Contents
https://qmail-spp.sourceforge.net/doc/
qmail-spp - qmail SMTP plugin patch http://qmail-spp.sourceforge.net/
1. What's that?
qmail-spp adds plugin support to qmail's SMTP daemon (qmail-smtpd). It's written entirely in C using native qmail libraries, so it does not create any dependencies.
2. Why it has been written / Why use it?
qmail-spp has been written because currently there is no common way of enhancing qmail-smtpd's functionality apart of patches which usually are not compatible one with other and require recompilation. In addition, qmail-spp gives you possibility of enhancing your mail server in any language, so you can easily integrate it with anything you want.
3. How does it work?
Plugins are external programs which are executed after processing SMTP
command, but just before accepting it by qmail - this lets you to add extra
checks on commands' arguments before accepting it - for instance you can check
envelope recipient address against your "black list".
Plugins can be written in any language, because they are independent programs.
They:
- should not read anything from standard input,
- should not exit with error code 120,
- should print all errors to standard error (they are logged),
- can print commands on standard output.
All required data (as HELO host, last RCPT address, etc.) can be retrieved
from environmental variables.4. Which SMTP commands can be enhanced this way?
HELO/EHLO, MAIL, RCPT, DATA and (if supported) AUTH. There is also one pseudo-event triggered just after client connection.
5. What environmental variables are set by qmail-spp?
SMTPHELOHOST - argument of 'HELO/EHLO' command SMTPMAILFROM - argument of 'MAIL' command SMTPRCPTTO - argument of last 'RCPT' command SMTPRCPTCOUNT - how many times have 'RCPT' command been accepted SMTPRCPTCOUNTALL - as above, but counts rejected 'RCPT' commands too SMTPRCPTHOSTSOK - rcpthosts check was successful (1) or not (0) If supported: SMTPAUTHUSER - user name of authorized SMTP client SMTPAUTHMETHOD - used SMTP authorization method You should probably also take a look at http://cr.yp.to/ucspi-tcp/environment.html if you use tcpserver (from ucspi-tcp package).
6. What environmental variables can I use to control qmail-spp?
NOSPP - if set, qmail-spp won't run in this session
SPPCONFFILE - if set, specifies alternative configuration file
(instead of standard "control/smtpplugins")7. What plugin commands are supported and how to use them?
A - Accept mail - turn off qmail-spp in this session
N - Next - accept current SMTP command (do not execute
remaining plugins for this command)
O - Ok - like N, but omits qmail checks in MAIL and RCPT
Emsg - Error - do not accept this SMTP command and immediately
send 'msg' to the client
LMmsg - Later, Mail - like E, but shows error after MAIL command
LRmsg - Later, Rcpt - like E, but shows error after RCPT command
LDmsg - Later, Data - like E, but shows error after DATA command
Rmsg - Reject mail - send 'msg' to the client and drop connection
D - Drop connection immediately, without printing anything
Svar=value - Set environmental variable 'var' to 'value'
Uvar - Unset 'var' variable
Hcontent - Header - add header 'content' (eg. 'X-Spam-Flag: YES')
Cfoo@bar.com - Change last address provided by the client to 'foo@bar.com'
(MAIL FROM or RCPT TO address)
Pmsg - Print - send 'msg' to the client
Plugins should simply print commands on standard output, one per line,
eg. RCPT plugin which prints
Cspam@myhost.com
HX-Spam-Flag: YES
HSspam=1
A
and print "redirected spam from <$SMTPMAILFROM>" to standard error
will:
change last RCPT TO address to 'spam@myhost.com'
add 'X-Spam-Flag: YES' header
set $spam to 1
accept mail (turn off qmail-spp for this session)
and log 'redirected spam from <spammer@aol.com>' message (where
<spammer@aol.com> is envelope sender address)
NOTES:
* each plugin command must end with a new line
* valid SMTP response codes are not added automatically to messages
generated by plugins
* A, N, O, E, R and D should be used as the last command8. Installation
Simply cd into the qmail source dir, patch it and install in usual way.
Following patches are bundled with qmail-spp:
* qmail-spp.diff - patch against stock qmail 1.03
* netqmail-spp.diff - patch against netqmail 1.05 -
http://qmail.org/netqmail/
* qmail-spp-smtpauth.diff - patch against qmail patched with
Krzysztof Dabrowski's SMTP AUTH patch -
http://members.elysium.pl/brush/qmail-smtpd-auth/
* qmail-spp-smtpauth-eh.diff - patch against qmail patched with
Erwin Hoffman's SMTP AUTH patch v. 0.4.3 -
http://www.fehcom.de/qmail/smtpauth.html
* qmail-spp-smtpauth-tls-20060105.diff - patch against netqmail 1.05
patched with Bill Shupp's smtpauth/tls combo patch v. 20060105, contributed
by Jason 'XenoPhage' Frisvold (friz /at/ godshell \dot\ com)
original Shupp's patch at:
http://shupp.org/patches/netqmail-1.05-tls-smtpauth-20060105.patch
Remember to create configuration file (see below) - you can also use sample
smtpplugins file bundled in samples/ directory.9. Configuration
The main standard configuration file of qmail-spp is
/var/qmail/control/smtpplugins
(assuming that /var/qmail is your qmail home dir).
It consist of few sections, one for each command:
connection - for plugins run just after client connection
helo - for HELO/EHLO
mail - for MAIL
rcpt - for RCPT
data - for DATA
auth - for AUTH (if supported)
Section names are marked using square brackets ('[' and ']'). After section
name there are plugins to execute for this command - one per line.
Example:
# smtpplugins sample file
[connection]
:plugins/rbl -r relays.ordb.org
[auth]
plugins/onlycrammd5
[helo]
:plugins/badhelo example.com spammers.com
[mail]
plugins/blacklisted
plugins/spf
plugins/dnsmx-check
[rcpt]
plugins/rcptexists
:plugins/tarpit --start-after=5 --wait=3
plugins/greylisting
[data]
plugins/foo
Paths are relative to the qmail home dir.
If you want your plugin to be executed by system shell, add ':' just before
plugin path. This might be useful for debugging or passing arguments to your
program, but note that this is slightly slower than normal mode.10. More information
- More information can be found on qmail-spp home page:
11. Legal notes
Copyright (c) 2004-2006 Pawel Foremski <pjf@asn.pl> Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license can be found at http://www.gnu.org/copyleft/fdl.html#SEC1 # vim: textwidth=80 tabstop=2 expandtab