Re: Using dyntransition to reduce privileges for Web application

[Scott Gifford]

On Sun, Feb 20, 2011 at 4:05 PM, Dominick Grift <domg472(a)gmail.com&gt; wrote:

>  On 02/20/2011 09:47 PM, Scott Gifford wrote:
>  > On Sun, Feb 20, 2011 at 12:02 PM, Dominick Grift <domg472(a)gmail.com&gt;
>  wrote:
>  
[ ... ]


>   >>> from /policy/mcs:
>  >>>
>  >>> # Note:
>  >>> #  - getattr on dirs/files is not constrained.
>  >>> #  - /proc/pid operations are not constrained.
>  >>>
>  >>> so that explains the above
>  >>
>  >
>  > Ah, yes it does, thanks!  I wonder if I can adjust this policy to get
>  > different behavior, or if it's hardcoded somewhere outside the policy?
>  >
>
>  No, not hardcoded. This is just configuration (policy) you can define
>  your own constraints, or modify existing ones.
>  
OK, I think I've got this.  I removed the "or ( t2 == domain )" from these
rules in policy/mcs:

   -
   - mlsconstrain dir { create getattr setattr read write link unlink rename
   search add_name remove_name reparent rmdir lock ioctl }
   -        (( h1 dom h2 ) or ( t2 == domain ) or ( t1 == mlsfileread ));
   -
   - mlsconstrain file { read }
   -        (( h1 dom h2 ) or ( t2 == domain ) or ( t1 == mlsfileread ));

 and I seem to be getting the behavior I want.  Anybody see any risks or
downsides to this?

For long-term maintenance, it looks like I can't override this in my own
module, I will need to patch the base policy, maybe by adding another patch
to the serefpolicy-2.4.6 RPM specfile and maintaining this by hand?  Is
there a better way to maintain customizations to the base policy?

I think I can automatically generate a unique category set from a PID by
using two MCS categories to represent each bit of the PID, the first for a
0-bit and the second for a 1-bit.  That will take 32 categories for a 16-bit
PID, which seems reasonable.

Thanks for the help!

-----Scott.