inet: switch IP ID generator to siphash
According to Amit Klein and Benny Pinkas, IP ID generation is too weak
and might be used by attackers.
Even with recent net_hash_mix() fix (netns: provide pure entropy for net_hash_mix())
having 64bit key and Jenkins hash is risky.
It is time to switch to siphash and its 128bit keys.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: Amit Klein <aksecurity@gmail.com>
Reported-by: Benny Pinkas <benny@pinkas.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index 14c7fda..f2688fc 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -500,15 +500,17 @@ EXPORT_SYMBOL(ip_idents_reserve);
void __ip_select_ident(struct net *net, struct iphdr *iph, int segs)
{
- static u32 ip_idents_hashrnd __read_mostly;
u32 hash, id;
- net_get_random_once(&ip_idents_hashrnd, sizeof(ip_idents_hashrnd));
+ /* Note the following code is not safe, but this is okay. */
+ if (unlikely(siphash_key_is_zero(&net->ipv4.ip_id_key)))
+ get_random_bytes(&net->ipv4.ip_id_key,
+ sizeof(net->ipv4.ip_id_key));
- hash = jhash_3words((__force u32)iph->daddr,
+ hash = siphash_3u32((__force u32)iph->daddr,
(__force u32)iph->saddr,
- iph->protocol ^ net_hash_mix(net),
- ip_idents_hashrnd);
+ iph->protocol,
+ &net->ipv4.ip_id_key);
id = ip_idents_reserve(hash, segs);
iph->id = htons(id);
}