Rainbow.CSharp.SDK.Cryptography 1.1.0

Provides ability to create objects implementing SASLMechanism.

These objects handle the SCRAM mechanism of SASL.

No strings are allocated during challenge. Only client-side mechanisms are provided.

Based on https://github.com/stazz/FluentCryptography and https://github.com/stazz/UtilPack

Code has been reworked:

• to only support SCRAM-SHA-1, SCRAM-SHA-256 and SCRAM-SHA-512
• to support .Net standard 2.0, 2.1, .Net 6.0 and .Net 8.0

Unnecessary code has been removed.

Example of use:

var credentials = new SASLCredentialsSCRAMForClient(
         userName,
         password // password may be clear-text password as string, or result of PBKDF2 iteration as byte array.
       );
       
String type = "SCRAM-SHA-512"; // To define which encryption must be used       
       
switch (type)
{

    case "SCRAM-SHA-1":
        var sha1 = new Rainbow.Cryptography.Digest.SHA128();
        client = sha1.CreateSASLClientSCRAM();
        break;

    case "SCRAM-SHA-256":
        var sha256 = new Rainbow.Cryptography.Digest.SHA256();
        client = sha256.CreateSASLClientSCRAM();
        break;

    case "SCRAM-SHA-512":
        var sha512 = new Rainbow.Cryptography.Digest.SHA512();
        client = sha512.CreateSASLClientSCRAM();
        break;
}

var encoding = new UTF8Encoding(false, false).CreateDefaultEncodingInfo();
var writeArray = new ResizableArray<Byte>();

var firstMessageToServer = Convert.ToBase64String( ComputeInitialResponse()); 

// => Need to send the first message to the server and read it's answer

var firstMessageFromServer = "..."; // <= Here it's the content of the server reponse

byte[] data = Convert.FromBase64String(firstMessageFromServer);
var secondMessageToServer = Convert.ToBase64String( ComputeFinalResponse(data));

// => Need to send the second message to the server and read it's answer

var secondMessageFromServer = "..."; // <= Here it's the content of the server reponse

data = Convert.FromBase64String(secondMessageFromServer);
VerifyServerSignature(data); // => If no exception, the authentication process is a success

private byte[] ComputeInitialResponse()
{

    var challengeArguments = credentials.CreateChallengeArguments(
      null, // Initial phase does not read anything
      -1,
      -1,
      writeArray,
      0,
      encoding
      );

    try
    {
        var task = client.ChallengeOrThrowOnErrorAsync(challengeArguments);
        (var bytesWritten, var challengeResult) = task.Result;

        if (bytesWritten > 0)
        {
            byte[] result = new byte[bytesWritten];
            Array.Copy(writeArray.Array, result, bytesWritten);
            return result;
        }
    }
    catch
    {

    }
    return new byte[0];
}

private byte[] ComputeFinalResponse(byte[] challenge)
{
    var challengeArguments = credentials.CreateChallengeArguments(
      challenge,
      0,
      challenge.Length,
      writeArray,
      0,
      encoding
      );

    try
    {
        var task = client.ChallengeOrThrowOnErrorAsync(challengeArguments);
        (var bytesWritten, var challengeResult) = task.Result;

        if (bytesWritten > 0)
        {
            byte[] result = new byte[bytesWritten];
            Array.Copy(writeArray.Array, result, bytesWritten);
            return result;
        }
    }
    catch
    {

    }
    return new byte[0];
}

private byte[] VerifyServerSignature(byte[] challenge)
{
    var challengeArguments = credentials.CreateChallengeArguments(
      challenge,
      0,
      challenge.Length,
      writeArray,
      0,
      encoding
      );

    var task = client.ChallengeOrThrowOnErrorAsync(challengeArguments);
    (var bytesWritten, var challengeResult) = task.Result;

    if(challengeResult == SASLChallengeResult.Completed)
        return new byte[0];

    throw new Exception("Server signature has not been verified with success");

}