Botan 3.3.0
Crypto and TLS for C&
totp.cpp
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1/*
2* TOTP
3* (C) 2017 Jack Lloyd
4*
5* Botan is released under the Simplified BSD License (see license.txt)
6*/
7
8#include <botan/otp.h>
9
10#include <botan/internal/calendar.h>
11
12namespace Botan {
13
14TOTP::TOTP(const uint8_t key[], size_t key_len, std::string_view hash_algo, size_t digits, size_t time_step) :
15 m_hotp(key, key_len, hash_algo, digits),
16 m_time_step(time_step),
17 m_unix_epoch(calendar_point(1970, 1, 1, 0, 0, 0).to_std_timepoint()) {
18 /*
19 * Technically any time step except 0 is valid, but 30 is typical
20 * and over 5 minutes seems unlikely.
21 */
22 BOTAN_ARG_CHECK(m_time_step > 0 && m_time_step < 300, "Invalid TOTP time step");
23}
24
25uint32_t TOTP::generate_totp(std::chrono::system_clock::time_point current_time) {
26 const uint64_t unix_time = std::chrono::duration_cast<std::chrono::seconds>(current_time - m_unix_epoch).count();
27 return this->generate_totp(unix_time);
28}
29
30uint32_t TOTP::generate_totp(uint64_t unix_time) {
31 return m_hotp.generate_hotp(unix_time / m_time_step);
32}
33
34bool TOTP::verify_totp(uint32_t otp, std::chrono::system_clock::time_point current_time, size_t clock_drift_accepted) {
35 const uint64_t unix_time = std::chrono::duration_cast<std::chrono::seconds>(current_time - m_unix_epoch).count();
36 return verify_totp(otp, unix_time, clock_drift_accepted);
37}
38
39bool TOTP::verify_totp(uint32_t otp, uint64_t unix_time, size_t clock_drift_accepted) {
40 uint64_t t = unix_time / m_time_step;
41
42 for(size_t i = 0; i <= clock_drift_accepted; ++i) {
43 if(m_hotp.generate_hotp(t - i) == otp) {
44 return true;
45 }
46 }
47
48 return false;
49}
50
51} // namespace Botan
#define BOTAN_ARG_CHECK(expr, msg)
Definition assert.h:29
uint32_t generate_hotp(uint64_t counter)
Definition hotp.cpp:43
uint32_t generate_totp(std::chrono::system_clock::time_point time_point)
Definition totp.cpp:25
TOTP(const SymmetricKey &key, std::string_view hash_algo="SHA-1", size_t digits=6, size_t time_step=30)
Definition otp.h:71
bool verify_totp(uint32_t otp, std::chrono::system_clock::time_point time, size_t clock_drift_accepted=0)
Definition totp.cpp:34