         # File lib/em/protocols/smtpserver.rb, line 259
    259:       def process_auth str
    260:         if @state.include?(:auth)
    261:           send_data "503 auth already issued\r\n"
    262:         elsif str =~ /\APLAIN\s+/i
    263:           plain = ($'.dup).unpack("m").first # Base64::decode64($'.dup)
    264:           discard,user,psw = plain.split("\000")
    265:           if receive_plain_auth user,psw
    266:             send_data "235 authentication ok\r\n"
    267:             @state << :auth
    268:           else
    269:             send_data "535 invalid authentication\r\n"
    270:           end
    271:           #elsif str =~ /\ALOGIN\s+/i
    272:         else
    273:           send_data "504 auth mechanism not available\r\n"
    274:         end
    275:       end