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GitLab

Implementing permissions

There are multiple types of permissions across GitLab, and when implementing anything that deals with permissions, all of them should be considered.

Instance

User types

Each user can be one of the following types:

  • Regular.
  • External - access to groups and projects only if direct member.
  • Internal users - system created.
  • Auditor:
    • No access to projects or groups settings menu.
    • No access to Admin Area.
    • Read-only access to everything else.
  • Administrator - read-write access.

See the permissions page for details on how each user type is used.

Groups and Projects

General permissions

Groups and projects can have the following visibility levels:

  • public (20) - an entity is visible to everyone
  • internal (10) - an entity is visible to logged in users
  • private (0) - an entity is visible only to the approved members of the entity

By default, subgroups can not have higher visibility levels. For example, if you create a new private group, it can not include a public subgroup.

The visibility level of a group can be changed only if all subgroups and sub-projects have the same or lower visibility level. For example, a group can be set to internal only if all subgroups and projects are internal or private.

WARNING: If you migrate an existing group to a lower visibility level, that action does not migrate subgroups in the same way. This is a known issue.

Visibility levels can be found in the Gitlab::VisibilityLevel module.

Feature specific permissions

Additionally, the following project features can have different visibility levels:

  • Issues
  • Repository
    • Merge request
    • Forks
    • Pipelines
  • Analytics
  • Requirements
  • Security & Compliance
  • Wiki
  • Snippets
  • Pages
  • Operations
  • Metrics Dashboard

These features can be set to "Everyone with Access" or "Only Project Members". They make sense only for public or internal projects because private projects can be accessed only by project members by default.

Members

Users can be members of multiple groups and projects. The following access levels are available (defined in the Gitlab::Access module):

  • No access (0)
  • Minimal access (5)
  • Guest (10)
  • Reporter (20)
  • Developer (30)
  • Maintainer (40)
  • Owner (50)

If a user is the member of both a project and the project parent group(s), the higher permission is taken into account for the project.

If a user is the member of a project, but not the parent group(s), they can still view the groups and their entities (like epics).

Project membership (where the group membership is already taken into account) is stored in the project_authorizations table.

WARNING: Due to an issue, projects in personal namespace do not show owner (50) permission in project_authorizations table. Note however that user.owned_projects is calculated properly.

Confidential issues

Confidential issues can be accessed only by project members who are at least reporters (they can't be accessed by guests). Additionally they can be accessed by their authors and assignees.

Licensed features

Some features can be accessed only if the user has the correct license plan.

Permission dependencies

Feature policies can be quite complex and consist of multiple rules. Quite often, one permission can be based on another.

Designing good permissions means reusing existing permissions as much as possible and making access to features granular.

In the case of a complex resource, it should be broken into smaller pieces of information and each piece should be granted a different permission.

A good example in this case is the Merge Request widget and the Security reports. Depending on the visibility level of the Pipelines, the Security reports are either visible in the widget or not. So, the Merge Request widget, the Pipelines, and the Security reports, have separate permissions. Moreover, the permissions for the Merge Request widget and the Pipelines are dependencies of the Security reports.

Permission dependencies of Secure features

Secure features have complex permissions since these features are integrated into different features like Merge Requests and CI flow.

Here is a list of some permission dependencies.

Activity level Resource Locations Permission dependency
View License information Dependency list, License Compliance Can view repository
View Dependency information Dependency list, License Compliance Can view repository
View Vulnerabilities information Dependency list Can view security findings
View Black/Whitelisted licenses for the project License Compliance, merge request Can view repository
View Security findings merge request, CI job page, Pipeline security tab Can read the project and CI jobs
View Vulnerability feedback merge request Can read security findings
View Dependency List page Project Can access Dependency information
View License Compliance page Project Can access License information

Where should permissions be checked?

By default, controllers, API endpoints, and GraphQL types/fields are responsible for authorization. See Secure Coding Guidelines > Permissions.

Considerations

  • Many actions are completely or partially extracted to services, finders, and other classes, so it is normal to do permission checks "downstream".
  • Often, authorization logic must be incorporated in DB queries to filter records.
  • DeclarativePolicy rules are relatively performant, but conditions may perform database calls.
  • Multiple permission checks across layers can be difficult to reason about, which is its own security risk. For example, duplicate authorization logic could diverge.
  • Should we apply defense-in-depth with permission checks? Join the discussion

Tips

If a class accepts current_user, then it may be responsible for authorization.

Example: Adding a new API endpoint

By default, we authorize at the endpoint. Checking an existing ability may make sense; if not, then we probably need to add one.

As an aside, most endpoints can be cleanly categorized as a CRUD (create, read, update, destroy) action on a resource. The services and abilities follow suit, which is why many are named like Projects::CreateService or :read_project.

Say, for example, we extract the whole endpoint into a service. The can? check will now be in the service. Say the service reuses an existing finder, which we are modifying for our purposes. Should we make the finder check an ability?

  • If the finder doesn't accept current_user, and therefore doesn't check permissions, then probably no.
  • If the finder accepts current_user, and doesn't check permissions, then it would be a good idea to double check other usages of the finder, and we might consider adding authorization.
  • If the finder accepts current_user, and already checks permissions, then either we need to add our case, or the existing checks are appropriate.