Re: [patch 0/2] policy capability support

[Joshua Brindle <method@manicmethod.com>]

Stephen Smalley wrote:
> On Wed, 2007-12-05 at 15:35 -0500, Joshua Brindle wrote:
>   
>> Stephen Smalley wrote:
>>     
>>> On Wed, 2007-12-05 at 15:16 -0500, Joshua Brindle wrote:
>>>   
>>>       
>>>> Stephen Smalley wrote:
>>>>     
>>>>         
>>>>> On Wed, 2007-12-05 at 14:30 -0500, Todd Miller wrote:
>>>>>       
>>>>>           
>>>>>> Paul Moore wrote:
>>>>>>         
>>>>>>             
>>>>>>> The discussion for this appears to have gone quiet (at least I
>>>>>>> haven't seen anything else on this list).  Where do things currently
>>>>>>> stand?
>>>>>>>           
>>>>>>>               
>>>>>> At this point I'd be OK with requiring equivalence and throwing an error
>>>>>> otherwise.  I do think that this will result in usability issues that we
>>>>>> will have to address once people start using the caps.  However, with
>>>>>> only
>>>>>> a single cap defined so far it is not really possible to know how these
>>>>>> will end up being used.
>>>>>>         
>>>>>>             
>>>>> We could try to come up with a solution at least for allowing clean
>>>>> upgrades from F8 (w/o any caps) to F9 (likely w/ peer cap defined)
>>>>> without requiring manual user intervention for dealing with local
>>>>> modules.
>>>>>
>>>>>       
>>>>>           
>>>> This was my exact objection to using an intersection or equivalence. IMO 
>>>> it is incompatible to require all modules to be the same and to also 
>>>> require upgrades to work without manual intervention.
>>>>
>>>> Do you still think unioning is wrong?
>>>>     
>>>>         
>>> Yes, I'm still against (automatic, default) unioning of the capabilities
>>> by the linker - that is clearly not a safe default.  semodule could
>>> possibly override that behavior based on an option though, at which
>>> point the %post scriptlet in the policy rpm could use that option if we
>>> wanted to force it w/o user intervention.
>>>
>>>   
>>>       
>> And when a user installs a new module via audit2allow they have to know 
>> to select --ignore-stuff-the-modules-say-and-do-something-else-anyway? I 
>> don't like this idea either.
>>     
>
> Shrug.  Then we'll just go with equivalence only, and the user will have
> to remove local modules before upgrade.
>   

Well, Todd just suggested, rather than forcing install (which has 
strange semantics anyway since it isn't clear which set of caps would 
end up in the kernel policy) we could have an --upgrade-polcaps option 
that unions the bitmaps of the modules installed. It isn't pretty but it 
requires manual intervention to union them instead of doing so 
automatically. This obviously will break local policies that do not 
support the cap but need to. The user will have to figure out how to 
update those local policies to add the required permissions, this isn't 
any different than adding new permission checks to the kernel though.

I'm still concerned about audit2allow's ability to decide what caps to 
put in a policy module being generated. I also have concerns about new 
policy modules that are being written by hand, the users aren't going to 
necessarily know what caps are available and why they should care. I'm 
sure SLIDE will be able to take care of that though ;)


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