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/*
* HMAC
* (C) 1999-2007,2014 Jack Lloyd
* 2007 Yves Jerschow
*
* Botan is released under the Simplified BSD License (see license.txt)
*/
#include <botan/hmac.h>
namespace Botan {
/*
* Update a HMAC Calculation
*/
void HMAC::add_data(const uint8_t input[], size_t length)
{
verify_key_set(m_ikey.empty() == false);
m_hash->update(input, length);
}
/*
* Finalize a HMAC Calculation
*/
void HMAC::final_result(uint8_t mac[])
{
verify_key_set(m_okey.empty() == false);
m_hash->final(mac);
m_hash->update(m_okey);
m_hash->update(mac, output_length());
m_hash->final(mac);
m_hash->update(m_ikey);
}
Key_Length_Specification HMAC::key_spec() const
{
// Support very long lengths for things like PBKDF2 and the TLS PRF
return Key_Length_Specification(0, 4096);
}
/*
* HMAC Key Schedule
*/
void HMAC::key_schedule(const uint8_t key[], size_t length)
{
m_hash->clear();
m_ikey.resize(m_hash->hash_block_size());
m_okey.resize(m_hash->hash_block_size());
const uint8_t ipad = 0x36;
const uint8_t opad = 0x5C;
std::fill(m_ikey.begin(), m_ikey.end(), ipad);
std::fill(m_okey.begin(), m_okey.end(), opad);
if(length > m_hash->hash_block_size())
{
secure_vector<uint8_t> hmac_key = m_hash->process(key, length);
xor_buf(m_ikey, hmac_key, hmac_key.size());
xor_buf(m_okey, hmac_key, hmac_key.size());
}
else
{
xor_buf(m_ikey, key, length);
xor_buf(m_okey, key, length);
}
m_hash->update(m_ikey);
}
/*
* Clear memory of sensitive data
*/
void HMAC::clear()
{
m_hash->clear();
zap(m_ikey);
zap(m_okey);
}
/*
* Return the name of this type
*/
std::string HMAC::name() const
{
return "HMAC(" + m_hash->name() + ")";
}
/*
* Return a clone of this object
*/
MessageAuthenticationCode* HMAC::clone() const
{
return new HMAC(m_hash->clone());
}
/*
* HMAC Constructor
*/
HMAC::HMAC(HashFunction* hash) : m_hash(hash)
{
BOTAN_ARG_CHECK(m_hash->hash_block_size() > 0,
"HMAC is not compatible with this hash function");
}
}
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