openbsd-compat/arc4random.c - platform/external/openssh - Gitiles

 /* OPENBSD ORIGINAL: lib/libc/crypto/arc4random.c */

 /*	$OpenBSD: arc4random.c,v 1.25 2013/10/01 18:34:57 markus 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 "includes.h"

 #include <sys/types.h>

 #include <fcntl.h>
 #include <stdlib.h>
 #include <string.h>
 #include <unistd.h>

 #ifndef HAVE_ARC4RANDOM

 #ifdef WITH_OPENSSL
 #include <openssl/rand.h>
 #include <openssl/err.h>
 #endif

 #include "log.h"

 #define KEYSTREAM_ONLY
 #include "chacha_private.h"

 #ifdef __GNUC__
 #define inline __inline
 #else				/* !__GNUC__ */
 #define inline
 #endif				/* !__GNUC__ */

 /* OpenSSH isn't multithreaded */
 #define _ARC4_LOCK()
 #define _ARC4_UNLOCK()

 #define KEYSZ	32
 #define IVSZ	8
 #define BLOCKSZ	64
 #define RSBUFSZ	(16*BLOCKSZ)
 static int rs_initialized;
 static pid_t rs_stir_pid;
 static chacha_ctx rs;		/* chacha context for random keystream */
 static u_char rs_buf[RSBUFSZ];	/* keystream blocks */
 static size_t rs_have;		/* valid bytes at end of rs_buf */
 static size_t rs_count;		/* bytes till reseed */

 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;
 	chacha_keysetup(&rs, buf, KEYSZ * 8, 0);
 	chacha_ivsetup(&rs, buf + KEYSZ);
 }

 #ifndef WITH_OPENSSL
 #define SSH_RANDOM_DEV "/dev/urandom"
 /* XXX use getrandom() if supported on Linux */
 static void
 getrnd(u_char *s, size_t len)
 {
 	int fd;
 	ssize_t r;
 	size_t o = 0;

 	if ((fd = open(SSH_RANDOM_DEV, O_RDONLY)) == -1)
 		fatal("Couldn't open %s: %s", SSH_RANDOM_DEV, strerror(errno));
 	while (o < len) {
 		r = read(fd, s + o, len - o);
 		if (r < 0) {
 			if (errno == EAGAIN || errno == EINTR ||
 			    errno == EWOULDBLOCK)
 				continue;
 			fatal("read %s: %s", SSH_RANDOM_DEV, strerror(errno));
 		}
 		o += r;
 	}
 	close(fd);
 }
 #endif

 static void
 _rs_stir(void)
 {
 	u_char rnd[KEYSZ + IVSZ];

 #ifdef WITH_OPENSSL
 	if (RAND_bytes(rnd, sizeof(rnd)) <= 0)
 		fatal("Couldn't obtain random bytes (error 0x%lx)",
 		    (unsigned long)ERR_get_error());
 #else
 	getrnd(rnd, sizeof(rnd));
 #endif

 	if (!rs_initialized) {
 		rs_initialized = 1;
 		_rs_init(rnd, sizeof(rnd));
 	} else
 		_rs_rekey(rnd, sizeof(rnd));
 	explicit_bzero(rnd, sizeof(rnd));

 	/* invalidate rs_buf */
 	rs_have = 0;
 	memset(rs_buf, 0, RSBUFSZ);

 	rs_count = 1600000;
 }

 static inline void
 _rs_stir_if_needed(size_t len)
 {
 	pid_t pid = getpid();

 	if (rs_count <= len || !rs_initialized || rs_stir_pid != pid) {
 		rs_stir_pid = pid;
 		_rs_stir();
 	} else
 		rs_count -= len;
 }

 static inline void
 _rs_rekey(u_char *dat, size_t datlen)
 {
 #ifndef KEYSTREAM_ONLY
 	memset(rs_buf, 0,RSBUFSZ);
 #endif
 	/* fill rs_buf with the keystream */
 	chacha_encrypt_bytes(&rs, rs_buf, rs_buf, RSBUFSZ);
 	/* mix in optional user provided data */
 	if (dat) {
 		size_t i, m;

 		m = MIN(datlen, KEYSZ + IVSZ);
 		for (i = 0; i < m; i++)
 			rs_buf[i] ^= dat[i];
 	}
 	/* immediately reinit for backtracking resistance */
 	_rs_init(rs_buf, KEYSZ + IVSZ);
 	memset(rs_buf, 0, KEYSZ + IVSZ);
 	rs_have = RSBUFSZ - KEYSZ - IVSZ;
 }

 static inline void
 _rs_random_buf(void *_buf, size_t n)
 {
 	u_char *buf = (u_char *)_buf;
 	size_t m;

 	_rs_stir_if_needed(n);
 	while (n > 0) {
 		if (rs_have > 0) {
 			m = MIN(n, rs_have);
 			memcpy(buf, rs_buf + RSBUFSZ - rs_have, m);
 			memset(rs_buf + RSBUFSZ - rs_have, 0, m);
 			buf += m;
 			n -= m;
 			rs_have -= m;
 		}
 		if (rs_have == 0)
 			_rs_rekey(NULL, 0);
 	}
 }

 static inline void
 _rs_random_u32(u_int32_t *val)
 {
 	_rs_stir_if_needed(sizeof(*val));
 	if (rs_have < sizeof(*val))
 		_rs_rekey(NULL, 0);
 	memcpy(val, rs_buf + RSBUFSZ - rs_have, sizeof(*val));
 	memset(rs_buf + RSBUFSZ - rs_have, 0, sizeof(*val));
 	rs_have -= sizeof(*val);
 	return;
 }

 void
 arc4random_stir(void)
 {
 	_ARC4_LOCK();
 	_rs_stir();
 	_ARC4_UNLOCK();
 }

 void
 arc4random_addrandom(u_char *dat, int datlen)
 {
 	int m;

 	_ARC4_LOCK();
 	if (!rs_initialized)
 		_rs_stir();
 	while (datlen > 0) {
 		m = MIN(datlen, KEYSZ + IVSZ);
 		_rs_rekey(dat, m);
 		dat += m;
 		datlen -= m;
 	}
 	_ARC4_UNLOCK();
 }

 u_int32_t
 arc4random(void)
 {
 	u_int32_t val;

 	_ARC4_LOCK();
 	_rs_random_u32(&val);
 	_ARC4_UNLOCK();
 	return val;
 }

 /*
  * 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();
 }
 # 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) */

 #ifndef HAVE_ARC4RANDOM_UNIFORM
 /*
  * 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.
  */
 u_int32_t
 arc4random_uniform(u_int32_t upper_bound)
 {
 	u_int32_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 = arc4random();
 		if (r >= min)
 			break;
 	}

 	return r % upper_bound;
 }
 #endif /* !HAVE_ARC4RANDOM_UNIFORM */

 #if 0
 /*-------- Test code for i386 --------*/
 #include <stdio.h>
 #include <machine/pctr.h>
 int
 main(int argc, char **argv)
 {
 	const int iter = 1000000;
 	int     i;
 	pctrval v;

 	v = rdtsc();
 	for (i = 0; i < iter; i++)
 		arc4random();
 	v = rdtsc() - v;
 	v /= iter;

 	printf("%qd cycles\n", v);
 	exit(0);
 }
 #endif
	/* OPENBSD ORIGINAL: lib/libc/crypto/arc4random.c */

	/* $OpenBSD: arc4random.c,v 1.25 2013/10/01 18:34:57 markus 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 "includes.h"

	#include <sys/types.h>

	#include <fcntl.h>
	#include <stdlib.h>
	#include <string.h>
	#include <unistd.h>

	#ifndef HAVE_ARC4RANDOM

	#ifdef WITH_OPENSSL
	#include <openssl/rand.h>
	#include <openssl/err.h>
	#endif

	#include "log.h"

	#define KEYSTREAM_ONLY
	#include "chacha_private.h"

	#ifdef __GNUC__
	#define inline __inline
	#else /* !__GNUC__ */
	#define inline
	#endif /* !__GNUC__ */

	/* OpenSSH isn't multithreaded */
	#define _ARC4_LOCK()
	#define _ARC4_UNLOCK()

	#define KEYSZ 32
	#define IVSZ 8
	#define BLOCKSZ 64
	#define RSBUFSZ (16*BLOCKSZ)
	static int rs_initialized;
	static pid_t rs_stir_pid;
	static chacha_ctx rs; /* chacha context for random keystream */
	static u_char rs_buf[RSBUFSZ]; /* keystream blocks */
	static size_t rs_have; /* valid bytes at end of rs_buf */
	static size_t rs_count; /* bytes till reseed */

	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;
	chacha_keysetup(&rs, buf, KEYSZ * 8, 0);
	chacha_ivsetup(&rs, buf + KEYSZ);
	}

	#ifndef WITH_OPENSSL
	#define SSH_RANDOM_DEV "/dev/urandom"
	/* XXX use getrandom() if supported on Linux */
	static void
	getrnd(u_char *s, size_t len)
	{
	int fd;
	ssize_t r;
	size_t o = 0;

	if ((fd = open(SSH_RANDOM_DEV, O_RDONLY)) == -1)
	fatal("Couldn't open %s: %s", SSH_RANDOM_DEV, strerror(errno));
	while (o < len) {
	r = read(fd, s + o, len - o);
	if (r < 0) {
	if (errno == EAGAIN \|\| errno == EINTR \|\|
	errno == EWOULDBLOCK)
	continue;
	fatal("read %s: %s", SSH_RANDOM_DEV, strerror(errno));
	}
	o += r;
	}
	close(fd);
	}
	#endif

	static void
	_rs_stir(void)
	{
	u_char rnd[KEYSZ + IVSZ];

	#ifdef WITH_OPENSSL
	if (RAND_bytes(rnd, sizeof(rnd)) <= 0)
	fatal("Couldn't obtain random bytes (error 0x%lx)",
	(unsigned long)ERR_get_error());
	#else
	getrnd(rnd, sizeof(rnd));
	#endif

	if (!rs_initialized) {
	rs_initialized = 1;
	_rs_init(rnd, sizeof(rnd));
	} else
	_rs_rekey(rnd, sizeof(rnd));
	explicit_bzero(rnd, sizeof(rnd));

	/* invalidate rs_buf */
	rs_have = 0;
	memset(rs_buf, 0, RSBUFSZ);

	rs_count = 1600000;
	}

	static inline void
	_rs_stir_if_needed(size_t len)
	{
	pid_t pid = getpid();

	if (rs_count <= len \|\| !rs_initialized \|\| rs_stir_pid != pid) {
	rs_stir_pid = pid;
	_rs_stir();
	} else
	rs_count -= len;
	}

	static inline void
	_rs_rekey(u_char *dat, size_t datlen)
	{
	#ifndef KEYSTREAM_ONLY
	memset(rs_buf, 0,RSBUFSZ);
	#endif
	/* fill rs_buf with the keystream */
	chacha_encrypt_bytes(&rs, rs_buf, rs_buf, RSBUFSZ);
	/* mix in optional user provided data */
	if (dat) {
	size_t i, m;

	m = MIN(datlen, KEYSZ + IVSZ);
	for (i = 0; i < m; i++)
	rs_buf[i] ^= dat[i];
	}
	/* immediately reinit for backtracking resistance */
	_rs_init(rs_buf, KEYSZ + IVSZ);
	memset(rs_buf, 0, KEYSZ + IVSZ);
	rs_have = RSBUFSZ - KEYSZ - IVSZ;
	}

	static inline void
	_rs_random_buf(void *_buf, size_t n)
	{
	u_char buf = (u_char )_buf;
	size_t m;

	_rs_stir_if_needed(n);
	while (n > 0) {
	if (rs_have > 0) {
	m = MIN(n, rs_have);
	memcpy(buf, rs_buf + RSBUFSZ - rs_have, m);
	memset(rs_buf + RSBUFSZ - rs_have, 0, m);
	buf += m;
	n -= m;
	rs_have -= m;
	}
	if (rs_have == 0)
	_rs_rekey(NULL, 0);
	}
	}

	static inline void
	_rs_random_u32(u_int32_t *val)
	{
	_rs_stir_if_needed(sizeof(*val));
	if (rs_have < sizeof(*val))
	_rs_rekey(NULL, 0);
	memcpy(val, rs_buf + RSBUFSZ - rs_have, sizeof(*val));
	memset(rs_buf + RSBUFSZ - rs_have, 0, sizeof(*val));
	rs_have -= sizeof(*val);
	return;
	}

	void
	arc4random_stir(void)
	{
	_ARC4_LOCK();
	_rs_stir();
	_ARC4_UNLOCK();
	}

	void
	arc4random_addrandom(u_char *dat, int datlen)
	{
	int m;

	_ARC4_LOCK();
	if (!rs_initialized)
	_rs_stir();
	while (datlen > 0) {
	m = MIN(datlen, KEYSZ + IVSZ);
	_rs_rekey(dat, m);
	dat += m;
	datlen -= m;
	}
	_ARC4_UNLOCK();
	}

	u_int32_t
	arc4random(void)
	{
	u_int32_t val;

	_ARC4_LOCK();
	_rs_random_u32(&val);
	_ARC4_UNLOCK();
	return val;
	}

	/*
	* 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();
	}
	# 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) */

	#ifndef HAVE_ARC4RANDOM_UNIFORM
	/*
	* 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
	* [232 % upper_bound, 232) which maps back to [0, upper_bound)
	* after reduction modulo upper_bound.
	*/
	u_int32_t
	arc4random_uniform(u_int32_t upper_bound)
	{
	u_int32_t r, min;

	if (upper_bound < 2)
	return 0;

	/* 232 % x == (232 - 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 = arc4random();
	if (r >= min)
	break;
	}

	return r % upper_bound;
	}
	#endif /* !HAVE_ARC4RANDOM_UNIFORM */

	#if 0
	/-------- Test code for i386 --------/
	#include <stdio.h>
	#include <machine/pctr.h>
	int
	main(int argc, char **argv)
	{
	const int iter = 1000000;
	int i;
	pctrval v;

	v = rdtsc();
	for (i = 0; i < iter; i++)
	arc4random();
	v = rdtsc() - v;
	v /= iter;

	printf("%qd cycles\n", v);
	exit(0);
	}
	#endif