ca7c845dc0
Split the discussion of v2 authentication into two parts: 1) A specification of the handshake between the client, registry and authentication service. 2) A description of how `docker/distribution` implements this using JWT. This should make it clearer that `#2` is an implementation detail, and that clients should regard tokens as opaque entities that only the registry and authentication service should understand. Signed-off-by: Matt Moore <mattmoor@google.com>
180 lines
8.8 KiB
Markdown
180 lines
8.8 KiB
Markdown
<!--[metadata]>
|
|
+++
|
|
title = "Token Authentication Specification"
|
|
description = "Specifies the Docker Registry v2 authentication"
|
|
keywords = ["registry, on-prem, images, tags, repository, distribution, Bearer authentication, advanced"]
|
|
[menu.main]
|
|
parent="smn_registry_ref"
|
|
+++
|
|
<![end-metadata]-->
|
|
|
|
# Docker Registry v2 authentication via central service
|
|
|
|
This document outlines the v2 Docker registry authentication scheme:
|
|
|
|
|
|
|
|
1. Attempt to begin a push/pull operation with the registry.
|
|
2. If the registry requires authorization it will return a `401 Unauthorized`
|
|
HTTP response with information on how to authenticate.
|
|
3. The registry client makes a request to the authorization service for a
|
|
Bearer token.
|
|
4. The authorization service returns an opaque Bearer token representing the
|
|
client's authorized access.
|
|
5. The client retries the original request with the Bearer token embedded in
|
|
the request's Authorization header.
|
|
6. The Registry authorizes the client by validating the Bearer token and the
|
|
claim set embedded within it and begins the push/pull session as usual.
|
|
|
|
## Requirements
|
|
|
|
- Registry clients which can understand and respond to token auth challenges
|
|
returned by the resource server.
|
|
- An authorization server capable of managing access controls to their
|
|
resources hosted by any given service (such as repositories in a Docker
|
|
Registry).
|
|
- A Docker Registry capable of trusting the authorization server to sign tokens
|
|
which clients can use for authorization and the ability to verify these
|
|
tokens for single use or for use during a sufficiently short period of time.
|
|
|
|
## Authorization Server Endpoint Descriptions
|
|
|
|
The described server is meant to serve as a standalone access control manager
|
|
for resources hosted by other services which wish to authenticate and manage
|
|
authorizations using a separate access control manager.
|
|
|
|
A service like this is used by the official Docker Registry to authenticate
|
|
clients and verify their authorization to Docker image repositories.
|
|
|
|
As of Docker 1.6, the registry client within the Docker Engine has been updated
|
|
to handle such an authorization workflow.
|
|
|
|
## How to authenticate
|
|
|
|
Registry V1 clients first contact the index to initiate a push or pull. Under
|
|
the Registry V2 workflow, clients should contact the registry first. If the
|
|
registry server requires authentication it will return a `401 Unauthorized`
|
|
response with a `WWW-Authenticate` header detailing how to authenticate to this
|
|
registry.
|
|
|
|
For example, say I (username `jlhawn`) am attempting to push an image to the
|
|
repository `samalba/my-app`. For the registry to authorize this, I will need
|
|
`push` access to the `samalba/my-app` repository. The registry will first
|
|
return this response:
|
|
|
|
```
|
|
HTTP/1.1 401 Unauthorized
|
|
Content-Type: application/json; charset=utf-8
|
|
Docker-Distribution-Api-Version: registry/2.0
|
|
Www-Authenticate: Bearer realm="https://auth.docker.io/token",service="registry.docker.io",scope="repository:samalba/my-app:pull,push"
|
|
Date: Thu, 10 Sep 2015 19:32:31 GMT
|
|
Content-Length: 235
|
|
Strict-Transport-Security: max-age=31536000
|
|
|
|
{"errors":[{"code":"UNAUTHORIZED","message":"access to the requested resource is not authorized","detail":[{"Type":"repository","Name":"samalba/my-app","Action":"pull"},{"Type":"repository","Name":"samalba/my-app","Action":"push"}]}]}
|
|
```
|
|
|
|
Note the HTTP Response Header indicating the auth challenge:
|
|
|
|
```
|
|
Www-Authenticate: Bearer realm="https://auth.docker.io/token",service="registry.docker.io",scope="repository:samalba/my-app:pull,push"
|
|
```
|
|
|
|
This format is documented in [Section 3 of RFC 6750: The OAuth 2.0 Authorization Framework: Bearer Token Usage](https://tools.ietf.org/html/rfc6750#section-3)
|
|
|
|
This challenge indicates that the registry requires a token issued by the
|
|
specified token server and that the request the client is attempting will
|
|
need to include sufficient access entries in its claim set. To respond to this
|
|
challenge, the client will need to make a `GET` request to the URL
|
|
`https://auth.docker.io/token` using the `service` and `scope` values from the
|
|
`WWW-Authenticate` header.
|
|
|
|
## Requesting a Token
|
|
|
|
#### Query Parameters
|
|
|
|
<dl>
|
|
<dt>
|
|
<code>service</code>
|
|
</dt>
|
|
<dd>
|
|
The name of the service which hosts the resource.
|
|
</dd>
|
|
<dt>
|
|
<code>scope</code>
|
|
</dt>
|
|
<dd>
|
|
The resource in question, formatted as one of the space-delimited
|
|
entries from the <code>scope</code> parameters from the <code>WWW-Authenticate</code> header
|
|
shown above. This query parameter should be specified multiple times if
|
|
there is more than one <code>scope</code> entry from the <code>WWW-Authenticate</code>
|
|
header. The above example would be specified as:
|
|
<code>scope=repository:samalba/my-app:push</code>.
|
|
</dd>
|
|
</dl>
|
|
|
|
#### Example
|
|
|
|
For this example, the client makes an HTTP GET request to the following URL:
|
|
|
|
```
|
|
https://auth.docker.io/token?service=registry.docker.io&scope=repository:samalba/my-app:pull,push
|
|
```
|
|
|
|
The token server should first attempt to authenticate the client using any
|
|
authentication credentials provided with the request. As of Docker 1.8, the
|
|
registry client in the Docker Engine only supports Basic Authentication to
|
|
these token servers. If an attempt to authenticate to the token server fails,
|
|
the token server should return a `401 Unauthorized` response indicating that
|
|
the provided credentials are invalid.
|
|
|
|
Whether the token server requires authentication is up to the policy of that
|
|
access control provider. Some requests may require authentication to determine
|
|
access (such as pushing or pulling a private repository) while others may not
|
|
(such as pulling from a public repository).
|
|
|
|
After authenticating the client (which may simply be an anonymous client if
|
|
no attempt was made to authenticate), the token server must next query its
|
|
access control list to determine whether the client has the requested scope. In
|
|
this example request, if I have authenticated as user `jlhawn`, the token
|
|
server will determine what access I have to the repository `samalba/my-app`
|
|
hosted by the entity `registry.docker.io`.
|
|
|
|
Once the token server has determined what access the client has to the
|
|
resources requested in the `scope` parameter, it will take the intersection of
|
|
the set of requested actions on each resource and the set of actions that the
|
|
client has in fact been granted. If the client only has a subset of the
|
|
requested access **it must not be considered an error** as it is not the
|
|
responsibility of the token server to indicate authorization errors as part of
|
|
this workflow.
|
|
|
|
Continuing with the example request, the token server will find that the
|
|
client's set of granted access to the repository is `[pull, push]` which when
|
|
intersected with the requested access `[pull, push]` yields an equal set. If
|
|
the granted access set was found only to be `[pull]` then the intersected set
|
|
would only be `[pull]`. If the client has no access to the repository then the
|
|
intersected set would be empty, `[]`.
|
|
|
|
It is this intersected set of access which is placed in the returned token.
|
|
|
|
The server then constructs an implementation-specific token with this
|
|
intersected set of access, and returns it to the Docker client to use to
|
|
authenticate to the audience service:
|
|
|
|
```
|
|
HTTP/1.1 200 OK
|
|
Content-Type: application/json
|
|
|
|
{"token": "eyJ0eXAiOiJKV1QiLCJhbGciOiJFUzI1NiIsImtpZCI6IlBZWU86VEVXVTpWN0pIOjI2SlY6QVFUWjpMSkMzOlNYVko6WEdIQTozNEYyOjJMQVE6WlJNSzpaN1E2In0.eyJpc3MiOiJhdXRoLmRvY2tlci5jb20iLCJzdWIiOiJqbGhhd24iLCJhdWQiOiJyZWdpc3RyeS5kb2NrZXIuY29tIiwiZXhwIjoxNDE1Mzg3MzE1LCJuYmYiOjE0MTUzODcwMTUsImlhdCI6MTQxNTM4NzAxNSwianRpIjoidFlKQ08xYzZjbnl5N2tBbjBjN3JLUGdiVjFIMWJGd3MiLCJhY2Nlc3MiOlt7InR5cGUiOiJyZXBvc2l0b3J5IiwibmFtZSI6InNhbWFsYmEvbXktYXBwIiwiYWN0aW9ucyI6WyJwdXNoIl19XX0.QhflHPfbd6eVF4lM9bwYpFZIV0PfikbyXuLx959ykRTBpe3CYnzs6YBK8FToVb5R47920PVLrh8zuLzdCr9t3w"}
|
|
```
|
|
|
|
## Using the Bearer token
|
|
|
|
Once the client has a token, it will try the registry request again with the
|
|
token placed in the HTTP `Authorization` header like so:
|
|
|
|
```
|
|
Authorization: Bearer eyJ0eXAiOiJKV1QiLCJhbGciOiJFUzI1NiIsImtpZCI6IkJWM0Q6MkFWWjpVQjVaOktJQVA6SU5QTDo1RU42Ok40SjQ6Nk1XTzpEUktFOkJWUUs6M0ZKTDpQT1RMIn0.eyJpc3MiOiJhdXRoLmRvY2tlci5jb20iLCJzdWIiOiJCQ0NZOk9VNlo6UUVKNTpXTjJDOjJBVkM6WTdZRDpBM0xZOjQ1VVc6NE9HRDpLQUxMOkNOSjU6NUlVTCIsImF1ZCI6InJlZ2lzdHJ5LmRvY2tlci5jb20iLCJleHAiOjE0MTUzODczMTUsIm5iZiI6MTQxNTM4NzAxNSwiaWF0IjoxNDE1Mzg3MDE1LCJqdGkiOiJ0WUpDTzFjNmNueXk3a0FuMGM3cktQZ2JWMUgxYkZ3cyIsInNjb3BlIjoiamxoYXduOnJlcG9zaXRvcnk6c2FtYWxiYS9teS1hcHA6cHVzaCxwdWxsIGpsaGF3bjpuYW1lc3BhY2U6c2FtYWxiYTpwdWxsIn0.Y3zZSwaZPqy4y9oRBVRImZyv3m_S9XDHF1tWwN7mL52C_IiA73SJkWVNsvNqpJIn5h7A2F8biv_S2ppQ1lgkbw
|
|
```
|
|
|
|
This is also described in [Section 2.1 of RFC 6750: The OAuth 2.0 Authorization Framework: Bearer Token Usage](https://tools.ietf.org/html/rfc6750#section-2.1)
|