Botan::System_RNG Class Reference

#include <system_rng.h>

Inheritance diagram for Botan::System_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>::value && std::is_trivial<T>::value
void	add_entropy_T (const T &t)
void	clear () override
bool	is_seeded () const override
std::string	name () const override
uint8_t	next_byte ()
uint8_t	next_nonzero_byte ()
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)
virtual size_t	reseed (Entropy_Sources &srcs, size_t poll_bits=BOTAN_RNG_RESEED_POLL_BITS, std::chrono::milliseconds poll_timeout=BOTAN_RNG_RESEED_DEFAULT_TIMEOUT)
virtual void	reseed_from_rng (RandomNumberGenerator &rng, size_t poll_bits=BOTAN_RNG_RESEED_POLL_BITS)

Protected Member Functions
void	fill_bytes_with_input (std::span< uint8_t > out, std::span< const uint8_t > in) override

Detailed Description

Definition at line 25 of file system_rng.h.

Member Function Documentation

accepts_input()

bool Botan::System_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 31 of file system_rng.h.

{ return system_rng().accepts_input(); }

References Botan::RandomNumberGenerator::accepts_input(), and Botan::system_rng().

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)); }

References Botan::RandomNumberGenerator::add_entropy().

Referenced by Botan::RandomNumberGenerator::add_entropy().

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 76 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>::value && std::is_trivial<T>::value

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

inlineinherited

Incorporate some additional data into the RNG state.

Definition at line 85 of file rng.h.

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

References T.

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

clear()

void Botan::System_RNG::clear ( )

inlineoverridevirtual

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 33 of file system_rng.h.

{ system_rng().clear(); }

References Botan::RandomNumberGenerator::clear(), and Botan::system_rng().

fill_bytes_with_input()

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

inlineoverrideprotectedvirtual

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.

Implements Botan::RandomNumberGenerator.

Definition at line 36 of file system_rng.h.

                                                                                           {
         system_rng().randomize_with_input(out, in);
      }

References Botan::RandomNumberGenerator::randomize_with_input(), and Botan::system_rng().

is_seeded()

bool Botan::System_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 29 of file system_rng.h.

{ return system_rng().is_seeded(); }

References Botan::RandomNumberGenerator::is_seeded(), and Botan::system_rng().

name()

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

inlineoverridevirtual

Returns

the name of this RNG type

Implements Botan::RandomNumberGenerator.

Definition at line 27 of file system_rng.h.

{ return system_rng().name(); }

References Botan::RandomNumberGenerator::name(), and Botan::system_rng().

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 228 of file rng.h.

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

References Botan::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 239 of file rng.h.

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

References Botan::b.

random_array()

template<size_t bytes>

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

inlineinherited

Create a std::array of bytes random bytes

Definition at line 216 of file rng.h.

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

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 )

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 180 of file rng.h.

{ this->randomize(v); }

Referenced by 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(), Botan::BigInt::randomize(), Botan::RandomNumberGenerator::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 )

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 191 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::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)); }

References Botan::RandomNumberGenerator::randomize().

Referenced by Botan::RandomNumberGenerator::randomize().

randomize_with_input() [1/2]

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

inlineinherited

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 105 of file rng.h.

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

Referenced by fill_bytes_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 )

inlineinherited

Definition at line 109 of file rng.h.

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

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 21 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 129 of file rng.h.

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

reseed()

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

virtualinherited

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 49 of file rng.cpp.

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

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

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

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 57 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 file:

• src/lib/rng/system_rng/system_rng.h