Botan  2.13.0
Crypto and TLS for C++11
Public Member Functions | Static Public Member Functions | List of all members
Botan::Intel_Rdrand Class Referencefinal

#include <rdrand.h>

Inheritance diagram for Botan::Intel_Rdrand:
Botan::Entropy_Source

Public Member Functions

std::string name () const override
 
size_t poll (RandomNumberGenerator &rng) override
 

Static Public Member Functions

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

Detailed Description

Entropy source using the rdrand instruction first introduced on Intel's Ivy Bridge architecture.

Definition at line 19 of file rdrand.h.

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 67 of file entropy_srcs.cpp.

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

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

68  {
69 #if defined(BOTAN_HAS_SYSTEM_RNG)
70  if(name == "system_rng" || name == "win32_cryptoapi")
71  {
72  return std::unique_ptr<Entropy_Source>(new System_RNG_EntropySource);
73  }
74 #endif
75 
76 #if defined(BOTAN_HAS_ENTROPY_SRC_RDRAND)
77  if(name == "rdrand")
78  {
79  return std::unique_ptr<Entropy_Source>(new Intel_Rdrand);
80  }
81 #endif
82 
83 #if defined(BOTAN_HAS_ENTROPY_SRC_RDSEED)
84  if(name == "rdseed")
85  {
86  return std::unique_ptr<Entropy_Source>(new Intel_Rdseed);
87  }
88 #endif
89 
90 #if defined(BOTAN_HAS_ENTROPY_SRC_DARN)
91  if(name == "p9_darn")
92  {
93  return std::unique_ptr<Entropy_Source>(new POWER9_DARN);
94  }
95 #endif
96 
97 #if defined(BOTAN_HAS_ENTROPY_SRC_GETENTROPY)
98  if(name == "getentropy")
99  {
100  return std::unique_ptr<Entropy_Source>(new Getentropy);
101  }
102 #endif
103 
104 #if defined(BOTAN_HAS_ENTROPY_SRC_DEV_RANDOM)
105  if(name == "dev_random")
106  {
107  return std::unique_ptr<Entropy_Source>(new Device_EntropySource(BOTAN_SYSTEM_RNG_POLL_DEVICES));
108  }
109 #endif
110 
111 #if defined(BOTAN_HAS_ENTROPY_SRC_PROC_WALKER)
112  if(name == "proc_walk" && OS::running_in_privileged_state() == false)
113  {
114  const std::string root_dir = BOTAN_ENTROPY_PROC_FS_PATH;
115  if(!root_dir.empty())
116  return std::unique_ptr<Entropy_Source>(new ProcWalking_EntropySource(root_dir));
117  }
118 #endif
119 
120 #if defined(BOTAN_HAS_ENTROPY_SRC_WIN32)
121  if(name == "system_stats")
122  {
123  return std::unique_ptr<Entropy_Source>(new Win32_EntropySource);
124  }
125 #endif
126 
128  return std::unique_ptr<Entropy_Source>();
129  }
virtual std::string name() const =0
bool running_in_privileged_state()
Definition: os_utils.cpp:143
#define BOTAN_UNUSED(...)
Definition: assert.h:142

◆ name()

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

Implements Botan::Entropy_Source.

Definition at line 22 of file rdrand.h.

22 { return "rdrand"; }

◆ poll()

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

Perform an entropy gathering poll

Parameters
rngwill be provided with entropy via calls to add_entropy
Returns
conservative estimate of actual entropy added to rng during poll

Implements Botan::Entropy_Source.

Definition at line 14 of file rdrand.cpp.

References Botan::RandomNumberGenerator::add_entropy(), Botan::RDRAND_RNG::available(), and Botan::RDRAND_RNG::randomize().

15  {
16  /*
17  * Intel's documentation for RDRAND at
18  * https://software.intel.com/en-us/articles/intel-digital-random-number-generator-drng-software-implementation-guide
19  * claims that software can guarantee a reseed event by polling enough data:
20  * "There is an upper bound of 511 samples per seed in the implementation
21  * where samples are 128 bits in size and can provide two 64-bit random
22  * numbers each."
23  *
24  * By requesting 8192 bytes we are asking for 512 samples and thus are assured
25  * that at some point in producing the output, at least one reseed of the
26  * internal state will occur.
27  *
28  * The alternative approach is to "Iteratively execute 32 RDRAND invocations
29  * with a 10 us wait period per iteration." however in practice this proves to
30  * be about 20x slower, despite producing much less seed material.
31  */
32  const size_t RDRAND_POLL_BYTES = 8*1024;
33 
35  {
36  RDRAND_RNG rdrand_rng;
37  secure_vector<uint8_t> buf(RDRAND_POLL_BYTES);
38  rdrand_rng.randomize(&buf[0], buf.size());
39  rng.add_entropy(buf.data(), buf.size());
40  }
41 
42  // RDRAND is used but not trusted
43  return 0;
44  }
static bool available()
Definition: rdrand_rng.cpp:85

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