Disabling ptrace

[Konstantin Belousov]

On Tue, Dec 30, 2014 at 12:22:12PM -0800, Simon J. Gerraty wrote:
> Shawn Webb <lattera at gmail.com> wrote:
> > I'm curious what the use case was that brought this up. And why the requester 
> > thinks it's actually useful.
> 
> Being able to disable ptrace is useful - provided it cannot be bypassed.
> In Junos we leveraged the signed binary implementation (based on NetBSD's
> verified exec) to tag processes for which ptrace should fail.  The
> signed binary stuff also supposed to prevent games with LD_PRELOAD -
> assuming we didn't provide and sign the lib in question.
Look.  If somebody can preload a library into the process, or arbitrary
modify the text segment, circumventing ptrace(2) ban is a least worry.
The reference to the "Old New Thing" blog I posted before explains
that with with fireworks, based on real 'security reports' sent to the
security team at MS.

> 
> When we re-implemented veriexec as a MAC module, the above was left out,
> in anticipation of using a separate module (though perhaps still
> leveraging veriexec to set the labels).