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ipv6:introduce function to find route for redirect

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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
a6279458c5 ("NDISC: Search over
all possible rules on receipt of redirect.") and the check
went away in commit b94f1c0904
("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@cn.fujitsu.com>
Acked-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Duan Jiong 2013-09-04 19:44:21 +08:00 committed by David S. Miller
parent 60cad4e67b
commit b55b76b221
6 changed files with 81 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
net/ipv6/ah6.c
View File

@ -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);

2
net/ipv6/esp6.c
View File

@ -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);

2
net/ipv6/icmp.c
View File

@ -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)

2
net/ipv6/ipcomp6.c
View File

@ -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);

3
net/ipv6/ndisc.c
View File

@ -1367,7 +1367,8 @@ 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;
}

81
net/ipv6/route.c
View File

@ -1156,6 +1156,77 @@ 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;
@ -1170,9 +1241,8 @@ 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);
@ -1192,9 +1262,8 @@ 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);
}