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/*
* Randpool
* (C) 1999-2009 Jack Lloyd
*
* Distributed under the terms of the Botan license
*/
#include <botan/randpool.h>
#include <botan/get_byte.h>
#include <botan/internal/xor_buf.h>
#include <botan/internal/stl_util.h>
#include <algorithm>
namespace Botan {
namespace {
/*
* PRF based on a MAC
*/
enum RANDPOOL_PRF_TAG {
CIPHER_KEY = 0,
MAC_KEY = 1,
GEN_OUTPUT = 2
};
}
/*
* Generate a buffer of random bytes
*/
void Randpool::randomize(byte out[], size_t length)
{
if(!is_seeded())
throw PRNG_Unseeded(name());
update_buffer();
while(length)
{
const size_t copied = std::min<size_t>(length, buffer.size());
copy_mem(out, &buffer[0], copied);
out += copied;
length -= copied;
update_buffer();
}
}
/*
* Refill the output buffer
*/
void Randpool::update_buffer()
{
for(size_t i = 0; i != counter.size(); ++i)
if(++counter[i])
break;
mac->update(static_cast<byte>(GEN_OUTPUT));
mac->update(counter);
SecureVector<byte> mac_val = mac->final();
for(size_t i = 0; i != mac_val.size(); ++i)
buffer[i % buffer.size()] ^= mac_val[i];
cipher->encrypt(buffer);
if(counter[0] % ITERATIONS_BEFORE_RESEED == 0)
mix_pool();
}
/*
* Mix the entropy pool
*/
void Randpool::mix_pool()
{
const size_t BLOCK_SIZE = cipher->BLOCK_SIZE;
mac->update(static_cast<byte>(MAC_KEY));
mac->update(pool);
mac->set_key(mac->final());
mac->update(static_cast<byte>(CIPHER_KEY));
mac->update(pool);
cipher->set_key(mac->final());
xor_buf(pool, buffer, BLOCK_SIZE);
cipher->encrypt(pool);
for(size_t i = 1; i != POOL_BLOCKS; ++i)
{
const byte* previous_block = &pool[BLOCK_SIZE*(i-1)];
byte* this_block = &pool[BLOCK_SIZE*i];
xor_buf(this_block, previous_block, BLOCK_SIZE);
cipher->encrypt(this_block);
}
update_buffer();
}
/*
* Reseed the internal state
*/
void Randpool::reseed(size_t poll_bits)
{
Entropy_Accumulator_BufferedComputation accum(*mac, poll_bits);
if(!entropy_sources.empty())
{
size_t poll_attempt = 0;
while(!accum.polling_goal_achieved() && poll_attempt < poll_bits)
{
entropy_sources[poll_attempt % entropy_sources.size()]->poll(accum);
++poll_attempt;
}
}
SecureVector<byte> mac_val = mac->final();
xor_buf(pool, mac_val, mac_val.size());
mix_pool();
if(accum.bits_collected() >= poll_bits)
seeded = true;
}
/*
* Add user-supplied entropy
*/
void Randpool::add_entropy(const byte input[], size_t length)
{
SecureVector<byte> mac_val = mac->process(input, length);
xor_buf(pool, mac_val, mac_val.size());
mix_pool();
if(length)
seeded = true;
}
/*
* Add another entropy source to the list
*/
void Randpool::add_entropy_source(EntropySource* src)
{
entropy_sources.push_back(src);
}
/*
* Clear memory of sensitive data
*/
void Randpool::clear()
{
cipher->clear();
mac->clear();
zeroise(pool);
zeroise(buffer);
zeroise(counter);
seeded = false;
}
/*
* Return the name of this type
*/
std::string Randpool::name() const
{
return "Randpool(" + cipher->name() + "," + mac->name() + ")";
}
/*
* Randpool Constructor
*/
Randpool::Randpool(BlockCipher* cipher_in,
MessageAuthenticationCode* mac_in,
size_t pool_blocks,
size_t iter_before_reseed) :
ITERATIONS_BEFORE_RESEED(iter_before_reseed),
POOL_BLOCKS(pool_blocks),
cipher(cipher_in),
mac(mac_in)
{
const size_t BLOCK_SIZE = cipher->BLOCK_SIZE;
const size_t OUTPUT_LENGTH = mac->output_length();
if(OUTPUT_LENGTH < BLOCK_SIZE ||
!cipher->valid_keylength(OUTPUT_LENGTH) ||
!mac->valid_keylength(OUTPUT_LENGTH))
{
delete cipher;
delete mac;
throw Internal_Error("Randpool: Invalid algorithm combination " +
cipher->name() + "/" + mac->name());
}
buffer.resize(BLOCK_SIZE);
pool.resize(POOL_BLOCKS * BLOCK_SIZE);
counter.resize(12);
seeded = false;
}
/*
* Randpool Destructor
*/
Randpool::~Randpool()
{
delete cipher;
delete mac;
std::for_each(entropy_sources.begin(), entropy_sources.end(),
del_fun<EntropySource>());
}
}
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