X-Git-Url: http://git.openwrt.org/?a=blobdiff_plain;f=target%2Flinux%2Fgeneric%2Fpatches-4.4%2F096-tcp-make-challenge-acks-less-predictable.patch;fp=target%2Flinux%2Fgeneric%2Fpatches-4.4%2F096-tcp-make-challenge-acks-less-predictable.patch;h=0000000000000000000000000000000000000000;hb=8072264b96785184b76aa46bcd08b4f9cdfada42;hp=a783c6ebbce84dbc202e962ece8df7c0a147d17c;hpb=861f566e340dcf5fedd52c0ff3b31501fd3b3f1b;p=openwrt%2Fopenwrt.git diff --git a/target/linux/generic/patches-4.4/096-tcp-make-challenge-acks-less-predictable.patch b/target/linux/generic/patches-4.4/096-tcp-make-challenge-acks-less-predictable.patch deleted file mode 100644 index a783c6ebbc..0000000000 --- a/target/linux/generic/patches-4.4/096-tcp-make-challenge-acks-less-predictable.patch +++ /dev/null @@ -1,76 +0,0 @@ -From 75ff39ccc1bd5d3c455b6822ab09e533c551f758 Mon Sep 17 00:00:00 2001 -From: Eric Dumazet -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 -Signed-off-by: Eric Dumazet -Suggested-by: Linus Torvalds -Cc: Yuchung Cheng -Cc: Neal Cardwell -Acked-by: Neal Cardwell -Acked-by: Yuchung Cheng -Signed-off-by: David S. Miller ---- - net/ipv4/tcp_input.c | 15 ++++++++++----- - 1 file changed, 10 insertions(+), 5 deletions(-) - ---- a/net/ipv4/tcp_input.c -+++ b/net/ipv4/tcp_input.c -@@ -89,7 +89,7 @@ int sysctl_tcp_adv_win_scale __read_most - 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; -@@ -3427,7 +3427,7 @@ static void tcp_send_challenge_ack(struc - 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, -@@ -3435,13 +3435,18 @@ static void tcp_send_challenge_ack(struc - &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_BH(sock_net(sk), LINUX_MIB_TCPCHALLENGEACK); - tcp_send_ack(sk); - }