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Some more typos secureboot
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dngray committed Mar 20, 2022
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Expand Up @@ -300,9 +300,9 @@ For background of how Secure Boot works on Linux:
One of the problems with Secure Boot particularly on Linux is that only the [chainloader](https://en.wikipedia.org/wiki/Chain_loading#Chain_loading_in_boot_manager_programs) (shim), the [boot loader](https://en.wikipedia.org/wiki/Bootloader) (GRUB), and the [kernel](https://en.wikipedia.org/wiki/Kernel_(operating_system)) are verified and that's where verification stops. The [initramfs](https://en.wikipedia.org/wiki/Initial_ramdisk) is often left unverified, unencrypted, and open up the window for an [evil maid](https://en.wikipedia.org/wiki/Evil_maid_attack) attack. There are a few things that can be done to reduce risk such as:

* Creating an [EFI Boot Stub](https://docs.kernel.org/admin-guide/efi-stub.html) that contains the [kernel](https://en.wikipedia.org/wiki/Kernel_(operating_system)), [initramfs](https://en.wikipedia.org/wiki/Initial_ramdisk) and [microcode](https://en.wikipedia.org/wiki/Microcode). This EFI stub can then be signed. If you use [dracut](https://en.wikipedia.org/wiki/Dracut_(software)) this can easily be done with the [`--uefi-stub` switch](https://man7.org/linux/man-pages/man8/dracut.8.html) or the [`uefi_stub` config](https://www.man7.org/linux/man-pages/man5/dracut.conf.5.html) option.
* [Encrypting the boot partition](https://wiki.archlinux.org/title/GRUB#Encrypted_/boot). However, this has it's own issues, the first being that [GRUB](https://en.wikipedia.org/wiki/GNU_GRUB) only supports [LUKS1](https://en.wikipedia.org/wiki/Linux_Unified_Key_Setup) and not the newer default LUKS2 scheme. As the bootloader runs in [protected mode](https://en.wikipedia.org/wiki/Protected_mode) and the encryption module lacks [SSE acceleration](https://en.wikipedia.org/wiki/Streaming_SIMD_Extensions) the boot process will take minutes to complete.
* [Encrypting the boot partition](https://wiki.archlinux.org/title/GRUB#Encrypted_/boot). However, this has its own issues, the first being that [GRUB](https://en.wikipedia.org/wiki/GNU_GRUB) only supports [LUKS1](https://en.wikipedia.org/wiki/Linux_Unified_Key_Setup) and not the newer default LUKS2 scheme. As the bootloader runs in [protected mode](https://en.wikipedia.org/wiki/Protected_mode) and the encryption module lacks [SSE acceleration](https://en.wikipedia.org/wiki/Streaming_SIMD_Extensions) the boot process will take minutes to complete.
* Using [TPM](https://en.wikipedia.org/wiki/Trusted_Platform_Module) to perform a [measured boot](https://www.krose.org/~krose/measured_boot).

After setting up Secure Boot it is cruical that you set a "firmware password" (also called a "supervisor password, "BIOS password" or "UEFI password"), otherwise an adversary can simply disable secure boot.
After setting up Secure Boot it is crucial that you set a "firmware password" (also called a "supervisor password, "BIOS password" or "UEFI password"), otherwise an adversary can simply disable secure boot.

These recommendations can make you a little more resistant to [evil maid](https://en.wikipedia.org/wiki/Evil_maid_attack) attacks, they not good as a proper verified boot process such as that found on [Android](https://source.android.com/security/verifiedboot), [ChromeOS](https://support.google.com/chromebook/answer/3438631) or [Windows](https://docs.microsoft.com/en-us/windows/security/information-protection/secure-the-windows-10-boot-process).

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