| Message ID | 20201015184200.2179938-1-eric.dumazet@gmail.com |
|---|---|
| State | New |
| Headers | show |
| Series | [net] icmp: randomize the global rate limiter | expand |
On Thu, 15 Oct 2020 11:42:00 -0700 Eric Dumazet wrote: > From: Eric Dumazet <edumazet@google.com> > > Keyu Man reported that the ICMP rate limiter could be used > by attackers to get useful signal. Details will be provided > in an upcoming academic publication. > > Our solution is to add some noise, so that the attackers > no longer can get help from the predictable token bucket limiter. > > Fixes: 4cdf507d5452 ("icmp: add a global rate limitation") > Signed-off-by: Eric Dumazet <edumazet@google.com> > Reported-by: Keyu Man <kman001@ucr.edu> Applied, queued up, thank you!
Hello: This patch was applied to netdev/net.git (refs/heads/master): On Thu, 15 Oct 2020 11:42:00 -0700 you wrote: > From: Eric Dumazet <edumazet@google.com> > > Keyu Man reported that the ICMP rate limiter could be used > by attackers to get useful signal. Details will be provided > in an upcoming academic publication. > > Our solution is to add some noise, so that the attackers > no longer can get help from the predictable token bucket limiter. > > [...] Here is the summary with links: - [net] icmp: randomize the global rate limiter https://git.kernel.org/netdev/net/c/b38e7819cae9 You are awesome, thank you! -- Deet-doot-dot, I am a bot. https://korg.docs.kernel.org/patchwork/pwbot.html
diff --git a/Documentation/networking/ip-sysctl.rst b/Documentation/networking/ip-sysctl.rst index 837d51f9e1fab7c0999a51184f95971fb43c1b9b..25e6673a085a0f55f1f23bd3974e806ed2706f68 100644 --- a/Documentation/networking/ip-sysctl.rst +++ b/Documentation/networking/ip-sysctl.rst @@ -1142,13 +1142,15 @@ icmp_ratelimit - INTEGER icmp_msgs_per_sec - INTEGER Limit maximal number of ICMP packets sent per second from this host. Only messages whose type matches icmp_ratemask (see below) are - controlled by this limit. + controlled by this limit. For security reasons, the precise count + of messages per second is randomized. Default: 1000 icmp_msgs_burst - INTEGER icmp_msgs_per_sec controls number of ICMP packets sent per second, while icmp_msgs_burst controls the burst size of these packets. + For security reasons, the precise burst size is randomized. Default: 50 diff --git a/net/ipv4/icmp.c b/net/ipv4/icmp.c index 9ea66d903c41f560093b5cf21814b494c71f669b..1e8fd77d85037f8c7b5a64fc54630ccffc3a48b1 100644 --- a/net/ipv4/icmp.c +++ b/net/ipv4/icmp.c @@ -239,7 +239,7 @@ static struct { /** * icmp_global_allow - Are we allowed to send one more ICMP message ? * - * Uses a token bucket to limit our ICMP messages to sysctl_icmp_msgs_per_sec. + * Uses a token bucket to limit our ICMP messages to ~sysctl_icmp_msgs_per_sec. * Returns false if we reached the limit and can not send another packet. * Note: called with BH disabled */ @@ -267,7 +267,10 @@ bool icmp_global_allow(void) } credit = min_t(u32, icmp_global.credit + incr, sysctl_icmp_msgs_burst); if (credit) { - credit--; + /* We want to use a credit of one in average, but need to randomize + * it for security reasons. + */ + credit = max_t(int, credit - prandom_u32_max(3), 0); rc = true; } WRITE_ONCE(icmp_global.credit, credit);