Permissions Policy Guide (Previously Feature Policy)

The Permissions Policy Guide has been moved to services/network/public/cpp/permissions_policy/README.md

Document Policy Guide

How to add a new feature to document policy

Document Policy (see spec) is a similar mechanism to Permissions Policy. It is intended to cover those kinds of features which don't involve delegation of permission to trusted origins; features which are more about configuring a document, or removing features (sandboxing) from a document or a frame. Document Policy can only be set through an HTTP header, and will not inherit to subframes.

Example HTTP header: Document-Policy: force-load-at-top=?0, lossy-images-max-bpp=1.0

• force-load-at-top is set to boolean value false (?0 in Structured Field syntax), i.e. the feature is disallowed in current document;
• lossy-images-max-bpp is set to 1.0, i.e. lossy image format (e.g. jpeg) images with byte per pixel rate higher than 1.0 will be blocked.

Adding a new feature to document policy

Shipping features behind a flag

If the additional feature is unshipped, or if the correct behaviour with document policy is undetermined, consider shipping the feature behind a runtime-enabled feature.

Define new feature

1. Document policy features are defined in third_party/blink/renderer/core/permissions_policy/document_policy_features.json5. Add the new feature, placing any runtime-enabled feature or origin trial dependencies in its “depends_on” field as described in the file's comments.

2. Append the new feature enum with a brief description as well in third_party/blink/public/mojom/permissions_policy/document_policy_feature.mojom

Integrate the feature behaviour with document policy

The most common way to check if features are enabled is ExecutionContext::IsFeatureEnabled.

Write web-platform-tests

Please add new tests to third_party/blink/web_tests/external/wpt/document-policy/.

Contacts

For more questions, please feel free to reach out to: iclelland@chromium.org (Emerita: loonybear@)