Uwe Gradenegger - Uwe Gradenegger

How the TameMyCerts Policy Module for Active Directory Certificate Services (ADCS) can repair incoming certificate requests to make them RFC compliant

Starting with version 58, Google has decided to remove support for the Subject Distinguished Name of web server certificates in the Chrome browser and instead only accept certificates with Subject Alternative Name.

Since this moment, web server certificates without a subject alternative name in the form of a dNSName rejected by Chrome. Other browser manufacturers quickly adopted this approach, meaning that this problem now affects all popular browsers (including Microsoft Edge).

How the TameMyCerts Policy Module for Active Directory Certificate Services (ADCS) can help establish digital signature processes in the company

Nowadays, many companies want to rely on paperless processes to speed up internal approval and signature processes. In times when most employees are working from home, this has become even more important.

Although the Microsoft certification authority is able to implement automatic certificate issuance processes, their ability to influence the content of the certificate is severely limited.

The TameMyCerts Policy Module for Microsoft Active Directory Certificate Services (AD CS) allows the definition of extended Rules for the Subject Distinguished Name and also the Subject Alternative Name certificates issued.

How the TameMyCerts Policy Module for Active Directory Certificate Services (ADCS) can help secure scenarios with Microsoft Intune and other Mobile Device Management (MDM) systems

Companies use Mobile Device Management (MDM) products to manage, configure and update mobile devices such as smartphones, tablet computers or desktop systems via the Internet (Over-the-Air, OTA).

Common mobile device management products are:

Microsoft Intune
VMware Workspace One (previously known as AirWatch)
Ivanti MobileIron UEM
Jamf Pro
Baramundi Enterprise Mobility Management
BlackBerry Enterprise Mobility Suite
Sophos Mobile Control
SOTI MobiControl

How the TameMyCerts Policy Module for Active Directory Certificate Services (ADCS) can detect and prevent attacks against the ESC6 and ESC7 attack vectors

With the supposedly good intention of making it possible to issue such certificate requirements with a SAN, guess unfortunately much at many Instructions to set the flag on the certification body EDITF_ATTRIBUTESUBJECTALTNAME2 to activate.

If this flag is activated, a very large attack surface is offered, as any applicant can now instruct the certification authority to issue certificates with any content. This type of attack is known in the security scene as ESC6 and ESC7 known.

How the TameMyCerts Policy Module for Active Directory Certificate Services (ADCS) can prevent attacks against the ESC1 attack vector

Attacks on Microsoft certification authorities can be aimed at exploiting authorizations on certificate templates. In many cases, certificate templates must be configured to grant the applicant the right to apply for any identities. This can lead to the attacker taking over the identities of Active Directory accounts and subsequently to the elevation of rights. Attacks of this kind are known in the security scene as "ESC1" is labeled.

Automatically enter DNS names in the Subject Alternate Name (SAN) of issued certificates - with the TameMyCerts Policy Module for Microsoft Active Directory Certificate Services (ADCS)

Google is a major player with the Chromium project and products based on it such as Google Chrome and Microsoft Edge have moved to implement the RFC 2818 and to no longer trust certificates that no longer fulfill this requirement.

For us, the following sentence is of great explosiveness:

If a subjectAltName extension of type dNSName is present, that MUST be used as the identity. Otherwise, the (most specific) Common Name field in the Subject field of the certificate MUST be used. Although the use of the Common Name is existing practice, it is deprecated and Certification Authorities are encouraged to use the dNSName instead
https://tools.ietf.org/html/rfc2818

Change the Subject Alternative Name (SAN) of a certificate before it is issued - but do it securely!

In net circulate unfortunately much at many Instructions (also the big players are not excluded from this, not even Microsoft itself or the Grand Master Komar), which fatally recommend that the flag EDITF_ATTRIBUTESUBJECTALTNAME2 should be set on the certification authority - supposedly to be able to issue certificates with Subject Alternative Name (SAN) extension for manually submitted certificate requests.

Unfortunately, this procedure is not only unnecessary, it also has some unpleasant side effects, which in the worst case can help an attacker to take over the entire Active Directory structure.

Basics: Delta revocation lists

Certificate revocation lists (CRLs) are used to remove issued certificates from circulation before the end of their validity period.

A CRL is a signed list of the serial numbers of certificates that have been revoked by the certification authority. The revocation list has an expiration date (usually a few days short) and is reissued and signed by the associated certification authority at regular intervals.

Certificate revocation lists can reach a considerable size if the volume of revoked certificates is high (as a rule of thumb, you can expect about 5 megabytes per 100,000 entries). The regular download of large certificate revocation lists by subscribers can generate a large network load. To address this problem, there is the concept of delta revocation lists.

Roles in a public key infrastructure

Understanding the roles involved is essential for designing a public key infrastructure.

The term "public key infrastructure" encompasses much more than the technical components and is often misleadingly used.

In summary, a public key infrastructure is both an authentication technology and the totality of all the components involved.

Deconstruction of an Active Directory integrated certification authority (Enterprise CA)

There are many instructions for setting up and commissioning IT services. However, the associated instructions for decommissioning are usually forgotten.

The following describes how to correctly decommission a certification authority (Enterprise Certification Authority) integrated into Active Directory.

Checking the integrity of backups of the certification authority database

Within the framework of the creation of a Backup of a certification authority The question may arise as to how to ensure that the integrity of the certification authority database backup is guaranteed so that it can be properly restored can be.

The Certification Authority database is available in a Microsoft JET Blue database engine (also known as Extensible Storage Engine, ESE). Their working and backup files have the extension .edb and can be created with the operating system tool esentutl be managed.

Configuring a Certificate Template for Online Responders (OCSP) Response Signing Certificates

To use the Online Certificate Status Protocol (OCSP), it is necessary to configure an appropriate certificate template.

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.

Logins via the Network Policy Server (NPS) fail with reason "Authentication failed due to a user credentials mismatch. Either the user name provided does not map to an existing user account or the password was incorrect."

Assume the following scenario:

A certificate-based login is performed with user or computer accounts to connect them to a wireless (IEEE 802.11 or Wireless LAN) or wired network (IEEE 802.3), or a remote access connection (e.g. DirectAccess, Routing and Remote Access (RAS), Always on VPN) to register.
The company uses Microsoft's Network Policy Server (NPS) as its Authentication, Authorization and Accounting (AAA) server.
Logging on to the network is no longer possible.
The network policy server logs the following event when a login attempt is made:

Network Policy Server denied access to a user. [...] Authentication failed due to a user credentials mismatch. Either the user name provided does not map to an existing user account or the password was incorrect.

The network policy server has denied access to a user. [...] Authentication error due to mismatch of user credentials. The specified username is not associated with an existing user account, or the password was incorrect.

Unable to install Network Device Enrollment Service (NDES) at a site with read-only domain controllers

Assume the following scenario:

A network device registration service (NDES) is to be implemented in the network.
Read Only Domain Controllers (RODC) are located at the Active Directory site of the NDES server.
NDES role configuration fails with the following error message:

Failed to add the following certificate templates to the enterprise Active Directory Certificate Service or update security settings on those templates:
EnrollmentAgentOffline
CEPEncryption
IPSEC(Offline request)
A referral was returned from the server. 0x8007202b (WIN32:8235 ERROR_DS_REFERRAL)