| /* $OpenBSD: arc4random.c,v 1.50 2014/07/21 18:13:12 deraadt Exp $ */ |
| |
| /* |
| * Copyright (c) 1996, David Mazieres <dm@uun.org> |
| * Copyright (c) 2008, Damien Miller <djm@openbsd.org> |
| * Copyright (c) 2013, Markus Friedl <markus@openbsd.org> |
| * |
| * 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 for OpenBSD. |
| */ |
| |
| #include <fcntl.h> |
| #include <limits.h> |
| #include <signal.h> |
| #include <stdint.h> |
| #include <stdlib.h> |
| #include <string.h> |
| #include <unistd.h> |
| #include <sys/types.h> |
| #include <sys/param.h> |
| #include <sys/time.h> |
| |
| #define KEYSTREAM_ONLY |
| #include "chacha_private.h" |
| |
| #define min(a, b) ((a) < (b) ? (a) : (b)) |
| #ifdef __GNUC__ |
| #define inline __inline |
| #else /* !__GNUC__ */ |
| #define inline |
| #endif /* !__GNUC__ */ |
| |
| #define KEYSZ 32 |
| #define IVSZ 8 |
| #define BLOCKSZ 64 |
| #define RSBUFSZ (16*BLOCKSZ) |
| |
| /* Marked MAP_INHERIT_ZERO, so zero'd out in fork children. */ |
| static struct _rs { |
| size_t rs_have; /* valid bytes at end of rs_buf */ |
| size_t rs_count; /* bytes till reseed */ |
| } *rs; |
| |
| /* Maybe be preserved in fork children, if _rs_allocate() decides. */ |
| static struct _rsx { |
| chacha_ctx rs_chacha; /* chacha context for random keystream */ |
| u_char rs_buf[RSBUFSZ]; /* keystream blocks */ |
| } *rsx; |
| |
| static inline int _rs_allocate(struct _rs **, struct _rsx **); |
| static inline void _rs_forkdetect(void); |
| #include "arc4random.h" |
| |
| static inline void _rs_rekey(u_char *dat, size_t datlen); |
| |
| static inline void |
| _rs_init(u_char *buf, size_t n) |
| { |
| if (n < KEYSZ + IVSZ) |
| return; |
| |
| if (rs == NULL) { |
| if (_rs_allocate(&rs, &rsx) == -1) |
| abort(); |
| } |
| |
| chacha_keysetup(&rsx->rs_chacha, buf, KEYSZ * 8, 0); |
| chacha_ivsetup(&rsx->rs_chacha, buf + KEYSZ); |
| } |
| |
| static void |
| _rs_stir(void) |
| { |
| u_char rnd[KEYSZ + IVSZ]; |
| |
| if (getentropy(rnd, sizeof rnd) == -1) |
| _getentropy_fail(); |
| |
| if (!rs) |
| _rs_init(rnd, sizeof(rnd)); |
| else |
| _rs_rekey(rnd, sizeof(rnd)); |
| explicit_bzero(rnd, sizeof(rnd)); /* discard source seed */ |
| |
| /* invalidate rs_buf */ |
| rs->rs_have = 0; |
| memset(rsx->rs_buf, 0, sizeof(rsx->rs_buf)); |
| |
| rs->rs_count = 1600000; |
| } |
| |
| static inline void |
| _rs_stir_if_needed(size_t len) |
| { |
| _rs_forkdetect(); |
| if (!rs || rs->rs_count <= len) |
| _rs_stir(); |
| if (rs->rs_count <= len) |
| rs->rs_count = 0; |
| else |
| rs->rs_count -= len; |
| } |
| |
| static inline void |
| _rs_rekey(u_char *dat, size_t datlen) |
| { |
| #ifndef KEYSTREAM_ONLY |
| memset(rsx->rs_buf, 0, sizeof(rsx->rs_buf)); |
| #endif |
| /* fill rs_buf with the keystream */ |
| chacha_encrypt_bytes(&rsx->rs_chacha, rsx->rs_buf, |
| rsx->rs_buf, sizeof(rsx->rs_buf)); |
| /* mix in optional user provided data */ |
| if (dat) { |
| size_t i, m; |
| |
| m = min(datlen, KEYSZ + IVSZ); |
| for (i = 0; i < m; i++) |
| rsx->rs_buf[i] ^= dat[i]; |
| } |
| /* immediately reinit for backtracking resistance */ |
| _rs_init(rsx->rs_buf, KEYSZ + IVSZ); |
| memset(rsx->rs_buf, 0, KEYSZ + IVSZ); |
| rs->rs_have = sizeof(rsx->rs_buf) - KEYSZ - IVSZ; |
| } |
| |
| static inline void |
| _rs_random_buf(void *_buf, size_t n) |
| { |
| u_char *buf = (u_char *)_buf; |
| u_char *keystream; |
| size_t m; |
| |
| _rs_stir_if_needed(n); |
| while (n > 0) { |
| if (rs->rs_have > 0) { |
| m = min(n, rs->rs_have); |
| keystream = rsx->rs_buf + sizeof(rsx->rs_buf) |
| - rs->rs_have; |
| memcpy(buf, keystream, m); |
| memset(keystream, 0, m); |
| buf += m; |
| n -= m; |
| rs->rs_have -= m; |
| } |
| if (rs->rs_have == 0) |
| _rs_rekey(NULL, 0); |
| } |
| } |
| |
| static inline void |
| _rs_random_u32(uint32_t *val) |
| { |
| u_char *keystream; |
| |
| _rs_stir_if_needed(sizeof(*val)); |
| if (rs->rs_have < sizeof(*val)) |
| _rs_rekey(NULL, 0); |
| keystream = rsx->rs_buf + sizeof(rsx->rs_buf) - rs->rs_have; |
| memcpy(val, keystream, sizeof(*val)); |
| memset(keystream, 0, sizeof(*val)); |
| rs->rs_have -= sizeof(*val); |
| } |
| |
| uint32_t |
| arc4random(void) |
| { |
| uint32_t val; |
| |
| _ARC4_LOCK(); |
| _rs_random_u32(&val); |
| _ARC4_UNLOCK(); |
| return val; |
| } |
| |
| void |
| arc4random_buf(void *buf, size_t n) |
| { |
| _ARC4_LOCK(); |
| _rs_random_buf(buf, n); |
| _ARC4_UNLOCK(); |
| } |