Botan  2.7.0
Crypto and TLS for C++11
Public Member Functions | Static Public Member Functions | List of all members
Botan::Device_EntropySource Class Referencefinal

#include <dev_random.h>

Inheritance diagram for Botan::Device_EntropySource:
Botan::Entropy_Source

Public Member Functions

 Device_EntropySource (const std::vector< std::string > &fsnames)
 
std::string name () const override
 
size_t poll (RandomNumberGenerator &rng) override
 
 ~Device_EntropySource ()
 

Static Public Member Functions

static std::unique_ptr< Entropy_Sourcecreate (const std::string &type)
 

Detailed Description

Entropy source reading from kernel devices like /dev/random

Definition at line 20 of file dev_random.h.

Constructor & Destructor Documentation

◆ Device_EntropySource()

Botan::Device_EntropySource::Device_EntropySource ( const std::vector< std::string > &  fsnames)
explicit

Device_EntropySource constructor Open a file descriptor to each (available) device in fsnames

Definition at line 24 of file dev_random.cpp.

References Botan::PKCS11::flags(), O_NOCTTY, O_NONBLOCK, and Botan::ASN1::to_string().

25  {
26 #ifndef O_NONBLOCK
27  #define O_NONBLOCK 0
28 #endif
29 
30 #ifndef O_NOCTTY
31  #define O_NOCTTY 0
32 #endif
33 
34  const int flags = O_RDONLY | O_NONBLOCK | O_NOCTTY;
35 
36  m_max_fd = 0;
37 
38  for(auto fsname : fsnames)
39  {
40  int fd = ::open(fsname.c_str(), flags);
41 
42  if(fd < 0)
43  {
44  /*
45  ENOENT or EACCES is normal as some of the named devices may not exist
46  on this system. But any other errno value probably indicates
47  either a bug in the application or file descriptor exhaustion.
48  */
49  if(errno != ENOENT && errno != EACCES)
50  throw Exception("Opening OS RNG device failed with errno " +
51  std::to_string(errno));
52  }
53  else
54  {
55  if(fd > FD_SETSIZE)
56  {
57  ::close(fd);
58  throw Exception("Open of OS RNG succeeded but fd is too large for fd_set");
59  }
60 
61  m_dev_fds.push_back(fd);
62  m_max_fd = std::max(m_max_fd, fd);
63  }
64  }
65  }
Flags flags(Flag flags)
Definition: p11.h:858
#define O_NONBLOCK
std::string to_string(const BER_Object &obj)
Definition: asn1_obj.cpp:210
#define O_NOCTTY

◆ ~Device_EntropySource()

Botan::Device_EntropySource::~Device_EntropySource ( )

Device_EntropySource destructor: close all open devices

Definition at line 70 of file dev_random.cpp.

71  {
72  for(int fd : m_dev_fds)
73  {
74  // ignoring return value here, can't throw in destructor anyway
75  ::close(fd);
76  }
77  }

Member Function Documentation

◆ create()

std::unique_ptr< Entropy_Source > Botan::Entropy_Source::create ( const std::string &  type)
staticinherited

Return a new entropy source of a particular type, or null Each entropy source may require substantial resources (eg, a file handle or socket instance), so try to share them among multiple RNGs, or just use the preconfigured global list accessed by Entropy_Sources::global_sources()

Definition at line 66 of file entropy_srcs.cpp.

References BOTAN_UNUSED, and Botan::Entropy_Source::name().

Referenced by Botan::Entropy_Sources::Entropy_Sources().

67  {
68 #if defined(BOTAN_HAS_SYSTEM_RNG)
69  if(name == "system_rng" || name == "win32_cryptoapi")
70  {
71  return std::unique_ptr<Entropy_Source>(new System_RNG_EntropySource);
72  }
73 #endif
74 
75 #if defined(BOTAN_HAS_ENTROPY_SRC_RDRAND)
76  if(name == "rdrand")
77  {
78  return std::unique_ptr<Entropy_Source>(new Intel_Rdrand);
79  }
80 #endif
81 
82 #if defined(BOTAN_HAS_ENTROPY_SRC_RDSEED)
83  if(name == "rdseed")
84  {
85  return std::unique_ptr<Entropy_Source>(new Intel_Rdseed);
86  }
87 #endif
88 
89 #if defined(BOTAN_HAS_ENTROPY_SRC_DARWIN_SECRANDOM)
90  if(name == "darwin_secrandom")
91  {
92  return std::unique_ptr<Entropy_Source>(new Darwin_SecRandom);
93  }
94 #endif
95 
96 #if defined(BOTAN_HAS_ENTROPY_SRC_GETENTROPY)
97  if(name == "getentropy")
98  {
99  return std::unique_ptr<Entropy_Source>(new Getentropy);
100  }
101 #endif
102 
103 #if defined(BOTAN_HAS_ENTROPY_SRC_DEV_RANDOM)
104  if(name == "dev_random")
105  {
106  return std::unique_ptr<Entropy_Source>(new Device_EntropySource(BOTAN_SYSTEM_RNG_POLL_DEVICES));
107  }
108 #endif
109 
110 #if defined(BOTAN_HAS_ENTROPY_SRC_PROC_WALKER)
111  if(name == "proc_walk")
112  {
113  const std::string root_dir = BOTAN_ENTROPY_PROC_FS_PATH;
114  if(!root_dir.empty())
115  return std::unique_ptr<Entropy_Source>(new ProcWalking_EntropySource(root_dir));
116  }
117 #endif
118 
119 #if defined(BOTAN_HAS_ENTROPY_SRC_WIN32)
120  if(name == "system_stats")
121  {
122  return std::unique_ptr<Entropy_Source>(new Win32_EntropySource);
123  }
124 #endif
125 
127  return std::unique_ptr<Entropy_Source>();
128  }
virtual std::string name() const =0
#define BOTAN_UNUSED(...)
Definition: assert.h:130

◆ name()

std::string Botan::Device_EntropySource::name ( ) const
inlineoverridevirtual
Returns
name identifying this entropy source

Implements Botan::Entropy_Source.

Definition at line 23 of file dev_random.h.

23 { return "dev_random"; }

◆ poll()

size_t Botan::Device_EntropySource::poll ( RandomNumberGenerator rng)
overridevirtual

Gather entropy from a RNG device

Implements Botan::Entropy_Source.

Definition at line 82 of file dev_random.cpp.

References Botan::RandomNumberGenerator::add_entropy(), and Botan::CT::select().

83  {
84  size_t bits = 0;
85 
86  if(m_dev_fds.size() > 0)
87  {
88  fd_set read_set;
89  FD_ZERO(&read_set);
90 
91  for(int dev_fd : m_dev_fds)
92  {
93  FD_SET(dev_fd, &read_set);
94  }
95 
96  secure_vector<uint8_t> io_buf(BOTAN_SYSTEM_RNG_POLL_REQUEST);
97 
98  struct ::timeval timeout;
99  timeout.tv_sec = (BOTAN_SYSTEM_RNG_POLL_TIMEOUT_MS / 1000);
100  timeout.tv_usec = (BOTAN_SYSTEM_RNG_POLL_TIMEOUT_MS % 1000) * 1000;
101 
102  if(::select(m_max_fd + 1, &read_set, nullptr, nullptr, &timeout) > 0)
103  {
104  for(int dev_fd : m_dev_fds)
105  {
106  if(FD_ISSET(dev_fd, &read_set))
107  {
108  const ssize_t got = ::read(dev_fd, io_buf.data(), io_buf.size());
109 
110  if(got > 0)
111  {
112  rng.add_entropy(io_buf.data(), static_cast<size_t>(got));
113  bits += got * 8;
114  }
115  }
116  }
117  }
118  }
119 
120  return bits;
121  }
T select(T mask, T from0, T from1)
Definition: ct_utils.h:106

The documentation for this class was generated from the following files: