diff options
Diffstat (limited to 'tcp-make-challenge-acks-less-predictable.patch')
| -rw-r--r-- | tcp-make-challenge-acks-less-predictable.patch | 81 |
1 files changed, 0 insertions, 81 deletions
diff --git a/tcp-make-challenge-acks-less-predictable.patch b/tcp-make-challenge-acks-less-predictable.patch deleted file mode 100644 index 6837cff0b..000000000 --- a/tcp-make-challenge-acks-less-predictable.patch +++ /dev/null @@ -1,81 +0,0 @@ -From 0af29b4f03b40fe0980c31d18e352f2ef19ec703 Mon Sep 17 00:00:00 2001 -From: Eric Dumazet <edumazet@google.com> -Date: Sun, 10 Jul 2016 10:04:02 +0200 -Subject: [PATCH] tcp: make challenge acks less predictable - -Yue Cao claims that current host rate limiting of challenge ACKS -(RFC 5961) could leak enough information to allow a patient attacker -to hijack TCP sessions. He will soon provide details in an academic -paper. - -This patch increases the default limit from 100 to 1000, and adds -some randomization so that the attacker can no longer hijack -sessions without spending a considerable amount of probes. - -Based on initial analysis and patch from Linus. - -Note that we also have per socket rate limiting, so it is tempting -to remove the host limit in the future. - -v2: randomize the count of challenge acks per second, not the period. - -Fixes: 282f23c6ee34 ("tcp: implement RFC 5961 3.2") -Reported-by: Yue Cao <ycao009@ucr.edu> -Signed-off-by: Eric Dumazet <edumazet@google.com> -Suggested-by: Linus Torvalds <torvalds@linux-foundation.org> -Cc: Yuchung Cheng <ycheng@google.com> -Cc: Neal Cardwell <ncardwell@google.com> -Acked-by: Neal Cardwell <ncardwell@google.com> -Acked-by: Yuchung Cheng <ycheng@google.com> -Signed-off-by: David S. Miller <davem@davemloft.net> ---- - net/ipv4/tcp_input.c | 15 ++++++++++----- - 1 file changed, 10 insertions(+), 5 deletions(-) - -diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c -index d6c8f4cd0800..91868bb17818 100644 ---- a/net/ipv4/tcp_input.c -+++ b/net/ipv4/tcp_input.c -@@ -87,7 +87,7 @@ int sysctl_tcp_adv_win_scale __read_mostly = 1; - EXPORT_SYMBOL(sysctl_tcp_adv_win_scale); - - /* rfc5961 challenge ack rate limiting */ --int sysctl_tcp_challenge_ack_limit = 100; -+int sysctl_tcp_challenge_ack_limit = 1000; - - int sysctl_tcp_stdurg __read_mostly; - int sysctl_tcp_rfc1337 __read_mostly; -@@ -3458,7 +3458,7 @@ static void tcp_send_challenge_ack(struct sock *sk, const struct sk_buff *skb) - static u32 challenge_timestamp; - static unsigned int challenge_count; - struct tcp_sock *tp = tcp_sk(sk); -- u32 now; -+ u32 count, now; - - /* First check our per-socket dupack rate limit. */ - if (tcp_oow_rate_limited(sock_net(sk), skb, -@@ -3466,13 +3466,18 @@ static void tcp_send_challenge_ack(struct sock *sk, const struct sk_buff *skb) - &tp->last_oow_ack_time)) - return; - -- /* Then check the check host-wide RFC 5961 rate limit. */ -+ /* Then check host-wide RFC 5961 rate limit. */ - now = jiffies / HZ; - if (now != challenge_timestamp) { -+ u32 half = (sysctl_tcp_challenge_ack_limit + 1) >> 1; -+ - challenge_timestamp = now; -- challenge_count = 0; -+ WRITE_ONCE(challenge_count, half + -+ prandom_u32_max(sysctl_tcp_challenge_ack_limit)); - } -- if (++challenge_count <= sysctl_tcp_challenge_ack_limit) { -+ count = READ_ONCE(challenge_count); -+ if (count > 0) { -+ WRITE_ONCE(challenge_count, count - 1); - NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPCHALLENGEACK); - tcp_send_ack(sk); - } --- -2.5.5 - |