If getrandom syscall is unavailable (ENOSYS), try to fallback on /dev…

…/urandom

ext/standard/random.c

@@ -93,14 +93,13 @@ PHPAPI int php_random_bytes(void *bytes, size_t size, zend_bool should_throw)
 	}
 #elif HAVE_DECL_ARC4RANDOM_BUF && ((defined(__OpenBSD__) && OpenBSD >= 201405) || (defined(__NetBSD__) && __NetBSD_Version__ >= 700000001))
 	arc4random_buf(bytes, size);
-#elif defined(__linux__) && defined(SYS_getrandom)
-	/* Linux getrandom(2) syscall */
+#else
 	size_t read_bytes = 0;
-	size_t amount_to_read = 0;
 	ssize_t n;
-
+#if defined(__linux__) && defined(SYS_getrandom)
+	/* Linux getrandom(2) syscall */
 	/* Keep reading until we get enough entropy */
-	do {
+	while (read_bytes < size) {
 		/* Below, (bytes + read_bytes)  is pointer arithmetic.
 
 		   bytes   read_bytes  size
@@ -110,11 +109,16 @@ PHPAPI int php_random_bytes(void *bytes, size_t size, zend_bool should_throw)
 		              amount_to_read
 
 		*/
-		amount_to_read = size - read_bytes;
+		size_t amount_to_read = size - read_bytes;
 		n = syscall(SYS_getrandom, bytes + read_bytes, amount_to_read, 0);
 
 		if (n == -1) {
-			if (errno == EINTR || errno == EAGAIN) {
+			if (errno == ENOSYS) {
+				/* Try to fallback to /dev/urandom */
+				read_bytes = 0;
+				break;
+			}
+			else if (errno == EINTR || errno == EAGAIN) {
 				/* Try again */
 				continue;
 			}
@@ -130,12 +134,11 @@ PHPAPI int php_random_bytes(void *bytes, size_t size, zend_bool should_throw)
 		}
 
 		read_bytes += (size_t) n;
-	} while (read_bytes < size);
-#else
+	}
+#endif
+	if (read_bytes < size) {
 		int    fd = RANDOM_G(fd);
 		struct stat st;
-	size_t read_bytes = 0;
-	ssize_t n;
 
 		if (fd < 0) {
 #if HAVE_DEV_URANDOM
@@ -164,12 +167,11 @@ PHPAPI int php_random_bytes(void *bytes, size_t size, zend_bool should_throw)
 			RANDOM_G(fd) = fd;
 		}
 
-	while (read_bytes < size) {
+		for (read_bytes = 0; read_bytes < size; read_bytes += (size_t) n) {
 			n = read(fd, bytes + read_bytes, size - read_bytes);
 			if (n <= 0) {
 				break;
 			}
-		read_bytes += n;
 		}
 
 		if (read_bytes < size) {
@@ -178,6 +180,7 @@ PHPAPI int php_random_bytes(void *bytes, size_t size, zend_bool should_throw)
 			}
 			return FAILURE;
 		}
+	}
 #endif
 
 	return SUCCESS;