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/*
* Randpool Source File
* (C) 1999-2009 Jack Lloyd
*/
#include <botan/randpool.h>
#include <botan/loadstor.h>
#include <botan/xor_buf.h>
#include <botan/util.h>
#include <botan/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[], u32bit length)
{
if(!is_seeded())
throw PRNG_Unseeded(name());
update_buffer();
while(length)
{
const u32bit copied = std::min(length, buffer.size());
copy_mem(out, buffer.begin(), copied);
out += copied;
length -= copied;
update_buffer();
}
}
/**
* Refill the output buffer
*/
void Randpool::update_buffer()
{
const u64bit timestamp = system_time();
for(u32bit i = 0; i != counter.size(); ++i)
if(++counter[i])
break;
store_be(timestamp, counter + 4);
mac->update(static_cast<byte>(GEN_OUTPUT));
mac->update(counter, counter.size());
SecureVector<byte> mac_val = mac->final();
for(u32bit 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 u32bit BLOCK_SIZE = cipher->BLOCK_SIZE;
mac->update(static_cast<byte>(MAC_KEY));
mac->update(pool, pool.size());
mac->set_key(mac->final());
mac->update(static_cast<byte>(CIPHER_KEY));
mac->update(pool, pool.size());
cipher->set_key(mac->final());
xor_buf(pool, buffer, BLOCK_SIZE);
cipher->encrypt(pool);
for(u32bit 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(u32bit poll_bits)
{
Entropy_Accumulator_BufferedComputation accum(*mac, poll_bits);
for(u32bit i = 0; i != entropy_sources.size(); ++i)
{
entropy_sources[i]->poll(accum);
if(accum.polling_goal_achieved())
break;
}
SecureVector<byte> mac_val = mac->final();
xor_buf(pool, mac_val, mac_val.size());
mix_pool();
entropy = std::min<u32bit>(entropy + accum.bits_collected(),
8 * mac_val.size());
}
/**
* Add user-supplied entropy
*/
void Randpool::add_entropy(const byte input[], u32bit length)
{
SecureVector<byte> mac_val = mac->process(input, length);
xor_buf(pool, mac_val, mac_val.size());
mix_pool();
// Assume 1 bit conditional entropy per byte of input
entropy = std::min<u32bit>(entropy + length, 8 * mac_val.size());
}
/**
* Add another entropy source to the list
*/
void Randpool::add_entropy_source(EntropySource* src)
{
entropy_sources.push_back(src);
}
/**
* Check if the the pool is seeded
*/
bool Randpool::is_seeded() const
{
return (entropy >= 7 * mac->OUTPUT_LENGTH);
}
/**
* Clear memory of sensitive data
*/
void Randpool::clear() throw()
{
cipher->clear();
mac->clear();
pool.clear();
buffer.clear();
counter.clear();
entropy = 0;
}
/**
* 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,
u32bit pool_blocks,
u32bit iter_before_reseed) :
ITERATIONS_BEFORE_RESEED(iter_before_reseed),
POOL_BLOCKS(pool_blocks),
cipher(cipher_in),
mac(mac_in)
{
const u32bit BLOCK_SIZE = cipher->BLOCK_SIZE;
const u32bit 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.create(BLOCK_SIZE);
pool.create(POOL_BLOCKS * BLOCK_SIZE);
counter.create(12);
entropy = 0;
}
/**
* Randpool Destructor
*/
Randpool::~Randpool()
{
delete cipher;
delete mac;
std::for_each(entropy_sources.begin(), entropy_sources.end(),
del_fun<EntropySource>());
entropy = 0;
}
}
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