inet: split syncookie keys for ipv4 and ipv6 and initialize with net_get_random_once

This patch splits the secret key for syncookies for ipv4 and ipv6 and
initializes them with net_get_random_once. This change was the reason I
did this series. I think the initialization of the syncookie_secret is
way to early.

Cc: Florian Westphal <fw@strlen.de>
Cc: Eric Dumazet <edumazet@google.com>
Cc: "David S. Miller" <davem@davemloft.net>
Signed-off-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 9 insertions, 3 deletions

diff --git a/net/ipv6/syncookies.c b/net/ipv6/syncookies.c
index d04d3f1dd9b7..535a3ad262f1 100644
--- a/net/ipv6/syncookies.c
+++ b/net/ipv6/syncookies.c
@@ -24,6 +24,8 @@
 #define COOKIEBITS 24   /* Upper bits store count */
 #define COOKIEMASK (((__u32)1 << COOKIEBITS) - 1)
 
+static u32 syncookie6_secret[2][16-4+SHA_DIGEST_WORDS];
+
 /* RFC 2460, Section 8.3:
  * [ipv6 tcp] MSS must be computed as the maximum packet size minus 60 [..]
  *
@@ -61,14 +63,18 @@ static DEFINE_PER_CPU(__u32 [16 + 5 + SHA_WORKSPACE_WORDS],
 static u32 cookie_hash(const struct in6_addr *saddr, const struct in6_addr *daddr,
                        __be16 sport, __be16 dport, u32 count, int c)
 {
-        __u32 *tmp = __get_cpu_var(ipv6_cookie_scratch);
+        __u32 *tmp;
+
+        net_get_random_once(syncookie6_secret, sizeof(syncookie6_secret));
+
+        tmp  = __get_cpu_var(ipv6_cookie_scratch);
 
         /*
          * we have 320 bits of information to hash, copy in the remaining
-         * 192 bits required for sha_transform, from the syncookie_secret
+         * 192 bits required for sha_transform, from the syncookie6_secret
          * and overwrite the digest with the secret
          */
-        memcpy(tmp + 10, syncookie_secret[c], 44);
+        memcpy(tmp + 10, syncookie6_secret[c], 44);
         memcpy(tmp, saddr, 16);
         memcpy(tmp + 4, daddr, 16);
         tmp[8] = ((__force u32)sport << 16) + (__force u32)dport;