net/flow_dissector: switch to siphash
[ Upstream commit 55667441c84fa5e0911a0aac44fb059c15ba6da2 ]
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>
diff --git a/include/net/flow_dissector.h b/include/net/flow_dissector.h
index 6a4586d..4618cbb 100644
--- 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>
/**
@@ -252,7 +253,7 @@
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;
diff --git a/include/net/fq.h b/include/net/fq.h
index ac944a6..c51be50 100644
--- a/include/net/fq.h
+++ b/include/net/fq.h
@@ -70,7 +70,7 @@
struct list_head backlogs;
spinlock_t lock;
u32 flows_cnt;
- u32 perturbation;
+ siphash_key_t perturbation;
u32 limit;
u32 memory_limit;
u32 memory_usage;
diff --git a/include/net/fq_impl.h b/include/net/fq_impl.h
index be7c0fa..89a0129 100644
--- a/include/net/fq_impl.h
+++ b/include/net/fq_impl.h
@@ -118,7 +118,7 @@
lockdep_assert_held(&fq->lock);
- hash = skb_get_hash_perturb(skb, fq->perturbation);
+ hash = skb_get_hash_perturb(skb, &fq->perturbation);
idx = reciprocal_scale(hash, fq->flows_cnt);
flow = &fq->flows[idx];
@@ -307,7 +307,7 @@
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 */