- (djm) [openbsd-compat/arc4random.c openbsd-compat/chacha_private.h] Pull

   in OpenBSD implementation of arc4random, shortly to replace the existing
   bsd-arc4random.c

1 files changed, 261 insertions, 0 deletions

diff --git a/openbsd-compat/arc4random.c b/openbsd-compat/arc4random.c
new file mode 100644
index 00000000..356e2318
--- /dev/null
+++ b/openbsd-compat/arc4random.c
@@ -0,0 +1,261 @@
+/*	$OpenBSD: arc4random.c,v 1.25 2013/10/01 18:34:57 markus Exp $	*/
+
+/*
+ * Copyright (c) 1996, David Mazieres <dm@uun.org>
+ * Copyright (c) 2008, Damien Miller <djm@openbsd.org>
+ * Copyright (c) 2013, Markus Friedl <markus@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.
+ */
+
+/*
+ * ChaCha based random number generator for OpenBSD.
+ */
+
+#include <fcntl.h>
+#include <limits.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <sys/types.h>
+#include <sys/param.h>
+#include <sys/time.h>
+#include <sys/sysctl.h>
+#include "thread_private.h"
+
+#define KEYSTREAM_ONLY
+#include "chacha_private.h"
+
+#ifdef __GNUC__
+#define inline __inline
+#else				/* !__GNUC__ */
+#define inline
+#endif				/* !__GNUC__ */
+
+#define KEYSZ	32
+#define IVSZ	8
+#define BLOCKSZ	64
+#define RSBUFSZ	(16*BLOCKSZ)
+static int rs_initialized;
+static pid_t rs_stir_pid;
+static chacha_ctx rs;		/* chacha context for random keystream */
+static u_char rs_buf[RSBUFSZ];	/* keystream blocks */
+static size_t rs_have;		/* valid bytes at end of rs_buf */
+static size_t rs_count;		/* bytes till reseed */
+
+static inline void _rs_rekey(u_char *dat, size_t datlen);
+
+static inline void
+_rs_init(u_char *buf, size_t n)
+{
+	if (n < KEYSZ + IVSZ)
+		return;
+	chacha_keysetup(&rs, buf, KEYSZ * 8, 0);
+	chacha_ivsetup(&rs, buf + KEYSZ);
+}
+
+static void
+_rs_stir(void)
+{
+	int     mib[2];
+	size_t	len;
+	u_char rnd[KEYSZ + IVSZ];
+
+	mib[0] = CTL_KERN;
+	mib[1] = KERN_ARND;
+
+	len = sizeof(rnd);
+	sysctl(mib, 2, rnd, &len, NULL, 0);
+
+	if (!rs_initialized) {
+		rs_initialized = 1;
+		_rs_init(rnd, sizeof(rnd));
+	} else
+		_rs_rekey(rnd, sizeof(rnd));
+	memset(rnd, 0, sizeof(rnd));
+
+	/* invalidate rs_buf */
+	rs_have = 0;
+	memset(rs_buf, 0, RSBUFSZ);
+
+	rs_count = 1600000;
+}
+
+static inline void
+_rs_stir_if_needed(size_t len)
+{
+	pid_t pid = getpid();
+
+	if (rs_count <= len || !rs_initialized || rs_stir_pid != pid) {
+		rs_stir_pid = pid;
+		_rs_stir();
+	} else
+		rs_count -= len;
+}
+
+static inline void
+_rs_rekey(u_char *dat, size_t datlen)
+{
+#ifndef KEYSTREAM_ONLY
+	memset(rs_buf, 0,RSBUFSZ);
+#endif
+	/* fill rs_buf with the keystream */
+	chacha_encrypt_bytes(&rs, rs_buf, rs_buf, RSBUFSZ);
+	/* mix in optional user provided data */
+	if (dat) {
+		size_t i, m;
+
+		m = MIN(datlen, KEYSZ + IVSZ);
+		for (i = 0; i < m; i++)
+			rs_buf[i] ^= dat[i];
+	}
+	/* immediately reinit for backtracking resistance */
+	_rs_init(rs_buf, KEYSZ + IVSZ);
+	memset(rs_buf, 0, KEYSZ + IVSZ);
+	rs_have = RSBUFSZ - KEYSZ - IVSZ;
+}
+
+static inline void
+_rs_random_buf(void *_buf, size_t n)
+{
+	u_char *buf = (u_char *)_buf;
+	size_t m;
+
+	_rs_stir_if_needed(n);
+	while (n > 0) {
+		if (rs_have > 0) {
+			m = MIN(n, rs_have);
+			memcpy(buf, rs_buf + RSBUFSZ - rs_have, m);
+			memset(rs_buf + RSBUFSZ - rs_have, 0, m);
+			buf += m;
+			n -= m;
+			rs_have -= m;
+		}
+		if (rs_have == 0)
+			_rs_rekey(NULL, 0);
+	}
+}
+
+static inline void
+_rs_random_u32(u_int32_t *val)
+{
+	_rs_stir_if_needed(sizeof(*val));
+	if (rs_have < sizeof(*val))
+		_rs_rekey(NULL, 0);
+	memcpy(val, rs_buf + RSBUFSZ - rs_have, sizeof(*val));
+	memset(rs_buf + RSBUFSZ - rs_have, 0, sizeof(*val));
+	rs_have -= sizeof(*val);
+	return;
+}
+
+void
+arc4random_stir(void)
+{
+	_ARC4_LOCK();
+	_rs_stir();
+	_ARC4_UNLOCK();
+}
+
+void
+arc4random_addrandom(u_char *dat, int datlen)
+{
+	int m;
+
+	_ARC4_LOCK();
+	if (!rs_initialized)
+		_rs_stir();
+	while (datlen > 0) {
+		m = MIN(datlen, KEYSZ + IVSZ);
+		_rs_rekey(dat, m);
+		dat += m;
+		datlen -= m;
+	}
+	_ARC4_UNLOCK();
+}
+
+u_int32_t
+arc4random(void)
+{
+	u_int32_t val;
+
+	_ARC4_LOCK();
+	_rs_random_u32(&val);
+	_ARC4_UNLOCK();
+	return val;
+}
+
+void
+arc4random_buf(void *buf, size_t n)
+{
+	_ARC4_LOCK();
+	_rs_random_buf(buf, n);
+	_ARC4_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;
+
+	/* 2**32 % x == (2**32 - x) % x */
+	min = -upper_bound % upper_bound;
+
+	/*
+	 * 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);
+	exit(0);
+}
+#endif