Re: patch to make Linux capabilities into something useful (v 0.3.1)

[Kyle Moffett <mrmacman_g4@mac.com>]

On Sep 07, 2006, at 14:21:15, James Antill wrote:
> David Madore <david.madore@ens.fr> writes:
>
>> Hi.
>>
>> As we all know, capabilities under Linux are currently crippled to  
>> the point of being useless.  Attached is a patch (against 2.6.18- 
>> rc6) which attempts to make them work in a reasonably useful way  
>> and at the same time not break anything.  On top of the  
>> "additional" capabilities that lead up to root, it also adds  
>> "regular" capabilities which all processes have by default and  
>> which can be removed from specifically untrusted programs.
>
> Just a minor comment, can you break out the OPEN into at least  
> OPEN_R, OPEN_NONFILE_W and OPEN_W (possibly OPEN_A, but I don't  
> want that personally). The case I'm thinking about are network  
> daemons that need to open+write to the syslog socket but only have  
> read access elsewhere.
>
> Also there is much more than just bind9 using capabilities, the  
> obvious ones that come to mind are NOATIME and AUDIT.

To be honest, once you get to the point of having an OPEN_NONFILE_W  
capability you should really just be using SELinux.  Instead of  
spewing policy all over your filesystem xattrs you put it all into a  
single set of fairly admin-readable policy files, and it includes  
more fine-grained operations than you have space for in 32 bits of  
"un"-capabilities.  It also conveniently supports the existing pseudo- 
POSIX capabilities.  You can effectively say "root, netadmin, and  
netuser users are allowed to run ping programs which automatically  
transition into the ping domain and get CAP_NET_RAW privileges" in  
your binary policy, then just leave ping as chmod "755" and be done  
with it.

Cheers,
Kyle Moffett