linux-stable/include/linux/siphash.h
Jason A. Donenfeld 1ae2324f73 siphash: implement HalfSipHash1-3 for hash tables
HalfSipHash, or hsiphash, is a shortened version of SipHash, which
generates 32-bit outputs using a weaker 64-bit key. It has *much* lower
security margins, and shouldn't be used for anything too sensitive, but
it could be used as a hashtable key function replacement, if the output
is never exposed, and if the security requirement is not too high.

The goal is to make this something that performance-critical jhash users
would be willing to use.

On 64-bit machines, HalfSipHash1-3 is slower than SipHash1-3, so we alias
SipHash1-3 to HalfSipHash1-3 on those systems.

64-bit x86_64:
[    0.509409] test_siphash:     SipHash2-4 cycles: 4049181
[    0.510650] test_siphash:     SipHash1-3 cycles: 2512884
[    0.512205] test_siphash: HalfSipHash1-3 cycles: 3429920
[    0.512904] test_siphash:    JenkinsHash cycles:  978267
So, we map hsiphash() -> SipHash1-3

32-bit x86:
[    0.509868] test_siphash:     SipHash2-4 cycles: 14812892
[    0.513601] test_siphash:     SipHash1-3 cycles:  9510710
[    0.515263] test_siphash: HalfSipHash1-3 cycles:  3856157
[    0.515952] test_siphash:    JenkinsHash cycles:  1148567
So, we map hsiphash() -> HalfSipHash1-3

hsiphash() is roughly 3 times slower than jhash(), but comes with a
considerable security improvement.

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Reviewed-by: Jean-Philippe Aumasson <jeanphilippe.aumasson@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2017-01-09 13:58:57 -05:00

140 lines
4.5 KiB
C

/* Copyright (C) 2016 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
*
* This file is provided under a dual BSD/GPLv2 license.
*
* SipHash: a fast short-input PRF
* https://131002.net/siphash/
*
* This implementation is specifically for SipHash2-4 for a secure PRF
* and HalfSipHash1-3/SipHash1-3 for an insecure PRF only suitable for
* hashtables.
*/
#ifndef _LINUX_SIPHASH_H
#define _LINUX_SIPHASH_H
#include <linux/types.h>
#include <linux/kernel.h>
#define SIPHASH_ALIGNMENT __alignof__(u64)
typedef struct {
u64 key[2];
} siphash_key_t;
u64 __siphash_aligned(const void *data, size_t len, const siphash_key_t *key);
#ifndef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
u64 __siphash_unaligned(const void *data, size_t len, const siphash_key_t *key);
#endif
u64 siphash_1u64(const u64 a, const siphash_key_t *key);
u64 siphash_2u64(const u64 a, const u64 b, const siphash_key_t *key);
u64 siphash_3u64(const u64 a, const u64 b, const u64 c,
const siphash_key_t *key);
u64 siphash_4u64(const u64 a, const u64 b, const u64 c, const u64 d,
const siphash_key_t *key);
u64 siphash_1u32(const u32 a, const siphash_key_t *key);
u64 siphash_3u32(const u32 a, const u32 b, const u32 c,
const siphash_key_t *key);
static inline u64 siphash_2u32(const u32 a, const u32 b,
const siphash_key_t *key)
{
return siphash_1u64((u64)b << 32 | a, key);
}
static inline u64 siphash_4u32(const u32 a, const u32 b, const u32 c,
const u32 d, const siphash_key_t *key)
{
return siphash_2u64((u64)b << 32 | a, (u64)d << 32 | c, key);
}
static inline u64 ___siphash_aligned(const __le64 *data, size_t len,
const siphash_key_t *key)
{
if (__builtin_constant_p(len) && len == 4)
return siphash_1u32(le32_to_cpup((const __le32 *)data), key);
if (__builtin_constant_p(len) && len == 8)
return siphash_1u64(le64_to_cpu(data[0]), key);
if (__builtin_constant_p(len) && len == 16)
return siphash_2u64(le64_to_cpu(data[0]), le64_to_cpu(data[1]),
key);
if (__builtin_constant_p(len) && len == 24)
return siphash_3u64(le64_to_cpu(data[0]), le64_to_cpu(data[1]),
le64_to_cpu(data[2]), key);
if (__builtin_constant_p(len) && len == 32)
return siphash_4u64(le64_to_cpu(data[0]), le64_to_cpu(data[1]),
le64_to_cpu(data[2]), le64_to_cpu(data[3]),
key);
return __siphash_aligned(data, len, key);
}
/**
* siphash - compute 64-bit siphash PRF value
* @data: buffer to hash
* @size: size of @data
* @key: the siphash key
*/
static inline u64 siphash(const void *data, size_t len,
const siphash_key_t *key)
{
#ifndef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
if (!IS_ALIGNED((unsigned long)data, SIPHASH_ALIGNMENT))
return __siphash_unaligned(data, len, key);
#endif
return ___siphash_aligned(data, len, key);
}
#define HSIPHASH_ALIGNMENT __alignof__(unsigned long)
typedef struct {
unsigned long key[2];
} hsiphash_key_t;
u32 __hsiphash_aligned(const void *data, size_t len,
const hsiphash_key_t *key);
#ifndef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
u32 __hsiphash_unaligned(const void *data, size_t len,
const hsiphash_key_t *key);
#endif
u32 hsiphash_1u32(const u32 a, const hsiphash_key_t *key);
u32 hsiphash_2u32(const u32 a, const u32 b, const hsiphash_key_t *key);
u32 hsiphash_3u32(const u32 a, const u32 b, const u32 c,
const hsiphash_key_t *key);
u32 hsiphash_4u32(const u32 a, const u32 b, const u32 c, const u32 d,
const hsiphash_key_t *key);
static inline u32 ___hsiphash_aligned(const __le32 *data, size_t len,
const hsiphash_key_t *key)
{
if (__builtin_constant_p(len) && len == 4)
return hsiphash_1u32(le32_to_cpu(data[0]), key);
if (__builtin_constant_p(len) && len == 8)
return hsiphash_2u32(le32_to_cpu(data[0]), le32_to_cpu(data[1]),
key);
if (__builtin_constant_p(len) && len == 12)
return hsiphash_3u32(le32_to_cpu(data[0]), le32_to_cpu(data[1]),
le32_to_cpu(data[2]), key);
if (__builtin_constant_p(len) && len == 16)
return hsiphash_4u32(le32_to_cpu(data[0]), le32_to_cpu(data[1]),
le32_to_cpu(data[2]), le32_to_cpu(data[3]),
key);
return __hsiphash_aligned(data, len, key);
}
/**
* hsiphash - compute 32-bit hsiphash PRF value
* @data: buffer to hash
* @size: size of @data
* @key: the hsiphash key
*/
static inline u32 hsiphash(const void *data, size_t len,
const hsiphash_key_t *key)
{
#ifndef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
if (!IS_ALIGNED((unsigned long)data, HSIPHASH_ALIGNMENT))
return __hsiphash_unaligned(data, len, key);
#endif
return ___hsiphash_aligned(data, len, key);
}
#endif /* _LINUX_SIPHASH_H */