Teleport 16: Advancing Infrastructure Defense in Depth with Device Trust, MFA, and VNET
Jul 25
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Teleport

OAuth2 and OIDC authentication

This guide will explain how to configure an SSO provider using OpenID Connect (also known as OIDC) to issue Teleport credentials to specific groups of users. When used in combination with role-based access control (RBAC), OIDC allows Teleport administrators to define policies like:

  • Only members of the "DBA" group can connect to PostgreSQL databases.
  • Developers must never SSH into production servers.

Prerequisites

  • Admin access to the SSO/IdP being integrated with users assigned to groups/roles.
  • Teleport role with permission to maintain oidc resources. This permission is available in the default editor role.
  • A running Teleport cluster. If you want to get started with Teleport, sign up for a free trial.

  • The tctl admin tool and tsh client tool version >= 16.1.0.

    Visit Installation for instructions on downloading tctl and tsh.

  • To check that you can connect to your Teleport cluster, sign in with tsh login, then verify that you can run tctl commands using your current credentials. tctl is supported on macOS and Linux machines. For example:
    tsh login --proxy=teleport.example.com --user=[email protected]
    tctl status

    Cluster teleport.example.com

    Version 16.1.0

    CA pin sha256:abdc1245efgh5678abdc1245efgh5678abdc1245efgh5678abdc1245efgh5678

    If you can connect to the cluster and run the tctl status command, you can use your current credentials to run subsequent tctl commands from your workstation. If you host your own Teleport cluster, you can also run tctl commands on the computer that hosts the Teleport Auth Service for full permissions.

Identity Providers

Register Teleport with the external identity provider you will be using and obtain your client_id and client_secret. This information should be documented on the identity providers website. Here are a few links:

Google Workspace

Save the relevant information from your identity provider. To make following this guide easier, you can add the Client ID here and it will be included in the example commands below:

Client ID: <CLIENT-ID>

OIDC Redirect URL

OIDC relies on HTTP redirects to return control back to Teleport after authentication is complete. The redirect URL must be selected by a Teleport administrator in advance.

The redirect URL for OIDC authentication in Teleport is mytenant.teleport.sh/v1/webapi/oidc/callback. Replace mytenant.teleport.sh with your Teleport Cloud tenant or Proxy Service address.

OIDC connector configuration

The next step is to add an OIDC connector to Teleport. The connectors are created, tested, and added or removed using tctl resource commands or the Teleport Web UI.

On your workstation, create a file called client-secret.txt consisting only of your client secret.

To create a new connector, use tctl sso configure. The following example creates a connector resource file in YAML format named oidc-connector.yaml:

tctl sso configure oidc --name <CONNECTOR-NAME> \ --issuer-url <PATH-TO-PROVIDER> \ --id <CLIENT-ID> \ --secret $(cat client-secret.txt) \ --claims-to-roles <CLAIM-KEY>,<CLAIM-VALUE>,access \ --claims-to-roles <CLAIM-KEY>,<CLAIM-VALUE>,editor > oidc-connector.yaml
  • --name: Usually the name of the IdP, this is how the connector will be identified in Teleport.
  • --issuer-url: This is the base path to the IdP's OIDC configuration endpoint, excluding .well-known/openid-configuration. If, for example, the endpoint is https://example.com/.well-known/openid-configuration, you would use https://example.com.
  • --id: The client ID as defined in the IdP. Depending on your identity provider this may be something you can define (for example, teleport), or may be an assigned string.
  • --secret: The client token/secret provided by the IdP to authorize this client.
  • --claims-to-roles: A mapping of OIDC claims/values to be associated with Teleport roles.

For more information on these and all available flags, see the tctl sso configure oidc section of the Teleport CLI Reference page.

The file created should look like the example below. This connector requests the scope <CLAIM-KEY> from the identity provider, then maps the value to either the access or the editor role depending on the value returned for that key within the claims:

kind: oidc
metadata:
  name: oidc_connector
spec:
  claims_to_roles:
  - claim: groups
    roles:
    - access
    value: users
  - claim: groups
    roles:
    - editor
    value: admins
  client_id: <CLIENT-NAME>
  client_secret: <CLIENT-SECRET>
  issuer_url: https://idp.example.com/
  redirect_url: https://mytenant.teleport.sh:443/v1/webapi/oidc/callback
  max_age: 24h
version: v3

The following example was generated using Keycloak as the identity provider. Keycloak is being served at keycloak.example.com, and the Teleport Proxy Service is listening at teleport.example.com. In Keycloak, the client is named teleport. Under the teleport-dedicated client scope, we've added the "Group Membership" mapper:

kind: oidc
metadata:
  name: keycloak
spec:
  claims_to_roles:
  - claim: groups
    roles:
    - access
    value: /users
  - claim: groups
    roles:
    - editor
    value: /admins
  client_id: teleport
  client_secret: abc123...
  issuer_url: https://keycloak.example.com/realms/master
  redirect_url: https://teleport.example.com:443/v1/webapi/oidc/callback
version: v3

Before applying the connector to your cluster, you can test that it's configured correctly:

cat oidc-connector | tctl sso test

This should open up your web browser and attempt to log you in to the Teleport cluster through your IdP. If it fails, review the output of this command for troubleshooting details.

Tip

The "[OIDC] Claims" section of the CLI output provides all the details of your user provided by the IdP. This is a good starting point while troubleshooting errors like Failed to calculate user attributes.

After your tests are successful, create the connector:

tctl create -f oidc-connector.yaml

Optional: ACR Values

Teleport supports sending Authentication Context Class Reference (ACR) values when obtaining an authorization code from an OIDC provider. By default ACR values are not set. However, if the acr_values field is set, Teleport expects to receive the same value in the acr claim, otherwise it will consider the callback invalid.

In addition, Teleport supports OIDC provider specific ACR value processing which can be enabled by setting the provider field in OIDC configuration. At the moment, the only build-in support is for NetIQ.

A example of using ACR values and provider specific processing is below:

# example connector which uses ACR values
kind: oidc
version: v2
metadata:
  name: "oidc-connector"
spec:
  issuer_url: "https://oidc.example.com"
  client_id: "xxxxxxxxxxxxxxxxxxxxxxx.example.com"
  client_secret: "zzzzzzzzzzzzzzzzzzzzzzzz"
  redirect_url: "https://mytenant.teleport.sh/v1/webapi/oidc/callback"
  display: "Login with Example"
  acr_values: "foo/bar"
  provider: netiq
  scope: [ "group" ]
  claims_to_roles:
     - claim: "group"
       value: "editor"
       roles: [ "editor" ]
     - claim: "group"
       value: "user"
       roles: [ "access" ]

Optional: Max age

Teleport has supported setting the max_age field since version 13.3.7 to control the maximum age of users' sessions before they will be forced to reauthenticate. By default max_age is unset, meaning once a user authenticates using OIDC they will not have to reauthenticate unless the configured OIDC provider forces them to. This can be set to a duration of time to force users to reauthenticate more often. If max_age is set to zero seconds, users will be forced to reauthenticate with their OIDC provider every time they authenticate with Teleport.

Note that the specified duration must be in whole seconds. 24h works because that's the same as 1440s, but 60s500ms would not be allowed as that is 60.5 seconds.

# Extra parts of OIDC yaml have been removed.
spec:
  max_age: 24h

Note that not all OIDC providers support setting max_age. Google and GitLab are both known not to support it and authentication with those providers will not work when the max_age field is set.

Optional: Prompt

Set the Authorization Server prompt for the End-User for reauthentication and consent per the OIDC protocol. If no prompt value is set, Teleport uses select_account as default.

# Extra parts of OIDC yaml have been removed.
spec:
  # Valid values as defined from https://openid.net/specs/openid-connect-core-1_0.html#AuthRequest
  # none: The Authorization Server must not display any authentication or consent user interface pages.
  # select_account: The Authorization Server should prompt the End-User to select a user account.
  # login: The Authorization Server should prompt the End-User for reauthentication.
  # consent: The Authorization Server should prompt the End-User for consent before returning information to the Client.
  prompt: 'login'

Optional: Redirect URL and Timeout

The redirect URL must be accessible by all user, optional redirect timeout.

# Extra parts of OIDC yaml have been removed.
spec:
  redirect_url: https://<cluster-url>.example.com:3080/v1/webapi/oidc/callback
  # Optional Redirect Timeout.
  # redirect_timeout: 90s

Optional: Disable email verification

By default, Teleport validates the email_verified claim, and users who attempt to sign in without a verified email address are prevented from doing so:

ERROR: SSO flow failed.
identity provider callback failed with error: OIDC provider did not verify email.
        email not verified by OIDC provider

For testing and other purposes, you can opt out of this behavior by enabling allow_unverified_email in your OIDC connector. This option weakens the overall security of the system, so we do not recommend enabling it.

kind: oidc
version: v2
metadata:
  name: connector
spec:
  allow_unverified_email: true

Optional: Specify a claim to use as the username

By default, Teleport will use the user's email as their Teleport username.

You can define a username_claim to specify the claim that should be used as the username instead:

kind: oidc
version: v2
metadata:
  name: connector
spec:
  # Use the `preferred_username` claim as the user's Teleport username.
  username_claim: preferred_username

Enable default OIDC authentication

Configure Teleport to use OIDC authentication as the default instead of the local user database.

Follow the instructions for your Teleport edition:

Update /etc/teleport.yaml in the auth_service section and restart the teleport daemon.

auth_service:
  authentication:
    type: oidc

Create a file called cap.yaml:

kind: cluster_auth_preference
metadata:
  name: cluster-auth-preference
spec:    
  type: oidc
version: v2

Create a resource:

tctl create -f cap.yaml

Troubleshooting

Troubleshooting SSO configuration can be challenging. Usually a Teleport administrator must be able to:

  • Be able to see what SAML/OIDC claims and values are getting exported and passed by the SSO provider to Teleport.
  • Be able to see how Teleport maps the received claims to role mappings as defined in the connector.
  • For self-hosted Teleport Enterprise clusters, ensure that HTTP/TLS certificates are configured properly for both the Teleport Proxy Service and the SSO provider.

If something is not working, we recommend to:

  • Double-check the host names, tokens and TCP ports in a connector definition.

Using the Web UI

If you get "access denied" or other login errors, the number one place to check is the Audit Log. Under the Management area you can access it within the Activity tab in the Teleport Web UI.

Example of a user being denied because the role clusteradmin wasn't set up:

{
  "code": "T1001W",
  "error": "role clusteradmin is not found",
  "event": "user.login",
  "method": "oidc",
  "success": false,
  "time": "2019-06-15T19:38:07Z",
  "uid": "cd9e45d0-b68c-43c3-87cf-73c4e0ec37e9"
}

Teleport does not show the expected Nodes

When Teleport's Auth Service receives a request to list Teleport Nodes (e.g., to display Nodes in the Web UI or via tsh ls), it only returns the Nodes that the current user is authorized to view.

For each Node in the user's Teleport cluster, the Auth Service applies the following checks in order and, if one check fails, hides the Node from the user:

  • None of the user's roles contain a deny rule that matches the Node's labels.
  • At least one of the user's roles contains an allow rule that matches the Node's labels.

If you are not seeing Nodes when expected, make sure that your user's roles include the appropriate allow and deny rules as documented in the Teleport Access Controls Reference.

When configuring SSO, ensure that the identity provider is populating each user's traits correctly. For a user to see a Node in Teleport, the result of populating a template variable in a role's allow.logins must match at least one of a user's traits.logins.

In this example a user will have usernames ubuntu, debian and usernames from the SSO trait logins for Nodes that have a env: dev label. If the SSO trait username is bob then the usernames would include ubuntu, debian, and bob.

kind: role
metadata:
  name: example-role
spec:
  allow:
    logins: ['{{external.logins}}', ubuntu, debian]
    node_labels:
      'env': 'dev'
version: v5

Single sign-on fails with OIDC

When encountering the error message "Failed to verify JWT: oidc: unable to verify JWT signature: no matching keys", it typically indicates a discrepancy between the algorithm used to sign the JWT token and the algorithm(s) supported by the JSON Web Key Set (JWKS). Specifically, the token might be signed with one algorithm, e.g., HS256, while the JWKS only lists keys for a different algorithm. e.g., RS256. This issue predominantly arises when using identity providers that offer extremely low-level functionality.

Here are some things to check:

  • Verify the JWT header specifies the correct signing algorithm. This should match one of the algorithms listed in the keys section of the JWKS endpoint response.
  • Ensure the JWKS endpoint is returning all relevant public keys. Sometimes key rotation can cause valid keys to be omitted.

To resolve the issue, align the JWT algorithm header with a supported algorithm in the JWKS. Rotate keys if necessary. Verify the JWKS only publishes the active public keys. With proper configuration, the signature should validate successfully.