From: "Jason A. Donenfeld" Jason@zx2c4.com
commit e73aaae2fa9024832e1f42e30c787c7baf61d014 upstream.
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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/char/random.c | 30 +++++++----------------------- include/linux/prandom.h | 23 +++++++---------------- include/linux/siphash.h | 28 ++++++++++++++++++++++++++++ lib/siphash.c | 32 ++++++++++---------------------- 4 files changed, 52 insertions(+), 61 deletions(-)
--- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -51,6 +51,7 @@ #include <linux/syscalls.h> #include <linux/completion.h> #include <linux/uuid.h> +#include <linux/siphash.h> #include <crypto/chacha20.h> #include <crypto/blake2s.h> #include <asm/processor.h> @@ -1012,12 +1013,11 @@ struct fast_pool {
static DEFINE_PER_CPU(struct fast_pool, irq_randomness) = { #ifdef CONFIG_64BIT - /* SipHash constants */ - .pool = { 0x736f6d6570736575UL, 0x646f72616e646f6dUL, - 0x6c7967656e657261UL, 0x7465646279746573UL } +#define FASTMIX_PERM SIPHASH_PERMUTATION + .pool = { SIPHASH_CONST_0, SIPHASH_CONST_1, SIPHASH_CONST_2, SIPHASH_CONST_3 } #else - /* HalfSipHash constants */ - .pool = { 0, 0, 0x6c796765U, 0x74656462U } +#define FASTMIX_PERM HSIPHASH_PERMUTATION + .pool = { HSIPHASH_CONST_0, HSIPHASH_CONST_1, HSIPHASH_CONST_2, HSIPHASH_CONST_3 } #endif };
@@ -1029,27 +1029,11 @@ static DEFINE_PER_CPU(struct fast_pool, */ static void fast_mix(unsigned long s[4], unsigned long v1, unsigned long v2) { -#ifdef CONFIG_64BIT -#define PERM() do { \ - s[0] += s[1]; s[1] = rol64(s[1], 13); s[1] ^= s[0]; s[0] = rol64(s[0], 32); \ - s[2] += s[3]; s[3] = rol64(s[3], 16); s[3] ^= s[2]; \ - s[0] += s[3]; s[3] = rol64(s[3], 21); s[3] ^= s[0]; \ - s[2] += s[1]; s[1] = rol64(s[1], 17); s[1] ^= s[2]; s[2] = rol64(s[2], 32); \ -} while (0) -#else -#define PERM() do { \ - s[0] += s[1]; s[1] = rol32(s[1], 5); s[1] ^= s[0]; s[0] = rol32(s[0], 16); \ - s[2] += s[3]; s[3] = rol32(s[3], 8); s[3] ^= s[2]; \ - s[0] += s[3]; s[3] = rol32(s[3], 7); s[3] ^= s[0]; \ - s[2] += s[1]; s[1] = rol32(s[1], 13); s[1] ^= s[2]; s[2] = rol32(s[2], 16); \ -} while (0) -#endif - s[3] ^= v1; - PERM(); + FASTMIX_PERM(s[0], s[1], s[2], s[3]); s[0] ^= v1; s[3] ^= v2; - PERM(); + FASTMIX_PERM(s[0], s[1], s[2], s[3]); s[0] ^= v2; }
--- a/include/linux/prandom.h +++ b/include/linux/prandom.h @@ -10,6 +10,7 @@
#include <linux/types.h> #include <linux/percpu.h> +#include <linux/siphash.h>
u32 prandom_u32(void); void prandom_bytes(void *buf, size_t nbytes); @@ -21,15 +22,10 @@ void prandom_reseed_late(void); * The core SipHash round function. Each line can be executed in * parallel given enough CPU resources. */ -#define PRND_SIPROUND(v0, v1, v2, v3) ( \ - v0 += v1, v1 = rol64(v1, 13), v2 += v3, v3 = rol64(v3, 16), \ - v1 ^= v0, v0 = rol64(v0, 32), v3 ^= v2, \ - v0 += v3, v3 = rol64(v3, 21), v2 += v1, v1 = rol64(v1, 17), \ - v3 ^= v0, v1 ^= v2, v2 = rol64(v2, 32) \ -) +#define PRND_SIPROUND(v0, v1, v2, v3) SIPHASH_PERMUTATION(v0, v1, v2, v3)
-#define PRND_K0 (0x736f6d6570736575 ^ 0x6c7967656e657261) -#define PRND_K1 (0x646f72616e646f6d ^ 0x7465646279746573) +#define PRND_K0 (SIPHASH_CONST_0 ^ SIPHASH_CONST_2) +#define PRND_K1 (SIPHASH_CONST_1 ^ SIPHASH_CONST_3)
#elif BITS_PER_LONG == 32 /* @@ -37,14 +33,9 @@ void prandom_reseed_late(void); * This is weaker, but 32-bit machines are not used for high-traffic * applications, so there is less output for an attacker to analyze. */ -#define PRND_SIPROUND(v0, v1, v2, v3) ( \ - v0 += v1, v1 = rol32(v1, 5), v2 += v3, v3 = rol32(v3, 8), \ - v1 ^= v0, v0 = rol32(v0, 16), v3 ^= v2, \ - v0 += v3, v3 = rol32(v3, 7), v2 += v1, v1 = rol32(v1, 13), \ - v3 ^= v0, v1 ^= v2, v2 = rol32(v2, 16) \ -) -#define PRND_K0 0x6c796765 -#define PRND_K1 0x74656462 +#define PRND_SIPROUND(v0, v1, v2, v3) HSIPHASH_PERMUTATION(v0, v1, v2, v3) +#define PRND_K0 (HSIPHASH_CONST_0 ^ HSIPHASH_CONST_2) +#define PRND_K1 (HSIPHASH_CONST_1 ^ HSIPHASH_CONST_3)
#else #error Unsupported BITS_PER_LONG --- a/include/linux/siphash.h +++ b/include/linux/siphash.h @@ -136,4 +136,32 @@ static inline u32 hsiphash(const void *d 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 */ --- a/lib/siphash.c +++ b/lib/siphash.c @@ -18,19 +18,13 @@ #include <asm/word-at-a-time.h> #endif
-#define SIPROUND \ - do { \ - v0 += v1; v1 = rol64(v1, 13); v1 ^= v0; v0 = rol64(v0, 32); \ - v2 += v3; v3 = rol64(v3, 16); v3 ^= v2; \ - v0 += v3; v3 = rol64(v3, 21); v3 ^= v0; \ - v2 += v1; v1 = rol64(v1, 17); v1 ^= v2; v2 = rol64(v2, 32); \ - } while (0) +#define SIPROUND SIPHASH_PERMUTATION(v0, v1, v2, v3)
#define PREAMBLE(len) \ - u64 v0 = 0x736f6d6570736575ULL; \ - u64 v1 = 0x646f72616e646f6dULL; \ - u64 v2 = 0x6c7967656e657261ULL; \ - u64 v3 = 0x7465646279746573ULL; \ + u64 v0 = SIPHASH_CONST_0; \ + u64 v1 = SIPHASH_CONST_1; \ + u64 v2 = SIPHASH_CONST_2; \ + u64 v3 = SIPHASH_CONST_3; \ u64 b = ((u64)(len)) << 56; \ v3 ^= key->key[1]; \ v2 ^= key->key[0]; \ @@ -389,19 +383,13 @@ u32 hsiphash_4u32(const u32 first, const } EXPORT_SYMBOL(hsiphash_4u32); #else -#define HSIPROUND \ - do { \ - v0 += v1; v1 = rol32(v1, 5); v1 ^= v0; v0 = rol32(v0, 16); \ - v2 += v3; v3 = rol32(v3, 8); v3 ^= v2; \ - v0 += v3; v3 = rol32(v3, 7); v3 ^= v0; \ - v2 += v1; v1 = rol32(v1, 13); v1 ^= v2; v2 = rol32(v2, 16); \ - } while (0) +#define HSIPROUND HSIPHASH_PERMUTATION(v0, v1, v2, v3)
#define HPREAMBLE(len) \ - u32 v0 = 0; \ - u32 v1 = 0; \ - u32 v2 = 0x6c796765U; \ - u32 v3 = 0x74656462U; \ + u32 v0 = HSIPHASH_CONST_0; \ + u32 v1 = HSIPHASH_CONST_1; \ + u32 v2 = HSIPHASH_CONST_2; \ + u32 v3 = HSIPHASH_CONST_3; \ u32 b = ((u32)(len)) << 24; \ v3 ^= key->key[1]; \ v2 ^= key->key[0]; \