Single Sign-On with Active Directory Federation Services

This guide will explain how to configure Active Directory Federation Services (ADFS) to be a single sign-on (SSO) provider to issue SSH credentials to specific groups of users. When used in combination with role based access control (RBAC), it allows SSH administrators to define policies like:

• Only members of "DBA" group can SSH into machines running PostgreSQL.
• Developers must never SSH into production servers.

Prerequisites

• ADFS installation with Admin access and users assigned to at least two groups.
• Teleport role with access to maintaining saml resources. This is available in the default editor role.

tsh login --proxy=teleport.example.com [email protected]
tctl status
Cluster  teleport.example.com
Version  12.1.1
CA pin   sha256:abdc1245efgh5678abdc1245efgh5678abdc1245efgh5678abdc1245efgh5678

tsh login --proxy=myinstance.teleport.sh [email protected]
tctl status
Cluster  myinstance.teleport.sh
Version  12.1.1
CA pin   sha256:sha-hash-here

Enable default SAML authentication

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

You can either edit your Teleport configuration file or create a dynamic resource.

auth_service:
  authentication:
    type: saml

Configure ADFS

You'll need to configure ADFS to export claims about a user (Claims Provider Trust in ADFS terminology) and you'll need to configure ADFS to trust Teleport (a Relying Party Trust in ADFS terminology).

For Claims Provider Trust configuration, you'll need to specify at least the following two incoming claims: Name ID and Group. Name ID should be a mapping of the LDAP Attribute E-Mail-Addresses to Name ID. A group membership claim should be used to map users to roles (for example to separate normal users and admins).

In addition, if you are using dynamic roles (see below), it may be useful to map the LDAP Attribute SAM-Account-Name to Windows account name and create another mapping of E-Mail-Addresses to UPN.

You'll also need to create a Relying Party Trust. Use the below information to help guide you through the Wizard. Note that for development purposes we recommend using https://localhost:3080/v1/webapi/saml/acs as the Assertion Consumer Service (ACS) URL, but for production you'll want to change this to a domain that can be accessed by other users as well.

• Create a claims aware trust.
• Enter data about the relying party manually.
• Set the display name to something along the lines of Teleport.
• Skip the token encryption certificate.
• Select "Enable support for SAML 2.0 Web SSO protocol" and set the URL to https://localhost:3080/v1/webapi/saml/acs.
• Set the relying party trust identifier to https://localhost:3080/v1/webapi/saml/acs as well.
• For access control policy select "Permit everyone".

Once the Relying Party Trust has been created, update the Claim Issuance Policy for it. Like before, make sure you send at least Name ID and Group claims to the relying party (Teleport). If you are using dynamic roles, it may be useful to map the LDAP Attribute SAM-Account-Name to "Windows account name" and create another mapping of E-Mail-Addresses to "UPN".

Lastly, ensure the user you create in Active Directory has an email address associated with it. To check this open Server Manager then "Tools -> Active Directory Users and Computers" and select the user and right click and open properties. Make sure the email address field is filled out.

Create Teleport roles

Let's create two Teleport roles: one for administrators and the other for normal users. You can create them using the tctl create {file name} CLI command or via the Web UI.

# admin-role.yaml
kind: "role"
version: "v3"
metadata:
  name: "admin"
spec:
  options:
    max_session_ttl: "8h0m0s"
  allow:
    logins: [ root ]
    node_labels:
      "*": "*"
    rules:
      - resources: ["*"]
        verbs: ["*"]

# user-role.yaml
kind: "role"
version: "v3"
metadata:
  name: "dev"
spec:
  options:
    # regular users can only be guests and their certificates will have a TTL of 1 hour:
    max_session_ttl: "1h"
  allow:
    # only allow login as either ubuntu or the 'windowsaccountname' claim
    logins: [ '{{external["http://schemas.microsoft.com/ws/2008/06/identity/claims/windowsaccountname"]}}', ubuntu ]
    node_labels:
      "access": "relaxed"

This role declares:

• Devs are only allowed to log in to nodes labeled access: relaxed.
• Developers can log in as the ubuntu user.
• Developers will not be able to see or replay past sessions or re-configure the Teleport cluster.

The login {{external["http://schemas.microsoft.com/ws/2008/06/identity/claims/windowsaccountname"]}} configures Teleport to look at the http://schemas.microsoft.com/ws/2008/06/identity/claims/windowsaccountname ADFS claim and use that field as an allowed login for each user. Note the double quotes (") and square brackets ([]) around the claim name—these are important.

Next, create a SAML connector resource:

# This example connector uses SAML to authenticate against
# Active Directory Federation Services (ADFS)
kind: saml
version: v2
metadata:
  name: adfs_connector
spec:
  # display allows to set the caption of the "login" button
  # in the Web interface
  # Using the work 'Microsoft' will show the windows symbol in the UI.
  display: Microsoft

  # "adfs" provider setting tells Teleport that this SAML connector uses ADFS
  # as a provider
  provider: adfs

  # Controls whether IdP-initiated SSO is allowed. If false, all such requests will be rejected with an error.
  allow_idp_initiated: false

  # entity_descriptor XML can either be copied into connector or fetched from a URL
  entity_descriptor: |
    <EntityDescriptor xmlns:md="urn:oasis:names:tc:SAML:2.0:metadata">
    ...
    </md:EntityDescriptor>
  # entity_descriptor_url is commented out, as only one is required to setup adfs.
  # if you're running Teleport in FIPS mode entity_descriptor_url with Azure AD may
  # fail
  #entity_descriptor_url: "https://example.com"

  # issuer typically comes from the "entity_descriptor" but can be overridden here
  issuer: "foo"
  # sso typically comes from the "entity_descriptor" but can be overridden here
  sso: "bar"
  # cert typically comes from the "entity_descriptor" but can be overridden here
  cert: |
    -----BEGIN RSA PRIVATE KEY-----
    ...
    -----END RSA PRIVATE KEY-----

  acs: "https://<cluster-url>.example.com:3080/v1/webapi/saml/acs"
  # if "service_provider_issuer" is not set, comes from "acs"
  service_provider_issuer: "https://<cluster-url>.example.com:3080/v1/webapi/saml/acs"
  # if "audience" is not set, comes from "acs"
  audience: "https://<cluster-url>.example.com:3080/v1/webapi/saml/acs"

  # if "signing_key_pair" is not set, teleport will generate a self signed
  # signing key pair
  signing_key_pair:
    private_key: |
      -----BEGIN RSA PRIVATE KEY-----
      ...
      -----END RSA PRIVATE KEY-----
    cert:
      -----BEGIN RSA PRIVATE KEY-----
      ...
      -----END RSA PRIVATE KEY-----

  attributes_to_roles:
    - name: "http://schemas.xmlsoap.org/claims/Group"
      value: "Administrators"
      roles: ["editor"]
    - name: "http://schemas.xmlsoap.org/claims/Group"
      value: "Users"
      roles: ["access"]

The acs field should match the value you set in ADFS earlier and you can obtain the entity_descriptor_url from ADFS under "ADFS -> Service -> Endpoints -> Metadata".

The attributes_to_roles is used to map attributes to the Teleport roles you just created. In our situation, we are mapping the "Group" attribute whose full name is http://schemas.xmlsoap.org/claims/Group with a value of "admins" to the "admin" role. Groups with the value "users" is being mapped to the "users" role.

Export the signing key

For the last step, you'll need to export the signing key:

tctl saml export adfs

Save the output to a file named saml.crt, return back to ADFS, open the "Relying Party Trust" and add this file as one of the signature verification certificates.

Testing

The Web UI will now contain a new button: "Login with MS Active Directory". The CLI is the same as before:

tsh --proxy=proxy.example.com login

This command will print the SSO login URL and try to open it automatically in a browser.

Troubleshooting

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

• Ensure that HTTP/TLS certificates are configured properly for both Teleport proxy and the SSO provider.

• 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.

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. You can access it in the Activity tab of 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