[refpolicy] write AVC on access()?

[dac.override@gmail.com (Dominick Grift)]

On Wed, Sep 10, 2014 at 11:05:59AM +0200, Pierre Ossman wrote:
> Dominick Grift wrote:
> 
> > A rule like this should do it:
> > 
> > dontaudit cupsd_t usr_t:file audit_access;
> 
> Thanks. That seems to be the correct approach for systems modern enough
> to have audit_access. But I want to support older versions as well, and
> figured that I'd be able to do so with an 'optional' section. Yet this:
> 
> > optional_policy(`
> > 	gen_require(`
> > 		type cupsd_t;
> > 		class file { audit_access };
> > 	')
> > 
> > 	dontaudit cupsd_t etc_t:file audit_access;
> > ')
> 
> Still results in:
> 
> > libsepol.permission_copy_callback: Module thinlinc depends on permission audit_access in class file, not satisfied (No such file or directory).
> 
> And if I leave it out of the require section:
> 
> > optional_policy(`
> >         gen_require(`
> >                 type cupsd_t;
> >         ')
> >         dontaudit cupsd_t etc_t:file audit_access;
> > ')
> 
> I get this:
> 
> > thinlinc.te":167:ERROR 'permission audit_access is not defined for class file' at token ';' on line 38285:
> > #line 167
> > 	dontaudit cupsd_t etc_t:file audit_access;
> 
> So I utterly fail to understand what 'optional' actually does. Is
> missing types the only thing it can check for?
> 

Yes right, it is about missing custmizable identifiers rather than missing security attributes

If you want to play it safe then you could consider:

dontaudit cupsd_t usr_t:file write;

I suppose that should also get rid of that event, although it would probably be a bit more prone to error

Another option might be to just add support for the audit_access av permission in your policy (access_vectors) even though it might
not be supported n the kernel

Ofcourse that would not really solve much since you will still end up with events on systems using a kernel that does not support audit_access

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Dominick Grift
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