From: Eric Dumazet Date: Wed, 27 Mar 2019 19:40:33 +0000 (-0700) Subject: inet: switch IP ID generator to siphash X-Git-Tag: v3.16.72~3 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=9ebeec41ed3f52fd94267f25f8b9bf3f4cbf1e4e;p=thirdparty%2Fkernel%2Fstable.git inet: switch IP ID generator to siphash 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 Reported-by: Amit Klein Reported-by: Benny Pinkas Signed-off-by: David S. Miller [bwh: Backported to 3.16: adjust context] Signed-off-by: Ben Hutchings --- diff --git a/include/linux/siphash.h b/include/linux/siphash.h index feeb29cd113ed..c8c7ae2e687bf 100644 --- 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); diff --git a/include/net/netns/ipv4.h b/include/net/netns/ipv4.h index 80a1c572b9a0d..213f53d4f6b23 100644 --- a/include/net/netns/ipv4.h +++ b/include/net/netns/ipv4.h @@ -7,6 +7,7 @@ #include #include +#include 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 diff --git a/net/ipv4/route.c b/net/ipv4/route.c index 5092304f31fba..858596c80e0e8 100644 --- 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); } diff --git a/net/ipv6/output_core.c b/net/ipv6/output_core.c index b1986acf08d34..a8274abad2316 100644 --- a/net/ipv6/output_core.c +++ b/net/ipv6/output_core.c @@ -9,14 +9,24 @@ #include #include -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 net *net, u32 hashrnd, */ 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 *net, struct sk_buff *skb) 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_ident); 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);