Non-SFI mode: Implement nacl_irt_random only for nacl_helper_nonsfi.

src/nonsfi/irt/irt_random.c

+/*
+ * Copyright (c) 2014 The Native Client Authors. All rights reserved.
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "native_client/src/nonsfi/irt/irt_random.h"
+#include "native_client/src/untrusted/nacl/nacl_random.h"
+
+#include <errno.h>
+#include <fcntl.h>
+#include <stdlib.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+static int g_urandom_fd = -1;
+
+void nonsfi_set_urandom_fd(int fd) {
+  g_urandom_fd = fd;
+}
+
+/*
+ * Note: This library provides the nacl_secure_random_init for testing purposes.
+ */
+int nacl_secure_random_init(void) {
+  return 0;  /* Success */
+}
+
+int nacl_secure_random(void *buf, size_t count, size_t *nread) {
+  if (g_urandom_fd < 0) {
+    /*
+     * If the fd for /dev/urandom is not initialized, try to open it.
+     * This happens on testing, or in nonsfi_loader. Abort on failure.
+     */
+    g_urandom_fd = open("/dev/urandom", O_RDONLY);
+    if (g_urandom_fd < 0)
+      abort();
+  }
+
+  int result = read(g_urandom_fd, buf, count);
+  if (result < 0)
+    return errno;
+  *nread = result;
+  return 0;
+}