GPL(ip6_sk_update_pmtu);
+/* Handle redirects */
+struct ip6rd_flowi {
+ struct flowi6 fl6;
+ struct in6_addr gateway;
+};
+
+static struct rt6_info *__ip6_route_redirect(struct net *net,
+ struct fib6_table *table,
+ struct flowi6 *fl6,
+ int flags)
+{
+ struct ip6rd_flowi *rdfl = (struct ip6rd_flowi *)fl6;
+ struct rt6_info *rt;
+ struct fib6_node *fn;
+
+ /* Get the "current" route for this destination and
+ * check if the redirect has come from approriate router.
+ *
+ * RFC 4861 specifies that redirects should only be
+ * accepted if they come from the nexthop to the target.
+ * Due to the way the routes are chosen, this notion
+ * is a bit fuzzy and one might need to check all possible
+ * routes.
+ */
+
+ read_lock_bh(&table->tb6_lock);
+ fn = fib6_lookup(&table->tb6_root, &fl6->daddr, &fl6->saddr);
+restart:
+ for (rt = fn->leaf; rt; rt = rt->dst.rt6_next) {
+ if (rt6_check_expired(rt))
+ continue;
+ if (rt->dst.error)
+ break;
+ if (!(rt->rt6i_flags & RTF_GATEWAY))
+ continue;
+ if (fl6->flowi6_oif != rt->dst.dev->ifindex)
+ continue;
+ if (!ipv6_addr_equal(&rdfl->gateway, &rt->rt6i_gateway))
+ continue;
+ break;
+ }
+
+ if (!rt)
+ rt = net->ipv6.ip6_null_entry;
+ else if (rt->dst.error) {
+ rt = net->ipv6.ip6_null_entry;
+ goto out;
+ }
+ BACKTRACK(net, &fl6->saddr);
+out:
+ dst_hold(&rt->dst);
+
+ read_unlock_bh(&table->tb6_lock);
+
+ return rt;
+};
+
+static struct dst_entry *ip6_route_redirect(struct net *net,
+ const struct flowi6 *fl6,
+ const struct in6_addr *gateway)
+{
+ int flags = RT6_LOOKUP_F_HAS_SADDR;
+ struct ip6rd_flowi rdfl;
+
+ rdfl.fl6 = *fl6;
+ rdfl.gateway = *gateway;
+
+ return fib6_rule_lookup(net, &rdfl.fl6,
+ flags, __ip6_route_redirect);
+}
+
void ip6_redirect(struct sk_buff *skb, struct net *net, int oif, u32 mark)
{
const struct ipv6hdr *iph = (struct ipv6hdr *) skb->data;
@@ -1171,9 +1242,8 @@ void ip6_redirect(struct sk_buff *skb, struct net *net, int oif, u32 mark)
fl6.saddr = iph->saddr;
fl6.flowlabel = ip6_flowinfo(iph);
- dst = ip6_route_output(net, NULL, &fl6);
- if (!dst->error)
- rt6_do_redirect(dst, NULL, skb);
+ dst = ip6_route_redirect(net, &fl6, &ipv6_hdr(skb)->saddr);
+ rt6_do_redirect(dst, NULL, skb);
dst_release(dst);
}
EXPORT_SYMBOL_GPL(ip6_redirect);
@@ -1193,9 +1263,8 @@ void ip6_redirect_no_header(struct sk_buff *skb, struct net *net, int oif,
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 = ip6_route_redirect(net, &fl6, &iph->saddr);
+ rt6_do_redirect(dst, NULL, skb);
dst_release(dst);
}
--
1.8.3.1
--
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