diff options
| author | Hannes Frederic Sowa <hannes@stressinduktion.org> | 2013-10-19 21:48:58 +0200 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2013-10-19 19:45:35 -0400 |
| commit | 222e83d2e0aecb6a5e8d42b1a8d51332a1eba960 (patch) | |
| tree | 395011fb151ed3ce911333e1ab70602b2cfbc3e0 | |
| parent | 1bbdceef1e535add893bf71d7b7ab102e4eb69eb (diff) | |
| download | linux-222e83d2e0aecb6a5e8d42b1a8d51332a1eba960.tar.bz2 | |
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>
| -rw-r--r-- | include/net/tcp.h | 2 | ||||
| -rw-r--r-- | net/ipv4/sysctl_net_ipv4.c | 5 | ||||
| -rw-r--r-- | net/ipv4/tcp_fastopen.c | 27 |
3 files changed, 22 insertions, 12 deletions
diff --git a/include/net/tcp.h b/include/net/tcp.h index f30326f1c92b..b12e29a76590 100644 --- a/include/net/tcp.h +++ b/include/net/tcp.h @@ -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 */ diff --git a/net/ipv4/sysctl_net_ipv4.c b/net/ipv4/sysctl_net_ipv4.c index c08f096d46b5..4b161d5aba0b 100644 --- a/net/ipv4/sysctl_net_ipv4.c +++ b/net/ipv4/sysctl_net_ipv4.c @@ -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); } diff --git a/net/ipv4/tcp_fastopen.c b/net/ipv4/tcp_fastopen.c index ab7bd35bb312..766032b4a6c3 100644 --- a/net/ipv4/tcp_fastopen.c +++ b/net/ipv4/tcp_fastopen.c @@ -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); |