1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
|
From df6369cb69d03c30b299a8a2e3dbeab2261562f9 Mon Sep 17 00:00:00 2001
From: Eric Dumazet <edumazet@google.com>
Date: Thu, 15 Oct 2020 11:42:00 -0700
Subject: [PATCH] icmp: randomize the global rate limiter
[ Upstream commit b38e7819cae946e2edf869e604af1e65a5d241c5 ]
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>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/ipv4/icmp.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/net/ipv4/icmp.c b/net/ipv4/icmp.c
index ac95ba78b903..76cacbe39a21 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);
--
2.17.1
|
