Olivier Deprez | 0e64123 | 2021-09-23 10:07:05 +0200 | [diff] [blame] | 1 | /* SPDX-License-Identifier: GPL-2.0 */ |
| 2 | /* |
| 3 | * include/linux/prandom.h |
| 4 | * |
| 5 | * Include file for the fast pseudo-random 32-bit |
| 6 | * generation. |
| 7 | */ |
| 8 | #ifndef _LINUX_PRANDOM_H |
| 9 | #define _LINUX_PRANDOM_H |
| 10 | |
| 11 | #include <linux/types.h> |
| 12 | #include <linux/percpu.h> |
| 13 | |
| 14 | u32 prandom_u32(void); |
| 15 | void prandom_bytes(void *buf, size_t nbytes); |
| 16 | void prandom_seed(u32 seed); |
| 17 | void prandom_reseed_late(void); |
| 18 | |
Olivier Deprez | 157378f | 2022-04-04 15:47:50 +0200 | [diff] [blame^] | 19 | DECLARE_PER_CPU(unsigned long, net_rand_noise); |
| 20 | |
| 21 | #define PRANDOM_ADD_NOISE(a, b, c, d) \ |
| 22 | prandom_u32_add_noise((unsigned long)(a), (unsigned long)(b), \ |
| 23 | (unsigned long)(c), (unsigned long)(d)) |
| 24 | |
Olivier Deprez | 0e64123 | 2021-09-23 10:07:05 +0200 | [diff] [blame] | 25 | #if BITS_PER_LONG == 64 |
| 26 | /* |
| 27 | * The core SipHash round function. Each line can be executed in |
| 28 | * parallel given enough CPU resources. |
| 29 | */ |
| 30 | #define PRND_SIPROUND(v0, v1, v2, v3) ( \ |
| 31 | v0 += v1, v1 = rol64(v1, 13), v2 += v3, v3 = rol64(v3, 16), \ |
| 32 | v1 ^= v0, v0 = rol64(v0, 32), v3 ^= v2, \ |
| 33 | v0 += v3, v3 = rol64(v3, 21), v2 += v1, v1 = rol64(v1, 17), \ |
| 34 | v3 ^= v0, v1 ^= v2, v2 = rol64(v2, 32) \ |
| 35 | ) |
| 36 | |
| 37 | #define PRND_K0 (0x736f6d6570736575 ^ 0x6c7967656e657261) |
| 38 | #define PRND_K1 (0x646f72616e646f6d ^ 0x7465646279746573) |
| 39 | |
| 40 | #elif BITS_PER_LONG == 32 |
| 41 | /* |
| 42 | * On 32-bit machines, we use HSipHash, a reduced-width version of SipHash. |
| 43 | * This is weaker, but 32-bit machines are not used for high-traffic |
| 44 | * applications, so there is less output for an attacker to analyze. |
| 45 | */ |
| 46 | #define PRND_SIPROUND(v0, v1, v2, v3) ( \ |
| 47 | v0 += v1, v1 = rol32(v1, 5), v2 += v3, v3 = rol32(v3, 8), \ |
| 48 | v1 ^= v0, v0 = rol32(v0, 16), v3 ^= v2, \ |
| 49 | v0 += v3, v3 = rol32(v3, 7), v2 += v1, v1 = rol32(v1, 13), \ |
| 50 | v3 ^= v0, v1 ^= v2, v2 = rol32(v2, 16) \ |
| 51 | ) |
| 52 | #define PRND_K0 0x6c796765 |
| 53 | #define PRND_K1 0x74656462 |
| 54 | |
| 55 | #else |
| 56 | #error Unsupported BITS_PER_LONG |
| 57 | #endif |
| 58 | |
Olivier Deprez | 157378f | 2022-04-04 15:47:50 +0200 | [diff] [blame^] | 59 | static inline void prandom_u32_add_noise(unsigned long a, unsigned long b, |
| 60 | unsigned long c, unsigned long d) |
| 61 | { |
| 62 | /* |
| 63 | * This is not used cryptographically; it's just |
| 64 | * a convenient 4-word hash function. (3 xor, 2 add, 2 rol) |
| 65 | */ |
| 66 | a ^= raw_cpu_read(net_rand_noise); |
| 67 | PRND_SIPROUND(a, b, c, d); |
| 68 | raw_cpu_write(net_rand_noise, d); |
| 69 | } |
| 70 | |
Olivier Deprez | 0e64123 | 2021-09-23 10:07:05 +0200 | [diff] [blame] | 71 | struct rnd_state { |
| 72 | __u32 s1, s2, s3, s4; |
| 73 | }; |
| 74 | |
| 75 | u32 prandom_u32_state(struct rnd_state *state); |
| 76 | void prandom_bytes_state(struct rnd_state *state, void *buf, size_t nbytes); |
| 77 | void prandom_seed_full_state(struct rnd_state __percpu *pcpu_state); |
| 78 | |
| 79 | #define prandom_init_once(pcpu_state) \ |
| 80 | DO_ONCE(prandom_seed_full_state, (pcpu_state)) |
| 81 | |
| 82 | /** |
| 83 | * prandom_u32_max - returns a pseudo-random number in interval [0, ep_ro) |
| 84 | * @ep_ro: right open interval endpoint |
| 85 | * |
| 86 | * Returns a pseudo-random number that is in interval [0, ep_ro). Note |
| 87 | * that the result depends on PRNG being well distributed in [0, ~0U] |
| 88 | * u32 space. Here we use maximally equidistributed combined Tausworthe |
| 89 | * generator, that is, prandom_u32(). This is useful when requesting a |
| 90 | * random index of an array containing ep_ro elements, for example. |
| 91 | * |
| 92 | * Returns: pseudo-random number in interval [0, ep_ro) |
| 93 | */ |
| 94 | static inline u32 prandom_u32_max(u32 ep_ro) |
| 95 | { |
| 96 | return (u32)(((u64) prandom_u32() * ep_ro) >> 32); |
| 97 | } |
| 98 | |
| 99 | /* |
| 100 | * Handle minimum values for seeds |
| 101 | */ |
| 102 | static inline u32 __seed(u32 x, u32 m) |
| 103 | { |
| 104 | return (x < m) ? x + m : x; |
| 105 | } |
| 106 | |
| 107 | /** |
| 108 | * prandom_seed_state - set seed for prandom_u32_state(). |
| 109 | * @state: pointer to state structure to receive the seed. |
| 110 | * @seed: arbitrary 64-bit value to use as a seed. |
| 111 | */ |
| 112 | static inline void prandom_seed_state(struct rnd_state *state, u64 seed) |
| 113 | { |
| 114 | u32 i = ((seed >> 32) ^ (seed << 10) ^ seed) & 0xffffffffUL; |
| 115 | |
| 116 | state->s1 = __seed(i, 2U); |
| 117 | state->s2 = __seed(i, 8U); |
| 118 | state->s3 = __seed(i, 16U); |
| 119 | state->s4 = __seed(i, 128U); |
Olivier Deprez | 157378f | 2022-04-04 15:47:50 +0200 | [diff] [blame^] | 120 | PRANDOM_ADD_NOISE(state, i, 0, 0); |
Olivier Deprez | 0e64123 | 2021-09-23 10:07:05 +0200 | [diff] [blame] | 121 | } |
| 122 | |
| 123 | /* Pseudo random number generator from numerical recipes. */ |
| 124 | static inline u32 next_pseudo_random32(u32 seed) |
| 125 | { |
| 126 | return seed * 1664525 + 1013904223; |
| 127 | } |
| 128 | |
| 129 | #endif |