No More Backdoors: Know Who Has Access to What, Right Now
Jun 13
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Using Teleport's Certificate Authority with GitHub

Teleport supports exporting user SSH certificates with configurable key extensions. This allows the Teleport CA to be used in conjunction with GitHub's support for SSH Certificate Authorities. This way, users can access their organizations' repositories with short-lived, signed SSH certificates.

Prerequisites

  • A running Teleport cluster version 15.3.7 or above. If you want to get started with Teleport, sign up for a free trial or set up a demo environment.

  • The tctl admin tool and tsh client tool.

    On Teleport Enterprise, you must use the Enterprise version of tctl, which you can download from your Teleport account workspace. Otherwise, visit Installation for instructions on downloading tctl and tsh for Teleport Community Edition.

  • Access to GitHub Enterprise and permissions to modify GitHub's SSH Certificate Authorities.
  • 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 15.3.7

    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.

Step 1/3. Import the Teleport CA into GitHub

In order to export the Teleport CA, execute the following command, assigning proxy to the address of your Teleport Proxy Service:

curl 'https://proxy/webapi/auth/export?type=user' | sed 's/^cert-authority //g'

Next, follow the instructions in the guide below to import your Teleport CA into GitHub:

Managing your organization's SSH certificate authorities

The contents of the exported teleport.ca file should by pasted into the "Key" field after clicking "New CA".

Step 2/3. Configure the GitHub key extension

Create or update a role to include the cert_extensions option. The value of name must be [email protected].

kind: role
version: v5
metadata:
  name: developer
spec:
  options:
     cert_extensions:
       - type: ssh
         mode: extension
         name: [email protected] # required to be `[email protected]`.
         value: "{{ external.logins }}"

Assign the developer role to your Teleport user by running the appropriate commands for your authentication provider:

  1. Retrieve your local user's roles as a comma-separated list:

    ROLES=$(tsh status -f json | jq -r '.active.roles | join(",")')
  2. Edit your local user to add the new role:

    tctl users update $(tsh status -f json | jq -r '.active.username') \ --set-roles "${ROLES?},developer"
  3. Sign out of the Teleport cluster and sign in again to assume the new role.

  1. Retrieve your github authentication connector:

    tctl get github/github --with-secrets > github.yaml

    Note that the --with-secrets flag adds the value of spec.signing_key_pair.private_key to the github.yaml file. Because this key contains a sensitive value, you should remove the github.yaml file immediately after updating the resource.

  2. Edit github.yaml, adding developer to the teams_to_roles section.

    The team you should map to this role depends on how you have designed your organization's role-based access controls (RBAC). However, the team must include your user account and should be the smallest team possible within your organization.

    Here is an example:

      teams_to_roles:
        - organization: octocats
          team: admins
          roles:
            - access
    +       - developer
    
  3. Apply your changes:

    tctl create -f github.yaml
  4. Sign out of the Teleport cluster and sign in again to assume the new role.

  1. Retrieve your saml configuration resource:

    tctl get --with-secrets saml/mysaml > saml.yaml

    Note that the --with-secrets flag adds the value of spec.signing_key_pair.private_key to the saml.yaml file. Because this key contains a sensitive value, you should remove the saml.yaml file immediately after updating the resource.

  2. Edit saml.yaml, adding developer to the attributes_to_roles section.

    The attribute you should map to this role depends on how you have designed your organization's role-based access controls (RBAC). However, the group must include your user account and should be the smallest group possible within your organization.

    Here is an example:

      attributes_to_roles:
        - name: "groups"
          value: "my-group"
          roles:
            - access
    +       - developer
    
  3. Apply your changes:

    tctl create -f saml.yaml
  4. Sign out of the Teleport cluster and sign in again to assume the new role.

  1. Retrieve your oidc configuration resource:

    tctl get oidc/myoidc --with-secrets > oidc.yaml

    Note that the --with-secrets flag adds the value of spec.signing_key_pair.private_key to the oidc.yaml file. Because this key contains a sensitive value, you should remove the oidc.yaml file immediately after updating the resource.

  2. Edit oidc.yaml, adding developer to the claims_to_roles section.

    The claim you should map to this role depends on how you have designed your organization's role-based access controls (RBAC). However, the group must include your user account and should be the smallest group possible within your organization.

    Here is an example:

      claims_to_roles:
        - name: "groups"
          value: "my-group"
          roles:
            - access
    +       - developer
    
  3. Apply your changes:

    tctl create -f oidc.yaml
  4. Sign out of the Teleport cluster and sign in again to assume the new role.

Step 3/3. Issue a user certificate

A user certificate may be issued with the following command, where <USERNAME> is the Teleport user to generate the SSH certificate for:

tctl auth sign --out out.cer --user=<USERNAME>

To test that authentication with this signed certificate is working correctly, SSH into github.com with your organization's user:

ssh -i out.cer org-<ID>@github.com

If authentication is successful, a "You've successfully authenticated" message should be displayed in the terminal.

This newly generated certificate may then be used when interacting with GitHub over SSH by adding the following to the ~/.ssh/config file:

Host github.com HostName github.com IdentityFile path/to/out.cer

When using SSH Certificate Authorities, you should retrieve your GitHub repository's SSH URL from the GitHub UI so the correct SSH user is used for authentication. For more information, see About SSH URLs with SSH certificates.