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Diffstat (limited to 'code/ecp/crypto/arc4random/arc4random.c')
| -rwxr-xr-x | code/ecp/crypto/arc4random/arc4random.c | 259 |
1 files changed, 259 insertions, 0 deletions
diff --git a/code/ecp/crypto/arc4random/arc4random.c b/code/ecp/crypto/arc4random/arc4random.c new file mode 100755 index 0000000..e891dd6 --- /dev/null +++ b/code/ecp/crypto/arc4random/arc4random.c @@ -0,0 +1,259 @@ +/* + * Copyright (c) 1996, David Mazieres <dm@uun.org> + * Copyright (c) 2008, Damien Miller <djm@openbsd.org> + * Copyright (c) 2013, Markus Friedl <markus@openbsd.org> + * Copyright (c) 2014, Theo de Raadt <deraadt@openbsd.org> + * Copyright (c) 2015, Sudhi Herle <sudhi@herle.net> + * + * Permission to use, copy, modify, and distribute this software for any + * purpose with or without fee is hereby granted, provided that the above + * copyright notice and this permission notice appear in all copies. + * + * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES + * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF + * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR + * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES + * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN + * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF + * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. + */ + + +/* + * ChaCha based random number generator from OpenBSD. + * + * Made fully portable and thread-safe by Sudhi Herle. + */ + +#include <stdint.h> +#include <stdlib.h> +#include <string.h> +#include <sys/types.h> +#include <assert.h> + +#define ARC4R_KEYSZ 32 +#define ARC4R_IVSZ 8 +#define ARC4R_BLOCKSZ 64 +#define ARC4R_RSBUFSZ (16*ARC4R_BLOCKSZ) + +typedef struct +{ + uint32_t input[16]; /* could be compressed */ +} chacha_ctx; + +struct rand_state +{ + size_t rs_have; /* valid bytes at end of rs_buf */ + size_t rs_count; /* bytes till reseed */ + chacha_ctx rs_chacha; /* chacha context for random keystream */ + u_char rs_buf[ARC4R_RSBUFSZ]; /* keystream blocks */ +}; +typedef struct rand_state rand_state; + + +/* kernel entropy */ +static int (*getentropy) (void* buf, size_t n); + + +#define KEYSTREAM_ONLY +#include "chacha_private.h" + +#define minimum(a, b) ((a) < (b) ? (a) : (b)) + +#include "arc4random.h" + + +static inline void +_rs_init(rand_state* st, u8 *buf, size_t n) +{ + assert(n >= (ARC4R_KEYSZ + ARC4R_IVSZ)); + + chacha_keysetup(&st->rs_chacha, buf, ARC4R_KEYSZ * 8, 0); + chacha_ivsetup(&st->rs_chacha, buf + ARC4R_KEYSZ); +} + + + +static inline void +_rs_rekey(rand_state* st, u8 *dat, size_t datlen) +{ + /* fill rs_buf with the keystream */ + chacha_encrypt_bytes(&st->rs_chacha, st->rs_buf, st->rs_buf, sizeof st->rs_buf); + + /* mix in optional user provided data */ + if (dat) { + size_t i, m; + + m = minimum(datlen, ARC4R_KEYSZ + ARC4R_IVSZ); + for (i = 0; i < m; i++) + st->rs_buf[i] ^= dat[i]; + + memset(dat, 0, datlen); + } + + /* immediately reinit for backtracking resistance */ + _rs_init(st, st->rs_buf, ARC4R_KEYSZ + ARC4R_IVSZ); + memset(st->rs_buf, 0, ARC4R_KEYSZ + ARC4R_IVSZ); + st->rs_have = (sizeof st->rs_buf) - ARC4R_KEYSZ - ARC4R_IVSZ; +} + + +static void +_rs_stir(rand_state* st) +{ + u8 rnd[ARC4R_KEYSZ + ARC4R_IVSZ]; + + + int r = getentropy(rnd, sizeof rnd); + assert(r == 0); + + _rs_rekey(st, rnd, sizeof(rnd)); + + /* invalidate rs_buf */ + st->rs_have = 0; + memset(st->rs_buf, 0, sizeof st->rs_buf); + + st->rs_count = 1600000; +} + + +static inline void +_rs_stir_if_needed(rand_state* st, size_t len) +{ + if (st->rs_count <= len) + _rs_stir(st); + + st->rs_count -= len; +} + + +static inline void +_rs_random_buf(rand_state* rs, void *_buf, size_t n) +{ + u8 *buf = (u8 *)_buf; + u8 *keystream; + size_t m; + + _rs_stir_if_needed(rs, n); + while (n > 0) { + if (rs->rs_have > 0) { + m = minimum(n, rs->rs_have); + keystream = rs->rs_buf + sizeof(rs->rs_buf) - rs->rs_have; + memcpy(buf, keystream, m); + memset(keystream, 0, m); + buf += m; + n -= m; + rs->rs_have -= m; + } else + _rs_rekey(rs, NULL, 0); + } +} + +static inline uint32_t +_rs_random_u32(rand_state* rs) +{ + u8 *keystream; + uint32_t val; + + _rs_stir_if_needed(rs, sizeof(val)); + if (rs->rs_have < sizeof(val)) + _rs_rekey(rs, NULL, 0); + keystream = rs->rs_buf + sizeof(rs->rs_buf) - rs->rs_have; + memcpy(&val, keystream, sizeof(val)); + memset(keystream, 0, sizeof(val)); + rs->rs_have -= sizeof(val); + + return val; +} + + +/* + * Use gcc extension to declare a thread-local variable. + * + * On most systems (including x86_64), thread-local access is + * essentially free for non .so use cases. + * + */ +static rand_state st = { .rs_count = 0 }; +static inline rand_state* +sget() +{ + rand_state* s = &st; + + if (s->rs_count == 0) + _rs_stir(s); + return s; +} + + + +/* + * Public API. + */ + + +void +arc4random_init(int (*f) (void*, size_t)) +{ + getentropy = f; +} + + +uint32_t +arc4random() +{ + rand_state* z = sget(); + + return _rs_random_u32(z); +} + + +void +arc4random_buf(void* b, size_t n) +{ + rand_state* z = sget(); + + _rs_random_buf(z, b, n); +} + + + + +/* + * Calculate a uniformly distributed random number less than upper_bound + * avoiding "modulo bias". + * + * Uniformity is achieved by generating new random numbers until the one + * returned is outside the range [0, 2**32 % upper_bound). This + * guarantees the selected random number will be inside + * [2**32 % upper_bound, 2**32) which maps back to [0, upper_bound) + * after reduction modulo upper_bound. + */ +uint32_t +arc4random_uniform(uint32_t upper_bound) +{ + rand_state* z = sget(); + uint32_t r, min; + + if (upper_bound < 2) + return 0; + + /* 2**32 % x == (2**32 - x) % x */ + min = -upper_bound % upper_bound; + + /* + * This could theoretically loop forever but each retry has + * p > 0.5 (worst case, usually far better) of selecting a + * number inside the range we need, so it should rarely need + * to re-roll. + */ + for (;;) { + r = _rs_random_u32(z); + if (r >= min) + break; + } + + return r % upper_bound; +} + +/* EOF */ |