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 16 namespace { 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. 22 class URandomFd { 23 public: URandomFd()24 URandomFd() { 25 fd_ = open("/dev/urandom", O_RDONLY); 26 CHECK_GE(fd_, 0) << "Cannot open /dev/urandom: " << errno; 27 } 28 ~URandomFd()29 ~URandomFd() { 30 close(fd_); 31 } 32 fd() const33 int fd() const { return fd_; } 34 35 private: 36 int fd_; 37 }; 38 39 base::LazyInstance<URandomFd> g_urandom_fd(base::LINKER_INITIALIZED); 40 41 } // namespace 42 43 namespace base { 44 RandUint64()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 GetUrandomFD(void)59int GetUrandomFD(void) { 60 return g_urandom_fd.Pointer()->fd(); 61 } 62