diff options
author | Eric Dumazet <edumazet@google.com> | 2019-10-22 07:57:46 -0700 |
---|---|---|
committer | David S. Miller <davem@davemloft.net> | 2019-10-23 20:13:22 -0700 |
commit | 55667441c84fa5e0911a0aac44fb059c15ba6da2 (patch) | |
tree | 83d3fb8a5acbfbb3f9766f30a1e2343f0f19a90b /net/sched/sch_sfb.c | |
parent | 6c5d9c2a6bedbb3c3c14253776320c0ee564f064 (diff) |
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.c | 13 |
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; |