public Totp(string base32Secret)
{
byte[] secretBytes = Base32.ToByteArray(base32Secret);
DateTime utcNow = DateTime.UtcNow;
long unixNow = ToUnixTime(utcNow);
long timestamp = Convert.ToInt64(unixNow / FREQUENCY_SECONDS);
byte[] timestampBytes = BitConverter.GetBytes(timestamp).ToArray();
// IBM PC architecture is little endian
Array.Reverse(timestampBytes);
using (HMACSHA1 hmac = new HMACSHA1(secretBytes)) {
byte[] hmacBytes = hmac.ComputeHash(timestampBytes);
int offset = hmacBytes.Last() & 0x0F;
int firstByte = (hmacBytes[offset + 0] & 0x7F) << 24;
int secondByte = hmacBytes[offset + 1] << 16;
int thirdByte = hmacBytes[offset + 2] << 8;
int fourthByte = hmacBytes[offset + 3];
int authenticationCode =
(firstByte | secondByte | thirdByte | fourthByte) % 1000000;
// pad with leading zeroes
AuthenticationCode = authenticationCode.ToString().PadLeft(6, '0');
ExpiryUtc = GetExpiry(utcNow);
}
}
public async Task <string> GenerateQRCode(string secret)
{
var user = await _userManager.GetUserAsync(_httpContextAccessor.HttpContext.User);
QRCodeGenerator qrGenerator = new QRCodeGenerator();
var buffer = Base32.ToByteArray(secret);
var secretBase32 = Base32.ToString(buffer);
string payload = $"otpauth://totp/BorovClub:{user.Email}?secret={secret}&issuer=BorovClub&algorithm=SHA1&digits=6&period=30";
QRCodeData qrCodeData = qrGenerator.CreateQrCode(payload, QRCodeGenerator.ECCLevel.Q);
Base64QRCode qrCode = new Base64QRCode(qrCodeData);
string qrCodeImageAsBase64 = qrCode.GetGraphic(20);
user.TwoFactorEnabled = true;
user.TotpSecret = secretBase32;
await _userManager.UpdateAsync(user);
await _dbContext.SaveChangesAsync();
return(qrCodeImageAsBase64);
}