[PATCH v2 net-next 3/4] secure_seq: use SipHash in place of MD5

Jason A. Donenfeld
2017-01-07T14:42:14Z

This gives a clear speed and security improvement. Siphash is both
faster and is more solid crypto than the aging MD5.

Rather than manually filling MD5 buffers, for IPv6, we simply create
a layout by a simple anonymous struct, for which gcc generates
rather efficient code. For IPv4, we pass the values directly to the
short input convenience functions.

64-bit x86_64:
[ 1.683628] secure_tcpv6_sequence_number_md5# cycles: 99563527
[ 1.717350] secure_tcp_sequence_number_md5# cycles: 92890502
[ 1.741968] secure_tcpv6_sequence_number_siphash# cycles: 67825362
[ 1.762048] secure_tcp_sequence_number_siphash# cycles: 67485526

32-bit x86:
[ 1.600012] secure_tcpv6_sequence_number_md5# cycles: 103227892
[ 1.634219] secure_tcp_sequence_number_md5# cycles: 94732544
[ 1.669102] secure_tcpv6_sequence_number_siphash# cycles: 96299384
[ 1.700165] secure_tcp_sequence_number_siphash# cycles: 86015473

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: David Miller <davem@davemloft.net>
Cc: David Laight <David.Laight@aculab.com>
Cc: Tom Herbert <tom@herbertland.com>
Cc: Hannes Frederic Sowa <hannes@stressinduktion.org>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
---
net/core/secure_seq.c | 145 ++++++++++++++++++++++----------------------------
1 file changed, 63 insertions(+), 82 deletions(-)

diff --git a/net/core/secure_seq.c b/net/core/secure_seq.c
index 88a8e429fc3e..119e3ebe2f30 100644
--- a/net/core/secure_seq.c
+++ b/net/core/secure_seq.c
@@ -1,3 +1,7 @@
+/*
+ * Copyright (C) 2016 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
+ */
+
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/cryptohash.h>
@@ -8,18 +12,18 @@
#include <linux/ktime.h>
#include <linux/string.h>
#include <linux/net.h>
-
+#include <linux/siphash.h>
#include <net/secure_seq.h>

#if IS_ENABLED(CONFIG_IPV6) || IS_ENABLED(CONFIG_INET)
+#include <linux/in6.h>
#include <net/tcp.h>
-#define NET_SECRET_SIZE (MD5_MESSAGE_BYTES / 4)

-static u32 net_secret[NET_SECRET_SIZE] ____cacheline_aligned;
+static siphash_key_t net_secret;

static __always_inline void net_secret_init(void)
{
- net_get_random_once(net_secret, sizeof(net_secret));
+ net_get_random_once(&net_secret, sizeof(net_secret));
}
#endif

@@ -44,80 +48,70 @@ static u32 seq_scale(u32 seq)
u32 secure_tcpv6_sequence_number(const __be32 *saddr, const __be32 *daddr,
__be16 sport, __be16 dport, u32 *tsoff)
{
- u32 secret[MD5_MESSAGE_BYTES / 4];
- u32 hash[MD5_DIGEST_WORDS];
- u32 i;
-
+ const struct {
+ struct in6_addr saddr;
+ struct in6_addr daddr;
+ __be16 sport;
+ __be16 dport;
+ } __aligned(SIPHASH_ALIGNMENT) combined = {
+ .saddr = *(struct in6_addr *)saddr,
+ .daddr = *(struct in6_addr *)daddr,
+ .sport = sport,
+ .dport = dport
+ };
+ u64 hash;
net_secret_init();
- memcpy(hash, saddr, 16);
- for (i = 0; i < 4; i++)
- secret[i] = net_secret[i] + (__force u32)daddr[i];
- secret[4] = net_secret[4] +
- (((__force u16)sport << 16) + (__force u16)dport);
- for (i = 5; i < MD5_MESSAGE_BYTES / 4; i++)
- secret[i] = net_secret[i];
-
- md5_transform(hash, secret);
-
- *tsoff = sysctl_tcp_timestamps == 1 ? hash[1] : 0;
- return seq_scale(hash[0]);
+ hash = siphash(&combined, offsetofend(typeof(combined), dport),
+ &net_secret);
+ *tsoff = sysctl_tcp_timestamps == 1 ? (hash >> 32) : 0;
+ return seq_scale(hash);
}
EXPORT_SYMBOL(secure_tcpv6_sequence_number);

u32 secure_ipv6_port_ephemeral(const __be32 *saddr, const __be32 *daddr,
__be16 dport)
{
- u32 secret[MD5_MESSAGE_BYTES / 4];
- u32 hash[MD5_DIGEST_WORDS];
- u32 i;
-
+ const struct {
+ struct in6_addr saddr;
+ struct in6_addr daddr;
+ __be16 dport;
+ } __aligned(SIPHASH_ALIGNMENT) combined = {
+ .saddr = *(struct in6_addr *)saddr,
+ .daddr = *(struct in6_addr *)daddr,
+ .dport = dport
+ };
net_secret_init();
- memcpy(hash, saddr, 16);
- for (i = 0; i < 4; i++)
- secret[i] = net_secret[i] + (__force u32) daddr[i];
- secret[4] = net_secret[4] + (__force u32)dport;
- for (i = 5; i < MD5_MESSAGE_BYTES / 4; i++)
- secret[i] = net_secret[i];
-
- md5_transform(hash, secret);
-
- return hash[0];
+ return siphash(&combined, offsetofend(typeof(combined), dport),
+ &net_secret);
}
EXPORT_SYMBOL(secure_ipv6_port_ephemeral);
#endif

#ifdef CONFIG_INET

+/* secure_tcp_sequence_number(a, b, 0, d) == secure_ipv4_port_ephemeral(a, b, d),
+ * but fortunately, `sport' cannot be 0 in any circumstances. If this changes,
+ * it would be easy enough to have the former function use siphash_4u32, passing
+ * the arguments as separate u32.
+ */
+
u32 secure_tcp_sequence_number(__be32 saddr, __be32 daddr,
__be16 sport, __be16 dport, u32 *tsoff)
{
- u32 hash[MD5_DIGEST_WORDS];
-
+ u64 hash;
net_secret_init();
- hash[0] = (__force u32)saddr;
- hash[1] = (__force u32)daddr;
- hash[2] = ((__force u16)sport << 16) + (__force u16)dport;
- hash[3] = net_secret[15];
-
- md5_transform(hash, net_secret);
-
- *tsoff = sysctl_tcp_timestamps == 1 ? hash[1] : 0;
- return seq_scale(hash[0]);
+ hash = siphash_3u32((__force u32)saddr, (__force u32)daddr,
+ (__force u32)sport << 16 | (__force u32)dport,
+ &net_secret);
+ *tsoff = sysctl_tcp_timestamps == 1 ? (hash >> 32) : 0;
+ return seq_scale(hash);
}

u32 secure_ipv4_port_ephemeral(__be32 saddr, __be32 daddr, __be16 dport)
{
- u32 hash[MD5_DIGEST_WORDS];
-
net_secret_init();
- hash[0] = (__force u32)saddr;
- hash[1] = (__force u32)daddr;
- hash[2] = (__force u32)dport ^ net_secret[14];
- hash[3] = net_secret[15];
-
- md5_transform(hash, net_secret);
-
- return hash[0];
+ return siphash_3u32((__force u32)saddr, (__force u32)daddr,
+ (__force u16)dport, &net_secret);
}
EXPORT_SYMBOL_GPL(secure_ipv4_port_ephemeral);
#endif
@@ -126,21 +120,11 @@ EXPORT_SYMBOL_GPL(secure_ipv4_port_ephemeral);
u64 secure_dccp_sequence_number(__be32 saddr, __be32 daddr,
__be16 sport, __be16 dport)
{
- u32 hash[MD5_DIGEST_WORDS];
u64 seq;
-
net_secret_init();
- hash[0] = (__force u32)saddr;
- hash[1] = (__force u32)daddr;
- hash[2] = ((__force u16)sport << 16) + (__force u16)dport;
- hash[3] = net_secret[15];
-
- md5_transform(hash, net_secret);
-
- seq = hash[0] | (((u64)hash[1]) << 32);
+ seq = siphash_3u32(saddr, daddr, (u32)sport << 16 | dport, &net_secret);
seq += ktime_get_real_ns();
seq &= (1ull << 48) - 1;
-
return seq;
}
EXPORT_SYMBOL(secure_dccp_sequence_number);
@@ -149,26 +133,23 @@ EXPORT_SYMBOL(secure_dccp_sequence_number);
u64 secure_dccpv6_sequence_number(__be32 *saddr, __be32 *daddr,
__be16 sport, __be16 dport)
{
- u32 secret[MD5_MESSAGE_BYTES / 4];
- u32 hash[MD5_DIGEST_WORDS];
+ const struct {
+ struct in6_addr saddr;
+ struct in6_addr daddr;
+ __be16 sport;
+ __be16 dport;
+ } __aligned(SIPHASH_ALIGNMENT) combined = {
+ .saddr = *(struct in6_addr *)saddr,
+ .daddr = *(struct in6_addr *)daddr,
+ .sport = sport,
+ .dport = dport
+ };
u64 seq;
- u32 i;
-
net_secret_init();
- memcpy(hash, saddr, 16);
- for (i = 0; i < 4; i++)
- secret[i] = net_secret[i] + (__force u32)daddr[i];
- secret[4] = net_secret[4] +
- (((__force u16)sport << 16) + (__force u16)dport);
- for (i = 5; i < MD5_MESSAGE_BYTES / 4; i++)
- secret[i] = net_secret[i];
-
- md5_transform(hash, secret);
-
- seq = hash[0] | (((u64)hash[1]) << 32);
+ seq = siphash(&combined, offsetofend(typeof(combined), dport),
+ &net_secret);
seq += ktime_get_real_ns();
seq &= (1ull << 48) - 1;
-
return seq;
}
EXPORT_SYMBOL(secure_dccpv6_sequence_number);
--
2.11.0