Microsoft Intune - Uwe Gradenegger

Sending S/MIME encrypted messages with Outlook for iOS is not possible: "There's a problem with one of your S/MIME encryption certificates."

Assume the following scenario:

The certificates were transferred to the smartphone via the Intune Connector.
Reading encrypted messages works.
However, when enabling encryption for outgoing messages, the following error message is displayed:

There's a problem with one of your S/MIME encryption certificates. Contact your IT help desk for more info.

There is a problem with one of your S/MIME encryption certificates. Contact your IT help desk for more information.

Requesting certificates for endpoints managed with Microsoft Intune

In a networked world, it has become standard to work from anywhere, and also to work with mobile end devices such as smartphones or tablets in addition to classic desktop computers. Such end devices are usually connected by means of Mobile Device Management (MDM) managed by systems such as Microsoft Intune.

In most cases, users of mobile devices need digital certificates to prove their identity in order to gain access to corporate resources. Thus, it is necessary to provide these devices with an automatable yet secure interface for applying for these certificates.

Transferring S/MIME certificates to Microsoft Intune

In a modern networked world, the confidential transmission of messages in the corporate environment is essential for business success. Despite their Age it is still impossible to imagine modern corporate communications without e-mail. However, its use has changed significantly over the decades.

Nowadays, it is common to be able to read and write business e-mails on mobile devices such as smartphones and tablets. Such end devices are usually connected by means of Mobile Device Management (MDM) managed by systems such as Microsoft Intune.

For the encryption of e-mail messages, companies usually use the Secure / Multipurpose Internet Message Extensions (S/MIME) standard and provide their users with the corresponding certificates. How do these certificates get to the end devices of the users in a scalable way?

Configuring the Network Device Enrollment Service (NDES) to work with a domain account.

The Network Device Enrollment Service (NDES), because it implements the web-based Simple Certificate Enrollment Protocol (SCEP), is mapped as a web application in Microsoft Internet Information Service (IIS). Here, the service runs in an application pool called "SCEP". In many cases it is sufficient to use the integrated application pool identity for it.

However, there are cases where you want to use a domain account. An example of this is the Certificate Connector for Microsoft Intune, which requires this.

The Certificate Connector for Microsoft Intune throws the error message "ArgumentException: String cannot be of zero length" during configuration.

Assume the following scenario:

An NDES server has been set up for use with Microsoft Intune.
The configuration of the Intune Certificate Connector cannot be completed because the following error message is thrown:

Error in Microsoft Intune Certificate Connector configuration. No changes were made to feature or proxy settings.
Unexpected error: System.ArgumentException: The string cannot have a length of 0 (zero).
Parameter name: name
  for System.Security.Principal.NTAccount.ctor(String name)

Issue certificates with shortened validity period

Sometimes it is necessary to issue certificates with a shorter validity period than configured in the certificate template. Therefore, you may not want to reconfigure the certificate template right away or create another certificate template.

S/MIME with the Outlook app for Apple IOS and Android only possible with devices managed via Intune

If you want to make S/MIME certificates available to your users on the smartphone as well, you may be surprised to discover that this is not possible with the Outlook app unless you also use Microsoft Intune as a management solution for the devices.

Microsoft has published in an article "Sensitivity labeling and protection in Outlook for iOS and Android" now clarified that this is due to the respective system architecture.

List of use cases for certificates that require specific Cryptographic Service Providers (CSP) or Key Storage Providers (KSP).

Windows Server 2008, along with NSA Suite B algorithms (also known as Cryptography Next Generation, CNG) with Key Storage Providers, introduced a new, modern interface for generating, storing, and using private keys in the Windows ecosystem.

In most cases, it does not matter which CSP or KSP is used for certificates. However, some applications will not work or will not work correctly if the wrong provider is chosen.

Below is a list of use cases I know of for certificates that only work with a specific Cryptographic Service Provider (CSP) or Key Storage Provider (KSP).

Basics: Restricting Extended Key Usage (EKU) in Certification Authority Certificates

A useful hardening measure for Certification Authorities is to restrict the Certification Authority certificates so that they are only used for the actually issued extended key usage (Extended Key Usage) becomes familiar.

In the event of a compromise of the certification authority, the damage is then (at least) limited to the defined extended key usages.

The Smart Card Logon Extended Key Usage, which is of interest for many attacks (in conjunction with the certification authority's membership in NTAuthCertificates) would then only be present in the certification authority certificate of the certification authority that actually issues such certificates.

The Network Device Enrollment Service (NDES) administration web page (certsrv/mscep_admin) reports "You do not have sufficient permission to enroll with SCEP. Please contact your system administrator."

Assume the following scenario:

An NDES server is configured on the network.
When calling the administration web page (certsrv/mscep_admin) the following message appears:

You do not have sufficient permission to enroll with SCEP. Please contact your system administrator.