lkml.org 
[lkml]   [2012]   [Jan]   [12]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [RFC,PATCH 1/2] seccomp_filters: system call filtering using BPF
Steven Rostedt wrote:
> On Wed, 2012-01-11 at 11:25 -0600, Will Drewry wrote:
>
> > Filter programs may _only_ cross the execve(2) barrier if last filter
> > program was attached by a task with CAP_SYS_ADMIN capabilities in its
> > user namespace. Once a task-local filter program is attached from a
> > process without privileges, execve will fail. This ensures that only
> > privileged parent task can affect its privileged children (e.g., setuid
> > binary).
>
> This means that a non privileged user can not run another program with
> limited features? How would a process exec another program and filter
> it? I would assume that the filter would need to be attached first and
> then the execv() would be performed. But after the filter is attached,
> the execv is prevented?

Ugly method: Using ptrace(), trap after the execve() and issue fake
syscalls to install the filter. I feel dirty thinking it, in a good way.

LD_PRELOAD has been suggested. It's not 100% reliable because not all
executables are dynamic (on some uClinux platforms none of them are),
but it will usually work.

-- Jamie


\
 
 \ /
  Last update: 2012-01-12 18:39    [from the cache]
©2003-2011 Jasper Spaans