Access control lists (ACLs)

Yandex Cloud uses two independent mechanisms for managing access to Object Storage resources:

• Identity and Access Management.
• An Object Storage ACL is a list of permissions for each object and bucket and is stored directly in Object Storage.

When receiving a request to a bucket or object, Object Storage checks access permissions through both mechanisms. If the required access is granted from either method, Object Storage executes the request. Permissions granted to a bucket apply to all of the objects it contains. With ACLs, you can extend access permissions to individual objects.

For example, if users have the viewer role in IAM for the bucket's folder, they can view its contents even if it isn't reflected in the bucket ACL.

By default, Object Storage creates an empty ACL for each new object or bucket. Users with the appropriate access rights can edit and upload ACLs for Object Storage buckets and objects.

You can use ACLs to grant permissions to Yandex Cloud users, service accounts, and system groups. To do this, you need to know the permission recipient's ID. When granting permissions, you can use predefined ACLs, which contain common permission sets.

To view the ACL structure, see ACL XML schema. You can set up to 100 rules per ACL.

Permission recipient ID

• User Yandex Cloud

  You can get the ID in the following ways:

  • In the IAM section of the management console.
  • Using the CLI or CLIIAM.

• Service account.

  To get the ID, go to the Service accounts section in the management console.

• System groups

  Use the system group URI to grant permissions.

ACL operations

• In the management console, you can edit ACLs for buckets and objects.

• Using an Amazon S3-compatible API, you can upload or download ACLs for buckets or objects.

  You can't delete ACLs. To remove all access permissions, upload an empty ACL.

Permission types

Permissions correspond to user roles in IAM.

Predefined ACLs

Predefined ACLs can be applied to both objects and buckets. When applied to an object, the public-read-write ACL is the same as public-read.

You can upload a predefined ACL using only an Amazon S3-compatible HTTP API. When uploading an ACL, use the X-Amz-Acl HTTP header.

System groups

AllUsers

Includes all internet users.

Permission for AllUsers looks like this:

<Grantee xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:type="Group">
    <URI>http://acs.amazonaws.com/groups/global/AllUsers</URI>
</Grantee>

AuthenticatedUsers

Includes all authenticated Yandex Cloud users: both from your clouds and other users' clouds.

Permission for AuthenticatedUsers looks like this:

<Grantee xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:type="Group">
    <URI>http://acs.amazonaws.com/groups/global/AuthenticatedUsers</URI>
</Grantee>

Inheritance of bucket access rights by system groups Yandex Cloud

A bucket inherits the same access rights in the IAM service as those of the folder and cloud where it's located. If users have access rights to the folder or cloud that the bucket belongs to, they'll also have access to the bucket itself.

How to view bucket access rights inherited from folders

A bucket inherits access rights from its folder. If you want to know exactly what access rights your bucket inherited, get a list of roles for the folder. You can also revoke these roles at any time.

• To get a list of folder roles, run the command:

  yc resource-manager folder list-access-bindings \
    --id b1g7gvsi89m34qmcm4ke
  

  Result:

  +---------+--------------+-----------------------+
  | ROLE ID | SUBJECT TYPE |      SUBJECT ID       |
  +---------+--------------+-----------------------+
  | viewer  | system       | allAuthenticatedUsers |
  | viewer  | system       | allUsers              |
  +---------+--------------+-----------------------+
  

  The output contains allAuthenticatedUsers and allUsers. This means that users of these groups are granted rights for this folder and all resources contained in it, including buckets.

• To revoke a role from the allAuthenticatedUsers system group, run the command:

  yc resource-manager folder remove-access-binding \
    --id b1g7gvsi89m34qmcm4ke \
    --role viewer \
    --allAuthenticatedUsers
  

• To revoke a role from the allUsers system group, run the command:

  yc resource-manager folder remove-access-binding \
    --id b1g7gvsi89m34qmcm4ke \
    --role viewer \
    --allUsers