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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_sfq.c
parent6c5d9c2a6bedbb3c3c14253776320c0ee564f064 (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_sfq.c')
-rw-r--r--net/sched/sch_sfq.c14
1 files changed, 8 insertions, 6 deletions
diff --git a/net/sched/sch_sfq.c b/net/sched/sch_sfq.c
index 68404a9d2ce4..c787d4d46017 100644
--- a/net/sched/sch_sfq.c
+++ b/net/sched/sch_sfq.c
@@ -14,7 +14,7 @@
#include <linux/errno.h>
#include <linux/init.h>
#include <linux/skbuff.h>
-#include <linux/jhash.h>
+#include <linux/siphash.h>
#include <linux/slab.h>
#include <linux/vmalloc.h>
#include <net/netlink.h>
@@ -117,7 +117,7 @@ struct sfq_sched_data {
u8 headdrop;
u8 maxdepth; /* limit of packets per flow */
- u32 perturbation;
+ siphash_key_t perturbation;
u8 cur_depth; /* depth of longest slot */
u8 flags;
unsigned short scaled_quantum; /* SFQ_ALLOT_SIZE(quantum) */
@@ -157,7 +157,7 @@ static inline struct sfq_head *sfq_dep_head(struct sfq_sched_data *q, sfq_index
static unsigned int sfq_hash(const struct sfq_sched_data *q,
const struct sk_buff *skb)
{
- return skb_get_hash_perturb(skb, q->perturbation) & (q->divisor - 1);
+ return skb_get_hash_perturb(skb, &q->perturbation) & (q->divisor - 1);
}
static unsigned int sfq_classify(struct sk_buff *skb, struct Qdisc *sch,
@@ -607,9 +607,11 @@ static void sfq_perturbation(struct timer_list *t)
struct sfq_sched_data *q = from_timer(q, t, perturb_timer);
struct Qdisc *sch = q->sch;
spinlock_t *root_lock = qdisc_lock(qdisc_root_sleeping(sch));
+ siphash_key_t nkey;
+ get_random_bytes(&nkey, sizeof(nkey));
spin_lock(root_lock);
- q->perturbation = prandom_u32();
+ q->perturbation = nkey;
if (!q->filter_list && q->tail)
sfq_rehash(sch);
spin_unlock(root_lock);
@@ -688,7 +690,7 @@ static int sfq_change(struct Qdisc *sch, struct nlattr *opt)
del_timer(&q->perturb_timer);
if (q->perturb_period) {
mod_timer(&q->perturb_timer, jiffies + q->perturb_period);
- q->perturbation = prandom_u32();
+ get_random_bytes(&q->perturbation, sizeof(q->perturbation));
}
sch_tree_unlock(sch);
kfree(p);
@@ -745,7 +747,7 @@ static int sfq_init(struct Qdisc *sch, struct nlattr *opt,
q->quantum = psched_mtu(qdisc_dev(sch));
q->scaled_quantum = SFQ_ALLOT_SIZE(q->quantum);
q->perturb_period = 0;
- q->perturbation = prandom_u32();
+ get_random_bytes(&q->perturbation, sizeof(q->perturbation));
if (opt) {
int err = sfq_change(sch, opt);