SSH Authentication with ADFS

This guide will cover how to configure Active Directory Federation Services ADFS 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.
  • ... and many others.

Version Warning

This guide requires a commercial edition of Teleport. The open source edition of Teleport only supports Github as an SSO provider.

Enable ADFS Authentication

First, configure Teleport auth server to use ADFS authentication instead of the local user database. Update /etc/teleport.yaml as shown below and restart the teleport daemon.

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 AD FS 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).

Name ID Configuration Group Configuration

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.

WAN Configuration UPN Configuration

You'll also need to create a Relying Party Trust, use the below information to help guide you through the Wizard. Note, 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

Lets create two Teleport roles: one for administrators and the other is for normal users. You can create them using 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 username claim
    logins: [ "{{external.username}}", ubuntu ]

Next create a SAML connector resource:

kind: saml
version: v2
metadata:
  name: "adfs"
spec:
  provider: "adfs"
  acs: "https://localhost:3080/v1/webapi/saml/acs"
  entity_descriptor_url: "https://adfs.example.com/FederationMetadata/2007-06/FederationMetadata.xml"
  attributes_to_roles:
    - name: "http://schemas.xmlsoap.org/claims/Group"
      value: "teleadmins"
      roles: ["admins"]
    - name: "http://schemas.xmlsoap.org/claims/Group"
      value: "teleusers"
      roles: ["users"]

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 creataed. In our situation, we are mapping the "Group" attribute whose full name is http://schemas.xmlsoap.org/claims/Group with a value of "teleadmins" to the "admin" role. Groups with the value "teleusers" 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 OneLogin". The CLI is the same as before:

$ tsh --proxy=proxy.example.com login

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

Tip

Teleport can use multiple SAML connectors. In this case a connector name can be passed via tsh login --auth=connector_name

IMPORTANT

Teleport only supports sending party initiated flows for SAML 2.0. This means you can not initiate login from your identity provider, you have to initiate login from either the Teleport Web UI or CLI.

Troubleshooting

If you get "access denied errors" the number one place to check is the audit log on the Teleport auth server. It is located in /var/lib/teleport/log by default and it will contain the detailed reason why a user's login was denied.

Some errors (like filesystem permissions or misconfigured network) can be diagnosed using Teleport's stderr log, which is usually available via:

$ sudo journalctl -fu teleport

If you wish to increase the verbocity of Teleport's syslog, you can pass --debug flag to teleport start command.