Tag: Subject distinguished name

Dirk-jan Mollema recently presented an attack that can be used to obtain a certificate for highly privileged accounts via Intune . This can then be used to compromise the entire Active Directory environment.

The attack is similar in its basic features to what I have already described in the article "From Zero to Enterprise Administrator through Network Device Enrollment Service (NDES) - and What to Do About It " and in the article "Attack vector on Active Directory directory service via smart card logon mechanism " (generally also known as ESC1 ).

What is new, however, is to utilize the Mobile Device Management (MDM) system - in this case Microsoft Intune - accordingly.

What is not new, however, is what can be done with the TameMyCerts Policy Module for Active Directory Certificate Services to drastically reduce the attack surface...

Continue reading "Attack on the Active Directory via Microsoft Intune - and how it can be contained with TameMyCerts"

Nowadays, it is essential to protect the authentication of devices on the company network and administrative interfaces. As a rule, digital certificates are used for this purpose.

Printers therefore also generally require digital certificates in order to be operated securely. From a certain number of devices, there is no getting around automatic certificate distribution.

Some printer manufacturers offer centralized management solutions for certificate distribution.

Unfortunately, it has been shown time and again that the secure handling of digital certificates requires a great deal of knowledge, experience and care, which is often not the case.

Continue reading "How securing printers can turn into a security disaster - and how the TameMyCerts Policy Module for Active Directory Certificate Services (ADCS) can prevent it"

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 then, web server certificates without a Subject Alternative Name in the form of a dNSName have been rejected by Google Chrome and other Chromium -based browsers (i.e. also Microsoft Edge ). Other browser manufacturers quickly adopted this approach, so that this problem now affects all popular browsers.

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

Companies use Mobile Device Management (MDM) products for managing, configuring and updating 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 under the brand name AirWatch)
• Ivanti MobileIron UEM
• Jamf Pro
• Baramundi Enterprise Mobility Management
• BlackBerry Enterprise Mobility Suite
• Sophos Mobile Control
• SOTI MobiControl
• Samsung Knox
• IBM MaaS360

Continue reading "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"

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, its 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 of issued certificates.

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

With the Chromium project and products based on it such as Google Chrome and Microsoft Edge, Google has moved to enforce RFC 2818 , adopted in 2000, and to no longer trust certificates that no longer fulfill this requirement.

For us, the following sentence is of great significance:

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

Continue reading "Automatically enter DNS names in the Subject Alternative Name (SAN) of issued certificates - with the TameMyCerts Policy Module for Microsoft Active Directory Certificate Services (AD CS)"

On the internet, there are unfortunately far too many instructions (the big players are not excluded from this , not even Microsoft itself or the grandmaster 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 forest .

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

Assume the following scenario:

• A new certification authority certificate is requested for a subordinate certification authority and issued by the parent certification authority.
• The Subject Distinguished Name (Subject DN) is identical to that of the previous certification authority certificate.
• However, the installation of the certification authority certificate fails with the following error message:

An error was detected while configuring Active Directory Certificate Services.
The Active Directory Certificate Services Setup Wizard will need to be rerun to complete the configuration.
The new certificate subject name does not exactly match the active CA name.
Renew with a new key to allow minor subject name changes: The parameter is incorrect. 0x80070057 (WIN32: 87 ERROR_INVALID_PARAMETER).

Continue reading "Installation of a new certification authority certificate fails with error code "ERROR_INVALID_PARAMETER""

Usually, the encoding of characters and strings in certificates is not a topic of great interest to the users of a PKI. However, there are cases where the default settings of the certification authority do not provide the desired results.

Continue reading "Character encoding in the Subject Distinguished Name of certificate requests and issued certificates"

As the operator of a certification authority, you are (among other things) responsible for the identification of the enrollees and the confirmation of the requested identities . The fact that this task is carried out conscientiously and without error is the central pillar of the trust placed in the certification authority. Well-known companies have already failed at this task , even had to file for insolvency as a result of misissuances and/or were severely punished by the big players in the market.

In many cases, we as (Microsoft) PKI operators in companies (regardless of the associated quality) are able to delegate our task of uniquely identifying an enrollee to the Active Directory. In many cases, however, we unfortunately also have to instruct our certification authority(ies) to simply issue everything that is requested.

Continue reading "A policy module to tame them all: Introducing the TameMyCerts Policy Module for Microsoft Active Directory Certificate Services"

When configuring a certificate template, one must decide on the intended certificate content, i.e., among other things, which identities are confirmed by the certificates and how they are mapped.

In the "Subject Name" tab of the certificate template configuration dialog, you can configure how the identity confirmed by the certificate is mapped.

Continue reading "About the "Build this from Active Directory information" option for certificate templates"

Name constraints are part of the X.509 standard and are described in RFC 5280 . They are a tool that can be used as part of qualified subordination to control the scope of a certification authority certificate in a fine-grained manner.

Continue reading "Basics: Name Constraints"

Assume the following scenario:

• An Appx package is to be signed.
• For this purpose, SignTool.exe is used.
• The code signing certificate used was recently renewed.
• The signing process with the new code signing certificate fails with the following error message:

"Error: SignerSign() failed." (-2147024885/0x8007000b) 

Continue reading "Code signing of Appx packages via SignTool.exe fails with error code 0x8007000b (ERROR_BAD_FORMAT)"

In the following, I would like to present a highly dangerous PKI configuration, perhaps not necessarily known to the general public, which can probably be encountered quite frequently in this way in corporate networks.

I show how, by exploiting various unfortunate circumstances in the Windows PKI, it is possible to elevate privileges from mere network access to complete Active Directory takeover.

The initial point of attack in this example is the Network Device Enrollment Service (NDES).

Continue reading "From Zero to Enterprise Administrator through Network Device Enrollment Service (NDES) - and What to Do About It"

The capolicy.inf contains basic settings that can or should be specified before installing a certification authority. Put simply, no certification authority should be installed without it.

Continue reading "Basics: Configuration file for the certification authority (capolicy.inf)"