fixes #1083 Random number improvements

4 files changed, 122 insertions, 88 deletions

diff --git a/src/platform/posix/posix_rand.c b/src/platform/posix/posix_rand.c
deleted file mode 100644
index 2b704e2f..00000000
--- a/src/platform/posix/posix_rand.c
+++ /dev/null
@@ -1,88 +0,0 @@
-//
-// Copyright 2018 Staysail Systems, Inc. <info@staysail.tech>
-// Copyright 2018 Capitar IT Group BV <info@capitar.com>
-//
-// This software is supplied under the terms of the MIT License, a
-// copy of which should be located in the distribution where this
-// file was obtained (LICENSE.txt).  A copy of the license may also be
-// found online at https://opensource.org/licenses/MIT.
-//
-
-// POSIX clock stuff.
-#include "core/nng_impl.h"
-
-#ifdef NNG_PLATFORM_POSIX
-
-#include <errno.h>
-#include <fcntl.h>
-#include <stdlib.h>
-#include <string.h>
-#include <sys/types.h>
-#include <sys/utsname.h>
-#include <time.h>
-#include <unistd.h>
-
-#if defined(NNG_USE_GETRANDOM)
-#include <linux/random.h>
-#elif defined(NNG_USE_GETENTROPY)
-#include <sys/random.h>
-#endif
-
-// This structure represents the very barest minimum that we can use as
-// a source of entropy.  We mix these into our initial entropy, but really
-// really really you want to have more data than this available, especially
-// for cryptographic applications.
-struct nni_plat_prng_x {
-	nni_time       now;
-	pid_t          pid;
-	uid_t          uid;
-	struct utsname uts;
-};
-
-void
-nni_plat_seed_prng(void *buf, size_t bufsz)
-{
-	struct nni_plat_prng_x x;
-	size_t                 i;
-
-	memset(buf, 0, bufsz);
-
-#if defined(NNG_USE_GETRANDOM)
-	// Latest Linux has a nice API here.
-	(void) getrandom(buf, bufsz, 0);
-#elif defined(NNG_USE_GETENTROPY)
-	// Modern BSD systems prefer this, but can only generate 256 bytes
-	(void) getentropy(buf, bufsz > 256 ? 256 : 0);
-#elif defined(NNG_USE_ARC4RANDOM)
-	// This uses BSD style pRNG seeded from the kernel in libc.
-	(void) arc4random_buf(buf, bufsz);
-#elif defined(NNG_USE_DEVURANDOM)
-	// The historic /dev/urandom device.  This is not as a good as
-	// a system call, since file descriptor attacks are possible,
-	// and it may need special permissions.  We choose /dev/urandom
-	// over /dev/random to avoid diminishing the system entropy.
-	int fd;
-
-	if ((fd = open("/dev/urandom", O_RDONLY)) >= 0) {
-		(void) read(fd, buf, bufsz);
-		(void) close(fd);
-	}
-#endif
-
-	// As a special extra guard, let's mixin the data from the
-	// following system calls.  This ensures that even on the most
-	// limited of systems, we have at least *some* level of randomness.
-	// The mixing is done in a way to avoid diminishing entropy we may
-	// have already collected.
-	memset(&x, 0, sizeof(x)); // satisfy valgrind
-	x.now = nni_clock();
-	x.pid = getpid();
-	x.uid = getuid();
-	uname(&x.uts);
-
-	for (i = 0; (i < bufsz) && (i < sizeof(x)); i++) {
-		((uint8_t *) buf)[i] ^= ((uint8_t *) &x)[i];
-	}
-}
-
-#endif // NNG_PLATFORM_POSIX
diff --git a/src/platform/posix/posix_rand_arc4random.c b/src/platform/posix/posix_rand_arc4random.c
new file mode 100644
index 00000000..a3cc265b
--- /dev/null
+++ b/src/platform/posix/posix_rand_arc4random.c
@@ -0,0 +1,24 @@
+//
+// Copyright 2020 Staysail Systems, Inc. <info@staysail.tech>
+//
+// This software is supplied under the terms of the MIT License, a
+// copy of which should be located in the distribution where this
+// file was obtained (LICENSE.txt).  A copy of the license may also be
+// found online at https://opensource.org/licenses/MIT.
+//
+
+// arc4random is the preferred source of cryptographic random numbers
+// on any platform where it is found.
+#include <stdlib.h>
+
+#include "core/nng_impl.h"
+
+#ifdef NNG_HAVE_ARC4RANDOM
+
+uint32_t
+nni_random(void)
+{
+	return (arc4random());
+}
+
+#endif
\ No newline at end of file
diff --git a/src/platform/posix/posix_rand_getrandom.c b/src/platform/posix/posix_rand_getrandom.c
new file mode 100644
index 00000000..489b2c76
--- /dev/null
+++ b/src/platform/posix/posix_rand_getrandom.c
@@ -0,0 +1,40 @@
+//
+// Copyright 2020 Staysail Systems, Inc. <info@staysail.tech>
+//
+// This software is supplied under the terms of the MIT License, a
+// copy of which should be located in the distribution where this
+// file was obtained (LICENSE.txt).  A copy of the license may also be
+// found online at https://opensource.org/licenses/MIT.
+//
+
+// getrandom is not as nice as arc4random, but on platforms where it
+// exists and arc4random does not, we should use it.
+//
+// getrandom will block only if the urandom device is not seeded yet.
+// That can only happen during very early boot (earlier than we should
+// normally be running.  This is the only time it can fail with correct
+// arguments, and then only if it is interrupted with a signal.
+
+#include <sys/random.h>
+
+#include "core/nng_impl.h"
+
+#ifdef NNG_HAVE_GETRANDOM
+
+uint32_t
+nni_random(void)
+{
+	uint32_t val;
+
+	// Documentation claims that as long as we are not using
+	// GRND_RANDOM and buflen < 256, this should never fail.
+	// The exception here is that we could fail if for some
+	// reason we got a signal while blocked at very early boot
+	// (i.e. /dev/urandom was not yet seeded).
+	if (getrandom(&val, sizeof(val), 0) != sizeof(val)) {
+		nni_panic("getrandom failed");
+	}
+	return (val);
+}
+
+#endif
\ No newline at end of file
diff --git a/src/platform/posix/posix_rand_urandom.c b/src/platform/posix/posix_rand_urandom.c
new file mode 100644
index 00000000..32ea6a51
--- /dev/null
+++ b/src/platform/posix/posix_rand_urandom.c
@@ -0,0 +1,58 @@
+//
+// Copyright 2020 Staysail Systems, Inc. <info@staysail.tech>
+//
+// This software is supplied under the terms of the MIT License, a
+// copy of which should be located in the distribution where this
+// file was obtained (LICENSE.txt).  A copy of the license may also be
+// found online at https://opensource.org/licenses/MIT.
+//
+
+#include <fcntl.h>
+#include <pthread.h>
+#include <stdint.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+#include "core/nng_impl.h"
+
+// The historic /dev/urandom device.  This is not as a good as
+// a system call, since file descriptor attacks are possible,  and it may
+// need special permissions. Modern advice is to always use /dev/urandom
+// unless you have very particular reasons for doing otherwise.
+// If you're in this code base, you're probably on either an ancient OS,
+// or one of the off-beat ones that hasn't updated for support with
+// arc4random or getrandom.
+
+// We could use ISAAC or something like that to seed it only once,
+// but instead we just keep our file descriptor open.  This will have
+// the apparent effect of leaking these file descriptors across fork.
+
+static int             urandom_fd   = -1;
+static pthread_mutex_t urandom_lock = PTHREAD_MUTEX_INITIALIZER;
+
+#ifndef O_CLOEXEC
+#define O_CLOEXEC 0u
+#endif
+
+uint32_t
+nni_random(void)
+{
+	int      fd;
+	uint32_t val;
+
+	(void) pthread_mutex_lock(&urandom_lock);
+	if ((fd = urandom_fd) == -1) {
+		if ((fd = open("/dev/urandom", O_RDONLY | O_CLOEXEC)) < 0) {
+			(void) pthread_mutex_unlock(&urandom_lock);
+			nni_panic("failed to open /dev/urandom");
+		}
+		urandom_fd = fd;
+	}
+	(void) pthread_mutex_unlock(&urandom_lock);
+
+	if (read(fd, &val, sizeof(val)) != sizeof(val)) {
+		nni_panic("failed reading /dev/urandom");
+	}
+	return (val);
+}
\ No newline at end of file