--- /dev/null
+/* $$$: 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>.
+ *
+ * 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 <features.h>
+#ifdef __UCLIBC_HAS_ARC4RANDOM__
+
+#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;
+ u_int8_t j;
+ u_int8_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 *, u_char *, int);
+static void arc4_stir(struct arc4_stream *);
+static inline u_int8_t arc4_getbyte(struct arc4_stream *);
+static inline u_int32_t arc4_getword(struct arc4_stream *);
+
+static inline void
+arc4_init(as)
+ 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(as, dat, datlen)
+ struct arc4_stream *as;
+ u_char *dat;
+ int datlen;
+{
+ int n;
+ u_int8_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(as)
+ struct arc4_stream *as;
+{
+ int fd;
+ struct {
+ struct timeval tv;
+ u_int rnd[(128 - sizeof(struct timeval)) / sizeof(u_int)];
+ } rdat;
+ int n;
+
+ gettimeofday(&rdat.tv, NULL);
+ fd = __open("/dev/urandom", O_RDONLY);
+ if (fd != -1) {
+ __read(fd, rdat.rnd, sizeof(rdat.rnd));
+ __close(fd);
+ }
+#ifdef __ARC4RANDOM_USE_ERANDOM__
+ else {
+ int mib[3];
+ u_int 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(u_int); i++) {
+ len = sizeof(u_int);
+ if (sysctl(mib, 3, &rdat.rnd[i], &len, NULL, 0) == -1)
+ break;
+ }
+ }
+#endif
+
+ arc4_addrandom(as, (void *) &rdat, sizeof(rdat));
+
+ /*
+ * 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 u_int8_t
+arc4_getbyte(as)
+ struct arc4_stream *as;
+{
+ u_int8_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 u_int32_t
+arc4_getword(as)
+ struct arc4_stream *as;
+{
+ u_int32_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()
+{
+ if (!rs_initialized) {
+ arc4_init(&rs);
+ rs_initialized = 1;
+ }
+ arc4_stir(&rs);
+}
+
+void
+arc4random_addrandom(dat, datlen)
+ u_char *dat;
+ int datlen;
+{
+ if (!rs_initialized)
+ arc4random_stir();
+ arc4_addrandom(&rs, dat, datlen);
+}
+
+u_int32_t
+arc4random()
+{
+ if (!rs_initialized)
+ 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
+
+#endif /* __UCLIBC_HAS_ARC4RANDOM__ */
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