TCPA Support in Linux

kempokaraterulz writes "Linux Journal is reporting that "The Trusted Computing Platform Alliance has published open specifications for a security chip and related software interfaces.". In the latest Gentoo Newsletter they talk about a possible 'Trusted Gentoo', and possible uses for hardware level security."

Comments

Lacking One Thing

[SpottedKuh]

Though the specifications detailed in the article are definately a Good Thing, they lack (at least as far as I could tell) any way of preventing unauthorized physical access to the chip.

Physical access to machines is always a big issue in security, and one that is often overlooked. And while it's probably not a big deal for your home machine, consider large companies whose machines could conceivably be targetting for a physical attack to recover the keys directly from the TPM (Trusted Platform Module).

Stajano's "Ubiquitous Computing" book has excellent coverage of the rationale, issues, and complexity of attempting to prevent physical access to chips and devices which store sensitive information. It's an easy read, and well worth it: http://www-lce.eng.cam.ac.uk/~fms27/secubicomp/ind ex.html

Re:Here comes the flood??

[Greger47]

This is the thing that I don't get. The supposedly secure boot process seems to be broken from start to finish.

The "trusted" boot functions provide the ability to store in Platform Configuration Registers (PCR), hashes of configuration information throughout the boot sequence. Once booted, data (such as symmetric keys for encrypted files) can be "sealed" under a PCR. The sealed data can only be unsealed if the PCR has the same value as at the time of sealing. Thus, if an attempt is made to boot an alternative system, or a virus has backdoored the operating system, the PCR value will not match, and the unseal will fail, thus protecting the data.

The whitepaper also mentions that in IBMs implementation the chip is connected to the SMbus.

This means that the entire security of the boot process hangs on whatever data the CPU feels like sending to the chip for hashing. I could as well make a patch for GRUB that sends the "secure" version of GRUB down the SMbus and actually executes whatever nastiness I have in store.

In the case of DRM this lets me run whatever OS I want. The only thing I have to do is to feed a copy of whatever OS Hollywood trusts to the chip and voila the chip will say I'm legit and Hollywood will give me access to their movies for me to pirate at my leisure. :)

As I see it, the only way to get this to work for real is if Intel steps up and builds TCPA support into the CPU itself such that the PCR register is continuously updated as each instruction is executed. And all existing external chips have to be blacklisted, ofcourse.

Or does the TCPA system have some other trick up their sleeve that makes this work even though it's implemented externally to the CPU?

/greger