Re: MLS dominance check behavior on el7

[Ted Toth <txtoth@gmail.com>]

[-- Attachment #1: Type: text/plain, Size: 4205 bytes --]

On Wed, Sep 12, 2018 at 9:57 AM Ted Toth <txtoth@gmail.com> wrote:

>
>
> On Wed, Sep 12, 2018 at 9:36 AM Dominick Grift <dac.override@gmail.com>
> wrote:
>
>> On Wed, Sep 12, 2018 at 09:57:20AM -0400, Stephen Smalley wrote:
>> > On 09/12/2018 09:26 AM, Ted Toth wrote:
>> > >
>> > >
>> > > On Wed, Sep 12, 2018 at 8:04 AM Stephen Smalley <sds@tycho.nsa.gov
>> > > <mailto:sds@tycho.nsa.gov>> wrote:
>> > >
>> > >     On 09/11/2018 04:59 PM, Ted Toth wrote:
>> > >      > That's awesome and now it's got me thinking about other
>> > >      > classes/permissions that we could implement. Can cil macros
>> can be
>> > >      > referenced in .te/.if files?
>> > >
>> > >     Not sure I understand your question.  You can't directly embed cil
>> > >     statements in .te/.if files.  However, if you define a
>> class/permission
>> > >     in a .cil module, you can certainly specify a require on it and
>> use it
>> > >     from a conventional .te/.if module, ala:
>> > >     $ cat > usemcstrans.te <<EOF
>> > >     policy_module(usemcstrans, 1.0)
>> > >
>> > >     require {
>> > >              class mcstrans { color_use };
>> > >              attribute domain;
>> > >     }
>> > >
>> > >     allow domain self:mcstrans color_use;
>> > >     EOF
>> > >
>> > >     $ make -f /usr/share/selinux/devel/Makefile usemcstrans.pp
>> > >     $ sudo semodule -i usemcstrans.pp
>> > >
>> > >
>> > > If the cil contained:
>> > >
>> > > (macro use_color (type caller) (allow caller self mcstrans
>> (color_use)))
>> > >
>> > > then in x.te can I use the macro:
>> > >
>> > > type x_t;
>> > > use_color(x_t)
>> >
>> > Sorry, no.  The macros used in .te/.if files are just m4 definitions
>> handled
>> > at the preprocessing stage, not a feature of the module language.  The
>> CIL
>> > macros are directly supported by the CIL compiler, but they won't be
>> visible
>> > to the module compiler.  Also, you are missing several parentheses above
>> > (I'm not fond of the lisp-like syntax myself).  In a CIL module, I
>> think the
>> > correct syntax would be:
>> >
>> > (macro use_color ((type caller)) (allow caller self (mcstrans
>> (color_use))))
>> >
>> > (call use_color(x_t))
>> >
>> > Or you could define a m4 macro in an .if file and use that in a .te
>> file.
>> > Or both.
>> >
>>
>> Ideally you would have all of your policy written in CIL or in a
>> high-level language that was designed to leverage CIL.
>>
>
> Unfortunately I/we don't live in an ideal world :( but thanks for the
> pointers.
>
>
>>
>> My DSSP2 policy is a CIL-only policy. In there I also leverage unordered
>> classes, Meaning that for example if you remove or disable the mcstrans
>> module then you automatically also remove or disable  the access vectors
>> that mcstrans manages.
>>
>> minimal:
>>
>> https://github.com/DefenSec/dssp2-minimal
>>
>> standard (my personal policy based on top of minimal):
>>
>> https://github.com/DefenSec/dssp2-standard/commits/master
>>
>> DSSP2 does not support enforcement of confidentiality though
>>
>> > _______________________________________________
>> > Selinux mailing list
>> > Selinux@tycho.nsa.gov
>> > To unsubscribe, send email to Selinux-leave@tycho.nsa.gov.
>> > To get help, send an email containing "help" to
>> Selinux-request@tycho.nsa.gov.
>>
>> --
>> Key fingerprint = 5F4D 3CDB D3F8 3652 FBD8  02D5 3B6C 5F1D 2C7B 6B02
>> https://sks-keyservers.net/pks/lookup?op=get&search=0x3B6C5F1D2C7B6B02
>> Dominick Grift
>>
>
I added a security class and permission using the following cil:
(block mcstrans
    (typeattributeset cil_gen_require  setrans_t)
    (typeattributeset cil_gen_require user_t)
    (class level_color (pick_using_dominance))
    (classorder (unordered level_color))

    (mlsconstrain (level_color (pick_using_dominance)) (dom h1 h2))

    (allow setrans_t self (level_color (pick_using_dominance))))

and this works for the mcscolor code I changed to use it. However I wrote
some python code to test the class/permission (using
security_compute_av_raw) and ran it before adding an allow rule for the
python code type and no avc was generated as I'd expected. Is there
anything different about adding a security class this way that would affect
avc generation?

[-- Attachment #2: Type: text/html, Size: 6263 bytes --]