Enforce Okta Device Trust for Jamf Pro-managed macOS devices

Prerequisites

This solution works with:
- Apple computers running Okta-supported versions of macOS.
- Jamf Pro MDM solution
- The following browsers and native apps capable of accessing the Okta Keychain on the managed computer when performing the federated authentication flow to Okta:
  - Browsers: Chrome and Safari browsers
  - Modern Auth-enabled native apps:
    - Box
    - Google Drive
    - Microsoft Office
    - Skype for Business
    - Slack
- The Okta Device Registration Task is a Python script that completes various tasks (for example, enrollment, and registration). Depending on your OS, complete one of the following, to make sure you use the appropriate version of this script:
  - If you have macOS 10.15.xx (Catalina) or 11.xx (Big Sur), use registration version 1.3.1 or later, which is based on Python 3.
  - If you have macOS 10.14.xx (Mojave) and are currently using registration script 1.2.1 or earlier, continue to use it as-is, or upgrade to Catalina or Big Sur before using Python 3.

Before you begin

Modern Authentication required for securing Microsoft Office apps: To secure Microsoft Office apps with this Device Trust solution they must be enabled to support Modern Authentication. For more information, see this Microsoft article. For information about securing Office 365 clients that use legacy protocols, see Office 365 Client Access Policies.
Device Trust isn't supported with all versions of Microsoft Office thick clients: This Device Trust solution has been tested to work with Microsoft Office thick client versions 16.13.1 and 16.15. However, it doesn't work with Microsoft Office thick client version 16.14 (build 180610).
Prevent iCloud from transferring the Okta keychain to other Apple devices: To prevent iCloud from transferring the Okta keychain from DT-secured macOS devices to other Apple devices, Okta strongly recommends that you create a Configuration Profile in Jamf Pro that disables Allow iCloud Keychain syncing. (Note: Be aware that disabling syncing blocks all keychain transfers.) See the Add the modified Okta Device Registration Task to Jamf Pro and distribute it to macOS devices.
Webview must have access to the device keychain: Device Trust for managed macOS computers works with any SAML/WS-Fed-enabled app that supports authentication through a webview. The webview in which authentication is performed must have access to the Okta Keychain on the device. To prevent end users from being prompted for consent when the certificate is used in the authentication flow, Okta allows the following apps. See Modify the default allowlist:
- Box
- Chrome
- Safari
- Microsoft Office
- Skype for Business
- Google Drive
- Slack
Per-device unbound certificate limit: A certificate becomes bound to a given user the first time that user accesses a device trust-secured application from a device trust-secured macOS device. Unused certificates are unbound. Okta can issue up to five unbound certificates to the device, one each time you perform the enrollment procedure. As a security precaution, Okta will not issue more than five unbound certificates to a given device. To avoid reaching the unbound certificate limit, ensure that users use the unbound certificates already on the device before you attempt to obtain more certificates through enrollment. If you reach the enrollment limit, the Syslog indicates an enrollment failure and the error message Maximum enrollment limit of 5 certificates for a device is reached appears in the JAMF log.
Per-org enrollment limit: A given macOS device can only be secured by the Device Trust configuration of a single Okta org. Put another way, macOS devices can't be secured by the Device Trust configuration of multiple Okta orgs simultaneously. This is because the client certificate issued to the device is signed by the CA of a particular org. This limit applies to Okta Preview and Production orgs.
Shared-terminal scenarios are not supported: This Device Trust solution doesn't support shared-terminal scenarios in which multiple Okta end users log in to the same account from the same macOS workstation.
Device Trust enrollment is not supported when Okta is in read-only mode: Devices cannot be enrolled in Device Trust if the cell in which your Okta org resides is in read-only mode.
End users may need to clear the browser cache: Some browsers (for example, Chrome) cache the Device Trust certificate. After the certificate is renewed automatically (once per year), these browsers may continue to present the expired certificate to Okta instead of the new certificate. In that case, end users are shown the Security requirements message and are denied access to Device Trust-secured apps. Okta recommends that you advise affected end users to clear browser cache by quitting and then restarting the browser (not just closing the browser window).
Apps secured by Device Trust are shown as locked on the Okta End-User Dashboard

On the Okta End-User Dashboard, a lock icon is shown beside apps secured by Device Trust under these conditions:
- The end users accessed the dashboard in a desktop or mobile browser (not in Okta Mobile).
- Device Trust is enabled for the org.
- The device is not trusted.
- The end user tried to access any Device Trust-secured app from their dashboard.
Apps must support Modern Authentication: To secure Microsoft Office apps with this Device Trust solution they must be enabled to support Modern Authentication. For more information, see the Microsoft article How modern authentication works for Office 2013 and Office 2016 client apps. Also see Office 365 Client Access Policies.
Make sure that certificates are installed in the keychain on the devices you have targeted for this Device Trust solution. If certificates are not installed and the Trusted setting is enabled in your App Sign On Policy, users are denied access to the app and are redirected to a security message advising them to contact their administrator. (You can configure the message to include a Learn more link to more information. See Step 1 — Enable the global Device Trust setting for your org).
Take care when disabling the macOS Device Trust setting: Do not disable the macOS Device Trust setting on the Security > Device Trust page if you have also configured an app sign on policy that allows trusted macOS devices. Otherwise, your Device Trust configuration will be in an inconsistent state. To disable Device Trust for your org, first remove any app sign on policies that contain a Device Trust setting, then disable macOS Device Trust in Security > Device Trust.
Before asking Okta Support to disable Device Trust: If you ask Okta Support to disable Device Trust capability for your org, make sure to first change the Device Trust setting in the app sign on policy rules to Any (Applications > app > Sign On). If you don't make this change and then later have Okta Support re-enable Device Trust capability for your org, the Device Trust setting in app sign on policy rules takes effect immediately, which you may not have expected.
Verify that clients can complete the MTLS handshake: The Mutual TLS certificate exchange (handshake) in this Device Trust flow occurs on Okta URLs that are separate from your Okta org URL (indicated by the wildcard character (*) in the following example). If you implement endpoint protection software, make sure to configure it in a way that does not block your clients from completing the certificate exchange with Okta. For example, if your organization uses an allowlist to limit outbound traffic, add these exact URLs to the allowlist, including the wildcard character (*):
*.okta.com
*.okta-emea.com

Procedures

STEP 1. Enable the global Device Trust setting for your org

In the Admin Console, go to Security > Device Trust
In the macOS Device Trust section, click Edit.
In the wizard that launches, select Enable macOS Device Trust.
Optional. In the Learn more field, you can enter an externally-accessible redirect URL where end users with untrusted devices can find more information. The security message shown to these end users will include a Learn more link that redirects to your specified URL.
If you choose not to specify a URL in this optional field, these end users will be shown the same message but without the Learn more link.
In Trust is established by, select Jamf Pro.
Enter information about the Jamf Pro API, such as the Jamf Pro tenant URL (for example, https://example.jamfcloud.com, not the API URL), credentials, and key.
This information allows Okta to verify that end user devices are managed by Jamf Pro at the time of certificate enrollment. For Jamf Pro, you need at least these READ privileges to access Jamf APIs in order for Okta to verify that the device is managed:
- Computers — READ
- Jamf Pro User Accounts & Groups — READ
- Users — READ

Important

Okta strongly recommends that you create a separate user for API access that is separate from the user your organization uses to access the Jamf Pro admin interface.

Click Test API credentials. A success message appears if a connection is established with your MDM provider's API.
Click Next.
On the Configure MDM Provider screen, click Download to obtain a python script. You'll modify the script later in STEP 2. Modify the Okta Device Registration Task.
To copy the provided Secret Key Value and Org URL to your clipboard, click the copy icon adjacent to the fields.

Important

Make a note of the provided Secret Key Value and Org URL, as this is the only time these will appear in Okta. Also, if you later want to edit your configuration and generate a new Secret Key through the Reset macOS Secret Key button, you must perform this procedure again.

Click Done.
Modify the downloaded Okta Device Registration Task as described in STEP 2.
The latest version of the Okta Device Registration Task is available from the Okta Admin Console Settings > Downloads page.

STEP 2. Modify the Okta Device Registration Task

Important

The Mutual TLS certificate exchange (handshake) in this Device Trust flow occurs on Okta URLs that are separate from your Okta org URL (indicated by the wildcard character (*) in the following example). If you implement endpoint protection software, make sure to configure it in a way that doesn't block your clients from completing the certificate exchange with Okta. For example, if your organization uses an allowlist to limit outbound traffic, add these exact URLs to the allowlist, including the wildcard character (*):

*.okta.com

*.okta-emea.com

On the Admin's computer, go to the Downloads folder and open the script you downloaded from Okta.
Modify the script by pasting in the Secret Key Value and Org URL you generated in STEP 1. Enable the global setting for your org.

When entering the key and the URL, retain the single quotation marks ( ' ) but replace the parentheses and the placeholder text with the actual Secret Key Value and Org URL, as shown in the following example:

For example, this is the unmodified script

For example, this is the modified script. Retain the single quotation marks but not the parentheses.

Optional. Modify the default app allowlist.

By default, the Okta Device Registration Task allows some popular apps so that end users aren't prompted for the keychain password when accessing them. To modify the default allowlist, see Modify the app allowlist.

Save the script.
Proceed to STEP 4. Add the modified Okta Device Registration Task to Jamf Pro and distribute it to macOS devices.

STEP 3. Install Python 3 and Device Trust dependencies

If Python 3 is already installed, go to step 2.

There are different ways to install Python 3. This step provides installation instructions using the macOS Xcode command line tool. Okta recommends that you use your preferred method.

Optional. Run the following script on your macOS machine to update your macOS environment to Python 3:

#!/bin/sh

echo "Checking for the existence of the Apple Command Line Developer Tools"

/usr/bin/xcode-select -p &> /dev/null

if [[ $? -ne 0 ]]; then

echo "Apple Command Line Developer Tools not found."

touch /tmp/.com.apple.dt.CommandLineTools.installondemand.in-progress;

installationPKG=$(/usr/sbin/softwareupdate --list | /usr/bin/grep -B 1 -E 'Command Line Tools' | /usr/bin/tail -2 | /usr/bin/awk -F'*' '/^ *\\*/ {print $2}' | /usr/bin/sed -e 's/^ *Label: //' -e 's/^ *//' | /usr/bin/tr -d '\n')

echo "Installing ${installationPKG}"

/usr/sbin/softwareupdate --install "${installationPKG}" --verbose

else

echo "Apple Command Line Developer Tools are already installed."

fi

exit

Install the Device Trust Dependencies. The updated macOS Device Registration Task requires “python3“ and “pip3“ alias on the device to point to the correct Python 3 installation.

Run the following script to install the required Device Trust dependencies:

#!/bin/sh

echo "Running pip3 install --upgrade pip"

sudo pip3 install --upgrade pip

echo "Running pip3 install pyobjc-framework-SystemConfiguration"

sudo pip3 install pyobjc-framework-SystemConfiguration

echo "pip3 install pyOpenSSL"

sudo pip3 install pyOpenSSL

exit

STEP 4. Add the modified Okta Device Registration Task to Jamf Pro and distribute it to macOS devices

The Okta Device Registration Task is a script that is distributed by Jamf Pro to the macOS devices you have targeted for this Device Trust solution. When deployed on the device, the Okta Device Registration Task does the following:

Registers with Okta to obtain a Device Trust certificate. Okta checks with Jamf Pro to make sure the device is managed.
Configures Chrome and Safari browsers and tested native apps on the device to present the certificate automatically during secure app access.
Schedules a lightweight task that runs once a day and whenever users log in to their computer. The task checks whether the Device Trust certificate is expired and tries to renew the certificate 30 days before expiry. Certificates are valid for 1 year.
During renewal, Okta performs checks similar to those that occur during registration, such as checking whether the device is managed before issuing a new certificate.
After the script runs on the device once, Jamf Pro removes it from the device automatically.
You can use the following query to determine which version of the Registration Task is installed on the device:
python3 ~/Library/Okta/okta_device_trust.py version

Create the workflows that make sense for your organization. Make sure the script successfully runs at least once to enroll the Okta certificate.

In Jamf Pro click the gear icon to go to All Settings.
Go to Computer Management > Scripts.
Create a new script and paste into it the Okta Device Registration Task you downloaded from Okta in STEP 1. Enable the global Device Trust setting for your org and modified in STEP 2. Modify the Okta Device Registration Task.
Click Save.
Create a policy to deploy the script to one or more Target Computers and/or Target Users:

Go to Computers > Policies.
Click + New.
Click General in the left pane.
Enter a policy a name in the Display Name field.
Select the following Trigger events that will initiate the policy:
- Enrollment Complete – the script runs immediately after devices complete the enrollment process.
- Recurring Check-in – the script runs according to the recurring check-in frequency configured in Jamf Pro.
Set the Execution Frequency to Once per computer per user.
Note: There are other approaches that you can implement in Jamf Pro to trigger deployment of the script (for example, Extension Attributes, which allow you to validate that the certificate is on the device and to deploy the certificate if it is missing).
Click Save.
Click Scripts in the left pane, and then click Configure.
Locate the script you created for this policy in step 3, and then click Add.
Click Scope.
In Target Computers and/or Target Users, specify the computers and users to whom the policy will apply.
Click Save.

Recommended. To prevent iCloud from transferring the Okta keychain from Device Trust-secured macOS devices to other Apple devices, you should create a Configuration Profile in Jamf Pro that disables Allow iCloud Keychain syncing.
Check the logs in Jamf Pro to verify that the Okta Device Registration Task ran successfully.
1. Go to Policies and click your policy.
2. Click Logs at the bottom of the screen.
Proceed to STEP 5. Configure app Sign On policy rules in Okta.

Revoke and remove Device Trust certificates

You may need to revoke an end user's Device Trust certificate(s) from the Okta Certificate Authority. This is recommended if the computer is lost or stolen, or if the end user is deactivated. To re-secure an end user's computer with Device Trust after revoking their Device Trust certificate(s), you need to remove the revoked certificate from their computer before enrolling a new certificate.

Steps 1 - 4 of this procedure revoke all Device Trust certificates from the Okta Certificate Authority that were issued to the end user. Certificate revocation does not remove existing certificates from macOS computers. In order to re-secure a macOS computer with Device Trust after revoking certificates, you must first remove any existing Device Trust certificate from the computer and then re-enroll the computer with a new certificate as detailed in Step 5. The Device Registration Task will not enroll a new certificate if another certificate (whether revoked or not) is present on the computer.
When an end user is deactivated Okta also revokes their Device Trust certificate from the Okta Certificate Authority automatically (but does not remove the certificate from their computer). To remove the certificate from the computer, use either removal method described in Step 5.

In the Admin Console, go to Directory > People.
Click the end user whose Device Trust certificate you want to revoke.
In the More Actions menu, click Revoke Trust Certificate.
Read the message that displays, and then click Revoke Trust Certificate.
To remove the Device Trust certificate for any reason (such as prior to re-securing a computer with Device Trust), first remove any existing Device Trust certificate from the computer. You can use a command line or create an uninstall script in Jamf Pro. Both uninstall methods remove all Device Trust related artifacts from the macOS device.

Note

If you plan to reuse the script that you downloaded and modified in Step 2 — Modify the Okta Device Registration Task, make sure to first remove the Org Token before using it. Also, the token is not necessary for the uninstall operation.

Remove through a command line — Open a terminal on the target computer and issue the command python <fileName>.py uninstall where <fileName> is the name of Okta Device Registration Task. For example, if the name of the Okta Registration Task is MacOktaDeviceRegistrationTaskSetup.1.0.2.py, you would issue this command:
python MacOktaDeviceRegistrationTaskSetup.1.0.2.py uninstall
Remove with an uninstall script — Create an uninstall script in Jamf Pro configured to pass the uninstall parameter. For details, see the procedure Adding a Script to Jamf Pro in Jamf Pro documentation.

View certificate enrollment logs

View logs in Jamf Pro

During deployment, the Okta Device Registration Task publishes logs in Jamf at three log levels (INFO, WARN, ERROR). To diagnose deployment issues, Jamf administrators can view deployment logs on a policy or individual computer basis. To generate more granular logs, use the verbose option as the Parameter Value in Jamf Pro.

In addition, end users can view log messages on their local macOS computers by having the Console app open while the script runs on their computer.

View logs on macOS computers

You can watch and monitor Okta-related log messages during certificate enrollment. The method depends on the operating system running on the device.

If running version 10.11.6 (OS X El Capitan):

Open Utilities > Console.
Click All Messages.
Type Okta in the search field and press Enter to filter all Okta-related messages.

If running either of the following operating systems:

macOS 10.12.6 (Sierra)
macOS 10.13.4 (High Sierra)

Open Utilities > Console.
Click your device under Devices in the left pane.
Type Okta in the search field and press Enter to filter all Okta-related messages.

To view past logs for all supported operating systems:

Open Utilities > Console.
Go to /var/log > asl in the left pane.
Select the date you want to search on.
Type Okta in the search field and press Enter to filter all Okta-related messages.

To see the system calls executed on the device, run the following command and then execute the Device Registration Task:

log stream --predicate 'eventMessage contains "okta"'

Modify the app allowlist

The Okta Device Registration Task allows some popular apps by default so that end users aren't prompted for the keychain password when trying to access them. You can customize the default allowlist as described in this procedure.

Keep in mind the following:

Keep a copy of your preferred allowlist. Your modified allowlist is overwritten whenever you push a new Okta Device Registration Task to your targeted macOS computers, so you'll have to recreate it.
If you add apps to the original Okta-defined allowlist, you should consider testing your modified allowlist with a subset of users before rolling it out to all users.
Unlike TeamIdentifiers for the other allowed apps, the TeamIdentifier for Safari is simply apple: (notice the colon) without a teamid: prefix.
You can allow any SAML/WS-Fed-enabled app that supports authentication through a webview. The webview in which authentication is performed must have access to the Okta Keychain on the device. The original Okta-provided allowlist currently includes the following apps:
- Box
- Chrome
- Safari
- Microsoft Office
- Skype for Business
- Google Drive
- Slack

Find the TeamIdentifier for the app(s) you want to allow:

On a macOS device that has the apps you want to allow, open a command line and list the apps in the Applications folder:

ls /Applications

Find an app's TeamIdentifier:

codesign -dv --verbose=4 /Applications/exampleapp.app

where exampleapp is the app you are investigating.

Locate the TeamIdentifier value in the output and make a note of it.

For example, here's how to find the team TeamIdentifier for RingCentral:

codesign -dv --verbose=4/App /Applications/RingCentral\ Meetings.app

And here's the output:

Modify the allowlist in the Okta Device Registration Task:

Example before modification

Allowlist includes the original Okta-defined allowlist:

Example after modification

Allowlist with RingCentral added:

Save your changes.
When appropriate, push the Okta Device Registration Task as described STEP 4 - Add the modified Okta Device Registration Task to Jamf Pro and distribute it to macOS devices.

Tip

Keep a copy of your preferred allowlist. Your modified allowlist is overwritten whenever you push a new Okta Device Registration Task to your targeted macOS computers, so you'll have to recreate it.

Known issues

Security requirements page not shown when accessing O365 native apps: End users with unmanaged macOS devices are not shown the Security requirements page when they try to access Office O365 native apps secured by this Device Trust solution. (This problem occurs only with Office Native apps; it doesn't occur when trying to access O365 apps through desktop browsers like Chrome and Safari.)
Problem accessing Google Backup and Sync app: When signing in to the Backup and Sync app (part of Google Drive), the authentication flow stops on the Google Account page instead of progressing to the app. Google is aware of this issue. To complete signing in, click the Sign in with your browser instead link in the lower portion of the page.