private static Tuple ExtractUserNameAndPassword()

in backend/MXApi/Filters/BasicAuthorizeFilter.cs [91:143]
40 lines of code
5 McCabe index (conditional complexity)

    private static Tuple<string, string> ExtractUserNameAndPassword(string authorizationParameter)
    {
      byte[] credentialBytes;

      try
      {
        credentialBytes = Convert.FromBase64String(authorizationParameter);
      }
      catch (FormatException e)
      {
        Trace.TraceWarning($"Unable to extract authentication header: {e}");
        return null;
      }

      // The currently approved HTTP 1.1 specification says characters here are ISO-8859-1.
      // However, the current draft updated specification for HTTP 1.1 indicates this encoding is infrequently
      // used in practice and defines behavior only for ASCII.
      Encoding encoding = Encoding.ASCII;

      // Make a writable copy of the encoding to enable setting a decoder fallback.
      encoding = (Encoding)encoding.Clone();

      // Fail on invalid bytes rather than silently replacing and continuing.
      encoding.DecoderFallback = DecoderFallback.ExceptionFallback;
      string decodedCredentials;

      try
      {
        decodedCredentials = encoding.GetString(credentialBytes);
      }
      catch (DecoderFallbackException e)
      {
        Trace.TraceWarning($"Unable to decode authentication header: {e}");
        return null;
      }

      if (string.IsNullOrEmpty(decodedCredentials))
      {
        Trace.TraceWarning($"Unable to find authentication header");
        return null;
      }

      int colonIndex = decodedCredentials.IndexOf(':');
      if (colonIndex == -1)
      {
        Trace.TraceWarning($"Unable to find colon in authentication header");
        return null;
      }

      string userName = decodedCredentials.Substring(0, colonIndex);
      string password = decodedCredentials.Substring(colonIndex + 1);
      return new Tuple<string, string>(userName, password);
    }