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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
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')
-rw-r--r--net/core/flow_dissector.c38
-rw-r--r--net/sched/sch_hhf.c8
-rw-r--r--net/sched/sch_sfb.c13
-rw-r--r--net/sched/sch_sfq.c14
4 files changed, 35 insertions, 38 deletions
diff --git a/net/core/flow_dissector.c b/net/core/flow_dissector.c
index 7c09d87d3269..68eda10d0680 100644
--- a/net/core/flow_dissector.c
+++ b/net/core/flow_dissector.c
@@ -1350,30 +1350,21 @@ out_bad:
}
EXPORT_SYMBOL(__skb_flow_dissect);
-static u32 hashrnd __read_mostly;
+static siphash_key_t hashrnd __read_mostly;
static __always_inline void __flow_hash_secret_init(void)
{
net_get_random_once(&hashrnd, sizeof(hashrnd));
}
-static __always_inline u32 __flow_hash_words(const u32 *words, u32 length,
- u32 keyval)
+static const void *flow_keys_hash_start(const struct flow_keys *flow)
{
- return jhash2(words, length, keyval);
-}
-
-static inline const u32 *flow_keys_hash_start(const struct flow_keys *flow)
-{
- const void *p = flow;
-
- BUILD_BUG_ON(FLOW_KEYS_HASH_OFFSET % sizeof(u32));
- return (const u32 *)(p + FLOW_KEYS_HASH_OFFSET);
+ BUILD_BUG_ON(FLOW_KEYS_HASH_OFFSET % SIPHASH_ALIGNMENT);
+ return &flow->FLOW_KEYS_HASH_START_FIELD;
}
static inline size_t flow_keys_hash_length(const struct flow_keys *flow)
{
size_t diff = FLOW_KEYS_HASH_OFFSET + sizeof(flow->addrs);
- BUILD_BUG_ON((sizeof(*flow) - FLOW_KEYS_HASH_OFFSET) % sizeof(u32));
BUILD_BUG_ON(offsetof(typeof(*flow), addrs) !=
sizeof(*flow) - sizeof(flow->addrs));
@@ -1388,7 +1379,7 @@ static inline size_t flow_keys_hash_length(const struct flow_keys *flow)
diff -= sizeof(flow->addrs.tipckey);
break;
}
- return (sizeof(*flow) - diff) / sizeof(u32);
+ return sizeof(*flow) - diff;
}
__be32 flow_get_u32_src(const struct flow_keys *flow)
@@ -1454,14 +1445,15 @@ static inline void __flow_hash_consistentify(struct flow_keys *keys)
}
}
-static inline u32 __flow_hash_from_keys(struct flow_keys *keys, u32 keyval)
+static inline u32 __flow_hash_from_keys(struct flow_keys *keys,
+ const siphash_key_t *keyval)
{
u32 hash;
__flow_hash_consistentify(keys);
- hash = __flow_hash_words(flow_keys_hash_start(keys),
- flow_keys_hash_length(keys), keyval);
+ hash = siphash(flow_keys_hash_start(keys),
+ flow_keys_hash_length(keys), keyval);
if (!hash)
hash = 1;
@@ -1471,12 +1463,13 @@ static inline u32 __flow_hash_from_keys(struct flow_keys *keys, u32 keyval)
u32 flow_hash_from_keys(struct flow_keys *keys)
{
__flow_hash_secret_init();
- return __flow_hash_from_keys(keys, hashrnd);
+ return __flow_hash_from_keys(keys, &hashrnd);
}
EXPORT_SYMBOL(flow_hash_from_keys);
static inline u32 ___skb_get_hash(const struct sk_buff *skb,
- struct flow_keys *keys, u32 keyval)
+ struct flow_keys *keys,
+ const siphash_key_t *keyval)
{
skb_flow_dissect_flow_keys(skb, keys,
FLOW_DISSECTOR_F_STOP_AT_FLOW_LABEL);
@@ -1524,7 +1517,7 @@ u32 __skb_get_hash_symmetric(const struct sk_buff *skb)
&keys, NULL, 0, 0, 0,
FLOW_DISSECTOR_F_STOP_AT_FLOW_LABEL);
- return __flow_hash_from_keys(&keys, hashrnd);
+ return __flow_hash_from_keys(&keys, &hashrnd);
}
EXPORT_SYMBOL_GPL(__skb_get_hash_symmetric);
@@ -1544,13 +1537,14 @@ void __skb_get_hash(struct sk_buff *skb)
__flow_hash_secret_init();
- hash = ___skb_get_hash(skb, &keys, hashrnd);
+ hash = ___skb_get_hash(skb, &keys, &hashrnd);
__skb_set_sw_hash(skb, hash, flow_keys_have_l4(&keys));
}
EXPORT_SYMBOL(__skb_get_hash);
-__u32 skb_get_hash_perturb(const struct sk_buff *skb, u32 perturb)
+__u32 skb_get_hash_perturb(const struct sk_buff *skb,
+ const siphash_key_t *perturb)
{
struct flow_keys keys;
diff --git a/net/sched/sch_hhf.c b/net/sched/sch_hhf.c
index 23cd1c873a2c..be35f03b657b 100644
--- a/net/sched/sch_hhf.c
+++ b/net/sched/sch_hhf.c
@@ -5,11 +5,11 @@
* Copyright (C) 2013 Nandita Dukkipati <nanditad@google.com>
*/
-#include <linux/jhash.h>
#include <linux/jiffies.h>
#include <linux/module.h>
#include <linux/skbuff.h>
#include <linux/vmalloc.h>
+#include <linux/siphash.h>
#include <net/pkt_sched.h>
#include <net/sock.h>
@@ -126,7 +126,7 @@ struct wdrr_bucket {
struct hhf_sched_data {
struct wdrr_bucket buckets[WDRR_BUCKET_CNT];
- u32 perturbation; /* hash perturbation */
+ siphash_key_t perturbation; /* hash perturbation */
u32 quantum; /* psched_mtu(qdisc_dev(sch)); */
u32 drop_overlimit; /* number of times max qdisc packet
* limit was hit
@@ -264,7 +264,7 @@ static enum wdrr_bucket_idx hhf_classify(struct sk_buff *skb, struct Qdisc *sch)
}
/* Get hashed flow-id of the skb. */
- hash = skb_get_hash_perturb(skb, q->perturbation);
+ hash = skb_get_hash_perturb(skb, &q->perturbation);
/* Check if this packet belongs to an already established HH flow. */
flow_pos = hash & HHF_BIT_MASK;
@@ -582,7 +582,7 @@ static int hhf_init(struct Qdisc *sch, struct nlattr *opt,
sch->limit = 1000;
q->quantum = psched_mtu(qdisc_dev(sch));
- q->perturbation = prandom_u32();
+ get_random_bytes(&q->perturbation, sizeof(q->perturbation));
INIT_LIST_HEAD(&q->new_buckets);
INIT_LIST_HEAD(&q->old_buckets);
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;
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);