Configure FIDO2 security key restrictions

This week is all about FIDO2 security keys. More specifically about configuring FIDO2 security key restrictions to make sure that users can only use specific FIDO2 security keys, or to prevent users from using specific FIDO2 security keys. That makes this blog post a follow up on this post about enabling password-less sign-in with security keys. In this post I’ll provide a short introduction about the FIDO2 security key AAGUID (and how to find it), followed by the steps to configure the FIDO2 security key restrictions. I’ll end this post by looking at the end-user experience.

FIDO2 security key AAGUID

According to the FIDO2 specification each authenticator should provide an Authenticator Attestation GUID (AAGUID) during attestation. An AAGUID is a 128-bit identifier that indicates the type (for example make and model) of the authenticator. The AAGUID should be identical across identical authenticators that are created by the same manufacturer, and should be different from the AAGUID of authenticators of different types and different manufacturers. To ensure this, the AAGUID is randomly generated.

The AAGUID of a FIDO2 security can be used to configure restrictions for the end-users, by either only allowing specific FIDO2 security keys based on their AAGUID or by only blocking specific FIDO2 security keys based on their AAGUID. To help with that some manufactures (like Yubico) provide a complete list of the AAGUIDs of their FIDO2 security keys.

When this information is not easily available, it’s possible to find the AAGUID by using the get_info.py script that’s available in the Python-FIDO2 library provided by Yubico. That script can make the device WINK, which will provide the information about the FIDO2 security that includes the AAGUID. Below (in Figure 1) is an example of FIDO2 security key that is sending a WINK. The information provided when sending the WINK includes the AAGUID and on some devices also the FIDO2 security key name and model.

Another method to retrieve the AAGUID of a FIDO2 security key is to register the security key as a sign-in method. That can be achieved via the Security method section of My account. After registering the security key, the AAGUID can be found with the security key as shown below in Figure 2.

Below is an overview of the FIDO2 security keys that I’ve had available during testing, including their AAGUID.

FIDO2 security keyFIDO2 AAGUID
Yubikey 5 NFC (Firmware version: 5.1.x)fa2b99dc9e3942578f924a30d23c4118
Yubikey 5C (Firmware version: 5.1.x)cb69481e8ff7403993ec0a2729a154a8
Feitian ePass FIDO-NFC Security Key K9ee041bce25e54cdb8f86897fd6418464
Feitian BioPass FIDO2 Security Key K2677010bd7212a4fc9b236d2ca5e9d4084
Feitian BioPass FIDO2 Security Key K2777010bd7212a4fc9b236d2ca5e9d4084
Feitian BioPass FIDO2 Security Key K3312ded7454bed47d4abaae713f51d6393
eWBM Goldengate Security Key G31095442b2ef15e4defb270efb106facb4e
eWBM Goldengate Security Key G32087dbc5a14c944dc88a4797d800fd1f3c

Configuring FIDO2 security key restriction

The configuration steps are pretty straightforward and can be achieved by adjusting the FIDO2 Security Keys authentication method. That can be achieved by performing the 3 steps mentioned below. Those steps are fully focussed on configuring the KEY RESTRICTION POLICY. When the FIDO2 Security Keys authentication method is not yet enabled, make sure to also perform the required actions for that. In other words, make sure to enable the authentication method and configure the target of the authentication method.

  1. Open the Azure portal and navigate to Azure Active Directory Security > Authentication methods Authentication method policy (preview) to open the Authentication methods – Authentication method policy (preview) blade
  2. On the Authentication methods – Authentication method policy (preview) blade, select FIDO2 Security Key to open the FIDO2 Security Key settings section
  3. On the FIDO2 Security Key settings section, provide at least the following information (see also Figure 3 for an overview of the available options) and click Save
  • Enforce key restrictions: Select Yes
  • Restrict specific keys: Select Block to create a key restriction policy that will blacklist the specified AAGUIDs and select Allow to create a key restriction policy that will whitelist the specified AAGUIDs
  • Click Add AAGUID and specify the specific AAGUIDs that should be blocked (blacklisted) or allowed (whitelisted)

End-user experience

Let’s end this post by having a look at the end-user experience. When the end-user wants to register a security key (either not on whitelist, or on the blacklist), via the Security info section in My Profile, the end-user can walk through the complete process of adding another sign-in method. At the end of the process, the end-user will receive an error with the message that the particular key type has been blocked by the organization. The message doesn’t provide a list of supported security keys.

More information

For more information about password-less authentication deployment and password-less FIDO2 security keys, refer to the following articles:

Enable password-less sign-in with security keys

This week is all about enabling password-less sign-in with security keys on Windows 10. I know that a lot has been written about that subject already, but it’s that big that it still deserves a spot on my blog. Especially the Microsoft Intune configuration belongs on my blog. In this post I’ll show the required configurations that should be performed, by an administrator and the the user, to enable the user to use a security key as a sign-in method. My user will use a Yubikey 5 NFC security key. I’ll start this post with the authentication method policy that should be configured in Azure AD, followed by the steps for a user to register a security key. I’ll end this post by showing the different methods to configure security keys a sign-in method on Windows 10, by using Microsoft Intune, and the end-user experience.

Keep in mind that the best experience, for password-less sign-in with security keys, is on Windows 10 version 1903 or higher. This is caused by the fact that the PassportForWork CSP setting is introduced in Windows 10 version 1903.

Configure the authentication method

The first step in enabling password-less sign-in with security keys, is configuring the authentication method. Within Azure AD there is the Authentication method policy available, which is currently still in preview, that can be used to enable password-less authentication for users. Either all users, or a specific group of users. Within that policy it’s currently possible to enable FIDO2 security keys and Microsoft Authentication as password-less authentication options. The following three steps walk through the process of enabling FIDO2 security keys as a password-less authentication option for all users.

  1. Open the Azure portal and navigate to Azure Active Directory Authentication methods > Authentication method policy (preview) to open the Authentication methods – Authentication method policy (preview) blade
  2. On the Authentication methods – Authentication method policy (preview) blade, select FIDO2 Security Key to open the FIDO2 Security Key settings blade
  3. On the FIDO2 Security Key settings blade, provide the following information and click Save
  • ENABLE: Select Yes
  • TARGET: Select All users (use Select users to only enable for specific users)
  • Allow self-service set-up: Select Yes
  • Enforce attestation: Select Yes
The key restriction policy settings are not working yet and should be left default for now.

Register security key as sign-in method

The second step is that the user must register a security key that can be used as sign-in method. That does require that the user already registered an Azure MFA method. If not, the user should first register an Azure MFA method. After registering an Azure MFA method, the following nine steps will walk the user through the process of adding an USB security key.

  1. Open the My Profile and navigate to Security info to open the Security info section
  2. On the Security info section, click Add method to open a dialog box
  3. On the Add method page, select Security key and click Add
  4. On the Security key page, select USB device and click Next
  5. A browser session will open to register the security key
  6. Insert the security key, touch it, provide a PIN and click Next
  7. Touch the security key another time and click Allow
  8. Provide a name for the security key and click Next
  9. On the Your all set page, click Done

After registering a security key as a sign-in method, the user can already use the security key as a sign-in method for browser sessions.

Configure security keys as a sign-in option

The third and last step is to configure security keys as a sign-in option on Windows devices. Within Microsoft Intune there are multiple methods for enabling security keys as a sign-in option on Windows 10 devices. It’s also good to keep in mind that, even though password-less sign-in is supported starting with Windows 10, version 1809, the following configuration options are all for Windows 10, version 1903 or later. The reason for that is actually quite simple, as the required setting (UseSecurityKeyForSignin) is introduced in the PassportForWork CSP with Windows 10, version 1903.

Using Windows enrollment (Windows Hello for Business) settings

The first configuration option is by using the Windows Hello for Business settings that are available within the Windows enrollment settings. Those settings actually enable the administrator to configure the use of security keys for sign-in independent of actually configuring Windows Hello for Business. The biggest challenge with this approach is that it can’t be slowly implemented, as it’s all or nothing. The following two steps walk through this configuration.

  1. Open the Azure portal and navigate to Microsoft Intune Device enrollmentWindows enrollment > Windows Hello for Business to open the Windows Hello for Business blade
  2. On the Windows Hello for Business blade, select Enabled with Use security keys for sign-in and click Save

This setting requires Windows 10, version 1903, or later, and is not dependent on configuring Windows Hello for Business.

Using Device configuration (Identity protection) settings

The second configuration option is by using the Identity protection device configuration profile. The Identity protection device configuration profile, provides the same configuration options as the Windows Hello for Business settings. The biggest difference is that the Identity protection device configuration profile can be implemented by using groups, which allows a phased implementation (and differentiation). The following four steps walk through this configuration.

  1. Open the Azure portal and navigate to Microsoft Intune Device configuration Profiles to open the Devices configuration – Profiles blade
  2. On the Devices configuration – Profiles blade, click Create profile to open the Create profile blade
  3. On the Create profile blade, provide the following information and click Create
  • Name: Provide a valid name
  • Description: (Optional) Provide a valid description
  • Platform: Windows 10 and later
  • Profile type: Identity protection
  • Settings: See step 4
  1. On the Windows Hello for Business blade, select Enable with Use security keys for sign-in and click OK;

This setting requires Windows 10, version 1903, or later, and is not dependent on configuring Windows Hello for Business

Use Device configuration (Custom) settings

The third and last option is by using a Custom device configuration profile. That Custom device configuration profile, is actually identical to the Identity protection device configuration profile. The only difference is that it’s a OMA-URI configuration, so no simple UI switch. Even though it’s good to mention this option, to remember what the actual configuration is that’s done on the background. The following four steps walk through this configuration.

  1. Open the Azure portal and navigate to Microsoft Intune Device configuration Profiles to open the Devices configuration – Profiles blade
  2. On the Devices configuration – Profiles blade, click Create profile to open the Create profile blade;
  3. On the Create profile blade, provide the following information and click Create;
  • Name: Provide a valid name
  • Description: (Optional) Provide a valid description
  • Platform: Windows 10 and later
  • Profile type: Identity protection
  • Settings: See step 4
  1. On the Custom OMA-URI Settings blade, provide the following information and click Add to open the Add row blade. On the Add row blade, provide the following information and click OK (and click OK in the Custom OMA-URI blade);
  • Name: Provide a valid name
  • Description: (Optional) Provide a valid description
  • OMA-URI: ./Device/Vendor/MSFT/PassportForWork/SecurityKey/UseSecurityKeyForSignin
  • Data type: Select Integer;
  • Value: 1

This setting requires Windows 10, version 1903, or later, and is not dependent on configuring Windows Hello for Business

End-user experience

Let’s end this post by having a look at the end-user experience. Below on the first row it starts with a static example of the sign-in experience on Windows 10 and in a browser. The second row is an example of the password-less sign-in experience of an user on Windows 10, version 1903, using a Yubikey 5 NFC security key. I’m specifically showing the experience when using the Other user sign-in option, as it will show that the user doesn’t need to provide a username nor a password. The user only needs to have the security key and the related PIN.

More information

For more information about password-less sign-in on Windows 10, see this doc named Enable passwordless security key sign in for Azure AD (preview).