258 lines
6.1 KiB
C
258 lines
6.1 KiB
C
/* $OpenBSD: arc4random.c,v 1.58 2022/07/31 13:41:45 tb Exp $ */
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/*
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* Copyright (c) 1996, David Mazieres <dm@uun.org>
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* Copyright (c) 2008, Damien Miller <djm@openbsd.org>
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* Copyright (c) 2013, Markus Friedl <markus@openbsd.org>
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* Copyright (c) 2014, Theo de Raadt <deraadt@openbsd.org>
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*
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* Permission to use, copy, modify, and distribute this software for any
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* purpose with or without fee is hereby granted, provided that the above
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* copyright notice and this permission notice appear in all copies.
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*
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* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
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* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
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* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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*/
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/*
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* ChaCha based random number generator for OpenBSD.
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*/
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/* OPENBSD ORIGINAL: lib/libc/crypt/arc4random.c */
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#include "includes.h"
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#include <sys/types.h>
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#include <fcntl.h>
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#include <limits.h>
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#include <signal.h>
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#ifdef HAVE_STDINT_H
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#include <stdint.h>
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#endif
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#include <stdlib.h>
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#include <string.h>
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#include <unistd.h>
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#include <sys/types.h>
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#include <sys/time.h>
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#ifndef HAVE_ARC4RANDOM
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/*
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* Always use the getentropy implementation from bsd-getentropy.c, which
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* will call a native getentropy if available then fall back as required.
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* We use a different name so that OpenSSL cannot call the wrong getentropy.
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*/
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int _ssh_compat_getentropy(void *, size_t);
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#ifdef getentropy
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# undef getentropy
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#endif
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#define getentropy(x, y) (_ssh_compat_getentropy((x), (y)))
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#include "log.h"
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#define KEYSTREAM_ONLY
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#include "chacha_private.h"
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#define minimum(a, b) ((a) < (b) ? (a) : (b))
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#if defined(__GNUC__) || defined(_MSC_VER)
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#define inline __inline
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#else /* __GNUC__ || _MSC_VER */
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#define inline
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#endif /* !__GNUC__ && !_MSC_VER */
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#define KEYSZ 32
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#define IVSZ 8
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#define BLOCKSZ 64
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#define RSBUFSZ (16*BLOCKSZ)
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#define REKEY_BASE (1024*1024) /* NB. should be a power of 2 */
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/* Marked MAP_INHERIT_ZERO, so zero'd out in fork children. */
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static struct _rs {
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size_t rs_have; /* valid bytes at end of rs_buf */
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size_t rs_count; /* bytes till reseed */
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} *rs;
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/* Maybe be preserved in fork children, if _rs_allocate() decides. */
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static struct _rsx {
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chacha_ctx rs_chacha; /* chacha context for random keystream */
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u_char rs_buf[RSBUFSZ]; /* keystream blocks */
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} *rsx;
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static inline int _rs_allocate(struct _rs **, struct _rsx **);
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static inline void _rs_forkdetect(void);
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#ifdef WINDOWS
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#include "arc4random_win.h"
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#else
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#include "arc4random.h"
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#endif /* WINDOWS*/
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static inline void _rs_rekey(u_char *dat, size_t datlen);
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static inline void
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_rs_init(u_char* buf, size_t n)
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{
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if (n < KEYSZ + IVSZ)
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return;
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if (rs == NULL) {
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if (_rs_allocate(&rs, &rsx) == -1)
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_exit(1);
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}
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chacha_keysetup(&rsx->rs_chacha, buf, KEYSZ * 8);
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chacha_ivsetup(&rsx->rs_chacha, buf + KEYSZ);
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}
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static void
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_rs_stir(void)
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{
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u_char rnd[KEYSZ + IVSZ];
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uint32_t rekey_fuzz = 0;
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if (getentropy(rnd, sizeof rnd) == -1)
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_getentropy_fail();
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if (!rs)
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_rs_init(rnd, sizeof(rnd));
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else
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_rs_rekey(rnd, sizeof(rnd));
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explicit_bzero(rnd, sizeof(rnd)); /* discard source seed */
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/* invalidate rs_buf */
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rs->rs_have = 0;
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memset(rsx->rs_buf, 0, sizeof(rsx->rs_buf));
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/* rekey interval should not be predictable */
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chacha_encrypt_bytes(&rsx->rs_chacha, (uint8_t *)&rekey_fuzz,
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(uint8_t *)&rekey_fuzz, sizeof(rekey_fuzz));
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rs->rs_count = REKEY_BASE + (rekey_fuzz % REKEY_BASE);
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}
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static inline void
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_rs_stir_if_needed(size_t len)
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{
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_rs_forkdetect();
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if (!rs || rs->rs_count <= len)
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_rs_stir();
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if (rs->rs_count <= len)
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rs->rs_count = 0;
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else
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rs->rs_count -= len;
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}
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static inline void
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_rs_rekey(u_char *dat, size_t datlen)
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{
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#ifndef KEYSTREAM_ONLY
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memset(rsx->rs_buf, 0, sizeof(rsx->rs_buf));
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#endif
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/* fill rs_buf with the keystream */
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chacha_encrypt_bytes(&rsx->rs_chacha, rsx->rs_buf,
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rsx->rs_buf, sizeof(rsx->rs_buf));
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/* mix in optional user provided data */
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if (dat) {
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size_t i, m;
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m = minimum(datlen, KEYSZ + IVSZ);
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for (i = 0; i < m; i++)
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rsx->rs_buf[i] ^= dat[i];
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}
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/* immediately reinit for backtracking resistance */
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_rs_init(rsx->rs_buf, KEYSZ + IVSZ);
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memset(rsx->rs_buf, 0, KEYSZ + IVSZ);
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rs->rs_have = sizeof(rsx->rs_buf) - KEYSZ - IVSZ;
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}
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static inline void
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_rs_random_buf(void *_buf, size_t n)
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{
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u_char *buf = (u_char *)_buf;
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u_char *keystream;
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size_t m;
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_rs_stir_if_needed(n);
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while (n > 0) {
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if (rs->rs_have > 0) {
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m = minimum(n, rs->rs_have);
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keystream = rsx->rs_buf + sizeof(rsx->rs_buf)
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- rs->rs_have;
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memcpy(buf, keystream, m);
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memset(keystream, 0, m);
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buf += m;
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n -= m;
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rs->rs_have -= m;
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}
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if (rs->rs_have == 0)
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_rs_rekey(NULL, 0);
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}
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}
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static inline void
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_rs_random_u32(uint32_t *val)
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{
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u_char *keystream;
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_rs_stir_if_needed(sizeof(*val));
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if (rs->rs_have < sizeof(*val))
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_rs_rekey(NULL, 0);
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keystream = rsx->rs_buf + sizeof(rsx->rs_buf) - rs->rs_have;
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memcpy(val, keystream, sizeof(*val));
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memset(keystream, 0, sizeof(*val));
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rs->rs_have -= sizeof(*val);
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}
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uint32_t
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arc4random(void)
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{
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uint32_t val;
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_ARC4_LOCK();
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_rs_random_u32(&val);
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_ARC4_UNLOCK();
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return val;
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}
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DEF_WEAK(arc4random);
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/*
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* If we are providing arc4random, then we can provide a more efficient
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* arc4random_buf().
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*/
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# ifndef HAVE_ARC4RANDOM_BUF
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void
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arc4random_buf(void *buf, size_t n)
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{
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_ARC4_LOCK();
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_rs_random_buf(buf, n);
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_ARC4_UNLOCK();
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}
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DEF_WEAK(arc4random_buf);
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# endif /* !HAVE_ARC4RANDOM_BUF */
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#endif /* !HAVE_ARC4RANDOM */
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/* arc4random_buf() that uses platform arc4random() */
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#if !defined(HAVE_ARC4RANDOM_BUF) && defined(HAVE_ARC4RANDOM)
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void
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arc4random_buf(void *_buf, size_t n)
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{
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size_t i;
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u_int32_t r = 0;
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char *buf = (char *)_buf;
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for (i = 0; i < n; i++) {
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if (i % 4 == 0)
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r = arc4random();
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buf[i] = r & 0xff;
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r >>= 8;
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}
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explicit_bzero(&r, sizeof(r));
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}
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#endif /* !defined(HAVE_ARC4RANDOM_BUF) && defined(HAVE_ARC4RANDOM) */
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