--- layout: default navsection: architecture navmenu: Concepts title: "Permission model" ... {% comment %} Copyright (C) The Arvados Authors. All rights reserved. SPDX-License-Identifier: CC-BY-SA-3.0 {% endcomment %} There are four levels of permission: *none*, *can_read*, *can_write*, and *can_manage*. * *none* is the default state when there are no other permission grants. ** the object is not included in any list query response. ** direct queries of the object by uuid return 404 Not Found. ** Link objects require valid identifiers in @head_uuid@ and @tail_uuid@, so an attempt to create a Link that references an unreadable object will return an error indicating the object is not found. * *can_read* grants read-only access to the record. Attempting to update or delete the record returns an error. ** *can_read* does not allow a reader to see any permission grants on the object except the object's owner_uuid and the reader's own permissions. * *can_write* permits changes to the record, including changing ownership and deleting the object. ** *can_write* cannot read, create, update or delete permission links associated with the object. ** *can_write* also implies *can_read*. * *can_manage* permits the user to read, create, update and delete permission links whose @head_uuid@ is this object's @uuid@. ** *can_manage* also implies *can_write* and *can_read*. h2. Ownership All Arvados objects have an @owner_uuid@ field. Valid uuid types for @owner_uuid@ are "User" and "Group". In the case of a Group, the @group_class@ must be "project". The User or Group specified by @owner_uuid@ has *can_manage* permission on the object. This permission is one way: an object that is owned does not get any special permissions on the User or Group that owns it. To change the @owner_uuid@ field, it is necessary to have @can_write@ permission on both the current owner and the new owner. h2(#links). Permission links A permission link is a link object with: * @owner_uuid@ of the system user. * @link_class@ "permission" * @name@ one of *can_read*, *can_write*, *can_manage* or *can_login* * @head_uuid@ of some Arvados object * @tail_uuid@ of a User or Group. For Group, the @group_class@ must be a "role". This grants the permission in @name@ for @tail_uuid@ accessing @head_uuid@. If a User has *can_manage* permission on some object, the user has the ability to read, create, update and delete permission links with @head_uuid@ of the managed object. In other words, the user has the ability to modify the permission grants on the object. The *can_login* @name@ is only meaningful on a permission link with with @tail_uuid@ a user UUID and @head_uuid@ a Virtual Machine UUID. A permission link of this type gives the user UUID permission to log into the Virtual Machine UUID. The username for the VM is specified in the @properties@ field. Group membership can be specified that way as well, optionally. See the "VM login section on the 'User management at the CLI' page":{{ site.baseurl }}/admin/user-management-cli.html#vm-login for an example. h3. Transitive permissions Permissions can be obtained indirectly through nested ownership (*can_manage*) or by following multiple permission links. * If a User X owns project A, and project A owns project B, then User X *can_manage* project B. * If a User X *can_read* role A, and role A *can_read* Object B, then User X *can_read* Object B. * Permissions are narrowed to the least powerful permission on the path. ** If User X *can_write* role A, and role A *can_read* Object B, then User X *can_read* Object B. ** If User X *can_read* role A, and role A *can_write* Object B, then User X *can_read* Object B. h2. Projects and Roles A "project" is a subtype of Group that is displayed as a "Project" in Workbench, and as a directory by @arv-mount@. * A project can own things (appear in @owner_uuid@) * A project can be owned by a user or another project. * The name of a project is unique only among projects and filters with the same owner_uuid. * Projects can be targets (@head_uuid@) of permission links, but not origins (@tail_uuid@). Putting a project in a @tail_uuid@ field is an error. A "filter" is a subtype of Group that is displayed as a "Project" in Workbench, and as a directory by @arv-mount@. See "the groups API documentation":{{ site.baseurl }}/api/methods/groups.html for more information. * A filter group cannot own things (cannot appear in @owner_uuid@). Putting a filter group in an @owner_uuid@ field is an error. * A filter group can be owned by a user or a project. * The name of a filter is unique only among projects and filters with the same owner_uuid. * Filters can be targets (@head_uuid@) of permission links, but not origins (@tail_uuid@). Putting a filter in a @tail_uuid@ field is an error. A "role" is a subtype of Group that is treated in Workbench as a group of users who have permissions in common (typically an organizational group). * A role cannot own things (cannot appear in @owner_uuid@). Putting a role in an @owner_uuid@ field is an error. * All roles are owned by the system user. * The name of a role is unique across a single Arvados cluster. * Roles can be both targets (@head_uuid@) and origins (@tail_uuid@) of permission links. * By default, all roles are visible to all active users. However, if the configuration entry @Users.RoleGroupsVisibleToAll@ is @false@, visibility is determined by normal permission rules, _i.e._, a role is only visible to users who have that role, and to admins. h3. Access through Roles A "role" consists of a set of users or other roles that have that role, and a set of permissions (primarily read/write/manage access to projects) the role grants. If there is a permission link stating that user A *can_write* role R, then we say A has role R. This means user A has up to *can_write* access to everything the role has access to. Because permissions are one-way, the links A *can_write* R and B *can_write* R does not imply that user A and B will be able to see each other. For users in a role to see each other, read permission should be added going in the opposite direction: R *can_read* A and R *can_read* B. If a user needs to be able to manipulate permissions of objects that are accessed through the role (for example, to share project P with a user outside the role), then role R must have *can_manage* permission on project P (R *can_manage* P) and the user must be granted *can_manage* permission on R (A *can_manage* R). h2. Special cases Log table objects are additionally readable based on whether the User has *can_read* permission on @object_uuid@ (User can access log history about objects it can read). To retain the integrity of the log, the log table denies all update or delete operations. Permission links where @tail_uuid@ is a User allow *can_read* on the link record by that user (User can discover her own permission grants.) At least *can_read* on a Collection grants permission to read the blocks that make up the collection (API server returns signed blocks). A user can only read a container record if the user has read permission to a container_request with that container_uuid. *can_read* and *can_write* access on a user grants access to the user record, but not anything owned by the user. *can_manage* access to a user grants can_manage access to the user, _and everything owned by that user_ . If a user A *can_read* role R, and role R *can_manage* user B, then user A *can_read* user B _and everything owned by that user_ . h2(#system). System user and group A privileged user account exists for the use by internal Arvados components. This user manages system objects which should not be "owned" by any particular user. The system user uuid is @{siteprefix}-tpzed-000000000000000@. h2. Anoymous user and group An Arvados site may be configured to allow users to browse resources without requiring a login. In this case, permissions for non-logged-in users are associated with the "anonymous" user. To make objects visible to anyone (both logged-in and non-logged-in users), they can be shared with the "anonymous" role. Note that objects shared with the "anonymous" user will only be visible to non-logged-in users! The anonymous user uuid is @{siteprefix}-tpzed-anonymouspublic@. The anonymous group uuid is @{siteprefix}-j7d0g-anonymouspublic@. h2. Example !(full-width){{site.baseurl}}/images/Arvados_Permissions.svg!