[CentOS] /bin/su wont work inside a chroot?

Mon Aug 2 00:41:43 UTC 2010
Gordon Messmer <yinyang at eburg.com>

On 08/01/2010 01:44 PM, JohnS wrote:
> It *WILL* work It is called "Outside to In"&&  mount -o bind will also.

You previously described symlinking "out" to the root filesystem, which 
is impossible.  Symlinks cannot resolve to files outside of a chroot 
environment.  Hard links can.

It is, however, possible to create a symlink in the primary root 
filesystem which points to a file inside a tree used for chroot, if that 
is what you mean by "outside to in".  In that case, your previous post 
was simply unclear.

> The difference depends on what is exactly the person needs.  IE (which
> way).  It will also allow a "Jail Break" Out&  In.  So security goes out
> the window.  In effect Zero Day here we are.

Symlinks do not allow you to break out of a chroot.  In fact, chroot 
isn't a security mechanism.  chroot will confine any non-root process, 
but any root process can escape a chroot simply by setting its cwd to 
the root directory and then calling chroot() to any directory.  The 
process will then have a cwd outside its own root filesystem, and can 
access the filesystem outside of the path it was originally using as its 

The term "zero day" normally describes a software exploit which was not 
previously known.  I don't believe it applies to anything you described.