On 23/09/2020 22:51, Pavel Machek wrote: > Hi! > >>>> Scenario 2 >>>> ---------- >>>> >>>> We know what code we need in advance. User trampolines are a good example of >>>> this. It is possible to define such code statically with some help from the >>>> kernel. >>>> >>>> This RFC addresses (2). (1) needs a general purpose trusted code generator >>>> and is out of scope for this RFC. >>> >>> This is slightly less crazy talk than introduction talking about holes >>> in W^X. But it is very, very far from normal Unix system, where you >>> have selection of interpretters to run your malware on (sh, python, >>> awk, emacs, ...) and often you can even compile malware from sources. >>> >>> And as you noted, we don't have "a general purpose trusted code >>> generator" for our systems. >>> >>> I believe you should simply delete confusing "introduction" and >>> provide details of super-secure system where your patches would be >>> useful, instead. >> >> This RFC talks about converting dynamic code (which cannot be authenticated) >> to static code that can be authenticated using signature verification. That >> is the scope of this RFC. >> >> If I have not been clear before, by dynamic code, I mean machine code that is >> dynamic in nature. Scripts are beyond the scope of this RFC. >> >> Also, malware compiled from sources is not dynamic code. That is orthogonal >> to this RFC. If such malware has a valid signature that the kernel permits its >> execution, we have a systemic problem. >> >> I am not saying that script authentication or compiled malware are not problems. >> I am just saying that this RFC is not trying to solve all of the security problems. >> It is trying to define one way to convert dynamic code to static code to address >> one class of problems. > > Well, you don't have to solve all problems at once. > > But solutions have to exist, and AFAIK in this case they don't. You > are armoring doors, but ignoring open windows. FYI, script execution is being addressed (for the kernel part) by this patch series: https://lore.kernel.org/lkml/20200924153228.387737-1-mic@xxxxxxxxxxx/ > > Or very probably you are thinking about something different than > normal desktop distros (Debian 10). Because on my systems, I have > python, gdb and gcc... It doesn't make sense for a tailored security system to leave all these tools available to an attacker. > > It would be nice to specify what other pieces need to be present for > this to make sense -- because it makes no sense on Debian 10. Not all kernel features make sense for a generic/undefined usage, especially specific security mechanisms (e.g. SELinux, Smack, Tomoyo, SafeSetID, LoadPin, IMA, IPE, secure/trusted boot, lockdown, etc.), but they can still be definitely useful. > > Best regards, > Pavel >
