OpenBSD: A new feature added to test snapshots of new OpenBSD releases will create a unique Kernel each time an OpenBSD user reboots or upgrades their computer.
This function is called KARL from the Kernel Address Randomized Link, or Random Kernel Address, and works by relinking the internal kernel files in random order to create a unique kernel binary blob every time.
Currently, in stable versions of OpenBSD the kernel uses a predefined order to perform relinking and load internal files into the kernel binary. This results in the same core for all of them users.
OpenBSD with KARL and not ASLR
KARL was developed by Theo de Raadt, and works by creating a new binary kernel during installation, upgrading, and boot time. If the user boots, upgrades or restarts his machine, a new created kernel will replace the existing kernel and the operating system will create a new binary kernel to be used in the next boot / upgrade / restart.
KARL should not be confused with ASLR or Address Space Layout Randomization, a technique that gives random addressing μνήμηs (memory address) when an application is running. Thus exploits cannot target a specific area of memory that the attacker knows an application or the kernel is running on.
Instead, KARL creates kernel binaries with random internal structures, so exploits can not attack internal kernel functions, pointers, or objects. A technical explanation is available in the link below.
http://undeadly.org/cgi?action=article&sid=20170701170044&mode=expanded&count=9
The feature has been developed lately two months
Tasks for this feature began in May and were first discussed in mid-June through the OpenBSD technical mailing list. KARL was recently added to OpenBSD 6.1 snapshots.
This new feature appears to be unique in OpenBSD, as we do not know anything similar about it Linux.
Linux has just added support for the Kernel Address Space Layout Randomization (KASLR), a function that makes the ASLR port in the kernel itself, loading the kernel to a random memory address.
This feature was enabled by default on Linux 4.12, which was released last week. The difference between the two is that KARL loads different kernel binaries in the same place, while KASLR loads the same kernel binary at random locations. Same goal, different paths.
As for Windows, KARL is not supported, but Microsoft has been using KASLR for many years.
It should be noted that OpenBSD's new functionality appears to provide much more security than the solutions used by Microsoft and Linux.
Perhaps after several tests we see KARL in other operating systems as well.
