Added crypto random-number generator

base/rand_util_posix.cc

 // Copyright (c) 2012 The Chromium 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 "base/rand_util.h"
 
 #include <errno.h>
 #include <fcntl.h>
 #include <unistd.h>
 
@@ skipping 23 matching lines @@
  private:
   int fd_;
 };
 
 base::LazyInstance<URandomFd> g_urandom_fd = LAZY_INSTANCE_INITIALIZER;
 
 }  // namespace
 
 namespace base {
 
+// NOTE: This function must be cryptographically secure. crypto/ relies on this.

[Ryan Sleevi, 2012/08/01 17:52:28]

Rather than say "crypto/ relies on this" (which again, hints that it's a
layering violation and we shouldn't actually have a crypto:: function at all),
point to a bug that indicates that anything that does depend on
cryptographically strong random should be using crypto:: code rather than
base::* functions

Same comment for Win.

// Note: Outputs must return cryptographically strong random numbers.
// http://crbug.com/XYZ

 uint64 RandUint64() {
   uint64 number;
 
   int urandom_fd = g_urandom_fd.Pointer()->fd();
   bool success = file_util::ReadFromFD(urandom_fd,
                                        reinterpret_cast<char*>(&number),
                                        sizeof(number));
   CHECK(success);
 
   return number;
 }
 
 int GetUrandomFD(void) {
   return g_urandom_fd.Pointer()->fd();
 }
 
 }  // namespace base