339 lines
7.1 KiB
C
339 lines
7.1 KiB
C
/* OPENBSD ORIGINAL: lib/libc/crypto/arc4random.c */
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/* $OpenBSD: arc4random.c,v 1.25 2013/10/01 18:34:57 markus 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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*
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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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#include "includes.h"
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#include <sys/types.h>
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#include <fcntl.h>
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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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#ifdef HAVE_SYS_RANDOM_H
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# include <sys/random.h>
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#endif
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#ifndef HAVE_ARC4RANDOM
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#ifdef WITH_OPENSSL
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#include <openssl/rand.h>
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#include <openssl/err.h>
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#endif
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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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#ifdef __GNUC__
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#define inline __inline
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#else /* !__GNUC__ */
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#define inline
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#endif /* !__GNUC__ */
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/* OpenSSH isn't multithreaded */
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#define _ARC4_LOCK()
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#define _ARC4_UNLOCK()
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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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static int rs_initialized;
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static pid_t rs_stir_pid;
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static chacha_ctx rs; /* chacha context for random keystream */
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static u_char rs_buf[RSBUFSZ]; /* keystream blocks */
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static size_t rs_have; /* valid bytes at end of rs_buf */
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static size_t rs_count; /* bytes till reseed */
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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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chacha_keysetup(&rs, buf, KEYSZ * 8, 0);
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chacha_ivsetup(&rs, buf + KEYSZ);
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}
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#ifndef WITH_OPENSSL
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# ifndef SSH_RANDOM_DEV
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# define SSH_RANDOM_DEV "/dev/urandom"
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# endif /* SSH_RANDOM_DEV */
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static void
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getrnd(u_char *s, size_t len)
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{
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int fd;
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ssize_t r;
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size_t o = 0;
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#ifdef HAVE_GETRANDOM
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if ((r = getrandom(s, len, 0)) > 0 && (size_t)r == len)
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return;
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#endif /* HAVE_GETRANDOM */
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if ((fd = open(SSH_RANDOM_DEV, O_RDONLY)) == -1)
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fatal("Couldn't open %s: %s", SSH_RANDOM_DEV, strerror(errno));
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while (o < len) {
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r = read(fd, s + o, len - o);
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if (r < 0) {
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if (errno == EAGAIN || errno == EINTR ||
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errno == EWOULDBLOCK)
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continue;
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fatal("read %s: %s", SSH_RANDOM_DEV, strerror(errno));
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}
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o += r;
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}
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close(fd);
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}
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#endif /* WITH_OPENSSL */
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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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#ifdef WITH_OPENSSL
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if (RAND_bytes(rnd, sizeof(rnd)) <= 0)
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fatal("Couldn't obtain random bytes (error 0x%lx)",
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(unsigned long)ERR_get_error());
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#else
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getrnd(rnd, sizeof(rnd));
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#endif
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if (!rs_initialized) {
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rs_initialized = 1;
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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));
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/* invalidate rs_buf */
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rs_have = 0;
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memset(rs_buf, 0, RSBUFSZ);
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rs_count = 1600000;
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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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pid_t pid = getpid();
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if (rs_count <= len || !rs_initialized || rs_stir_pid != pid) {
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rs_stir_pid = pid;
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_rs_stir();
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} else
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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(rs_buf, 0,RSBUFSZ);
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#endif
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/* fill rs_buf with the keystream */
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chacha_encrypt_bytes(&rs, rs_buf, rs_buf, RSBUFSZ);
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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 = MIN(datlen, KEYSZ + IVSZ);
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for (i = 0; i < m; i++)
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rs_buf[i] ^= dat[i];
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}
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/* immediately reinit for backtracking resistance */
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_rs_init(rs_buf, KEYSZ + IVSZ);
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memset(rs_buf, 0, KEYSZ + IVSZ);
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rs_have = RSBUFSZ - 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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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_have > 0) {
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m = MIN(n, rs_have);
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memcpy(buf, rs_buf + RSBUFSZ - rs_have, m);
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memset(rs_buf + RSBUFSZ - rs_have, 0, m);
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buf += m;
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n -= m;
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rs_have -= m;
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}
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if (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(u_int32_t *val)
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{
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_rs_stir_if_needed(sizeof(*val));
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if (rs_have < sizeof(*val))
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_rs_rekey(NULL, 0);
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memcpy(val, rs_buf + RSBUFSZ - rs_have, sizeof(*val));
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memset(rs_buf + RSBUFSZ - rs_have, 0, sizeof(*val));
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rs_have -= sizeof(*val);
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return;
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}
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void
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arc4random_stir(void)
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{
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_ARC4_LOCK();
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_rs_stir();
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_ARC4_UNLOCK();
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}
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void
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arc4random_addrandom(u_char *dat, int datlen)
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{
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int m;
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_ARC4_LOCK();
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if (!rs_initialized)
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_rs_stir();
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while (datlen > 0) {
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m = MIN(datlen, KEYSZ + IVSZ);
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_rs_rekey(dat, m);
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dat += m;
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datlen -= m;
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}
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_ARC4_UNLOCK();
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}
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u_int32_t
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arc4random(void)
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{
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u_int32_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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/*
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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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# 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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#ifndef HAVE_ARC4RANDOM_UNIFORM
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/*
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* Calculate a uniformly distributed random number less than upper_bound
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* avoiding "modulo bias".
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*
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* Uniformity is achieved by generating new random numbers until the one
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* returned is outside the range [0, 2**32 % upper_bound). This
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* guarantees the selected random number will be inside
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* [2**32 % upper_bound, 2**32) which maps back to [0, upper_bound)
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* after reduction modulo upper_bound.
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*/
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u_int32_t
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arc4random_uniform(u_int32_t upper_bound)
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{
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u_int32_t r, min;
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if (upper_bound < 2)
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return 0;
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/* 2**32 % x == (2**32 - x) % x */
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min = -upper_bound % upper_bound;
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/*
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* This could theoretically loop forever but each retry has
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* p > 0.5 (worst case, usually far better) of selecting a
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* number inside the range we need, so it should rarely need
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* to re-roll.
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*/
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for (;;) {
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r = arc4random();
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if (r >= min)
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break;
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}
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return r % upper_bound;
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}
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#endif /* !HAVE_ARC4RANDOM_UNIFORM */
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#if 0
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/*-------- Test code for i386 --------*/
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#include <stdio.h>
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#include <machine/pctr.h>
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int
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main(int argc, char **argv)
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{
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const int iter = 1000000;
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int i;
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pctrval v;
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v = rdtsc();
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for (i = 0; i < iter; i++)
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arc4random();
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v = rdtsc() - v;
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v /= iter;
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printf("%qd cycles\n", v);
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exit(0);
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}
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#endif
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