Messages in this thread | | | Date | Thu, 24 Oct 2002 13:11:26 +0300 | From | Ville Herva <> | Subject | Re: One for the Security Guru's |
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On Wed, Oct 23, 2002 at 11:15:14PM +0100, you [James Stevenson] wrote: > > As to load a module you must be root and if you are root you > can read / write disks. Thus you could recompile your own kernel > install it try to force a crash or a reboot which is not hard as root > and the person may not even notice that the kernel has grown by a few > bytes after the crash.
Which is why some people configure kernels not to support installing modules and only use read-only media (e.g. CD-R) for booting. Sure, there's still the /dev/kmem hole, but this closes 2 classes of attacks - loading rootkit module and booting with a hacked kernel in straight-forward way.
BTW, this might be a reason to make kexec syscall to be a config option (if it isn't already.) The other reason is to avoid bloat for people that don't need it, but perhaps this is a stronger argument. I realize you can propably launch the kernel by hand (using /dev/kmem etc) if you really know what to do. But the same applies to adding code/patching kernel without CONFIG_MODULES support.
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