Registry-Auth

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Registry-Auth providers authentication and authorization for Docker Registry.

Docker Registry can be configurated with three kinds of authentications:

• silly which is only appropriate for development. It simply checks for the existence of the Authorization header in the HTTP request. It does not check the header’s value.

• htpasswd which supports username and password authentication. Docker Registry loads the htpasswd config once when startup. The htpasswd only resolves the authentication problem, but can not provide authorizations.

• token which supports authentication and authorization. It takes the JWT format including the token's validation period and authorized actions. You can set each repository's accessibilities for users.

  For example, user test1 can only pull from repository repo1, while user test2 can push and pull from repository repo2.

• Besides mentioned above, there is a proxy authentication method described in Docker's deploying document. A proxy will be deployed before the Docker Registry, which can process the authentication.

  The references about the proxy are here:

  1. https://docs.docker.com/registry/deploying/#more-advanced-authentication
  2. https://docs.docker.com/registry/recipes/apache/
  3. https://docs.docker.com/registry/recipes/nginx/

Registry-auth has implemented the token and the proxy authentication.

Quick Start

The following script will run a simple Registry-Auth and Docker Registry service. It then tests the docker login and pushes and pulls images.

  curl https://raw.githubusercontent.com/alauda/registry-auth/main/scripts/quick-start.sh | bash

The Token Authentication

When using the token authentication, the Registry-Auth and the Docker Registry will use the same x509 certificate to sign and verify the token. The token is signed by the Registry-Auth and will be verified by the Docker Registry.

When the client (such as docker, containerd, etc.) accesses the Docker Registry firstly, the token does not exist in the HTTP headers. The Docker Registry will respond with an authentication fail with status code 401, and the "WWW-Authenticate" header is added in the response, which includes the Registry-Auth's URL.

Then the client will send the username and password to Registry-Auth by the Basic Authorization method for a valid token. The Registry-Auth will check the username and password and also the user's authorized repositories. After all the checks are passed, it will sign a token for the client.

The client then accesses the Docker Registry secondly with the token. And the Docker Registry will respond with the image content after validating the token.

The sequence of token authentication is here:

    sequenceDiagram;
      participant c as client
      participant r as Docker Registry
      participant ra as Registry-Auth
      c->>+r: request image
      r->>-c: 401 with Registry-Auth URL
      c->>+ra: request token by username/password
      ra->>ra: authenticate and authorize
      ra->>-c: response with token
      c->>+r: request image with token
      r->>r: validate token
      r->>-c: response with image

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The Proxy Authentication

The Registry-Auth's proxy authentication works with token authentication. The Registry-Auth is deployed before the Docker Registry as a proxy, but token authentication is also taken between Registry-Auth and Docker Registry. When using proxy authentication, only one access endpoint is needed, which will simplify the deployment and reduce the client's requests.

When the client access Registry-Auth (also the Docker Registry) with the Basic Authorization header, the Registry-Auth will check the username and password and also the user's authorized repositories, and then sign a token. The token is transmitted to the Docker Registry with the origin request.

The Docker Registry will respond with the image content after validating the token.

The sequence of proxy authentication is here:

    sequenceDiagram;
      participant c as client
      participant ra as Registry-Auth
      participant r as Docker Registry
      c->>+ra: request image with username/password
      ra->>ra: authenticate and authorize
      ra->>ra: generate token
      ra->>+r: request image with token
      r->>r: validate token
      r->>-ra: response with image
      ra->>-c: response with image

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Configurations

Registry-auth can load a config file set by the argument --auth-config-file. The config file contains the usernames, passwords and authorizations for repositories.

The format and example of the configuration are here:

  users:
    user1: password1           # use the plaintext password for user1
    # use the bcrypt encrypted password, the password can be generated by command: `htpasswd -nbB user2 password2`
    user2: $2y$05$o.txf8NBl17CimmIKybYYe9SmIcAzctQ84.UbFCObPFxt78W1DEJW
  auths:
    user1:                     # user1's configs
    - target: usersrepo/test1  # repository name
      actions:                 # allowed actions
      - pull
      - push
    - target: team1repo/.*     # use regexp to match repository name
      useRegexp: true          # stands for the regexp will be used
      actions:
      - pull
    _anonymous:                # the configs for anonymous user, the anonymous user need not provide username and password to login
    - target: .*
      useRegexp: true
      actions:
      - pull

Registry-auth can load configurations from Kubernetes secrets through the arguments --auth-config-selector, --auth-config-selector and --kubeconfig. The configurations in the secrets are preferred to those loaded from the config file.

The secret example:

apiVersion: v1
kind: Secret
metadata:
  name: registry-auth-example
  labels:
    registry-auth-config: "true"
  namespace: default
type: Opaque
data:
  config: |
    users:
      user3: password3
    auths:
      user3:
      - target: userrepo3/.*
        useRegexp: true
        actions:
        - pull
        - push

ComanndLine Argumentes

Argument	Default	Description
--server-bind-address		The listening IP, all IPs will listen if not defined.
--server-port	8080	The listening port.
--server-tls-cert-file		The file path for the HTTPS certificate. It's optional. HTTP will be used if empty.
--server-tls-key-file		The file path for the HTTPS private key, used with --server-tls-cert-file.
--auth-public-cert-file		The file path of the certificate for signing token, MUST be set.
--auth-private-key-file		The file path of the private key for signing token, MUST be set.
--auth-config-file		The file path of the config file. It's optional.
--auth-config-namespace		The namespace to load config from Kubernetes. It's optional.
--auth-config-selector	registry-auth-config=true	The label selector for secrets to load config. It's optional.
--auth-token-duration	600	The token's validation period in seconds.
--auth-issuer	registry-token-issuer	The token's issuer name.
--auth-thirdparty-server		The third-party authentication server. It's optional.
--registry-backend	127.0.0.1:5000	The backend registry address.
--kubeconfig		The config file to access Kubernetes. It's optional, used with --auth-config-namespace.
--log-level	info	The log level.

The Docker Registry's Config

The Docker Registry need configure to work with Registry-Auth. You can configure it by config file or environment variables.

You can add the following configs in /etc/docker/registry/config.yml:

auth:
  token:
    autoredirect: true                             # Set it true for proxy authentication, set it false for token authentication.
    realm: /auth/token                             # The Registry-Auth's URL. Set relative path for using proxy authentication, but full URL is needed for token authentication.
    service: docker-registry                       # It's used by the authentication server to distinguish different Docker Registry instances, but useless for now.
    issuer: registry-token-issuer                  # Same with Registry-Auth
    rootcertbundle: /etc/registry-auth/token.crt   # Same with Registry-Auth's --auth-public-cert-file argument.

Or you can exploit the following equivalent environment variables:

Key	Value
REGISTRY_AUTH_TOKEN_AUTOREDIRECT	true
REGISTRY_AUTH_TOKEN_REALM	/auth/token
REGISTRY_AUTH_TOKEN_SERVICE	token-service
REGISTRY_AUTH_TOKEN_ISSUER	registry-token-issuer
REGISTRY_AUTH_TOKEN_ROOTCERTBUNDLE	/etc/registry-auth/token.crt