dmProxy

Discourse Mail Proxy

This small script is inspired by AlterMIME. but does a very specific task Unlike just appending a disclaimer text in a mail, it looks for a specific set of words in a mail and replaces that with a link. This was specifically developed for Discourse to replace link_url or show_url with a URL based on a subdomain value fetched from custom fields in the discourse database. You are most welcome to take and break it for your needs !! Cheers, Anindya Roy i@anindya.me

Pre-Requisites

Any Linux distribution with bash and Postfix already installed and running

Installation

Step 1.

Download dmProxy.sh and dmProxy.conf or simply do a git clone of this folder. I recommend to do it in a folder like /opt/dmProxy. But you are welcome to use your imagination. then move dmProxy.conf to /etc/

Step 2.

Now open the /etc/dmProxy.conf file in your favorit text editor and localize it with your system settings. Everything is commented pretty well. Though I am bad with spellings so pardon my typos ;-) ! here is a quick list of what all you would need to replace

Line 3: INSPECT_DIR=/var/spool/filter -- This is the folder where the mails will be captured and worked on. we will create it in the next step

Line 5: SENDMAIL=/usr/sbin/sendmail -- Your sendmail location. do a whereis sendmail to find this

Line 7: HTTP="https" -- Change it with what suites you. HTTP or HTTPS. this will be appended at the beginning of the link

Line 9: DOMAIN="monitoringclient.com" -- Your domain goes here

Line 11: export PGPASSWORD="" -- Put your Postgres Password Here. yes plain text. bad idea. there are other ways to do this aswell. do some googling ;-)

Line 13: dbHost="" -- Put your PostgreSQL Hostname or IP here

Line 15: dbName="" -- And DB Name Goes here. most likely it will be discourse.

Line 17: dbUser="" -- Finally the db user. Remember the plain text password in line 21? create a readonly DB user and use it for this script.

And you are pretty much done with the script

Step 3.

Create a folder where your mails will be kept while parsing. This folder needs to be secure enough so we will create a dedicated user for running our proxy and accessing this folder in next step

#mkdir /var/spool/filter

Step 4.

Create a user called filter like this

#useradd -r -c "Postfix Filters" -d /var/spool/filter filter

Step 5.

Now make sure the folder /var/spool/filter is owned by the filter user

#chown filter:filter /var/spool/filter

Step 6.

and tighten the security a bit

#chmod 750 /var/spool/filter Also, as the user is now created. lets give our shell script rights to be run by filter group

#chown root.filter /opt/dmProxy/ -R

and make it executable

#chmod 755 /opt/dmProxy/dmProxy.sh

Step 7.

Now open postfix's master.cf with your favorit text editor and add a line just below

smtp inet n - y - - smtpd

-o content_filter=dmProxy:dummy #This is the line to be added

NOTE: if you are using smtps then you have to append the same line below smtps as well. This should look like

smtps inet n - y - - smtpd

-o content_filter=dmProxy:dummy

Step 8.

And now you have to define the dmProxy content filter that you have just created. go to the end of master.cf and append the following 2 lines

dmProxy unix - n n - - pipe

flags=Rq user=filter argv=/opt/dmProxy/dmProxy.sh -f ${sender} -- ${recipient}

Step 9.

And finally restart postfix

#/etc/init.d/postfix restart

and you are done !! wasn't it easy ;-) ?