- (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 000000000..356e23181
--- /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