Pass the ticket
MITRE ATT&CK™ Sub-technique T1550.003
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MITRE ATT&CK™ Sub-technique T1550.003
Last updated
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There are ways to come across () or forge (, and attacks) Kerberos tickets. A ticket can then be used to authenticate to a system using Kerberos without knowing any password. This is called . Another name for this is Pass the Cache (when using tickets from, or found on, UNIX-like systems).
On Windows systems, tools like and inject the ticket in memory. Native Microsoft tools can then use the ticket just like usual.
On UNIX-like systems, the path to the .ccache ticket to use has to be referenced in the environment variable KRB5CCNAME
Once a ticket is obtained/created, it needs to be referenced in the KRB5CCNAME environment variable for it to be used by others tools.
On Windows, once Kerberos tickets are injected, they can be used natively.
On UNIX-like systems, once the KRB5CCNAME variable is exported, the ticket can be used by tools that support Kerberos authentication.
When requesting access to a service, a Service Ticket is used. In contains enough information about the user to allow the destination service to decide to grant access or not, without asking the Domain Controller. These information are stored in a protected blob inside the ST called PAC (Privilege Attribute Certificate). In theory, the user requesting access can't tamper with that PAC.
Another information stored in the ST, outside of the PAC, and unprotected, called sname, indicates what service the ticket is destined to be used for. This information is basically the SPN (Service Principal Name) of the target service. It's split into two elements: the service class, and the hostname.
The scripts like (Python) have the ability to remotely dump hashes and LSA secrets from a machine.
(Python) has the ability to do it on a set of targets. The bh_owned has the ability to set targets as "owned" in (see ).
(Python) has the ability to do it with higher success probabilities as it offers multiple dumping methods. This tool can set targets as "owned" in . It works in standalone but also as a module (see ).
On Windows, once the ticket is injected, it will natively be used when accessing a service, for example with to extract the krbtgt hash.
Some scripts (Python) enable testers to execute commands on target systems with Kerberos support.
(Python) has the ability to do it on a set of targets
On Windows, legitimate tools like the () can then be used to open a cmd using that ticket.
Their are multiple service classes for multiple service types (LDAP, CIFS, HTTP and so on) (more info on ). The problem here is that since the SPN is not protected, there are scenarios (e.g. services configured for ) where the service class can be modified in the ticket, allowing attackers to have access to other types of services.
This technique is implemented and attempted by default in all scripts when doing pass-the-ticket (Impacket tries to change the service class to something else, and calls this "AnySPN").
Impacket's tgssub.py script can also be used for manual manipulation of the service name value. At the time of writing, 12th Feb. 2022, adding this script is pending.
With , it can be conducted by supplying the /altservice flag when using the s4u or the tgssub modules and the whole SPN can be changed (service class and/or hostname).
