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