Re: [PATCH 2 of 4] ima: related Makefile compile order change and Readme

[Pavel Machek <pavel@ucw.cz>]

Hi!

> > > +Limitations: IMA does not detect corruption of software once it is
> > > +loaded into main memory. Instead, it indicates known vulnerabilities
> > > +in such software (e.g., buffer overflow) by securely identifying the
> > > +software at load-time. Only executable files (binaries, libraries,
> > > +kernel modules) are measured by default. However, IMA offers a
> > > +sysfs-interface that allows applications to instruct the kernel to
> > > +measure files that they have opened.
> > 
> > What is it good for, then? So I have to put my backdoor into script,
> > not into an executable...
> 
> Scripts can be measured as well (from the user space).
>  
> For example, equipping the bash shell with 5-10 lines of code, bash 
> initiates IMA measurements on scripts and files that are sourced into bash before 
> they are "executed" by bash. This way, startup scripts and executed scripts can 
> be logged as measurements and the measuremnt list will include
> them. 

Well, for this to be usefull, you'd have to split files into two
categories:

1) files that do not change

2) files that can not compromise your security.

I guess that /etc/shadow *has to change*, and it still can compromise
your system security.

Same with basch scripts; you can make bash checksum its script, but
when user modifies his first script, you'll detect system as
"compromised".

I guess it can work... but I don't see how it can work in Linux.

								Pavel
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