UEFI Secure Boot is not an attempt by Microsoft to lock Linux out of the PC market here SB is a security measure to protect against malware during early system boot. Starting with Debian version 10 ("Buster"), Debian included working UEFI Secure Boot to make things easier. The methods for doing this vary massively from one system to another, making this potentially quite difficult for users. This meant that on many new computer systems, users had to first disable SB to be able to install and use Debian. Other Linux distros (Red Hat, Fedora, SUSE, Ubuntu, etc.) have had SB working for a while, but Debian was slow in getting this working. There are also programs to deal with firmware updates before operating system startup (like fwupdate and fwupd), and other utilities may live here too. Most of the programs that are expected to run in the UEFI environment are boot loaders, but others exist too. Most modern systems will ship with SB enabled - they will not run any unsigned code by default, but it is possible to change the firmware configuration to either disable SB or to enroll extra signing keys. This means the firmware on these systems will trust binaries that are signed by Microsoft. Most x86 hardware comes from the factory pre-loaded with Microsoft keys. This stops unexpected / unauthorised code from running in the UEFI environment. When SB is enabled on a system, any attempt to execute an untrusted program will not be allowed. Each program that is loaded by the firmware includes a signature and a checksum, and before allowing execution the firmware will verify that the program is trusted by validating the checksum and the signature. SB works using cryptographic checksums and signatures. It is designed to protect a system against malicious code being loaded and executed early in the boot process, before the operating system has been loaded. UEFI Secure Boot (SB) is a verification mechanism for ensuring that code launched by a computer's UEFI firmware is trusted.
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May 2023
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