No, because the entire point of this is to be resilient against physical attack - anyone re-flashing your firmware already has your case open and can just move the jumper while they're at it.
A switch that can’t be controlled via software is at least more secure than the alternatives. If you check the jumper before booting up you can still be 100% sure even if someone previously flashed stuff onto it. Remember, it is called secure boot, not secure flash, so fw get verified again during boot up.
Not really. Secure Boot also guards access to tamper-resistant security modules like the TPM. Replacing the whole machine would never give you access to the old TPM. And if, for example, the disk is encrypted using using keys stored in the TPM, replacing the board won't work. Same even for OS-level keychains and credential stores even if the entire disk isn't encrypted.
if i have access to the tpm and the system, i can MitM it.
safeboot is perfect in a theoritical ideal vacum. something that bored reaearchers look and nod.
but keys leaking, hardware hacks, etc... are not even considered to not disturb the safety blanket everyone wrapped themselves with. yeah it makes it inconvenient for boot kits, bit that's it. if you can install os updates, i can install a boot kit
This is if you unlock your machine after an attacker has had physical access to it. "Evil maid" attacks are well-known (that is what these are called, someone installing MitM hardware on your computer). Whether contemporary machines are actually resistant to it in practice I am not sure.
So, isn't this firmware protection with BootGuard only really meant to prevent rootkits from getting persistence?
PS: thanks for all the blog posts you share on the matter! they are really golden
I saw this "but it only prevent persistence" several times and I wonder...
Isn't preventing rootkit from getting persistence already a big win? Preventing a rootkit from getting persistence also means that should a new signed kernel contain a security fix fixing the hole the rootkit was exploiting be installed, the rootkit won't work at all anymore. The attacker now needs not only to root the machine at each boot, he also needs to cross fingers that a kernel patch closing the hole he's exploiting doesn't get installed (or he needs to both prevent the new kernel from being installed while, at the same time, managing to make believe it's been installed).
Which also raises the probability the exploit he's using at every boot gets detected at some point.
How is this a win for attackers?
Are black hat hackers really thinking "Great, BootGuard and SecureBoot are getting ubiquitous, everything up to the kernel loading is signed and enforced, so now things are easier for me!"?