Version 3 (modified by Kim Minh Kaplan, 11 years ago)

Fix hyperlinks

Copyright 2007 by Kim Minh Kaplan

Greyfix is the greylisting policy daemon for Postfix written by Kim Minh Kaplan. Greylisting is an anti spam technique described by Evan Harris. Postfix is a popular mail transport agent developped by Wietse Zweitze Venema. Greyfix uses Postfix policy mechanism to enable greylisting with Postfix.

<contents>

* Latest version

greyfix-0.3.3.tar.gz (PGP signature)

  • BUGFIX expire correctly triplets
  • Add option =--dump-triplets=, =--reject-action= and =--greylisted-action=.
  • Really delete expired triplets from the DB.
  • Note that =451= reject code is probably better than =DEFER_IF_PERMIT=.

* Features

  • Low and tunable resource usage and high efficiency. The program is written in C and uses Berkeley DB to track mailers. By itself it allocates memory only for a single request and the Berkeley DB library can be configured to use very few RAM.
  • Integrates with Postfix's master daemon. Postfix will shutdown greyfix when it is not used completely freeing its runtime resources.
  • No administrative burden. Everything happens "automagically".
  • No need for a database server. Uses Berkeley DB.

* Requirements

* Quickstart

Greyfix uses GNU's build system. To install the greyfix daemon just type the following commands:

<example>

$ gzip -cd greyfix-0.3.3.tar.gz | tar xf - $ cd greyfix-0.3.3 $ ./configure $ make $ su -c 'make install'

</example>

Edit Postfix's master configuration file, =/etc/postfix/master.cf=, and add the following:

<example> greyfix unix - n n - - spawn

user=nobody argv=/usr/local/sbin/greyfix -/ 24 -r 451%sTry%sagain%sin%s%d%ssecond%p.%sSee%shttp://www.kim-minh.com/pub/greyfix/%sfor%smore%sinformation.

</example>

Edit Postfix's main configuration file, =/etc/postfix/main.cf= and add the following:

<example> smtpd_recipient_restrictions = permit_mynetworks,

reject_unauth_destination, check_policy_service unix:private/greyfix

</example>

If there is already a =smtpd_recipient_restrictions= configuration line you should edit it rather than add a new one. The important part for greyfix is that you should add <code>check_policy_service unix:private/greyfix</code> to it.

Finally have postfix reload its configuration with <code>postfix reload</code>.

* Usage

<example> greyfix [-v] [-d] [-h <Berkeley DB home directory>] [-g <greylist delay>]

[-b <bloc maximum idle>] [-p <pass maximum idle>] [-r <reject action>] [-G <greylisted action>] [-/ <network bits>] [--dump-triplets]

-b <seconds>, --bloc-max-idle <seconds>

This determines how many seconds of life are given to a record that is created from a new mail (ip, from, to) triplet. Note that the window created by this setting for passing mails is reduced by the amount set for --greylist-delay. NOTE: See also --pass-max-idle. Defaults to 18000 (5 hours).

-d, --debug

Debug logging

-g <seconds>, --greylist-delay <seconds>

This determines how many seconds we will block inbound mail that is from a previously unknown (ip, from, to) triplet. If it is set to zero, incoming mail association will be learned, but no deliveries will be tempfailed. Use a setting of zero with caution, as it will learn spammers as well as legitimate senders. Defaults to 3480 (58 minutes).

-h <Berkeley DB home directory>, --home <Berkeley DB home directory>

Location of the Berkeley DB environment home location (the default is autoconf's $localstatedir/greyfix i.e. /usr/local/var/lib/greyfix).

-p <seconds>, --pass-max-idle <seconds>

How much life (in secs) to give to a record we are updating from an allowed (passed) email.

The default is 36 days, which should be enough to handle messages that may only be sent once a month, or on things like the first monday of the month (which sometimes means 5 weeks). Plus, we add a day for a delivery buffer.

-r <reject action>, --reject-action <reject action>

The reject action directive that will be used. See access(5) for valid actions. The string expands %d to the number of seconds, %p to the empty string if %d expands to 1 or "s" otherwise, %s to " " and %% to "%".

The default is "DEFER_IF_PERMIT Greylisted by Greyfix X.Y.Z, try again in %d second%p. See http://www.kim-minh.com/pub/greyfix/ for more information.". http://cvs.puremagic.com/viewcvs/greylisting/schema/whitelist_ip.txt?r1=1.10&r2=1.11 suggests that a 451 SMTP error code is a better idea.

-G <greylisted action>, --greylisted-action <greylisted action>

The action that will be used the first time a triplet passes greylisting. Same expansion as for --reject-action.

The default is "PREPEND X-Greyfix: Greylisted by Grefix X.Y.Z for %d second%p. See http://www.kim-minh.com/pub/greyfix/ for more information."

-v, --verbose

Verbose logging

-/ <nbits>, --network-prefix <nbits>

Only consider the first <nbits> bits of an IPv4 address. Defaults to 32 i.e. the whole adresse is significant.

--dump-triplets

Dump the triplets database to stdout. Mostly for debugging purposes.

</example>

* Notes

GNU Autoconf's default value for =$(localstatedir)= is =/usr/local/var/lib= which is quite different from what most Unix distribution use. You'll probably want to invoke configure like this:

<example>

$ ./configure --localstatedir=/var/lib

</example>

This makes Greyfix DB be located in =/var/lib/greyfix=. Alternatively you can use the =-h <DB home>= command line option but do not forget to create the directory and give it correct permissions so that Greyfix can access it.

Greyfix uses syslog with facility =LOG_MAIL=. As such the log messages should appear along postfix's.

You should use some whitelisting of some sort for some servers. A good starting base is whitelist_ip.txt.

* TODO

* Older versions