# Information in Printers

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There are several blogs in the Internet which **highlight the dangers of leaving printers configured with LDAP with default/weak** logon credentials.  \
This is because an attacker could **trick the printer to authenticate against a rogue LDAP server** (typically a `nc -vv -l -p 389` or `slapd -d 2` is enough) and capture the printer **credentials in clear-text**.

Also, several printers will contain **logs with usernames** or could even be able to **download all usernames** from the Domain Controller.

All this **sensitive information** and the common **lack of security** makes printers very interesting for attackers.

Some introductory blogs about the topic:

- [https://www.ceos3c.com/hacking/obtaining-domain-credentials-printer-netcat/](https://www.ceos3c.com/hacking/obtaining-domain-credentials-printer-netcat/)
- [https://medium.com/@nickvangilder/exploiting-multifunction-printers-during-a-penetration-test-engagement-28d3840d8856](https://medium.com/@nickvangilder/exploiting-multifunction-printers-during-a-penetration-test-engagement-28d3840d8856)

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## Printer Configuration

- **Location**: The LDAP server list is usually found in the web interface (e.g. *Network ➜ LDAP Setting ➜ Setting Up LDAP*).
- **Behavior**: Many embedded web servers allow LDAP server modifications **without re-entering credentials** (usability feature → security risk).
- **Exploit**: Redirect the LDAP server address to an attacker-controlled host and use the *Test Connection* / *Address Book Sync* button to force the printer to bind to you.

---
## Capturing Credentials

### Method 1 – Netcat Listener

```bash
sudo nc -k -v -l -p 389     # LDAPS → 636 (or 3269)
```

Small/old MFPs may send a simple *simple-bind* in clear-text that netcat can capture. Modern devices usually perform an anonymous query first and then attempt the bind, so results vary.

### Method 2 – Full Rogue LDAP server (recommended)

Because many devices will issue an anonymous search *before* authenticating, standing up a real LDAP daemon yields much more reliable results:

```bash
# Debian/Ubuntu example
sudo apt install slapd ldap-utils
sudo dpkg-reconfigure slapd   # set any base-DN – it will not be validated

# run slapd in foreground / debug 2
slapd -d 2 -h "ldap:///"      # only LDAP, no LDAPS
```

When the printer performs its lookup you will see the clear-text credentials in the debug output.

> 💡  You can also use `impacket/examples/ldapd.py` (Python rogue LDAP) or `Responder -w -r -f` to harvest NTLMv2 hashes over LDAP/SMB.

---
## Recent Pass-Back Vulnerabilities (2024-2025)

Pass-back is *not* a theoretical issue – vendors keep publishing advisories in 2024/2025 that exactly describe this attack class.

### Xerox VersaLink – CVE-2024-12510 & CVE-2024-12511

Firmware ≤ 57.69.91 of Xerox VersaLink C70xx MFPs allowed an authenticated admin (or anyone when default creds remain) to:

* **CVE-2024-12510 – LDAP pass-back**: change the LDAP server address and trigger a lookup, causing the device to leak the configured Windows credentials to the attacker-controlled host.
* **CVE-2024-12511 – SMB/FTP pass-back**: identical issue via *scan-to-folder* destinations, leaking NetNTLMv2 or FTP clear-text creds.

A simple listener such as:

```bash
sudo nc -k -v -l -p 389     # capture LDAP bind
```

or a rogue SMB server (`impacket-smbserver`) is enough to harvest the credentials.  

### Canon imageRUNNER / imageCLASS – Advisory 20 May 2025

Canon confirmed a **SMTP/LDAP pass-back** weakness in dozens of Laser & MFP product lines. An attacker with admin access can modify the server configuration and retrieve the stored credentials for LDAP **or** SMTP (many orgs use a privileged account to allow scan-to-mail).  

The vendor guidance explicitly recommends:

1. Updating to patched firmware as soon as available.
2. Using strong, unique admin passwords.
3. Avoiding privileged AD accounts for printer integration.

---
## Automated Enumeration / Exploitation Tools

| Tool | Purpose | Example |
|------|---------|---------|
| **PRET** (Printer Exploitation Toolkit) | PostScript/PJL/PCL abuse, file-system access, default-creds check, *SNMP discovery* | `python pret.py 192.168.1.50 pjl` |
| **Praeda** | Harvest configuration (including address books & LDAP creds) via HTTP/HTTPS | `perl praeda.pl -t 192.168.1.50` |
| **Responder / ntlmrelayx** | Capture & relay NetNTLM hashes from SMB/FTP pass-back | `responder -I eth0 -wrf` |
| **impacket-ldapd.py** | Lightweight rogue LDAP service to receive clear-text binds | `python ldapd.py -debug` |

---
## Hardening & Detection

1. **Patch / firmware-update** MFPs promptly (check vendor PSIRT bulletins).
2. **Least-Privilege Service Accounts** – never use Domain Admin for LDAP/SMB/SMTP; restrict to *read-only* OU scopes.
3. **Restrict Management Access** – place printer web/IPP/SNMP interfaces in a management VLAN or behind an ACL/VPN.
4. **Disable Unused Protocols** – FTP, Telnet, raw-9100, older SSL ciphers.
5. **Enable Audit Logging** – some devices can syslog LDAP/SMTP failures; correlate unexpected binds.
6. **Monitor for Clear-Text LDAP binds** on unusual sources (printers should normally talk only to DCs).
7. **SNMPv3 or disable SNMP** – community `public` often leaks device & LDAP config.

---
## References

- [https://grimhacker.com/2018/03/09/just-a-printer/](https://grimhacker.com/2018/03/09/just-a-printer/)
- Rapid7. “Xerox VersaLink C7025 MFP Pass-Back Attack Vulnerabilities.” February 2025.  
- Canon PSIRT. “Vulnerability Mitigation Against SMTP/LDAP Passback for Laser Printers and Small Office Multifunction Printers.” May 2025.

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