arc4random() number generator, for use with things like RPC xid's.

1 files changed, 175 insertions, 0 deletions

diff --git a/lib/libc/crypt/arc4random.c b/lib/libc/crypt/arc4random.c
new file mode 100644
index 00000000000..078f4eeea6d
--- /dev/null
+++ b/lib/libc/crypt/arc4random.c
@@ -0,0 +1,175 @@
+/* $Id: arc4random.c,v 1.1 1996/12/28 06:33:01 dm 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 (for instance 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 <stdlib.h>
+#include <fcntl.h>
+#include <sys/types.h>
+#include <sys/time.h>
+
+#ifdef __GNUC__
+#define inline __inline
+#else				/* !__GNUC__ */
+#define inline
+#endif				/* !__GNUC__ */
+
+struct arc4_stream {
+	u_int8_t i;
+	u_int8_t j;
+	u_int8_t s[256];
+};
+
+int     rs_initialized;
+static struct arc4_stream rs;
+
+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;
+	}
+}
+
+static void
+arc4_stir(as)
+	struct arc4_stream *as;
+{
+	int     fd;
+	struct {
+		struct timeval tv;
+		u_int8_t rnd[128 - sizeof(struct timeval)];
+	}       rdat;
+
+	gettimeofday(&rdat.tv, NULL);
+	fd = open("/dev/arandom", O_RDONLY);
+	if (fd >= 0) {
+		read(fd, rdat.rnd, sizeof(rdat.rnd));
+		close(fd);
+	}
+	/* fd < 0?  Ah, what the heck. We'll just take whatever was on the
+	 * stack... */
+
+	arc4_addrandom(as, (void *) &rdat, sizeof(rdat));
+}
+
+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 for i386 --------*/
+#include <stdio.h>
+#include <machine/pctr.h>
+int
+main(int argc, char **argv)
+{
+	const int iter = 1000000;
+	int     i;
+	pctrval v;
+
+	v = rdtsc();
+	for (i = 0; i < iter; i++)
+		arc4random();
+	v = rdtsc() - v;
+	v /= iter;
+
+	printf("%qd cycles\n", v);
+}
+#endif