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| author | Eric Dumazet <edumazet@google.com> | 2017-05-05 06:56:54 -0700 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2017-05-05 12:00:11 -0400 |
| commit | 84b114b98452c431299d99c135f751659e517acb (patch) | |
| tree | 53778bfd4964bed65ac40a9c1c57a73f21cb9664 /include/net/tcp.h | |
| parent | 9051247dcf9ecee156d2ddac39a4f1ca591f8428 (diff) | |
| download | linux-84b114b98452c431299d99c135f751659e517acb.tar.gz | |
tcp: randomize timestamps on syncookies
Whole point of randomization was to hide server uptime, but an attacker
can simply start a syn flood and TCP generates 'old style' timestamps,
directly revealing server jiffies value.
Also, TSval sent by the server to a particular remote address vary
depending on syncookies being sent or not, potentially triggering PAWS
drops for innocent clients.
Lets implement proper randomization, including for SYNcookies.
Also we do not need to export sysctl_tcp_timestamps, since it is not
used from a module.
In v2, I added Florian feedback and contribution, adding tsoff to
tcp_get_cookie_sock().
v3 removed one unused variable in tcp_v4_connect() as Florian spotted.
Fixes: 95a22caee396c ("tcp: randomize tcp timestamp offsets for each connection")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Florian Westphal <fw@strlen.de>
Tested-by: Florian Westphal <fw@strlen.de>
Cc: Yuchung Cheng <ycheng@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'include/net/tcp.h')
| -rw-r--r-- | include/net/tcp.h | 5 |
1 files changed, 3 insertions, 2 deletions
diff --git a/include/net/tcp.h b/include/net/tcp.h index 270e5cc43c99..8c0e5a901d64 100644 --- a/include/net/tcp.h +++ b/include/net/tcp.h @@ -470,7 +470,7 @@ void inet_sk_rx_dst_set(struct sock *sk, const struct sk_buff *skb); /* From syncookies.c */ struct sock *tcp_get_cookie_sock(struct sock *sk, struct sk_buff *skb, struct request_sock *req, - struct dst_entry *dst); + struct dst_entry *dst, u32 tsoff); 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); @@ -1822,7 +1822,8 @@ struct tcp_request_sock_ops { #endif struct dst_entry *(*route_req)(const struct sock *sk, struct flowi *fl, const struct request_sock *req); - __u32 (*init_seq_tsoff)(const struct sk_buff *skb, u32 *tsoff); + u32 (*init_seq)(const struct sk_buff *skb); + u32 (*init_ts_off)(const struct sk_buff *skb); int (*send_synack)(const struct sock *sk, struct dst_entry *dst, struct flowi *fl, struct request_sock *req, struct tcp_fastopen_cookie *foc, |