1 files changed, 252 insertions, 0 deletions
diff --git a/lib/libc/gen/arc4random.c b/lib/libc/gen/arc4random.c
new file mode 100644
index 000000000000..cc65e0131970
--- /dev/null
+++ b/lib/libc/gen/arc4random.c
@@ -0,0 +1,252 @@
+/*	$OpenBSD: arc4random.c,v 1.58 2022/07/31 13:41:45 tb 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>
+ * Copyright (c) 2014, Theo de Raadt <deraadt@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 "namespace.h"
+#if defined(__FreeBSD__)
+#include <assert.h>
+#endif
+#include <fcntl.h>
+#include <limits.h>
+#include <pthread.h>
+#include <signal.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <ssp/ssp.h>
+#include <sys/types.h>
+#include <sys/time.h>
+ 
+#include "libc_private.h"
+#include "un-namespace.h"
+
+#define CHACHA_EMBED
+#define KEYSTREAM_ONLY
+#if defined(__FreeBSD__)
+#define ARC4RANDOM_FXRNG 1
+#else
+#define ARC4RANDOM_FXRNG 0
+#endif
+#include "chacha.c"
+
+#define minimum(a, b) ((a) < (b) ? (a) : (b))
+
+#if defined(__GNUC__) || defined(_MSC_VER)
+#define inline __inline
+#else				/* __GNUC__ || _MSC_VER */
+#define inline
+#endif				/* !__GNUC__ && !_MSC_VER */
+
+#define KEYSZ	32
+#define IVSZ	8
+#define BLOCKSZ	64
+#define RSBUFSZ	(16*BLOCKSZ)
+
+#define REKEY_BASE	(1024*1024) /* NB. should be a power of 2 */
+
+/* Marked INHERIT_ZERO, so zero'd out in fork children. */
+static struct _rs {
+	size_t		rs_have;	/* valid bytes at end of rs_buf */
+	size_t		rs_count;	/* bytes till reseed */
+} *rs;
+
+/* Maybe be preserved in fork children, if _rs_allocate() decides. */
+static struct _rsx {
+	chacha_ctx	rs_chacha;	/* chacha context for random keystream */
+	u_char		rs_buf[RSBUFSZ];	/* keystream blocks */
+#ifdef __FreeBSD__
+	uint32_t	rs_seed_generation;	/* 32-bit userspace RNG version */
+#endif
+} *rsx;
+
+static inline int _rs_allocate(struct _rs **, struct _rsx **);
+static inline void _rs_forkdetect(void);
+#include "arc4random.h"
+
+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;
+
+	if (rs == NULL) {
+		if (_rs_allocate(&rs, &rsx) == -1)
+			_exit(1);
+	}
+
+	chacha_keysetup(&rsx->rs_chacha, buf, KEYSZ * 8);
+	chacha_ivsetup(&rsx->rs_chacha, buf + KEYSZ, NULL);
+}
+
+static void
+_rs_stir(void)
+{
+	u_char rnd[KEYSZ + IVSZ];
+	uint32_t rekey_fuzz = 0;
+
+#if defined(__FreeBSD__)
+	bool need_init;
+
+	/*
+	 * De-couple allocation (which locates the vdso_fxrngp pointer in
+	 * auxinfo) from initialization.  This allows us to read the root seed
+	 * version before we fetch system entropy, maintaining the invariant
+	 * that the PRF was seeded with entropy from rs_seed_generation or a
+	 * later generation.  But never seeded from an earlier generation.
+	 * This invariant prevents us from missing a root reseed event.
+	 */
+	need_init = false;
+	if (rs == NULL) {
+		if (_rs_allocate(&rs, &rsx) == -1)
+			abort();
+		need_init = true;
+	}
+	/*
+	 * Transition period: new userspace on old kernel.  This should become
+	 * a hard error at some point, if the scheme is adopted.
+	 */
+	if (vdso_fxrngp != NULL)
+		rsx->rs_seed_generation =
+		    fxrng_load_acq_generation(&vdso_fxrngp->fx_generation32);
+#endif
+
+	if (getentropy(rnd, sizeof rnd) == -1)
+		_getentropy_fail();
+
+#if !defined(__FreeBSD__)
+	if (!rs)
+		_rs_init(rnd, sizeof(rnd));
+#else /* __FreeBSD__ */
+	assert(rs != NULL);
+	if (need_init)
+		_rs_init(rnd, sizeof(rnd));
+#endif
+	else
+		_rs_rekey(rnd, sizeof(rnd));
+	explicit_bzero(rnd, sizeof(rnd));	/* discard source seed */
+
+	/* invalidate rs_buf */
+	rs->rs_have = 0;
+	memset(rsx->rs_buf, 0, sizeof(rsx->rs_buf));
+
+	/* rekey interval should not be predictable */
+	chacha_encrypt_bytes(&rsx->rs_chacha, (uint8_t *)&rekey_fuzz,
+	    (uint8_t *)&rekey_fuzz, sizeof(rekey_fuzz));
+	rs->rs_count = REKEY_BASE + (rekey_fuzz % REKEY_BASE);
+}
+
+static inline void
+_rs_stir_if_needed(size_t len)
+{
+	_rs_forkdetect();
+	if (!rs || rs->rs_count <= len)
+		_rs_stir();
+	if (rs->rs_count <= len)
+		rs->rs_count = 0;
+	else
+		rs->rs_count -= len;
+}
+
+static inline void
+_rs_rekey(u_char *dat, size_t datlen)
+{
+#ifndef KEYSTREAM_ONLY
+	memset(rsx->rs_buf, 0, sizeof(rsx->rs_buf));
+#endif
+	/* fill rs_buf with the keystream */
+	chacha_encrypt_bytes(&rsx->rs_chacha, rsx->rs_buf,
+	    rsx->rs_buf, sizeof(rsx->rs_buf));
+	/* mix in optional user provided data */
+	if (dat) {
+		size_t i, m;
+
+		m = minimum(datlen, KEYSZ + IVSZ);
+		for (i = 0; i < m; i++)
+			rsx->rs_buf[i] ^= dat[i];
+	}
+	/* immediately reinit for backtracking resistance */
+	_rs_init(rsx->rs_buf, KEYSZ + IVSZ);
+	memset(rsx->rs_buf, 0, KEYSZ + IVSZ);
+	rs->rs_have = sizeof(rsx->rs_buf) - KEYSZ - IVSZ;
+}
+
+static inline void
+_rs_random_buf(void *_buf, size_t n)
+{
+	u_char *buf = (u_char *)_buf;
+	u_char *keystream;
+	size_t m;
+
+	_rs_stir_if_needed(n);
+	while (n > 0) {
+		if (rs->rs_have > 0) {
+			m = minimum(n, rs->rs_have);
+			keystream = rsx->rs_buf + sizeof(rsx->rs_buf)
+			    - rs->rs_have;
+			memcpy(buf, keystream, m);
+			memset(keystream, 0, m);
+			buf += m;
+			n -= m;
+			rs->rs_have -= m;
+		}
+		if (rs->rs_have == 0)
+			_rs_rekey(NULL, 0);
+	}
+}
+
+static inline void
+_rs_random_u32(uint32_t *val)
+{
+	u_char *keystream;
+
+	_rs_stir_if_needed(sizeof(*val));
+	if (rs->rs_have < sizeof(*val))
+		_rs_rekey(NULL, 0);
+	keystream = rsx->rs_buf + sizeof(rsx->rs_buf) - rs->rs_have;
+	memcpy(val, keystream, sizeof(*val));
+	memset(keystream, 0, sizeof(*val));
+	rs->rs_have -= sizeof(*val);
+}
+
+uint32_t
+arc4random(void)
+{
+	uint32_t val;
+
+	_ARC4_LOCK();
+	_rs_random_u32(&val);
+	_ARC4_UNLOCK();
+	return val;
+}
+
+void
+__ssp_real(arc4random_buf)(void *buf, size_t n)
+{
+	_ARC4_LOCK();
+	_rs_random_buf(buf, n);
+	_ARC4_UNLOCK();
+}