BMCs can be used to remotely monitor system temperature, voltage and power consumption, operating system health, and so on, and power cycle the box if it runs into trouble, tweak configurations, and even, depending on the setup, reinstall the OS – all from the comfort of an operations center, as opposed to having to find an errant server in the middle of a data center to physically wrangle. They also provide the foundations for IPMI.

[…]

It’s a situation not unlike Intel’s Active Management Technology, a remote management component that sits under the OS or hypervisor, has total control over a system, and been exploited more than once over the years.

Waisman and his colleague Matias Soler, a senior security researcher at Immunity, examined these BMC systems, and claimed the results weren’t good. They even tried some old-school hacking techniques from the 1990s against the equipment they could get hold of, and found them to be very successful. With HP’s BMC-based remote management technology iLO4, for example, the builtin web server could be tricked into thinking a remote attacker was local, and so didn’t need to authenticate them.

“We decided to take a look at these devices and what we found was even worse than what we could have imagined,” the pair said. “Vulnerabilities that bring back memories from the 1990s, remote code execution that is 100 per cent reliable, and the possibility of moving bidirectionally between the server and the BMC, making not only an amazing lateral movement angle, but the perfect backdoor too.”

The fear is that once an intruder gets into a data center network, insecure BMC firmware could be used to turn a drama into a crisis: vulnerabilities in the technology could be exploited to hijack more systems, install malware that persists across reboots and reinstalls, or simple hide from administrators.

[…]

The duo probed whatever kit they could get hold of – mainly older equipment – and it could be that modern stuff is a lot better in terms of security with firmware that follows secure coding best practices. On the other hand, what Waisman and Soler have found and documented doesn’t inspire a terrible amount of confidence in newer gear.

Their full findings can be found here, and their slides here.

Source: Can we talk about the little backdoors in data center servers, please? • The Register