NIST Publishes Draft Guidelines For Server BIOS Protection

hypnosec writes "The U.S.'s National Institute of Standards and Technology has come up with a set of proposed guidelines for security of server BIOSes— the mechanism on which most modern day computers rely during boot up. Recently quite a few instances of malware have been known to persistently infect computer systems, and cannot be removed even on OS re-installs. NIST is proposing a set of measures through which the BIOS can be made more secure and resistant to such firmware manipulating attacks. Mebromi is one such Trojan. NIST published the draft guidelines [PDF] earlier this week and has proposed four different features through which the server BIOSes can be made more secure: authenticated update mechanism; secure local update mechanism (optional); firmware integrity protections; and non-bypassability features."

Comments

Stupid and wrong

[jmorris42]

Locking the BIOS with signed updates and crap is exactly the wrong way to go. It means there will still be bugs to exploit. But the forces seeking to lock down the PC will advance yet another step under cover of security theater.

The correct solution is to give the machine a one way gate so that after POST the BIOS can't be updated, period. Electrically impossible. That would require an updater in the BIOS and either storing the extended config now flashed into the same chip with the BIOS to either go elsewhere or the flash chip to be smart enough to have a protected area and an unprotected area and only the protected area be unrevokable without a full reboot. It also should go without saying that the BIOS can't look at the unprotected area before the big switch to prevent buffer overflow attacks from getting into the BIOS while the flash is writable and/or stopping the user from invoking a clear extended data function.

A minimal rescue program in mask ROM would be gravy of course. Lets see the leet warez doodz get past that one. Wouldn't put anything past the NSA though.

Re:Stupid and wrong

[dgatwood]

Actually, it's not easy. A trojan horse can draw the same UI, write the same file to the flash drive, and a naïve user would probably dutifully follow the instructions because the user would not know any better. Your "solution" is no better than the status quo.

Allowing a power-user (someone who knows how to hold down the magic keys and isn't afraid of the BIOS UI) to install an unsigned update explicitly and manually is one thing. Such a user can be assumed to know enough about what he or she is doing to understand the risks of downloading a BIOS update from an untrusted source. Allowing unsigned BIOS updates to be installed by average users as a part of their normal day-to-day update process, however, is another thing entirely, and is a very bad idea.

Re:Stupid and wrong

[msauve]

That would require an updater in the BIOS and either storing the extended config now flashed into the same chip with the BIOS to either go elsewhere or the flash chip to be smart enough to have a protected area and an unprotected area and only the protected area be unrevokable without a full reboot.

Let me change that from something completely unparsable, to something simple.

All that's needed is a jumper on the motherboard which must be closed in order to modify the BIOS.

Re:Stupid and wrong

[dgatwood]

I suppose updating your BIOS is not extremely common in the Windows world, though I've done more than one BIOS update over the years despite having used only a single-digit number of devices that actually have a BIOS, so it isn't that rare. And I would agree that updating the BIOS on server hardware is particularly exceptional.

The problem is that whatever standard somebody comes up with for servers is liable to trickle down into consumer goods. We'd be better off deciding on a single set of good, sane standards that everyone can live with, including consumer product makers. Coming from the Mac world, where nearly every piece of hardware has seen at least one EFI or SMC update, making it "almost impossible" seems like a very bad idea for general-purpose hardware.

Re:Stupid and wrong

[fustakrakich]

Yeah, my first thought was, if you want protected BIOS, I suggest it be read only, put it in a socket, and if needs an update, you have one shipped, or go to your local store and get one. Damned if the socket won't be bigger than the whole machine pretty soon...

Re:Stupid and wrong

[crispytwo]

Along the same logic, I would argue, why do we need to have the bios have built in writable flash memory these days? So many simple options to solve this come to mind, but if I really wanted to update the bois - which is incredibly rare - couldn't we be a little more hands on and use a USB key for example?
here's a possible solution:
- I could pull out a small USB drive/key from the special slot on the mobo
- stick it into my USB slot on a running computer
- write a new bios to it with my fancy updater tool - simple so far
- stick it back into the mobo (it could even lock in with a clip for those who vibrate a lot)
- (re)boot
- new bios is read from the -special- USB.

bonuses:
- if something goes wrong - place in a new different USB drive/key
- test with a different USB drive/key to see if the update is better, then update the special one
- I can think of others too!

what I mean by "special USB", is that it is only accessed and read by a booting bios, so doesn't have pass through or presence to the OS. It may be especially small.

I seem to remember somewhere that we don't really need much of a BIOS since the kernels do all the probing for themselves a second time anyway, so in many respects we have 2 boots, once (slowly) in BIOS, which is promptly thrown away, and another in whatever OS you might load.

Re:Stupid and wrong

[SuricouRaven]

Secure boot works using a cryptographic signing system: The board will only boot code signed by one of the Powers That Be - an organisation big enough for motherboard vendors to bother including the public key for, like Microsoft. This places smaller, niche players at a serious disadvantage. Which is probably the idea. An alternative non-market-distorting approach would be fingerprinting: The BIOS/EFI hashes the MBR (plus however many additional sectors the MBR specifies in an agreed-upon location). If the result doesn't match a stored fingerprint, it can generate a warning and refuse to boot until the user either restores from a matching backup or else selects the 'I intentionally changed the OS' button - in which case the newly-computed hash replaces the stored one.

If Secure Boot were really about security, that is how it would work. But it isn't. It's about creating a barrier in the market which can only be overcome with a pile of cash or good business connections, something that poses only the slightest inconvenience to Microsoft but a major difficulty to linux.

Step one?

[girlintraining]

Step one: Kill UEFI with fire.
Step two (optional): Everything else.

I'm perfectly serious -- If you have UEFI, it doesn't matter how secure everything else is, you're screwed, and you're screwed because Microsoft asked the companies making the motherboards to screw you for the sake of adding yet another failed DRM attempt to their next operating system: Windows 8, "Explode On Launchpad Edition".

Re:Step one?

[Microlith]

UEFI is not the problem.

The problem is that the security architecture that was added to UEFI was designed by Microsoft and (obviously) favors them completely. Unfortunately, they're the only OS level software developer in the UEFI Promoters group so they pretty much get whatever they want and, I suspect, can overrule complaints from "Contributors."

A real fair solution would have had such keys administered by the UEFI Foundation and included the ability to auto-add keys from read-only media.

Re:Step one?

[Aryeh Goretsky]

Hello,

A list of OS software developers who are members of UEFI:

• Apple
• Canonical
• Cisco
• Cray
• Fujitsu
• Hewlett-Packard
• IBM
• Microsoft
• NEC
• Novell
• Oracle
• Red Flag
• Red Hat

And there are also other companies who work in the same neighborhood (CPU manufacturers, firmware developers, etc.). Source: UEFI Membership List.

While I understand (and, to some extent, sympathize with) the desire to hold Microsoft solely responsible for every activity in the computing industry, this is clearly a joint effort across the industry to replace a two decade-old invention whose time has come. And as far as I know, the largest installed base of UEFI firmware—albeit an older version of the standard—is Apple, a company not precisely known for having a cordial relationship with Microsoft.

Regards,

Aryeh Goretsky

Easier

[Weaselmancer]

You should only update your BIOS when you mean to. I'm of the opinion that it's something that you should mean to do, not something that should just happen automatically ever. So it doesn't need to be writable 99.999% of the time. So how about a switch that toggles the write enable pin to your bios flash on the front panel of your box?

Want to update your bios? Power down box. Insert CD or USB key. Flip write enable switch. Power up. Flash bios then power down. Flip switch to write disable. Boot.

And for an added measure, don't let the thing ever boot from an MBR if the switch is in "write" mode.

Easy peasy.