Use explicit_bzero() instead of memset() on buffers going out of scope.

Also, zero the SHA256 context.
suggested by "eric" in a comment on an opensslrampage.org post
ok miod@ deraadt@

src/lib/libcrypto/arc4random/getentropy_linux.c

@@ -1,4 +1,4 @@
-/*	$OpenBSD: getentropy_linux.c,v 1.29 2014/07/21 19:15:56 deraadt Exp $	*/
+/*	$OpenBSD: getentropy_linux.c,v 1.30 2014/07/21 20:19:47 guenther Exp $	*/
 
 /*
  * Copyright (c) 2014 Theo de Raadt <deraadt@openbsd.org>
@@ -539,7 +539,8 @@ getentropy_fallback(void *buf, size_t len)
 		memcpy((char *)buf + i, results, min(sizeof(results), len - i));
 		i += min(sizeof(results), len - i);
 	}
-	memset(results, 0, sizeof results);
+	explicit_bzero(&ctx, sizeof ctx);
+	explicit_bzero(results, sizeof results);
 	if (gotdata(buf, len) == 0) {
 		errno = save_errno;
 		return 0;		/* satisfied */

src/lib/libcrypto/arc4random/getentropy_osx.c

@@ -1,4 +1,4 @@
-/*	$OpenBSD: getentropy_osx.c,v 1.7 2014/07/19 16:12:00 deraadt Exp $	*/
+/*	$OpenBSD: getentropy_osx.c,v 1.8 2014/07/21 20:19:47 guenther Exp $	*/
 
 /*
  * Copyright (c) 2014 Theo de Raadt <deraadt@openbsd.org>
@@ -418,7 +418,8 @@ getentropy_fallback(void *buf, size_t len)
 		memcpy((char *)buf + i, results, min(sizeof(results), len - i));
 		i += min(sizeof(results), len - i);
 	}
-	memset(results, 0, sizeof results);
+	explicit_bzero(&ctx, sizeof ctx);
+	explicit_bzero(results, sizeof results);
 	if (gotdata(buf, len) == 0) {
 		errno = save_errno;
 		return 0;		/* satisfied */

src/lib/libcrypto/arc4random/getentropy_solaris.c

@@ -1,4 +1,4 @@
-/*	$OpenBSD: getentropy_solaris.c,v 1.8 2014/07/19 16:12:00 deraadt Exp $	*/
+/*	$OpenBSD: getentropy_solaris.c,v 1.9 2014/07/21 20:19:47 guenther Exp $	*/
 
 /*
  * Copyright (c) 2014 Theo de Raadt <deraadt@openbsd.org>
@@ -434,7 +434,8 @@ getentropy_fallback(void *buf, size_t len)
 		memcpy((char *)buf + i, results, min(sizeof(results), len - i));
 		i += min(sizeof(results), len - i);
 	}
-	memset(results, 0, sizeof results);
+	explicit_bzero(&ctx, sizeof ctx);
+	explicit_bzero(results, sizeof results);
 	if (gotdata(buf, len) == 0) {
 		errno = save_errno;
 		return 0;		/* satisfied */

src/lib/libcrypto/crypto/getentropy_linux.c

@@ -1,4 +1,4 @@
-/*	$OpenBSD: getentropy_linux.c,v 1.29 2014/07/21 19:15:56 deraadt Exp $	*/
+/*	$OpenBSD: getentropy_linux.c,v 1.30 2014/07/21 20:19:47 guenther Exp $	*/
 
 /*
  * Copyright (c) 2014 Theo de Raadt <deraadt@openbsd.org>
@@ -539,7 +539,8 @@ getentropy_fallback(void *buf, size_t len)
 		memcpy((char *)buf + i, results, min(sizeof(results), len - i));
 		i += min(sizeof(results), len - i);
 	}
-	memset(results, 0, sizeof results);
+	explicit_bzero(&ctx, sizeof ctx);
+	explicit_bzero(results, sizeof results);
 	if (gotdata(buf, len) == 0) {
 		errno = save_errno;
 		return 0;		/* satisfied */

src/lib/libcrypto/crypto/getentropy_osx.c

@@ -1,4 +1,4 @@
-/*	$OpenBSD: getentropy_osx.c,v 1.7 2014/07/19 16:12:00 deraadt Exp $	*/
+/*	$OpenBSD: getentropy_osx.c,v 1.8 2014/07/21 20:19:47 guenther Exp $	*/
 
 /*
  * Copyright (c) 2014 Theo de Raadt <deraadt@openbsd.org>
@@ -418,7 +418,8 @@ getentropy_fallback(void *buf, size_t len)
 		memcpy((char *)buf + i, results, min(sizeof(results), len - i));
 		i += min(sizeof(results), len - i);
 	}
-	memset(results, 0, sizeof results);
+	explicit_bzero(&ctx, sizeof ctx);
+	explicit_bzero(results, sizeof results);
 	if (gotdata(buf, len) == 0) {
 		errno = save_errno;
 		return 0;		/* satisfied */

src/lib/libcrypto/crypto/getentropy_solaris.c

@@ -1,4 +1,4 @@
-/*	$OpenBSD: getentropy_solaris.c,v 1.8 2014/07/19 16:12:00 deraadt Exp $	*/
+/*	$OpenBSD: getentropy_solaris.c,v 1.9 2014/07/21 20:19:47 guenther Exp $	*/
 
 /*
  * Copyright (c) 2014 Theo de Raadt <deraadt@openbsd.org>
@@ -434,7 +434,8 @@ getentropy_fallback(void *buf, size_t len)
 		memcpy((char *)buf + i, results, min(sizeof(results), len - i));
 		i += min(sizeof(results), len - i);
 	}
-	memset(results, 0, sizeof results);
+	explicit_bzero(&ctx, sizeof ctx);
+	explicit_bzero(results, sizeof results);
 	if (gotdata(buf, len) == 0) {
 		errno = save_errno;
 		return 0;		/* satisfied */