From: Eric Dumazet edumazet@google.com
commit 55667441c84fa5e0911a0aac44fb059c15ba6da2 upstream.
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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- include/linux/skbuff.h | 3 ++- include/net/flow_dissector.h | 3 ++- include/net/fq.h | 2 +- include/net/fq_impl.h | 4 ++-- net/core/flow_dissector.c | 38 ++++++++++++++++---------------------- net/sched/sch_hhf.c | 8 ++++---- net/sched/sch_sfb.c | 13 +++++++------ net/sched/sch_sfq.c | 14 ++++++++------ 8 files changed, 42 insertions(+), 43 deletions(-)
--- a/include/linux/skbuff.h +++ b/include/linux/skbuff.h @@ -1360,7 +1360,8 @@ static inline __u32 skb_get_hash_flowi6( return skb->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);
static inline __u32 skb_get_hash_raw(const struct sk_buff *skb) { --- a/include/net/flow_dissector.h +++ b/include/net/flow_dissector.h @@ -4,6 +4,7 @@
#include <linux/types.h> #include <linux/in6.h> +#include <linux/siphash.h> #include <uapi/linux/if_ether.h>
/** @@ -276,7 +277,7 @@ struct flow_keys_basic { struct flow_keys { struct flow_dissector_key_control control; #define FLOW_KEYS_HASH_START_FIELD basic - struct flow_dissector_key_basic basic; + struct flow_dissector_key_basic basic __aligned(SIPHASH_ALIGNMENT); struct flow_dissector_key_tags tags; struct flow_dissector_key_vlan vlan; struct flow_dissector_key_vlan cvlan; --- a/include/net/fq.h +++ b/include/net/fq.h @@ -69,7 +69,7 @@ struct fq { struct list_head backlogs; spinlock_t lock; u32 flows_cnt; - u32 perturbation; + siphash_key_t perturbation; u32 limit; u32 memory_limit; u32 memory_usage; --- a/include/net/fq_impl.h +++ b/include/net/fq_impl.h @@ -108,7 +108,7 @@ begin:
static u32 fq_flow_idx(struct fq *fq, struct sk_buff *skb) { - u32 hash = skb_get_hash_perturb(skb, fq->perturbation); + u32 hash = skb_get_hash_perturb(skb, &fq->perturbation);
return reciprocal_scale(hash, fq->flows_cnt); } @@ -308,7 +308,7 @@ static int fq_init(struct fq *fq, int fl INIT_LIST_HEAD(&fq->backlogs); spin_lock_init(&fq->lock); fq->flows_cnt = max_t(u32, flows_cnt, 1); - fq->perturbation = prandom_u32(); + get_random_bytes(&fq->perturbation, sizeof(fq->perturbation)); fq->quantum = 300; fq->limit = 8192; fq->memory_limit = 16 << 20; /* 16 MBytes */ --- a/net/core/flow_dissector.c +++ b/net/core/flow_dissector.c @@ -1333,30 +1333,21 @@ 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));
@@ -1371,7 +1362,7 @@ static inline size_t flow_keys_hash_leng 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) @@ -1437,14 +1428,15 @@ static inline void __flow_hash_consisten } }
-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;
@@ -1454,12 +1446,13 @@ static inline u32 __flow_hash_from_keys( 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); @@ -1507,7 +1500,7 @@ u32 __skb_get_hash_symmetric(const struc &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);
@@ -1527,13 +1520,14 @@ 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;
--- 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 }
/* 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, s
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);
--- 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,
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 *s /* 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 *s /* 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; --- 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_h 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 time 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, 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, s 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);