This change addresses several issues in the creation and use of EC2/S3
credentials with keystone tokens.
1. Disable altering credential owner attributes or metadata
Without this patch, an authenticated user can create an EC2 credential
for themself for a project they have a role on, then update the
credential to target a user and project completely unrelated to them. In
the worst case, this could be the admin user and a project the admin
user has a role assignment on. A token granted for an altered credential
like this would allow the user to masquerade as the victim user. This
patch ensures that when updating a credential, the new form of the
credential is one the acting user has access to: if the system admin
user is changing the credential, the new user ID or project ID could be
anything, but regular users may only change the credential to be one
that they still own.
Relatedly, when a user uses an application credential or a trust to
create an EC2 credential, keystone automatically adds the trust ID or
application credential ID as metadata in the EC2 access blob so that it
knows how the token can be scoped when it is used. Without this patch, a
user who has created a credential in this way can update the access blob
to remove or alter this metadata and escalate their privileges to be
fully authorized for the trustor's, application credential creator's, or
OAuth1 access token authorizor's privileges on the project. This patch
fixes the issue by simply disallowing updates to keystone-controlled
metadata in the credential.
2. Respect token roles when creating EC2 credentials
Without this patch, a trustee, an application credential user, or an
OAuth1 access token holder could create an EC2 credential or an
application credential using any roles the trustor, application
credential creator, or access token authorizor had on the project,
regardless of whether the creator had delegated only a limited subset of
roles. This was because the trust_id attribute of the EC2 access blob
was ignored, and no metadata for the application credential or access
token was recorded either. This change ensures that the access
delegation resource is recorded in the metadata of the EC2 credential
when created and passed to the token provider when used for
authentication so that the token provider can look up the correct roles
for the request.
Change-Id: I39d0d705839fbe31ac518ac9a82959e108cb7c1d
Closes-bug: #1872733
Closes-bug: #1872755
Closes-bug: #1872735
(cherry picked from commit 37e9907a17)
2f2736ebb2