1 files changed, 271 insertions, 127 deletions

diff --git a/compat/arc4random.c b/compat/arc4random.c
index 90098127c954..d61d61ffa788 100644
--- a/compat/arc4random.c
+++ b/compat/arc4random.c
@@ -1,173 +1,317 @@
+/*	$OpenBSD: arc4random.c,v 1.58 2022/07/31 13:41:45 tb Exp $	*/
+
 /*
- * Arc4 random number generator for OpenBSD.
- * Copyright 1996 David Mazieres <dm@lcs.mit.edu>.
+ * 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.
  *
- * Modification and redistribution in source and binary forms is
- * permitted provided that due credit is given to the author and the
- * OpenBSD project by leaving this copyright notice intact.
+ * 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.
  */
 
 /*
- * 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.
+ * ChaCha based random number generator for OpenBSD.
  */
 
-#include <sys/time.h>
+/*
+ * OPENBSD ORIGINAL: lib/libc/crypt/arc4random.c
+ *                   lib/libc/crypt/arc4random.h
+ */
+
+#include "config.h"
 
 #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/time.h>
 
-#include "arc4random.h"
+#if defined(HAVE_OPENSSL)
+#include <openssl/rand.h>
+#endif
 
-struct arc4_stream {
-	uint8_t i;
-	uint8_t j;
-	uint8_t s[256];
-	size_t count;
-	pid_t stir_pid;
-	int fd;
-};
+#define KEYSTREAM_ONLY
+#include "chacha_private.h"
 
-#define S(n) (n)
-#define S4(n) S(n), S(n + 1), S(n + 2), S(n + 3)
-#define S16(n) S4(n), S4(n + 4), S4(n + 8), S4(n + 12)
-#define S64(n) S16(n), S16(n + 16), S16(n + 32), S16(n + 48)
-#define S256 S64(0), S64(64), S64(128), S64(192)
+#define minimum(a, b) ((a) < (b) ? (a) : (b))
 
-static struct arc4_stream rs = { .i = 0xff, .j = 0, .s = { S256 },
-                    .count = 0, .stir_pid = 0, .fd = -1 };
+#if defined(__GNUC__) || defined(_MSC_VER)
+#define inline __inline
+#else				/* __GNUC__ || _MSC_VER */
+#define inline
+#endif				/* !__GNUC__ && !_MSC_VER */
 
-#undef S
-#undef S4
-#undef S16
-#undef S64
-#undef S256
+#define KEYSZ	32
+#define IVSZ	8
+#define BLOCKSZ	64
+#define RSBUFSZ	(16*BLOCKSZ)
 
-static void
-arc4_addrandom(struct arc4_stream *as, unsigned char *dat, int datlen)
+#define REKEY_BASE	(1024*1024) /* NB. should be a power of 2 */
+
+/* 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 int _dhcpcd_rand_fd = -1;	/* /dev/urandom fd */
+
+static int _dhcpcd_getentropy(void *, size_t);
+static inline int _rs_allocate(struct _rs **, struct _rsx **);
+
+/* dhcpcd needs to hold onto the fd at fork due to privsep */
+#if 0
+static inline void _rs_forkdetect(void);
+#else
+#define _rs_forkdetect()
+#define _rs_forkhandler()
+#endif
+
+/* Inline "arc4random.h" */
+#include <sys/types.h>
+#include <sys/mman.h>
+
+static inline void _rs_rekey(u_char *dat, size_t datlen);
+
+/* dhcpcd isn't multithreaded */
+#define _ARC4_LOCK()
+#define _ARC4_UNLOCK()
+
+static int
+_dhcpcd_getentropy(void *buf, size_t length)
+{
+	struct timeval	 tv;
+	uint8_t		*rand = (uint8_t *)buf;
+
+#if defined (HAVE_OPENSSL)
+	if (RAND_priv_bytes(buf, (int)length) == 1)
+		return (0);
+#endif
+
+	if (length < sizeof(tv)) {
+		gettimeofday(&tv, NULL);
+		memcpy(buf, &tv, sizeof(tv));
+		length -= sizeof(tv);
+		rand += sizeof(tv);
+	}
+	if (_dhcpcd_rand_fd == -1)
+		_dhcpcd_rand_fd = open("/dev/urandom", O_RDONLY | O_NONBLOCK);
+	if (_dhcpcd_rand_fd != -1) {
+		/* coverity[check_return] */
+		(void)read(_dhcpcd_rand_fd, rand, length);
+	}
+
+	/* Never fail. If there is an error reading from /dev/urandom,
+         * just use what is on the stack. */
+	return (0);
+}
+
+static inline void
+_getentropy_fail(void)
+{
+	raise(SIGKILL);
+}
+
+#if 0
+static volatile sig_atomic_t _rs_forked;
+
+static inline void
+_rs_forkhandler(void)
+{
+	_rs_forked = 1;
+}
+
+static inline void
+_rs_forkdetect(void)
 {
-	int n;
-	uint8_t si;
-
-	as->i--;
-	for (n = 0; n < 256; n++) {
-		as->i = (uint8_t)(as->i + 1);
-		si = as->s[as->i];
-		as->j = (uint8_t)(as->j + si + dat[n % datlen]);
-		as->s[as->i] = as->s[as->j];
-		as->s[as->j] = si;
+	static pid_t _rs_pid = 0;
+	pid_t pid = getpid();
+
+        /* XXX unusual calls to clone() can bypass checks */
+	if (_rs_pid == 0 || _rs_pid == 1 || _rs_pid != pid || _rs_forked) {
+		_rs_pid = pid;
+		_rs_forked = 0;
+		if (rs)
+			memset(rs, 0, sizeof(*rs));
 	}
-	as->j = as->i;
 }
+#endif
 
-static uint8_t
-arc4_getbyte(struct arc4_stream *as)
+static inline int
+_rs_allocate(struct _rs **rsp, struct _rsx **rsxp)
 {
-	uint8_t si, sj;
-
-	as->i = (uint8_t)(as->i + 1);
-	si = as->s[as->i];
-	as->j = (uint8_t)(as->j + si);
-	sj = as->s[as->j];
-	as->s[as->i] = sj;
-	as->s[as->j] = si;
-	return (as->s[(si + sj) & 0xff]);
+	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(*rsp, sizeof(**rsp));
+		*rsp = NULL;
+		return (-1);
+	}
+
+	_rs_forkhandler();
+	return (0);
 }
 
-static uint32_t
-arc4_getword(struct arc4_stream *as)
+static inline void
+_rs_init(u_char *buf, size_t n)
 {
-	int val;
+	if (n < KEYSZ + IVSZ)
+		return;
+
+	if (rs == NULL) {
+		if (_rs_allocate(&rs, &rsx) == -1)
+			_exit(1);
+	}
 
-	val = (int)((unsigned int)arc4_getbyte(as) << 24);
-	val |= arc4_getbyte(as) << 16;
-	val |= arc4_getbyte(as) << 8;
-	val |= arc4_getbyte(as);
-	return (uint32_t)val;
+	chacha_keysetup(&rsx->rs_chacha, buf, KEYSZ * 8);
+	chacha_ivsetup(&rsx->rs_chacha, buf + KEYSZ);
 }
 
-/* We don't care about any error on read, just use what we have
- * on the stack. So mask off this GCC warning. */
-#pragma GCC diagnostic ignored "-Wunused-result"
 static void
-arc4_stir(struct arc4_stream *as)
+_rs_stir(void)
 {
-	struct {
-		struct timeval tv;
-		unsigned int rnd[(128 - sizeof(struct timeval)) /
-			sizeof(unsigned int)];
-	}       rdat;
-	size_t n;
-
-	gettimeofday(&rdat.tv, NULL);
-	if (as->fd == -1) {
-#ifndef O_CLOEXEC
-		int fd_opts;
-#endif
+	u_char rnd[KEYSZ + IVSZ];
+	uint32_t rekey_fuzz = 0;
 
-		as->fd = open("/dev/urandom", O_RDONLY | O_NONBLOCK
-#ifdef O_CLOEXEC
-		| O_CLOEXEC
+	if (_dhcpcd_getentropy(rnd, sizeof rnd) == -1)
+		_getentropy_fail();
+
+	if (!rs)
+		_rs_init(rnd, sizeof(rnd));
+	else
+		_rs_rekey(rnd, sizeof(rnd));
+#if defined(HAVE_EXPLICIT_BZERO)
+	explicit_bzero(rnd, sizeof(rnd));	/* discard source seed */
+#elif defined(HAVE_MEMSET_EXPLICIT)
+	(void)memset_explicit(rnd, 0, sizeof(rnd));
+#elif defined(HAVE_MEMSET_S)
+	(void)memset_s(rnd, sizeof(rnd), 0, sizeof(rnd));
+#else
+#warning potentially insecure use of memset discarding the source seed
+	(void)memset(rnd, 0, sizeof(rnd));	/* discard source seed */
 #endif
-		);
-#ifndef O_CLOEXEC
-		if (as->fd != -1 &&
-		    (fd_opts = fcntl(as->fd, F_GETFD)))
-			fcntl(as->fd, F_SETFD, fd_opts | FD_CLOEXEC);
+
+	/* 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;
 
-	if (as->fd != -1) {
-		/* If there is an error reading, just use what is
-		 * on the stack. */
-		/* coverity[check_return] */
-		(void)read(as->fd, rdat.rnd, sizeof(rdat.rnd));
+		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;
+}
 
-	/* fd < 0?  Ah, what the heck. We'll just take
-	 * whatever was on the stack... */
-	/* coverity[uninit_use_in_call] */
-	arc4_addrandom(as, (void *) &rdat, sizeof(rdat));
-
-	/*
-	 * Throw away the first N words of output, as suggested in the
-	 * paper "Weaknesses in the Key Scheduling Algorithm of RC4"
-	 * by Fluher, Mantin, and Shamir.  (N = 256 in our case.)
-	 */
-	for (n = 0; n < 256 * sizeof(uint32_t); n++)
-		arc4_getbyte(as);
-	as->count = 1600000;
+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 void
-arc4_stir_if_needed(struct arc4_stream *as)
+static inline void
+_rs_random_u32(uint32_t *val)
 {
-	pid_t pid;
-
-	pid = getpid();
-	if (as->count <= sizeof(uint32_t) || as->stir_pid != pid) {
-		as->stir_pid = pid;
-		arc4_stir(as);
-	} else
-		as->count -= sizeof(uint32_t);
+	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()
+arc4random(void)
 {
+	uint32_t val;
+
+	_ARC4_LOCK();
+	_rs_random_u32(&val);
+	_ARC4_UNLOCK();
+	return val;
+}
 
-	arc4_stir_if_needed(&rs);
-	return arc4_getword(&rs);
+void
+arc4random_buf(void *buf, size_t n)
+{
+	_ARC4_LOCK();
+	_rs_random_buf(buf, n);
+	_ARC4_UNLOCK();
 }