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/*
* HMAC_DRBG
* (C) 2014,2015 Jack Lloyd
*
* Botan is released under the Simplified BSD License (see license.txt)
*/
#include <botan/hmac_drbg.h>
#include <algorithm>
namespace Botan {
HMAC_DRBG::HMAC_DRBG(MessageAuthenticationCode* mac,
RandomNumberGenerator* prng) :
m_mac(mac),
m_prng(prng),
m_V(m_mac->output_length(), 0x01),
m_reseed_counter(0)
{
m_mac->set_key(std::vector<byte>(m_mac->output_length(), 0x00));
}
HMAC_DRBG::HMAC_DRBG(const std::string& mac_name,
RandomNumberGenerator* prng) :
m_prng(prng),
m_reseed_counter(0)
{
m_mac = MessageAuthenticationCode::create(mac_name);
if(!m_mac)
throw Algorithm_Not_Found(mac_name);
m_V = secure_vector<byte>(m_mac->output_length(), 0x01),
m_mac->set_key(std::vector<byte>(m_mac->output_length(), 0x00));
}
void HMAC_DRBG::randomize(byte out[], size_t length)
{
if(!is_seeded() || m_reseed_counter > BOTAN_RNG_MAX_OUTPUT_BEFORE_RESEED)
reseed(m_mac->output_length() * 8);
if(!is_seeded())
throw PRNG_Unseeded(name());
while(length)
{
const size_t to_copy = std::min(length, m_V.size());
m_V = m_mac->process(m_V);
copy_mem(out, m_V.data(), to_copy);
length -= to_copy;
out += to_copy;
}
m_reseed_counter += length;
update(nullptr, 0); // additional_data is always empty
}
/*
* Reset V and the mac key with new values
*/
void HMAC_DRBG::update(const byte input[], size_t input_len)
{
m_mac->update(m_V);
m_mac->update(0x00);
m_mac->update(input, input_len);
m_mac->set_key(m_mac->final());
m_V = m_mac->process(m_V);
if(input_len)
{
m_mac->update(m_V);
m_mac->update(0x01);
m_mac->update(input, input_len);
m_mac->set_key(m_mac->final());
m_V = m_mac->process(m_V);
}
}
void HMAC_DRBG::reseed(size_t poll_bits)
{
if(m_prng)
{
m_prng->reseed(poll_bits);
if(m_prng->is_seeded())
{
secure_vector<byte> input = m_prng->random_vec(m_mac->output_length());
update(input.data(), input.size());
m_reseed_counter = 1;
}
}
}
void HMAC_DRBG::add_entropy(const byte input[], size_t length)
{
update(input, length);
m_reseed_counter = 1;
}
bool HMAC_DRBG::is_seeded() const
{
return m_reseed_counter > 0;
}
void HMAC_DRBG::clear()
{
m_reseed_counter = 0;
for(size_t i = 0; i != m_V.size(); ++i)
m_V[i] = 0x01;
m_mac->set_key(std::vector<byte>(m_mac->output_length(), 0x00));
if(m_prng)
m_prng->clear();
}
std::string HMAC_DRBG::name() const
{
return "HMAC_DRBG(" + m_mac->name() + ")";
}
}
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