Active Directory Auth Method with TOTP Login MFA

Vault first introduced Login MFA in version 1.10.0 to offer support for multiple authentication factors with Vault auth methods.

Challenge

Your organization uses the Vault Active Directory Auth Method to allow users to authenticate with Vault using their Active Directory credentials. You need to enforce additional authentication method, such as a Time-Based One Time Password (TOTP).

Solution

The Vault Login MFA functionality provides a means to link an auth method to additional authentication factors such as those offered by third party services. It also features a built in TOTP MFA method.

You can leverage the built-in TOTP MFA method with an authenticator application to enhance security with an additional authentication factor.

Target audience

Vault cluster administrators with privileged policies to manage auth methods and secrets engines. The admin persona performs the steps of this role in the hands-on scenario that is part of this tutorial.

Vault users authenticating to Vault with the Active Directory secrets engine. The user persona will authenticate with the Active Directory secrets engine and the authenticator application to authenticate with Vault.

Scenario introduction

To learn how Vault TOTP MFA works, you can use the hands on lab steps to spin up a virtual machine with a Windows Server with Active Directory. You will also run a Docker container running Vault in dev mode.

The diagram shows the Two-Phase MFA authentication workflow described in this tutorial.

1. The admin persona configures the Vault environment.

2. The user persona uses the Vault API, CLI, or UI and their authentication application on an enrolled device.

3. The user persona attempts authentication with Vault.

4. Vault returns a message advising that the authentication requires MFA.

5. The user persona interacts with their authenticator app, which returns a code used as the extra authentication factor.

6. The user persona validates their authentication with the code returned from authenticator app.

7. Vault verifies the code through the TOTP MFA method

8. If verification is successful, the authentication also succeeds and the user persona receives a Vault token.

Prerequisites

This lab functions end to end on macOS using an x86_64 based processor. If you are running macOS on an Apple silicon-based processor, use a x86_64 based Linux virtual machine in your preferred cloud provider.

• A Windows environment with Active Directory. This scenario uses the community based Vagrant environment for a Windows Server based Active Directory project.

• Docker. This scenario uses Docker Desktop for macOS.

• Vagrant. Required if you choose to use the Vagrant environment for an Active Directory Server. This scenario was last tested with version 2.2.19.

  • A supported Vagrant virtualization target; this scenario uses VirtualBox tested against version 6.1.34.

• git required for cloning repositories used in the scenario.

• An authenticator application; this scenario uses the Google Authenticator app for iOS, but you can use any compatible authenticator application.

• If you are following along on a Linux based host, you'll need xdg-open. Sometimes this utility is part of an xdg-utils meta-package that you can install with your OS package manager. Check your distribution specific documentation for details on how to install xdg-open.

Lab setup

You will use a terminal session and command line to start an Active Directory virtual machine and Vault server container.

Open a new terminal session to begin the lab setup.

For ease of cleanup and simplicity, create a temporary directory to contain all required configuration for the scenario, and assign the directory name value to the environment variable HC_LEARN_LAB.

$ export HC_LEARN_LAB="$(mktemp -d -t hc-learn-XXXX)"

Change into this directory; you will execute all scenario commands on the local host from this directory or one of its descendants.

$ cd $HC_LEARN_LAB

You can also echo this value so that you can find the files within the directory for using the generated QR code later.

$ echo $HC_LEARN_LAB

Windows Server with Active Directory

To set up your Windows Server environment with Active Directory environment, clone the project repository.

$ git clone https://github.com/splitbrain/vagrant-active-directory

Change into the project directory.

$ cd vagrant-active-directory

Create a directory for the extra VirtualBox network configuration.

$ sudo mkdir /etc/vbox

Write the configuration file.

$ sudo sh -c 'tee /etc/vbox/networks.conf << EOF
* 10.0.0.0/8 192.168.0.0/16
* 2001::/64
EOF'

Start the virtual machine with Vagrant.

$ vagrant up

The last lines in the Vagrant log output show that the Active Directory server is ready because it begins creating the users and groups:

    dc: Waiting for the AD to become available... (Can take a long time)
    dc: Creating Groups...
    dc: Creating Users...

Confirm that the Active Directory services are available by connecting to the virtual machine with WinRM and using dcdiag to test services.

$ vagrant winrm -c 'dcdiag /test:Services' dc | grep passed
         ......................... DC passed test Connectivity
         ......................... DC passed test Services

If the tests also show passing status, then the Active Directory server is ready.

Docker network

Create a Docker network named learn-vault-network.

$ docker network create learn-vault-network

Vault server

Start a dev mode Vault server container.

$ docker run \
    --name learn-vault \
    --detach \
    --rm \
    --network learn-vault-network \
    --cap-add=IPC_LOCK \
    --publish 8200:8200 \
    --hostname vault-server \
    --volume /tmp:/tmp \
    --env VAULT_ADDR=http://0.0.0.0:8200 \
    hashicorp/vault server \
     -dev \
     -dev-root-token-id=root \
     -dev-listen-address 0.0.0.0:8200

Access the learn-vault container by executing a shell within it.

$  docker exec -it learn-vault sh

Notice that the prompt changes to:

/ #

Update the package cache.

$ apk update

Install jq to parse JSON output.

$ apk add jq

Get Vault server status.

$ vault status
Key             Value
---             -----
Seal Type       shamir
Initialized     true
Sealed          false
Total Shares    1
Threshold       1
Version         1.10.2
Storage Type    inmem
Cluster Name    vault-cluster-313799f2
Cluster ID      01478d6e-5d5c-af5d-7e51-6694c706f130
HA Enabled      false

The Vault server is ready.

For the purposes of this scenario, you will use the initial root token value with the VAULT_TOKEN environment variable for the scenario steps.

Scenario tasks

Enable and configure LDAP auth method

Enable the LDAP auth method.

$ VAULT_TOKEN=root vault auth enable ldap
Success! Enabled ldap auth method at: ldap/

Configure the LDAP auth method.

$ VAULT_TOKEN=root vault write auth/ldap/config \
    url="ldaps://host.docker.internal:7636" \
    userattr=sAMAccountName \
    userdn="CN=Users,DC=example,DC=local" \
    groupdn="CN=Users,DC=example,DC=local" \
    groupfilter="(&(objectClass=person)(uid={{.Username}}))" \
    groupattr="memberOf" \
    binddn="CN=vagrant,CN=Users,DC=example,DC=local" \
    bindpass='vagrant' \
    insecure_tls=true

Successful output example:

Success! Data written to: auth/ldap/config

Since the Active Directory server for this scenario uses a self-signed TLS certificate, you instruct Vault to use insecure TLS with insecure_tls=true. You should not use this setting in a production configuration. You should instead prefer using certificates which a known CA validates.

Login with LDAP auth method

Test the Vault login with LDAP auth method.

$ vault login -method=ldap username=w.kluge password='Foo_b_ar123!'

Successful output example:

Success! You are now authenticated. The token information displayed below
is already stored in the token helper. You do NOT need to run "vault login"
again. Future Vault requests will automatically use this token.

WARNING! The following warnings were returned from Vault:

  * no LDAP groups found in groupDN 'CN=Users,DC=example,DC=local'; only
  policies from locally-defined groups available

Key                    Value
---                    -----
token                  hvs.CAESIEipBa8DtnBePdnrElWEc0WOh2ONelkG-i0wDLAeuHYiGh4KHGh2cy5LMFB6NFJzR0RxcTdncnh6ejdDdXNhTk4
token_accessor         s7FUF7n3f8BbWzzWRAW0zvXV
token_duration         768h
token_renewable        true
token_policies         ["default"]
identity_policies      []
policies               ["default"]
token_meta_username    w.kluge

You need to capture the identity entity ID of the w.kluge user for configuration of the Login MFA method.

Export its value to the ENTITY_ID environment variable for later use.

$ export ENTITY_ID=$(vault login -method=ldap username=w.kluge \
    password='Foo_b_ar123!' -format=json \
    | jq -r '.auth.entity_id')

Check the value.

$ echo $ENTITY_ID
fcf3f7bc-5042-11dd-53f5-917aaede9300

Enable login MFA method

Enable a Login MFA method to enforce TOTP on the LDAP auth method.

Configure the Login MFA TOTP method and assign its method ID to the TOTP_METHOD_ID environment variable.

$ TOTP_METHOD_ID=$(VAULT_TOKEN=root vault write identity/mfa/method/totp \
    -format=json \
    generate=true \
    issuer=Vault \
    period=30 \
    key_size=30 \
    algorithm=SHA256 \
    digits=6 | jq -r '.data.method_id')

Check the value.

$ echo $TOTP_METHOD_ID
29a3e898-50e6-5763-7fbe-834df79eea77

Generate authenticator app QR code

Generate QR code as a PNG image.

$ VAULT_TOKEN=root vault write -field=barcode \
    /identity/mfa/method/totp/admin-generate \
    method_id=$TOTP_METHOD_ID entity_id=$ENTITY_ID \
    | base64 -d > /tmp/qr-code.png

You can open the QR code image from the host system in different ways depending on your operating system.

You can use an example for Linux, macOS, or Windows.

$ xdg-open /tmp/qr-code.png

$ open /tmp/qr-code.png

$ start /tmp/qr-code.png

You can scan this image with your authenticator app to add Vault TOTP. Again, this scenario presumes that you will use the Google Authenticator app for this.

Create login MFA enforcement

Capture the LDAP auth method for use in creating a Login MFA enforcement.

$ LDAP_ACCESSOR=$(VAULT_TOKEN=root vault auth list -format=json \
    --detailed | jq -r '."ldap/".accessor')

Check the value.

$ echo $LDAP_ACCESSOR
auth_ldap_cf1840a4

Create the enforcement.

$ VAULT_TOKEN=root vault write /identity/mfa/login-enforcement/adtotp \
    mfa_method_ids="$TOTP_METHOD_ID" \
    auth_method_accessors=$LDAP_ACCESSOR

Successful output example:

Success! Data written to: identity/mfa/login-enforcement/adtotp

Login with LDAP auth method

Use the CLI to login with the LDAP auth method a second time.

$ vault login -method=ldap username=w.kluge password='Foo_b_ar123!'
Enter the passphrase for methodID "01194a79-e2d9-c038-029d-79b0091cafd0" of type "totp":

Enter the TOTP from your authenticator app when prompted.

Successful output example:

Key                    Value
---                    -----
token                  hvs.CAESIE6K0E7BjHv2m1Gj2IAriFhBfUsB6xjtechsRIhL6-wbGh4KHGh2cy5VNDFTZE9XMm96UUN0UDZ1WWtKQm94SkI
token_accessor         SXxDMVRc35h9OBIdbTAf52RO
token_duration         768h
token_renewable        true
token_policies         ["default"]
identity_policies      []
policies               ["default"]
token_meta_username    w.kluge

You have authenticated to Vault with the Active Directory. Enter exit to quit out of the container.

Login TOTP is also supported when authenticating with the Vault user interface.

Navigate to http://127.0.0.1:8200

From the Method pulldown menu select LDAP.

Enter w.kluge in the Username textbox and Foo_b_ar123! in the Password textbox then click Sign In.

Cleanup

Stop the Vault server Docker container.

$ docker stop learn-vault

Remove the Docker network

$ docker network rm learn-vault-network

Change into the vagrant-active-directory project directory.

$ cd $HC_LEARN_LAB/vagrant-active-directory

Destroy the virtual machine

$ vagrant destroy -f

Change to your home directory.

$ cd

To remove all configuration and other data you created during this scenario, you can recursively remove the $HC_LEARN_LAB directory.

$ rm -rf $HC_LEARN_LAB

Remove the additional VirtualBox network configuration.

$ sudo rm -rf /etc/vbox

Summary

As the admin persona, you learned how to enable and configure Login MFA with the LDAP auth method and TOTP MFA method.

As the user persona, you learned how to use a Login MFA method when authenticating to Vault.

You can learn more about Vault authentication and auth methods in the Manage Authentication Methods tutorial, and the Auth Methods documentation.

Help and reference

• Login MFA documentation

• Enable Login Multi Factor Authentication (MFA)