secure_seq: use SipHash in place of MD5

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>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/core/secure_seq.c b/net/core/secure_seq.c
index 88a8e429fc3e6d5779a5fa989dfecb330acb1cbe..3a9fcec94ace21238c0d6cd6d9997678e0623ab9 100644 (file)
--- 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 __read_mostly;
 
 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);