Tag: ESC1

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"

Attacks on Microsoft certification authorities can be aimed at exploiting permissions on certificate templates. In many cases, certificate templates must be configured to grant the enrollee the right to request arbitrary identities. This can lead to the attacker taking over the identities of Active Directory accounts and subsequently to privilege escalation. Attacks of this type are known in the security scene as "ESC1 ".

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

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"

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!"

In the article "Signing certificates bypassing the certification authority " I described how an attacker with administrative rights on the certification authority can generate a logon certificate for administrative accounts of the domain by bypassing the certification authority software, i.e. by directly using the private key of the certification authority.

In the previous article I used the PSCertificateEnrollment Powershell Module to demonstrate the procedure. However, with certreq and certutil Microsoft already ships perfectly suitable pentesting tools directly with the operating system ex works.

Continue reading "Signing certificates bypassing the certification authority - solely using built-in tools"

Time and again in discussions about the security of a certification authority, it comes up that abuse of the certification authority could be contained by its security settings.

However, the fact that the integrity of a certification authority is directly tied to its key material and can therefore also be compromised through it is not obvious at first glance.

One has to think of the certification authority software as a kind of management around the key material. For example, the software provides an online interface for certificate enrollment , takes care of the authentication of the enrollees, the automated execution of signature operations (issuing certificates and certificate revocation lists ) and their logging (certification authority database , audit log , event log ).

However, signature operations require nothing more than the private key of the certification authority. The following example shows how an attacker, given access to the certification authority's private key, can generate and issue certificates without the certification authority software and its security mechanisms noticing.

With such a certificate, it would in the worst case even be possible to take over the Active Directory forest undetected .

Continue reading "Signing certificates bypassing the certification authority"

Even with a certificate template for domain controllers that is supposedly simple to configure, there are a few things to keep in mind.

Continue reading "Configuring a Certificate Template for Domain Controllers"

In simple terms, public key cryptography can be reduced to the assumption that the private part of each key pair is known only to its owner.

A certification authority is responsible for the correct identification of users, computers or resources. Its issued certificates are therefore granted a trust status because all participants assume that its private key is known only to it.

If an attacker succeeds in gaining knowledge of a certification authority's private key, or at least to perform signatures using the private key , the integrity of the certification authority is no longer guaranteed.

Continue reading "Attack vector on Active Directory directory service via smart card logon mechanism"