The release of Fedora 38 proposes to implement the first phase of the transition to a modernized boot process, previously suggested by Lennart Poettering, aiming for a fully verified boot covering all stages from firmware to user space, not just the kernel and bootloader. This proposal has not yet been reviewed by the FESCo (Fedora Engineering Steering Committee), which is responsible for the technical aspects of Fedora's development.
Components for implementing the proposed idea are already integrated into systemd 252 and involve using a unified kernel image (UKI), generated in the distribution's infrastructure and verified by the distribution's digital signature, instead of an initrd image created on the local system during kernel package installation. UKI combines the kernel loader for UEFI (UEFI boot stub), the Linux kernel image, and the initrd system environment loaded into memory into a single file. When invoking the UKI image from UEFI, integrity and authenticity checks can be performed using the digital signature not only for the kernel but also for the initrd contents, which is crucial as key extraction for decrypting the root filesystem occurs in this environment.
Due to the significant upcoming changes, the implementation is planned to be divided into several phases. The first phase will add UKI support to the bootloader and begin publishing an optional UKI image, focused on booting. of virtual machines with a limited set of components and drivers, as well as related tools for installing and updating UKI. In the second and third phases, it is planned to move away from passing kernel parameters via command line and cease storing keys in initrd.
Source: opennet.ru
