ipv6: make fragment identifications less predictable
IPv6 fragment identification generation is way beyond what we use for
IPv4 : It uses a single generator. Its not scalable and allows DOS
attacks.
Now inetpeer is IPv6 aware, we can use it to provide a more secure and
scalable frag ident generator (per destination, instead of system wide)
This patch :
1) defines a new secure_ipv6_id() helper
2) extends inet_getid() to provide 32bit results
3) extends ipv6_select_ident() with a new dest parameter
Reported-by: Fernando Gont <fernando@gont.com.ar>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
index 8db0e48..32e5339 100644
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -596,6 +596,31 @@
return offset;
}
+void ipv6_select_ident(struct frag_hdr *fhdr, struct rt6_info *rt)
+{
+ static atomic_t ipv6_fragmentation_id;
+ int old, new;
+
+ if (rt) {
+ struct inet_peer *peer;
+
+ if (!rt->rt6i_peer)
+ rt6_bind_peer(rt, 1);
+ peer = rt->rt6i_peer;
+ if (peer) {
+ fhdr->identification = htonl(inet_getid(peer, 0));
+ return;
+ }
+ }
+ do {
+ old = atomic_read(&ipv6_fragmentation_id);
+ new = old + 1;
+ if (!new)
+ new = 1;
+ } while (atomic_cmpxchg(&ipv6_fragmentation_id, old, new) != old);
+ fhdr->identification = htonl(new);
+}
+
int ip6_fragment(struct sk_buff *skb, int (*output)(struct sk_buff *))
{
struct sk_buff *frag;
@@ -680,7 +705,7 @@
skb_reset_network_header(skb);
memcpy(skb_network_header(skb), tmp_hdr, hlen);
- ipv6_select_ident(fh);
+ ipv6_select_ident(fh, rt);
fh->nexthdr = nexthdr;
fh->reserved = 0;
fh->frag_off = htons(IP6_MF);
@@ -826,7 +851,7 @@
fh->nexthdr = nexthdr;
fh->reserved = 0;
if (!frag_id) {
- ipv6_select_ident(fh);
+ ipv6_select_ident(fh, rt);
frag_id = fh->identification;
} else
fh->identification = frag_id;
@@ -1076,7 +1101,8 @@
int getfrag(void *from, char *to, int offset, int len,
int odd, struct sk_buff *skb),
void *from, int length, int hh_len, int fragheaderlen,
- int transhdrlen, int mtu,unsigned int flags)
+ int transhdrlen, int mtu,unsigned int flags,
+ struct rt6_info *rt)
{
struct sk_buff *skb;
@@ -1120,7 +1146,7 @@
skb_shinfo(skb)->gso_size = (mtu - fragheaderlen -
sizeof(struct frag_hdr)) & ~7;
skb_shinfo(skb)->gso_type = SKB_GSO_UDP;
- ipv6_select_ident(&fhdr);
+ ipv6_select_ident(&fhdr, rt);
skb_shinfo(skb)->ip6_frag_id = fhdr.identification;
__skb_queue_tail(&sk->sk_write_queue, skb);
@@ -1286,7 +1312,7 @@
err = ip6_ufo_append_data(sk, getfrag, from, length,
hh_len, fragheaderlen,
- transhdrlen, mtu, flags);
+ transhdrlen, mtu, flags, rt);
if (err)
goto error;
return 0;