On Thu, Nov 01, 2012 at 09:10:03AM -0400, Vivek Goyal wrote: [..] > > > > > - So say we can sign /sbin/kexec at build time and distros can do that. > > > - Verify the signature at exec time using kernel keyring and if > > > verification happens successfully, say process gains extra capability. > > > - Use this new capability to determine whether kexec_load() will be > > > successful or not. > > > > > > Even if we can do all this, it still has the issue of being able to > > > stop the process in user space and replace the code at run time > > > and be able to launch unsigned kernel. > > Thinking more about it. Can we just keep track whether a process was > ptraced or not and disallow kexec_load() syscall if it was ptraced. > (I am assuming that ptrace is the only way to change process code/data). > > So binaries can be signed offline. Signature verification can take place > using kernel keyring at exec() time. And we can keep track of ptraced > processes and disallow calling kexec_load() for such processes. If this > is implementable, this should take care of following requirement raised > by matthew. > > ************************************************************************ > It must be impossible for the kernel to launch any /sbin/kexec that hasn't > been signed by a trusted key that's been built into the kernel, and it > must be impossible for anything other than /sbin/kexec to make the kexec > system call. > ************************************************************************* > > Thoughts? Eric responded but my mistake he responded to only me. So I will quickly put his idea here. [start quote] You can't ptrace a process that has a capability you don't. That should be enforced in security/commoncap/ [end quote] This looks like a good idea. Upon verification signed binaries will be assigned special capability and then no unsigned binary should be able to ptrace signed/verified processes Thanks Vivek
