SecDocker

An application firewall for Docker

Description

SecDocker is a Go application that acts as a firewall for Docker. It's designed to receive all the traffic that goes to the Docker API / socket and drop the requests that contain unauthorized parameters. You can provide rules and specifications as well as general restrictions to be applied to every request, modifying the traffic as it goes to the Docker daemon.

This application is meant to run transparently. In order to work, you must redirect the traffic to this tool without modifiying it. The easiest way to do this (specially in a test environment) is by using iptables.

For example:

sudo iptables -A PREROUTING -t nat -i eth0 -p tcp --dport 2376 -j REDIRECT --to-port 8999

to redirect external traffic to SecDocker

Config file

An example config file is provided in the repo as config.yml

The config file has the following fields:

• plugins

  The list of plugins to be loaded

• restrictions

  Here are the rules that SecDocker checks. If a run command contains any of the rules, the action is blocked.

  Available restrictions:

  • ports
  • users
  • mounts
  • environment
  • securitypolicies
  • images
  • privileged

• general

  This are the restrictions that are applied to each run instruction after it is checked.

  Available restrictions:

  • memory
  • cpu
  • user
  • environment

Log file

A log file based on Logrus is written to secdocker.log containing information about every event that happens. This includes:

• Requests received
• Allowed requests
• Forbidden options requested

Compile and run

• To compile:

  go build

• To run:

  ./secdocker

Testing

To test the code run:

go test `go list ./... | grep -v plugins` -v -cover -coverprofile=coverage.out

To obtain the coverage:

go tool cover -func=coverage.out

Plugins

Plugins are components that are independent from the original program. In our case, the only requirement is that the the plugins must be compiled with the current version of SecDocker in order to work.

To compile them:

go build -buildmode=plugin -o plugin_name.so plugin_name.go

Plugins are called by using Process(image string) bool at the moment. In order to create your own plugin, you must implement this method inside the plugin. The bool response says if the plugin output states that the image is safe.

At the moment, we have 2 plugins:

• Anchore

  This plugin depends on a working anchore engine (https://hub.docker.com/r/anchore/anchore-engine). It will ask for an analysis of the image. All can be customized inside the config.yml file inside the anchore folder.

• Notary

  This plugin checks if the local image that is being run has the same digest as the remote image.

CI

The application is designed to be used in DevOps environments to provide a secure use of containers. An example diagram with Jenkins and Github / Gitlab is provided:

Flow diagrams

Blocked create container

Credits

It was built at: https://seguridad.unileon.es/index.php/SecDocker

Notes

The TCP proxy code (tcpintercept package) is a modified version of the one from the project Trudy