Botan::ESDM_RNG Class Reference

#include <esdm_rng.h>

Inheritance diagram for Botan::ESDM_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
	ESDM_RNG ()
	ESDM_RNG (bool prediction_resistance)
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

Entropy Source and DRNG Manager (ESDM) is a Linux/Unix based PRNG manager, which can be seeded from NTG.1/SP800-90B sources.

See:

• Repository: https://github.com/smuellerDD/esdm
• Further Docs: https://www.chronox.de/esdm/index.html

Different entropy sources can be configured in respect of being active and how much entropy is accounted for each of them.

ESDM tracks its seed and reseed status and blocks, when not fully seeded. For this functionality, the esdm_rpcc_get_random_bytes_pr (prediction resistant) or esdm_rpcc_get_random_bytes_full (fully seeded) calls have to be used.

Configurable modes:

• fully seeded (-> fast): provide entropy from a DRBG/PRNG after beeing fully seeded, block until this point is reached, reseed from after a time and/or invocation limit, block again if reseeding is not possible
• prediction resistance (-> slow): reseed ESDM with fresh entropy after each invocation

You typically want to use the fast fully seeded mode, which is the default.

Instances of this class communicate over RPC with ESDM. The esdm_rpc_client library, provided by ESDM, is leveraged for this.

Thread safety: It is fine to construct, destruct and use objects of this class concurrently. The communication with ESDM is thread-safe, as handled by esdm_rpc_client. The initialization of esdm_rpc_client is not thread safe, therefore this class takes care of it, with its embedded ESDM_Context.

Definition at line 53 of file esdm_rng.h.

Constructor & Destructor Documentation

ESDM_RNG() [1/2]

Botan::ESDM_RNG::ESDM_RNG ( )

inline

Default constructor for ESDM, fully seeded mode

Definition at line 58 of file esdm_rng.h.

: ESDM_RNG(false) {}

ESDM_RNG() [2/2]

Botan::ESDM_RNG::ESDM_RNG ( bool prediction_resistance )

explicit

Construct ESDM instance with configurable mode

Definition at line 55 of file esdm_rng.cpp.

                                             :
      m_prediction_resistance(prediction_resistance), m_ctx(ESDM_Context::instance()) {}

Member Function Documentation

accepts_input()

bool Botan::ESDM_RNG::accepts_input ( ) const

inlineoverridevirtual

ESDM can inject additional inputs but we do not account entropy for it

Returns

true

Implements Botan::RandomNumberGenerator.

Definition at line 86 of file esdm_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(), 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::ESDM_RNG::clear ( )

inlineoverridevirtual

the ESDM RNG does not hold any state outside ESDM, that should be cleared here

Implements Botan::RandomNumberGenerator.

Definition at line 92 of file esdm_rng.h.

{}

fill_bytes_with_input()

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

overrideprotectedvirtual

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 58 of file esdm_rng.cpp.

                                                                                    {
   /*
   * This variable is implicitly set by the "esdm_invoke" macro that comes
   * with the ESDM library. "esdm_invoke" implements a retry mechanism for
   * the underlying RPC mechanism of ESDM.
   */
   ssize_t ret = 0;
 
   if(!in.empty()) {
      ret = 0;
 
      /*
      * take additional input, but do not account entropy for it,
      * as this information is not included in the API
      */
      esdm_invoke(esdm_rpcc_write_data(in.data(), in.size()));
      /*
      * ret was set by esdm_invoke, as mentioned above
      */
      if(ret != 0) {
         throw Botan::System_Error("Writing additional input to ESDM failed");
      }
   }
 
   if(!out.empty()) {
      ret = 0;
 
      if(m_prediction_resistance) {
         esdm_invoke(esdm_rpcc_get_random_bytes_pr(out.data(), out.size()));
      } else {
         esdm_invoke(esdm_rpcc_get_random_bytes_full(out.data(), out.size()));
      }
      /*
      * ret was set by esdm_invoke, as mentioned above
      */
      if(ret != static_cast<ssize_t>(out.size())) {
         throw Botan::System_Error("Fetching random bytes from ESDM failed");
      }
   }
}

is_seeded()

bool Botan::ESDM_RNG::is_seeded ( ) const

inlineoverridevirtual

ESDM blocks, if it is not seeded,

Returns

true

Implements Botan::RandomNumberGenerator.

Definition at line 78 of file esdm_rng.h.

{ return true; }

name()

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

inlineoverridevirtual

Returns

the name of this RNG type

Implements Botan::RandomNumberGenerator.

Definition at line 65 of file esdm_rng.h.

                                      {
         if(m_prediction_resistance) {
            return "esdm-pr";
         } else {
            return "esdm-full";
         }
      }

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::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(), 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 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 Botan::RandomNumberGenerator::accepts_input(), BOTAN_UNUSED, Botan::RandomNumberGenerator::fill_bytes_with_input(), Botan::OS::get_high_resolution_clock(), Botan::OS::get_process_id(), 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 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 Botan::RandomNumberGenerator::accepts_input(), BOTAN_UNUSED, 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 63 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/esdm_rng/esdm_rng.h
• src/lib/rng/esdm_rng/esdm_rng.cpp