The Tor Browser: ipc/chromium/src/third_party/libevent/arc4random.c@6474c204b198 (annotated)

ipc/chromium/src/third_party/libevent/arc4random.c@6474c204b198 (annotated)

ipc/chromium/src/third_party/libevent/arc4random.c

Wed, 31 Dec 2014 06:09:35 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Wed, 31 Dec 2014 06:09:35 +0100
changeset 0: 6474c204b198
permissions: -rw-r--r--

Cloned upstream origin tor-browser at tor-browser-31.3.0esr-4.5-1-build1
revision ID fc1c9ff7c1b2defdbc039f12214767608f46423f for hacking purpose.

 /* 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

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ipc/chromium/src/third_party/libevent/arc4random.c@6474c204b198 (annotated)

ipc/chromium/src/third_party/libevent/arc4random.c