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The Intelligent Platform Management Interface (IPMI) specification defines a set of common interfaces to a computer system which system administrators can use to monitor system health IPMI and manage the system.
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Dell, HP, Intel Corporation and NEC Corporation announced IPMI v1.0 on 1998-09-16, v1.5 on 2001-03-01, and v2.0 on 2004-02-14. New in IPMI V2.0
IPMI is implemented on a hardware chip known as the Baseboard Management Controller (BMC), or Management Controller (MC). BMC operates independently of the operating system and allows administrators to manage a system remotely even in the absence of an operating system, or if the monitored system is powered off, but connected to a power source.
IPMI also functions after the operating system has started, and offers enhanced features when used with system management software.
IPMI version 1.5 and later can send out alerts via a direct serial connection, a local area network (LAN) or a serial over LAN (SOL) connection to a remote client. System administrators can then use IPMI messaging to query platform status, to review hardware logs, or to issue other requests from a remote console through the same connections.
The standard also defines an alerting mechanism for the system to send a simple network management protocol (SNMP) platform event trap (PET). Among them temperature, voltage, fan speed, bus errors, etc. It can perform recovery operations (local or remote system resets and power on/off operations), and an interface for logging without operating system intervention for abnormal or ‘out-of-range’ conditions for later examination and alerting.
BMC is always powered on even when the main system is OFF, or the operating system has crashed. So the BMC can be configured to look at the status of local hardware from another server for secure remote monitoring and recovery (such as system reset) regardless of the status of the platform.
Along with main controller BMC (Baseboard Management Controller ) there can be other management controllers distributed among different system modules that are referred to as "satellite" controllers. Such satellite controllers can implement Web interface like Dell DRAC as well as additional functions. For example remote CDROM drive.
The satellite controllers within the same chassis connect to the BMC via the system interface called IPMB (Intelligent Platform Management Bus/Bridge) — an enhanced implementation of I˛C (Inter-Integrated Circuit). The BMC connects to satellite controllers or another BMC in another chassis via IPMC (Intelligent Platform Management Chassis) bus/bridge. It may be managed with the Remote Management Control Protocol (RMCP), a specialized wire protocol defined by this specification.
A Field Replaceable Unit (FRU) holds the inventory (such as vendor id, manufacturer etc.) of potentially replaceable devices.
A Sensor Data Records (SDR) repository provides the properties of the individual sensors present on the board. For example, the board may contain sensors for temperature, fan speed, and voltage.
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Nov 07, 2017 | www.zdnet.com
Matthew Garrett, the well-known Linux and security developer who works for Google, explained recently that, "Intel chipsets for some years have included a Management Engine [ME] , a small microprocessor that runs independently of the main CPU and operating system. Various pieces of software run on the ME, ranging from code to handle media DRM to an implementation of a TPM. AMT [Active Management Technology] is another piece of software running on the ME."In May, we found out that AMT had a major security flaw , which had been in there for nine -- count 'em -- nine years.
"Fixing this requires a system firmware update in order to provide new ME firmware (including an updated copy of the AMT code)," Garrett wrote. "Many of the affected machines are no longer receiving firmware updates from their manufacturers, and so will probably never get a fix," he said. "Anyone who ever enables AMT on one of these devices will be vulnerable."
Quick! How many of you patched your PC or server's chip firmware? Right. Darn few of you. That's bad. It's not every processor, but if you or your hardware vendor has "explicitly enabled AMT", your machine is still vulnerable to attack.
The Electronic Frontier Foundation (EFF) has called for Intel to provide a way for users to disable ME . Russian researchers have found a way to disable ME after the hardware has initialized, and the main processor has started. That doesn't really help much. ME is already running by then.
But Minnich found that what's going on within the chip is even more troubling. At a presentation at Embedded Linux Conference Europe , he reported that systems using Intel chips that have AMT, are running MINIX.
If you learned about operating systems in the late '80s and early '90s, you knew MINIX as Andrew S Tanenbaum's educational Unix-like operating system. It was used to teach operating system principles. Today, it's best known as the OS that inspired Linus Torvalds to create Linux.
So, what's it doing in Intel chips? A lot. These processors are running a closed-source variation of the open-source MINIX 3. We don't know exactly what version or how it's been modified since we don't have the source code. We do know that with it there:
- Neither Linux nor any other operating system have final control of the x86 platform
- Between the operating system and the hardware are at least 2 ½ OS kernels (MINIX and UEFI)
- These are proprietary and (perhaps not surprisingly) exploit-friendly
- And the exploits can persist, i.e. be written to FLASH, and you can't fix that
In addition, thanks to Minnich and his fellow researchers' work, MINIX is running on three separate x86 cores on modern chips. There, it's running:
- TCP/IP networking stacks (4 and 6)
- File systems
- Drivers (disk, net, USB, mouse)
- Web servers
MINIX also has access to your passwords. It can also reimage your computer's firmware even if it's powered off. Let me repeat that. If your computer is "off" but still plugged in, MINIX can still potentially change your computer's fundamental settings.
And, for even more fun, it "can implement self-modifying code that can persist across power cycles". So, if an exploit happens here, even if you unplug your server in one last desperate attempt to save it, the attack will still be there waiting for you when you plug it back in.
How? MINIX can do all this because it runs at a fundamentally lower level.
x86-based computers run their software at different privilege levels or "rings" . Your programs run at ring three, and they have the least access to the hardware. The lower the number your program runs at, the more access they have to the hardware. Rings two and one don't tend to be used . Operating systems run on ring zero. Bare-metal hypervisors, such as Xen , run on ring -1. Unified Extensible Firmware Interface (UEFI) runs on ring -2. MINIX? It runs on ring -3.
You can't see it. You can't control it. It's just humming away there, running your computer. The result, according to Minnich is "there are big giant holes that people can drive exploits through." He continued, "Are you scared yet? If you're not scared yet, maybe I didn't explain it very well, because I sure am scared."
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