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icmp: use per rate limit randomized jitter

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Using the same random jitter for multiple rate limits allows an
attacker to use one rate limiter to figure out the current jitter
and then use this knowledge to de-randomize the other rate limiters.
This can be mitigated by using a separate randomized jitter for each
rate limiter.
This issue was reported as issue number 10 in Keyu Man et al.:
SCAD: Towards a Universal and Automated Network Side-Channel
Vulnerability Detection

Reviewed by:		rrs, Peter Lei, glebius
Sponsored by:		Netflix, Inc.
Differential Revision:	https://reviews.freebsd.org/D48804
Approved by:		re (cperciva)

(cherry picked from commit 923c223f27)
(cherry picked from commit e1dd07ede9)
This commit is contained in:
Michael Tuexen committed 2025-02-13 15:04:39 +01:00
1 parent 5f2744d520
commit cd91df3292
2 files changed
+39 -31
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sys/netinet/ip_icmp.c
+12 -8
View File
@@ -89,7 +89,7 @@ SYSCTL_PROC(_net_inet_icmp, ICMPCTL_ICMPLIM, icmplim, CTLTYPE_UINT |
&sysctl_icmplim_and_jitter, "IU",
"Maximum number of ICMP responses per second");
VNET_DEFINE_STATIC(int, icmplim_curr_jitter) = 0;
VNET_DEFINE_STATIC(int, icmplim_curr_jitter[BANDLIM_MAX]) = {0};
#define V_icmplim_curr_jitter VNET(icmplim_curr_jitter)
VNET_DEFINE_STATIC(u_int, icmplim_jitter) = 16;
#define V_icmplim_jitter VNET(icmplim_jitter)
@@ -1102,14 +1102,16 @@ static const char *icmp_rate_descrs[BANDLIM_MAX] = {
};
static void
icmplim_new_jitter(void)
icmplim_new_jitter(int which)
{
/*
* Adjust limit +/- to jitter the measurement to deny a side-channel
* port scan as in https://dl.acm.org/doi/10.1145/3372297.3417280
*/
KASSERT(which >= 0 && which < BANDLIM_MAX,
("%s: which %d", __func__, which));
if (V_icmplim_jitter > 0)
V_icmplim_curr_jitter =
V_icmplim_curr_jitter[which] =
arc4random_uniform(V_icmplim_jitter * 2 + 1) -
V_icmplim_jitter;
}
@@ -1138,7 +1140,9 @@ sysctl_icmplim_and_jitter(SYSCTL_HANDLER_ARGS)
error = EINVAL;
else {
V_icmplim_jitter = new;
icmplim_new_jitter();
for (int i = 0; i < BANDLIM_MAX; i++) {
icmplim_new_jitter(i);
}
}
}
}
@@ -1154,8 +1158,8 @@ icmp_bandlimit_init(void)
for (int i = 0; i < BANDLIM_MAX; i++) {
V_icmp_rates[i].cr_rate = counter_u64_alloc(M_WAITOK);
V_icmp_rates[i].cr_ticks = ticks;
icmplim_new_jitter(i);
}
icmplim_new_jitter();
}
VNET_SYSINIT(icmp_bandlimit, SI_SUB_PROTO_DOMAIN, SI_ORDER_ANY,
icmp_bandlimit_init, NULL);
@@ -1184,14 +1188,14 @@ badport_bandlim(int which)
("%s: which %d", __func__, which));
pps = counter_ratecheck(&V_icmp_rates[which], V_icmplim +
V_icmplim_curr_jitter);
V_icmplim_curr_jitter[which]);
if (pps > 0) {
if (V_icmplim_output)
log(LOG_NOTICE,
"Limiting %s response from %jd to %d packets/sec\n",
icmp_rate_descrs[which], (intmax_t )pps,
V_icmplim + V_icmplim_curr_jitter);
icmplim_new_jitter();
V_icmplim + V_icmplim_curr_jitter[which]);
icmplim_new_jitter(which);
}
if (pps == -1)
return (-1);
sys/netinet6/icmp6.c
+27 -23
View File
@@ -2778,22 +2778,6 @@ SYSCTL_PROC(_net_inet6_icmp6, ICMPV6CTL_ERRPPSLIMIT, errppslimit,
&sysctl_icmp6lim_and_jitter, "IU",
"Maximum number of ICMPv6 error/reply messages per second");
VNET_DEFINE_STATIC(int, icmp6lim_curr_jitter) = 0;
#define V_icmp6lim_curr_jitter VNET(icmp6lim_curr_jitter)
VNET_DEFINE_STATIC(u_int, icmp6lim_jitter) = 8;
#define V_icmp6lim_jitter VNET(icmp6lim_jitter)
SYSCTL_PROC(_net_inet6_icmp6, OID_AUTO, icmp6lim_jitter, CTLTYPE_UINT |
CTLFLAG_VNET | CTLFLAG_RW, &VNET_NAME(icmp6lim_jitter), 0,
&sysctl_icmp6lim_and_jitter, "IU",
"Random errppslimit jitter adjustment limit");
VNET_DEFINE_STATIC(int, icmp6lim_output) = 1;
#define V_icmp6lim_output VNET(icmp6lim_output)
SYSCTL_INT(_net_inet6_icmp6, OID_AUTO, icmp6lim_output,
CTLFLAG_VNET | CTLFLAG_RW, &VNET_NAME(icmp6lim_output), 0,
"Enable logging of ICMPv6 response rate limiting");
typedef enum {
RATELIM_PARAM_PROB = 0,
RATELIM_TOO_BIG,
@@ -2815,15 +2799,33 @@ static const char *icmp6_rate_descrs[RATELIM_MAX] = {
[RATELIM_OTHER] = "(other)",
};
VNET_DEFINE_STATIC(int, icmp6lim_curr_jitter[RATELIM_MAX]) = {0};
#define V_icmp6lim_curr_jitter VNET(icmp6lim_curr_jitter)
VNET_DEFINE_STATIC(u_int, icmp6lim_jitter) = 8;
#define V_icmp6lim_jitter VNET(icmp6lim_jitter)
SYSCTL_PROC(_net_inet6_icmp6, OID_AUTO, icmp6lim_jitter, CTLTYPE_UINT |
CTLFLAG_VNET | CTLFLAG_RW, &VNET_NAME(icmp6lim_jitter), 0,
&sysctl_icmp6lim_and_jitter, "IU",
"Random errppslimit jitter adjustment limit");
VNET_DEFINE_STATIC(int, icmp6lim_output) = 1;
#define V_icmp6lim_output VNET(icmp6lim_output)
SYSCTL_INT(_net_inet6_icmp6, OID_AUTO, icmp6lim_output,
CTLFLAG_VNET | CTLFLAG_RW, &VNET_NAME(icmp6lim_output), 0,
"Enable logging of ICMPv6 response rate limiting");
static void
icmp6lim_new_jitter(void)
icmp6lim_new_jitter(int which)
{
/*
* Adjust limit +/- to jitter the measurement to deny a side-channel
* port scan as in https://dl.acm.org/doi/10.1145/3372297.3417280
*/
KASSERT(which >= 0 && which < RATELIM_MAX,
("%s: which %d", __func__, which));
if (V_icmp6lim_jitter > 0)
V_icmp6lim_curr_jitter =
V_icmp6lim_curr_jitter[which] =
arc4random_uniform(V_icmp6lim_jitter * 2 + 1) -
V_icmp6lim_jitter;
}
@@ -2852,7 +2854,9 @@ sysctl_icmp6lim_and_jitter(SYSCTL_HANDLER_ARGS)
error = EINVAL;
else {
V_icmp6lim_jitter = new;
icmp6lim_new_jitter();
for (int i = 0; i < RATELIM_MAX; i++) {
icmp6lim_new_jitter(i);
}
}
}
}
@@ -2872,8 +2876,8 @@ icmp6_ratelimit_init(void)
for (int i = 0; i < RATELIM_MAX; i++) {
V_icmp6_rates[i].cr_rate = counter_u64_alloc(M_WAITOK);
V_icmp6_rates[i].cr_ticks = ticks;
icmp6lim_new_jitter(i);
}
icmp6lim_new_jitter();
}
VNET_SYSINIT(icmp6_ratelimit, SI_SUB_PROTO_DOMAIN, SI_ORDER_ANY,
icmp6_ratelimit_init, NULL);
@@ -2935,14 +2939,14 @@ icmp6_ratelimit(const struct in6_addr *dst, const int type, const int code)
};
pps = counter_ratecheck(&V_icmp6_rates[which], V_icmp6errppslim +
V_icmp6lim_curr_jitter);
V_icmp6lim_curr_jitter[which]);
if (pps > 0) {
if (V_icmp6lim_output)
log(LOG_NOTICE, "Limiting ICMPv6 %s output from %jd "
"to %d packets/sec\n", icmp6_rate_descrs[which],
(intmax_t )pps, V_icmp6errppslim +
V_icmp6lim_curr_jitter);
icmp6lim_new_jitter();
V_icmp6lim_curr_jitter[which]);
icmp6lim_new_jitter(which);
}
if (pps == -1) {
ICMP6STAT_INC(icp6s_toofreq);