Update arc4random() headers from OpenBSD

Split Linux support into its own header separate from the generic Unix
to fix a Linux-specific issue with clone(). Reset rsp to NULL on failure.

COPYING

@@ -429,6 +429,7 @@ Files:
  man/strlcpy.3bsd
  man/strtonum.3bsd
  src/arc4random.c
+ src/arc4random_linux.h
  src/arc4random_openbsd.h
  src/arc4random_uniform.c
  src/arc4random_unix.h

src/Makefile.am

@@ -60,9 +60,10 @@ libbsd_la_LDFLAGS = \
 libbsd_la_SOURCES = \
 	arc4random.c \
 	arc4random.h \
-	arc4random_unix.h \
+	arc4random_linux.h \
 	arc4random_openbsd.h \
 	arc4random_uniform.c \
+	arc4random_unix.h \
 	bsd_getopt.c \
 	chacha_private.h \
 	closefrom.c \

src/arc4random.h

@@ -34,6 +34,8 @@ getentropy(void *buf, size_t len);
 
 #if defined(__OpenBSD__)
 #include "arc4random_openbsd.h"
+#elif defined(__linux__)
+#include "arc4random_linux.h"
 #else
 #include "arc4random_unix.h"
 #endif

src/arc4random_linux.h

@@ -0,0 +1,88 @@
+/*	$OpenBSD: arc4random_linux.h,v 1.11 2016/06/30 12:19:51 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>
+ * 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.
+ */
+
+/*
+ * Stub functions for portability.
+ */
+
+#include <sys/mman.h>
+
+#include <pthread.h>
+#include <signal.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();
+
+	/* 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));
+	}
+}
+
+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(*rsp, sizeof(**rsp));
+		*rsp = NULL;
+		return (-1);
+	}
+
+	_ARC4_ATFORK(_rs_forkhandler);
+	return (0);
+}

src/arc4random_unix.h

@@ -1,4 +1,4 @@
-/*	$OpenBSD: arc4random_linux.h,v 1.8 2014/08/13 06:04:10 deraadt Exp $	*/
+/*	$OpenBSD: arc4random_freebsd.h,v 1.4 2016/06/30 12:19:51 bcook Exp $	*/
 
 /*
  * Copyright (c) 1996, David Mazieres <dm@uun.org>
@@ -84,6 +84,7 @@ _rs_allocate(struct _rs **rsp, struct _rsx **rsxp)
 	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);
 	}