1 // Copyright (c) 2012 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.
5 #include "base/rand_util.h"
13 #include "base/files/file_util.h"
14 #include "base/lazy_instance.h"
15 #include "base/logging.h"
16 #include "base/posix/eintr_wrapper.h"
20 // We keep the file descriptor for /dev/urandom around so we don't need to
21 // reopen it (which is expensive), and since we may not even be able to reopen
22 // it if we are later put in a sandbox. This class wraps the file descriptor so
23 // we can use LazyInstance to handle opening it on the first access.
27 // AIX has no 64-bit support for open falgs such as -
28 // O_CLOEXEC, O_NOFOLLOW and O_TTY_INIT
29 URandomFd() : fd_(HANDLE_EINTR(open("/dev/urandom", O_RDONLY))) {
30 DCHECK_GE(fd_, 0) << "Cannot open /dev/urandom: " << errno;
33 URandomFd() : fd_(HANDLE_EINTR(open("/dev/urandom", O_RDONLY | O_CLOEXEC))) {
34 DCHECK_GE(fd_, 0) << "Cannot open /dev/urandom: " << errno;
38 ~URandomFd() { close(fd_); }
40 int fd() const { return fd_; }
46 base::LazyInstance<URandomFd>::Leaky g_urandom_fd = LAZY_INSTANCE_INITIALIZER;
52 void RandBytes(void* output, size_t output_length) {
53 const int urandom_fd = g_urandom_fd.Pointer()->fd();
55 ReadFromFD(urandom_fd, static_cast<char*>(output), output_length);
59 int GetUrandomFD(void) {
60 return g_urandom_fd.Pointer()->fd();