/* $$$: arc4random.c 2005/02/08 robert */ /* $NetBSD: arc4random.c,v 1.5.2.1 2004/03/26 22:52:50 jmc Exp $ */ /* $OpenBSD: arc4random.c,v 1.6 2001/06/05 05:05:38 pvalchev Exp $ */ /* * Arc4 random number generator for OpenBSD. * Copyright 1996 David Mazieres . * * Modification and redistribution in source and binary forms is * permitted provided that due credit is given to the author and the * OpenBSD project by leaving this copyright notice intact. */ /* * 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. */ #include #if !defined(HAVE_OPENSSL) && !defined(HAVE_GNUTLS) && !defined(HAVE_MBEDTLS) && !defined(HAVE_ARC4RANDOM) #include "arc4random.h" #ifdef HAVE_GETRUSAGE #include #endif struct arc4_stream { uint8_t i; uint8_t j; uint8_t s[256]; }; static int rs_initialized; static struct arc4_stream rs; static inline void arc4_init(struct arc4_stream *); static inline void arc4_addrandom(struct arc4_stream *, uint8_t *, int); static void arc4_stir(struct arc4_stream *); static inline uint8_t arc4_getbyte(struct arc4_stream *); static inline uint32_t arc4_getword(struct arc4_stream *); static inline void arc4_init(struct arc4_stream *as) { int n; for(n = 0; n < 256; n++) as->s[n] = n; as->i = 0; as->j = 0; } static inline void arc4_addrandom(struct arc4_stream *as, uint8_t *dat, int datlen) { int n; uint8_t si; as->i--; for(n = 0; n < 256; n++) { as->i = (as->i + 1); si = as->s[as->i]; as->j = (as->j + si + dat[n % datlen]); as->s[as->i] = as->s[as->j]; as->s[as->j] = si; } as->j = as->i; } static void arc4_stir(struct arc4_stream *as) { struct timeval tv; pid_t pid; int n; #ifdef _WIN32 HMODULE lib; #endif /* XXX this doesn't support egd sources or similiar */ pid = getpid(); arc4_addrandom(as, (void *)&pid, sizeof(pid)); rb_gettimeofday(&tv, NULL); arc4_addrandom(as, (void *)&tv.tv_sec, sizeof(&tv.tv_sec)); arc4_addrandom(as, (void *)&tv.tv_usec, sizeof(&tv.tv_usec)); rb_gettimeofday(&tv, NULL); arc4_addrandom(as, (void *)&tv.tv_usec, sizeof(&tv.tv_usec)); #if defined(HAVE_GETRUSAGE) && RUSAGE_SELF { struct rusage buf; getrusage(RUSAGE_SELF, &buf); arc4_addrandom(as, (void *)&buf, sizeof(buf)); memset(&buf, 0, sizeof(buf))} #endif #if !defined(_WIN32) { uint8_t rnd[128]; int fd; fd = open("/dev/urandom", O_RDONLY); if(fd != -1) { read(fd, rnd, sizeof(rnd)); close(fd); arc4_addrandom(as, (void *)rnd, sizeof(rnd)); memset(&rnd, 0, sizeof(rnd)); } } #else { LARGE_INTEGER performanceCount; if(QueryPerformanceCounter(&performanceCount)) { arc4_addrandom(as, (void *)&performanceCount, sizeof(performanceCount)); } lib = LoadLibrary("ADVAPI32.DLL"); if(lib) { uint8_t rnd[128]; BOOLEAN(APIENTRY * pfn) (void *, ULONG) = (BOOLEAN(APIENTRY *) (void *, ULONG))GetProcAddress(lib, "SystemFunction036"); if(pfn) { if(pfn(rnd, sizeof(rnd)) == TRUE) arc4_addrandom(as, (void *)rnd, sizeof(rnd)); memset(&rnd, 0, sizeof(rnd)); } } } #endif /* * Throw away the first N words of output, as suggested in the * paper "Weaknesses in the Key Scheduling Algorithm of RC4" * by Fluher, Mantin, and Shamir. * http://www.wisdom.weizmann.ac.il/~itsik/RC4/Papers/Rc4_ksa.ps * N = 256 in our case. */ for(n = 0; n < 256 * 4; n++) arc4_getbyte(as); } static inline uint8_t arc4_getbyte(struct arc4_stream *as) { uint8_t si, sj; as->i = (as->i + 1); si = as->s[as->i]; as->j = (as->j + si); sj = as->s[as->j]; as->s[as->i] = sj; as->s[as->j] = si; return (as->s[(si + sj) & 0xff]); } static inline uint32_t arc4_getword(struct arc4_stream *as) { uint32_t val; val = arc4_getbyte(as) << 24; val |= arc4_getbyte(as) << 16; val |= arc4_getbyte(as) << 8; val |= arc4_getbyte(as); return val; } void arc4random_stir(void) { if(!rs_initialized) { arc4_init(&rs); rs_initialized = 1; } arc4_stir(&rs); } void arc4random_addrandom(uint8_t *dat, int datlen) { if(!rs_initialized) arc4random_stir(); arc4_addrandom(&rs, dat, datlen); } uint32_t arc4random(void) { if(!rs_initialized) arc4random_stir(); return arc4_getword(&rs); } #endif