148 lines
6.9 KiB
Markdown
148 lines
6.9 KiB
Markdown
---
|
|
title: "Token Scope Documentation"
|
|
description: "Describes the scope and access fields used for registry authorization tokens"
|
|
keywords: registry, on-prem, images, tags, repository, distribution, advanced, access, scope
|
|
---
|
|
|
|
# Docker Registry Token Scope and Access
|
|
|
|
Tokens used by the registry are always restricted what resources they may
|
|
be used to access, where those resources may be accessed, and what actions
|
|
may be done on those resources. Tokens always have the context of a user which
|
|
the token was originally created for. This document describes how these
|
|
restrictions are represented and enforced by the authorization server and
|
|
resource providers.
|
|
|
|
## Scope Components
|
|
|
|
### Subject (Authenticated User)
|
|
|
|
The subject represents the user for which a token is valid. Any actions
|
|
performed using an access token should be considered on behalf of the subject.
|
|
This is included in the `sub` field of access token JWT. A refresh token should
|
|
be limited to a single subject and only be able to give out access tokens for
|
|
that subject.
|
|
|
|
### Audience (Resource Provider)
|
|
|
|
The audience represents a resource provider which is intended to be able to
|
|
perform the actions specified in the access token. Any resource provider which
|
|
does not match the audience should not use that access token. The audience is
|
|
included in the `aud` field of the access token JWT. A refresh token should be
|
|
limited to a single audience and only be able to give out access tokens for that
|
|
audience.
|
|
|
|
### Resource Type
|
|
|
|
The resource type represents the type of resource which the resource name is
|
|
intended to represent. This type may be specific to a resource provider but must
|
|
be understood by the authorization server in order to validate the subject
|
|
is authorized for a specific resource.
|
|
|
|
#### Resource Class
|
|
|
|
The resource type might have a resource class which further classifies the
|
|
the resource name within the resource type. A class is not required and
|
|
is specific to the resource type.
|
|
|
|
#### Example Resource Types
|
|
|
|
- `repository` - represents a single repository within a registry. A
|
|
repository may represent many manifest or content blobs, but the resource type
|
|
is considered the collections of those items. Actions which may be performed on
|
|
a `repository` are `pull` for accessing the collection and `push` for adding to
|
|
it. By default the `repository` type has the class of `image`.
|
|
- `repository(plugin)` - represents a single repository of plugins within a
|
|
registry. A plugin repository has the same content and actions as a repository.
|
|
- `registry` - represents the entire registry. Used for administrative actions
|
|
or lookup operations that span an entire registry.
|
|
|
|
### Resource Name
|
|
|
|
The resource name represent the name which identifies a resource for a resource
|
|
provider. A resource is identified by this name and the provided resource type.
|
|
An example of a resource name would be the name component of an image tag, such
|
|
as "samalba/myapp" or "hostname/samalba/myapp".
|
|
|
|
### Resource Actions
|
|
|
|
The resource actions define the actions which the access token allows to be
|
|
performed on the identified resource. These actions are type specific but will
|
|
normally have actions identifying read and write access on the resource. Example
|
|
for the `repository` type are `pull` for read access and `push` for write
|
|
access.
|
|
|
|
## Authorization Server Use
|
|
|
|
Each access token request may include a scope and an audience. The subject is
|
|
always derived from the passed in credentials or refresh token. When using
|
|
a refresh token the passed in audience must match the audience defined for
|
|
the refresh token. The audience (resource provider) is provided using the
|
|
`service` field. Multiple resource scopes may be provided using multiple `scope`
|
|
fields on the `GET` request. The `POST` request only takes in a single
|
|
`scope` field but may use a space to separate a list of multiple resource
|
|
scopes.
|
|
|
|
### Resource Scope Grammar
|
|
|
|
```
|
|
scope := resourcescope [ ' ' resourcescope ]*
|
|
resourcescope := resourcetype ":" resourcename ":" action [ ',' action ]*
|
|
resourcetype := resourcetypevalue [ '(' resourcetypevalue ')' ]
|
|
resourcetypevalue := /[a-z0-9]+/
|
|
resourcename := [ hostname '/' ] component [ '/' component ]*
|
|
hostname := hostcomponent ['.' hostcomponent]* [':' port-number]
|
|
hostcomponent := /([a-zA-Z0-9]|[a-zA-Z0-9][a-zA-Z0-9-]*[a-zA-Z0-9])/
|
|
port-number := /[0-9]+/
|
|
action := /[a-z]*/
|
|
component := alpha-numeric [ separator alpha-numeric ]*
|
|
alpha-numeric := /[a-z0-9]+/
|
|
separator := /[_.]|__|[-]*/
|
|
```
|
|
Full reference grammar is defined
|
|
[here](https://godoc.org/github.com/docker/distribution/reference). Currently
|
|
the scope name grammar is a subset of the reference grammar.
|
|
|
|
> **NOTE:** that the `resourcename` may contain one `:` due to a possible port
|
|
> number in the hostname component of the `resourcename`, so a naive
|
|
> implementation that interprets the first three `:`-delimited tokens of a
|
|
> `scope` to be the `resourcetype`, `resourcename`, and a list of `action`
|
|
> would be insufficient.
|
|
|
|
## Resource Provider Use
|
|
|
|
Once a resource provider has verified the authenticity of the scope through
|
|
JWT access token verification, the resource provider must ensure that scope
|
|
satisfies the request. The resource provider should match the given audience
|
|
according to name or URI the resource provider uses to identify itself. Any
|
|
denial based on subject is not defined here and is up to resource provider, the
|
|
subject is mainly provided for audit logs and any other user-specific rules
|
|
which may need to be provided but are not defined by the authorization server.
|
|
|
|
The resource provider must ensure that ANY resource being accessed as the
|
|
result of a request has the appropriate access scope. Both the resource type
|
|
and resource name must match the accessed resource and an appropriate action
|
|
scope must be included.
|
|
|
|
When appropriate authorization is not provided either due to lack of scope
|
|
or missing token, the resource provider to return a `WWW-AUTHENTICATE` HTTP
|
|
header with the `realm` as the authorization server, the `service` as the
|
|
expected audience identifying string, and a `scope` field for each required
|
|
resource scope to complete the request.
|
|
|
|
## JWT Access Tokens
|
|
|
|
Each JWT access token may only have a single subject and audience but multiple
|
|
resource scopes. The subject and audience are put into standard JWT fields
|
|
`sub` and `aud`. The resource scope is put into the `access` field. The
|
|
structure of the access field can be seen in the
|
|
[jwt documentation](jwt.md).
|
|
|
|
## Refresh Tokens
|
|
|
|
A refresh token must be defined for a single subject and audience. Further
|
|
restricting scope to specific type, name, and actions combinations should be
|
|
done by fetching an access token using the refresh token. Since the refresh
|
|
token is not scoped to specific resources for an audience, extra care should
|
|
be taken to only use the refresh token to negotiate new access tokens directly
|
|
with the authorization server, and never with a resource provider.
|