173 lines
3.2 KiB
C
173 lines
3.2 KiB
C
/* $FreeBSD$ */
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/*
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* Arc4 random number generator for OpenBSD.
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* Copyright 1996 David Mazieres <dm@lcs.mit.edu>.
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*
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* Modification and redistribution in source and binary forms is
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* permitted provided that due credit is given to the author and the
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* OpenBSD project (for instance by leaving this copyright notice
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* intact).
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*/
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/*
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* This code is derived from section 17.1 of Applied Cryptography,
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* second edition, which describes a stream cipher allegedly
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* compatible with RSA Labs "RC4" cipher (the actual description of
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* which is a trade secret). The same algorithm is used as a stream
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* cipher called "arcfour" in Tatu Ylonen's ssh package.
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*
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* Here the stream cipher has been modified always to include the time
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* when initializing the state. That makes it impossible to
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* regenerate the same random sequence twice, so this can't be used
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* for encryption, but will generate good random numbers.
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*
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* RC4 is a registered trademark of RSA Laboratories.
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*/
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#include <stdlib.h>
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#include <fcntl.h>
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#include <unistd.h>
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#include <sys/types.h>
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#include <sys/time.h>
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struct arc4_stream {
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u_int8_t i;
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u_int8_t j;
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u_int8_t s[256];
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};
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static int rs_initialized;
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static struct arc4_stream rs;
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static inline void
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arc4_init(as)
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struct arc4_stream *as;
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{
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int n;
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for (n = 0; n < 256; n++)
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as->s[n] = n;
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as->i = 0;
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as->j = 0;
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}
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static inline void
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arc4_addrandom(as, dat, datlen)
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struct arc4_stream *as;
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u_char *dat;
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int datlen;
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{
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int n;
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u_int8_t si;
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as->i--;
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for (n = 0; n < 256; n++) {
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as->i = (as->i + 1);
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si = as->s[as->i];
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as->j = (as->j + si + dat[n % datlen]);
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as->s[as->i] = as->s[as->j];
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as->s[as->j] = si;
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}
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}
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static void
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arc4_stir(as)
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struct arc4_stream *as;
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{
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int fd;
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struct {
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struct timeval tv;
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pid_t pid;
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u_int8_t rnd[128 - sizeof(struct timeval) - sizeof(pid_t)];
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} rdat;
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gettimeofday(&rdat.tv, NULL);
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rdat.pid = getpid();
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fd = open("/dev/urandom", O_RDONLY, 0);
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if (fd >= 0) {
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(void) read(fd, rdat.rnd, sizeof(rdat.rnd));
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close(fd);
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}
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/* fd < 0? Ah, what the heck. We'll just take whatever was on the
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* stack... */
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arc4_addrandom(as, (void *) &rdat, sizeof(rdat));
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}
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static inline u_int8_t
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arc4_getbyte(as)
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struct arc4_stream *as;
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{
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u_int8_t si, sj;
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as->i = (as->i + 1);
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si = as->s[as->i];
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as->j = (as->j + si);
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sj = as->s[as->j];
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as->s[as->i] = sj;
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as->s[as->j] = si;
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return (as->s[(si + sj) & 0xff]);
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}
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static inline u_int32_t
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arc4_getword(as)
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struct arc4_stream *as;
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{
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u_int32_t val;
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val = arc4_getbyte(as) << 24;
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val |= arc4_getbyte(as) << 16;
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val |= arc4_getbyte(as) << 8;
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val |= arc4_getbyte(as);
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return val;
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}
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void
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arc4random_stir()
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{
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if (!rs_initialized) {
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arc4_init(&rs);
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rs_initialized = 1;
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}
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arc4_stir(&rs);
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}
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void
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arc4random_addrandom(dat, datlen)
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u_char *dat;
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int datlen;
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{
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if (!rs_initialized)
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arc4random_stir();
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arc4_addrandom(&rs, dat, datlen);
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}
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u_int32_t
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arc4random()
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{
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if (!rs_initialized)
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arc4random_stir();
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return arc4_getword(&rs);
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}
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#if 0
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/*-------- Test code for i386 --------*/
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#include <stdio.h>
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#include <machine/pctr.h>
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int
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main(int argc, char **argv)
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{
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const int iter = 1000000;
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int i;
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pctrval v;
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v = rdtsc();
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for (i = 0; i < iter; i++)
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arc4random();
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v = rdtsc() - v;
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v /= iter;
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printf("%qd cycles\n", v);
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}
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#endif
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