From df453700e8d81b1bdafdf684365ee2b9431fb702 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Wed, 27 Mar 2019 12:40:33 -0700 Subject: 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 Reported-by: Amit Klein Reported-by: Benny Pinkas Signed-off-by: David S. Miller --- net/ipv4/route.c | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-) (limited to 'net/ipv4') diff --git a/net/ipv4/route.c b/net/ipv4/route.c index 14c7fdacaa72..f2688fce39e1 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); } -- cgit v1.2.3-59-g8ed1b