From e73aaae2fa9024832e1f42e30c787c7baf61d014 Mon Sep 17 00:00:00 2001 From: "Jason A. Donenfeld" Date: Sat, 7 May 2022 14:03:46 +0200 Subject: siphash: use one source of truth for siphash permutations 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 --- include/linux/siphash.h | 28 ++++++++++++++++++++++++++++ 1 file changed, 28 insertions(+) (limited to 'include/linux/siphash.h') diff --git a/include/linux/siphash.h b/include/linux/siphash.h index cce8a9acc76c..3af1428da559 100644 --- a/include/linux/siphash.h +++ b/include/linux/siphash.h @@ -138,4 +138,32 @@ static inline u32 hsiphash(const void *data, size_t len, return ___hsiphash_aligned(data, len, key); } +/* + * These macros expose the raw SipHash and HalfSipHash permutations. + * Do not use them directly! If you think you have a use for them, + * be sure to CC the maintainer of this file explaining why. + */ + +#define SIPHASH_PERMUTATION(a, b, c, d) ( \ + (a) += (b), (b) = rol64((b), 13), (b) ^= (a), (a) = rol64((a), 32), \ + (c) += (d), (d) = rol64((d), 16), (d) ^= (c), \ + (a) += (d), (d) = rol64((d), 21), (d) ^= (a), \ + (c) += (b), (b) = rol64((b), 17), (b) ^= (c), (c) = rol64((c), 32)) + +#define SIPHASH_CONST_0 0x736f6d6570736575ULL +#define SIPHASH_CONST_1 0x646f72616e646f6dULL +#define SIPHASH_CONST_2 0x6c7967656e657261ULL +#define SIPHASH_CONST_3 0x7465646279746573ULL + +#define HSIPHASH_PERMUTATION(a, b, c, d) ( \ + (a) += (b), (b) = rol32((b), 5), (b) ^= (a), (a) = rol32((a), 16), \ + (c) += (d), (d) = rol32((d), 8), (d) ^= (c), \ + (a) += (d), (d) = rol32((d), 7), (d) ^= (a), \ + (c) += (b), (b) = rol32((b), 13), (b) ^= (c), (c) = rol32((c), 16)) + +#define HSIPHASH_CONST_0 0U +#define HSIPHASH_CONST_1 0U +#define HSIPHASH_CONST_2 0x6c796765U +#define HSIPHASH_CONST_3 0x74656462U + #endif /* _LINUX_SIPHASH_H */ -- cgit v1.2.3 From 53c83d6d8e399fad3d3d25df0ea0d54eb0f94f88 Mon Sep 17 00:00:00 2001 From: "Jason A. Donenfeld" Date: Wed, 18 May 2022 15:23:45 +0200 Subject: siphash: add SPDX tags as sole licensing authority The text "dual BSD/GPLv2 license" is somewhat ambiguous, and moving this over to SPDX is overdue. This commit adds SPDX tags to the relevant files and clarifies that it's GPLv2 only and 3-clause BSD. It also removes the old text, so that the SPDX tags are the only source of the information. Suggested-by: Thomas Gleixner Signed-off-by: Jason A. Donenfeld Signed-off-by: Greg Kroah-Hartman --- include/linux/siphash.h | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) (limited to 'include/linux/siphash.h') diff --git a/include/linux/siphash.h b/include/linux/siphash.h index cce8a9acc76c..9e822311b29e 100644 --- a/include/linux/siphash.h +++ b/include/linux/siphash.h @@ -1,6 +1,5 @@ -/* Copyright (C) 2016 Jason A. Donenfeld . All Rights Reserved. - * - * This file is provided under a dual BSD/GPLv2 license. +/* SPDX-License-Identifier: (GPL-2.0-only OR BSD-3-Clause) */ +/* Copyright (C) 2016-2022 Jason A. Donenfeld . All Rights Reserved. * * SipHash: a fast short-input PRF * https://131002.net/siphash/ -- cgit v1.2.3