Authenticate users with single sign-on (SSO) and Auth0

Consul Enterprise 1.8.0 introduced the ability to configure single sign-on (SSO) and to authenticate with Consul using OIDC.

OIDC authentication is useful when you want to deploy SSO widely in your organization and do not want to manage access with Consul ACL tokens.

Once implemented, SSO will enable an interactive login procedure that can be initiated from either the Consul UI or the command line.

In this tutorial you will configure Auth0 as an identity provider. Your configuration will use the user metadata in Auth0 to automatically grant permissions in Consul ACL.

This is a multi-step process that includes:

• configure an application in Auth0 for Consul integration;
• set up Consul ACL policies and roles to provide permissions to users
• configure user metadata and use binding rules to automatically assign permissions to users based on their metadata values.

This approach unifies the user permissions grant without the need to create individual user tokens or to define permissions individually for the different users. The tutorial also shows one example of how to define service permissions grants for a user based on unique metadata values of the individual user, making this approach also suitable for finer grained permissions.

Prerequisites

In order to complete this tutorial the following prerequisites need to be satisfied:

• A Consul Enterprise datacenter or local dev agent. The datacenter will need ACLs enabled to use the OIDC authentication method. You can use the following ACL configuration as a minimal example to follow the steps in this tutorial:

acl {
 enabled        = true
 default_policy = "deny"

 tokens {
   initial_management = "root"
   agent  = "root"
 }
}

{
  "acl": {
    "enabled": true,
    "default_policy": "deny",
    "tokens": {
      "initial_management": "root",
      "agent": "root"
    }
  }
}

• A valid Auth0 account. If you do not have one, create one now, before continuing with the tutorial. The tutorial will show you the configuration steps necessary to configure your Auth0 account to interact with Consul.

Configure Auth0 application

In the Auth0 dashboard, select Applications.

Once you have created a new account, Auth0 should already have a default application called Default App in the main Dashboard.

In this tutorial we will be using the default application.

Select Default App and open the Settings tab.

In the Application configuration, you can set the callback URLs that the user will be redirected to after the authentication process is completed.

In the Allowed Callback URLs field, enter the following:

http://<consul_agent_address>:8550/oidc/callback,
http://<consul_agent_address>:8500/ui/oidc/callback

The http://<consul_agent_address>:8550/oidc/callback address will be used by the CLI when you login via consul login -type=oidc -method=oidc command.

The http://<consul_agent_address>:8500/ui/oidc/callback address will be used by the Consul UI when you login with OIDC auth method.

For example, if you are running your Consul agent locally you would use:

http://localhost:8550/oidc/callback,
http://localhost:8500/ui/oidc/callback

Create Auth0 users and metadata

In the Auth0 dashboard for your app, on the sidebar, select Users & Roles > Users and click on Create User

Create at least one demo user with username/password authentication.

Edit the user's record and assign some user_metadata and app_metadata such as:

{
  // user_metadata (end-user editable)
  "first_name": "Kara",
  "last_name": "Danvers"
}

{
  // app_metadata (end-user not editable)
  "roles": ["engineering"]
}

Configure claims in the ID tokens using Auth0 rules

In the Auth0 dashboard for your application, on the sidebar, select Rules.

Create a new rule with the following content:

function (user, context, callback) {
   user.user_metadata = user.user_metadata || {};
   user.app_metadata = user.app_metadata || {};

   context.idToken['http://consul.internal/first_name'] = user.user_metadata.first_name || "";
   context.idToken['http://consul.internal/last_name'] = user.user_metadata.last_name || "";
   context.idToken['http://consul.internal/groups'] = user.app_metadata.roles || [];
   callback(null, user, context);
}

Create Consul policies and roles

After the login procedure confirms the user identity, it has to then give them privileges when creating their ACL token. Auth methods in Consul use binding rules to control that.

Binding rules allow for two ways to assign privileges to a new token:

• Service identities: this approach is better suited for application login and is not suggested for user login.
• Roles: this approach is preferred when enabling user login.

Roles are a named collection of privileges, such as lists of policies and service identities, that can be linked to a token.

In order to assign some privilege to a token via an auth method, you will first define the privilege in a policy and then assign that policy to a role. In this way, the binding rule can reference the role by name.

Step 1: Define policy for Auth0 users

Create a policy named eng-ro to allow full read-only access of any service for service discovery.

$ CONSUL_HTTP_TOKEN=root \
   consul acl policy create -name eng-ro \
   -rules='service_prefix "" { policy="read" } node_prefix "" { policy="read" }'

If the command completes successfully, you will receive an output similar to this:

ID:           56c478f2-21a3-dc84-9116-4827e32125ff
Name:         eng-ro
Namespace:    default
Description:
Datacenters:
Rules:
service_prefix "" { policy="read" } node_prefix "" { policy="read" }

Assign a policy to a role

Next create a role named eng-ro linked to the policy created earlier.

$ CONSUL_HTTP_TOKEN=root \
   consul acl role create -name eng-ro -policy-name eng-ro

If the command completes successfully, you will receive an output similar to this:

Name:         eng-ro
Namespace:    default
Description:
Policies:
  56c478f2-21a3-dc84-9116-4827e32125ff - eng-ro

Enable the OIDC auth method for Consul

In the Auth0 dashboard, select Applications.

Select Default App, and open the Settings tab.

You will use the values from Domain, Client ID, and Client Secret to create a configuration file for the OIDC auth method for Consul.

{
  "OIDCDiscoveryURL": "https://<AUTH0_DOMAIN>/",
  "OIDCClientID": "<AUTH0_CLIENT_ID>",
  "OIDCClientSecret": "<AUTH0_CLIENT_SECRET>",
  "BoundAudiences": ["<AUTH0_CLIENT_ID>"],
  "AllowedRedirectURIs": [
    "http://localhost:8550/oidc/callback",
    "http://localhost:8500/ui/oidc/callback"
  ],
  "ClaimMappings": {
    "http://consul.internal/first_name": "first_name",
    "http://consul.internal/last_name": "last_name"
  },
  "ListClaimMappings": {
    "http://consul.internal/groups": "groups"
  }
}

$ CONSUL_HTTP_TOKEN=root \
  consul acl auth-method create -type oidc \
    -name auth0 \
    -max-token-ttl=5m \
    -config=@auth-method-config.json

{
  "Name": "auth0",
  "Type": "oidc",
  "MaxTokenTTL": "5m",
  "Config": {
    "OIDCDiscoveryURL": "https://<AUTH0_DOMAIN>/",
    "OIDCClientID": "<AUTH0_CLIENT_ID>",
    "OIDCClientSecret": "<AUTH0_CLIENT_SECRET>",
    "BoundAudiences": ["<AUTH0_CLIENT_ID>"],
    "AllowedRedirectURIs": [
      "http://localhost:8550/oidc/callback",
      "http://localhost:8500/ui/oidc/callback"
    ],
    "ClaimMappings": {
      "http://consul.internal/first_name": "first_name",
      "http://consul.internal/last_name": "last_name"
    },
    "ListClaimMappings": {
      "http://consul.internal/groups": "groups"
    }
  }
}

$ curl -sL --header 'x-consul-token: root' --request PUT \
   http://localhost:8500/v1/acl/auth-method \
   --data @auth-method-config.json

Once you have configured the auth method, you can automate permissions grants to users using the metadata you defined earlier. This means that once auth method trust is established, Consul can be configured to bind attested identities to roles or services with no additional work beyond what is required to link the identity and the auth method. This can be configured using Consul binding rules.

Grant role permissions with app metadata

Grant users in the engineering group the role eng-ro.

$ CONSUL_HTTP_TOKEN=root \
   consul acl binding-rule create \
       -method=auth0 \
       -bind-type=role \
       -bind-name=eng-ro \
       -selector='engineering in list.groups'

ID:           7c9d6445-75c0-7d93-bb5e-d56100590950
Namespace:    default
AuthMethod:   auth0
Description:
BindType:     role
BindName:     eng-ro
Selector:     engineering in list.groups

This will automatically associate every user with engineering in their app_metadata to Consul eng-ro role that you already associated with an ACL policy.

Grant service permissions with user metadata

If you want to grant users permissions to register services, you can use a service type binding. In this tutorial, you will grant users in the engineering group the ability to register a service in the service mesh with their own name.

$ CONSUL_HTTP_TOKEN=root \
   consul acl binding-rule create \
       -method=auth0 \
       -bind-type=service \
       -bind-name='dev-${value.first_name}-${value.last_name}' \
       -selector='engineering in list.groups'

ID:           a5309527-f5e0-8034-0795-ed7a98b961d0
Namespace:    default
AuthMethod:   auth0
Description:
BindType:     service
BindName:     dev-${value.first_name}-${value.last_name}
Selector:     engineering in list.groups

Login with OIDC

After the configuration is complete, you can login to Consul using Auth0.

$ consul login -method=auth0 -type=oidc -token-sink-file=dev.token

f110aff6-4d5b-4563-80dd-4da6f74c1067

$ consul acl token read -self -token-file=dev.token
AccessorID:       cd887b52-263a-4ae2-8747-725b76d0a79f
SecretID:         f110aff6-4d5b-4563-80dd-4da6f74c1067
Namespace:        default
Description:      token created via OIDC login
Local:            true
Auth Method:      auth0
Create Time:      2020-04-28 15:00:49.790370772 -0500 CDT
Roles:
   7d3e3a66-8c0f-e528-944e-84df6b36a115 - eng-ro
Service Identities:
   dev-kara-danvers (Datacenters: all)

Once login is successful, you can navigate to the Consul UI.

Next steps

In this tutorial you learned how to enable SSO for Consul Enterprise, and how to use Auth0 as the OIDC provider.

You configured Auth0 and created a user to test the SSO feature.

Finally, you tested the SSO login using both the CLI and the UI.

Complete Secure Consul with Access Control Lists (ACLs) to learn how to configure production ready ACLs for your Consul datacenter.