Botan::Stateful_RNG Class Reference

#include <stateful_rng.h>

Inheritance diagram for Botan::Stateful_RNG:

Public Member Functions
bool	accepts_input () const final
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 () final
void	force_reseed ()
void	initialize_with (const uint8_t input[], size_t length)
void	initialize_with (std::span< const uint8_t > input)
bool	is_seeded () const final
virtual size_t	max_number_of_bytes_per_request () const =0
virtual std::string	name () const =0
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)
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) override
void	reseed_from_rng (RandomNumberGenerator &rng, size_t poll_bits=BOTAN_RNG_RESEED_POLL_BITS) final
size_t	reseed_interval () const
virtual size_t	security_level () const =0
	Stateful_RNG ()
	Stateful_RNG (Entropy_Sources &entropy_sources, size_t reseed_interval)
	Stateful_RNG (RandomNumberGenerator &rng, Entropy_Sources &entropy_sources, size_t reseed_interval)
	Stateful_RNG (RandomNumberGenerator &rng, size_t reseed_interval)

Protected Member Functions
virtual void	clear_state ()=0
virtual void	generate_output (std::span< uint8_t > output, std::span< const uint8_t > input)=0
void	reseed_check ()
virtual void	update (std::span< const uint8_t > input)=0

Detailed Description

Inherited by RNGs which maintain in-process state, like HMAC_DRBG. On Unix these RNGs are vulnerable to problems with fork, where the RNG state is duplicated, and the parent and child process RNGs will produce identical output until one of them reseeds. Stateful_RNG reseeds itself whenever a fork is detected, or after a set number of bytes have been output.

Not implemented by RNGs which access an external RNG, such as the system PRNG or a hardware RNG.

Definition at line 26 of file stateful_rng.h.

Constructor & Destructor Documentation

Stateful_RNG() [1/4]

Botan::Stateful_RNG::Stateful_RNG ( RandomNumberGenerator & rng, Entropy_Sources & entropy_sources, size_t reseed_interval )

inline

Parameters

rng	is a reference to some RNG which will be used to perform the periodic reseeding
entropy_sources	will be polled to perform reseeding periodically
reseed_interval	specifies a limit of how many times the RNG will be called before automatic reseeding is performed

Definition at line 35 of file stateful_rng.h.

                                                                                                         :
            m_underlying_rng(&rng), m_entropy_sources(&entropy_sources), m_reseed_interval(reseed_interval) {}

Stateful_RNG() [2/4]

Botan::Stateful_RNG::Stateful_RNG ( RandomNumberGenerator & rng, size_t reseed_interval )

inline

Parameters

rng	is a reference to some RNG which will be used to perform the periodic reseeding
reseed_interval	specifies a limit of how many times the RNG will be called before automatic reseeding is performed

Definition at line 44 of file stateful_rng.h.

                                                                       :
            m_underlying_rng(&rng), m_reseed_interval(reseed_interval) {}

Stateful_RNG() [3/4]

Botan::Stateful_RNG::Stateful_RNG ( Entropy_Sources & entropy_sources, size_t reseed_interval )

inline

Parameters

entropy_sources	will be polled to perform reseeding periodically
reseed_interval	specifies a limit of how many times the RNG will be called before automatic reseeding is performed

Definition at line 52 of file stateful_rng.h.

                                                                             :
            m_entropy_sources(&entropy_sources), m_reseed_interval(reseed_interval) {}

Stateful_RNG() [4/4]

Botan::Stateful_RNG::Stateful_RNG ( )

inline

In this case, automatic reseeding is impossible

Definition at line 58 of file stateful_rng.h.

: m_reseed_interval(0) {}

Member Function Documentation

accepts_input()

bool Botan::Stateful_RNG::accepts_input ( ) const

inlinefinalvirtual

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 71 of file stateful_rng.h.

{ return true; }

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(), 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::Stateful_RNG::clear ( )

finalvirtual

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 14 of file stateful_rng.cpp.

                         {
   lock_guard_type<recursive_mutex_type> lock(m_mutex);
   m_reseed_counter = 0;
   m_last_pid = 0;
   clear_state();
}

References clear_state(), and Botan::lock().

Referenced by Botan::ChaCha_RNG::ChaCha_RNG(), Botan::ChaCha_RNG::ChaCha_RNG(), Botan::ChaCha_RNG::ChaCha_RNG(), Botan::ChaCha_RNG::ChaCha_RNG(), Botan::ChaCha_RNG::ChaCha_RNG(), Botan::HMAC_DRBG::HMAC_DRBG(), Botan::HMAC_DRBG::HMAC_DRBG(), Botan::HMAC_DRBG::HMAC_DRBG(), Botan::HMAC_DRBG::HMAC_DRBG(), Botan::HMAC_DRBG::HMAC_DRBG(), and initialize_with().

clear_state()

virtual void Botan::Stateful_RNG::clear_state ( )

protectedpure virtual

Referenced by clear().

force_reseed()

void Botan::Stateful_RNG::force_reseed

(

)

Mark state as requiring a reseed on next use

Definition at line 21 of file stateful_rng.cpp.

                                {
   lock_guard_type<recursive_mutex_type> lock(m_mutex);
   m_reseed_counter = 0;
}

References Botan::lock().

generate_output()

virtual void Botan::Stateful_RNG::generate_output ( std::span< uint8_t > output, std::span< const uint8_t > input )

protectedpure virtual

initialize_with() [1/2]

void Botan::Stateful_RNG::initialize_with ( const uint8_t input[], size_t length )

inline

Definition at line 67 of file stateful_rng.h.

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

References initialize_with().

Referenced by initialize_with().

initialize_with() [2/2]

void Botan::Stateful_RNG::initialize_with

(

std::span< const uint8_t >

input

)

Consume this input and mark the RNG as initialized regardless of the length of the input or the current seeded state of the RNG.

Definition at line 31 of file stateful_rng.cpp.

                                                               {
   lock_guard_type<recursive_mutex_type> lock(m_mutex);
 
   clear();
   add_entropy(input);
}

References Botan::RandomNumberGenerator::add_entropy(), clear(), and Botan::lock().

is_seeded()

bool Botan::Stateful_RNG::is_seeded ( ) const

finalvirtual

Check whether this RNG is seeded.

Returns

true if this RNG was already seeded, false otherwise.

Implements Botan::RandomNumberGenerator.

Definition at line 26 of file stateful_rng.cpp.

                                   {
   lock_guard_type<recursive_mutex_type> lock(m_mutex);
   return m_reseed_counter > 0;
}

References Botan::lock().

Referenced by reseed_check().

max_number_of_bytes_per_request()

virtual size_t Botan::Stateful_RNG::max_number_of_bytes_per_request ( ) const

pure virtual

Some DRBGs have a notion of the maximum number of bytes per request. Longer requests (to randomize) will be treated as multiple requests, and may initiate reseeding multiple times, depending on the values of max_number_of_bytes_per_request and reseed_interval(). This function returns zero if the RNG in question does not have such a notion.

Returns

max number of bytes per request (or zero)

Implemented in Botan::ChaCha_RNG, and Botan::HMAC_DRBG.

name()

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

pure virtualinherited

Returns

the name of this RNG type

Implemented in Botan::AutoSeeded_RNG, Botan::ChaCha_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 reseed_check().

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 Botan::System_RNG::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::Stateful_RNG::reseed ( Entropy_Sources & srcs, size_t poll_bits = BOTAN_RNG_RESEED_POLL_BITS, std::chrono::milliseconds poll_timeout = BOTAN_RNG_RESEED_DEFAULT_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.

Reimplemented from Botan::RandomNumberGenerator.

Definition at line 77 of file stateful_rng.cpp.

                                                                                                       {
   lock_guard_type<recursive_mutex_type> lock(m_mutex);
 
   const size_t bits_collected = RandomNumberGenerator::reseed(srcs, poll_bits, poll_timeout);
 
   if(bits_collected >= security_level()) {
      reset_reseed_counter();
   }
 
   return bits_collected;
}

References Botan::lock(), Botan::RandomNumberGenerator::reseed(), and security_level().

Referenced by reseed_check().

reseed_check()

void Botan::Stateful_RNG::reseed_check ( )

protected

Definition at line 104 of file stateful_rng.cpp.

                                {
   // Lock is held whenever this function is called
 
   const uint32_t cur_pid = OS::get_process_id();
 
   const bool fork_detected = (m_last_pid > 0) && (cur_pid != m_last_pid);
 
   if(is_seeded() == false || fork_detected || (m_reseed_interval > 0 && m_reseed_counter >= m_reseed_interval)) {
      m_reseed_counter = 0;
      m_last_pid = cur_pid;
 
      if(m_underlying_rng) {
         reseed_from_rng(*m_underlying_rng, security_level());
      }
 
      if(m_entropy_sources) {
         reseed(*m_entropy_sources, security_level());
      }
 
      if(!is_seeded()) {
         if(fork_detected) {
            throw Invalid_State("Detected use of fork but cannot reseed DRBG");
         } else {
            throw PRNG_Unseeded(name());
         }
      }
   } else {
      BOTAN_ASSERT(m_reseed_counter != 0, "RNG is seeded");
      m_reseed_counter += 1;
   }
}

References BOTAN_ASSERT, Botan::OS::get_process_id(), is_seeded(), Botan::RandomNumberGenerator::name(), reseed(), reseed_from_rng(), and security_level().

reseed_from_rng()

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

finalvirtual

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 from Botan::RandomNumberGenerator.

Definition at line 89 of file stateful_rng.cpp.

                                                                               {
   lock_guard_type<recursive_mutex_type> lock(m_mutex);
 
   RandomNumberGenerator::reseed_from_rng(rng, poll_bits);
 
   if(poll_bits >= security_level()) {
      reset_reseed_counter();
   }
}

References Botan::lock(), Botan::RandomNumberGenerator::reseed_from_rng(), and security_level().

Referenced by reseed_check().

reseed_interval()

size_t Botan::Stateful_RNG::reseed_interval ( ) const

inline

Definition at line 106 of file stateful_rng.h.

{ return m_reseed_interval; }

Referenced by Botan::HMAC_DRBG::HMAC_DRBG(), Botan::HMAC_DRBG::HMAC_DRBG(), and Botan::HMAC_DRBG::HMAC_DRBG().

security_level()

virtual size_t Botan::Stateful_RNG::security_level ( ) const

pure virtual

Returns

intended security level of this DRBG

Implemented in Botan::ChaCha_RNG, and Botan::HMAC_DRBG.

Referenced by reseed(), reseed_check(), and reseed_from_rng().

update()

virtual void Botan::Stateful_RNG::update ( std::span< const uint8_t > input )

protectedpure virtual

---

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

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