


smtpd(n)             Tcl SMTP Server Package             smtpd(n)


______________________________________________________________________________

NAME
       smtpd - Tcl SMTP server implementation

SYNOPSIS
       package require Tcl  8.3

       package require smtpd  ?1.4?

       ::smtpd::start ?myaddr? ?port?

       ::smtpd::stop

       ::smptd::configure ?option value? ?option value ...?

       ::smtpd::cget ?option?

_________________________________________________________________

DESCRIPTION
       The  smtpd  package  provides  a simple Tcl-only server library for the
       Simple Mail Transfer Protocol as described in RFC  821 (http://www.rfc-
       editor.org/rfc/rfc821.txt)    and    RFC    2821   (http://www.rfc-edi-
       tor.org/rfc/rfc2821.txt).  By default  the  server  will  bind  to  the
       default network address and the standard SMTP port (25).

       This  package  was  designed  to permit testing of Mail User Agent code
       from a developers workstation. It does not attempt to deliver  mail  to
       your  mailbox.  Instead  users  of this package are expected to write a
       procedure that will be called when mail arrives.  Once  this  procedure
       returns, the server has nothing further to do with the mail.

SECURITY
       On  Unix platforms binding to the SMTP port requires root privileges. I
       would not recommend running any  script-based  server  as  root  unless
       there is some method for dropping root privileges immediately after the
       socket is bound. Under Windows platforms, it is not necessary  to  have
       root or administrator privileges to bind low numbered sockets. However,
       security on these platforms is weak anyway.

       In short, this code should probably not be used as a  permanently  run-
       ning  Mail  Transfer Agent on an Internet connected server, even though
       we are careful not to evaluate remote user input. There are many  other
       well  tested  and  security  audited  programs that can be used as mail
       servers for internet connected hosts.

COMMANDS
       ::smtpd::start ?myaddr? ?port?
              Start the service listening on port or the default port  25.  If
              myaddr  is given as a domain-style name or numerical dotted-quad
              IP address then the server socket will be bound to that  network
              interface.  By default the server is bound to all network inter-
              faces. For example:



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smtpd(n)             Tcl SMTP Server Package             smtpd(n)


                set sock [::smtpd::start [info hostname] 0]


              will bind to the hosts internet interface on the first available
              port.

              At present the package only supports a single instance of a SMTP
              server. This could be changed if required at the cost of  making
              the  package  a  little  more complicated to read. If there is a
              good reason for running multiple SMTP services then it will only
              be  necessary  to fix the options array and the ::smtpd::stopped
              variable usage.

              As the server code uses fileevent(n)  handlers  to  process  the
              input on sockets you will need to run the event loop. This means
              either you should be running from within wish(1) or  you  should
              vwait(n)  on the ::smtpd::stopped variable which is set when the
              server is stopped.

       ::smtpd::stop
              Halt the server and release the listening socket. If the  server
              has  not  been  started  then  this  command  does nothing.  The
              ::smtpd::stopped variable is set for use with vwait(n).

              It should be noted that stopping the server does not  disconnect
              any  currently  active  sessions  as these are operating over an
              independent channel. Only explicitly tracking and closing  these
              sessions,  or exiting the server process will close down all the
              running sessions. This is similar to the usual unix daemon prac-
              tice  where the server performs a fork(2) and the client session
              continues on the child process.

       ::smptd::configure ?option value? ?option value ...?
              Set configuration options for the SMTP server. Most  values  are
              the  name of a callback procedure to be called at various points
              in the SMTP protocol. See the CALLBACKS section for  details  of
              the procedures.

              -validate_host proc
                     Callback to authenticate new connections based on the ip-
                     address of the client.

              -validate_sender proc
                     Callback to authenticate new  connections  based  on  the
                     senders email address.

              -validate_recipient proc
                     Callback  to  validate  and  authorize  a recipient email
                     address

              -deliverMIME proc
                     Callback used to deliver mail as a mime token created  by
                     the tcllib mime package.




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smtpd(n)             Tcl SMTP Server Package             smtpd(n)


              -deliver proc
                     Callback used to deliver email. This option has no effect
                     if the -deliverMIME option has been set.

       ::smtpd::cget ?option?
              If no option is specified the command will return a list of  all
              options  and  their current values. If an option is specified it
              will return the value of that option.


CALLBACKS
       validate_host callback
              This procedure is called with the clients ip address as soon  as
              a  connection  request has been accepted and before any protocol
              commands are processed. If you wish to deny access to a specific
              host  then  an  error  should  be returned by this callback. For
              example:


               proc validate_host {ipnum} {
                  if {[string match "192.168.1.*" $ipnum]} {
                     error "go away!"
                  }
               }


              If access is denied the client will receive a  standard  message
              that includes the text of your error, such as:


               550 Access denied: I hate you.


              As  per  the  SMTP protocol, the connection is not closed but we
              wait for the client to send a QUIT command. Any  other  commands
              cause a 503 Bad Sequence error.

       validate_sender callback
              The  validate_sender  callback  is  called with the senders mail
              address during processing of a MAIL  command  to  allow  you  to
              accept  or reject mail based upon the declared sender. To reject
              mail you should throw an error. For example, to reject mail from
              user "denied":


               proc validate_sender {address} {
                  eval array set addr [mime::parseaddress $address]
                  if {[string match "denied" $addr(local)]} {
                       error "mailbox $addr(local) denied"
                  }
                  return
               }





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smtpd(n)             Tcl SMTP Server Package             smtpd(n)


              The  content of any error message will not be passed back to the
              client.

       validate_recipient callback
              The  validate_recipient  callback  is  similar  to   the   vali-
              date_sender  callback  and permits you to verify a local mailbox
              and accept mail for a local user  address  during  RCPT  command
              handling.  To  reject  mail,  throw an error as above. The error
              message is ignored.

       deliverMIME callback
              ] The deliverMIME callback is called once  a  mail  message  has
              been  successfully  passed  to  the server. A mime token is con-
              structed from the sender, recipients and data and the users pro-
              cedure  it  called  with  this  single  argument.  When the call
              returns, the mime token is cleaned up so if the user  wishes  to
              preserve the data she must make a copy.


               proc deliverMIME {token} {
                   set sender [lindex [mime::getheader $token From] 0]
                   set recipients [lindex [mime::getheader $token To] 0]
                   set mail "From $sender [clock format [clock seconds]]"
                   append mail "\n" [mime::buildmessage $token]
                   puts $mail
               }


       deliver callback
              The deliver callback is called once a mail message has been suc-
              cessfully passed to the server  and  there  is  no  -deliverMIME
              option  set.  The procedure is called with the sender, a list of
              recipients and the text of the mail as  a  list  of  lines.  For
              example:


               proc deliver {sender recipients data} {
                  set mail "From $sender  [clock format [clock seconds]]"
                  append mail "\n" [join $data "\n"]
                  puts "$mail"
               }


              Note  that the DATA command will return an error if no sender or
              recipient has yet been defined.


VARIABLES
       ::smtpd::stopped
              This variable is set to true during the ::smtpd::stop command to
              permit the use of the vwait(n) command.






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smtpd(n)             Tcl SMTP Server Package             smtpd(n)


AUTHOR
       Written by Pat Thoyts mailto:patthoyts@users.sourceforge.net.

LICENSE
       This  software  is  distributed in the hope that it will be useful, but
       WITHOUT ANY  WARRANTY;  without  even  the  implied  warranty  of  MER-
       CHANTABILITY  or  FITNESS  FOR  A  PARTICULAR  PURPOSE.  See  the  file
       "license.terms" for more details.

BUGS, IDEAS, FEEDBACK
       This document, and the package it describes, will  undoubtedly  contain
       bugs  and  other problems.  Please report such in the category smtpd of
       the         Tcllib         SF         Trackers          [http://source-
       forge.net/tracker/?group_id=12883].   Please  also report any ideas for
       enhancements you may have for either package and/or documentation.

KEYWORDS
       rfc 2821, rfc 821, services, smtp, smtpd, socket, vwait

CATEGORY
       Networking

COPYRIGHT
       Copyright (c) Pat Thoyts <patthoyts@users.sourceforge.net>

































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