Need to get some information how counter value is handled in this library.
std::string generateTOTP(const std::string& secretKey) {
using namespace CryptoPP;
const int timeStep = 30; // Time step in seconds
SecByteBlock key(HMAC<SHA1>::DEFAULT_KEYLENGTH);
StringSource(secretKey, true, new Base32Decoder(new ArraySink(key,
key.size())));
// Get the current time in 30-second intervals (TOTP time step)
std::time_t currentTime = std::time(nullptr);
uint64_t counter = static_cast<uint64_t>(currentTime) / timeStep;
const size_t byteArraySize = sizeof(counter);
byte* byteArray = new byte[byteArraySize];
//Big endian representation
for (size_t i = 0; i < byteArraySize; ++i) {
byteArray[sizeof(counter) - 1 - i] = static_cast<byte>((counter >> (8 * i))
& 0xFF);
}
// Calculate the HMAC-SHA1 using the secret key and the counter bytes
byte mac[CryptoPP::HMAC<CryptoPP::SHA1>::DIGESTSIZE];
CryptoPP::HMAC<CryptoPP::SHA1> hmac(key, sizeof(key));
hmac.Update(byteArray, sizeof(byteArraySize));
hmac.Final(mac);
// Generate the TOTP value from the last 4 bits of the HMAC-SHA1 result
int offset = mac[CryptoPP::HMAC<CryptoPP::SHA1>::DIGESTSIZE - 1] & 0xF;
uint32_t otpValue = (mac[offset] & 0x7F) << 24 |
(mac[offset + 1] & 0xFF) << 16 |
(mac[offset + 2] & 0xFF) << 8 |
(mac[offset + 3] & 0xFF);
// Convert the OTP value to a 6-digit OTP (modulo 10^6)
otpValue %= 1000000;
//Format the OTP as a 6-digit string with leading zeros if needed
std::string otp = std::to_string(otpValue);
otp.insert(otp.begin(), 6 - otp.size(), '0');
delete[] byteArray;
return otp;
}
This code have issues with hmac.update(). Seems problem with counter
value.Does anyone help to generate correct otp?
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