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/*
* TOTP
* (C) 2017 Jack Lloyd
*
* Botan is released under the Simplified BSD License (see license.txt)
*/
#include <botan/totp.h>
#include <botan/calendar.h>
namespace Botan {
TOTP::TOTP(const SymmetricKey& key, const std::string& hash_algo,
size_t digits, size_t time_step)
: m_hotp(key, hash_algo, digits)
, m_time_step(time_step)
, m_unix_epoch(calendar_point(1970, 1, 1, 0, 0, 0).to_std_timepoint())
{
/*
* Technically any time step except 0 is valid, but 30 is typical
* and over 5 minutes seems unlikely.
*/
if(m_time_step == 0 || m_time_step > 300)
throw Invalid_Argument("Invalid TOTP time step");
}
uint32_t TOTP::generate_totp(std::chrono::system_clock::time_point current_time)
{
const uint64_t unix_time =
std::chrono::duration_cast<std::chrono::seconds>(current_time - m_unix_epoch).count();
return this->generate_totp(unix_time);
}
uint32_t TOTP::generate_totp(uint64_t unix_time)
{
return m_hotp.generate_hotp(unix_time / m_time_step);
}
bool TOTP::verify_totp(uint32_t otp, std::chrono::system_clock::time_point current_time,
size_t clock_drift_accepted)
{
const uint64_t unix_time =
std::chrono::duration_cast<std::chrono::seconds>(current_time - m_unix_epoch).count();
return verify_totp(otp, unix_time, clock_drift_accepted);
}
bool TOTP::verify_totp(uint32_t otp, uint64_t unix_time,
size_t clock_drift_accepted)
{
uint64_t t = unix_time / m_time_step;
for(size_t i = 0; i <= clock_drift_accepted; ++i)
{
if(m_hotp.generate_hotp(t-i) == otp)
{
return true;
}
}
return false;
}
}
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