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From charl...@apache.org
Subject cvs commit: jakarta-james/proposals/v1.3/www/rfclist README rfc2554.txt
Date Thu, 14 Jun 2001 09:28:08 GMT
charlesb    01/06/14 02:28:08

  Added:       proposals/v1.3/conf james-config.xml
               proposals/v1.3/java/org/apache/james/smtpserver
                        SMTPHandler.java
               proposals/v1.3/java/org/apache/james/util Base64.java
               proposals/v1.3/www/rfclist README rfc2554.txt
  Log:
  Added SMTP_AUTH contribution by Jason Borden. Compiles but not tested.
  
  Revision  Changes    Path
  1.7       +9 -1      jakarta-james/proposals/v1.3/conf/james-config.xml
  
  
  
  
  1.1                  jakarta-james/proposals/v1.3/java/org/apache/james/smtpserver/SMTPHandler.java
  
  Index: SMTPHandler.java
  ===================================================================
  /*
   * Copyright (C) The Apache Software Foundation. All rights reserved.
   *
   * This software is published under the terms of the Apache Software License
   * version 1.1, a copy of which has been included with this distribution in
   * the LICENSE file.
   */
  package org.apache.james.smtpserver;
  
  import java.io.*;
  import java.net.*;
  import java.util.*;
  import javax.mail.*;
  import javax.mail.internet.*;
  import org.apache.avalon.framework.activity.Initializable;
  import org.apache.avalon.framework.component.ComponentException;
  import org.apache.avalon.framework.component.ComponentManager;
  import org.apache.avalon.framework.component.Composable;
  import org.apache.avalon.framework.configuration.Configurable;
  import org.apache.avalon.framework.configuration.Configuration;
  import org.apache.avalon.framework.configuration.ConfigurationException;
  import org.apache.avalon.framework.context.Context;
  import org.apache.avalon.framework.context.ContextException;
  import org.apache.avalon.framework.context.Contextualizable;
  import org.apache.avalon.framework.logger.AbstractLoggable;
  import org.apache.avalon.cornerstone.services.connection.ConnectionHandler;
  import org.apache.avalon.cornerstone.services.scheduler.PeriodicTimeTrigger;
  import org.apache.avalon.cornerstone.services.scheduler.Target;
  import org.apache.avalon.cornerstone.services.scheduler.TimeScheduler;
  import org.apache.james.*;
  import org.apache.james.core.*;
  import org.apache.james.services.MailServer;
  import org.apache.james.services.UsersRepository;
  import org.apache.james.services.UsersStore;
  import org.apache.james.util.*;
  import org.apache.mailet.*;
  
  /**
   * This handles an individual incoming message.  It handles regular SMTP
   * commands, and when it receives a message, adds it to the spool.
   * @author Serge Knystautas <sergek@lokitech.com>
   * @author Federico Barbieri <scoobie@systemy.it>
   * @author Jason Borden <jborden@javasense.com>
   * @version 0.9
   */
  public class SMTPHandler
      extends BaseConnectionHandler
      implements ConnectionHandler, Composable, Configurable, Target {
  
      public final static String SERVER_NAME = "SERVER_NAME";
      public final static String SERVER_TYPE = "SERVER_TYPE";
      public final static String REMOTE_NAME = "REMOTE_NAME";
      public final static String REMOTE_IP = "REMOTE_IP";
      public final static String NAME_GIVEN = "NAME_GIVEN";
      public final static String CURRENT_HELO_MODE = "CURRENT_HELO_MODE";
      public final static String SENDER = "SENDER_ADDRESS";
      public final static String RCPT_VECTOR = "RCPT_VECTOR";
      public final static String SMTP_ID = "SMTP_ID";
      public final static String AUTH = "AUTHENTICATED";
      public final static char[] SMTPTerminator = {'\r','\n','.','\r','\n'};
  
      private Socket socket;
      private DataInputStream in;
      private PrintWriter out;
  
      private String remoteHost;
      private String remoteHostGiven;
      private String remoteIP;
      private String messageID;
      private String smtpID;
  
      private boolean authRequired = false;
      private boolean verifyIdentity = false;
  
      private Configuration conf;
      private TimeScheduler scheduler;
      private UsersRepository users;
      private MailServer mailServer;
      private James parentJames;
  
      private String softwaretype = "JAMES SMTP Server " + Constants.SOFTWARE_VERSION;
      private static long count;
      private Hashtable state     = new Hashtable();
      private Random random       = new Random();
  
      public void configure ( Configuration configuration ) throws ConfigurationException
{
          super.configure(configuration);
          authRequired = configuration.getChild("authRequired").getValueAsBoolean(false);
          verifyIdentity = configuration.getChild("verifyIdentity").getValueAsBoolean(false);
      }
  
      public void compose( final ComponentManager componentManager )
          throws ComponentException {
          mailServer = (MailServer)componentManager.lookup("org.apache.james.services.MailServer");
          parentJames = (James)componentManager.lookup("org.apache.james.services.MailServer");
          scheduler = (TimeScheduler)componentManager.
              lookup("org.apache.avalon.cornerstone.services.scheduler.TimeScheduler");
          UsersStore usersStore = (UsersStore)componentManager.
              lookup( "org.apache.james.services.UsersStore" );
          users = usersStore.getRepository("LocalUsers");   
      }
  
      /**
       * Handle a connection.
       * This handler is responsible for processing connections as they occur.
       *
       * @param connection the connection
       * @exception IOException if an error reading from socket occurs
       * @exception ProtocolException if an error handling connection occurs
       */
      public void handleConnection( Socket connection )
          throws IOException {
          try {
              this.socket = connection;
              final InputStream bufferedInput =
                  new BufferedInputStream( socket.getInputStream(), 1024 );
              in = new DataInputStream( bufferedInput );
              out = new InternetPrintWriter(socket.getOutputStream(), true);
  
              remoteHost = socket.getInetAddress ().getHostName ();
              remoteIP = socket.getInetAddress ().getHostAddress ();
              smtpID = Math.abs(random.nextInt() % 1024) + "";
              state.clear();
              state.put(SERVER_NAME, this.helloName );
              state.put(SERVER_TYPE, this.softwaretype );
              state.put(REMOTE_NAME, remoteHost);
              state.put(REMOTE_IP, remoteIP);
              state.put(SMTP_ID, smtpID);
          } catch (Exception e) {
              getLogger().error("Cannot open connection from " + remoteHost + " (" + remoteIP
+ "): " + e.getMessage(), e );
              throw new RuntimeException("Cannot open connection from " + remoteHost + " ("
+ remoteIP + "): " + e.getMessage());
          }
  
          getLogger().info("Connection from " + remoteHost + " (" + remoteIP + ")");
  
          try {
              // Initially greet the connector
              // Format is:  Sat,  24 Jan 1998 13:16:09 -0500
  
              final PeriodicTimeTrigger trigger = new PeriodicTimeTrigger( timeout, -1 );
              scheduler.addTrigger( this.toString(), trigger, this );
              out.println("220 " + this.helloName + " SMTP Server (" + softwaretype + ") ready
" + RFC822DateFormat.toString(new Date()));
  
              while  (parseCommand(in.readLine())) {
                  scheduler.resetTrigger(this.toString());
              }
              socket.close();
              scheduler.removeTrigger(this.toString());
          } catch (SocketException se) {
              getLogger().debug("Socket to " + remoteHost + " closed remotely.", se );
          } catch ( InterruptedIOException iioe ) {
              getLogger().debug( "Socket to " + remoteHost + " timeout.", iioe );
          } catch ( IOException ioe ) {
              getLogger().debug( "Exception handling socket to " + remoteHost + ":"
                                 + ioe.getMessage(), ioe );
          } catch (Exception e) {
              getLogger().debug( "Exception opening socket: " + e.getMessage(), e );
          } finally {
              try {
                  socket.close();
              } catch (IOException e) {
                  getLogger().error("Exception closing socket: " + e.getMessage());
              }
          }
      }
  
      public void targetTriggered( final String triggerName ) {
          getLogger().error("Connection timeout on socket");
          try {
              out.println("Connection timeout. Closing connection");
              socket.close();
          } catch (IOException e) {
          }
      }
  
      private void resetState() {
          state.clear();
          state.put(SERVER_NAME, this.helloName );
          state.put(SERVER_TYPE, this.softwaretype );
          state.put(REMOTE_NAME, remoteHost);
          state.put(REMOTE_IP, remoteIP);
          state.put(SMTP_ID, smtpID);
      }
  
      private boolean parseCommand(String command)
          throws Exception {
  
          if (command == null) return false;
          getLogger().info("Command received: " + command);
          StringTokenizer commandLine = new StringTokenizer(command.trim(), " :");
          int arguments = commandLine.countTokens();
          if (arguments == 0) {
              return true;
          } else if(arguments > 0) {
              command = commandLine.nextToken();
          }
          String argument = (String) null;
          if(arguments > 1) {
              argument = commandLine.nextToken();
          }
          String argument1 = (String) null;
          if(arguments > 2) {
              argument1 = commandLine.nextToken();
          }
  
          if (command.equalsIgnoreCase("HELO"))
              doHELO(command,argument,argument1);
          else if (command.equalsIgnoreCase("EHLO"))
              doEHLO(command,argument,argument1);
          else if (command.equalsIgnoreCase("AUTH"))
              doAUTH(command,argument,argument1);        
          else if (command.equalsIgnoreCase("MAIL"))
              doMAIL(command,argument,argument1);
          else if (command.equalsIgnoreCase("RCPT"))
              doRCPT(command,argument,argument1);
          else if (command.equalsIgnoreCase("NOOP"))
              doNOOP(command,argument,argument1);
          else if (command.equalsIgnoreCase("RSET"))
              doRSET(command,argument,argument1);
          else if (command.equalsIgnoreCase("DATA"))
              doDATA(command,argument,argument1);
          else if (command.equalsIgnoreCase("QUIT"))
              doQUIT(command,argument,argument1);
          else
              doUnknownCmd(command,argument,argument1);
          return (command.equalsIgnoreCase("QUIT") == false);
      }
  
      private void doHELO(String command,String argument,String argument1) {
          if (state.containsKey(CURRENT_HELO_MODE)) {
              out.println("250 " + state.get(SERVER_NAME) + " Duplicate HELO/EHLO");
          } else if (argument == null) {
              out.println("501 domain address required: " + command);
          } else {
              state.put(CURRENT_HELO_MODE, command);
              state.put(NAME_GIVEN, argument);
              out.println(((authRequired) ? "250-AUTH LOGIN PLAIN\r\n" : "") + "250 " + state.get(SERVER_NAME)
+ " Hello " + argument +
                          " (" + state.get(REMOTE_NAME) +
                          " [" + state.get(REMOTE_IP) + "])");
          }
      }
      private void doEHLO(String command,String argument,String argument1) {
          doHELO(command,argument,argument1);
      }
  
      private void doAUTH(String command,String argument,String argument1) throws Exception
{
          if (state.containsKey(AUTH)) {
              out.println("503 User has previously authenticated. Further authentication is
not required!");
              return;        
          } else if (argument == null) {
              out.println("501 Usage: AUTH (authentication type) <challenge>");
              return;        
          } else if (argument.equalsIgnoreCase("PLAIN")) {
              String userpass, user, pass;
              StringTokenizer authTokenizer;
              if (argument1 == null) {
                  out.println("334 OK. Continue authentication");
                  userpass = in.readLine().trim();
              } else
                  userpass = argument1.trim();
              authTokenizer = new StringTokenizer(Base64.decode(userpass).readLine().trim(),
"\0");
              user = authTokenizer.nextToken();
              pass = authTokenizer.nextToken();
              // Authenticate user
              if (users.test(user, pass)) {
                  state.put(AUTH, user);
                  out.println("235 Authentication Successful");
                  getLogger().info("AUTH method PLAIN succeeded");
              } else {                
                  out.println("535 Authentication Failed");
                  getLogger().error("AUTH method PLAIN failed");
              }
              return;
          } else if (argument.equalsIgnoreCase("LOGIN")) {
              String user, pass;
  
              if (argument1 == null) {
                  out.println("334 VXNlcm5hbWU6"); // base64 encoded "Username:" String
                  user = in.readLine().trim();
              } else
                  user = argument1.trim();
              user = Base64.decode(user).readLine().trim();
              out.println("334 UGFzc3dvcmQ6"); // base64 encoded "Password:" String
              pass = Base64.decode(in.readLine().trim()).readLine().trim();
              //Authenticate user
              if (users.test(user, pass)) {
                  state.put(AUTH, user);
                  out.println("235 Authentication Successful");
                  getLogger().info("AUTH method LOGIN succeeded");
              } else {                
                  out.println("535 Authentication Failed");
                  getLogger().error("AUTH method LOGIN failed");
              }
              return;
          } else {
              out.println("504 Unrecognized Authentication Type");
              getLogger().error("AUTH method " + argument + " is an unrecognized authentication
type");
              return;
          }
      }
  
      private void doMAIL(String command,String argument,String argument1) {
          if (state.containsKey(SENDER)) {
              out.println("503 Sender already specified");
          } else if (argument == null || !argument.equalsIgnoreCase("FROM")
                     || argument1 == null) {
              out.println("501 Usage: MAIL FROM:<sender>");
          } else {
              String sender = argument1.trim();
              if (!sender.startsWith("<") || !sender.endsWith(">")) {
                  out.println("501 Syntax error in parameters or arguments");
                  getLogger().error("Error parsing sender address: " + sender
                                    + ": did not start and end with < >");
                  return;
              }
              MailAddress senderAddress = null;
              //Remove < and >
              sender = sender.substring(1, sender.length() - 1);
              try {
                  senderAddress = new MailAddress(sender);
              } catch (Exception pe) {
                  out.println("501 Syntax error in parameters or arguments");
                  getLogger().error("Error parsing sender address: " + sender
                                    + ": " + pe.getMessage());
                  return;
              }
              state.put(SENDER, senderAddress);
              out.println("250 Sender <" + sender + "> OK");
          }
      }
  
      private void doRCPT(String command,String argument,String argument1) {
          if (!state.containsKey(SENDER)) {
              out.println("503 Need MAIL before RCPT");
          } else if (argument == null || !argument.equalsIgnoreCase("TO") || argument1 ==
null) {
              out.println("501 Usage: RCPT TO:<recipient>");
          } else {
              Collection rcptColl = (Collection) state.get(RCPT_VECTOR);
              if (rcptColl == null) {
                  rcptColl = new Vector();
              }
              String recipient = argument1.trim();
              if (!recipient.startsWith("<") || !recipient.endsWith(">")) {
                  out.println("Syntax error in parameters or arguments");
                  getLogger().error("Error parsing recipient address: "
                                    + recipient
                                    + ": did not start and end with < >");
                  return;
              }
              MailAddress recipientAddress = null;
              //Remove < and >
              recipient = recipient.substring(1, recipient.length() - 1);
              try {
                  recipientAddress = new MailAddress(recipient);
              } catch (Exception pe) {
                  out.println("501 Syntax error in parameters or arguments");
                  getLogger().error("Error parsing recipient address: "
                                    + recipient + ": " + pe.getMessage());
                  return;
              }
              if (authRequired) {
                  // Make sure the mail is being sent locally if not authenticated else reject
                  if (!state.containsKey(AUTH)) {
                      String toDomain = recipient.substring(recipient.indexOf('@') + 1);
                      
                      if (!parentJames.isLocalServer(toDomain)) {
                          out.println("530 Authentication Required");
                          getLogger().error("Authentication is required for mail request");
                          return;
                      }
                  } else {                    
                      // Identity verification checking
                      if (verifyIdentity) {
                          String authUser = (String)state.get(AUTH);                     
          
                          MailAddress senderAddress = (MailAddress)state.get(SENDER);
                          boolean domainExists = false;
  
                          if (!authUser.equalsIgnoreCase(senderAddress.getUser())) {
                              out.println("503 Incorrect Authentication for Specified Email
Address");
                              getLogger().error("User " + authUser + " authenticated, however
tried sending email as " + senderAddress);
                              return;
                          }                        
                          if (!parentJames.isLocalServer(senderAddress.getHost())) {
                              out.println("503 Incorrect Authentication for Specified Email
Address");
                              getLogger().error("User " + authUser + " authenticated, however
tried sending email as " + senderAddress);
                              return;
                          }                                                        
                      }
                  }
              }
              rcptColl.add(recipientAddress);
              state.put(RCPT_VECTOR, rcptColl);
              out.println("250 Recipient <" + recipient + "> OK");
          }
      }
      private void doNOOP(String command,String argument,String argument1) {
          out.println("250 OK");
      }
      private void doRSET(String command,String argument,String argument1) {
          resetState();
          out.println("250 OK");
      }
  
      private void doDATA(String command,String argument,String argument1) {
          if (!state.containsKey(SENDER)) {
              out.println("503 No sender specified");
          } else if (!state.containsKey(RCPT_VECTOR)) {
              out.println("503 No recipients specified");
          } else {
              out.println("354 Ok Send data ending with <CRLF>.<CRLF>");
              try {
                  // parse headers
                  InputStream msgIn = new CharTerminatedInputStream(in, SMTPTerminator);
                  MailHeaders headers = new MailHeaders(msgIn);
                  // if headers do not contains minimum REQUIRED headers fields add them
                  if (!headers.isSet("Date")) {
                      headers.setHeader("Date", RFC822DateFormat.toString (new Date ()));
                  }
                  /*
                    We no longer add To as this in practice is not set (from what I've seen)
                    if (!headers.isSet("To")) {
                    headers.setHeader("To", );
                    }
                  */
                  if (!headers.isSet("From")) {
                      headers.setHeader("From", state.get(SENDER).toString());
                  }
  
                  String received = "from " + state.get(REMOTE_NAME) + " ([" + state.get(REMOTE_IP)
                      + "])\r\n          by " + this.helloName + " ("
                      + softwaretype + ") with SMTP ID " + state.get(SMTP_ID);
                  if (((Collection)state.get(RCPT_VECTOR)).size () == 1) {
                      //Only indicate a recipient if they're the only recipient
                      //(prevents email address harvesting and large headers in bulk email)
                      received += "\r\n          for <"
                          + ((Vector)state.get(RCPT_VECTOR)).elementAt(0).toString() + ">";
                  }
                  received += ";\r\n          " + RFC822DateFormat.toString (new Date ());
                  headers.addHeader ("Received", received);
  
                  // headers.setReceivedStamp("Unknown", (String) helloName.elementAt(0));
                  ByteArrayInputStream headersIn = new ByteArrayInputStream(headers.toByteArray());
                  MailImpl mail = new MailImpl(mailServer.getId(), (MailAddress)state.get(SENDER),
                                               (Vector)state.get(RCPT_VECTOR),
                                               new SequenceInputStream(headersIn, msgIn));
                  mail.setRemoteHost((String)state.get(REMOTE_NAME));
                  mail.setRemoteAddr((String)state.get(REMOTE_IP));
                  mailServer.sendMail(mail);
              } catch (MessagingException me) {
                  out.println("451 Error processing message: " + me.getMessage());
                  getLogger().error("Error processing message: "
                                    + me.getMessage());
                  return;
              }
              getLogger().info("Mail sent to Mail Server");
              resetState();
              out.println("250 Message received");
          }
      }
      private void doQUIT(String command,String argument,String argument1) {
          out.println("221 " + state.get(SERVER_NAME) + " Service closing transmission channel");
      }
  
      private void doUnknownCmd(String command,String argument,String argument1) {
          out.println("500 " + state.get(SERVER_NAME) + " Syntax error, command unrecognized:
" +
                      command);
      }
  }
  
  
  
  1.1                  jakarta-james/proposals/v1.3/java/org/apache/james/util/Base64.java
  
  Index: Base64.java
  ===================================================================
  /*
   * Copyright (C) The Apache Software Foundation. All rights reserved.
   *
   * This software is published under the terms of the Apache Software License
   * version 1.1, a copy of which has been included with this distribution in
   * the LICENSE file.
   */
  package org.apache.james.util;
  
  import java.io.*;
  import javax.mail.internet.*;
  
  /**
   * Simple Base64 string decoding function
   * @author Jason Borden <jborden@javasense.com>  
   */
  
  public class Base64 {
  
      public static BufferedReader decode(String b64string) throws Exception {
          return new BufferedReader(new InputStreamReader(MimeUtility.decode(new ByteArrayInputStream(b64string.getBytes()),
"base64")));
      }
  }
  
  
  
  1.1                  jakarta-james/proposals/v1.3/www/rfclist/README
  
  Index: README
  ===================================================================
  This Document contains references to relevant RFCs and Drafts.
  
  Basic RFC
  ---------
  RFC 822: Mail Message Format
  
  SMTP
  ----
  RFC 2554: SMTP Service Extension for Authentication
  
  POP3
  ----
  
  IMAP
  ----
  
  NNTP
  ----
  RFC 977 : NNTP Protocol.
  draft-ietf-nntpext-base-13.txt: Latest draft of NNTP protocol
  RFC 2980: Common NNTP Extensions
  RFC 1036: Format of News Messages
  NNTP Working group: http://www.academ.com/academ/nntp/
  
  LDAP
  ----
  
  
  
  1.1                  jakarta-james/proposals/v1.3/www/rfclist/rfc2554.txt
  
  Index: rfc2554.txt
  ===================================================================
  
  
  
  
  
  
  Network Working Group                                           J. Myers
  Request for Comments: 2554                       Netscape Communications
  Category: Standards Track                                     March 1999
  
  
                           SMTP Service Extension
                             for Authentication
  
  Status of this Memo
  
     This document specifies an Internet standards track protocol for the
     Internet community, and requests discussion and suggestions for
     improvements.  Please refer to the current edition of the "Internet
     Official Protocol Standards" (STD 1) for the standardization state
     and status of this protocol.  Distribution of this memo is unlimited.
  
  Copyright Notice
  
     Copyright (C) The Internet Society (1999).  All Rights Reserved.
  
  
  1. Introduction
  
     This document defines an SMTP service extension [ESMTP] whereby an
     SMTP client may indicate an authentication mechanism to the server,
     perform an authentication protocol exchange, and optionally negotiate
     a security layer for subsequent protocol interactions.  This
     extension is a profile of the Simple Authentication and Security
     Layer [SASL].
  
  
  2. Conventions Used in this Document
  
     In examples, "C:" and "S:" indicate lines sent by the client and
     server respectively.
  
     The key words "MUST", "MUST NOT", "SHOULD", "SHOULD NOT", and "MAY"
     in this document are to be interpreted as defined in "Key words for
     use in RFCs to Indicate Requirement Levels" [KEYWORDS].
  
  
  3. The Authentication service extension
  
  
     (1) the name of the SMTP service extension is "Authentication"
  
     (2) the EHLO keyword value associated with this extension is "AUTH"
  
  
  
  
  Myers                       Standards Track                     [Page 1]
  
  RFC 2554                  SMTP Authentication                 March 1999
  
  
     (3) The AUTH EHLO keyword contains as a parameter a space separated
         list of the names of supported SASL mechanisms.
  
     (4) a new SMTP verb "AUTH" is defined
  
     (5) an optional parameter using the keyword "AUTH" is added to the
         MAIL FROM command, and extends the maximum line length of the
         MAIL FROM command by 500 characters.
  
     (6) this extension is appropriate for the submission protocol
         [SUBMIT].
  
  
  4. The AUTH command
  
     AUTH mechanism [initial-response]
  
       Arguments:
           a string identifying a SASL authentication mechanism.
           an optional base64-encoded response
  
       Restrictions:
           After an AUTH command has successfully completed, no more AUTH
           commands may be issued in the same session.  After a successful
           AUTH command completes, a server MUST reject any further AUTH
           commands with a 503 reply.
  
           The AUTH command is not permitted during a mail transaction.
  
       Discussion:
           The AUTH command indicates an authentication mechanism to the
           server.  If the server supports the requested authentication
           mechanism, it performs an authentication protocol exchange to
           authenticate and identify the user.  Optionally, it also
           negotiates a security layer for subsequent protocol
           interactions.  If the requested authentication mechanism is not
           supported, the server rejects the AUTH command with a 504
           reply.
  
           The authentication protocol exchange consists of a series of
           server challenges and client answers that are specific to the
           authentication mechanism.  A server challenge, otherwise known
           as a ready response, is a 334 reply with the text part
           containing a BASE64 encoded string.  The client answer consists
           of a line containing a BASE64 encoded string.  If the client
           wishes to cancel an authentication exchange, it issues a line
           with a single "*".  If the server receives such an answer, it
           MUST reject the AUTH command by sending a 501 reply.
  
  
  
  Myers                       Standards Track                     [Page 2]
  
  RFC 2554                  SMTP Authentication                 March 1999
  
  
           The optional initial-response argument to the AUTH command is
           used to save a round trip when using authentication mechanisms
           that are defined to send no data in the initial challenge.
           When the initial-response argument is used with such a
           mechanism, the initial empty challenge is not sent to the
           client and the server uses the data in the initial-response
           argument as if it were sent in response to the empty challenge.
           Unlike a zero-length client answer to a 334 reply, a zero-
           length initial response is sent as a single equals sign ("=").
           If the client uses an initial-response argument to the AUTH
           command with a mechanism that sends data in the initial
           challenge, the server rejects the AUTH command with a 535
           reply.
  
           If the server cannot BASE64 decode the argument, it rejects the
           AUTH command with a 501 reply.  If the server rejects the
           authentication data, it SHOULD reject the AUTH command with a
           535 reply unless a more specific error code, such as one listed
           in section 6, is appropriate.  Should the client successfully
           complete the authentication exchange, the SMTP server issues a
           235 reply.
  
           The service name specified by this protocol's profile of SASL
           is "smtp".
  
           If a security layer is negotiated through the SASL
           authentication exchange, it takes effect immediately following
           the CRLF that concludes the authentication exchange for the
           client, and the CRLF of the success reply for the server.  Upon
           a security layer's taking effect, the SMTP protocol is reset to
           the initial state (the state in SMTP after a server issues a
           220 service ready greeting).  The server MUST discard any
           knowledge obtained from the client, such as the argument to the
           EHLO command, which was not obtained from the SASL negotiation
           itself.  The client MUST discard any knowledge obtained from
           the server, such as the list of SMTP service extensions, which
           was not obtained from the SASL negotiation itself (with the
           exception that a client MAY compare the list of advertised SASL
           mechanisms before and after authentication in order to detect
           an active down-negotiation attack).  The client SHOULD send an
           EHLO command as the first command after a successful SASL
           negotiation which results in the enabling of a security layer.
  
           The server is not required to support any particular
           authentication mechanism, nor are authentication mechanisms
           required to support any security layers.  If an AUTH command
           fails, the client may try another authentication mechanism by
           issuing another AUTH command.
  
  
  
  Myers                       Standards Track                     [Page 3]
  
  RFC 2554                  SMTP Authentication                 March 1999
  
  
           If an AUTH command fails, the server MUST behave the same as if
           the client had not issued the AUTH command.
  
           The BASE64 string may in general be arbitrarily long.  Clients
           and servers MUST be able to support challenges and responses
           that are as long as are generated by the authentication
           mechanisms they support, independent of any line length
           limitations the client or server may have in other parts of its
           protocol implementation.
  
       Examples:
           S: 220 smtp.example.com ESMTP server ready
           C: EHLO jgm.example.com
           S: 250-smtp.example.com
           S: 250 AUTH CRAM-MD5 DIGEST-MD5
           C: AUTH FOOBAR
           S: 504 Unrecognized authentication type.
           C: AUTH CRAM-MD5
           S: 334
           PENCeUxFREJoU0NnbmhNWitOMjNGNndAZWx3b29kLmlubm9zb2Z0LmNvbT4=
           C: ZnJlZCA5ZTk1YWVlMDljNDBhZjJiODRhMGMyYjNiYmFlNzg2ZQ==
           S: 235 Authentication successful.
  
  
  
  5. The AUTH parameter to the MAIL FROM command
  
     AUTH=addr-spec
  
     Arguments:
         An addr-spec containing the identity which submitted the message
         to the delivery system, or the two character sequence "<>"
         indicating such an identity is unknown or insufficiently
         authenticated.  To comply with the restrictions imposed on ESMTP
         parameters, the addr-spec is encoded inside an xtext.  The syntax
         of an xtext is described in section 5 of [ESMTP-DSN].
  
     Discussion:
         The optional AUTH parameter to the MAIL FROM command allows
         cooperating agents in a trusted environment to communicate the
         authentication of individual messages.
  
         If the server trusts the authenticated identity of the client to
         assert that the message was originally submitted by the supplied
         addr-spec, then the server SHOULD supply the same addr-spec in an
         AUTH parameter when relaying the message to any server which
         supports the AUTH extension.
  
  
  
  
  Myers                       Standards Track                     [Page 4]
  
  RFC 2554                  SMTP Authentication                 March 1999
  
  
         A MAIL FROM parameter of AUTH=<> indicates that the original
         submitter of the message is not known.  The server MUST NOT treat
         the message as having been originally submitted by the client.
  
         If the AUTH parameter to the MAIL FROM is not supplied, the
         client has authenticated, and the server believes the message is
         an original submission by the client, the server MAY supply the
         client's identity in the addr-spec in an AUTH parameter when
         relaying the message to any server which supports the AUTH
         extension.
  
         If the server does not sufficiently trust the authenticated
         identity of the client, or if the client is not authenticated,
         then the server MUST behave as if the AUTH=<> parameter was
         supplied.  The server MAY, however, write the value of the AUTH
         parameter to a log file.
  
         If an AUTH=<> parameter was supplied, either explicitly or due to
         the requirement in the previous paragraph, then the server MUST
         supply the AUTH=<> parameter when relaying the message to any
         server which it has authenticated to using the AUTH extension.
  
         A server MAY treat expansion of a mailing list as a new
         submission, setting the AUTH parameter to the mailing list
         address or mailing list administration address when relaying the
         message to list subscribers.
  
         It is conforming for an implementation to be hard-coded to treat
         all clients as being insufficiently trusted.  In that case, the
         implementation does nothing more than parse and discard
         syntactically valid AUTH parameters to the MAIL FROM command and
         supply AUTH=<> parameters to any servers to which it
         authenticates using the AUTH extension.
  
     Examples:
         C: MAIL FROM:<e=mc2@example.com> AUTH=e+3Dmc2@example.com
         S: 250 OK
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  Myers                       Standards Track                     [Page 5]
  
  RFC 2554                  SMTP Authentication                 March 1999
  
  
  6. Error Codes
  
     The following error codes may be used to indicate various conditions
     as described.
  
     432 A password transition is needed
  
     This response to the AUTH command indicates that the user needs to
     transition to the selected authentication mechanism.  This typically
     done by authenticating once using the PLAIN authentication mechanism.
  
     534 Authentication mechanism is too weak
  
     This response to the AUTH command indicates that the selected
     authentication mechanism is weaker than server policy permits for
     that user.
  
     538 Encryption required for requested authentication mechanism
  
     This response to the AUTH command indicates that the selected
     authentication mechanism may only be used when the underlying SMTP
     connection is encrypted.
  
     454 Temporary authentication failure
  
     This response to the AUTH command indicates that the authentication
     failed due to a temporary server failure.
  
     530 Authentication required
  
     This response may be returned by any command other than AUTH, EHLO,
     HELO, NOOP, RSET, or QUIT.  It indicates that server policy requires
     authentication in order to perform the requested action.
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  Myers                       Standards Track                     [Page 6]
  
  RFC 2554                  SMTP Authentication                 March 1999
  
  
  7. Formal Syntax
  
     The following syntax specification uses the augmented Backus-Naur
     Form (BNF) notation as specified in [ABNF].
  
     Except as noted otherwise, all alphabetic characters are case-
     insensitive.  The use of upper or lower case characters to define
     token strings is for editorial clarity only.  Implementations MUST
     accept these strings in a case-insensitive fashion.
  
     UPALPHA         = %x41-5A            ;; Uppercase: A-Z
  
     LOALPHA         = %x61-7A            ;; Lowercase: a-z
  
     ALPHA           = UPALPHA / LOALPHA  ;; case insensitive
  
     DIGIT           = %x30-39            ;; Digits 0-9
  
     HEXDIGIT        = %x41-46 / DIGIT    ;; hexidecimal digit (uppercase)
  
     hexchar         = "+" HEXDIGIT HEXDIGIT
  
     xchar           = %x21-2A / %x2C-3C / %x3E-7E
                       ;; US-ASCII except for "+", "=", SPACE and CTL
  
     xtext           = *(xchar / hexchar)
  
     AUTH_CHAR       = ALPHA / DIGIT / "-" / "_"
  
     auth_type       = 1*20AUTH_CHAR
  
     auth_command    = "AUTH" SPACE auth_type [SPACE (base64 / "=")]
                       *(CRLF [base64]) CRLF
  
     auth_param      = "AUTH=" xtext
                         ;; The decoded form of the xtext MUST be either
                         ;; an addr-spec or the two characters "<>"
  
     base64          = base64_terminal /
                       ( 1*(4base64_CHAR) [base64_terminal] )
  
     base64_char     = UPALPHA / LOALPHA / DIGIT / "+" / "/"
                       ;; Case-sensitive
  
     base64_terminal = (2base64_char "==") / (3base64_char "=")
  
     continue_req    = "334" SPACE [base64] CRLF
  
  
  
  
  Myers                       Standards Track                     [Page 7]
  
  RFC 2554                  SMTP Authentication                 March 1999
  
  
     CR              = %x0C           ;; ASCII CR, carriage return
  
     CRLF            = CR LF
  
     CTL             = %x00-1F / %x7F ;; any ASCII control character and DEL
  
     LF              = %x0A           ;; ASCII LF, line feed
  
     SPACE           = %x20           ;; ASCII SP, space
  
  
  
  
  8. References
  
     [ABNF]      Crocker, D. and P. Overell, "Augmented BNF for Syntax
                 Specifications: ABNF", RFC 2234, November 1997.
  
     [CRAM-MD5]  Klensin, J., Catoe, R. and P. Krumviede, "IMAP/POP
                 AUTHorize Extension for Simple Challenge/Response", RFC
                 2195, September 1997.
  
     [ESMTP]     Klensin, J., Freed, N., Rose, M., Stefferud, E. and D.
                 Crocker, "SMTP Service Extensions", RFC 1869, November
                 1995.
  
     [ESMTP-DSN] Moore, K, "SMTP Service Extension for Delivery Status
                 Notifications", RFC 1891, January 1996.
  
     [KEYWORDS]  Bradner, S., "Key words for use in RFCs to Indicate
                 Requirement Levels", BCP 14, RFC 2119, March 1997.
  
     [SASL]      Myers, J., "Simple Authentication and Security Layer
                 (SASL)", RFC 2222, October 1997.
  
     [SUBMIT]    Gellens, R. and J. Klensin, "Message Submission", RFC
                 2476, December 1998.
  
     [RFC821]    Postel, J., "Simple Mail Transfer Protocol", STD 10, RFC
                 821, August 1982.
  
     [RFC822]    Crocker, D., "Standard for the Format of ARPA Internet
                 Text Messages", STD 11, RFC 822, August 1982.
  
  
  
  
  
  
  
  
  Myers                       Standards Track                     [Page 8]
  
  RFC 2554                  SMTP Authentication                 March 1999
  
  
  9. Security Considerations
  
     Security issues are discussed throughout this memo.
  
     If a client uses this extension to get an encrypted tunnel through an
     insecure network to a cooperating server, it needs to be configured
     to never send mail to that server when the connection is not mutually
     authenticated and encrypted.  Otherwise, an attacker could steal the
     client's mail by hijacking the SMTP connection and either pretending
     the server does not support the Authentication extension or causing
     all AUTH commands to fail.
  
     Before the SASL negotiation has begun, any protocol interactions are
     performed in the clear and may be modified by an active attacker.
     For this reason, clients and servers MUST discard any knowledge
     obtained prior to the start of the SASL negotiation upon completion
     of a SASL negotiation which results in a security layer.
  
     This mechanism does not protect the TCP port, so an active attacker
     may redirect a relay connection attempt to the submission port
     [SUBMIT].  The AUTH=<> parameter prevents such an attack from causing
     an relayed message without an envelope authentication to pick up the
     authentication of the relay client.
  
     A message submission client may require the user to authenticate
     whenever a suitable SASL mechanism is advertised.  Therefore, it may
     not be desirable for a submission server [SUBMIT] to advertise a SASL
     mechanism when use of that mechanism grants the client no benefits
     over anonymous submission.
  
     This extension is not intended to replace or be used instead of end-
     to-end message signature and encryption systems such as S/MIME or
     PGP.  This extension addresses a different problem than end-to-end
     systems; it has the following key differences:
  
        (1) it is generally useful only within a trusted enclave
  
        (2) it protects the entire envelope of a message, not just the
            message's body.
  
        (3) it authenticates the message submission, not authorship of the
            message content
  
        (4) it can give the sender some assurance the message was
            delivered to the next hop in the case where the sender
            mutually authenticates with the next hop and negotiates an
            appropriate security layer.
  
  
  
  
  Myers                       Standards Track                     [Page 9]
  
  RFC 2554                  SMTP Authentication                 March 1999
  
  
     Additional security considerations are mentioned in the SASL
     specification [SASL].
  
  
  
  10. Author's Address
  
     John Gardiner Myers
     Netscape Communications
     501 East Middlefield Road
     Mail Stop MV-029
     Mountain View, CA 94043
  
     EMail: jgmyers@netscape.com
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  Myers                       Standards Track                    [Page 10]
  
  RFC 2554                  SMTP Authentication                 March 1999
  
  
  11.  Full Copyright Statement
  
     Copyright (C) The Internet Society (1999).  All Rights Reserved.
  
     This document and translations of it may be copied and furnished to
     others, and derivative works that comment on or otherwise explain it
     or assist in its implementation may be prepared, copied, published
     and distributed, in whole or in part, without restriction of any
     kind, provided that the above copyright notice and this paragraph are
     included on all such copies and derivative works.  However, this
     document itself may not be modified in any way, such as by removing
     the copyright notice or references to the Internet Society or other
     Internet organizations, except as needed for the purpose of
     developing Internet standards in which case the procedures for
     copyrights defined in the Internet Standards process must be
     followed, or as required to translate it into languages other than
     English.
  
     The limited permissions granted above are perpetual and will not be
     revoked by the Internet Society or its successors or assigns.
  
     This document and the information contained herein is provided on an
     "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
     TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
     BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
     HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
     MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  Myers                       Standards Track                    [Page 11]
  
  
  
  
  

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