3.16.72-rc1 review patch. If anyone has any objections, please let me know.
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From: Eric Dumazet edumazet@google.com
commit df453700e8d81b1bdafdf684365ee2b9431fb702 upstream.
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 [bwh: Backported to 3.16: adjust context] Signed-off-by: Ben Hutchings ben@decadent.org.uk --- --- a/include/linux/siphash.h +++ b/include/linux/siphash.h @@ -19,6 +19,11 @@ typedef struct { u64 key[2]; } siphash_key_t;
+static inline bool siphash_key_is_zero(const siphash_key_t *key) +{ + return !(key->key[0] | key->key[1]); +} + u64 __siphash_aligned(const void *data, size_t len, const siphash_key_t *key); #ifndef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS u64 __siphash_unaligned(const void *data, size_t len, const siphash_key_t *key); --- a/include/net/netns/ipv4.h +++ b/include/net/netns/ipv4.h @@ -7,6 +7,7 @@
#include <linux/uidgid.h> #include <net/inet_frag.h> +#include <linux/siphash.h>
struct tcpm_hash_bucket; struct ctl_table_header; @@ -98,5 +99,6 @@ struct netns_ipv4 { #endif #endif atomic_t rt_genid; + siphash_key_t ip_id_key; }; #endif --- a/net/ipv4/route.c +++ b/net/ipv4/route.c @@ -486,15 +486,17 @@ 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); } --- a/net/ipv6/output_core.c +++ b/net/ipv6/output_core.c @@ -9,14 +9,24 @@ #include <net/addrconf.h> #include <net/secure_seq.h>
-static u32 __ipv6_select_ident(struct net *net, u32 hashrnd, +static u32 __ipv6_select_ident(struct net *net, struct in6_addr *dst, struct in6_addr *src) { + const struct { + struct in6_addr dst; + struct in6_addr src; + } __aligned(SIPHASH_ALIGNMENT) combined = { + .dst = *dst, + .src = *src, + }; u32 hash, id;
- hash = __ipv6_addr_jhash(dst, hashrnd); - hash = __ipv6_addr_jhash(src, hash); - hash ^= net_hash_mix(net); + /* 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 = siphash(&combined, sizeof(combined), &net->ipv4.ip_id_key);
/* Treat id of 0 as unset and if we get 0 back from ip_idents_reserve, * set the hight order instead thus minimizing possible future @@ -39,7 +49,6 @@ static u32 __ipv6_select_ident(struct ne */ void ipv6_proxy_select_ident(struct net *net, struct sk_buff *skb) { - static u32 ip6_proxy_idents_hashrnd __read_mostly; struct in6_addr buf[2]; struct in6_addr *addrs; u32 id; @@ -51,11 +60,7 @@ void ipv6_proxy_select_ident(struct net if (!addrs) return;
- net_get_random_once(&ip6_proxy_idents_hashrnd, - sizeof(ip6_proxy_idents_hashrnd)); - - id = __ipv6_select_ident(net, ip6_proxy_idents_hashrnd, - &addrs[1], &addrs[0]); + id = __ipv6_select_ident(net, &addrs[1], &addrs[0]); skb_shinfo(skb)->ip6_frag_id = htonl(id); } EXPORT_SYMBOL_GPL(ipv6_proxy_select_ident); @@ -63,13 +68,9 @@ EXPORT_SYMBOL_GPL(ipv6_proxy_select_iden void ipv6_select_ident(struct net *net, struct frag_hdr *fhdr, struct rt6_info *rt) { - static u32 ip6_idents_hashrnd __read_mostly; u32 id;
- net_get_random_once(&ip6_idents_hashrnd, sizeof(ip6_idents_hashrnd)); - - id = __ipv6_select_ident(net, ip6_idents_hashrnd, &rt->rt6i_dst.addr, - &rt->rt6i_src.addr); + id = __ipv6_select_ident(net, &rt->rt6i_dst.addr, &rt->rt6i_src.addr); fhdr->identification = htonl(id); } EXPORT_SYMBOL(ipv6_select_ident);