diff options
Diffstat (limited to 'openbsd-compat/arc4random.c')
| -rw-r--r-- | openbsd-compat/arc4random.c | 254 |
1 files changed, 254 insertions, 0 deletions
diff --git a/openbsd-compat/arc4random.c b/openbsd-compat/arc4random.c new file mode 100644 index 0000000..ffd3373 --- /dev/null +++ b/openbsd-compat/arc4random.c @@ -0,0 +1,254 @@ +/* $OpenBSD: arc4random.c,v 1.58 2022/07/31 13:41:45 tb 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> + * Copyright (c) 2014, Theo de Raadt <deraadt@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. + */ + +/* OPENBSD ORIGINAL: lib/libc/crypt/arc4random.c */ + +#include "includes.h" + +#include <sys/types.h> + +#include <fcntl.h> +#include <limits.h> +#include <signal.h> +#ifdef HAVE_STDINT_H +#include <stdint.h> +#endif +#include <stdlib.h> +#include <string.h> +#include <unistd.h> +#include <sys/types.h> +#include <sys/time.h> + +#ifndef HAVE_ARC4RANDOM + +/* + * Always use the getentropy implementation from bsd-getentropy.c, which + * will call a native getentropy if available then fall back as required. + * We use a different name so that OpenSSL cannot call the wrong getentropy. + */ +int _ssh_compat_getentropy(void *, size_t); +#ifdef getentropy +# undef getentropy +#endif +#define getentropy(x, y) (_ssh_compat_getentropy((x), (y))) + +#include "log.h" + +#define KEYSTREAM_ONLY +#include "chacha_private.h" + +#define minimum(a, b) ((a) < (b) ? (a) : (b)) + +#if defined(__GNUC__) || defined(_MSC_VER) +#define inline __inline +#else /* __GNUC__ || _MSC_VER */ +#define inline +#endif /* !__GNUC__ && !_MSC_VER */ + +#define KEYSZ 32 +#define IVSZ 8 +#define BLOCKSZ 64 +#define RSBUFSZ (16*BLOCKSZ) + +#define REKEY_BASE (1024*1024) /* NB. should be a power of 2 */ + +/* 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) + _exit(1); + } + + chacha_keysetup(&rsx->rs_chacha, buf, KEYSZ * 8); + chacha_ivsetup(&rsx->rs_chacha, buf + KEYSZ); +} + +static void +_rs_stir(void) +{ + u_char rnd[KEYSZ + IVSZ]; + uint32_t rekey_fuzz = 0; + + 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)); + + /* rekey interval should not be predictable */ + chacha_encrypt_bytes(&rsx->rs_chacha, (uint8_t *)&rekey_fuzz, + (uint8_t *)&rekey_fuzz, sizeof(rekey_fuzz)); + rs->rs_count = REKEY_BASE + (rekey_fuzz % REKEY_BASE); +} + +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 = minimum(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 = minimum(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; +} +DEF_WEAK(arc4random); + +/* + * If we are providing arc4random, then we can provide a more efficient + * arc4random_buf(). + */ +# ifndef HAVE_ARC4RANDOM_BUF +void +arc4random_buf(void *buf, size_t n) +{ + _ARC4_LOCK(); + _rs_random_buf(buf, n); + _ARC4_UNLOCK(); +} +DEF_WEAK(arc4random_buf); +# endif /* !HAVE_ARC4RANDOM_BUF */ +#endif /* !HAVE_ARC4RANDOM */ + +/* arc4random_buf() that uses platform arc4random() */ +#if !defined(HAVE_ARC4RANDOM_BUF) && defined(HAVE_ARC4RANDOM) +void +arc4random_buf(void *_buf, size_t n) +{ + size_t i; + u_int32_t r = 0; + char *buf = (char *)_buf; + + for (i = 0; i < n; i++) { + if (i % 4 == 0) + r = arc4random(); + buf[i] = r & 0xff; + r >>= 8; + } + explicit_bzero(&r, sizeof(r)); +} +#endif /* !defined(HAVE_ARC4RANDOM_BUF) && defined(HAVE_ARC4RANDOM) */ + |