* Updating common/lib * Updating lib/csu * Updating lib/libc * Updating libexec/ld.elf_so * Corrected test on __minix in featuretest to actually follow the meaning of the comment. * Cleaned up _REENTRANT-related defintions. * Disabled -D_REENTRANT for libfetch * Removing some unneeded __NBSD_LIBC defines and tests Change-Id: Ic1394baef74d11b9f86b312f5ff4bbc3cbf72ce2
307 lines
7 KiB
C
307 lines
7 KiB
C
/* $NetBSD: arc4random.c,v 1.20 2012/08/20 21:38:09 dsl Exp $ */
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/* $OpenBSD: arc4random.c,v 1.6 2001/06/05 05:05:38 pvalchev Exp $ */
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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 by leaving this copyright notice 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 <sys/cdefs.h>
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#if defined(LIBC_SCCS) && !defined(lint)
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__RCSID("$NetBSD: arc4random.c,v 1.20 2012/08/20 21:38:09 dsl Exp $");
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#endif /* LIBC_SCCS and not lint */
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#include "namespace.h"
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#include "reentrant.h"
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#include <fcntl.h>
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#include <stdlib.h>
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#include <unistd.h>
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#include <sys/types.h>
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#include <sys/param.h>
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#include <sys/time.h>
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#include <sys/sysctl.h>
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#ifdef __weak_alias
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__weak_alias(arc4random,_arc4random)
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__weak_alias(arc4random_addrandom,_arc4random_addrandom)
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__weak_alias(arc4random_buf,_arc4random_buf)
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__weak_alias(arc4random_stir,_arc4random_stir)
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__weak_alias(arc4random_uniform,_arc4random_uniform)
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#endif
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struct arc4_stream {
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uint8_t stirred;
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uint8_t pad;
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uint8_t i;
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uint8_t j;
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uint8_t s[(uint8_t)~0u + 1u]; /* 256 to you and me */
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#ifdef _REENTRANT
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mutex_t mtx;
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#endif
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};
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#ifdef _REENTRANT
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#define LOCK(rs) { \
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int isthreaded = __isthreaded; \
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if (isthreaded) \
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mutex_lock(&(rs)->mtx);
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#define UNLOCK(rs) \
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if (isthreaded) \
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mutex_unlock(&(rs)->mtx); \
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}
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#else
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#define LOCK(rs)
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#define UNLOCK(rs)
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#endif
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#define S(n) (n)
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#define S4(n) S(n), S(n + 1), S(n + 2), S(n + 3)
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#define S16(n) S4(n), S4(n + 4), S4(n + 8), S4(n + 12)
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#define S64(n) S16(n), S16(n + 16), S16(n + 32), S16(n + 48)
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#define S256 S64(0), S64(64), S64(128), S64(192)
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static struct arc4_stream rs = { .i = 0xff, .j = 0, .s = { S256 },
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#ifdef _REENTRANT
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.stirred = 0, .mtx = MUTEX_INITIALIZER };
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#else
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.stirred = 0 };
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#endif
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#undef S
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#undef S4
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#undef S16
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#undef S64
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#undef S256
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static inline void arc4_addrandom(struct arc4_stream *, u_char *, int);
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static __noinline void arc4_stir(struct arc4_stream *);
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static inline uint8_t arc4_getbyte(struct arc4_stream *);
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static inline uint32_t arc4_getword(struct arc4_stream *);
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static inline int
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arc4_check_init(struct arc4_stream *as)
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{
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if (__predict_true(rs.stirred))
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return 0;
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arc4_stir(as);
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return 1;
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}
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static inline void
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arc4_addrandom(struct arc4_stream *as, u_char *dat, int datlen)
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{
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uint8_t si;
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size_t n;
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for (n = 0; n < __arraycount(as->s); 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 __noinline void
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arc4_stir(struct arc4_stream *as)
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{
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#ifdef __minix
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/* LSC: We do not have a compatibility layer for the
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* KERN_URND call, so use the old way... */
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int fd;
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size_t j;
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struct {
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struct timeval tv;
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u_int rnd[(128 - sizeof(struct timeval)) / sizeof(u_int)];
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} rdat;
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gettimeofday(&rdat.tv, NULL);
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fd = open("/dev/urandom", O_RDONLY);
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if (fd != -1) {
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read(fd, rdat.rnd, sizeof(rdat.rnd));
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close(fd);
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}
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/* fd < 0 or failed sysctl ? Ah, what the heck. We'll just take
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* whatever was on the stack... */
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#else
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int rdat[32];
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int mib[] = { CTL_KERN, KERN_URND };
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size_t len;
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size_t i, j;
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/*
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* This code once opened and read /dev/urandom on each
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* call. That causes repeated rekeying of the kernel stream
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* generator, which is very wasteful. Because of application
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* behavior, caching the fd doesn't really help. So we just
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* fill up the tank from sysctl, which is a tiny bit slower
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* for us but much friendlier to other entropy consumers.
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*/
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for (i = 0; i < __arraycount(rdat); i++) {
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len = sizeof(rdat[i]);
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if (sysctl(mib, 2, &rdat[i], &len, NULL, 0) == -1)
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abort();
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}
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#endif
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arc4_addrandom(as, (void *) &rdat, (int)sizeof(rdat));
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/*
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* Throw away the first N words of output, as suggested in the
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* paper "Weaknesses in the Key Scheduling Algorithm of RC4"
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* by Fluher, Mantin, and Shamir. (N = 256 in our case.)
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*/
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for (j = 0; j < __arraycount(as->s) * 4; j++)
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arc4_getbyte(as);
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as->stirred = 1;
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}
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static __always_inline uint8_t
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arc4_getbyte_ij(struct arc4_stream *as, uint8_t *i, uint8_t *j)
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{
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uint8_t si, sj;
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*i = *i + 1;
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si = as->s[*i];
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*j = *j + si;
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sj = as->s[*j];
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as->s[*i] = sj;
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as->s[*j] = si;
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return (as->s[(si + sj) & 0xff]);
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}
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static inline uint8_t
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arc4_getbyte(struct arc4_stream *as)
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{
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return arc4_getbyte_ij(as, &as->i, &as->j);
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}
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static inline uint32_t
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arc4_getword(struct arc4_stream *as)
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{
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uint32_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(void)
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{
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LOCK(&rs);
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arc4_stir(&rs);
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UNLOCK(&rs);
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}
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void
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arc4random_addrandom(u_char *dat, int datlen)
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{
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LOCK(&rs);
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arc4_check_init(&rs);
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arc4_addrandom(&rs, dat, datlen);
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UNLOCK(&rs);
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}
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uint32_t
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arc4random(void)
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{
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uint32_t v;
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LOCK(&rs);
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arc4_check_init(&rs);
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v = arc4_getword(&rs);
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UNLOCK(&rs);
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return v;
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}
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void
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arc4random_buf(void *buf, size_t len)
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{
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uint8_t *bp = buf;
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uint8_t *ep = bp + len;
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uint8_t i, j;
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LOCK(&rs);
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arc4_check_init(&rs);
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/* cache i and j - compiler can't know 'buf' doesn't alias them */
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i = rs.i;
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j = rs.j;
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while (bp < ep)
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*bp++ = arc4_getbyte_ij(&rs, &i, &j);
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rs.i = i;
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rs.j = j;
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UNLOCK(&rs);
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}
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/*-
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* Written by Damien Miller.
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* With simplifications by Jinmei Tatuya.
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*/
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/*
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* Calculate a uniformly distributed random number less than
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* upper_bound avoiding "modulo bias".
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*
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* Uniformity is achieved by generating new random numbers
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* until the one returned is outside the range
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* [0, 2^32 % upper_bound[. This guarantees the selected
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* random number will be inside the range
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* [2^32 % upper_bound, 2^32[ which maps back to
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* [0, upper_bound[ after reduction modulo upper_bound.
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*/
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uint32_t
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arc4random_uniform(uint32_t upper_bound)
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{
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uint32_t r, min;
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if (upper_bound < 2)
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return 0;
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/* calculate (2^32 % upper_bound) avoiding 64-bit math */
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/* ((2^32 - x) % x) == (2^32 % x) when x <= 2^31 */
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min = (0xFFFFFFFFU - upper_bound + 1) % upper_bound;
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LOCK(&rs);
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arc4_check_init(&rs);
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/*
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* This could theoretically loop forever but each retry has
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* p > 0.5 (worst case, usually far better) of selecting a
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* number inside the range we need, so it should rarely need
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* to re-roll (at all).
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*/
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do
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r = arc4_getword(&rs);
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while (r < min);
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UNLOCK(&rs);
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return r % upper_bound;
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}
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