Policies Service Configuration

Introduction

The Infinite Scale policies service provides a new gRPC API which can be used to check whether a requested operation is allowed or not. To do so, Open Policy Agent (OPA) is used to define the set of rules of what is permitted and what is not.

  • The policies service does not start automatically and must be started manually. For more details see the Start Infinite Scale section.

  • The reason for excluding the policies service from autostart is, that you must have a defined rulset available. If the ruleset is not available, the policies service will prevent other services from starting up.

Policies are written in the Rego query language. The location of the Rego files can be configured via yaml. A configuration using environment variables is not possible.

Default Values

  • The policies service listens on port 9125 by default.

General Information

The policies service consists of the following modules:

  • Proxy authorization (middleware)

  • Event authorization (async post-processing)

  • gRPC API (can be used by other services)

To configure the policies service, three environment variables need to be defined:

  • POLICIES_ENGINE_TIMEOUT

  • POLICIES_POSTPROCESSING_QUERY

  • PROXY_POLICIES_QUERY

Note that each query setting defines the Complete Rules variable defined in the Rego rule set the corresponding step uses for the evaluation. If the variable is mistyped or not found, the evaluation defaults to deny. Individual query definitions can be defined for each module.

To activate the policies service for a module, it must be started with a yaml configuration that points to at least one Rego file that contains the complete rule variable to be queried. Note that if the service is scaled horizontally, each instance should have access to the same Rego files to avoid unpredictable results. If a file path has been configured but the file is not present or accessible, the evaluation defaults to deny.

When using async post-processing via the postprocessing service, the value policies must be added to the POSTPROCESSING_STEPS configuration in the order in which the evaluation should take place. Example: First check if a file contains questionable content via policies. If it looks okay, continue to check for viruses.

For configuration examples, the example policies provided by the Example Policies are used.

Modules

gRPC API

The gRPC API can be used by any other internal service. It can also be used for example by third parties to find out if an action is allowed or not. This layer is already used by the proxy middleware. There is no configuration necessary, because the query setting (complete rule variable) must be part of the request.

Proxy Middleware

The proxy service already includes a middleware which uses the internal gRPC api to evaluate the policies. Since the proxy is in heavy use and every HTTP request is processed here, only simple and quick decisions should be evaluated. More complex queries such as file content evaluation are strongly discouraged.

If the evaluation in the proxy results in a denied outcome, the response will return a 403 Permission Denied with the following response body:

{
    "error":
    {
        "code": "deniedByPolicy",
        "message": "Operation denied due to security policies",
        "innererror":
        {
            "date": "2023-09-19T13:22:20Z",
            "filename": "File",
            "method": "POST",
            "path": "/dav/spaces/some-space-id/Folder/",
            "request-id": "9CFCE925-F9D9-4F26-AB3B-2C1C40A9CD0C"
        }
    }
}

Event Service (Postprocessing)

This layer is event-based and part of the postprocessing service. Since processing at this point is asynchronous, the operations can also take longer and be more expensive, like evaluating the contents of a file.

Defining Policies to Evaluate

Each module can have as many policy files as needed for evaluation. Files can also include other files if necessary. To use policies, they have to be saved to a location that is accessible to the policies service. As a good starting point, take the config directory and use a subdirectory collecting all the .rego files, though any other directory can be defined. The config directory is already accessible by all services and usually is included in a backup plan.

If this is done, it’s required to configure the policies service to use these files:

It is important that all necessary files are added to the list of files the policies service uses. 
policies:
  engine:
    policies:
      - your_path_to_policies/proxy.rego
      - your_path_to_policies/postprocessing.rego
      - your_path_to_policies/util.rego

Once the references to policy files are configured correctly, the _QUERY configuration needs to be defined for the proxy middleware and for the events service.

Setting the Query Configuration

To define a value for the query evaluation, the following scheme is necessary:

data.<package-name>.<complete-rule-variable-name>

  • The keyword data is mandatory and must be present.

  • The package-name is defined in one .rego file like package postprocessing. It is not related to the filename. For more details, see the packages documentation.

  • The complete-rule-variable-name is the variable providing the result of the evaluation.

  • Exact one of the defined files, which is responsible for returning the evaluation result, must contain the combination of <package-name> and <complete-rule-variable-name>.

Proxy

Note that this setting has to be part of the proxy configuration.

proxy:
  policies_middleware:
    query: data.proxy.granted

The same can be achieved by setting the following environment variable:

PROXY_POLICIES_QUERY=data.proxy.granted

Postprocessing

policies:
  postprocessing:
    query: data.postprocessing.granted

The same can be achieved by setting the following environment variable:

POLICIES_POSTPROCESSING_QUERY=data.postprocessing.granted

As soon as that query is configured, the postprocessing service must be informed to use the policies step by setting the environment variable:

POSTPROCESSING_STEPS=policies

Note that additional steps can be configured and their position in the list defines the order of processing. For details see the postprocessing service documentation.

Example Policies

The policies service contains a set of preconfigured example policies. See the deployment examples directory for details. The contained policies disallow Infinite Scale to create certain file types, both via the proxy middleware and the events service via postprocessing.

  • 8.2.0

Rego policies deployment example directory

Using git branch name: stable-8.2, to point to the latest stable version that also includes patches

Extend Mime Type File Extension Mapping

In the extended set of the rego query language, it is possible to get a list of associated file extensions based on a mime type, for example ocis.mimetype.extensions("application/pdf").

The list of mappings is restricted by default and is provided by the host system Infinite Scale is installed on.

This list can be extended. To do so, Infinite Scale must be provided with the path to a custom mime.types file that maps mime types to extensions. The location of the file must be accessible by all instances of the policy service. As a rule of thumb, use the directory where the Infinite Scale configuration files are stored. Note that existing mappings from the host are extended by the definitions from the mime types file, but not replaced.

The path to that file can be provided via a yaml configuration or an environment variable. Make sure to replace the OCIS_CONFIG_DIR string by an existing path. See the documentation of the Configuration Directory and the Extended Environment Variables for predefined or manually defined config paths.

POLICIES_ENGINE_MIMES=OCIS_CONFIG_DIR/mime.types
policies:
  engine:
    mimes: OCIS_CONFIG_DIR/mime.types

A good example of how such a file should be formatted can be found in the Apache svn repository.

Event Bus Configuration

The Infinite Scale event bus can be configured by a set of environment variables.

  • In case of an orchestrated installation like with Docker or Kubernetes, the event bus must be an external service for scalability like a Redis Sentinel cluster or a key-value-store NATS JetStream. Both named stores are supported and also used in Caching and Persistence. The store used is not part of the Infinite Scale installation and must be separately provided and configured.

  • Note that from a configuration point of view, caching and persistence are independent of the event bus configuration.

Note that for each global environment variable, a service-based one might be available additionally. For precedences see Environment Variable Notes. Check the configuration section below.

Without the aim of completeness, see the list of environment variables to configure the event bus:

Envvar Description

OCIS_EVENTS_ENDPOINT

The address of the event system.

OCIS_EVENTS_CLUSTER

The clusterID of the event system. Mandatory when using NATS as event system.

OCIS_EVENTS_ENABLE_TLS

Enable TLS for the connection to the events broker.

OCIS_INSECURE

Whether to verify the server TLS certificates.

OCIS_EVENTS_AUTH_USERNAME

The username to authenticate with the events broker.

OCIS_EVENTS_AUTH_PASSWORD

The password to authenticate with the events broker.

Configuration

Environment Variables

The policies service is configured via the following environment variables. Read the Environment Variable Types documentation for important details. Column IV shows with which release the environment variable has been introduced.

404: Not Found

  • 8.2.0

404: Not Found

YAML Example

  • 8.2.0

404: Not Found