| From foo@baz Fri 31 May 2019 03:16:57 PM PDT |
| From: Eric Dumazet <edumazet@google.com> |
| Date: Wed, 27 Mar 2019 12:40:33 -0700 |
| Subject: inet: switch IP ID generator to siphash |
| |
| From: Eric Dumazet <edumazet@google.com> |
| |
| [ Upstream commit df453700e8d81b1bdafdf684365ee2b9431fb702 ] |
| |
| 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> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| --- |
| include/linux/siphash.h | 5 +++++ |
| include/net/netns/ipv4.h | 2 ++ |
| net/ipv4/route.c | 12 +++++++----- |
| net/ipv6/output_core.c | 30 ++++++++++++++++-------------- |
| 4 files changed, 30 insertions(+), 19 deletions(-) |
| |
| --- a/include/linux/siphash.h |
| +++ b/include/linux/siphash.h |
| @@ -21,6 +21,11 @@ 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 |
| @@ -9,6 +9,7 @@ |
| #include <linux/uidgid.h> |
| #include <net/inet_frag.h> |
| #include <linux/rcupdate.h> |
| +#include <linux/siphash.h> |
| |
| struct tcpm_hash_bucket; |
| struct ctl_table_header; |
| @@ -217,5 +218,6 @@ struct netns_ipv4 { |
| unsigned int ipmr_seq; /* protected by rtnl_mutex */ |
| |
| atomic_t rt_genid; |
| + siphash_key_t ip_id_key; |
| }; |
| #endif |
| --- 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); |
| } |
| --- a/net/ipv6/output_core.c |
| +++ b/net/ipv6/output_core.c |
| @@ -10,15 +10,25 @@ |
| #include <net/secure_seq.h> |
| #include <linux/netfilter.h> |
| |
| -static u32 __ipv6_select_ident(struct net *net, u32 hashrnd, |
| +static u32 __ipv6_select_ident(struct net *net, |
| const struct in6_addr *dst, |
| const 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 |
| @@ -41,7 +51,6 @@ static u32 __ipv6_select_ident(struct ne |
| */ |
| __be32 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; |
| @@ -53,11 +62,7 @@ __be32 ipv6_proxy_select_ident(struct ne |
| if (!addrs) |
| return 0; |
| |
| - 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]); |
| return htonl(id); |
| } |
| EXPORT_SYMBOL_GPL(ipv6_proxy_select_ident); |
| @@ -66,12 +71,9 @@ __be32 ipv6_select_ident(struct net *net |
| const struct in6_addr *daddr, |
| const struct in6_addr *saddr) |
| { |
| - 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, daddr, saddr); |
| + id = __ipv6_select_ident(net, daddr, saddr); |
| return htonl(id); |
| } |
| EXPORT_SYMBOL(ipv6_select_ident); |