Azure Active Directory certificate-based authentication on iOS

Devices that run iOS can use certificate-based authentication (CBA) to authenticate to Azure Active Directory (Azure AD) using a client certificate on their device when connecting to:

  • Office mobile applications such as Microsoft Outlook and Microsoft Word
  • Exchange ActiveSync (EAS) clients

Azure AD CBA is supported for certificates on-device on native browsers and on Microsoft first-party applications on iOS devices.

Prerequisites

  • iOS version must be iOS 9 or later.
  • Microsoft Authenticator is required for Office applications and Outlook on iOS.

Support for on-device certificates and external storage

On-device certificates are provisioned on the device. Customers can use Mobile Device Management (MDM) to provision the certificates on the device. Since iOS doesn't support hardware protected keys out of the box, customers can use external storage devices for certificates.

Supported platforms

  • Only native browsers are supported
  • Applications using latest MSAL libraries or Microsoft Authenticator can do CBA
  • Edge with profile, when users add account and logged in a profile will support CBA
  • Microsoft first party apps with latest MSAL libraries or Microsoft Authenticator can do CBA

Browsers

Edge Chrome Safari Firefox

Microsoft mobile applications support

Applications Support
Azure Information Protection app
Company Portal
Microsoft Teams
Office (mobile)
OneNote
OneDrive
Outlook
Power BI
Skype for Business
Word / Excel / PowerPoint
Yammer

Support for Exchange ActiveSync clients

On iOS 9 or later, the native iOS mail client is supported.

To determine if your email application supports Azure AD CBA, contact your application developer.

Support for certificates on hardware security key (preview)

Certificates can be provisioned in external devices like hardware security keys along with a PIN to protect private key access. Microsoft's mobile certificate-based solution coupled with the hardware security keys is a simple, convenient, FIPS (Federal Information Processing Standards) certified phishing-resistant MFA method.

As for iOS 16/iPadOS 16.1, Apple devices provide native driver support for USB-C or Lightning connected CCID-compliant smart cards. This means Apple devices on iOS 16/iPadOS 16.1 will see a USB-C or Lightning connected CCID-compliant device as a smart card without the use of additional drivers or 3rd party apps. Azure AD CBA will work on these USB-A or USB-C, or Lightning connected CCID-compliant smart cards.

Advantages of certificates on hardware security key

Security keys with certificates:

  • Can be used on any device, and don't need a certificate to be provisioned on every device the user has
  • Are hardware-secured with a PIN, which makes them phishing-resistant
  • Provide multifactor authentication with a PIN as second factor to access the private key of the certificate
  • Satisfy the industry requirement to have MFA on separate device
  • Help in future proofing where multiple credentials can be stored including Fast Identity Online 2 (FIDO2) keys

Azure AD CBA on iOS mobile with YubiKey

Even though the native Smartcard/CCID driver is available on iOS/iPadOS for Lightning connected CCID-compliant smart cards, the YubiKey 5Ci Lightning connector is not seen as a connected smart card on these devices without the use of PIV (Personal Identity Verification) middleware like the Yubico Authenticator.

One-time registration prerequisite

  • Have a PIV-enabled YubiKey with a smartcard certificate provisioned on it
  • Download the Yubico Authenticator for iOS app on your iPhone with v14.2 or later
  • Open the app, insert the YubiKey or tap over near field communication (NFC) and follow steps to upload the certificate to iOS keychain

Steps to test YubiKey on Microsoft apps on iOS mobile

  1. Install the latest Microsoft Authenticator app.
  2. Open Outlook and plug in your YubiKey.
  3. Select Add account and enter your user principal name (UPN).
  4. Click Continue and the iOS certificate picker will appear.
  5. Select the public certificate copied from YubiKey that is associated with the user’s account.
  6. Click YubiKey required to open the YubiKey authenticator app.
  7. Enter the PIN to access YubiKey and select the back button at the top left corner.

The user should be successfully logged in and redirected to the Outlook homepage.

Troubleshoot certificates on hardware security key

What will happen if the user has certificates both on the iOS device and YubiKey?

The iOS certificate picker will show all the certificates on both iOS device and the ones copied from YubiKey into iOS device. Depending on the certificate user picks they will be either taken to YubiKey authenticator to enter PIN or directly authenticated.

My YubiKey is locked after incorrectly typing PIN 3 times. How do I fix it?

  • Users should see a dialog informing you that too many PIN attempts have been made. This dialog also pops up during subsequent attempts to select Use Certificate or smart card.
  • YubiKey Manager can reset a YubiKey’s PIN.

This issue happens because of certificate caching. We are working to add a fix to clear the cache. As a workaround, clicking cancel and restarting the login flow will let the user choose a new certificate and successfully login.

Azure AD CBA with YubiKey is failing. What information would help debug the issue?

  1. Open Microsoft Authenticator app, click the three dots icon in the top right corner and select Send Feedback.
  2. Click Having Trouble?.
  3. For Select an option, select Add or sign into an account.
  4. Describe any details you want to add.
  5. Click the send arrow in the top right corner. Note the code provided in the dialog that appears.

How can I enforce phishing-resistant MFA using a hardware security key on browser-based applications on mobile?

Certificate based authentication and Conditional Access authentication strength capability makes it powerful for customers to enforce authentication needs. Edge as a profile (add an account) will work with a hardware security key like YubiKey and conditional access policy with authentication strength capability can enforce phishing-resistant authentication with CBA.

CBA support for YubiKey is available in the latest Microsoft Authentication Library (MSAL) libraries, any third-party application that integrates the latest MSAL, and all Microsoft first party applications can leverage CBA and Conditional Access authentication strength.

Supported operating systems

Operating system Certificate on-device/Derived PIV Smart cards
iOS Supported vendors only

Supported browsers

Operating system Chrome certificate on-device Chrome smart card Safari certificate on-device Safari smart card Edge certificate on-device Edge smart card
iOS

Security key providers

Provider iOS
YubiKey

Known issue

On iOS, users will see a "double prompt", where they must click the option to use certificate-based authentication twice. We're working to create a seamless user experience.

Next steps