Whonix developer Patrick doesn't believe in file system permissions for containing malware having already infected a system and shares Joanna Rutkowska's opinion on that. The word "believe" in this context has been deliberately chosen, because putting permissions into questions might start a religiously heated discussion.
One interesting thing about Qubes DB is that it get rids of the (overly complex and unnecessary) permission system that is used by xenstore, and instead uses the most simple approach: each VM has its separate Qubes DB daemon, and so a totally separate configuration/state namespace. This is inline with the rest of the Qubes philosophy, which basically says that: permissions is dead, long live separation!
Many old-school security people can't imagine a system without permissions, but if we think about it more, we might get to a conclusion that: 1) permissions are complex and so often difficult to understand and set correctly, 2) require often complex code to parse and make security decisions, and 3) often are absolutely unneeded.
As a practical example of how permissions schemes might sometime trick even (otherwise somehow smart) developers into making a mistake consider this bug in Qubes we made a long time ago when setting permissions on some xenstore key, which resulted in some information leak (not much of a security problem in general, but still). And just today, Xen.org has published this advisory, that sounds pretty serious, again caused by bad permissions on some xenstore keys.
The real solution is using strong isolation concepts, as Qubes OS is doing.
Countless hours of Whonix development time were wasted on file permissions.
- How long would user password have to be so they cannot be locally brute forced and how realistic is it to have users keep on typing them?
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