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.
4
5 #include "base/rand_util.h"
6
7 #include <errno.h>
8 #include <fcntl.h>
9 #include <stddef.h>
10 #include <stdint.h>
11 #include <unistd.h>
12
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"
17
18 namespace {
19
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.
24 class URandomFd {
25 public:
26 #if defined(OS_AIX)
27 // AIX has no 64-bit support for open falgs such as -
28 // O_CLOEXEC, O_NOFOLLOW and O_TTY_INIT
URandomFd()29 URandomFd() : fd_(HANDLE_EINTR(open("/dev/urandom", O_RDONLY))) {
30 DCHECK_GE(fd_, 0) << "Cannot open /dev/urandom: " << errno;
31 }
32 #else
33 URandomFd() : fd_(HANDLE_EINTR(open("/dev/urandom", O_RDONLY | O_CLOEXEC))) {
34 DCHECK_GE(fd_, 0) << "Cannot open /dev/urandom: " << errno;
35 }
36 #endif
37
~URandomFd()38 ~URandomFd() { close(fd_); }
39
fd() const40 int fd() const { return fd_; }
41
42 private:
43 const int fd_;
44 };
45
46 base::LazyInstance<URandomFd>::Leaky g_urandom_fd = LAZY_INSTANCE_INITIALIZER;
47
48 } // namespace
49
50 namespace base {
51
RandBytes(void * output,size_t output_length)52 void RandBytes(void* output, size_t output_length) {
53 const int urandom_fd = g_urandom_fd.Pointer()->fd();
54 const bool success =
55 ReadFromFD(urandom_fd, static_cast<char*>(output), output_length);
56 CHECK(success);
57 }
58
GetUrandomFD(void)59 int GetUrandomFD(void) {
60 return g_urandom_fd.Pointer()->fd();
61 }
62
63 } // namespace base
64