Botan::RandomNumberGenerator Class Reference

#include <rng.h>

Inheritance diagram for Botan::RandomNumberGenerator:

Public Member Functions
virtual bool	accepts_input () const =0
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>::value && std::is_trivial<T>::value
void	add_entropy_T (const T &t)
virtual void	clear ()=0
virtual bool	is_seeded () const =0
virtual std::string	name () const =0
uint8_t	next_byte ()
uint8_t	next_nonzero_byte ()
RandomNumberGenerator &	operator= (const RandomNumberGenerator &rng)=delete
template<size_t bytes>
std::array< uint8_t, bytes >	random_array ()
template<concepts::resizable_byte_buffer T = secure_vector<uint8_t>> requires std::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 (std::span< uint8_t > output, std::span< const uint8_t > input)
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)
	RandomNumberGenerator ()=default
	RandomNumberGenerator (const RandomNumberGenerator &rng)=delete
virtual size_t	reseed (Entropy_Sources &srcs, size_t poll_bits=RandomNumberGenerator::DefaultPollBits, std::chrono::milliseconds poll_timeout=RandomNumberGenerator::DefaultPollTimeout)
virtual void	reseed_from_rng (RandomNumberGenerator &rng, size_t poll_bits=RandomNumberGenerator::DefaultPollBits)
virtual	~RandomNumberGenerator ()=default

Static Public Attributes
static constexpr size_t	DefaultPollBits = 256
static constexpr auto	DefaultPollTimeout = std::chrono::milliseconds(50)
static constexpr size_t	DefaultReseedInterval = 1024

Protected Member Functions
virtual void	fill_bytes_with_input (std::span< uint8_t > output, std::span< const uint8_t > input)=0

Detailed Description

An interface to a cryptographic random number generator

Definition at line 30 of file rng.h.

Constructor & Destructor Documentation

~RandomNumberGenerator()

virtual Botan::RandomNumberGenerator::~RandomNumberGenerator ( )

virtualdefault

RandomNumberGenerator() [1/2]

Botan::RandomNumberGenerator::RandomNumberGenerator ( )

default

Referenced by Botan::AutoSeeded_RNG::AutoSeeded_RNG(), Botan::AutoSeeded_RNG::AutoSeeded_RNG(), Botan::Stateful_RNG::clear_state(), is_seeded(), operator=(), RandomNumberGenerator(), reseed_from_rng(), Botan::Stateful_RNG::reseed_from_rng(), Botan::Stateful_RNG::Stateful_RNG(), and Botan::Stateful_RNG::Stateful_RNG().

RandomNumberGenerator() [2/2]

Botan::RandomNumberGenerator::RandomNumberGenerator ( const RandomNumberGenerator & rng )

delete

References RandomNumberGenerator().

Member Function Documentation

accepts_input()

virtual bool Botan::RandomNumberGenerator::accepts_input ( ) const

pure virtual

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.

Implemented in Botan::AutoSeeded_RNG, Botan::ESDM_RNG, Botan::Jitter_RNG, Botan::Null_RNG, Botan::PKCS11::PKCS11_RNG, Botan::Processor_RNG, Botan::Stateful_RNG, Botan::System_RNG, Botan::TPM2::RandomNumberGenerator, and Botan::TPM_RNG.

Referenced by Botan::System_RNG::accepts_input(), randomize_with_ts_input(), reseed(), and reseed_from_rng().

add_entropy() [1/2]

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

inline

Definition at line 93 of file rng.h.

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

References add_entropy().

Referenced by add_entropy().

add_entropy() [2/2]

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

inline

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 91 of file rng.h.

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

References fill_bytes_with_input().

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

add_entropy_T()

template<typename T>
requires std::is_standard_layout<T>::value && std::is_trivial<T>::value

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

inline

Incorporate some additional data into the RNG state.

Definition at line 100 of file rng.h.

                                     {
         this->add_entropy(reinterpret_cast<const uint8_t*>(&t), sizeof(T));
      }

References add_entropy().

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

clear()

virtual void Botan::RandomNumberGenerator::clear ( )

pure virtual

Clear all internally held values of this RNG

Postcondition

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

Implemented in Botan::AutoSeeded_RNG, Botan::ESDM_RNG, Botan::Hardware_RNG, Botan::Jitter_RNG, Botan::Null_RNG, Botan::Stateful_RNG, and Botan::System_RNG.

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

fill_bytes_with_input()

virtual void Botan::RandomNumberGenerator::fill_bytes_with_input ( std::span< uint8_t > output, std::span< const uint8_t > input )

protectedpure virtual

Generic interface to provide entropy to a concrete implementation and to fill a given buffer with random output. Both output and input may be empty and should be ignored in that case. If both buffers are non-empty implementations should typically first apply the input data and then generate random data into output.

This method must be implemented by all RandomNumberGenerator sub-classes.

Parameters

output	Byte buffer to write random bytes into. Implementations should not read from this buffer.
input	Byte buffer that may contain bytes to be incorporated in the RNG's internal state. Implementations may choose to ignore the bytes in this buffer.

Implemented in Botan::ESDM_RNG, and Botan::System_RNG.

Referenced by add_entropy(), next_byte(), randomize(), randomize_with_input(), and randomize_with_ts_input().

is_seeded()

virtual bool Botan::RandomNumberGenerator::is_seeded ( ) const

pure virtual

Check whether this RNG is seeded.

Returns

true if this RNG was already seeded, false otherwise.

Implemented in Botan::AutoSeeded_RNG, Botan::ESDM_RNG, Botan::Jitter_RNG, Botan::Null_RNG, Botan::PKCS11::PKCS11_RNG, Botan::Processor_RNG, Botan::Stateful_RNG, Botan::System_RNG, Botan::TPM2::RandomNumberGenerator, and Botan::TPM_RNG.

References DefaultPollBits, DefaultPollTimeout, RandomNumberGenerator(), reseed(), and reseed_from_rng().

Referenced by Botan::EC_Point_Var_Point_Precompute::EC_Point_Var_Point_Precompute(), Botan::is_prime(), Botan::System_RNG::is_seeded(), Botan::EC_Point_Base_Point_Precompute::mul(), and Botan::EC_Point::randomize_repr().

name()

virtual std::string Botan::RandomNumberGenerator::name ( ) const

pure virtual

Returns

the name of this RNG type

Implemented in Botan::AutoSeeded_RNG, Botan::ChaCha_RNG, Botan::ESDM_RNG, Botan::HMAC_DRBG, Botan::Jitter_RNG, Botan::Null_RNG, Botan::PKCS11::PKCS11_RNG, Botan::Processor_RNG, Botan::System_RNG, Botan::TPM2::RandomNumberGenerator, and Botan::TPM_RNG.

Referenced by Botan::System_RNG::name(), and Botan::Stateful_RNG::reseed_check().

next_byte()

uint8_t Botan::RandomNumberGenerator::next_byte ( )

inline

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 244 of file rng.h.

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

References fill_bytes_with_input().

Referenced by next_nonzero_byte(), and Botan::random_prime().

next_nonzero_byte()

uint8_t Botan::RandomNumberGenerator::next_nonzero_byte ( )

inline

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 255 of file rng.h.

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

References next_byte().

operator=()

RandomNumberGenerator & Botan::RandomNumberGenerator::operator= ( const RandomNumberGenerator & rng )

delete

References RandomNumberGenerator().

random_array()

template<size_t bytes>

std::array< uint8_t, bytes > Botan::RandomNumberGenerator::random_array ( )

inline

Create a std::array of bytes random bytes

Definition at line 232 of file rng.h.

                                              {
         std::array<uint8_t, bytes> result;
         random_vec(result);
         return result;
      }

References random_vec().

random_vec() [1/3]

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

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

inline

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 222 of file rng.h.

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

References random_vec().

random_vec() [2/3]

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

inline

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 196 of file rng.h.

{ this->randomize(v); }

References randomize().

Referenced by Botan::Classic_McEliece_PrivateKey::Classic_McEliece_PrivateKey(), Botan::TLS::Client_Key_Exchange::Client_Key_Exchange(), Botan::TLS::Client_Key_Exchange::Client_Key_Exchange(), Botan::PK_Decryptor::decrypt_or_random(), Botan::Dilithium_PrivateKey::Dilithium_PrivateKey(), Botan::Ed25519_PrivateKey::Ed25519_PrivateKey(), Botan::Kyber_KEM_Encryptor::encapsulate(), Botan::ML_KEM_Encryptor::encapsulate(), Botan::TLS::Session::encrypt(), Botan::KeyPair::encryption_consistency_check(), Botan::FrodoKEM_PrivateKey::FrodoKEM_PrivateKey(), Botan::generate_bcrypt(), Botan::HSS_LMS_PrivateKeyInternal::HSS_LMS_PrivateKeyInternal(), Botan::Kyber_PrivateKey::Kyber_PrivateKey(), Botan::TLS::make_hello_random(), Botan::OctetString::OctetString(), random_array(), random_vec(), random_vec(), Botan::BigInt::randomize(), reseed_from_rng(), Botan::SphincsPlus_PrivateKey::SphincsPlus_PrivateKey(), and Botan::X25519_PrivateKey::X25519_PrivateKey().

random_vec() [3/3]

template<concepts::resizable_byte_buffer T>

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

inline

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 207 of file rng.h.

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

References random_vec().

randomize() [1/2]

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

inline

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 68 of file rng.h.

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

References fill_bytes_with_input().

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::random_gf2m(), Botan::McEliece_PublicKey::random_plaintext_element(), Botan::random_prime(), random_vec(), Botan::Sodium::randombytes_buf(), 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 )

inline

Definition at line 70 of file rng.h.

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

References randomize().

Referenced by randomize().

randomize_with_input() [1/2]

void Botan::RandomNumberGenerator::randomize_with_input ( std::span< uint8_t > output, std::span< const uint8_t > input )

inline

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 120 of file rng.h.

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

References fill_bytes_with_input().

Referenced by Botan::System_RNG::fill_bytes_with_input(), and randomize_with_input().

randomize_with_input() [2/2]

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

inline

Definition at line 124 of file rng.h.

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

References randomize_with_input().

randomize_with_ts_input() [1/2]

void Botan::RandomNumberGenerator::randomize_with_ts_input

(

std::span< uint8_t >

output

)

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 27 of file rng.cpp.

                                                                           {
   if(this->accepts_input()) {
      std::array<uint8_t, 32> additional_input = {0};
 
#if defined(BOTAN_HAS_OS_UTILS)
      store_le(std::span{additional_input}.subspan<0, 8>(), OS::get_high_resolution_clock());
      store_le(std::span{additional_input}.subspan<8, 4>(), OS::get_process_id());
      constexpr size_t offset = 12;
#else
      constexpr size_t offset = 0;
#endif
 
#if defined(BOTAN_HAS_SYSTEM_RNG)
      system_rng().randomize(std::span{additional_input}.subspan<offset>());
#else
      BOTAN_UNUSED(offset);
#endif
 
      this->fill_bytes_with_input(output, additional_input);
   } else {
      this->fill_bytes_with_input(output, {});
   }
}

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

Referenced by randomize_with_ts_input().

randomize_with_ts_input() [2/2]

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

inline

Definition at line 144 of file rng.h.

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

References randomize_with_ts_input().

reseed()

size_t Botan::RandomNumberGenerator::reseed ( Entropy_Sources & srcs, size_t poll_bits = RandomNumberGenerator::DefaultPollBits, std::chrono::milliseconds poll_timeout = RandomNumberGenerator::DefaultPollTimeout )

virtual

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 in Botan::AutoSeeded_RNG, Botan::PKCS11::PKCS11_RNG, Botan::Processor_RNG, and Botan::Stateful_RNG.

Definition at line 51 of file rng.cpp.

                                                                                                                {
   if(this->accepts_input()) {
#if defined(BOTAN_HAS_ENTROPY_SOURCE)
      return srcs.poll(*this, poll_bits, poll_timeout);
#else
      BOTAN_UNUSED(srcs, poll_bits, poll_timeout);
#endif
   }
 
   return 0;
}

References accepts_input(), BOTAN_UNUSED, and Botan::Entropy_Sources::poll().

Referenced by is_seeded(), and Botan::Stateful_RNG::reseed().

reseed_from_rng()

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

virtual

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 63 of file rng.cpp.

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

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

Referenced by is_seeded(), and Botan::Stateful_RNG::reseed_from_rng().

Member Data Documentation

DefaultPollBits

size_t Botan::RandomNumberGenerator::DefaultPollBits = 256

staticconstexpr

Number of entropy bits polled for reseeding userspace RNGs like HMAC_DRBG

Definition at line 41 of file rng.h.

Referenced by is_seeded().

DefaultPollTimeout

auto Botan::RandomNumberGenerator::DefaultPollTimeout = std::chrono::milliseconds(50)

staticconstexpr

Default poll timeout

Definition at line 46 of file rng.h.

Referenced by is_seeded().

DefaultReseedInterval

size_t Botan::RandomNumberGenerator::DefaultReseedInterval = 1024

staticconstexpr

Userspace RNGs like HMAC_DRBG will reseed after a specified number of outputs are generated. Set to zero to disable automatic reseeding.

Definition at line 36 of file rng.h.

---

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

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