Botan  2.6.0
Crypto and TLS for C++11
dev_random.cpp
Go to the documentation of this file.
1 /*
2 * Reader of /dev/random and company
3 * (C) 1999-2009,2013 Jack Lloyd
4 *
5 * Botan is released under the Simplified BSD License (see license.txt)
6 */
7 
8 #include <botan/internal/dev_random.h>
9 #include <botan/exceptn.h>
10 
11 #include <sys/types.h>
12 #include <sys/select.h>
13 #include <sys/stat.h>
14 #include <unistd.h>
15 #include <fcntl.h>
16 
17 namespace Botan {
18 
19 /**
20 Device_EntropySource constructor
21 Open a file descriptor to each (available) device in fsnames
22 */
23 Device_EntropySource::Device_EntropySource(const std::vector<std::string>& fsnames)
24  {
25 #ifndef O_NONBLOCK
26  #define O_NONBLOCK 0
27 #endif
28 
29 #ifndef O_NOCTTY
30  #define O_NOCTTY 0
31 #endif
32 
33  const int flags = O_RDONLY | O_NONBLOCK | O_NOCTTY;
34 
35  m_max_fd = 0;
36 
37  for(auto fsname : fsnames)
38  {
39  int fd = ::open(fsname.c_str(), flags);
40 
41  if(fd < 0)
42  {
43  /*
44  ENOENT or EACCES is normal as some of the named devices may not exist
45  on this system. But any other errno value probably indicates
46  either a bug in the application or file descriptor exhaustion.
47  */
48  if(errno != ENOENT && errno != EACCES)
49  throw Exception("Opening OS RNG device failed with errno " +
50  std::to_string(errno));
51  }
52  else
53  {
54  if(fd > FD_SETSIZE)
55  {
56  ::close(fd);
57  throw Exception("Open of OS RNG succeeded but fd is too large for fd_set");
58  }
59 
60  m_dev_fds.push_back(fd);
61  m_max_fd = std::max(m_max_fd, fd);
62  }
63  }
64  }
65 
66 /**
67 Device_EntropySource destructor: close all open devices
68 */
70  {
71  for(int fd : m_dev_fds)
72  {
73  // ignoring return value here, can't throw in destructor anyway
74  ::close(fd);
75  }
76  }
77 
78 /**
79 * Gather entropy from a RNG device
80 */
82  {
83  size_t bits = 0;
84 
85  if(m_dev_fds.size() > 0)
86  {
87  fd_set read_set;
88  FD_ZERO(&read_set);
89 
90  for(int dev_fd : m_dev_fds)
91  {
92  FD_SET(dev_fd, &read_set);
93  }
94 
95  secure_vector<uint8_t> io_buf(BOTAN_SYSTEM_RNG_POLL_REQUEST);
96 
97  struct ::timeval timeout;
98  timeout.tv_sec = (BOTAN_SYSTEM_RNG_POLL_TIMEOUT_MS / 1000);
99  timeout.tv_usec = (BOTAN_SYSTEM_RNG_POLL_TIMEOUT_MS % 1000) * 1000;
100 
101  if(::select(m_max_fd + 1, &read_set, nullptr, nullptr, &timeout) > 0)
102  {
103  for(int dev_fd : m_dev_fds)
104  {
105  if(FD_ISSET(dev_fd, &read_set))
106  {
107  const ssize_t got = ::read(dev_fd, io_buf.data(), io_buf.size());
108 
109  if(got > 0)
110  {
111  rng.add_entropy(io_buf.data(), static_cast<size_t>(got));
112  bits += got * 8;
113  }
114  }
115  }
116  }
117  }
118 
119  return bits;
120  }
121 
122 }
Device_EntropySource(const std::vector< std::string > &fsnames)
Definition: dev_random.cpp:23
virtual void add_entropy(const uint8_t input[], size_t length)=0
Flags flags(Flag flags)
Definition: p11.h:858
#define O_NONBLOCK
std::string to_string(const BER_Object &obj)
Definition: asn1_obj.cpp:145
#define O_NOCTTY
T select(T mask, T from0, T from1)
Definition: ct_utils.h:106
Definition: alg_id.cpp:13
size_t poll(RandomNumberGenerator &rng) override
Definition: dev_random.cpp:81
std::vector< T, secure_allocator< T > > secure_vector
Definition: secmem.h:88