'\"
'\" Generated from file 'smtpd\&.man' by tcllib/doctools with format 'nroff'
'\" Copyright (c) Pat Thoyts <patthoyts@users\&.sourceforge\&.net>
'\"
.TH "smtpd" n 1\&.6 tcllib "Tcl SMTP Server Package"
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.BS
.SH NAME
smtpd \- Tcl SMTP server implementation
.SH SYNOPSIS
package require \fBTcl 8\&.5 9\fR
.sp
package require \fBsmtpd ?1\&.6?\fR
.sp
\fB::smtpd::start\fR ?\fImyaddr\fR? ?\fIport\fR?
.sp
\fB::smtpd::stop\fR
.sp
\fB::smptd::configure\fR ?\fIoption\fR \fIvalue\fR? ?\fIoption\fR \fIvalue\fR \fI\&.\&.\&.\fR?
.sp
\fB::smtpd::cget\fR ?\fIoption\fR?
.sp
.BE
.SH DESCRIPTION
.PP
The \fBsmtpd\fR package provides a simple Tcl-only server library
for the Simple Mail Transfer Protocol as described in
RFC  821 (\fIhttp://www\&.rfc-editor\&.org/rfc/rfc821\&.txt\fR) and
RFC 2821 (\fIhttp://www\&.rfc-editor\&.org/rfc/rfc2821\&.txt\fR)\&.
By default the server will bind to the default network address and the
standard SMTP port (25)\&.
.PP
This package was designed to permit testing of Mail User Agent code
from a developers workstation\&. \fIIt does not attempt to deliver  mail to your mailbox\&.\fR 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\&.
.SH 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\&.
.PP
In short, this code should probably not be used as a permanently
running 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\&.
.SH "TLS SECURITY CONSIDERATIONS"
.PP
This package uses the \fBTLS\fR package to handle the
security for \fBhttps\fR urls and other socket connections\&.
.PP
Policy decisions like the set of protocols to support and what
ciphers to use are not the responsibility of \fBTLS\fR, nor of
this package itself however\&.
Such decisions are the responsibility of whichever application is
using the package, and are likely influenced by the set of servers
the application will talk to as well\&.
.PP
For example, in light of the recent
\fIPOODLE attack\fR [http://googleonlinesecurity\&.blogspot\&.co\&.uk/2014/10/this-poodle-bites-exploiting-ssl-30\&.html] discovered by Google many servers will disable support
for the SSLv3 protocol\&.
To handle this change the applications using \fBTLS\fR must be
patched, and not this package, nor \fBTLS\fR itself\&.
Such a patch may be as simple as generally activating \fBtls1\fR
support, as shown in the example below\&.
.CS


    package require tls
    tls::init -tls1 1 ;# forcibly activate support for the TLS1 protocol

    \&.\&.\&. your own application code \&.\&.\&.

.CE
.SH COMMANDS
.TP
\fB::smtpd::start\fR ?\fImyaddr\fR? ?\fIport\fR?
Start the service listening on \fIport\fR or the default port 25\&. If
\fImyaddr\fR 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
interfaces\&. For example:
.sp
.CS


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

.CE
.sp
will bind to the hosts internet interface on the first available port\&.
.sp
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 \fBoptions\fR array and the \fB::smtpd::stopped\fR variable
usage\&.
.sp
As the server code uses \fBfileevent\fR(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 \fBwish\fR(1) or you
should \fBvwait\fR(n) on the \fB::smtpd::stopped\fR variable which is
set when the server is stopped\&.
.TP
\fB::smtpd::stop\fR
Halt the server and release the listening socket\&. If the server has
not been started then this command does nothing\&.
The \fB::smtpd::stopped\fR variable is set for use with
\fBvwait\fR(n)\&.
.sp
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 practice where the
server performs a \fBfork\fR(2) and the client session continues on
the child process\&.
.TP
\fB::smptd::configure\fR ?\fIoption\fR \fIvalue\fR? ?\fIoption\fR \fIvalue\fR \fI\&.\&.\&.\fR?
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 \fBCALLBACKS\fR section for details of the
procedures\&.
.RS
.TP
\fB-banner\fR \fItext\fR
Text of a custom banner message\&. The default banner is "tcllib smtpd 1\&.6"\&.
Note that changing the banner does not affect the bracketing text
in the full greeting, printing status 220, server-address, and timestamp\&.
.TP
\fB-validate_host\fR \fIproc\fR
Callback to authenticate new connections based on the ip-address of
the client\&.
.TP
\fB-validate_sender\fR \fIproc\fR
Callback to authenticate new connections based on the senders email
address\&.
.TP
\fB-validate_recipient\fR \fIproc\fR
Callback to validate and authorize a recipient email address
.TP
\fB-deliverMIME\fR \fIproc\fR
Callback used to deliver mail as a mime token created by the tcllib
\fBmime\fR package\&.
.TP
\fB-deliver\fR \fIproc\fR
Callback used to deliver email\&. This option has no effect if
the \fB-deliverMIME\fR option has been set\&.
.RE
.TP
\fB::smtpd::cget\fR ?\fIoption\fR?
If no \fIoption\fR 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\&.
.PP
.SH CALLBACKS
.TP
\fBvalidate_host\fR 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:
.sp
.CS


 proc validate_host {ipnum} {
    if {[string match "192\&.168\&.1\&.*" $ipnum]} {
       error "go away!"
    }
 }

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


 550 Access denied: I hate you\&.

.CE
.sp
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
\fB503 Bad Sequence\fR error\&.
.TP
\fBvalidate_sender\fR 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":
.sp
.CS


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

.CE
.sp
The content of any error message will not be passed back to the client\&.
.TP
\fBvalidate_recipient\fR callback
The validate_recipient callback is similar to the validate_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\&.
.TP
\fBdeliverMIME\fR callback
The deliverMIME callback is called once a mail message has been
successfully passed to the server\&. A mime token is constructed from
the sender, recipients and data and the users procedure 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\&.
.sp
.CS


 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
 }

.CE
.TP
\fBdeliver\fR callback
The deliver callback is called once a mail message has been
successfully 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:
.sp
.CS


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

.CE
.sp
Note that the DATA command will return an error if no sender or
recipient has yet been defined\&.
.PP
.SH VARIABLES
.TP
\fB::smtpd::stopped\fR
This variable is set to \fBtrue\fR during the \fB::smtpd::stop\fR
command to permit the use of the \fBvwait\fR(n) command\&.
.PP
.SH AUTHOR
Written by Pat Thoyts \fImailto:patthoyts@users\&.sourceforge\&.net\fR\&.
.SH LICENSE
This software is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE\&. See the file
"\fIlicense\&.terms\fR" for more details\&.
.SH "BUGS, IDEAS, FEEDBACK"
This document, and the package it describes, will undoubtedly contain
bugs and other problems\&.
Please report such in the category \fIsmtpd\fR of the
\fITcllib Trackers\fR [http://core\&.tcl\&.tk/tcllib/reportlist]\&.
Please also report any ideas for enhancements you may have for either
package and/or documentation\&.
.PP
When proposing code changes, please provide \fIunified diffs\fR,
i\&.e the output of \fBdiff -u\fR\&.
.PP
Note further that \fIattachments\fR are strongly preferred over
inlined patches\&. Attachments can be made by going to the \fBEdit\fR
form of the ticket immediately after its creation, and then using the
left-most button in the secondary navigation bar\&.
.SH KEYWORDS
rfc 2821, rfc 821, services, smtp, smtpd, socket, vwait
.SH CATEGORY
Networking
.SH COPYRIGHT
.nf
Copyright (c) Pat Thoyts <patthoyts@users\&.sourceforge\&.net>

.fi
