# OpenSMTPD now supports regex in match rules

TL;DR:
regex table lookups were introduced for builtin filters.
After a few weeks of working solely on filters, I wanted to work on something else.
Using the same mechanism, all match criterias using tables can support regex.


## K_REGEX lookups

The table mechanism is used within OpenSMTPD to perform all kinds of lookups.

Recently, while working on builtin filters, I introduced the K_REGEX lookup type allowing tables to serve regex(3) patterns.

When a K_REGEX lookup is performed, the table API will use the lookup key as a string and iterate over entries in the table, compiling them with regcomp(3) and performing a simple regcomp(3) against the key.

## regex use in match criterias

In the new smtpd.conf, accept rules where replaced with match rules.

The match rules consist of matching criterias which describe how an envelope should look like to be accepted for a specific action. Among these criterias, you’ll find for example from src, for domain, mail-from or even rcpt-to, which can either take a table, or a string literal which … is actually an inlined on-element table.

The new feature introduces a regex keyword that can be used to instruct OpenSMTPD that the table will use regex. This basically allows the following:

table regex_domains file:/etc/mail/list-of-regex.txt"

match for domain regex "^.*\.example.com\$" action foobar
match for domain regex <regex_domains> action foobar


except that it also allows it for pretty much every criteria that can be used on a match rule and expect a parameter.

## What next ?

This was just committed a few minutes ago in -current and the feature is essentially complete, so there’s not much in that front.

You can already play with that feature which has been documented in the smtpd.conf(5) man page.

So … NOW, I’m taking a break until next week because I did everything I wanted to do for this year ;-)