registry: add reference (#22497)

<!--Delete sections as needed -->

## Description

Re-add registry reference from point in time of deletion at
https://github.com/docker/docs/pull/18390, not upstream.


https://deploy-preview-22497--docsdocker.netlify.app/reference/api/registry/latest/

https://deploy-preview-22497--docsdocker.netlify.app/reference/api/registry/auth/

## Related issues or tickets

ENGDOCS-2577

## Reviews

<!-- Notes for reviewers here -->
<!-- List applicable reviews (optionally @tag reviewers) -->

- [ ] Technical review
- [ ] Editorial review
- [ ] Product review

---------

Signed-off-by: Craig <craig.osterhout@docker.com>
Co-authored-by: sheltongraves <148902861+sheltongraves@users.noreply.github.com>
Co-authored-by: Sarah Sanders <sarah.sanders@docker.com>

content/reference/_index.md

@@ -42,6 +42,10 @@ params:
     description: API for Docker Verified Publishers to fetch analytics data.
     icon: area_chart
     link: /reference/api/hub/dvp/
+  - title: Registry API
+    description: API for Docker Registry.
+    icon: database
+    link: /reference/api/registry/latest/
 ---
 
 This section includes the reference documentation for the Docker platform's

content/reference/api/registry/_index.md

@@ -0,0 +1,5 @@
+---
+title: Registry API
+build:
+  render: never
+---

content/reference/api/registry/auth.md

@@ -0,0 +1,221 @@
+---
+title: Registry authentication
+description: "Specifies the Docker Registry v2 authentication"
+keywords: registry, images, tags, repository, distribution, Bearer authentication, advanced
+---
+
+This document outlines the registry authentication scheme:
+
+![v2 registry auth](./images/v2-registry-auth.png)
+
+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 want 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:
+
+```text
+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:
+
+```text
+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
+
+Defines getting a bearer and refresh token using the token endpoint.
+
+### Query parameters
+
+#### `service`
+
+The name of the service which hosts the resource.
+
+#### `offline_token`
+
+Whether to return a refresh token along with the bearer token. A refresh token
+is capable of getting additional bearer tokens for the same subject with
+different scopes. The refresh token does not have an expiration and should be
+considered completely opaque to the client.
+
+#### `client_id`
+
+String identifying the client. This `client_id` does not need to be registered
+with the authorization server but should be set to a meaningful value in order
+to allow auditing keys created by unregistered clients. Accepted syntax is
+defined in [RFC6749 Appendix
+A.1](https://tools.ietf.org/html/rfc6749#appendix-A.1).
+
+#### `scope`
+
+The resource in question, formatted as one of the space-delimited entries from
+the `scope` parameters from the `WWW-Authenticate` header shown previously. This
+query parameter should be specified multiple times if there is more than one
+`scope` entry from the `WWW-Authenticate` header. The previous example would be
+specified as: `scope=repository:samalba/my-app:push`. The scope field may be
+empty to request a refresh token without providing any resource permissions to
+the returned bearer token.
+
+### Token response fields
+
+#### `token`
+
+An opaque `Bearer` token that clients should supply to subsequent
+requests in the `Authorization` header.
+
+#### `access_token`
+
+For compatibility with OAuth 2.0, the `token` under the name `access_token` is
+also accepted.  At least one of these fields must be specified, but both may
+also appear (for compatibility with older clients).  When both are specified,
+they should be equivalent; if they differ the client's choice is undefined.
+
+#### `expires_in`
+
+(Optional) The duration in seconds since the token was issued that it will
+remain valid. When omitted, this defaults to 60 seconds. For compatibility
+with older clients, a token should never be returned with less than 60 seconds
+to live.
+
+#### `issued_at`
+
+(Optional) The [RFC3339](https://www.ietf.org/rfc/rfc3339.txt)-serialized UTC
+standard time at which a given token was issued. If `issued_at` is omitted, the
+expiration is from when the token exchange completed.
+
+#### `refresh_token`
+
+(Optional) Token which can be used to get additional access tokens for
+the same subject with different scopes. This token should be kept secure
+by the client and only sent to the authorization server which issues
+bearer tokens. This field will only be set when `offline_token=true` is
+provided in the request.
+
+### Example
+
+For this example, the client makes an HTTP GET request to the following URL:
+
+```text
+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. From Docker 1.11 the
+Docker Engine supports both Basic Authentication and OAuth2 for
+getting tokens. Docker 1.10 and before, the registry client in the Docker Engine
+only supports Basic Authentication. 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 (within the indicated window of time):
+
+```text
+HTTP/1.1 200 OK
+Content-Type: application/json
+
+{"token": "eyJ0eXAiOiJKV1QiLCJhbGciOiJFUzI1NiIsImtpZCI6IlBZWU86VEVXVTpWN0pIOjI2SlY6QVFUWjpMSkMzOlNYVko6WEdIQTozNEYyOjJMQVE6WlJNSzpaN1E2In0.eyJpc3MiOiJhdXRoLmRvY2tlci5jb20iLCJzdWIiOiJqbGhhd24iLCJhdWQiOiJyZWdpc3RyeS5kb2NrZXIuY29tIiwiZXhwIjoxNDE1Mzg3MzE1LCJuYmYiOjE0MTUzODcwMTUsImlhdCI6MTQxNTM4NzAxNSwianRpIjoidFlKQ08xYzZjbnl5N2tBbjBjN3JLUGdiVjFIMWJGd3MiLCJhY2Nlc3MiOlt7InR5cGUiOiJyZXBvc2l0b3J5IiwibmFtZSI6InNhbWFsYmEvbXktYXBwIiwiYWN0aW9ucyI6WyJwdXNoIl19XX0.QhflHPfbd6eVF4lM9bwYpFZIV0PfikbyXuLx959ykRTBpe3CYnzs6YBK8FToVb5R47920PVLrh8zuLzdCr9t3w", "expires_in": 3600,"issued_at": "2009-11-10T23:00:00Z"}
+```
+
+## 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:
+
+```text
+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)

content/reference/api/registry/latest.md

@@ -0,0 +1,7 @@
+---
+layout: api
+title: Supported registry API for Docker Hub
+linktitle: Latest
+description: "Supported registry API endpoints."
+keywords: registry, on-prem, images, tags, repository, distribution, api, advanced
+---