- http://www.mirbsd.org/MirOS/dist/hosted/other/arc4random.c

Changed files:
    arc4random.c -> 1.1

diff --git a/arc4random.c b/arc4random.c
new file mode 100644 (file)
index 0000000..8e8331d
--- /dev/null
+++ b/arc4random.c
@@ -0,0 +1,198 @@
+/* $MirOS: contrib/code/Snippets/arc4random.c,v 1.2 2007/09/09 22:14:04 tg 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.
+ */
+
+/*-
+ * Modified by Robert Connolly from OpenBSD lib/libc/crypt/arc4random.c v1.11.
+ * This is arc4random(3) using urandom.
+ */
+
+#include <sys/param.h>
+#include <sys/types.h>
+#include <sys/time.h>
+#if HAVE_SYS_SYSCTL_H
+#include <sys/sysctl.h>
+#endif
+#include <fcntl.h>
+#if HAVE_STDINT_H
+#include <stdint.h>
+#endif
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+struct arc4_stream {
+       uint8_t i;
+       uint8_t j;
+       uint8_t s[256];
+};
+
+static int rs_initialized;
+static struct arc4_stream rs;
+static pid_t arc4_stir_pid;
+
+static uint8_t arc4_getbyte(struct arc4_stream *);
+
+u_int32_t arc4random(void);
+void arc4random_addrandom(u_char *, int);
+void arc4random_stir(void);
+
+static void
+arc4_init(struct arc4_stream *as)
+{
+       int     n;
+
+       for (n = 0; n < 256; n++)
+               as->s[n] = n;
+       as->i = 0;
+       as->j = 0;
+}
+
+static void
+arc4_addrandom(struct arc4_stream *as, u_char *dat, int datlen)
+{
+       int     n;
+       uint8_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(struct arc4_stream *as)
+{
+       int     n, fd;
+       struct {
+               struct timeval tv;
+               u_int rnd[(128 - sizeof(struct timeval)) / sizeof(u_int)];
+       }       rdat;
+
+       gettimeofday(&rdat.tv, NULL);
+
+       /* /dev/urandom is a multithread interface, sysctl is not. */
+       /* Try to use /dev/urandom before sysctl. */
+       fd = open("/dev/urandom", O_RDONLY);
+       if (fd != -1) {
+               read(fd, rdat.rnd, sizeof(rdat.rnd));
+               close(fd);
+       } else {
+               /* /dev/urandom failed? Maybe we're in a chroot. */
+//#if defined(CTL_KERN) && defined(KERN_RANDOM) && defined(RANDOM_UUID)
+#ifdef _LINUX_SYSCTL_H
+               /* XXX this is for Linux, which uses enums */
+
+               int mib[3];
+               size_t i, len;
+
+               mib[0] = CTL_KERN;
+               mib[1] = KERN_RANDOM;
+               mib[2] = RANDOM_UUID;
+
+               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) {
+                               fprintf(stderr, "warning: no entropy source\n");
+                               break;
+                       }
+               }
+#else
+               /* XXX kFreeBSD doesn't seem to have KERN_ARND or so */
+               ;
+#endif
+       }
+
+       arc4_stir_pid = getpid();
+       /*
+        * Time to give up. If no entropy could be found then we will just
+        * use gettimeofday.
+        */
+       arc4_addrandom(as, (void *)&rdat, sizeof(rdat));
+
+       /*
+        * Discard early keystream, as per recommendations in:
+        * http://www.wisdom.weizmann.ac.il/~itsik/RC4/Papers/Rc4_ksa.ps
+        * We discard 256 words. A long word is 4 bytes.
+        */
+       for (n = 0; n < 256 * 4; n ++)
+               arc4_getbyte(as);
+}
+
+static uint8_t
+arc4_getbyte(struct arc4_stream *as)
+{
+       uint8_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 uint32_t
+arc4_getword(struct arc4_stream *as)
+{
+       uint32_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(void)
+{
+       if (!rs_initialized) {
+               arc4_init(&rs);
+               rs_initialized = 1;
+       }
+       arc4_stir(&rs);
+}
+
+void
+arc4random_addrandom(u_char *dat, int datlen)
+{
+       if (!rs_initialized)
+               arc4random_stir();
+       arc4_addrandom(&rs, dat, datlen);
+}
+
+u_int32_t
+arc4random(void)
+{
+       if (!rs_initialized || arc4_stir_pid != getpid())
+               arc4random_stir();
+       return arc4_getword(&rs);
+}