Botan::Processor_RNG Class Reference

#include <processor_rng.h>

Inheritance diagram for Botan::Processor_RNG:

Public Member Functions
bool	accepts_input () const override
void	add_entropy (const uint8_t input[], size_t length)
void	add_entropy (std::span< const uint8_t > input)
template<typename T > requires std::is_standard_layout<T>
void	add_entropy_T (const T &t)
virtual void	clear () final override
bool	is_seeded () const override
std::string	name () const override
uint8_t	next_byte ()
uint8_t	next_nonzero_byte ()
	Processor_RNG ()
template<concepts::resizable_byte_buffer T = secure_vector<uint8_t>> requires concepts::default_initializable<T>
T	random_vec (size_t bytes)
void	random_vec (std::span< uint8_t > v)
template<concepts::resizable_byte_buffer T>
void	random_vec (T &v, size_t bytes)
void	randomize (std::span< uint8_t > output)
void	randomize (uint8_t output[], size_t length)
void	randomize_with_input (uint8_t output[], size_t output_len, const uint8_t input[], size_t input_len)
void	randomize_with_ts_input (std::span< uint8_t > output)
void	randomize_with_ts_input (uint8_t output[], size_t output_len)
size_t	reseed (Entropy_Sources &, size_t, std::chrono::milliseconds) override
virtual void	reseed_from_rng (RandomNumberGenerator &rng, size_t poll_bits=BOTAN_RNG_RESEED_POLL_BITS)

Static Public Member Functions
static bool	available ()

Detailed Description

Directly invokes a CPU specific instruction to generate random numbers. On x86, the RDRAND instruction is used. on POWER, the DARN instruction is used.

Definition at line 19 of file processor_rng.h.

Constructor & Destructor Documentation

Processor_RNG()

Botan::Processor_RNG::Processor_RNG

(

)

Constructor will throw if CPU does not have RDRAND bit set

Definition at line 155 of file processor_rng.cpp.

   {
   if(!Processor_RNG::available())
      throw Invalid_State("Current CPU does not support RNG instruction");
   }

References available().

Member Function Documentation

accepts_input()

bool Botan::Processor_RNG::accepts_input ( ) const

inlineoverridevirtual

Returns false if it is known that this RNG object is not able to accept externally provided inputs (via add_entropy, randomize_with_input, etc). In this case, any such provided inputs are ignored.

If this function returns true, then inputs may or may not be accepted.

Implements Botan::RandomNumberGenerator.

Definition at line 32 of file processor_rng.h.

{ return false; }

add_entropy() [1/2]

void Botan::RandomNumberGenerator::add_entropy ( const uint8_t  input[], size_t  length  )

inlineinherited

Definition at line 78 of file rng.h.

         { this->add_entropy(std::span(input, length)); }

add_entropy() [2/2]

void Botan::RandomNumberGenerator::add_entropy ( std::span< const uint8_t >  input )

inlineinherited

Incorporate some additional data into the RNG state. For example adding nonces or timestamps from a peer's protocol message can help hedge against VM state rollback attacks. A few RNG types do not accept any externally provided input, in which case this function is a no-op.

Parameters

input

a byte array containing the entropy to be added

Exceptions

Exception

may throw if the RNG accepts input, but adding the entropy failed.

Definition at line 77 of file rng.h.

{ this->fill_bytes_with_input({}, input); }

Referenced by Botan::ChaCha_RNG::ChaCha_RNG(), Botan::Stateful_RNG::initialize_with(), Botan::Getentropy::poll(), Botan::Intel_Rdseed::poll(), and Botan::RandomNumberGenerator::reseed_from_rng().

add_entropy_T()

template<typename T >
requires std::is_standard_layout<T>

void Botan::RandomNumberGenerator::add_entropy_T ( const T &  t )

inlineinherited

Incorporate some additional data into the RNG state. Incorporate entropy into the RNG state then produce output. Some RNG types implement this using a single operation, default calls add_entropy + randomize in sequence.

Use this to further bind the outputs to your current process/protocol state. For instance if generating a new key for use in a session, include a session ID or other such value. See NIST SP 800-90 A, B, C series for more ideas.

Parameters

output	buffer to hold the random output
input	entropy buffer to incorporate

Exceptions

PRNG_Unseeded	if the RNG fails because it has not enough entropy
Exception	if the RNG fails
Exception	may throw if the RNG accepts input, but adding the entropy failed.

Definition at line 84 of file rng.h.

         {
         this->add_entropy(reinterpret_cast<const uint8_t*>(&t), sizeof(T));
         }
 
      /**
      * Incorporate entropy into the RNG state then produce output.
      * Some RNG types implement this using a single operation, default
      * calls add_entropy + randomize in sequence.
      *
      * Use this to further bind the outputs to your current
      * process/protocol state. For instance if generating a new key
      * for use in a session, include a session ID or other such
      * value. See NIST SP 800-90 A, B, C series for more ideas.
      *
      * @param output buffer to hold the random output
      * @param input entropy buffer to incorporate
      * @throws PRNG_Unseeded if the RNG fails because it has not enough entropy
      * @throws Exception if the RNG fails
      * @throws Exception may throw if the RNG accepts input, but adding the entropy failed.
      */
      void randomize_with_input(std::span<uint8_t> output, std::span<const uint8_t> input)
         { this->fill_bytes_with_input(output, input); }

References T.

Referenced by Botan::Win32_EntropySource::poll().

available()

bool Botan::Processor_RNG::available ( )

static

Return true if RNG instruction is available on the current processor

Definition at line 110 of file processor_rng.cpp.

   {
#if defined(BOTAN_TARGET_CPU_IS_X86_FAMILY)
   return CPUID::has_rdrand();
#elif defined(BOTAN_TARGET_CPU_IS_PPC_FAMILY)
   return CPUID::has_darn_rng();
#else
   return false;
#endif
   }

Referenced by botan_rng_init(), Botan::Entropy_Source::create(), and Processor_RNG().

clear()

virtual void Botan::Hardware_RNG::clear ( )

inlinefinaloverridevirtualinherited

Clear all internally held values of this RNG

Postcondition

is_seeded() == false if the RNG has an internal state that can be cleared.

Implements Botan::RandomNumberGenerator.

Definition at line 269 of file rng.h.

{ /* no way to clear state of hardware RNG */ }

is_seeded()

bool Botan::Processor_RNG::is_seeded ( ) const

inlineoverridevirtual

Check whether this RNG is seeded.

Returns

true if this RNG was already seeded, false otherwise.

Implements Botan::RandomNumberGenerator.

Definition at line 33 of file processor_rng.h.

{ return true; }

name()

std::string Botan::Processor_RNG::name ( ) const

overridevirtual

Returns

the name of this RNG type

Implements Botan::RandomNumberGenerator.

Definition at line 121 of file processor_rng.cpp.

   {
#if defined(BOTAN_TARGET_CPU_IS_X86_FAMILY)
   return "rdrand";
#elif defined(BOTAN_TARGET_CPU_IS_PPC_FAMILY)
   return "darn";
#else
   return "hwrng";
#endif
   }

next_byte()

uint8_t Botan::RandomNumberGenerator::next_byte ( )

inlineinherited

Return a random byte

Returns

random byte

Exceptions

PRNG_Unseeded	if the RNG fails because it has not enough entropy
Exception	if the RNG fails

Definition at line 219 of file rng.h.

         {
         uint8_t b;
         this->fill_bytes_with_input(std::span(&b, 1), {});
         return b;
         }

Referenced by Botan::random_prime().

next_nonzero_byte()

uint8_t Botan::RandomNumberGenerator::next_nonzero_byte ( )

inlineinherited

Returns

a random byte that is greater than zero

Exceptions

PRNG_Unseeded	if the RNG fails because it has not enough entropy
Exception	if the RNG fails

Definition at line 231 of file rng.h.

         {
         uint8_t b = this->next_byte();
         while(b == 0)
            b = this->next_byte();
         return b;
         }

Referenced by Botan::EME_PKCS1v15::pad().

random_vec() [1/3]

template<concepts::resizable_byte_buffer T = secure_vector<uint8_t>>
requires concepts::default_initializable<T>

T Botan::RandomNumberGenerator::random_vec ( size_t  bytes )

inlineinherited

Create some byte container type and fill it with some random bytes.

Template Parameters

T	the desired byte container type (e.g std::vector<uint8_t>)

Parameters

bytes

number of random bytes to initialize the container with

Returns

a container of type T with bytes random bytes

Exceptions

Exception

if RNG or memory allocation fails

Definition at line 206 of file rng.h.

         {
         T result;
         random_vec(result, bytes);
         return result;
         }

References T.

random_vec() [2/3]

void Botan::RandomNumberGenerator::random_vec ( std::span< uint8_t >  v )

inlineinherited

Fill a given byte container with bytes random bytes

Todo:

deprecate this overload (in favor of randomize())

Parameters

v	the container to be filled with bytes random bytes

Exceptions

Exception

if RNG fails

Definition at line 178 of file rng.h.

         { this->randomize(v); }

Referenced by Botan::TLS::Client_Key_Exchange::Client_Key_Exchange(), Botan::Curve25519_PrivateKey::Curve25519_PrivateKey(), Botan::PK_Decryptor::decrypt_or_random(), Botan::Dilithium_PrivateKey::Dilithium_PrivateKey(), Botan::Ed25519_PrivateKey::Ed25519_PrivateKey(), Botan::TLS::Session::encrypt(), Botan::KeyPair::encryption_consistency_check(), Botan::generate_bcrypt(), Botan::Kyber_PrivateKey::Kyber_PrivateKey(), Botan::TLS::make_hello_random(), Botan::OctetString::OctetString(), Botan::BigInt::randomize(), and Botan::RandomNumberGenerator::reseed_from_rng().

random_vec() [3/3]

template<concepts::resizable_byte_buffer T>

void Botan::RandomNumberGenerator::random_vec ( T &  v, size_t  bytes  )

inlineinherited

Resize a given byte container to bytes and fill it with random bytes

Template Parameters

T	the desired byte container type (e.g std::vector<uint8_t>)

Parameters

v	the container to be filled with bytes random bytes
bytes	number of random bytes to initialize the container with

Exceptions

Exception

if RNG or memory allocation fails

Definition at line 190 of file rng.h.

         {
         v.resize(bytes);
         random_vec(v);
         }

randomize() [1/2]

void Botan::RandomNumberGenerator::randomize ( std::span< uint8_t >  output )

inlineinherited

Randomize a byte array.

May block shortly if e.g. the RNG is not yet initialized or a retry because of insufficient entropy is needed.

Parameters

output

the byte array to hold the random output.

Exceptions

PRNG_Unseeded	if the RNG fails because it has not enough entropy
Exception	if the RNG fails

Definition at line 53 of file rng.h.

         { this->fill_bytes_with_input(output, {}); }

Referenced by Botan::TLS::Connection_Cipher_State::aead_nonce(), Botan::argon2_generate_pwhash(), botan_system_rng_get(), Botan::CryptoBox::encrypt(), Botan::generate_dsa_primes(), Botan::generate_passhash9(), Botan::Roughtime::Nonce::Nonce(), Botan::EME_PKCS1v15::pad(), Botan::random_gf2m(), Botan::McEliece_PublicKey::random_plaintext_element(), Botan::random_prime(), Botan::Sodium::randombytes_buf(), Botan::RandomNumberGenerator::randomize_with_ts_input(), Botan::KeyPair::signature_consistency_check(), Botan::RTSS_Share::split(), and Botan::UUID::UUID().

randomize() [2/2]

void Botan::RandomNumberGenerator::randomize ( uint8_t  output[], size_t  length  )

inlineinherited

Definition at line 55 of file rng.h.

         { this->randomize(std::span(output, length)); }

randomize_with_input()

void Botan::RandomNumberGenerator::randomize_with_input ( uint8_t  output[], size_t  output_len, const uint8_t  input[], size_t  input_len  )

inlineinherited

Definition at line 108 of file rng.h.

         { this->randomize_with_input(std::span(output, output_len), std::span(input, input_len)); }

Referenced by Botan::System_RNG::fill_bytes_with_input().

randomize_with_ts_input() [1/2]

void Botan::RandomNumberGenerator::randomize_with_ts_input ( std::span< uint8_t >  output )

inherited

This calls randomize_with_input using some timestamps as extra input.

For a stateful RNG using non-random but potentially unique data the extra input can help protect against problems with fork, VM state rollback, or other cases where somehow an RNG state is duplicated. If both of the duplicated RNG states later incorporate a timestamp (and the timestamps don't themselves repeat), their outputs will diverge.

Parameters

output

buffer to hold the random output

Exceptions

PRNG_Unseeded	if the RNG fails because it has not enough entropy
Exception	if the RNG fails
Exception	may throw if the RNG accepts input, but adding the entropy failed.

Definition at line 20 of file rng.cpp.

   {
   if(this->accepts_input())
      {
      constexpr auto s_hd_clk = sizeof(decltype(OS::get_high_resolution_clock()));
      constexpr auto s_sys_ts = sizeof(decltype(OS::get_system_timestamp_ns()));
      constexpr auto s_pid    = sizeof(decltype(OS::get_process_id()));
 
      std::array<uint8_t, s_hd_clk + s_sys_ts + s_pid> additional_input = {0};
      auto s_additional_input = std::span(additional_input.begin(), additional_input.end());
 
      store_le(OS::get_high_resolution_clock(), s_additional_input.data());
      s_additional_input = s_additional_input.subspan(s_hd_clk);
 
#if defined(BOTAN_HAS_SYSTEM_RNG)
      System_RNG system_rng;
      system_rng.randomize(s_additional_input);
#else
      store_le(OS::get_system_timestamp_ns(), s_additional_input.data());
      s_additional_input = s_additional_input.subspan(s_sys_ts);
 
      store_le(OS::get_process_id(), s_additional_input.data());
#endif
 
      this->fill_bytes_with_input(output, additional_input);
      }
   else
      {
      this->fill_bytes_with_input(output, {});
      }
   }

References Botan::RandomNumberGenerator::accepts_input(), Botan::RandomNumberGenerator::fill_bytes_with_input(), Botan::OS::get_high_resolution_clock(), Botan::OS::get_process_id(), Botan::OS::get_system_timestamp_ns(), Botan::RandomNumberGenerator::randomize(), Botan::store_le(), and Botan::system_rng().

randomize_with_ts_input() [2/2]

void Botan::RandomNumberGenerator::randomize_with_ts_input ( uint8_t  output[], size_t  output_len  )

inlineinherited

Definition at line 127 of file rng.h.

         { this->randomize_with_ts_input(std::span(output, output_len)); }

reseed()

size_t Botan::Processor_RNG::reseed ( Entropy_Sources &  srcs, size_t  poll_bits, std::chrono::milliseconds  poll_timeout  )

overridevirtual

Poll provided sources for up to poll_bits bits of entropy or until the timeout expires. Returns estimate of the number of bits collected.

Sets the seeded state to true if enough entropy was added.

Reimplemented from Botan::RandomNumberGenerator.

Definition at line 161 of file processor_rng.cpp.

   {
   /* no way to add entropy */
   return 0;
   }

reseed_from_rng()

void Botan::RandomNumberGenerator::reseed_from_rng ( RandomNumberGenerator &  rng, size_t  poll_bits = BOTAN_RNG_RESEED_POLL_BITS  )

virtualinherited

Reseed by reading specified bits from the RNG

Sets the seeded state to true if enough entropy was added.

Exceptions

Exception

if RNG accepts input but reseeding failed.

Reimplemented in Botan::Stateful_RNG.

Definition at line 66 of file rng.cpp.

   {
   if(this->accepts_input())
      {
      this->add_entropy(rng.random_vec(poll_bits / 8));
      }
   }

References Botan::RandomNumberGenerator::accepts_input(), Botan::RandomNumberGenerator::add_entropy(), and Botan::RandomNumberGenerator::random_vec().

Referenced by Botan::Stateful_RNG::reseed_from_rng().

---

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

• src/lib/rng/processor_rng/processor_rng.h
• src/lib/rng/processor_rng/processor_rng.cpp