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 /* Portable arc4random.c based on arc4random.c from OpenBSD.

  * Portable version by Chris Davis, adapted for Libevent by Nick Mathewson

  * Copyright (c) 2010 Chris Davis, Niels Provos, and Nick Mathewson

  * Copyright (c) 2010-2012 Niels Provos and Nick Mathewson

  *

  * Note that in Libevent, this file isn't compiled directly.  Instead,

  * it's included from evutil_rand.c

  */

 /*

  * Copyright (c) 1996, David Mazieres <dm@uun.org>

  * Copyright (c) 2008, Damien Miller <djm@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.

  */

 /*

  * Arc4 random number generator for OpenBSD.

  *

  * This code is derived from section 17.1 of Applied Cryptography,

  * second edition, which describes a stream cipher allegedly

  * compatible with RSA Labs "RC4" cipher (the actual description of

  * which is a trade secret).  The same algorithm is used as a stream

  * cipher called "arcfour" in Tatu Ylonen's ssh package.

  *

  * Here the stream cipher has been modified always to include the time

  * when initializing the state.  That makes it impossible to

  * regenerate the same random sequence twice, so this can't be used

  * for encryption, but will generate good random numbers.

  *

  * RC4 is a registered trademark of RSA Laboratories.

  */

 #ifndef ARC4RANDOM_EXPORT

 #define ARC4RANDOM_EXPORT

 #endif

 #ifndef ARC4RANDOM_UINT32

 #define ARC4RANDOM_UINT32 uint32_t

 #endif

 #ifndef ARC4RANDOM_NO_INCLUDES

 #ifdef WIN32

 #include <wincrypt.h>

 #include <process.h>

 #else

 #include <fcntl.h>

 #include <unistd.h>

 #include <sys/param.h>

 #include <sys/time.h>

 #ifdef _EVENT_HAVE_SYS_SYSCTL_H

 #include <sys/sysctl.h>

 #endif

 #endif

 #include <limits.h>

 #include <stdlib.h>

 #include <string.h>

 #endif

 /* Add platform entropy 32 bytes (256 bits) at a time. */

 #define ADD_ENTROPY 32

 /* Re-seed from the platform RNG after generating this many bytes. */

 #define BYTES_BEFORE_RESEED 1600000

 struct arc4_stream {

 	unsigned char i;

 	unsigned char j;

 	unsigned char s[256];

 };

 #ifdef WIN32

 #define getpid _getpid

 #define pid_t int

 #endif

 static int rs_initialized;

 static struct arc4_stream rs;

 static pid_t arc4_stir_pid;

 static int arc4_count;

 static int arc4_seeded_ok;

 static inline unsigned char arc4_getbyte(void);

 static inline void

 arc4_init(void)

 {

 	int     n;

 	for (n = 0; n < 256; n++)

 		rs.s[n] = n;

 	rs.i = 0;

 	rs.j = 0;

 }

 static inline void

 arc4_addrandom(const unsigned char *dat, int datlen)

 {

 	int     n;

 	unsigned char si;

 	rs.i--;

 	for (n = 0; n < 256; n++) {

 		rs.i = (rs.i + 1);

 		si = rs.s[rs.i];

 		rs.j = (rs.j + si + dat[n % datlen]);

 		rs.s[rs.i] = rs.s[rs.j];

 		rs.s[rs.j] = si;

 	}

 	rs.j = rs.i;

 }

 #ifndef WIN32

 static ssize_t

 read_all(int fd, unsigned char *buf, size_t count)

 {

 	size_t numread = 0;

 	ssize_t result;

 	while (numread < count) {

 		result = read(fd, buf+numread, count-numread);

 		if (result<0)

 			return -1;

 		else if (result == 0)

 			break;

 		numread += result;

 	}

 	return (ssize_t)numread;

 }

 #endif

 #ifdef WIN32

 #define TRY_SEED_WIN32

 static int

 arc4_seed_win32(void)

 {

 	/* This is adapted from Tor's crypto_seed_rng() */

 	static int provider_set = 0;

 	static HCRYPTPROV provider;

 	unsigned char buf[ADD_ENTROPY];

 	if (!provider_set) {

 		if (!CryptAcquireContext(&provider, NULL, NULL, PROV_RSA_FULL,

 		    CRYPT_VERIFYCONTEXT)) {

 			if (GetLastError() != (DWORD)NTE_BAD_KEYSET)

 				return -1;

 		}

 		provider_set = 1;

 	}

 	if (!CryptGenRandom(provider, sizeof(buf), buf))

 		return -1;

 	arc4_addrandom(buf, sizeof(buf));

 	memset(buf, 0, sizeof(buf));

 	arc4_seeded_ok = 1;

 	return 0;

 }

 #endif

 #if defined(_EVENT_HAVE_SYS_SYSCTL_H) && defined(_EVENT_HAVE_SYSCTL)

 #if _EVENT_HAVE_DECL_CTL_KERN && _EVENT_HAVE_DECL_KERN_RANDOM && _EVENT_HAVE_DECL_RANDOM_UUID

 #define TRY_SEED_SYSCTL_LINUX

 static int

 arc4_seed_sysctl_linux(void)

 {

 	/* Based on code by William Ahern, this function tries to use the

 	 * RANDOM_UUID sysctl to get entropy from the kernel.  This can work

 	 * even if /dev/urandom is inaccessible for some reason (e.g., we're

 	 * running in a chroot). */

 	int mib[] = { CTL_KERN, KERN_RANDOM, RANDOM_UUID };

 	unsigned char buf[ADD_ENTROPY];

 	size_t len, n;

 	unsigned i;

 	int any_set;

 	memset(buf, 0, sizeof(buf));

 	for (len = 0; len < sizeof(buf); len += n) {

 		n = sizeof(buf) - len;

 		if (0 != sysctl(mib, 3, &buf[len], &n, NULL, 0))

 			return -1;

 	}

 	/* make sure that the buffer actually got set. */

 	for (i=0,any_set=0; i<sizeof(buf); ++i) {

 		any_set |= buf[i];

 	}

 	if (!any_set)

 		return -1;

 	arc4_addrandom(buf, sizeof(buf));

 	memset(buf, 0, sizeof(buf));

 	arc4_seeded_ok = 1;

 	return 0;

 }

 #endif

 #if _EVENT_HAVE_DECL_CTL_KERN && _EVENT_HAVE_DECL_KERN_ARND

 #define TRY_SEED_SYSCTL_BSD

 static int

 arc4_seed_sysctl_bsd(void)

 {

 	/* Based on code from William Ahern and from OpenBSD, this function

 	 * tries to use the KERN_ARND syscall to get entropy from the kernel.

 	 * This can work even if /dev/urandom is inaccessible for some reason

 	 * (e.g., we're running in a chroot). */

 	int mib[] = { CTL_KERN, KERN_ARND };

 	unsigned char buf[ADD_ENTROPY];

 	size_t len, n;

 	int i, any_set;

 	memset(buf, 0, sizeof(buf));

 	len = sizeof(buf);

 	if (sysctl(mib, 2, buf, &len, NULL, 0) == -1) {

 		for (len = 0; len < sizeof(buf); len += sizeof(unsigned)) {

 			n = sizeof(unsigned);

 			if (n + len > sizeof(buf))

 			    n = len - sizeof(buf);

 			if (sysctl(mib, 2, &buf[len], &n, NULL, 0) == -1)

 				return -1;

 		}

 	}

 	/* make sure that the buffer actually got set. */

 	for (i=any_set=0; i<sizeof(buf); ++i) {

 		any_set |= buf[i];

 	}

 	if (!any_set)

 		return -1;

 	arc4_addrandom(buf, sizeof(buf));

 	memset(buf, 0, sizeof(buf));

 	arc4_seeded_ok = 1;

 	return 0;

 }

 #endif

 #endif /* defined(_EVENT_HAVE_SYS_SYSCTL_H) */

 #ifdef __linux__

 #define TRY_SEED_PROC_SYS_KERNEL_RANDOM_UUID

 static int

 arc4_seed_proc_sys_kernel_random_uuid(void)

 {

 	/* Occasionally, somebody will make /proc/sys accessible in a chroot,

 	 * but not /dev/urandom.  Let's try /proc/sys/kernel/random/uuid.

 	 * Its format is stupid, so we need to decode it from hex.

 	 */

 	int fd;

 	char buf[128];

 	unsigned char entropy[64];

 	int bytes, n, i, nybbles;

 	for (bytes = 0; bytes<ADD_ENTROPY; ) {

 		fd = evutil_open_closeonexec("/proc/sys/kernel/random/uuid", O_RDONLY, 0);

 		if (fd < 0)

 			return -1;

 		n = read(fd, buf, sizeof(buf));

 		close(fd);

 		if (n<=0)

 			return -1;

 		memset(entropy, 0, sizeof(entropy));

 		for (i=nybbles=0; i<n; ++i) {

 			if (EVUTIL_ISXDIGIT(buf[i])) {

 				int nyb = evutil_hex_char_to_int(buf[i]);

 				if (nybbles & 1) {

 					entropy[nybbles/2] |= nyb;

 				} else {

 					entropy[nybbles/2] |= nyb<<4;

 				}

 				++nybbles;

 			}

 		}

 		if (nybbles < 2)

 			return -1;

 		arc4_addrandom(entropy, nybbles/2);

 		bytes += nybbles/2;

 	}

 	memset(entropy, 0, sizeof(entropy));

 	memset(buf, 0, sizeof(buf));

 	return 0;

 }

 #endif

 #ifndef WIN32

 #define TRY_SEED_URANDOM

 static int

 arc4_seed_urandom(void)

 {

 	/* This is adapted from Tor's crypto_seed_rng() */

 	static const char *filenames[] = {

 		"/dev/srandom", "/dev/urandom", "/dev/random", NULL

 	};

 	unsigned char buf[ADD_ENTROPY];

 	int fd, i;

 	size_t n;

 	for (i = 0; filenames[i]; ++i) {

 		fd = evutil_open_closeonexec(filenames[i], O_RDONLY, 0);

 		if (fd<0)

 			continue;

 		n = read_all(fd, buf, sizeof(buf));

 		close(fd);

 		if (n != sizeof(buf))

 			return -1;

 		arc4_addrandom(buf, sizeof(buf));

 		memset(buf, 0, sizeof(buf));

 		arc4_seeded_ok = 1;

 		return 0;

 	}

 	return -1;

 }

 #endif

 static int

 arc4_seed(void)

 {

 	int ok = 0;

 	/* We try every method that might work, and don't give up even if one

 	 * does seem to work.  There's no real harm in over-seeding, and if

 	 * one of these sources turns out to be broken, that would be bad. */

 #ifdef TRY_SEED_WIN32

 	if (0 == arc4_seed_win32())

 		ok = 1;

 #endif

 #ifdef TRY_SEED_URANDOM

 	if (0 == arc4_seed_urandom())

 		ok = 1;

 #endif

 #ifdef TRY_SEED_PROC_SYS_KERNEL_RANDOM_UUID

 	if (0 == arc4_seed_proc_sys_kernel_random_uuid())

 		ok = 1;

 #endif

 #ifdef TRY_SEED_SYSCTL_LINUX

 	/* Apparently Linux is deprecating sysctl, and spewing warning

 	 * messages when you try to use it. */

 	if (!ok && 0 == arc4_seed_sysctl_linux())

 		ok = 1;

 #endif

 #ifdef TRY_SEED_SYSCTL_BSD

 	if (0 == arc4_seed_sysctl_bsd())

 		ok = 1;

 #endif

 	return ok ? 0 : -1;

 }

 static int

 arc4_stir(void)

 {

 	int     i;

 	if (!rs_initialized) {

 		arc4_init();

 		rs_initialized = 1;

 	}

 	arc4_seed();

 	if (!arc4_seeded_ok)

 		return -1;

 	/*

 	 * Discard early keystream, as per recommendations in

 	 * "Weaknesses in the Key Scheduling Algorithm of RC4" by

 	 * Scott Fluhrer, Itsik Mantin, and Adi Shamir.

 	 * http://www.wisdom.weizmann.ac.il/~itsik/RC4/Papers/Rc4_ksa.ps

 	 *

 	 * Ilya Mironov's "(Not So) Random Shuffles of RC4" suggests that

 	 * we drop at least 2*256 bytes, with 12*256 as a conservative

 	 * value.

 	 *

 	 * RFC4345 says to drop 6*256.

 	 *

 	 * At least some versions of this code drop 4*256, in a mistaken

 	 * belief that "words" in the Fluhrer/Mantin/Shamir paper refers

 	 * to processor words.

 	 *

 	 * We add another sect to the cargo cult, and choose 12*256.

 	 */

 	for (i = 0; i < 12*256; i++)

 		(void)arc4_getbyte();

 	arc4_count = BYTES_BEFORE_RESEED;

 	return 0;

 }

 static void

 arc4_stir_if_needed(void)

 {

 	pid_t pid = getpid();

 	if (arc4_count <= 0 || !rs_initialized || arc4_stir_pid != pid)

 	{

 		arc4_stir_pid = pid;

 		arc4_stir();

 	}

 }

 static inline unsigned char

 arc4_getbyte(void)

 {

 	unsigned char si, sj;

 	rs.i = (rs.i + 1);

 	si = rs.s[rs.i];

 	rs.j = (rs.j + si);

 	sj = rs.s[rs.j];

 	rs.s[rs.i] = sj;

 	rs.s[rs.j] = si;

 	return (rs.s[(si + sj) & 0xff]);

 }

 static inline unsigned int

 arc4_getword(void)

 {

 	unsigned int val;

 	val = arc4_getbyte() << 24;

 	val |= arc4_getbyte() << 16;

 	val |= arc4_getbyte() << 8;

 	val |= arc4_getbyte();

 	return val;

 }

 #ifndef ARC4RANDOM_NOSTIR

 ARC4RANDOM_EXPORT int

 arc4random_stir(void)

 {

 	int val;

 	_ARC4_LOCK();

 	val = arc4_stir();

 	_ARC4_UNLOCK();

 	return val;

 }

 #endif

 #ifndef ARC4RANDOM_NOADDRANDOM

 ARC4RANDOM_EXPORT void

 arc4random_addrandom(const unsigned char *dat, int datlen)

 {

 	int j;

 	_ARC4_LOCK();

 	if (!rs_initialized)

 		arc4_stir();

 	for (j = 0; j < datlen; j += 256) {

 		/* arc4_addrandom() ignores all but the first 256 bytes of

 		 * its input.  We want to make sure to look at ALL the

 		 * data in 'dat', just in case the user is doing something

 		 * crazy like passing us all the files in /var/log. */

 		arc4_addrandom(dat + j, datlen - j);

 	}

 	_ARC4_UNLOCK();

 }

 #endif

 #ifndef ARC4RANDOM_NORANDOM

 ARC4RANDOM_EXPORT ARC4RANDOM_UINT32

 arc4random(void)

 {

 	ARC4RANDOM_UINT32 val;

 	_ARC4_LOCK();

 	arc4_count -= 4;

 	arc4_stir_if_needed();

 	val = arc4_getword();

 	_ARC4_UNLOCK();

 	return val;

 }

 #endif

 ARC4RANDOM_EXPORT void

 arc4random_buf(void *_buf, size_t n)

 {

 	unsigned char *buf = _buf;

 	_ARC4_LOCK();

 	arc4_stir_if_needed();

 	while (n--) {

 		if (--arc4_count <= 0)

 			arc4_stir();

 		buf[n] = arc4_getbyte();

 	}

 	_ARC4_UNLOCK();

 }

 #ifndef ARC4RANDOM_NOUNIFORM

 /*

  * 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.

  */

 ARC4RANDOM_EXPORT unsigned int

 arc4random_uniform(unsigned int upper_bound)

 {

 	ARC4RANDOM_UINT32 r, min;

 	if (upper_bound < 2)

 		return 0;

 #if (UINT_MAX > 0xffffffffUL)

 	min = 0x100000000UL % upper_bound;

 #else

 	/* Calculate (2**32 % upper_bound) avoiding 64-bit math */

 	if (upper_bound > 0x80000000)

 		min = 1 + ~upper_bound;		/* 2**32 - upper_bound */

 	else {

 		/* (2**32 - (x * 2)) % x == 2**32 % x when x <= 2**31 */

 		min = ((0xffffffff - (upper_bound * 2)) + 1) % upper_bound;

 	}

 #endif

 	/*

 	 * 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