1// Copyright (c) 2008 The Chromium Authors. All rights reserved. 2// Use of this source code is governed by a BSD-style license that can be 3// found in the LICENSE file. 4 5#include "base/rand_util.h" 6#include "base/rand_util_c.h" 7 8#include <errno.h> 9#include <fcntl.h> 10#include <unistd.h> 11 12#include "base/file_util.h" 13#include "base/lazy_instance.h" 14#include "base/logging.h" 15 16namespace { 17 18// We keep the file descriptor for /dev/urandom around so we don't need to 19// reopen it (which is expensive), and since we may not even be able to reopen 20// it if we are later put in a sandbox. This class wraps the file descriptor so 21// we can use LazyInstance to handle opening it on the first access. 22class URandomFd { 23 public: 24 URandomFd() { 25 fd_ = open("/dev/urandom", O_RDONLY); 26 CHECK_GE(fd_, 0) << "Cannot open /dev/urandom: " << errno; 27 } 28 29 ~URandomFd() { 30 close(fd_); 31 } 32 33 int fd() const { return fd_; } 34 35 private: 36 int fd_; 37}; 38 39base::LazyInstance<URandomFd> g_urandom_fd(base::LINKER_INITIALIZED); 40 41} // namespace 42 43namespace base { 44 45uint64 RandUint64() { 46 uint64 number; 47 48 int urandom_fd = g_urandom_fd.Pointer()->fd(); 49 bool success = file_util::ReadFromFD(urandom_fd, 50 reinterpret_cast<char*>(&number), 51 sizeof(number)); 52 CHECK(success); 53 54 return number; 55} 56 57} // namespace base 58 59int GetUrandomFD(void) { 60 return g_urandom_fd.Pointer()->fd(); 61} 62