1 files changed, 128 insertions, 118 deletions

diff --git a/sys/libkern/arc4random.c b/sys/libkern/arc4random.c
index ccda6ad5bd50..ad4c6b057e4a 100644
--- a/sys/libkern/arc4random.c
+++ b/sys/libkern/arc4random.c
@@ -1,11 +1,28 @@
 /*-
- * THE BEER-WARE LICENSE
+ * Copyright (c) 2017 The FreeBSD Foundation
+ * All rights reserved.
  *
- * <dan@FreeBSD.ORG> wrote this file.  As long as you retain this notice you
- * can do whatever you want with this stuff.  If we meet some day, and you
- * think this stuff is worth it, you can buy me a beer in return.
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer
+ *    in this position and unchanged.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  *
- * Dan Moschuk
  */
 
 #include <sys/cdefs.h>
@@ -14,173 +31,159 @@ __FBSDID("$FreeBSD$");
 #include <sys/types.h>
 #include <sys/param.h>
 #include <sys/kernel.h>
-#include <sys/random.h>
 #include <sys/libkern.h>
+#include <sys/linker.h>
 #include <sys/lock.h>
+#include <sys/malloc.h>
 #include <sys/mutex.h>
-#include <sys/time.h>
+#include <sys/random.h>
 #include <sys/smp.h>
-#include <sys/malloc.h>
+#include <sys/time.h>
+
+#include <crypto/chacha20/chacha.h>
 
-#define	ARC4_RESEED_BYTES 65536
-#define	ARC4_RESEED_SECONDS 300
-#define	ARC4_KEYBYTES 256
+#define	CHACHA20_RESEED_BYTES	65536
+#define	CHACHA20_RESEED_SECONDS	300
+#define	CHACHA20_KEYBYTES	32
+#define	CHACHA20_BUFFER_SIZE	64
+
+CTASSERT(CHACHA20_KEYBYTES*8 >= CHACHA_MINKEYLEN);
 
 int arc4rand_iniseed_state = ARC4_ENTR_NONE;
 
-MALLOC_DEFINE(M_ARC4RANDOM, "arc4random", "arc4random structures");
+MALLOC_DEFINE(M_CHACHA20RANDOM, "chacha20random", "chacha20random structures");
 
-struct arc4_s {
+struct chacha20_s {
 	struct mtx mtx;
-	u_int8_t i, j;
-	int numruns;
-	u_int8_t sbox[256];
+	int numbytes;
+	int first_time_done;
 	time_t t_reseed;
-
+	u_int8_t m_buffer[CHACHA20_BUFFER_SIZE];
+	struct chacha_ctx ctx;
 } __aligned(CACHE_LINE_SIZE);
 
-static struct arc4_s *arc4inst = NULL;
+static struct chacha20_s *chacha20inst = NULL;
 
-#define ARC4_FOREACH(_arc4) \
-	for (_arc4 = &arc4inst[0]; _arc4 <= &arc4inst[mp_maxid]; _arc4++)
-
-static u_int8_t arc4_randbyte(struct arc4_s *arc4);
-
-static __inline void
-arc4_swap(u_int8_t *a, u_int8_t *b)
-{
-	u_int8_t c;
-
-	c = *a;
-	*a = *b;
-	*b = c;
-}	
+#define CHACHA20_FOREACH(_chacha20) \
+	for (_chacha20 = &chacha20inst[0]; \
+	     _chacha20 <= &chacha20inst[mp_maxid]; \
+	     _chacha20++)
 
 /*
- * Stir our S-box.
+ * Mix up the current context.
  */
 static void
-arc4_randomstir(struct arc4_s* arc4)
+chacha20_randomstir(struct chacha20_s* chacha20)
 {
-	u_int8_t key[ARC4_KEYBYTES];
-	int n;
 	struct timeval tv_now;
+	size_t n, size;
+	u_int8_t key[CHACHA20_KEYBYTES], *data;
+	caddr_t keyfile;
 
 	/*
-	 * XXX: FIX!! This isn't brilliant. Need more confidence.
-	 * This returns zero entropy before random(4) is seeded.
+	 * This is making the best of what may be an insecure
+	 * Situation. If the loader(8) did not have an entropy
+	 * stash from the previous shutdown to load, then we will
+	 * be improperly seeded. The answer is to make sure there
+	 * is an entropy stash at shutdown time.
 	 */
-	(void)read_random(key, ARC4_KEYBYTES);
-	getmicrouptime(&tv_now);
-	mtx_lock(&arc4->mtx);
-	for (n = 0; n < 256; n++) {
-		arc4->j = (arc4->j + arc4->sbox[n] + key[n]) % 256;
-		arc4_swap(&arc4->sbox[n], &arc4->sbox[arc4->j]);
+	(void)read_random(key, CHACHA20_KEYBYTES);
+	if (!chacha20->first_time_done) {
+		keyfile = preload_search_by_type(RANDOM_CACHED_BOOT_ENTROPY_MODULE);
+		if (keyfile != NULL) {
+			data = preload_fetch_addr(keyfile);
+			size = MIN(preload_fetch_size(keyfile), CHACHA20_KEYBYTES);
+			for (n = 0; n < size; n++)
+				key[n] ^= data[n];
+			explicit_bzero(data, size);
+			if (bootverbose)
+				printf("arc4random: read %zu bytes from preloaded cache\n", size);
+		} else
+			printf("arc4random: no preloaded entropy cache\n");
+		chacha20->first_time_done = 1;
 	}
-	arc4->i = arc4->j = 0;
+	getmicrouptime(&tv_now);
+	mtx_lock(&chacha20->mtx);
+	chacha_keysetup(&chacha20->ctx, key, CHACHA20_KEYBYTES*8);
+	chacha_ivsetup(&chacha20->ctx, (u_char *)&tv_now.tv_sec, (u_char *)&tv_now.tv_usec);
 	/* Reset for next reseed cycle. */
-	arc4->t_reseed = tv_now.tv_sec + ARC4_RESEED_SECONDS;
-	arc4->numruns = 0;
-	/*
-	 * 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 = 768 in our case.)
-	 *
-	 * http://dl.acm.org/citation.cfm?id=646557.694759
-	 */
-	for (n = 0; n < 768*4; n++)
-		arc4_randbyte(arc4);
-
-	mtx_unlock(&arc4->mtx);
+	chacha20->t_reseed = tv_now.tv_sec + CHACHA20_RESEED_SECONDS;
+	chacha20->numbytes = 0;
+	mtx_unlock(&chacha20->mtx);
 }
 
 /*
- * Initialize our S-box to its beginning defaults.
+ * Initialize the contexts.
  */
 static void
-arc4_init(void)
+chacha20_init(void)
 {
-	struct arc4_s *arc4;
-	int n;
-
-	arc4inst = malloc((mp_maxid + 1) * sizeof(struct arc4_s),
-			M_ARC4RANDOM, M_NOWAIT | M_ZERO);
-	KASSERT(arc4inst != NULL, ("arc4_init: memory allocation error"));
+	struct chacha20_s *chacha20;
 
-	ARC4_FOREACH(arc4) {
-		mtx_init(&arc4->mtx, "arc4_mtx", NULL, MTX_DEF);
+	chacha20inst = malloc((mp_maxid + 1) * sizeof(struct chacha20_s),
+			M_CHACHA20RANDOM, M_NOWAIT | M_ZERO);
+	KASSERT(chacha20inst != NULL, ("chacha20_init: memory allocation error"));
 
-		arc4->i = arc4->j = 0;
-		for (n = 0; n < 256; n++)
-			arc4->sbox[n] = (u_int8_t) n;
-
-		arc4->t_reseed = -1;
-		arc4->numruns = 0;
+	CHACHA20_FOREACH(chacha20) {
+		mtx_init(&chacha20->mtx, "chacha20_mtx", NULL, MTX_DEF);
+		chacha20->t_reseed = -1;
+		chacha20->numbytes = 0;
+		chacha20->first_time_done = 0;
+		explicit_bzero(chacha20->m_buffer, CHACHA20_BUFFER_SIZE);
+		explicit_bzero(&chacha20->ctx, sizeof(chacha20->ctx));
 	}
 }
-SYSINIT(arc4, SI_SUB_LOCK, SI_ORDER_ANY, arc4_init, NULL);
+SYSINIT(chacha20, SI_SUB_LOCK, SI_ORDER_ANY, chacha20_init, NULL);
 
 
 static void
-arc4_uninit(void)
+chacha20_uninit(void)
 {
-	struct arc4_s *arc4;
-
-	ARC4_FOREACH(arc4) {
-		mtx_destroy(&arc4->mtx);
-	}
+	struct chacha20_s *chacha20;
 
-	free(arc4inst, M_ARC4RANDOM);
+	CHACHA20_FOREACH(chacha20)
+		mtx_destroy(&chacha20->mtx);
+	free(chacha20inst, M_CHACHA20RANDOM);
 }
-
-SYSUNINIT(arc4, SI_SUB_LOCK, SI_ORDER_ANY, arc4_uninit, NULL);
+SYSUNINIT(chacha20, SI_SUB_LOCK, SI_ORDER_ANY, chacha20_uninit, NULL);
 
 
 /*
- * Generate a random byte.
- */
-static u_int8_t
-arc4_randbyte(struct arc4_s *arc4)
-{
-	u_int8_t arc4_t;
-
-	arc4->i = (arc4->i + 1) % 256;
-	arc4->j = (arc4->j + arc4->sbox[arc4->i]) % 256;
-
-	arc4_swap(&arc4->sbox[arc4->i], &arc4->sbox[arc4->j]);
-
-	arc4_t = (arc4->sbox[arc4->i] + arc4->sbox[arc4->j]) % 256;
-	return arc4->sbox[arc4_t];
-}
-
-/*
  * MPSAFE
  */
 void
 arc4rand(void *ptr, u_int len, int reseed)
 {
-	u_char *p;
+	struct chacha20_s *chacha20;
 	struct timeval tv;
-	struct arc4_s *arc4;
+	u_int length;
+	u_int8_t *p;
 
-	if (reseed || atomic_cmpset_int(&arc4rand_iniseed_state,
-			ARC4_ENTR_HAVE, ARC4_ENTR_SEED)) {
-		ARC4_FOREACH(arc4)
-			arc4_randomstir(arc4);
-	}
+	if (reseed || atomic_cmpset_int(&arc4rand_iniseed_state, ARC4_ENTR_HAVE, ARC4_ENTR_SEED))
+		CHACHA20_FOREACH(chacha20)
+			chacha20_randomstir(chacha20);
 
-	arc4 = &arc4inst[curcpu];
+	chacha20 = &chacha20inst[curcpu];
 	getmicrouptime(&tv);
-	if ((arc4->numruns > ARC4_RESEED_BYTES) ||
-		(tv.tv_sec > arc4->t_reseed))
-		arc4_randomstir(arc4);
+	/* We may get unlucky and be migrated off this CPU, but that is expected to be infrequent */
+	if ((chacha20->numbytes > CHACHA20_RESEED_BYTES) || (tv.tv_sec > chacha20->t_reseed))
+		chacha20_randomstir(chacha20);
 
-	mtx_lock(&arc4->mtx);
-	arc4->numruns += len;
+	mtx_lock(&chacha20->mtx);
 	p = ptr;
-	while (len--)
-		*p++ = arc4_randbyte(arc4);
-	mtx_unlock(&arc4->mtx);
+	while (len) {
+		length = MIN(CHACHA20_BUFFER_SIZE, len);
+		chacha_encrypt_bytes(&chacha20->ctx, chacha20->m_buffer, p, length);
+		p += length;
+		len -= length;
+		chacha20->numbytes += length;
+		if (chacha20->numbytes > CHACHA20_RESEED_BYTES) {
+			mtx_unlock(&chacha20->mtx);
+			chacha20_randomstir(chacha20);
+			mtx_lock(&chacha20->mtx);
+		}
+	}
+	mtx_unlock(&chacha20->mtx);
 }
 
 uint32_t
@@ -188,6 +191,13 @@ arc4random(void)
 {
 	uint32_t ret;
 
-	arc4rand(&ret, sizeof ret, 0);
+	arc4rand(&ret, sizeof(ret), 0);
 	return ret;
 }
+
+void
+arc4random_buf(void *ptr, size_t len)
+{
+
+	arc4rand(ptr, len, 0);
+}