diff options
author | Florian Westphal <fw@strlen.de> | 2010-06-16 21:42:15 (GMT) |
---|---|---|
committer | David S. Miller <davem@davemloft.net> | 2010-06-16 21:42:15 (GMT) |
commit | 8c76368174ed2359739f1b7b8a9c042b1ef839c4 (patch) | |
tree | 143aa28c9438b24154bc3d1e36b432a534eca50c | |
parent | 317fe0e6c5dc9448bcef41a2e31fecfd3dba7f55 (diff) | |
download | linux-8c76368174ed2359739f1b7b8a9c042b1ef839c4.tar.xz |
syncookies: check decoded options against sysctl settings
Discard the ACK if we find options that do not match current sysctl
settings.
Previously it was possible to create a connection with sack, wscale,
etc. enabled even if the feature was disabled via sysctl.
Also remove an unneeded call to tcp_sack_reset() in
cookie_check_timestamp: Both call sites (cookie_v4_check,
cookie_v6_check) zero "struct tcp_options_received", hand it to
tcp_parse_options() (which does not change tcp_opt->num_sacks/dsack)
and then call cookie_check_timestamp().
Even if num_sacks/dsacks were changed, the structure is allocated on
the stack and after cookie_check_timestamp returns only a few selected
members are copied to the inet_request_sock.
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
-rw-r--r-- | include/net/tcp.h | 2 | ||||
-rw-r--r-- | net/ipv4/syncookies.c | 25 | ||||
-rw-r--r-- | net/ipv6/syncookies.c | 4 |
3 files changed, 22 insertions, 9 deletions
diff --git a/include/net/tcp.h b/include/net/tcp.h index 9e68e25..18c246c 100644 --- a/include/net/tcp.h +++ b/include/net/tcp.h @@ -464,7 +464,7 @@ extern __u32 cookie_v4_init_sequence(struct sock *sk, struct sk_buff *skb, __u16 *mss); extern __u32 cookie_init_timestamp(struct request_sock *req); -extern void cookie_check_timestamp(struct tcp_options_received *tcp_opt); +extern bool cookie_check_timestamp(struct tcp_options_received *tcp_opt); /* From net/ipv6/syncookies.c */ extern struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb); diff --git a/net/ipv4/syncookies.c b/net/ipv4/syncookies.c index 02bef6a..51b5662 100644 --- a/net/ipv4/syncookies.c +++ b/net/ipv4/syncookies.c @@ -230,23 +230,36 @@ static inline struct sock *get_cookie_sock(struct sock *sk, struct sk_buff *skb, * The lowest 4 bits are for snd_wscale * The next 4 lsb are for rcv_wscale * The next lsb is for sack_ok + * + * return false if we decode an option that should not be. */ -void cookie_check_timestamp(struct tcp_options_received *tcp_opt) +bool cookie_check_timestamp(struct tcp_options_received *tcp_opt) { /* echoed timestamp, 9 lowest bits contain options */ u32 options = tcp_opt->rcv_tsecr & TSMASK; + if (!tcp_opt->saw_tstamp) { + tcp_clear_options(tcp_opt); + return true; + } + + if (!sysctl_tcp_timestamps) + return false; + tcp_opt->snd_wscale = options & 0xf; options >>= 4; tcp_opt->rcv_wscale = options & 0xf; tcp_opt->sack_ok = (options >> 4) & 0x1; - if (tcp_opt->sack_ok) - tcp_sack_reset(tcp_opt); + if (tcp_opt->sack_ok && !sysctl_tcp_sack) + return false; - if (tcp_opt->snd_wscale || tcp_opt->rcv_wscale) + if (tcp_opt->snd_wscale || tcp_opt->rcv_wscale) { tcp_opt->wscale_ok = 1; + return sysctl_tcp_window_scaling != 0; + } + return true; } EXPORT_SYMBOL(cookie_check_timestamp); @@ -281,8 +294,8 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb, memset(&tcp_opt, 0, sizeof(tcp_opt)); tcp_parse_options(skb, &tcp_opt, &hash_location, 0); - if (tcp_opt.saw_tstamp) - cookie_check_timestamp(&tcp_opt); + if (!cookie_check_timestamp(&tcp_opt)) + goto out; ret = NULL; req = inet_reqsk_alloc(&tcp_request_sock_ops); /* for safety */ diff --git a/net/ipv6/syncookies.c b/net/ipv6/syncookies.c index 70d330f..c7ee574 100644 --- a/net/ipv6/syncookies.c +++ b/net/ipv6/syncookies.c @@ -180,8 +180,8 @@ struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb) memset(&tcp_opt, 0, sizeof(tcp_opt)); tcp_parse_options(skb, &tcp_opt, &hash_location, 0); - if (tcp_opt.saw_tstamp) - cookie_check_timestamp(&tcp_opt); + if (!cookie_check_timestamp(&tcp_opt)) + goto out; ret = NULL; req = inet6_reqsk_alloc(&tcp6_request_sock_ops); |