internal static byte[] SignChallenge(OtpInfo otp, byte[] challenge, uint unixSeconds)
{
if (challenge.Length != ChallengeSize)
{
throw new ArgumentOutOfRangeException(
"challenge",
challenge.Length,
string.Format("Challenge must be {0} bytes long", ChallengeSize));
}
using (var s = new MemoryStream(1024))
{
s.Write(otp.Suite, 0, otp.Suite.Length);
s.WriteByte(0);
s.Write(challenge, 0, challenge.Length);
var z = BitConverter.GetBytes((UInt32)0);
s.Write(z, 0, z.Length);
var time = (unixSeconds - otp.StartTime) / otp.TimeStep;
var t = BitConverter.GetBytes((UInt32)time);
if (BitConverter.IsLittleEndian)
{
Array.Reverse(t);
}
s.Write(t, 0, t.Length);
return(Hmac(otp.HmacSeed, s.ToArray()));
}
}
// Checks that the OTP info is something we can work with. The Chrome
// extension also supports only this subset. They don't validate as much,
// just assume the values are what they expect.
public static void ValidateOtpInfo(OtpInfo otp)
{
Action <object, object, string> throwError = (actual, expected, name) =>
{
throw new ArgumentException(
string.Format("Invalid OTP {0} (expected {1}, got {2})",
name,
expected,
actual));
};
Action <int, int, string> verify = (actual, expected, name) =>
{
if (actual != expected)
{
throwError(actual, expected, name);
}
};
verify(otp.Version, 3, "version");
verify(otp.OtpAlgorithm, 1, "algorithm");
verify(otp.OtpLength, 0, "length");
verify(otp.HashAlgorithm, 2, "hash");
verify(otp.HmacSeed.Length, 32, "HMAC length");
verify(otp.Iptmk.Length, 32, "IPTMK length");
const string suite = "OCRA-1:HOTP-SHA256-0:QA08";
if (!otp.Suite.SequenceEqual(suite.ToBytes()))
{
throwError(otp.Suite, suite, "suite");
}
}
internal static byte[] SignChallenge(OtpInfo otp, byte[] challenge, uint unixSeconds)
{
if (challenge.Length != ChallengeSize)
{
throw new InternalErrorException($"Challenge must be {ChallengeSize} bytes long");
}
using var s = new MemoryStream(1024);
s.Write(otp.Suite, 0, otp.Suite.Length);
s.WriteByte(0);
s.Write(challenge, 0, challenge.Length);
var z = BitConverter.GetBytes(0u);
s.Write(z, 0, z.Length);
var time = (unixSeconds - otp.StartTime) / otp.TimeStep;
var t = BitConverter.GetBytes((uint)time);
if (BitConverter.IsLittleEndian)
{
Array.Reverse(t);
}
s.Write(t, 0, t.Length);
return(Crypto.HmacSha256(otp.HmacSeed, s.ToArray()));
}
public static OtpChallenge GenerateRandomOtpChallenge(OtpInfo otp)
{
var challenge = RandomBytes(ChallengeSize);
var time = DateTime.UtcNow;
return(new OtpChallenge(challenge,
time,
SignChallenge(otp, challenge, time.UnixSeconds())));
}
/// <summary>
/// When overridden in a descendant class, deserializes the object from an XML according to Aadhaar API specification.
/// </summary>
/// <param name="element">An instance of <see cref="XElement"/>.</param>
protected override void DeserializeXml(XElement element)
{
base.DeserializeXml(element);
IsOtpSent = element.Attribute("ret").Value[0] == AadhaarHelper.Yes;
var info = element.Attribute("info")?.Value;
Info = info != null ? new OtpInfo {
InfoValue = info
} : null;
}
