/// <inheritdoc/>
public string GeneratePassword(byte[] key, long counter, IPasswordLength length)
{
if (key == null)
{
throw new ArgumentNullException(nameof(key));
}
if (counter < 0)
{
throw new ArgumentOutOfRangeException(
nameof(counter),
"A positive value must be supplied for the counter.");
}
if (length.Digits < 0 || length.Digits > 8)
{
throw new ArgumentOutOfRangeException(
nameof(length.Digits),
"Only passwords of between 1 and 8 digits in length can be generated.");
}
using (var hmac = new HMACSHA1())
{
return(GeneratePassword(key, counter, length, hmac));
}
}
public string GeneratePassword(byte[] key, int step, IPasswordLength length, HMAC hmac)
{
if (key == null)
{
throw new ArgumentNullException(nameof(key));
}
if (step < 1)
{
throw new ArgumentOutOfRangeException(nameof(step), "A positive value must be supplied for step.");
}
if (length.Digits < 0 || length.Digits > 8)
{
throw new ArgumentOutOfRangeException(
nameof(length.Digits),
"Only passwords of between 1 and 8 digits in length can be generated.");
}
if (hmac == null)
{
throw new ArgumentNullException(nameof(hmac));
}
return(this.GeneratePassword(key, DateTime.UtcNow, step, length, hmac));
}
public void APassword_OfTheCorrectNumberOfDigits_IsGenerated(long counter, IPasswordLength length, int expectedLength)
{
// Arrange
var secret = Encoding.UTF8.GetBytes("000000000000");
var otpGenerator = new HotpGenerator();
// Act
var password = otpGenerator.GeneratePassword(secret, counter, length);
// Assert
Assert.Equal(password.Length, expectedLength);
}
public string GeneratePassword(byte[] key, IPasswordLength length, HMAC hmac)
{
if (key == null)
{
throw new ArgumentNullException(nameof(key));
}
if (length.Digits < 0 || length.Digits > 8)
{
throw new ArgumentOutOfRangeException(
nameof(length.Digits),
"Only passwords of between 1 and 8 digits in length can be generated.");
}
if (hmac == null)
{
throw new ArgumentNullException(nameof(hmac));
}
TimeSpan span = (DateTime.Now.ToUniversalTime() - Epoch);
return(this.GeneratePassword(key, DateTime.UtcNow, 60, length, hmac));
}
internal string GeneratePassword(byte[] key, long counter, IPasswordLength length, HMAC hmac)
{
var text = BitConverter.GetBytes(counter);
if (!BitConverter.IsLittleEndian)
{
Array.Reverse(text);
}
Array.Resize(ref text, 8);
Array.Reverse(text);
hmac.Key = key;
var hash = hmac.ComputeHash(text);
int offset = hash[hash.Length - 1] & 0xf;
int binary = (hash[offset] & 0x7f) << 24
| (hash[offset + 1] & 0xff) << 16
| (hash[offset + 2] & 0xff) << 8
| (hash[offset + 3] & 0xff);
int password = binary % length.Power;
return(password.ToString(length.Format));
}
internal string GeneratePassword(byte[] key, DateTime date, int step, IPasswordLength length, HMAC hmac)
{
TimeSpan span = (date.ToUniversalTime() - Epoch);
return(Otp.Hotp.GeneratePassword(key, (long)span.TotalSeconds / step, length, hmac));
}
