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 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 38 ~URandomFd() { close(fd_); } 39 40 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 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 59 int GetUrandomFD(void) { 60 return g_urandom_fd.Pointer()->fd(); 61 } 62 63 } // namespace base 64
