Configuration Using Local Policy File (Linux)

When using open-appsec for NGINX or Kong on Linux the configuration can be done in a declarative way using a single YAML file which holds all the relevant configuration objects. This way it is compatible with integration in GitOps CD-based processes.

Alternatively management can also soon be done centrally via the open-appsec WebUI (SaaS): Using the Web UI (SaaS)

Location of the declarative configuration file

The default location of the declarative configuration file is here:

/etc/cp/conf/local_policy.yaml

You find syntax and schema of the declarative configuration file explained here: Local Policy File (Advanced)

You can show and edit the full default declarative configuration file with the following command:

vi /etc/cp/conf/local_policy.yaml

or by using the interactive CLI tool open-appsec-ctl : Using the open-appsec-ctl Tool

Basic configuration

The default policy within the default configuration file, which is created during the installation, contains the following setting which sets the mode to detect-learn for all web resources provided by the NGINX or Kong Gateway:

policies.default.mode: detect-learn

If you want attacks instead to be prevented by default for all web resources you can change this as follows:

policies.default.mode: prevent-learn

The section policies.specific-rules allows you to create specific rule entries for specific hostnames, hostname-path combinations or paths which override the default policy.

The mode settings defined in the policy for default or specific-rules will only have an effect on the actual enforcement for specific security features when the override-mode setting in the referenced practice is set to as-top-level as this will cause it to inherited the mode setting from the policy.

It is recommended to configure a specific rule for each of your protected web applications and web APIs assets (starting with detect-learn mode, later move to prevent-learn). This allows you to apply a separate enforcement mode setting for each of these protected assets as well as to customize many other settings like selecting the logging configuration, the threat prevention practices configuration or selecting a custom-response like a specific response code or a custom block page.

Also the real-time contextual machine learning will be done individually per each configured asset/specific rule. Note that these settings are all configured by referencing other elements which are defined separately in the configuration file as well, so that you can reuse them multiple times in a kind of object-oriented way.

policies:
  default:
  ...
  ...
  specific-rules:
  - host: "www.my-specific-host.com/my-specific-path"
    triggers:
    - appsec-default-log-trigger
    mode: detect-learn
    practices:
    - webapp-default-practice
    custom-response: appsec-default-web-user-response

It is recommended that once sufficient confidence was gained in detect-learn mode for an asset which has a specific rule (review the logs) to move this specific rule to prevent-learn mode:

policies:
  default:
  ...
  ...
  specific-rules:
  - host: "www.my-specific-host.com/my-specific-path"
    triggers:
    - appsec-default-log-trigger
    mode: prevent-learn
    practices:
    - webapp-default-practice
    custom-response: appsec-default-web-user-response

Applying a changed local declarative configuration file

Once you did any changes to the local declarative configuration file local_policy.yaml in order to become active you must apply the new policy:

Use the open-appsec-ctl tool to apply the changes in the policy as follows:

open-appsec-ctl --apply-policy

Configuring the local declarative configuration file

On the next page you find the full description for the different configuration sections and elements that can be part of the declarative configuration file:

Local Policy File (Advanced)