releases/5.1.7/inet-switch-ip-id-generator-to-siphash.patch

   1 From foo@baz Fri 31 May 2019 03:16:39 PM PDT
   2 From: Eric Dumazet <edumazet@google.com>
   3 Date: Wed, 27 Mar 2019 12:40:33 -0700
   4 Subject: inet: switch IP ID generator to siphash
   5
   6 From: Eric Dumazet <edumazet@google.com>
   7
   8 [ Upstream commit df453700e8d81b1bdafdf684365ee2b9431fb702 ]
   9
  10 According to Amit Klein and Benny Pinkas, IP ID generation is too weak
  11 and might be used by attackers.
  12
  13 Even with recent net_hash_mix() fix (netns: provide pure entropy for net_hash_mix())
  14 having 64bit key and Jenkins hash is risky.
  15
  16 It is time to switch to siphash and its 128bit keys.
  17
  18 Signed-off-by: Eric Dumazet <edumazet@google.com>
  19 Reported-by: Amit Klein <aksecurity@gmail.com>
  20 Reported-by: Benny Pinkas <benny@pinkas.net>
  21 Signed-off-by: David S. Miller <davem@davemloft.net>
  22 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  23 ---
  24  include/linux/siphash.h  |    5 +++++
  25  include/net/netns/ipv4.h |    2 ++
  26  net/ipv4/route.c         |   12 +++++++-----
  27  net/ipv6/output_core.c   |   30 ++++++++++++++++--------------
  28  4 files changed, 30 insertions(+), 19 deletions(-)
  29
  30 --- a/include/linux/siphash.h
  31 +++ b/include/linux/siphash.h
  32 @@ -21,6 +21,11 @@ typedef struct {
  33         u64 key[2];
  34  } siphash_key_t;
  35
  36 +static inline bool siphash_key_is_zero(const siphash_key_t *key)
  37 +{
  38 +       return !(key->key[0] | key->key[1]);
  39 +}
  40 +
  41  u64 __siphash_aligned(const void *data, size_t len, const siphash_key_t *key);
  42  #ifndef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
  43  u64 __siphash_unaligned(const void *data, size_t len, const siphash_key_t *key);
  44 --- a/include/net/netns/ipv4.h
  45 +++ b/include/net/netns/ipv4.h
  46 @@ -9,6 +9,7 @@
  47  #include <linux/uidgid.h>
  48  #include <net/inet_frag.h>
  49  #include <linux/rcupdate.h>
  50 +#include <linux/siphash.h>
  51
  52  struct tcpm_hash_bucket;
  53  struct ctl_table_header;
  54 @@ -217,5 +218,6 @@ struct netns_ipv4 {
  55         unsigned int    ipmr_seq;       /* protected by rtnl_mutex */
  56
  57         atomic_t        rt_genid;
  58 +       siphash_key_t   ip_id_key;
  59  };
  60  #endif
  61 --- a/net/ipv4/route.c
  62 +++ b/net/ipv4/route.c
  63 @@ -500,15 +500,17 @@ EXPORT_SYMBOL(ip_idents_reserve);
  64
  65  void __ip_select_ident(struct net *net, struct iphdr *iph, int segs)
  66  {
  67 -       static u32 ip_idents_hashrnd __read_mostly;
  68         u32 hash, id;
  69
  70 -       net_get_random_once(&ip_idents_hashrnd, sizeof(ip_idents_hashrnd));
  71 +       /* Note the following code is not safe, but this is okay. */
  72 +       if (unlikely(siphash_key_is_zero(&net->ipv4.ip_id_key)))
  73 +               get_random_bytes(&net->ipv4.ip_id_key,
  74 +                                sizeof(net->ipv4.ip_id_key));
  75
  76 -       hash = jhash_3words((__force u32)iph->daddr,
  77 +       hash = siphash_3u32((__force u32)iph->daddr,
  78                             (__force u32)iph->saddr,
  79 -                           iph->protocol ^ net_hash_mix(net),
  80 -                           ip_idents_hashrnd);
  81 +                           iph->protocol,
  82 +                           &net->ipv4.ip_id_key);
  83         id = ip_idents_reserve(hash, segs);
  84         iph->id = htons(id);
  85  }
  86 --- a/net/ipv6/output_core.c
  87 +++ b/net/ipv6/output_core.c
  88 @@ -10,15 +10,25 @@
  89  #include <net/secure_seq.h>
  90  #include <linux/netfilter.h>
  91
  92 -static u32 __ipv6_select_ident(struct net *net, u32 hashrnd,
  93 +static u32 __ipv6_select_ident(struct net *net,
  94                                const struct in6_addr *dst,
  95                                const struct in6_addr *src)
  96  {
  97 +       const struct {
  98 +               struct in6_addr dst;
  99 +               struct in6_addr src;
 100 +       } __aligned(SIPHASH_ALIGNMENT) combined = {
 101 +               .dst = *dst,
 102 +               .src = *src,
 103 +       };
 104         u32 hash, id;
 105
 106 -       hash = __ipv6_addr_jhash(dst, hashrnd);
 107 -       hash = __ipv6_addr_jhash(src, hash);
 108 -       hash ^= net_hash_mix(net);
 109 +       /* Note the following code is not safe, but this is okay. */
 110 +       if (unlikely(siphash_key_is_zero(&net->ipv4.ip_id_key)))
 111 +               get_random_bytes(&net->ipv4.ip_id_key,
 112 +                                sizeof(net->ipv4.ip_id_key));
 113 +
 114 +       hash = siphash(&combined, sizeof(combined), &net->ipv4.ip_id_key);
 115
 116         /* Treat id of 0 as unset and if we get 0 back from ip_idents_reserve,
 117          * set the hight order instead thus minimizing possible future
 118 @@ -41,7 +51,6 @@ static u32 __ipv6_select_ident(struct ne
 119   */
 120  __be32 ipv6_proxy_select_ident(struct net *net, struct sk_buff *skb)
 121  {
 122 -       static u32 ip6_proxy_idents_hashrnd __read_mostly;
 123         struct in6_addr buf[2];
 124         struct in6_addr *addrs;
 125         u32 id;
 126 @@ -53,11 +62,7 @@ __be32 ipv6_proxy_select_ident(struct ne
 127         if (!addrs)
 128                 return 0;
 129
 130 -       net_get_random_once(&ip6_proxy_idents_hashrnd,
 131 -                           sizeof(ip6_proxy_idents_hashrnd));
 132 -
 133 -       id = __ipv6_select_ident(net, ip6_proxy_idents_hashrnd,
 134 -                                &addrs[1], &addrs[0]);
 135 +       id = __ipv6_select_ident(net, &addrs[1], &addrs[0]);
 136         return htonl(id);
 137  }
 138  EXPORT_SYMBOL_GPL(ipv6_proxy_select_ident);
 139 @@ -66,12 +71,9 @@ __be32 ipv6_select_ident(struct net *net
 140                          const struct in6_addr *daddr,
 141                          const struct in6_addr *saddr)
 142  {
 143 -       static u32 ip6_idents_hashrnd __read_mostly;
 144         u32 id;
 145
 146 -       net_get_random_once(&ip6_idents_hashrnd, sizeof(ip6_idents_hashrnd));
 147 -
 148 -       id = __ipv6_select_ident(net, ip6_idents_hashrnd, daddr, saddr);
 149 +       id = __ipv6_select_ident(net, daddr, saddr);
 150         return htonl(id);
 151  }
 152  EXPORT_SYMBOL(ipv6_select_ident);