Edit
kc3-lang/libevent/arc4random.c
Nick Mathewson
- arc4random.c
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/* Portable arc4random.c based on arc4random.c from OpenBSD. * Portable version by Chris Davis, adapted for Libevent by 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> #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 /* This is adapted from Tor's crypto_seed_rng() */ static int arc4_seed(void) { unsigned char buf[ADD_ENTROPY]; /* local variables */ #ifdef WIN32 static int provider_set = 0; static HCRYPTPROV provider; #else static const char *filenames[] = { "/dev/srandom", "/dev/urandom", "/dev/random", NULL }; int fd, i; size_t n; #endif #ifdef WIN32 if (!provider_set) { if (!CryptAcquireContext(&provider, NULL, NULL, PROV_RSA_FULL, CRYPT_VERIFYCONTEXT)) { if ((unsigned long)GetLastError() != (unsigned long)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; #else for (i = 0; filenames[i]; ++i) { fd = open(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 void arc4_stir(void) { int i; if (!rs_initialized) { arc4_init(); rs_initialized = 1; } arc4_seed(); /* * 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; } 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