private void doAuthentication(PGStream pgStream, String user, String password, Logger logger)
      throws IOException, SQLException {
    // Now get the response from the backend, either an error message
    // or an authentication request

    while (true) {
      int beresp = pgStream.ReceiveChar();

      switch (beresp) {
        case 'E':
          // An error occured, so pass the error message to the
          // user.
          //
          // The most common one to be thrown here is:
          // "User authentication failed"
          //
          int l_elen = pgStream.ReceiveInteger4();
          if (l_elen > 30000) {
            // if the error length is > than 30000 we assume this is really a v2 protocol
            // server, so trigger fallback.
            throw new UnsupportedProtocolException();
          }

          ServerErrorMessage errorMsg =
              new ServerErrorMessage(pgStream.ReceiveString(l_elen - 4), logger.getLogLevel());
          if (logger.logDebug()) logger.debug(" <=BE ErrorMessage(" + errorMsg + ")");
          throw new PSQLException(errorMsg);

        case 'R':
          // Authentication request.
          // Get the message length
          int l_msgLen = pgStream.ReceiveInteger4();

          // Get the type of request
          int areq = pgStream.ReceiveInteger4();

          // Process the request.
          switch (areq) {
            case AUTH_REQ_CRYPT:
              {
                byte[] rst = new byte[2];
                rst[0] = (byte) pgStream.ReceiveChar();
                rst[1] = (byte) pgStream.ReceiveChar();
                String salt = new String(rst, 0, 2, "US-ASCII");

                if (logger.logDebug())
                  logger.debug(" <=BE AuthenticationReqCrypt(salt='" + salt + "')");

                if (password == null)
                  throw new PSQLException(
                      GT.tr(
                          "The server requested password-based authentication, but no password was provided."),
                      PSQLState.CONNECTION_REJECTED);

                String result = UnixCrypt.crypt(salt, password);
                byte[] encodedResult = result.getBytes("US-ASCII");

                if (logger.logDebug()) logger.debug(" FE=> Password(crypt='" + result + "')");

                pgStream.SendChar('p');
                pgStream.SendInteger4(4 + encodedResult.length + 1);
                pgStream.Send(encodedResult);
                pgStream.SendChar(0);
                pgStream.flush();

                break;
              }

            case AUTH_REQ_MD5:
              {
                byte[] md5Salt = pgStream.Receive(4);
                if (logger.logDebug()) {
                  logger.debug(
                      " <=BE AuthenticationReqMD5(salt=" + Utils.toHexString(md5Salt) + ")");
                }

                if (password == null)
                  throw new PSQLException(
                      GT.tr(
                          "The server requested password-based authentication, but no password was provided."),
                      PSQLState.CONNECTION_REJECTED);

                byte[] digest = MD5Digest.encode(user, password, md5Salt);

                if (logger.logDebug()) {
                  logger.debug(" FE=> Password(md5digest=" + new String(digest, "US-ASCII") + ")");
                }

                pgStream.SendChar('p');
                pgStream.SendInteger4(4 + digest.length + 1);
                pgStream.Send(digest);
                pgStream.SendChar(0);
                pgStream.flush();

                break;
              }

            case AUTH_REQ_PASSWORD:
              {
                if (logger.logDebug()) {
                  logger.debug(" <=BE AuthenticationReqPassword");
                  logger.debug(" FE=> Password(password=<not shown>)");
                }

                if (password == null)
                  throw new PSQLException(
                      GT.tr(
                          "The server requested password-based authentication, but no password was provided."),
                      PSQLState.CONNECTION_REJECTED);

                byte[] encodedPassword = password.getBytes("US-ASCII");

                pgStream.SendChar('p');
                pgStream.SendInteger4(4 + encodedPassword.length + 1);
                pgStream.Send(encodedPassword);
                pgStream.SendChar(0);
                pgStream.flush();

                break;
              }

            case AUTH_REQ_OK:
              if (logger.logDebug()) logger.debug(" <=BE AuthenticationOk");

              return; // We're done.

            default:
              if (logger.logDebug())
                logger.debug(" <=BE AuthenticationReq (unsupported type " + ((int) areq) + ")");

              throw new PSQLException(
                  GT.tr(
                      "The authentication type {0} is not supported. Check that you have configured the pg_hba.conf file to include the client''s IP address or subnet, and that it is using an authentication scheme supported by the driver.",
                      new Integer(areq)),
                  PSQLState.CONNECTION_REJECTED);
          }

          break;

        default:
          throw new PSQLException(
              GT.tr("Protocol error.  Session setup failed."),
              PSQLState.CONNECTION_UNABLE_TO_CONNECT);
      }
    }
  }
 public int getServerVersionNum() {
   if (serverVersionNum != 0) return serverVersionNum;
   return Utils.parseServerVersionStr(serverVersion);
 }