Messages in this thread | | | Date | Wed, 1 Oct 2003 22:04:11 -0400 (EDT) | From | David Gordon <> | Subject | Re: [ANNOUNCE] DigSig 0.2: kernel module for digital signatureverification for binaries |
| |
> The "How do I make sure that only licensed software > will run on my new gizmo?" problem? > > Why should an open source developer encourage this?
Digital signatures in open source software are aimed at running only allowed (read signed) binaries, the license question is a side issue. IMHO, this has a potential to increase the security of a Linux box.
> AFAICS if I want to exec something, I can avoid > exec() syscall and do mmaps by hand... > Pavel
That is true. A digital signature will only protect binary data on hard disk. The whole process from the hard disk to memory is harder to cover (see http://www.phrack.org/show.php?p=59&a=5 Short Stories about execve). I believe that digital signature verification in the kernel must be placed as close as possible to the actual mmap of the binary. LSM framework is the current way of implementing this but not quite sufficient.
> Don't be ridiculous. It's trivial to exploit a local > buffer overrun in one of your signed binaries and > have the shellcode mmap the rest. All pre-built, of
> course.
That's also true. A digital signature will not protect against an already existing vulnerability in a binary (bo). Let's say for instance that a linux box is compromised with a bo, usually another backdoor is created. Even if the system is running Pax (mentioned by Makan), "http://www.phrack.org/show.php?p=61&a=8 Cerberus Elf interface" describes how to circumvent this.
But on a system with digitally signed binaries, this is no longer possible since it requires modification of the binary which is signed.
My point is that a system with digitally signed binaries won't prevent existing security holes, but will prevent the creation of other ones. The attacker is constrained to use the system as is, ie. to exploit the same bo. Unless of course the bo gives him access to the kernel and he disables digital signature verification.
David
______________________________________________________________________ Post your free ad now! http://personals.yahoo.ca - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |