IPMI
Last updated
Last updated
(IPMI) is a set of standardized specifications for hardware-based host management systems used for system management and monitoring. It acts as an autonomous subsystem and works independently of the host's BIOS, CPU, firmware, and underlying operating system. IPMI provides sysadmins with the ability to manage and monitor systems even if they are powered off or in an unresponsive state. It operates using a direct network connection to the system's hardware and does not require access to the operating system via a login shell. IPMI can also be used for remote upgrades to systems without requiring physical access to the target host. IPMI is typically used in three ways:
Before the OS has booted to modify BIOS settings
When the host is fully powered down
Access to a host after a system failure
When not being used for these tasks, IPMI can monitor a range of different things such as system temperature, voltage, fan status, and power supplies. It can also be used for querying inventory information, reviewing hardware logs, and alerting using SNMP. The host system can be powered off, but the IPMI module requires a power source and a LAN connection to work correctly.
The IPMI protocol was first published by Intel in 1998 and is now supported by over 200 system vendors, including Cisco, Dell, HP, Supermicro, Intel, and more. Systems using IPMI version 2.0 can be administered via serial over LAN, giving sysadmins the ability to view serial console output in band. To function, IPMI requires the following components:
Baseboard Management Controller (BMC) - A micro-controller and essential component of an IPMI
Intelligent Chassis Management Bus (ICMB) - An interface that permits communication from one chassis to another
Intelligent Platform Management Bus (IPMB) - extends the BMC
IPMI Memory - stores things such as the system event log, repository store data, and more
Communications Interfaces - local system interfaces, serial and LAN interfaces, ICMB and PCI Management Bus
IPMI communicates over port 623 UDP. Systems that use the IPMI protocol are called Baseboard Management Controllers (BMCs). BMCs are typically implemented as embedded ARM systems running Linux, and connected directly to the host's motherboard. BMCs are built into many motherboards but can also be added to a system as a PCI card. Most servers either come with a BMC or support adding a BMC. The most common BMCs we often see during internal penetration tests are HP iLO, Dell DRAC, and Supermicro IPMI. If we can access a BMC during an assessment, we would gain full access to the host motherboard and be able to monitor, reboot, power off, or even reinstall the host operating system. Gaining access to a BMC is nearly equivalent to physical access to a system. Many BMCs (including HP iLO, Dell DRAC, and Supermicro IPMI) expose a web-based management console, some sort of command-line remote access protocol such as Telnet or SSH, and the port 623 UDP, which, again, is for the IPMI network protocol. Below is a sample Nmap scan using the Nmap NSE script to footprint the service.
Nmap
We can use a specific Nmap script for IPMI version:
Script Summary:Performs IPMI Information Discovery through Channel Auth probes.
Example Usage:nmap -sU --script ipmi-version -p 623 <host>
During internal penetration tests, we often find BMCs where the administrators have not changed the default password. Some unique default passwords to keep in our cheatsheets include:
Dell iDRAC
root
calvin
HP iLO
Administrator
randomized 8-character string consisting of numbers and uppercase letters
Supermicro IPMI
ADMIN
ADMIN
It is also essential to try out known default passwords for ANY services that we discover, as these are often left unchanged and can lead to quick wins. When dealing with BMCs, these default passwords may gain us access to the web console or even command line access via SSH or Telnet.
There is no direct "fix" to this issue because the flaw is a critical component of the IPMI specification. Clients can opt for very long, difficult to crack passwords or implement network segmentation rules to restrict the direct access to the BMCs. It is important to not overlook IPMI during internal penetration tests (we see it during most assessments) because not only can we often gain access to the BMC web console, which is a high-risk finding, but we have seen environments where a unique (but crackable) password is set that is later re-used across other systems. On one such penetration test, we obtained an IPMI hash, cracked it offline using Hashcat, and were able to SSH into many critical servers in the environment as the root user and gain access to web management consoles for various network monitoring tools.
Here we can see that we have successfully obtained the password hash for the user ADMIN, and the tool was able to quickly crack it to reveal what appears to be a default password ADMIN. From here, we could attempt to log in to the BMC, or, if the password were something more unique, check for password re-use on other systems. IPMI is very common in network environments since sysadmins need to be able to access servers remotely in the event of an outage or perform certain maintenance tasks that they would traditionally have had to be physically in front of the server to complete. This ease of administration comes with the risk of exposing password hashes to anyone on the network and can lead to unauthorized access, system disruption, and even remote code execution. Checking for IPMI should be part of our internal penetration test playbook for any environment we find ourselves assessing.
Here, we can see that the IPMI protocol is indeed listening on port 623, and Nmap has fingerprinted version 2.0 of the protocol. We can also use the Metasploit scanner module .
If default credentials do not work to access a BMC, we can turn to a in the RAKP protocol in IPMI 2.0. During the authentication process, the server sends a salted SHA1 or MD5 hash of the user's password to the client before authentication takes place. This can be leveraged to obtain the password hash for ANY valid user account on the BMC. These password hashes can then be cracked offline using a dictionary attack using Hashcat mode 7300. In the event of an HP iLO using a factory default password, we can use this Hashcat mask attack command hashcat -m 7300 ipmi.txt -a 3 ?1?1?1?1?1?1?1?1 -1 ?d?u which tries all combinations of upper case letters and numbers for an eight-character password.
To retrieve IPMI hashes, we can use the Metasploit module.