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/*
* PBKDF2
* (C) 1999-2007 Jack Lloyd
*
* Botan is released under the Simplified BSD License (see license.txt)
*/
#include <botan/pbkdf2.h>
#include <botan/loadstor.h>
#include <botan/internal/rounding.h>
namespace Botan {
PKCS5_PBKDF2* PKCS5_PBKDF2::make(const Spec& spec)
{
if(auto mac = MessageAuthenticationCode::create(spec.arg(0)))
return new PKCS5_PBKDF2(mac.release());
if(auto mac = MessageAuthenticationCode::create("HMAC(" + spec.arg(0) + ")"))
return new PKCS5_PBKDF2(mac.release());
return nullptr;
}
size_t
pbkdf2(MessageAuthenticationCode& prf,
byte out[],
size_t out_len,
const std::string& passphrase,
const byte salt[], size_t salt_len,
size_t iterations,
std::chrono::milliseconds msec)
{
clear_mem(out, out_len);
if(out_len == 0)
return 0;
try
{
prf.set_key(reinterpret_cast<const byte*>(passphrase.data()), passphrase.size());
}
catch(Invalid_Key_Length&)
{
throw Exception("PBKDF2 with " + prf.name() +
" cannot accept passphrases of length " +
std::to_string(passphrase.size()));
}
const size_t prf_sz = prf.output_length();
secure_vector<byte> U(prf_sz);
const size_t blocks_needed = round_up(out_len, prf_sz) / prf_sz;
std::chrono::microseconds usec_per_block =
std::chrono::duration_cast<std::chrono::microseconds>(msec) / blocks_needed;
u32bit counter = 1;
while(out_len)
{
const size_t prf_output = std::min<size_t>(prf_sz, out_len);
prf.update(salt, salt_len);
prf.update_be(counter++);
prf.final(U.data());
xor_buf(out, U.data(), prf_output);
if(iterations == 0)
{
/*
If no iterations set, run the first block to calibrate based
on how long hashing takes on whatever machine we're running on.
*/
const auto start = std::chrono::high_resolution_clock::now();
iterations = 1; // the first iteration we did above
while(true)
{
prf.update(U);
prf.final(U.data());
xor_buf(out, U.data(), prf_output);
iterations++;
/*
Only break on relatively 'even' iterations. For one it
avoids confusion, and likely some broken implementations
break on getting completely randomly distributed values
*/
if(iterations % 10000 == 0)
{
auto time_taken = std::chrono::high_resolution_clock::now() - start;
auto usec_taken = std::chrono::duration_cast<std::chrono::microseconds>(time_taken);
if(usec_taken > usec_per_block)
break;
}
}
}
else
{
for(size_t i = 1; i != iterations; ++i)
{
prf.update(U);
prf.final(U.data());
xor_buf(out, U.data(), prf_output);
}
}
out_len -= prf_output;
out += prf_output;
}
return iterations;
}
size_t
PKCS5_PBKDF2::pbkdf(byte key[], size_t key_len,
const std::string& passphrase,
const byte salt[], size_t salt_len,
size_t iterations,
std::chrono::milliseconds msec) const
{
return pbkdf2(*m_mac.get(), key, key_len, passphrase, salt, salt_len, iterations, msec);
}
}
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