Comment on Microsoft waited 6 months to patch actively exploited admin-to-kernel vulnerability
henfredemars@infosec.pub 3 months agoYou generally cannot load whatever you want into the kernel as admin on Windows.
You have to either disable secure boot to enable changing it via command prompt, or you have to boot into a special recovery mode first that verifies you have physical access to turn it off.
Linux with secure boot is similar. Root cannot patch the kernel (without a bug). The kernel lockdown feature is activated, which enforces code signing. You have to use your physical access to change the UEFI setting to disable secure boot first or use a MOK to enable signing your own modules in such a way the secure boot chain accepts them.
hddsx@lemmy.ca 3 months ago
Huh. I must be outdated. I didn’t know they got secure boot working. So what do you do when you need to update your kernel? Or does the fact that it comes from the package manager mean that it is allowed to update that?
henfredemars@infosec.pub 3 months ago
The package manager doesn’t have special permission. The new kernel you download is also signed for you and trusted by your system.
If it wasn’t trusted, would the next time you boot the kernel won’t load because the bootloader will refuse to load the unsigned code.
technohacker@programming.dev 3 months ago
Generally yes. For many distros, the kernel signing key is with the distro maintainers and so the package comes with pre-signed kernel images. For distros like Arch and Gentoo, it’s the user’s responsibility to maintain the signing key and sign each updated kernel
hddsx@lemmy.ca 3 months ago
So why can’t root add new keys?
technohacker@programming.dev 3 months ago
The firmware has to allow it, so if you’ve got physical access to the machine that’s possible. Remote access root, on the other hand, can’t tell the firmware to register new keys as long as it’s configured correctly