Use upstream OpenBSD's arc4random.

The getentropy_linux.c is lightly modified to build on Android, but we're now
completely in sync with upstream OpenBSD's arc4random implementation.

Change-Id: If32229fc28aba908035fb38703190d41ddcabc95

4 files changed, 344 insertions, 0 deletions

diff --git a/libc/upstream-openbsd/android/include/arc4random.h b/libc/upstream-openbsd/android/include/arc4random.h
new file mode 100644
index 0000000..c07257d
--- /dev/null
+++ b/libc/upstream-openbsd/android/include/arc4random.h
@@ -0,0 +1,87 @@
+/*	$OpenBSD: arc4random_linux.h,v 1.7 2014/07/20 20:51:13 bcook 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.
+ */
+
+/*
+ * Stub functions for portability.
+ */
+
+#include <sys/mman.h>
+
+#include <pthread.h>
+#include <signal.h>
+
+// Android gets these from "thread_private.h".
+#include "thread_private.h"
+//static pthread_mutex_t arc4random_mtx = PTHREAD_MUTEX_INITIALIZER;
+//#define _ARC4_LOCK()   pthread_mutex_lock(&arc4random_mtx)
+//#define _ARC4_UNLOCK() pthread_mutex_unlock(&arc4random_mtx)
+
+#ifdef __GLIBC__
+extern void *__dso_handle;
+extern int __register_atfork(void (*)(void), void(*)(void), void (*)(void), void *);
+#define _ARC4_ATFORK(f) __register_atfork(NULL, NULL, (f), __dso_handle)
+#else
+#define _ARC4_ATFORK(f) pthread_atfork(NULL, NULL, (f))
+#endif
+
+static inline void
+_getentropy_fail(void)
+{
+	raise(SIGKILL);
+}
+
+static volatile sig_atomic_t _rs_forked;
+
+static inline void
+_rs_forkhandler(void)
+{
+	_rs_forked = 1;
+}
+
+static inline void
+_rs_forkdetect(void)
+{
+	static pid_t _rs_pid = 0;
+	pid_t pid = getpid();
+
+	if (_rs_pid == 0 || _rs_pid != pid || _rs_forked) {
+		_rs_pid = pid;
+		_rs_forked = 0;
+		if (rs)
+			memset(rs, 0, sizeof(*rs));
+	}
+}
+
+static inline int
+_rs_allocate(struct _rs **rsp, struct _rsx **rsxp)
+{
+	if ((*rsp = mmap(NULL, sizeof(**rsp), PROT_READ|PROT_WRITE,
+	    MAP_ANON|MAP_PRIVATE, -1, 0)) == MAP_FAILED)
+		return (-1);
+
+	if ((*rsxp = mmap(NULL, sizeof(**rsxp), PROT_READ|PROT_WRITE,
+	    MAP_ANON|MAP_PRIVATE, -1, 0)) == MAP_FAILED) {
+		munmap(*rsxp, sizeof(**rsxp));
+		return (-1);
+	}
+
+	_ARC4_ATFORK(_rs_forkhandler);
+	return (0);
+}
diff --git a/libc/upstream-openbsd/android/include/openbsd-compat.h b/libc/upstream-openbsd/android/include/openbsd-compat.h
index 5827a82..34ad2c5 100644
--- a/libc/upstream-openbsd/android/include/openbsd-compat.h
+++ b/libc/upstream-openbsd/android/include/openbsd-compat.h
@@ -18,6 +18,7 @@
 #define _BIONIC_OPENBSD_COMPAT_H_included
 
 #include <sys/cdefs.h>
+#include <stddef.h> // For size_t.
 
 #define __USE_BSD
 
@@ -36,6 +37,11 @@
 /* OpenBSD has this, but we can't really implement it correctly on Linux. */
 #define issetugid() 0
 
+#define explicit_bzero(p, s) memset(p, 0, s)
+
+/* We have OpenBSD's getentropy_linux.c, but we don't mention getentropy in any header. */
+__LIBC_HIDDEN__ extern int getentropy(void*, size_t);
+
 /* LP32 NDK ctype.h contained references to these. */
 __LIBC64_HIDDEN__ extern const short* _tolower_tab_;
 __LIBC64_HIDDEN__ extern const short* _toupper_tab_;
diff --git a/libc/upstream-openbsd/lib/libc/crypt/arc4random.c b/libc/upstream-openbsd/lib/libc/crypt/arc4random.c
new file mode 100644
index 0000000..64248b6
--- /dev/null
+++ b/libc/upstream-openbsd/lib/libc/crypt/arc4random.c
@@ -0,0 +1,195 @@
+/*	$OpenBSD: arc4random.c,v 1.50 2014/07/21 18:13:12 deraadt 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 <signal.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <sys/types.h>
+#include <sys/param.h>
+#include <sys/time.h>
+
+#define KEYSTREAM_ONLY
+#include "chacha_private.h"
+
+#define min(a, b) ((a) < (b) ? (a) : (b))
+#ifdef __GNUC__
+#define inline __inline
+#else				/* !__GNUC__ */
+#define inline
+#endif				/* !__GNUC__ */
+
+#define KEYSZ	32
+#define IVSZ	8
+#define BLOCKSZ	64
+#define RSBUFSZ	(16*BLOCKSZ)
+
+/* Marked MAP_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 */
+} *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)
+			abort();
+	}
+
+	chacha_keysetup(&rsx->rs_chacha, buf, KEYSZ * 8, 0);
+	chacha_ivsetup(&rsx->rs_chacha, buf + KEYSZ);
+}
+
+static void
+_rs_stir(void)
+{
+	u_char rnd[KEYSZ + IVSZ];
+
+	if (getentropy(rnd, sizeof rnd) == -1)
+		_getentropy_fail();
+
+	if (!rs)
+		_rs_init(rnd, sizeof(rnd));
+	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));
+
+	rs->rs_count = 1600000;
+}
+
+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 = min(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 = min(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
+arc4random_buf(void *buf, size_t n)
+{
+	_ARC4_LOCK();
+	_rs_random_buf(buf, n);
+	_ARC4_UNLOCK();
+}
diff --git a/libc/upstream-openbsd/lib/libc/crypt/arc4random_uniform.c b/libc/upstream-openbsd/lib/libc/crypt/arc4random_uniform.c
new file mode 100644
index 0000000..1aa9a62
--- /dev/null
+++ b/libc/upstream-openbsd/lib/libc/crypt/arc4random_uniform.c
@@ -0,0 +1,56 @@
+/*	$OpenBSD: arc4random_uniform.c,v 1.1 2014/07/12 13:24:54 deraadt Exp $	*/
+
+/*
+ * 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.
+ */
+
+#include <sys/types.h>
+#include <stdlib.h>
+
+/*
+ * 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.
+ */
+uint32_t
+arc4random_uniform(uint32_t upper_bound)
+{
+	uint32_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;
+}