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authorEric Dumazet <edumazet@google.com>2019-10-22 07:57:46 -0700
committerDavid S. Miller <davem@davemloft.net>2019-10-23 20:13:22 -0700
commit55667441c84fa5e0911a0aac44fb059c15ba6da2 (patch)
tree83d3fb8a5acbfbb3f9766f30a1e2343f0f19a90b /net/sched/sch_sfb.c
parent6c5d9c2a6bedbb3c3c14253776320c0ee564f064 (diff)
downloadlinux-55667441c84fa5e0911a0aac44fb059c15ba6da2.tar.bz2
net/flow_dissector: switch to siphash
UDP IPv6 packets auto flowlabels are using a 32bit secret (static u32 hashrnd in net/core/flow_dissector.c) and apply jhash() over fields known by the receivers. Attackers can easily infer the 32bit secret and use this information to identify a device and/or user, since this 32bit secret is only set at boot time. Really, using jhash() to generate cookies sent on the wire is a serious security concern. Trying to change the rol32(hash, 16) in ip6_make_flowlabel() would be a dead end. Trying to periodically change the secret (like in sch_sfq.c) could change paths taken in the network for long lived flows. Let's switch to siphash, as we did in commit df453700e8d8 ("inet: switch IP ID generator to siphash") Using a cryptographically strong pseudo random function will solve this privacy issue and more generally remove other weak points in the stack. Packet schedulers using skb_get_hash_perturb() benefit from this change. Fixes: b56774163f99 ("ipv6: Enable auto flow labels by default") Fixes: 42240901f7c4 ("ipv6: Implement different admin modes for automatic flow labels") Fixes: 67800f9b1f4e ("ipv6: Call skb_get_hash_flowi6 to get skb->hash in ip6_make_flowlabel") Fixes: cb1ce2ef387b ("ipv6: Implement automatic flow label generation on transmit") Signed-off-by: Eric Dumazet <edumazet@google.com> Reported-by: Jonathan Berger <jonathann1@walla.com> Reported-by: Amit Klein <aksecurity@gmail.com> Reported-by: Benny Pinkas <benny@pinkas.net> Cc: Tom Herbert <tom@herbertland.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/sched/sch_sfb.c')
-rw-r--r--net/sched/sch_sfb.c13
1 files changed, 7 insertions, 6 deletions
diff --git a/net/sched/sch_sfb.c b/net/sched/sch_sfb.c
index d448fe3068e5..4074c50ac3d7 100644
--- a/net/sched/sch_sfb.c
+++ b/net/sched/sch_sfb.c
@@ -18,7 +18,7 @@
#include <linux/errno.h>
#include <linux/skbuff.h>
#include <linux/random.h>
-#include <linux/jhash.h>
+#include <linux/siphash.h>
#include <net/ip.h>
#include <net/pkt_sched.h>
#include <net/pkt_cls.h>
@@ -45,7 +45,7 @@ struct sfb_bucket {
* (Section 4.4 of SFB reference : moving hash functions)
*/
struct sfb_bins {
- u32 perturbation; /* jhash perturbation */
+ siphash_key_t perturbation; /* siphash key */
struct sfb_bucket bins[SFB_LEVELS][SFB_NUMBUCKETS];
};
@@ -217,7 +217,8 @@ static u32 sfb_compute_qlen(u32 *prob_r, u32 *avgpm_r, const struct sfb_sched_da
static void sfb_init_perturbation(u32 slot, struct sfb_sched_data *q)
{
- q->bins[slot].perturbation = prandom_u32();
+ get_random_bytes(&q->bins[slot].perturbation,
+ sizeof(q->bins[slot].perturbation));
}
static void sfb_swap_slot(struct sfb_sched_data *q)
@@ -314,9 +315,9 @@ static int sfb_enqueue(struct sk_buff *skb, struct Qdisc *sch,
/* If using external classifiers, get result and record it. */
if (!sfb_classify(skb, fl, &ret, &salt))
goto other_drop;
- sfbhash = jhash_1word(salt, q->bins[slot].perturbation);
+ sfbhash = siphash_1u32(salt, &q->bins[slot].perturbation);
} else {
- sfbhash = skb_get_hash_perturb(skb, q->bins[slot].perturbation);
+ sfbhash = skb_get_hash_perturb(skb, &q->bins[slot].perturbation);
}
@@ -352,7 +353,7 @@ static int sfb_enqueue(struct sk_buff *skb, struct Qdisc *sch,
/* Inelastic flow */
if (q->double_buffering) {
sfbhash = skb_get_hash_perturb(skb,
- q->bins[slot].perturbation);
+ &q->bins[slot].perturbation);
if (!sfbhash)
sfbhash = 1;
sfb_skb_cb(skb)->hashes[slot] = sfbhash;