Posted in Programming, Tech

How to fetch IP ranges/entries from SPF records in bash

Recently I needed to fetch IP ranges from SPF records. After looking at different python/ruby/perl modules I came to the conclusion that a fancy module (sometimes with wonky dependencies) was overkill just to parse a simple SPF record. So I threw together a simple bash script that is mainly just fetching the SPF record with dig and grep:

It iterates through the options (it currently recognizes a, mx, ip4, ip6, include, and redirect), and then sorts the output by ipv4, then ipv6.

Download URL: fetch_spf.sh

Posted in Security, Server, Tech

Setting up multidomain DKIM with Exim

I was recently setting up SPF, DKIM and DMARC for multiple domains and was having trouble getting Exim to sign emails for the different domains. I found an article here explaining the steps. But I kept getting the following error in my exim logs:

failed to expand dkim_private_key: missing or misplaced { or }

The suggested configuration was the following:

I’m not quite sure why, but Exim was having trouble using the macros in the following macros, so I ended up changing it to the following snippet instead. If you don’t use DKIM_FILE you can omit it. Also you might want to set DKIM_STRICT to true if you published a DMARC policy that will reject or quarantine email failing the DKIM tests (unset, or “false” tells Exim to send the message unsigned if it ran into problems signing the email). The default setting for DKIM_CANON is “relaxed“, so it also can be omitted.

Other than that, just make sure the exim process has permissions to access the dkim directory and certificate files and everything should work nicely.

Posted in Internet Stuff

Playing around with Exim, Spamassassin, DKIM and SPF

I was playing around with my mail server today and decided to have a look at DKIM and SPF. Jump to the bottom for some useful links. You will have to be able to change TXT entries for your domain/subdomains to do any of this. Sending a mail to check-auth@verifier.port25.com will generate an auto-reply with the result of your mail servers settings. I also noticed that Exim wasn’t listening to the IPv6 interface and promptly fixed that, and have received my first mail via IPv6.

Some spamassassin scores for your local/user settings:

SPF:
Syntax: http://www.openspf.org/SPF_Record_Syntax
Tools & Information: http://www.openspf.org/
Wizard: http://www.spfwizard.net/

DKIM:
Exim walkthrough: http://mikepultz.com/2010/02/using-dkim-in-exim/
Domain specific settings: http://www.debian-administration.org/users/lee/weblog/41
Tools: http://dkimcore.org/tools/
Wizard: https://www.port25.com/dkim-wizard/