Difference between revisions of "DSpam RELAY"

Revision as of 22:23, 27 July 2009

Configuring DSPAM as a seamless front-end relay using Postfix

This HOWTO explains how to set up DSPAM as a front-end relay. Using this configuration, you can point your MX records to the DSPAM server and then have DSPAM pass along any valid email to your mail server. The example provided also provides personalized training for each user it is protecting, even if users have multiple email aliases. This allows you to create more than just a dumb gateway server, but something smart enough to learn each user's mail. You may either account for all addresses behind your mail server (to ward off dictionary attacks) or configure pass-thru for unprovisioned users on the system to lighten the work load by provisioning only users who want filtering.

When configuring DSPAM as a relay, it's generally a good idea to set up DSPAM on its own server. Therefore, we will assume you've got a fresh server running *NIX with an existing MySQL 4.1+ installation (you'll want at least 4.1.12 to avoid some nasty bugs in MySQL which affect DSPAM).

Step 1: Configure, compile and install Postfix with MySQL support

To do this, you'll need to init a set of makefiles including the path to your MySQL includes and libraries...

make -f Makefile.init makefiles \
    'CCARGS=-DHAS_MYSQL -I/usr/local/mysql/include' \
    'AUXLIBS=-L/usr/local/mysql/lib -lmysqlclient -lz -lm'

Then simply

make && make install

Step 2: Configure, compile and install DSPAM with daemon + mysql support

You'll need the following options:

• MySQL
• Virtual Users
• Daemon mode

It may also be a good idea to enable:

• Preferences extension
• Debug

For example:

./configure     --with-storage-driver=mysql_drv \
                --with-mysql-libraries=/usr/local/mysql/lib \
                --with-mysql-includes=/usr/local/mysql/include \
                --enable-virtual-users \
                --enable-preferences-extension \
                --enable-daemon 

Step 3: Install DSPAM MySQL Objects (With a twist)

Create the MySQL objects as outlined in the mysql DSPAM doc, but use the virtual_user_aliases.sql script instead of virtual-users.sql script to create a table without a primary key. This will allow you to create multiple email addresses with the same uid, which is how DSPAM recognizes users.

Step 4: Configure DSPAM to receive LMTP and delivery SMTP

We're going to configure postfix to connect to DSPAM via LMTP using a domain socket. The following configuration properties should be set in dspam.conf:

ServerQueueSize		32
ServerPID		/var/run/dspam.pid
ServerMode		standard
ServerParameters	"--deliver=innocent"
ServerIdent		"localhost.localdomain"
ServerDomainSocketPath	/tmp/dspam.sock

You'll also want to use the following ParseToHeader parameters:

ParseToHeaders on
ChangeModeOnParse on
ChangeUserOnParse off

This prevents Postfix from needing to use any aliases for retraining. When users email [email protected], DSPAM will automatically realize that it needs to retrain the message. I'll explain how to set this up in a bit.

Step 5: Configure Postfix to use DSPAM + virtual UIDs table

The following is a sample configuration that will tell postfix to use DSPAM as its virtual transport (passing all mail to DSPAM via LMTP) and to use the dspam_virtual_uids table as its source for mailbox aliases. You can build on this and add mysql support for virtual_mailbox_domains, but you'll need to maintain your own database table for that.

virtual_transport = lmtp:unix:/tmp/dspam.sock
virtual_mailbox_domains = mydomain.com
virtual_mailbox_maps = mysql:/etc/postfix/vmailbox.cf

vmailbox.cf should look something like:

user = [mysql username]
password = [mysql password]
dbname = [mysql db]
query = SELECT username FROM dspam_virtual_uids WHERE username='%s'
table = dspam_virtual_uids
host = 127.0.0.1
select_field = username
where_field = username
additiona_conditions =

Step 6: Add a localStore preference for each user

The localStore preference defines the web directory name for each user (for the WebUI). Since users might have multiple email addresses, you want to avoid having a directory for each alias. You can do this by setting their web directory to match their uid.

To do this, you'll first need to allow the localStore override in dspam.conf:

AllowOverride	localStore

Next, set the localStore preference for that user to their uid or some other unique identifier:

dspam_admin ch pref [email protected] localStore 1 

Now, whenever any address pertaining to this user is emailed, information will be stored in $DSPAM_HOME/data/1

Step 7: Configure user aliases for dspam_virtual_uids

Postfix is now set up to do a lookup in dspam_virtual_uids. It _must_ find a valid address in this table in order to accept the message. What you'll need to do now is to create email addresses (and spam addresses) in this table for each user behind your mail server. You will need to assign any aliases under the same UID, and you'll also need to create a spam alias in this table. For example:

UID	Username
1	[email protected]
1	[email protected]
1	[email protected]			<- An alias 
1	[email protected]		<- Another alias	

When any of these destination addresses is specified, DSPAM will process mail under the same user so that only one database is used for all of these addresses. You can create as many aliases as you like, and in fact should probably write a script to pull this from your existing production system.

Congratulations! You're now set up. You can start DSPAM using dspam --daemon. You might want to run with verbose debug to test and ensure everything is working properly.

GLOBAL DATABASES

If you're thinking about going with a global database, I strongly recommend using merged groups + toe instead of a single global group. To do this, just follow the README directions for setting one up and leave everything the way it is. If, however, you insist on a single global group, you'll need to make one change to dspam.conf to accomodate this configuration. Add --user [globaluser] to your ServerParameters property. This will cause all mail to be processed using this user, but will still deliver using the recipient information.

ALIASES

If you have some aliases, you'll need to also set them up on your relay so that DSPAM can process the individual users. To do this, add the following lines to postfix's main.cf:

virtual_alias_domains =
virtual_alias_maps = mysql:/etc/postfix/valiases.cf

now create a valiases.cf similar to vmailbox.cf, only you'll want to create a new table just for aliases. the field pulled from should be a list of recipient addresses, for example:

[email protected]		[email protected],[email protected]

postfix will now deliver to each of these mailboxes instead of an alias address