diff options
Diffstat (limited to 'libc/stdlib/arc4random.c')
| -rw-r--r-- | libc/stdlib/arc4random.c | 146 |
1 files changed, 85 insertions, 61 deletions
diff --git a/libc/stdlib/arc4random.c b/libc/stdlib/arc4random.c index b83fe32a6..0013612e9 100644 --- a/libc/stdlib/arc4random.c +++ b/libc/stdlib/arc4random.c @@ -1,24 +1,29 @@ -/* $$$: 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 <dm@lcs.mit.edu>. + * Copyright (c) 1996, David Mazieres <dm@uun.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. * - * 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. + * 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 + * Here the stream cipher has been modified always to include entropy * 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. @@ -26,17 +31,15 @@ * RC4 is a registered trademark of RSA Laboratories. */ +/* $OpenBSD: arc4random.c,v 1.16 2007/02/12 19:58:47 otto Exp $ */ + #include <features.h> + #include <fcntl.h> #include <stdlib.h> #include <unistd.h> #include <sys/types.h> -#include <sys/param.h> #include <sys/time.h> -#ifdef __ARC4RANDOM_USE_ERANDOM__ -#include <sys/sysctl.h> -#endif - struct arc4_stream { u_int8_t i; @@ -46,6 +49,8 @@ struct arc4_stream { static smallint rs_initialized; static struct arc4_stream rs; +static pid_t arc4_stir_pid; +static int arc4_count; static __inline__ void arc4_init(struct arc4_stream *as) @@ -92,52 +97,83 @@ arc4_addrandom(struct arc4_stream *as, u_char *dat, int datlen) static void arc4_stir(struct arc4_stream *as) { - int fd; - struct { - struct timeval tv; - uint rnd[(128 - sizeof(struct timeval)) / sizeof(uint)]; - } rdat; int n; + u_char rnd[128]; + struct timeval tv; + +#ifndef __ARC4RANDOM_USES_NODEV__ + int fd; - gettimeofday(&rdat.tv, NULL); fd = open("/dev/urandom", O_RDONLY); if (fd != -1) { - read(fd, rdat.rnd, sizeof(rdat.rnd)); + read(fd, rnd, sizeof(rnd)); close(fd); } -#ifdef __ARC4RANDOM_USE_ERANDOM__ + /* Did the pseudo-random device fail? Use gettimeofday(). */ + else +#endif + if (gettimeofday(&tv, NULL) != (-1)) { + + /* Initialize the first element so it's hopefully not '0', + * to help out the next loop. Tossing in some prime numbers + * probably can't hurt. */ + rnd[0] = (tv.tv_sec % 10000) * 3 + tv.tv_usec * 7 + \ + (getpid() % 1000) * 13; + + for (n = 1; n < 127 ; n++) { + + /* Take advantage of the stack space. Only initialize + * elements equal to '0'. This will make the rnd[] + * array much less vulnerable to timing attacks. Here + * we'll stir getpid() into the value of the previous + * element. Approximately 1 in 128 elements will still + * become '0'. */ + + if (rnd[n] == 0) { + rnd[n] = ((rnd[n - 1] + n) ^ \ + ((getpid() % 1000) * 17)); + } + } + } else { - int mib[3]; - uint i; - size_t len; - - /* Device could not be opened, we might be chrooted, take - * randomness from sysctl. */ - - mib[0] = CTL_KERN; - mib[1] = KERN_RANDOM; - mib[2] = RANDOM_ERANDOM; - - for (i = 0; i < sizeof(rdat.rnd) / sizeof(uint); i++) { - len = sizeof(uint); - if (sysctl(mib, 3, &rdat.rnd[i], &len, NULL, 0) == -1) - break; + /* gettimeofday() failed? Do the same thing as above, but only + * with getpid(). */ + + rnd[0] = (getpid() % 1000) * 19; + for (n = 1; n < 127 ; n++) { + if (rnd[n] == 0) { + rnd[n] = ((rnd[n - 1] + n) ^ \ + ((getpid() % 1000) * 23)); + } } } -#endif - arc4_addrandom(as, (void *) &rdat, sizeof(rdat)); + arc4_stir_pid = getpid(); + arc4_addrandom(as, rnd, sizeof(rnd)); /* - * 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. N = 1024 is based on - * suggestions in the paper "(Not So) Random Shuffles of RC4" - * by Ilya Mironov. + * Discard early keystream, as per recommendations in: + * http://www.wisdom.weizmann.ac.il/~itsik/RC4/Papers/Rc4_ksa.ps */ - for (n = 0; n < 1024; n++) - arc4_getbyte(as); + for (n = 0; n < 256; n++) + (void)arc4_getbyte(as); + arc4_count = 1600000; +} + +#if 0 +static void __arc4random_stir(void); +/* + * __arc4_getbyte() is a libc private function intended for use + * with malloc. + */ +u_int8_t +__arc4_getbyte(void) +{ + if (--arc4_count == 0 || !rs_initialized) + __arc4random_stir(); + return arc4_getbyte(&rs); } +#endif static __inline__ u_int32_t arc4_getword(struct arc4_stream *as) @@ -172,20 +208,8 @@ arc4random_addrandom(u_char *dat, int datlen) u_int32_t arc4random(void) { - if (!rs_initialized) + arc4_count -= 4; + if (arc4_count <= 0 || !rs_initialized || arc4_stir_pid != getpid()) __arc4random_stir(); return arc4_getword(&rs); } - -#if 0 -/*-------- Test code --------*/ -#include <stdlib.h> -#include <stdio.h> - -int main(void) { - int random_number; - random_number = arc4random() % 65536; - printf("%d\n", random_number); - return 0; -} -#endif |