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Subject[PATCH net-next v3 6/9] inet: split syncookie keys for ipv4 and ipv6 and initialize with net_get_random_once
Date
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>
---
include/net/tcp.h | 1 -
net/ipv4/syncookies.c | 15 +++++----------
net/ipv6/syncookies.c | 12 +++++++++---
3 files changed, 14 insertions(+), 14 deletions(-)

diff --git a/include/net/tcp.h b/include/net/tcp.h
index 1db3a01..0fa8fdc 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -475,7 +475,6 @@ int tcp_send_rcvq(struct sock *sk, struct msghdr *msg, size_t size);
void inet_sk_rx_dst_set(struct sock *sk, const struct sk_buff *skb);

/* From syncookies.c */
-extern __u32 syncookie_secret[2][16-4+SHA_DIGEST_WORDS];
int __cookie_v4_check(const struct iphdr *iph, const struct tcphdr *th,
u32 cookie);
struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb,
diff --git a/net/ipv4/syncookies.c b/net/ipv4/syncookies.c
index 3b64c59..b95331e 100644
--- a/net/ipv4/syncookies.c
+++ b/net/ipv4/syncookies.c
@@ -25,15 +25,7 @@

extern int sysctl_tcp_syncookies;

-__u32 syncookie_secret[2][16-4+SHA_DIGEST_WORDS];
-EXPORT_SYMBOL(syncookie_secret);
-
-static __init int init_syncookies(void)
-{
- get_random_bytes(syncookie_secret, sizeof(syncookie_secret));
- return 0;
-}
-__initcall(init_syncookies);
+static u32 syncookie_secret[2][16-4+SHA_DIGEST_WORDS];

#define COOKIEBITS 24 /* Upper bits store count */
#define COOKIEMASK (((__u32)1 << COOKIEBITS) - 1)
@@ -44,8 +36,11 @@ static DEFINE_PER_CPU(__u32 [16 + 5 + SHA_WORKSPACE_WORDS],
static u32 cookie_hash(__be32 saddr, __be32 daddr, __be16 sport, __be16 dport,
u32 count, int c)
{
- __u32 *tmp = __get_cpu_var(ipv4_cookie_scratch);
+ __u32 *tmp;
+
+ net_get_random_once(syncookie_secret, sizeof(syncookie_secret));

+ tmp = __get_cpu_var(ipv4_cookie_scratch);
memcpy(tmp + 4, syncookie_secret[c], sizeof(syncookie_secret[c]));
tmp[0] = (__force u32)saddr;
tmp[1] = (__force u32)daddr;
diff --git a/net/ipv6/syncookies.c b/net/ipv6/syncookies.c
index d04d3f1..535a3ad 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;
--
1.8.3.1


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