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  1. Module Management
  2. Logging
  3. Data Root
  4. API
  5. Database
  6. Random Number Generator
  7. Notifications
  8. Update Framework
  9. UI Server
  10. Utilities

Module Management

In order to maintain a clear concept and code structure, the Portmaster Core Service is split up into many modules. Everything that serves a distinct purpose usually is a separate module. This keeps the code clean and makes it easier to build and maintain high quality software.

The module management is responsible for preparing, starting and stopping all modules in the correct order and also provides utilities to safeguard module operation. These allow a module to quickly start a secure worker or a repeating task. The module manager can then schedule tasks and correctly wait for every bit to properly stop when shutting down.

For convenience, multiple small modules are bundled into big modules - such as “Privacy Filter”, “Secure DNS”, etc. In the code these “Big Modules” are referred to as Subsystems, while in marketing and other high level context they are simply called “Modules”.


Golang Docs

Writing logs is vital for understanding what is going on and is of tremendous help when trying to identify what is going wrong.

It uses a leveled log system in order to regulate the amount of information saved. On the trace level, it can also attach logs to a context, which are then written in a batch in order to clunk logs of one operation together. This is especially useful, as the Portmaster Core Service is highly concurrent and it can otherwise be hard to attribute log lines to a certain operation.

You can configure the Log Level in the settings or set it on the cmdline with the --log argument.

You can view saved log files in the logs directory in the data root.

This is what logs could look like:

210112 12:58:38.691 er/storage:096 ▶ DEBU 013 updates: loaded index stable.json
210112 12:58:38.700 api/router:065 ▶ INFO 050 api: starting to listen on
210112 12:59:19.785 connection:539 ▶ INFO 723 filter: connection user:/usr/lib/firefox/firefox:2854 to ([REDACTED]) accepted: default permit Σ=7.728613ms
            6.114µs terception:092 ▶ TRAC     filter: handling packet: OUT TCP [REDACTED]
         4.344452ms ocess/find:022 ▶ TRAC     process: getting pid from system network state
            6.696µs ss/process:095 ▶ TRAC     process: getting process for PID 2854
           21.753µs ss/profile:025 ▶ TRAC     process: profile already loaded
           39.661µs terception:102 ▶ TRAC     filter: created new connection [REDACTED]
            5.436µs terception:234 ▶ TRAC     filter: handing over to connection-based handler
            9.038µs terception:271 ▶ TRAC     filter: starting decision process
          169.189µs tel/entity:300 ▶ TRAC     intel: CNAME filtering enabled, checking [] too
            4.986µs tel/entity:317 ▶ TRAC     intel: loading domain list for
         2.982395ms tel/entity:317 ▶ TRAC     intel: loading domain list for
            10.52µs tel/entity:371 ▶ TRAC     intel: loading ASN list for 5403
            4.124µs tel/entity:429 ▶ TRAC     intel: loading IP list for [REDACTED]
           22.082µs tel/entity:396 ▶ TRAC     intel: loading country list for AT
          102.167µs all/master:355 ▶ TRAC     filter: LMS score of eTLD+1 is 100.00

Data Root

Golang Docs

The Portmaster Application keeps everything it needs in a single directory. On Windows, this is %PROGRAMDATA%\Safing\Portmaster and on Linux it is /opt/safing/portmaster.

Linux installs before November 2021 were located in "/var/lib/portmaster", while new Linux installs are located in "/opt/safing/portmaster".

The dataroot is not a module, but just a small utility that provides easy access to it. It uses the DirStructure utility to ensure that all the directories always have the correct file system permissions.

Note: Having everything structured into one directory has many practical advantages. However, we are aware that some operating systems do not like mixing live data (databases) with executables (updates). We are planning to improve on this in the future.


Golang Docs

The API provides an interface for all other software components, like the Portmaster UI, to interact with the Portmaster Core Service. Both the Portmaster UI and the Notifier (System Tray Applet) use the API to change settings and subscribe to data changes via the database API.


Golang Docs

The database module provides a persistence layer. This key/value storage provides a uniform interface to save, read and update data. It supports scoped data storages as well as virtual database backends. The module also includes a simple permission layer to protect important assets.

There are included data interaction helpers for queries, bulk operations, subscribing to database changes and hooks. Read and write caching improves performance on slow devices.

List of Databases

The Portmaster Core Service uses these databases:

  • core: Main storage for app settings.
  • cache: For all data that is cached and can be automatically recovered if lost.
  • runtime: Virtual database that exposes internal runtime data to benefit from the database layer features.
  • config: Virtual database that gives easy access to configuration and associated metadata.
  • network: Virtual database that exposes all the network activity for the monitoring in the App.

If you have the Development Mode enabled, you can access all the data in these database directly via the Dev Console, which is available at

Random Number Generator

Golang Docs

This module employs the Fortuna PRNG by Ferguson and Schneier.

It sources randomness both from the standard OS interface as well as internal Portmaster Core Service modules, which can easily and safely ingest random data into the RNG. This ensures strong encryption in case of a weakness in the operating system’s PRNG.
Most prominently, the SPN will inject secret random data (eg. nonces or padding) received from SPN nodes.

The created randomness is then used by other modules wherever randomness is required. Examples are choosing random ports for DNS requests or generating secure cookies/access tokens.


Golang Docs

The notification module takes care of handling notifications: These range from informational messages to important, actionable items.

This module also takes care of connection prompts, even though they are displayed separately in the Portmaster UI.

On Windows, the Notifier (System Tray Applet) interfaces with the Windows Notification Center in order to display notifications via the native interface. We use SnoreToast as a helper for submitting notifications.

On Linux, the Notifier (System Tray Applet) sends notifications to the notification server via D-BUS, which is typically provided by your distribution.

Note: Desktop notifications can be disabled in the settings.

Update Framework

The update system makes sure that all required resources are available and up to date. Resources include: executables, UI assets, filter lists.

The update system keeps track of available versions and automatically downloads new resource versions. Multiple versions are kept locally in case an upgrade breaks and needs a rollback.

The communication with the update server is always encrypted and authenticated.

Note: In the future, all resources provided via the update framework will also be cryptographically signed as an additional layer of protection.

Currently, updates are checked for every hour. This frequency was chosen to stay up to date with the ever-changing landscape of malware/tracker/phishing domains managed by the various filter lists. Kudos to everyone doing excellent work in that field!

Note: You can always see the current active and available versions in the Portmaster UI.

UI Server

Golang Docs

The UI Server module serves UI resources and assets locally on port 817.

This is where the Portmaster User Interface gets its resources from - loading them directly from the Portmaster Core Service. Thus, with the Developer Mode enabled, you can also open the Portmaster UI in your browser if you prefer to do so via

Please note that some (non-vital) features, such as Application icons on Windows will not work in the browser since they depend on the supplied Portmaster UI.


While not a module, it is worth mentioning where we collect all our internal utilities that are used across the modules. These include basic Go helper functions, OS-specific interfaces and a small utility to gather and format debugging information.