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authorJason A. Donenfeld <Jason@zx2c4.com>2022-05-07 14:03:46 +0200
committerJason A. Donenfeld <Jason@zx2c4.com>2022-05-18 15:53:52 +0200
commite73aaae2fa9024832e1f42e30c787c7baf61d014 (patch)
tree151a956250ad489a31c98047f24ea82fa157a1a8 /include/linux/prandom.h
parent791332b3cbb080510954a4c152ce02af8832eac9 (diff)
downloadlinux-e73aaae2fa9024832e1f42e30c787c7baf61d014.tar.gz
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 <Jason@zx2c4.com>
Diffstat (limited to 'include/linux/prandom.h')
-rw-r--r--include/linux/prandom.h23
1 files changed, 7 insertions, 16 deletions
diff --git a/include/linux/prandom.h b/include/linux/prandom.h
index 056d31317e49..a4aadd2dc153 100644
--- 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);
@@ -27,15 +28,10 @@ DECLARE_PER_CPU(unsigned long, net_rand_noise);
* 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
/*
@@ -43,14 +39,9 @@ DECLARE_PER_CPU(unsigned long, net_rand_noise);
* 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