Botan::Stateful_RNG Class Reference

#include <stateful_rng.h>

Inheritance diagram for Botan::Stateful_RNG:

Public Member Functions
bool	accepts_input () const override final
virtual void	add_entropy (const uint8_t input[], size_t length)=0
template<typename T >
void	add_entropy_T (const T &t)
void	clear () override
void	force_reseed ()
void	initialize_with (const uint8_t input[], size_t length)
bool	is_seeded () const override 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 ()
secure_vector< uint8_t >	random_vec (size_t bytes)
virtual void	randomize (uint8_t output[], size_t length)=0
virtual void	randomize_with_input (uint8_t output[], size_t output_len, const uint8_t input[], size_t input_len)
void	randomize_with_ts_input (uint8_t output[], size_t output_len) override final
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) override final
size_t	reseed_interval () const
virtual size_t	security_level () const =0
	Stateful_RNG (RandomNumberGenerator &rng, Entropy_Sources &entropy_sources, size_t reseed_interval)
	Stateful_RNG (RandomNumberGenerator &rng, size_t reseed_interval)
	Stateful_RNG (Entropy_Sources &entropy_sources, size_t reseed_interval)
	Stateful_RNG ()

Static Public Member Functions
static RandomNumberGenerator *	make_rng ()

Protected Member Functions
void	reseed_check ()
void	reset_reseed_counter ()

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 25 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 49 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 59 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 67 of file stateful_rng.h.

: m_reseed_interval(0) {}

Member Function Documentation

accepts_input()

bool Botan::Stateful_RNG::accepts_input ( ) const

inlinefinaloverridevirtual

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 78 of file stateful_rng.h.

{ return true; }

add_entropy()

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

pure virtualinherited

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 containg the entropy to be added
length	the length of the byte array in

Implemented in Botan::Null_RNG, Botan::HMAC_DRBG, Botan::ChaCha_RNG, Botan::TPM_RNG, Botan::RDRAND_RNG, Botan::AutoSeeded_RNG, and Botan::System_RNG.

Referenced by Botan::System_RNG::add_entropy(), botan_rng_add_entropy(), initialize_with(), Botan::Getentropy::poll(), Botan::Intel_Rdrand::poll(), Botan::Device_EntropySource::poll(), Botan::RandomNumberGenerator::randomize_with_input(), and Botan::RandomNumberGenerator::reseed_from_rng().

add_entropy_T()

template<typename T >

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

inlineinherited

Incorporate some additional data into the RNG state.

Definition at line 68 of file rng.h.

References T.

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

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

clear()

void Botan::Stateful_RNG::clear ( )

overridevirtual

Clear all internally held values of this RNG

Postcondition

is_seeded() == false

Implements Botan::RandomNumberGenerator.

Definition at line 13 of file stateful_rng.cpp.

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

   {
   m_reseed_counter = 0;
   m_last_pid = 0;
   }

force_reseed()

void Botan::Stateful_RNG::force_reseed

(

)

Mark state as requiring a reseed on next use

Definition at line 19 of file stateful_rng.cpp.

   {
   m_reseed_counter = 0;
   }

initialize_with()

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

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 29 of file stateful_rng.cpp.

References Botan::RandomNumberGenerator::add_entropy(), reset_reseed_counter(), and security_level().

   {
   add_entropy(input, len);

   if(8*len >= security_level())
      {
      reset_reseed_counter();
      }
   }

is_seeded()

bool Botan::Stateful_RNG::is_seeded ( ) const

finaloverridevirtual

Check whether this RNG is seeded.

Returns

true if this RNG was already seeded, false otherwise.

Implements Botan::RandomNumberGenerator.

Definition at line 24 of file stateful_rng.cpp.

Referenced by reseed_check().

   {
   return m_reseed_counter > 0;
   }

make_rng()

RandomNumberGenerator * Botan::RandomNumberGenerator::make_rng ( )

staticinherited

Create a seeded and active RNG object for general application use Added in 1.8.0 Use AutoSeeded_RNG instead

Definition at line 69 of file rng.cpp.

   {
#if defined(BOTAN_HAS_AUTO_SEEDING_RNG)
   return new AutoSeeded_RNG;
#else
   throw Exception("make_rng failed, no AutoSeeded_RNG in this build");
#endif
   }

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::HMAC_DRBG, and Botan::ChaCha_RNG.

name()

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

pure virtualinherited

Returns

the name of this RNG type

Implemented in Botan::Null_RNG, Botan::HMAC_DRBG, Botan::ChaCha_RNG, Botan::TPM_RNG, Botan::RDRAND_RNG, Botan::AutoSeeded_RNG, Botan::PKCS11::PKCS11_RNG, and Botan::System_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

Definition at line 152 of file rng.h.

Referenced by Botan::random_prime().

         {
         uint8_t b;
         this->randomize(&b, 1);
         return b;
         }

next_nonzero_byte()

uint8_t Botan::RandomNumberGenerator::next_nonzero_byte ( )

inlineinherited

Returns

a random byte that is greater than zero

Definition at line 162 of file rng.h.

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

random_vec()

secure_vector<uint8_t> Botan::RandomNumberGenerator::random_vec ( size_t  bytes )

inlineinherited

Return a random vector

Parameters

bytes

number of bytes in the result

Returns

randomized vector of length bytes

Definition at line 141 of file rng.h.

Referenced by Botan::CECPQ1_accept(), Botan::CECPQ1_offer(), Botan::TLS::Client_Key_Exchange::Client_Key_Exchange(), Botan::Curve25519_PrivateKey::Curve25519_PrivateKey(), Botan::PK_Decryptor::decrypt_or_random(), Botan::Ed25519_PrivateKey::Ed25519_PrivateKey(), Botan::TLS::Session::encrypt(), Botan::KeyPair::encryption_consistency_check(), Botan::generate_bcrypt(), Botan::mceies_encrypt(), Botan::OctetString::OctetString(), Botan::BigInt::randomize(), and Botan::TLS::Session_Manager_In_Memory::remove_all().

         {
         secure_vector<uint8_t> output(bytes);
         this->randomize(output.data(), output.size());
         return output;
         }

randomize()

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

pure virtualinherited

Randomize a byte array.

Parameters

output	the byte array to hold the random output.
length	the length of the byte array output in bytes.

Implemented in Botan::Null_RNG, Botan::HMAC_DRBG, Botan::ChaCha_RNG, Botan::TPM_RNG, Botan::RDRAND_RNG, Botan::System_RNG, and Botan::AutoSeeded_RNG.

Referenced by Botan::TLS::Connection_Cipher_State::aead_nonce(), botan_rng_get(), Botan::CryptoBox::encrypt(), Botan::generate_dsa_primes(), Botan::generate_passhash9(), Botan::TLS::make_hello_random(), Botan::newhope_keygen(), Botan::random_gf2m(), Botan::McEliece_PublicKey::random_plaintext_element(), Botan::System_RNG::randomize(), Botan::RandomNumberGenerator::randomize_with_input(), Botan::RandomNumberGenerator::randomize_with_ts_input(), Botan::RandomNumberGenerator::reseed_from_rng(), Botan::KeyPair::signature_consistency_check(), Botan::RTSS_Share::split(), and Botan::UUID::UUID().

randomize_with_input()

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

virtualinherited

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
output_len	size of the output buffer in bytes
input	entropy buffer to incorporate
input_len	size of the input buffer in bytes

Reimplemented in Botan::HMAC_DRBG, Botan::ChaCha_RNG, and Botan::AutoSeeded_RNG.

Definition at line 38 of file rng.cpp.

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

Referenced by randomize_with_ts_input(), and Botan::RandomNumberGenerator::randomize_with_ts_input().

   {
   this->add_entropy(input, input_len);
   this->randomize(output, output_len);
   }

randomize_with_ts_input()

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

finaloverridevirtual

Overrides default implementation and also includes the current process ID and the reseed counter.

Reimplemented from Botan::RandomNumberGenerator.

Definition at line 39 of file stateful_rng.cpp.

References Botan::OS::get_high_resolution_clock(), Botan::OS::get_system_timestamp_ns(), Botan::RandomNumberGenerator::randomize_with_input(), and Botan::store_le().

   {
   uint8_t additional_input[24] = { 0 };
   store_le(OS::get_system_timestamp_ns(), additional_input);
   store_le(OS::get_high_resolution_clock(), additional_input + 8);
   store_le(m_last_pid, additional_input + 16);
   store_le(static_cast<uint32_t>(m_reseed_counter), additional_input + 20);

   randomize_with_input(output, output_len, additional_input, sizeof(additional_input));
   }

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 50 of file stateful_rng.cpp.

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

Referenced by reseed_check().

   {
   size_t bits_collected = RandomNumberGenerator::reseed(srcs, poll_bits, poll_timeout);

   if(bits_collected >= security_level())
      {
      reset_reseed_counter();
      }

   return bits_collected;
   }

reseed_check()

void Botan::Stateful_RNG::reseed_check ( )

protected

Definition at line 74 of file stateful_rng.cpp.

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

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

   {
   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 Exception("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;
      }
   }

reseed_from_rng()

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

finaloverridevirtual

Reseed by reading specified bits from the RNG

Reimplemented from Botan::RandomNumberGenerator.

Definition at line 64 of file stateful_rng.cpp.

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

Referenced by reseed_check().

   {
   RandomNumberGenerator::reseed_from_rng(rng, poll_bits);

   if(poll_bits >= security_level())
      {
      reset_reseed_counter();
      }
   }

reseed_interval()

size_t Botan::Stateful_RNG::reseed_interval ( ) const

inline

Definition at line 120 of file stateful_rng.h.

{ return m_reseed_interval; }

reset_reseed_counter()

void Botan::Stateful_RNG::reset_reseed_counter ( )

inlineprotected

Called by a subclass to notify that a reseed has been successfully performed.

Definition at line 131 of file stateful_rng.h.

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

{ m_reseed_counter = 1; }

security_level()

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

pure virtual

Returns

intended security level of this DRBG

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

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

---

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