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tcp: switch tcp_fastopen key generation to net_get_random_once 

Changed key initialization of tcp_fastopen cookies to net_get_random_once.

If the user sets a custom key net_get_random_once must be called at
least once to ensure we don't overwrite the user provided key when the
first cookie is generated later on.

Cc: Yuchung Cheng <ycheng@google.com>
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>
This commit is contained in:
Hannes Frederic Sowa 2013-10-19 21:48:58 +02:00 committed by David S. Miller
parent 1bbdceef1e
commit 222e83d2e0
3 changed files with 22 additions and 12 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
include/net/tcp.h
View File

@ -1322,7 +1322,7 @@ extern struct tcp_fastopen_context __rcu *tcp_fastopen_ctx;
int tcp_fastopen_reset_cipher(void *key, unsigned int len);
void tcp_fastopen_cookie_gen(__be32 src, __be32 dst,
struct tcp_fastopen_cookie *foc);
void tcp_fastopen_init_key_once(bool publish);
#define TCP_FASTOPEN_KEY_LENGTH 16
/* Fastopen key context */

5
net/ipv4/sysctl_net_ipv4.c
View File

@ -274,6 +274,11 @@ static int proc_tcp_fastopen_key(struct ctl_table *ctl, int write,
ret = -EINVAL;
goto bad_key;
}
/* Generate a dummy secret but don't publish it. This
* is needed so we don't regenerate a new key on the
* first invocation of tcp_fastopen_cookie_gen
*/
tcp_fastopen_init_key_once(false);
tcp_fastopen_reset_cipher(user_key, TCP_FASTOPEN_KEY_LENGTH);
}

27
net/ipv4/tcp_fastopen.c
View File

@ -14,6 +14,20 @@ struct tcp_fastopen_context __rcu *tcp_fastopen_ctx;
static DEFINE_SPINLOCK(tcp_fastopen_ctx_lock);
void tcp_fastopen_init_key_once(bool publish)
{
static u8 key[TCP_FASTOPEN_KEY_LENGTH];
/* tcp_fastopen_reset_cipher publishes the new context
* atomically, so we allow this race happening here.
*
* All call sites of tcp_fastopen_cookie_gen also check
* for a valid cookie, so this is an acceptable risk.
*/
if (net_get_random_once(key, sizeof(key)) && publish)
tcp_fastopen_reset_cipher(key, sizeof(key));
}
static void tcp_fastopen_ctx_free(struct rcu_head *head)
{
struct tcp_fastopen_context *ctx =
@ -70,6 +84,8 @@ void tcp_fastopen_cookie_gen(__be32 src, __be32 dst,
__be32 path[4] = { src, dst, 0, 0 };
struct tcp_fastopen_context *ctx;
tcp_fastopen_init_key_once(true);
rcu_read_lock();
ctx = rcu_dereference(tcp_fastopen_ctx);
if (ctx) {
@ -78,14 +94,3 @@ void tcp_fastopen_cookie_gen(__be32 src, __be32 dst,
}
rcu_read_unlock();
}
static int __init tcp_fastopen_init(void)
{
__u8 key[TCP_FASTOPEN_KEY_LENGTH];
get_random_bytes(key, sizeof(key));
tcp_fastopen_reset_cipher(key, sizeof(key));
return 0;
}
late_initcall(tcp_fastopen_init);