183a03b38SAndrey A. Chernov /* 283a03b38SAndrey A. Chernov * Arc4 random number generator for OpenBSD. 383a03b38SAndrey A. Chernov * Copyright 1996 David Mazieres <dm@lcs.mit.edu>. 483a03b38SAndrey A. Chernov * 583a03b38SAndrey A. Chernov * Modification and redistribution in source and binary forms is 683a03b38SAndrey A. Chernov * permitted provided that due credit is given to the author and the 783a03b38SAndrey A. Chernov * OpenBSD project (for instance by leaving this copyright notice 883a03b38SAndrey A. Chernov * intact). 983a03b38SAndrey A. Chernov */ 1083a03b38SAndrey A. Chernov 1183a03b38SAndrey A. Chernov /* 1283a03b38SAndrey A. Chernov * This code is derived from section 17.1 of Applied Cryptography, 1383a03b38SAndrey A. Chernov * second edition, which describes a stream cipher allegedly 1483a03b38SAndrey A. Chernov * compatible with RSA Labs "RC4" cipher (the actual description of 1583a03b38SAndrey A. Chernov * which is a trade secret). The same algorithm is used as a stream 1683a03b38SAndrey A. Chernov * cipher called "arcfour" in Tatu Ylonen's ssh package. 1783a03b38SAndrey A. Chernov * 1883a03b38SAndrey A. Chernov * Here the stream cipher has been modified always to include the time 1983a03b38SAndrey A. Chernov * when initializing the state. That makes it impossible to 2083a03b38SAndrey A. Chernov * regenerate the same random sequence twice, so this can't be used 2183a03b38SAndrey A. Chernov * for encryption, but will generate good random numbers. 2283a03b38SAndrey A. Chernov * 2383a03b38SAndrey A. Chernov * RC4 is a registered trademark of RSA Laboratories. 2483a03b38SAndrey A. Chernov */ 2583a03b38SAndrey A. Chernov 26333fc21eSDavid E. O'Brien #include <sys/cdefs.h> 27333fc21eSDavid E. O'Brien __FBSDID("$FreeBSD$"); 28333fc21eSDavid E. O'Brien 29d201fe46SDaniel Eischen #include "namespace.h" 30333fc21eSDavid E. O'Brien #include <sys/types.h> 31333fc21eSDavid E. O'Brien #include <sys/time.h> 3283a03b38SAndrey A. Chernov #include <stdlib.h> 3383a03b38SAndrey A. Chernov #include <fcntl.h> 3483a03b38SAndrey A. Chernov #include <unistd.h> 355295209eSBrian Feldman #include <pthread.h> 365295209eSBrian Feldman 375295209eSBrian Feldman #include "libc_private.h" 38d201fe46SDaniel Eischen #include "un-namespace.h" 3983a03b38SAndrey A. Chernov 4083a03b38SAndrey A. Chernov struct arc4_stream { 4183a03b38SAndrey A. Chernov u_int8_t i; 4283a03b38SAndrey A. Chernov u_int8_t j; 4383a03b38SAndrey A. Chernov u_int8_t s[256]; 4483a03b38SAndrey A. Chernov }; 4583a03b38SAndrey A. Chernov 465295209eSBrian Feldman static pthread_mutex_t arc4random_mtx = PTHREAD_MUTEX_INITIALIZER; 475295209eSBrian Feldman 485295209eSBrian Feldman #define RANDOMDEV "/dev/urandom" 495295209eSBrian Feldman #define THREAD_LOCK() \ 505295209eSBrian Feldman do { \ 515295209eSBrian Feldman if (__isthreaded) \ 525295209eSBrian Feldman _pthread_mutex_lock(&arc4random_mtx); \ 535295209eSBrian Feldman } while (0) 545295209eSBrian Feldman 555295209eSBrian Feldman #define THREAD_UNLOCK() \ 565295209eSBrian Feldman do { \ 575295209eSBrian Feldman if (__isthreaded) \ 585295209eSBrian Feldman _pthread_mutex_unlock(&arc4random_mtx); \ 595295209eSBrian Feldman } while (0) 605295209eSBrian Feldman 6183a03b38SAndrey A. Chernov static struct arc4_stream rs; 625295209eSBrian Feldman static int rs_initialized; 635295209eSBrian Feldman static int rs_stired; 6483a03b38SAndrey A. Chernov 6560ce8b0eSDavid Schultz static inline u_int8_t arc4_getbyte(struct arc4_stream *); 665295209eSBrian Feldman static void arc4_stir(struct arc4_stream *); 6760ce8b0eSDavid Schultz 6883a03b38SAndrey A. Chernov static inline void 6983a03b38SAndrey A. Chernov arc4_init(as) 7083a03b38SAndrey A. Chernov struct arc4_stream *as; 7183a03b38SAndrey A. Chernov { 7283a03b38SAndrey A. Chernov int n; 7383a03b38SAndrey A. Chernov 7483a03b38SAndrey A. Chernov for (n = 0; n < 256; n++) 7583a03b38SAndrey A. Chernov as->s[n] = n; 7683a03b38SAndrey A. Chernov as->i = 0; 7783a03b38SAndrey A. Chernov as->j = 0; 7883a03b38SAndrey A. Chernov } 7983a03b38SAndrey A. Chernov 8083a03b38SAndrey A. Chernov static inline void 8183a03b38SAndrey A. Chernov arc4_addrandom(as, dat, datlen) 8283a03b38SAndrey A. Chernov struct arc4_stream *as; 8383a03b38SAndrey A. Chernov u_char *dat; 8483a03b38SAndrey A. Chernov int datlen; 8583a03b38SAndrey A. Chernov { 8683a03b38SAndrey A. Chernov int n; 8783a03b38SAndrey A. Chernov u_int8_t si; 8883a03b38SAndrey A. Chernov 8983a03b38SAndrey A. Chernov as->i--; 9083a03b38SAndrey A. Chernov for (n = 0; n < 256; n++) { 9183a03b38SAndrey A. Chernov as->i = (as->i + 1); 9283a03b38SAndrey A. Chernov si = as->s[as->i]; 9383a03b38SAndrey A. Chernov as->j = (as->j + si + dat[n % datlen]); 9483a03b38SAndrey A. Chernov as->s[as->i] = as->s[as->j]; 9583a03b38SAndrey A. Chernov as->s[as->j] = si; 9683a03b38SAndrey A. Chernov } 9783a03b38SAndrey A. Chernov } 9883a03b38SAndrey A. Chernov 9983a03b38SAndrey A. Chernov static void 10083a03b38SAndrey A. Chernov arc4_stir(as) 10183a03b38SAndrey A. Chernov struct arc4_stream *as; 10283a03b38SAndrey A. Chernov { 10360ce8b0eSDavid Schultz int fd, n; 10483a03b38SAndrey A. Chernov struct { 10583a03b38SAndrey A. Chernov struct timeval tv; 10683a03b38SAndrey A. Chernov pid_t pid; 10783a03b38SAndrey A. Chernov u_int8_t rnd[128 - sizeof(struct timeval) - sizeof(pid_t)]; 10883a03b38SAndrey A. Chernov } rdat; 10983a03b38SAndrey A. Chernov 11083a03b38SAndrey A. Chernov gettimeofday(&rdat.tv, NULL); 11183a03b38SAndrey A. Chernov rdat.pid = getpid(); 1125295209eSBrian Feldman fd = _open(RANDOMDEV, O_RDONLY, 0); 11383a03b38SAndrey A. Chernov if (fd >= 0) { 1149233c4d9SJason Evans (void) _read(fd, rdat.rnd, sizeof(rdat.rnd)); 1159233c4d9SJason Evans _close(fd); 11683a03b38SAndrey A. Chernov } 11783a03b38SAndrey A. Chernov /* fd < 0? Ah, what the heck. We'll just take whatever was on the 11883a03b38SAndrey A. Chernov * stack... */ 11983a03b38SAndrey A. Chernov 12083a03b38SAndrey A. Chernov arc4_addrandom(as, (void *) &rdat, sizeof(rdat)); 12160ce8b0eSDavid Schultz 12260ce8b0eSDavid Schultz /* 12360ce8b0eSDavid Schultz * Throw away the first N bytes of output, as suggested in the 12460ce8b0eSDavid Schultz * paper "Weaknesses in the Key Scheduling Algorithm of RC4" 12560ce8b0eSDavid Schultz * by Fluher, Mantin, and Shamir. N=1024 is based on 12660ce8b0eSDavid Schultz * suggestions in the paper "(Not So) Random Shuffles of RC4" 12760ce8b0eSDavid Schultz * by Ilya Mironov. 12860ce8b0eSDavid Schultz */ 12960ce8b0eSDavid Schultz for (n = 0; n < 1024; n++) 13060ce8b0eSDavid Schultz arc4_getbyte(as); 13183a03b38SAndrey A. Chernov } 13283a03b38SAndrey A. Chernov 13383a03b38SAndrey A. Chernov static inline u_int8_t 13483a03b38SAndrey A. Chernov arc4_getbyte(as) 13583a03b38SAndrey A. Chernov struct arc4_stream *as; 13683a03b38SAndrey A. Chernov { 13783a03b38SAndrey A. Chernov u_int8_t si, sj; 13883a03b38SAndrey A. Chernov 13983a03b38SAndrey A. Chernov as->i = (as->i + 1); 14083a03b38SAndrey A. Chernov si = as->s[as->i]; 14183a03b38SAndrey A. Chernov as->j = (as->j + si); 14283a03b38SAndrey A. Chernov sj = as->s[as->j]; 14383a03b38SAndrey A. Chernov as->s[as->i] = sj; 14483a03b38SAndrey A. Chernov as->s[as->j] = si; 1457ce21b20SBrian Feldman 14683a03b38SAndrey A. Chernov return (as->s[(si + sj) & 0xff]); 14783a03b38SAndrey A. Chernov } 14883a03b38SAndrey A. Chernov 14983a03b38SAndrey A. Chernov static inline u_int32_t 15083a03b38SAndrey A. Chernov arc4_getword(as) 15183a03b38SAndrey A. Chernov struct arc4_stream *as; 15283a03b38SAndrey A. Chernov { 15383a03b38SAndrey A. Chernov u_int32_t val; 1547ce21b20SBrian Feldman 15583a03b38SAndrey A. Chernov val = arc4_getbyte(as) << 24; 15683a03b38SAndrey A. Chernov val |= arc4_getbyte(as) << 16; 15783a03b38SAndrey A. Chernov val |= arc4_getbyte(as) << 8; 15883a03b38SAndrey A. Chernov val |= arc4_getbyte(as); 1597ce21b20SBrian Feldman 1607ce21b20SBrian Feldman return (val); 16183a03b38SAndrey A. Chernov } 16283a03b38SAndrey A. Chernov 1635295209eSBrian Feldman static void 1645295209eSBrian Feldman arc4_check_init(void) 16583a03b38SAndrey A. Chernov { 16683a03b38SAndrey A. Chernov if (!rs_initialized) { 16783a03b38SAndrey A. Chernov arc4_init(&rs); 16883a03b38SAndrey A. Chernov rs_initialized = 1; 16983a03b38SAndrey A. Chernov } 1705295209eSBrian Feldman } 1715295209eSBrian Feldman 1725295209eSBrian Feldman static void 1735295209eSBrian Feldman arc4_check_stir(void) 1745295209eSBrian Feldman { 1755295209eSBrian Feldman if (!rs_stired) { 17683a03b38SAndrey A. Chernov arc4_stir(&rs); 1775295209eSBrian Feldman rs_stired = 1; 1785295209eSBrian Feldman } 1795295209eSBrian Feldman } 1805295209eSBrian Feldman 1815295209eSBrian Feldman void 1825295209eSBrian Feldman arc4random_stir() 1835295209eSBrian Feldman { 1845295209eSBrian Feldman THREAD_LOCK(); 1855295209eSBrian Feldman arc4_check_init(); 1865295209eSBrian Feldman arc4_stir(&rs); 1875295209eSBrian Feldman THREAD_UNLOCK(); 18883a03b38SAndrey A. Chernov } 18983a03b38SAndrey A. Chernov 19083a03b38SAndrey A. Chernov void 19183a03b38SAndrey A. Chernov arc4random_addrandom(dat, datlen) 19283a03b38SAndrey A. Chernov u_char *dat; 19383a03b38SAndrey A. Chernov int datlen; 19483a03b38SAndrey A. Chernov { 1955295209eSBrian Feldman THREAD_LOCK(); 1965295209eSBrian Feldman arc4_check_init(); 1975295209eSBrian Feldman arc4_check_stir(); 19883a03b38SAndrey A. Chernov arc4_addrandom(&rs, dat, datlen); 1995295209eSBrian Feldman THREAD_UNLOCK(); 20083a03b38SAndrey A. Chernov } 20183a03b38SAndrey A. Chernov 20283a03b38SAndrey A. Chernov u_int32_t 20383a03b38SAndrey A. Chernov arc4random() 20483a03b38SAndrey A. Chernov { 2055295209eSBrian Feldman u_int32_t rnd; 2067ce21b20SBrian Feldman 2075295209eSBrian Feldman THREAD_LOCK(); 2085295209eSBrian Feldman arc4_check_init(); 2095295209eSBrian Feldman arc4_check_stir(); 2105295209eSBrian Feldman rnd = arc4_getword(&rs); 2115295209eSBrian Feldman THREAD_UNLOCK(); 2125295209eSBrian Feldman 2135295209eSBrian Feldman return (rnd); 21483a03b38SAndrey A. Chernov } 21583a03b38SAndrey A. Chernov 21683a03b38SAndrey A. Chernov #if 0 21783a03b38SAndrey A. Chernov /*-------- Test code for i386 --------*/ 21883a03b38SAndrey A. Chernov #include <stdio.h> 21983a03b38SAndrey A. Chernov #include <machine/pctr.h> 22083a03b38SAndrey A. Chernov int 22183a03b38SAndrey A. Chernov main(int argc, char **argv) 22283a03b38SAndrey A. Chernov { 22383a03b38SAndrey A. Chernov const int iter = 1000000; 22483a03b38SAndrey A. Chernov int i; 22583a03b38SAndrey A. Chernov pctrval v; 22683a03b38SAndrey A. Chernov 22783a03b38SAndrey A. Chernov v = rdtsc(); 22883a03b38SAndrey A. Chernov for (i = 0; i < iter; i++) 22983a03b38SAndrey A. Chernov arc4random(); 23083a03b38SAndrey A. Chernov v = rdtsc() - v; 23183a03b38SAndrey A. Chernov v /= iter; 23283a03b38SAndrey A. Chernov 23383a03b38SAndrey A. Chernov printf("%qd cycles\n", v); 23483a03b38SAndrey A. Chernov } 23583a03b38SAndrey A. Chernov #endif 236