michael@0: /* Portable arc4random.c based on arc4random.c from OpenBSD.
michael@0:  * Portable version by Chris Davis, adapted for Libevent by Nick Mathewson
michael@0:  * Copyright (c) 2010 Chris Davis, Niels Provos, and Nick Mathewson
michael@0:  * Copyright (c) 2010-2012 Niels Provos and Nick Mathewson
michael@0:  *
michael@0:  * Note that in Libevent, this file isn't compiled directly.  Instead,
michael@0:  * it's included from evutil_rand.c
michael@0:  */
michael@0: 
michael@0: /*
michael@0:  * Copyright (c) 1996, David Mazieres <dm@uun.org>
michael@0:  * Copyright (c) 2008, Damien Miller <djm@openbsd.org>
michael@0:  *
michael@0:  * Permission to use, copy, modify, and distribute this software for any
michael@0:  * purpose with or without fee is hereby granted, provided that the above
michael@0:  * copyright notice and this permission notice appear in all copies.
michael@0:  *
michael@0:  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
michael@0:  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
michael@0:  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
michael@0:  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
michael@0:  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
michael@0:  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
michael@0:  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
michael@0:  */
michael@0: 
michael@0: /*
michael@0:  * Arc4 random number generator for OpenBSD.
michael@0:  *
michael@0:  * This code is derived from section 17.1 of Applied Cryptography,
michael@0:  * second edition, which describes a stream cipher allegedly
michael@0:  * compatible with RSA Labs "RC4" cipher (the actual description of
michael@0:  * which is a trade secret).  The same algorithm is used as a stream
michael@0:  * cipher called "arcfour" in Tatu Ylonen's ssh package.
michael@0:  *
michael@0:  * Here the stream cipher has been modified always to include the time
michael@0:  * when initializing the state.  That makes it impossible to
michael@0:  * regenerate the same random sequence twice, so this can't be used
michael@0:  * for encryption, but will generate good random numbers.
michael@0:  *
michael@0:  * RC4 is a registered trademark of RSA Laboratories.
michael@0:  */
michael@0: 
michael@0: #ifndef ARC4RANDOM_EXPORT
michael@0: #define ARC4RANDOM_EXPORT
michael@0: #endif
michael@0: 
michael@0: #ifndef ARC4RANDOM_UINT32
michael@0: #define ARC4RANDOM_UINT32 uint32_t
michael@0: #endif
michael@0: 
michael@0: #ifndef ARC4RANDOM_NO_INCLUDES
michael@0: #ifdef WIN32
michael@0: #include <wincrypt.h>
michael@0: #include <process.h>
michael@0: #else
michael@0: #include <fcntl.h>
michael@0: #include <unistd.h>
michael@0: #include <sys/param.h>
michael@0: #include <sys/time.h>
michael@0: #ifdef _EVENT_HAVE_SYS_SYSCTL_H
michael@0: #include <sys/sysctl.h>
michael@0: #endif
michael@0: #endif
michael@0: #include <limits.h>
michael@0: #include <stdlib.h>
michael@0: #include <string.h>
michael@0: #endif
michael@0: 
michael@0: /* Add platform entropy 32 bytes (256 bits) at a time. */
michael@0: #define ADD_ENTROPY 32
michael@0: 
michael@0: /* Re-seed from the platform RNG after generating this many bytes. */
michael@0: #define BYTES_BEFORE_RESEED 1600000
michael@0: 
michael@0: struct arc4_stream {
michael@0: 	unsigned char i;
michael@0: 	unsigned char j;
michael@0: 	unsigned char s[256];
michael@0: };
michael@0: 
michael@0: #ifdef WIN32
michael@0: #define getpid _getpid
michael@0: #define pid_t int
michael@0: #endif
michael@0: 
michael@0: static int rs_initialized;
michael@0: static struct arc4_stream rs;
michael@0: static pid_t arc4_stir_pid;
michael@0: static int arc4_count;
michael@0: static int arc4_seeded_ok;
michael@0: 
michael@0: static inline unsigned char arc4_getbyte(void);
michael@0: 
michael@0: static inline void
michael@0: arc4_init(void)
michael@0: {
michael@0: 	int     n;
michael@0: 
michael@0: 	for (n = 0; n < 256; n++)
michael@0: 		rs.s[n] = n;
michael@0: 	rs.i = 0;
michael@0: 	rs.j = 0;
michael@0: }
michael@0: 
michael@0: static inline void
michael@0: arc4_addrandom(const unsigned char *dat, int datlen)
michael@0: {
michael@0: 	int     n;
michael@0: 	unsigned char si;
michael@0: 
michael@0: 	rs.i--;
michael@0: 	for (n = 0; n < 256; n++) {
michael@0: 		rs.i = (rs.i + 1);
michael@0: 		si = rs.s[rs.i];
michael@0: 		rs.j = (rs.j + si + dat[n % datlen]);
michael@0: 		rs.s[rs.i] = rs.s[rs.j];
michael@0: 		rs.s[rs.j] = si;
michael@0: 	}
michael@0: 	rs.j = rs.i;
michael@0: }
michael@0: 
michael@0: #ifndef WIN32
michael@0: static ssize_t
michael@0: read_all(int fd, unsigned char *buf, size_t count)
michael@0: {
michael@0: 	size_t numread = 0;
michael@0: 	ssize_t result;
michael@0: 
michael@0: 	while (numread < count) {
michael@0: 		result = read(fd, buf+numread, count-numread);
michael@0: 		if (result<0)
michael@0: 			return -1;
michael@0: 		else if (result == 0)
michael@0: 			break;
michael@0: 		numread += result;
michael@0: 	}
michael@0: 
michael@0: 	return (ssize_t)numread;
michael@0: }
michael@0: #endif
michael@0: 
michael@0: #ifdef WIN32
michael@0: #define TRY_SEED_WIN32
michael@0: static int
michael@0: arc4_seed_win32(void)
michael@0: {
michael@0: 	/* This is adapted from Tor's crypto_seed_rng() */
michael@0: 	static int provider_set = 0;
michael@0: 	static HCRYPTPROV provider;
michael@0: 	unsigned char buf[ADD_ENTROPY];
michael@0: 
michael@0: 	if (!provider_set) {
michael@0: 		if (!CryptAcquireContext(&provider, NULL, NULL, PROV_RSA_FULL,
michael@0: 		    CRYPT_VERIFYCONTEXT)) {
michael@0: 			if (GetLastError() != (DWORD)NTE_BAD_KEYSET)
michael@0: 				return -1;
michael@0: 		}
michael@0: 		provider_set = 1;
michael@0: 	}
michael@0: 	if (!CryptGenRandom(provider, sizeof(buf), buf))
michael@0: 		return -1;
michael@0: 	arc4_addrandom(buf, sizeof(buf));
michael@0: 	memset(buf, 0, sizeof(buf));
michael@0: 	arc4_seeded_ok = 1;
michael@0: 	return 0;
michael@0: }
michael@0: #endif
michael@0: 
michael@0: #if defined(_EVENT_HAVE_SYS_SYSCTL_H) && defined(_EVENT_HAVE_SYSCTL)
michael@0: #if _EVENT_HAVE_DECL_CTL_KERN && _EVENT_HAVE_DECL_KERN_RANDOM && _EVENT_HAVE_DECL_RANDOM_UUID
michael@0: #define TRY_SEED_SYSCTL_LINUX
michael@0: static int
michael@0: arc4_seed_sysctl_linux(void)
michael@0: {
michael@0: 	/* Based on code by William Ahern, this function tries to use the
michael@0: 	 * RANDOM_UUID sysctl to get entropy from the kernel.  This can work
michael@0: 	 * even if /dev/urandom is inaccessible for some reason (e.g., we're
michael@0: 	 * running in a chroot). */
michael@0: 	int mib[] = { CTL_KERN, KERN_RANDOM, RANDOM_UUID };
michael@0: 	unsigned char buf[ADD_ENTROPY];
michael@0: 	size_t len, n;
michael@0: 	unsigned i;
michael@0: 	int any_set;
michael@0: 
michael@0: 	memset(buf, 0, sizeof(buf));
michael@0: 
michael@0: 	for (len = 0; len < sizeof(buf); len += n) {
michael@0: 		n = sizeof(buf) - len;
michael@0: 
michael@0: 		if (0 != sysctl(mib, 3, &buf[len], &n, NULL, 0))
michael@0: 			return -1;
michael@0: 	}
michael@0: 	/* make sure that the buffer actually got set. */
michael@0: 	for (i=0,any_set=0; i<sizeof(buf); ++i) {
michael@0: 		any_set |= buf[i];
michael@0: 	}
michael@0: 	if (!any_set)
michael@0: 		return -1;
michael@0: 
michael@0: 	arc4_addrandom(buf, sizeof(buf));
michael@0: 	memset(buf, 0, sizeof(buf));
michael@0: 	arc4_seeded_ok = 1;
michael@0: 	return 0;
michael@0: }
michael@0: #endif
michael@0: 
michael@0: #if _EVENT_HAVE_DECL_CTL_KERN && _EVENT_HAVE_DECL_KERN_ARND
michael@0: #define TRY_SEED_SYSCTL_BSD
michael@0: static int
michael@0: arc4_seed_sysctl_bsd(void)
michael@0: {
michael@0: 	/* Based on code from William Ahern and from OpenBSD, this function
michael@0: 	 * tries to use the KERN_ARND syscall to get entropy from the kernel.
michael@0: 	 * This can work even if /dev/urandom is inaccessible for some reason
michael@0: 	 * (e.g., we're running in a chroot). */
michael@0: 	int mib[] = { CTL_KERN, KERN_ARND };
michael@0: 	unsigned char buf[ADD_ENTROPY];
michael@0: 	size_t len, n;
michael@0: 	int i, any_set;
michael@0: 
michael@0: 	memset(buf, 0, sizeof(buf));
michael@0: 
michael@0: 	len = sizeof(buf);
michael@0: 	if (sysctl(mib, 2, buf, &len, NULL, 0) == -1) {
michael@0: 		for (len = 0; len < sizeof(buf); len += sizeof(unsigned)) {
michael@0: 			n = sizeof(unsigned);
michael@0: 			if (n + len > sizeof(buf))
michael@0: 			    n = len - sizeof(buf);
michael@0: 			if (sysctl(mib, 2, &buf[len], &n, NULL, 0) == -1)
michael@0: 				return -1;
michael@0: 		}
michael@0: 	}
michael@0: 	/* make sure that the buffer actually got set. */
michael@0: 	for (i=any_set=0; i<sizeof(buf); ++i) {
michael@0: 		any_set |= buf[i];
michael@0: 	}
michael@0: 	if (!any_set)
michael@0: 		return -1;
michael@0: 
michael@0: 	arc4_addrandom(buf, sizeof(buf));
michael@0: 	memset(buf, 0, sizeof(buf));
michael@0: 	arc4_seeded_ok = 1;
michael@0: 	return 0;
michael@0: }
michael@0: #endif
michael@0: #endif /* defined(_EVENT_HAVE_SYS_SYSCTL_H) */
michael@0: 
michael@0: #ifdef __linux__
michael@0: #define TRY_SEED_PROC_SYS_KERNEL_RANDOM_UUID
michael@0: static int
michael@0: arc4_seed_proc_sys_kernel_random_uuid(void)
michael@0: {
michael@0: 	/* Occasionally, somebody will make /proc/sys accessible in a chroot,
michael@0: 	 * but not /dev/urandom.  Let's try /proc/sys/kernel/random/uuid.
michael@0: 	 * Its format is stupid, so we need to decode it from hex.
michael@0: 	 */
michael@0: 	int fd;
michael@0: 	char buf[128];
michael@0: 	unsigned char entropy[64];
michael@0: 	int bytes, n, i, nybbles;
michael@0: 	for (bytes = 0; bytes<ADD_ENTROPY; ) {
michael@0: 		fd = evutil_open_closeonexec("/proc/sys/kernel/random/uuid", O_RDONLY, 0);
michael@0: 		if (fd < 0)
michael@0: 			return -1;
michael@0: 		n = read(fd, buf, sizeof(buf));
michael@0: 		close(fd);
michael@0: 		if (n<=0)
michael@0: 			return -1;
michael@0: 		memset(entropy, 0, sizeof(entropy));
michael@0: 		for (i=nybbles=0; i<n; ++i) {
michael@0: 			if (EVUTIL_ISXDIGIT(buf[i])) {
michael@0: 				int nyb = evutil_hex_char_to_int(buf[i]);
michael@0: 				if (nybbles & 1) {
michael@0: 					entropy[nybbles/2] |= nyb;
michael@0: 				} else {
michael@0: 					entropy[nybbles/2] |= nyb<<4;
michael@0: 				}
michael@0: 				++nybbles;
michael@0: 			}
michael@0: 		}
michael@0: 		if (nybbles < 2)
michael@0: 			return -1;
michael@0: 		arc4_addrandom(entropy, nybbles/2);
michael@0: 		bytes += nybbles/2;
michael@0: 	}
michael@0: 	memset(entropy, 0, sizeof(entropy));
michael@0: 	memset(buf, 0, sizeof(buf));
michael@0: 	return 0;
michael@0: }
michael@0: #endif
michael@0: 
michael@0: #ifndef WIN32
michael@0: #define TRY_SEED_URANDOM
michael@0: static int
michael@0: arc4_seed_urandom(void)
michael@0: {
michael@0: 	/* This is adapted from Tor's crypto_seed_rng() */
michael@0: 	static const char *filenames[] = {
michael@0: 		"/dev/srandom", "/dev/urandom", "/dev/random", NULL
michael@0: 	};
michael@0: 	unsigned char buf[ADD_ENTROPY];
michael@0: 	int fd, i;
michael@0: 	size_t n;
michael@0: 
michael@0: 	for (i = 0; filenames[i]; ++i) {
michael@0: 		fd = evutil_open_closeonexec(filenames[i], O_RDONLY, 0);
michael@0: 		if (fd<0)
michael@0: 			continue;
michael@0: 		n = read_all(fd, buf, sizeof(buf));
michael@0: 		close(fd);
michael@0: 		if (n != sizeof(buf))
michael@0: 			return -1;
michael@0: 		arc4_addrandom(buf, sizeof(buf));
michael@0: 		memset(buf, 0, sizeof(buf));
michael@0: 		arc4_seeded_ok = 1;
michael@0: 		return 0;
michael@0: 	}
michael@0: 
michael@0: 	return -1;
michael@0: }
michael@0: #endif
michael@0: 
michael@0: static int
michael@0: arc4_seed(void)
michael@0: {
michael@0: 	int ok = 0;
michael@0: 	/* We try every method that might work, and don't give up even if one
michael@0: 	 * does seem to work.  There's no real harm in over-seeding, and if
michael@0: 	 * one of these sources turns out to be broken, that would be bad. */
michael@0: #ifdef TRY_SEED_WIN32
michael@0: 	if (0 == arc4_seed_win32())
michael@0: 		ok = 1;
michael@0: #endif
michael@0: #ifdef TRY_SEED_URANDOM
michael@0: 	if (0 == arc4_seed_urandom())
michael@0: 		ok = 1;
michael@0: #endif
michael@0: #ifdef TRY_SEED_PROC_SYS_KERNEL_RANDOM_UUID
michael@0: 	if (0 == arc4_seed_proc_sys_kernel_random_uuid())
michael@0: 		ok = 1;
michael@0: #endif
michael@0: #ifdef TRY_SEED_SYSCTL_LINUX
michael@0: 	/* Apparently Linux is deprecating sysctl, and spewing warning
michael@0: 	 * messages when you try to use it. */
michael@0: 	if (!ok && 0 == arc4_seed_sysctl_linux())
michael@0: 		ok = 1;
michael@0: #endif
michael@0: #ifdef TRY_SEED_SYSCTL_BSD
michael@0: 	if (0 == arc4_seed_sysctl_bsd())
michael@0: 		ok = 1;
michael@0: #endif
michael@0: 	return ok ? 0 : -1;
michael@0: }
michael@0: 
michael@0: static int
michael@0: arc4_stir(void)
michael@0: {
michael@0: 	int     i;
michael@0: 
michael@0: 	if (!rs_initialized) {
michael@0: 		arc4_init();
michael@0: 		rs_initialized = 1;
michael@0: 	}
michael@0: 
michael@0: 	arc4_seed();
michael@0: 	if (!arc4_seeded_ok)
michael@0: 		return -1;
michael@0: 
michael@0: 	/*
michael@0: 	 * Discard early keystream, as per recommendations in
michael@0: 	 * "Weaknesses in the Key Scheduling Algorithm of RC4" by
michael@0: 	 * Scott Fluhrer, Itsik Mantin, and Adi Shamir.
michael@0: 	 * http://www.wisdom.weizmann.ac.il/~itsik/RC4/Papers/Rc4_ksa.ps
michael@0: 	 *
michael@0: 	 * Ilya Mironov's "(Not So) Random Shuffles of RC4" suggests that
michael@0: 	 * we drop at least 2*256 bytes, with 12*256 as a conservative
michael@0: 	 * value.
michael@0: 	 *
michael@0: 	 * RFC4345 says to drop 6*256.
michael@0: 	 *
michael@0: 	 * At least some versions of this code drop 4*256, in a mistaken
michael@0: 	 * belief that "words" in the Fluhrer/Mantin/Shamir paper refers
michael@0: 	 * to processor words.
michael@0: 	 *
michael@0: 	 * We add another sect to the cargo cult, and choose 12*256.
michael@0: 	 */
michael@0: 	for (i = 0; i < 12*256; i++)
michael@0: 		(void)arc4_getbyte();
michael@0: 	arc4_count = BYTES_BEFORE_RESEED;
michael@0: 
michael@0: 	return 0;
michael@0: }
michael@0: 
michael@0: 
michael@0: static void
michael@0: arc4_stir_if_needed(void)
michael@0: {
michael@0: 	pid_t pid = getpid();
michael@0: 
michael@0: 	if (arc4_count <= 0 || !rs_initialized || arc4_stir_pid != pid)
michael@0: 	{
michael@0: 		arc4_stir_pid = pid;
michael@0: 		arc4_stir();
michael@0: 	}
michael@0: }
michael@0: 
michael@0: static inline unsigned char
michael@0: arc4_getbyte(void)
michael@0: {
michael@0: 	unsigned char si, sj;
michael@0: 
michael@0: 	rs.i = (rs.i + 1);
michael@0: 	si = rs.s[rs.i];
michael@0: 	rs.j = (rs.j + si);
michael@0: 	sj = rs.s[rs.j];
michael@0: 	rs.s[rs.i] = sj;
michael@0: 	rs.s[rs.j] = si;
michael@0: 	return (rs.s[(si + sj) & 0xff]);
michael@0: }
michael@0: 
michael@0: static inline unsigned int
michael@0: arc4_getword(void)
michael@0: {
michael@0: 	unsigned int val;
michael@0: 
michael@0: 	val = arc4_getbyte() << 24;
michael@0: 	val |= arc4_getbyte() << 16;
michael@0: 	val |= arc4_getbyte() << 8;
michael@0: 	val |= arc4_getbyte();
michael@0: 
michael@0: 	return val;
michael@0: }
michael@0: 
michael@0: #ifndef ARC4RANDOM_NOSTIR
michael@0: ARC4RANDOM_EXPORT int
michael@0: arc4random_stir(void)
michael@0: {
michael@0: 	int val;
michael@0: 	_ARC4_LOCK();
michael@0: 	val = arc4_stir();
michael@0: 	_ARC4_UNLOCK();
michael@0: 	return val;
michael@0: }
michael@0: #endif
michael@0: 
michael@0: #ifndef ARC4RANDOM_NOADDRANDOM
michael@0: ARC4RANDOM_EXPORT void
michael@0: arc4random_addrandom(const unsigned char *dat, int datlen)
michael@0: {
michael@0: 	int j;
michael@0: 	_ARC4_LOCK();
michael@0: 	if (!rs_initialized)
michael@0: 		arc4_stir();
michael@0: 	for (j = 0; j < datlen; j += 256) {
michael@0: 		/* arc4_addrandom() ignores all but the first 256 bytes of
michael@0: 		 * its input.  We want to make sure to look at ALL the
michael@0: 		 * data in 'dat', just in case the user is doing something
michael@0: 		 * crazy like passing us all the files in /var/log. */
michael@0: 		arc4_addrandom(dat + j, datlen - j);
michael@0: 	}
michael@0: 	_ARC4_UNLOCK();
michael@0: }
michael@0: #endif
michael@0: 
michael@0: #ifndef ARC4RANDOM_NORANDOM
michael@0: ARC4RANDOM_EXPORT ARC4RANDOM_UINT32
michael@0: arc4random(void)
michael@0: {
michael@0: 	ARC4RANDOM_UINT32 val;
michael@0: 	_ARC4_LOCK();
michael@0: 	arc4_count -= 4;
michael@0: 	arc4_stir_if_needed();
michael@0: 	val = arc4_getword();
michael@0: 	_ARC4_UNLOCK();
michael@0: 	return val;
michael@0: }
michael@0: #endif
michael@0: 
michael@0: ARC4RANDOM_EXPORT void
michael@0: arc4random_buf(void *_buf, size_t n)
michael@0: {
michael@0: 	unsigned char *buf = _buf;
michael@0: 	_ARC4_LOCK();
michael@0: 	arc4_stir_if_needed();
michael@0: 	while (n--) {
michael@0: 		if (--arc4_count <= 0)
michael@0: 			arc4_stir();
michael@0: 		buf[n] = arc4_getbyte();
michael@0: 	}
michael@0: 	_ARC4_UNLOCK();
michael@0: }
michael@0: 
michael@0: #ifndef ARC4RANDOM_NOUNIFORM
michael@0: /*
michael@0:  * Calculate a uniformly distributed random number less than upper_bound
michael@0:  * avoiding "modulo bias".
michael@0:  *
michael@0:  * Uniformity is achieved by generating new random numbers until the one
michael@0:  * returned is outside the range [0, 2**32 % upper_bound).  This
michael@0:  * guarantees the selected random number will be inside
michael@0:  * [2**32 % upper_bound, 2**32) which maps back to [0, upper_bound)
michael@0:  * after reduction modulo upper_bound.
michael@0:  */
michael@0: ARC4RANDOM_EXPORT unsigned int
michael@0: arc4random_uniform(unsigned int upper_bound)
michael@0: {
michael@0: 	ARC4RANDOM_UINT32 r, min;
michael@0: 
michael@0: 	if (upper_bound < 2)
michael@0: 		return 0;
michael@0: 
michael@0: #if (UINT_MAX > 0xffffffffUL)
michael@0: 	min = 0x100000000UL % upper_bound;
michael@0: #else
michael@0: 	/* Calculate (2**32 % upper_bound) avoiding 64-bit math */
michael@0: 	if (upper_bound > 0x80000000)
michael@0: 		min = 1 + ~upper_bound;		/* 2**32 - upper_bound */
michael@0: 	else {
michael@0: 		/* (2**32 - (x * 2)) % x == 2**32 % x when x <= 2**31 */
michael@0: 		min = ((0xffffffff - (upper_bound * 2)) + 1) % upper_bound;
michael@0: 	}
michael@0: #endif
michael@0: 
michael@0: 	/*
michael@0: 	 * This could theoretically loop forever but each retry has
michael@0: 	 * p > 0.5 (worst case, usually far better) of selecting a
michael@0: 	 * number inside the range we need, so it should rarely need
michael@0: 	 * to re-roll.
michael@0: 	 */
michael@0: 	for (;;) {
michael@0: 		r = arc4random();
michael@0: 		if (r >= min)
michael@0: 			break;
michael@0: 	}
michael@0: 
michael@0: 	return r % upper_bound;
michael@0: }
michael@0: #endif