1 files changed, 304 insertions, 0 deletions
diff --git a/lib/libc/gen/arc4random.c b/lib/libc/gen/arc4random.c
new file mode 100644
index 0000000..56dfba9
--- /dev/null
+++ b/lib/libc/gen/arc4random.c
@@ -0,0 +1,304 @@
+/*
+ * Copyright (c) 1996, David Mazieres <dm@uun.org>
+ * Copyright (c) 2008, Damien Miller <djm@openbsd.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.
+ *
+ * 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
+ * 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 <sys/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+#include "namespace.h"
+#include <sys/types.h>
+#include <sys/time.h>
+#include <stdlib.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <pthread.h>
+
+#include "libc_private.h"
+#include "un-namespace.h"
+
+struct arc4_stream {
+	u_int8_t i;
+	u_int8_t j;
+	u_int8_t s[256];
+};
+
+static pthread_mutex_t	arc4random_mtx = PTHREAD_MUTEX_INITIALIZER;
+
+#define	RANDOMDEV	"/dev/random"
+#define KEYSIZE		128
+#define	THREAD_LOCK()						\
+	do {							\
+		if (__isthreaded)				\
+			_pthread_mutex_lock(&arc4random_mtx);	\
+	} while (0)
+
+#define	THREAD_UNLOCK()						\
+	do {							\
+		if (__isthreaded)				\
+			_pthread_mutex_unlock(&arc4random_mtx);	\
+	} while (0)
+
+static struct arc4_stream rs;
+static int rs_initialized;
+static int rs_stired;
+static int arc4_count;
+
+static inline u_int8_t arc4_getbyte(void);
+static void arc4_stir(void);
+
+static inline void
+arc4_init(void)
+{
+	int     n;
+
+	for (n = 0; n < 256; n++)
+		rs.s[n] = n;
+	rs.i = 0;
+	rs.j = 0;
+}
+
+static inline void
+arc4_addrandom(u_char *dat, int datlen)
+{
+	int     n;
+	u_int8_t si;
+
+	rs.i--;
+	for (n = 0; n < 256; n++) {
+		rs.i = (rs.i + 1);
+		si = rs.s[rs.i];
+		rs.j = (rs.j + si + dat[n % datlen]);
+		rs.s[rs.i] = rs.s[rs.j];
+		rs.s[rs.j] = si;
+	}
+	rs.j = rs.i;
+}
+
+static void
+arc4_stir(void)
+{
+	int done, fd, n;
+	struct {
+		struct timeval	tv;
+		pid_t 		pid;
+		u_int8_t 	rnd[KEYSIZE];
+	} rdat;
+
+	fd = _open(RANDOMDEV, O_RDONLY, 0);
+	done = 0;
+	if (fd >= 0) {
+		if (_read(fd, &rdat, KEYSIZE) == KEYSIZE)
+			done = 1;
+		(void)_close(fd);
+	} 
+	if (!done) {
+		(void)gettimeofday(&rdat.tv, NULL);
+		rdat.pid = getpid();
+		/* We'll just take whatever was on the stack too... */
+	}
+
+	arc4_addrandom((u_char *)&rdat, KEYSIZE);
+
+	/*
+	 * Throw away the first N bytes 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.
+	 */
+	for (n = 0; n < 1024; n++)
+		(void) arc4_getbyte();
+	arc4_count = 1600000;
+}
+
+static inline u_int8_t
+arc4_getbyte(void)
+{
+	u_int8_t si, sj;
+
+	rs.i = (rs.i + 1);
+	si = rs.s[rs.i];
+	rs.j = (rs.j + si);
+	sj = rs.s[rs.j];
+	rs.s[rs.i] = sj;
+	rs.s[rs.j] = si;
+
+	return (rs.s[(si + sj) & 0xff]);
+}
+
+static inline u_int32_t
+arc4_getword(void)
+{
+	u_int32_t val;
+
+	val = arc4_getbyte() << 24;
+	val |= arc4_getbyte() << 16;
+	val |= arc4_getbyte() << 8;
+	val |= arc4_getbyte();
+
+	return (val);
+}
+
+static void
+arc4_check_init(void)
+{
+	if (!rs_initialized) {
+		arc4_init();
+		rs_initialized = 1;
+	}
+}
+
+static inline void
+arc4_check_stir(void)
+{
+	if (!rs_stired || arc4_count <= 0) {
+		arc4_stir();
+		rs_stired = 1;
+	}
+}
+
+void
+arc4random_stir(void)
+{
+	THREAD_LOCK();
+	arc4_check_init();
+	arc4_stir();
+	rs_stired = 1;
+	THREAD_UNLOCK();
+}
+
+void
+arc4random_addrandom(u_char *dat, int datlen)
+{
+	THREAD_LOCK();
+	arc4_check_init();
+	arc4_check_stir();
+	arc4_addrandom(dat, datlen);
+	THREAD_UNLOCK();
+}
+
+u_int32_t
+arc4random(void)
+{
+	u_int32_t rnd;
+
+	THREAD_LOCK();
+	arc4_check_init();
+	arc4_check_stir();
+	rnd = arc4_getword();
+	arc4_count -= 4;
+	THREAD_UNLOCK();
+
+	return (rnd);
+}
+
+void
+arc4random_buf(void *_buf, size_t n)
+{
+	u_char *buf = (u_char *)_buf;
+
+	THREAD_LOCK();
+	arc4_check_init();
+	while (n--) {
+		arc4_check_stir();
+		buf[n] = arc4_getbyte();
+		arc4_count--;
+	}
+	THREAD_UNLOCK();
+}
+
+/*
+ * Calculate a uniformly distributed random number less than upper_bound
+ * avoiding "modulo bias".
+ *
+ * Uniformity is achieved by generating new random numbers until the one
+ * returned is outside the range [0, 2**32 % upper_bound).  This
+ * guarantees the selected random number will be inside
+ * [2**32 % upper_bound, 2**32) which maps back to [0, upper_bound)
+ * after reduction modulo upper_bound.
+ */
+u_int32_t
+arc4random_uniform(u_int32_t upper_bound)
+{
+	u_int32_t r, min;
+
+	if (upper_bound < 2)
+		return (0);
+
+#if (ULONG_MAX > 0xffffffffUL)
+	min = 0x100000000UL % upper_bound;
+#else
+	/* Calculate (2**32 % upper_bound) avoiding 64-bit math */
+	if (upper_bound > 0x80000000)
+		min = 1 + ~upper_bound;		/* 2**32 - upper_bound */
+	else {
+		/* (2**32 - (x * 2)) % x == 2**32 % x when x <= 2**31 */
+		min = ((0xffffffff - (upper_bound * 2)) + 1) % upper_bound;
+	}
+#endif
+
+	/*
+	 * This could theoretically loop forever but each retry has
+	 * p > 0.5 (worst case, usually far better) of selecting a
+	 * number inside the range we need, so it should rarely need
+	 * to re-roll.
+	 */
+	for (;;) {
+		r = arc4random();
+		if (r >= min)
+			break;
+	}
+
+	return (r % upper_bound);
+}
+
+#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