Basics and Future

This article explains the basic coding guidelines that apply and put the development effort into perspective by explaining the difficulties of legacy code and the interaction/migration to new MVC-based code. It also explains guideline differences between new and legacy code.

PHP code

For PHP code the PSR-12 coding standard applies.


For Python code the Python Enhancement Proposals (PEPs) apply. See the Python Developer’s Guide for detailed information.


Documentation is available about our architecture and used components.

Safeguard user input

We aim to validate user input before injecting it in the configuration in order to provide a more user friendly interface and prevent bad things to happen in the future.

Although we do understand that the perfect validation isn’t always possible at once (too much referential constraints, not always as easy to catch) it is a best practice to ask yourself if a specific input could be validated (if not now, what about the future).

The issue with user input impossible to validate is that it will bite you eventually, leading to future security issues waiting to happen (for example a non authorized user can write commands that will be executed with elevated privileges, we saw this with openvpn for example).

For this reason we do not allow plain text configuration data to be stored in our configuration (although some legacy components still use this opnsense/core#d62015 )


Feature requests for custom user inputs will be declined in our public repositories, defining what a feature should do also helps designing the right feature.


If custom input is needed, in most cases you can use hooks to include additional configuration data in the service, most services offer this type of support (either with predefined directories or via the template system).

This prevents arbitrary users from adding undefined configuration data.

The different field types in our model system are aimed to help the developer safeguard his or her code for unexpected input.

Ideal Development

Our ideal OPNsense system looks like a standard FreeBSD system using our pluggable user interface for management, which supports both real users as “machine” users (REST).

When developing we want the code to be clean and coded as DRY (Don’t Repeat Yourself) as possible and do not want to invent the wheel when not needed.

The user interface should to be able to run as non-root user instead of root by restructuring the way commands are passed to the system (configd).

Reality: Overdue Maintenance

In reality we forked a system that went without code maintenance for a very long time and we needed to transition that into something more structured.

One of the first things (on the programming part of the system) we did was build components around an existing framework (Phalcon) to create new modules, which could use validated configuration data (from the config.xml), supply a RESTful API and generate HTML output using standard templates (Volt).

We created the configd system, which can generate system configuration and execute system calls using predefined templates. And then we started using those new components for our first newly designed modules (like the proxy and the traffic shaper). More information about the “to-be” architecture can be found in our architecture documentation.


Knowing we can’t change the world in a single day and having a lot of legacy to drag around with us, our strategy consists of three parts:

1) Cleanup and maintenance Restructure old (legacy) code, basically all code in the src/www, src/etc/inc to make it better readable, easier to use and remove unused / unnecessary parts. By doing so we want to extend the lifetime of the old code a bit and make the transition in new code easier eventually.

2) Detach Move system configuration calls to configd where possible, which gives the administrator the advantage of running those commands from the command line and helps removing the need for root user access in the future. The ipsec VICI implementation is one example of this stage.

3) Moving on (re)build new parts, using our new modules, which provide a layered development system to automatically support API calls from other systems and XML based model templates to describe configuration data.

See also:

Our guidelines somewhat depend of the stage the code is in, when writing new code, all actions should use the API system for actually changing configuration and performing configuration tasks. They should, of course, use the normal PSR coding standards for PHP code and follow the Python PEPs.

When moving to the legacy part of the system, our goal is to stick as close to PSR1/2 as possible, knowing it will never be perfect.