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![Jason A. Donenfeld](/assets/img/avatar_default.png)
The SipHash family of permutations is currently used in three places: - siphash.c itself, used in the ordinary way it was intended. - random32.c, in a construction from an anonymous contributor. - random.c, as part of its fast_mix function. Each one of these places reinvents the wheel with the same C code, same rotation constants, and same symmetry-breaking constants. This commit tidies things up a bit by placing macros for the permutations and constants into siphash.h, where each of the three .c users can access them. It also leaves a note dissuading more users of them from emerging. Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
169 lines
5.6 KiB
C
169 lines
5.6 KiB
C
/* Copyright (C) 2016 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
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*
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* This file is provided under a dual BSD/GPLv2 license.
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*
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* SipHash: a fast short-input PRF
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* https://131002.net/siphash/
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*
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* This implementation is specifically for SipHash2-4 for a secure PRF
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* and HalfSipHash1-3/SipHash1-3 for an insecure PRF only suitable for
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* hashtables.
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*/
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#ifndef _LINUX_SIPHASH_H
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#define _LINUX_SIPHASH_H
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#include <linux/types.h>
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#include <linux/kernel.h>
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#define SIPHASH_ALIGNMENT __alignof__(u64)
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typedef struct {
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u64 key[2];
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} siphash_key_t;
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#define siphash_aligned_key_t siphash_key_t __aligned(16)
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static inline bool siphash_key_is_zero(const siphash_key_t *key)
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{
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return !(key->key[0] | key->key[1]);
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}
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u64 __siphash_aligned(const void *data, size_t len, const siphash_key_t *key);
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u64 __siphash_unaligned(const void *data, size_t len, const siphash_key_t *key);
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u64 siphash_1u64(const u64 a, const siphash_key_t *key);
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u64 siphash_2u64(const u64 a, const u64 b, const siphash_key_t *key);
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u64 siphash_3u64(const u64 a, const u64 b, const u64 c,
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const siphash_key_t *key);
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u64 siphash_4u64(const u64 a, const u64 b, const u64 c, const u64 d,
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const siphash_key_t *key);
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u64 siphash_1u32(const u32 a, const siphash_key_t *key);
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u64 siphash_3u32(const u32 a, const u32 b, const u32 c,
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const siphash_key_t *key);
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static inline u64 siphash_2u32(const u32 a, const u32 b,
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const siphash_key_t *key)
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{
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return siphash_1u64((u64)b << 32 | a, key);
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}
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static inline u64 siphash_4u32(const u32 a, const u32 b, const u32 c,
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const u32 d, const siphash_key_t *key)
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{
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return siphash_2u64((u64)b << 32 | a, (u64)d << 32 | c, key);
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}
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static inline u64 ___siphash_aligned(const __le64 *data, size_t len,
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const siphash_key_t *key)
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{
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if (__builtin_constant_p(len) && len == 4)
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return siphash_1u32(le32_to_cpup((const __le32 *)data), key);
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if (__builtin_constant_p(len) && len == 8)
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return siphash_1u64(le64_to_cpu(data[0]), key);
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if (__builtin_constant_p(len) && len == 16)
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return siphash_2u64(le64_to_cpu(data[0]), le64_to_cpu(data[1]),
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key);
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if (__builtin_constant_p(len) && len == 24)
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return siphash_3u64(le64_to_cpu(data[0]), le64_to_cpu(data[1]),
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le64_to_cpu(data[2]), key);
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if (__builtin_constant_p(len) && len == 32)
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return siphash_4u64(le64_to_cpu(data[0]), le64_to_cpu(data[1]),
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le64_to_cpu(data[2]), le64_to_cpu(data[3]),
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key);
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return __siphash_aligned(data, len, key);
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}
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/**
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* siphash - compute 64-bit siphash PRF value
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* @data: buffer to hash
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* @size: size of @data
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* @key: the siphash key
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*/
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static inline u64 siphash(const void *data, size_t len,
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const siphash_key_t *key)
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{
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if (IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS) ||
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!IS_ALIGNED((unsigned long)data, SIPHASH_ALIGNMENT))
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return __siphash_unaligned(data, len, key);
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return ___siphash_aligned(data, len, key);
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}
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#define HSIPHASH_ALIGNMENT __alignof__(unsigned long)
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typedef struct {
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unsigned long key[2];
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} hsiphash_key_t;
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u32 __hsiphash_aligned(const void *data, size_t len,
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const hsiphash_key_t *key);
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u32 __hsiphash_unaligned(const void *data, size_t len,
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const hsiphash_key_t *key);
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u32 hsiphash_1u32(const u32 a, const hsiphash_key_t *key);
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u32 hsiphash_2u32(const u32 a, const u32 b, const hsiphash_key_t *key);
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u32 hsiphash_3u32(const u32 a, const u32 b, const u32 c,
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const hsiphash_key_t *key);
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u32 hsiphash_4u32(const u32 a, const u32 b, const u32 c, const u32 d,
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const hsiphash_key_t *key);
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static inline u32 ___hsiphash_aligned(const __le32 *data, size_t len,
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const hsiphash_key_t *key)
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{
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if (__builtin_constant_p(len) && len == 4)
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return hsiphash_1u32(le32_to_cpu(data[0]), key);
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if (__builtin_constant_p(len) && len == 8)
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return hsiphash_2u32(le32_to_cpu(data[0]), le32_to_cpu(data[1]),
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key);
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if (__builtin_constant_p(len) && len == 12)
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return hsiphash_3u32(le32_to_cpu(data[0]), le32_to_cpu(data[1]),
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le32_to_cpu(data[2]), key);
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if (__builtin_constant_p(len) && len == 16)
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return hsiphash_4u32(le32_to_cpu(data[0]), le32_to_cpu(data[1]),
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le32_to_cpu(data[2]), le32_to_cpu(data[3]),
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key);
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return __hsiphash_aligned(data, len, key);
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}
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/**
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* hsiphash - compute 32-bit hsiphash PRF value
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* @data: buffer to hash
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* @size: size of @data
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* @key: the hsiphash key
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*/
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static inline u32 hsiphash(const void *data, size_t len,
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const hsiphash_key_t *key)
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{
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if (IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS) ||
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!IS_ALIGNED((unsigned long)data, HSIPHASH_ALIGNMENT))
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return __hsiphash_unaligned(data, len, key);
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return ___hsiphash_aligned(data, len, key);
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}
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/*
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* These macros expose the raw SipHash and HalfSipHash permutations.
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* Do not use them directly! If you think you have a use for them,
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* be sure to CC the maintainer of this file explaining why.
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*/
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#define SIPHASH_PERMUTATION(a, b, c, d) ( \
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(a) += (b), (b) = rol64((b), 13), (b) ^= (a), (a) = rol64((a), 32), \
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(c) += (d), (d) = rol64((d), 16), (d) ^= (c), \
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(a) += (d), (d) = rol64((d), 21), (d) ^= (a), \
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(c) += (b), (b) = rol64((b), 17), (b) ^= (c), (c) = rol64((c), 32))
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#define SIPHASH_CONST_0 0x736f6d6570736575ULL
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#define SIPHASH_CONST_1 0x646f72616e646f6dULL
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#define SIPHASH_CONST_2 0x6c7967656e657261ULL
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#define SIPHASH_CONST_3 0x7465646279746573ULL
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#define HSIPHASH_PERMUTATION(a, b, c, d) ( \
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(a) += (b), (b) = rol32((b), 5), (b) ^= (a), (a) = rol32((a), 16), \
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(c) += (d), (d) = rol32((d), 8), (d) ^= (c), \
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(a) += (d), (d) = rol32((d), 7), (d) ^= (a), \
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(c) += (b), (b) = rol32((b), 13), (b) ^= (c), (c) = rol32((c), 16))
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#define HSIPHASH_CONST_0 0U
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#define HSIPHASH_CONST_1 0U
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#define HSIPHASH_CONST_2 0x6c796765U
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#define HSIPHASH_CONST_3 0x74656462U
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#endif /* _LINUX_SIPHASH_H */
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