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From: Dominick Grift <dominick.grift@defensec.nl>
To: James Carter <jwcart2@gmail.com>
Cc: SElinux list <selinux@vger.kernel.org>
Subject: Re: [PATCH v4] secilc/docs: document expandtypeattribute
Date: Tue, 04 Aug 2020 22:29:10 +0200
Message-ID: <ypjl7due88a1.fsf@defensec.nl> (raw)
In-Reply-To: <CAP+JOzRUPpWXXmmuX5zdS1qCCbhpAXm8uO9JXvy+pYeBOoGbnA@mail.gmail.com> (James Carter's message of "Tue, 4 Aug 2020 16:23:41 -0400")

James Carter <jwcart2@gmail.com> writes:

> On Tue, Aug 4, 2020 at 11:48 AM Dominick Grift
> <dominick.grift@defensec.nl> wrote:
>>
>> James Carter <jwcart2@gmail.com> writes:
>>
>> > On Tue, Aug 4, 2020 at 3:18 AM Dominick Grift
>> > <dominick.grift@defensec.nl> wrote:
>> >>
>> >> James Carter <jwcart2@gmail.com> writes:
>> >>
>> >> > On Sun, Aug 2, 2020 at 8:39 AM Dominick Grift
>> >> > <dominick.grift@defensec.nl> wrote:
>> >> >>
>> >> >> This was added for Androids Treble in 2017.
>> >> >>
>> >> >> Signed-off-by: Dominick Grift <dominick.grift@defensec.nl>
>> >> >> ---
>> >> >> v2: overriden is overridden
>> >> >> v3: add link to README.md
>> >> >> v4: rephrase and add another example
>> >> >>
>> >> >>  secilc/docs/README.md              |  1 +
>> >> >>  secilc/docs/cil_type_statements.md | 44 ++++++++++++++++++++++++++++++
>> >> >>  2 files changed, 45 insertions(+)
>> >> >>
>> >> >> diff --git a/secilc/docs/README.md b/secilc/docs/README.md
>> >> >> index 3f1838e6..efab2a71 100644
>> >> >> --- a/secilc/docs/README.md
>> >> >> +++ b/secilc/docs/README.md
>> >> >> @@ -126,6 +126,7 @@ CIL (Common Intermediate Language)
>> >> >>    * [typealiasactual](cil_type_statements.md#typealiasactual)
>> >> >>    * [typeattribute](cil_type_statements.md#typeattribute)
>> >> >>    * [typeattributeset](cil_type_statements.md#typeattributeset)
>> >> >> +  * [expandtypeattribute](cil_type_statements.md#expandtypeattribute)
>> >> >>    * [typebounds](cil_type_statements.md#typebounds)
>> >> >>    * [typechange](cil_type_statements.md#typechange)
>> >> >>    * [typemember](cil_type_statements.md#typemember)
>> >> >> diff --git a/secilc/docs/cil_type_statements.md b/secilc/docs/cil_type_statements.md
>> >> >> index f9dd3a76..41f0f01a 100644
>> >> >> --- a/secilc/docs/cil_type_statements.md
>> >> >> +++ b/secilc/docs/cil_type_statements.md
>> >> >> @@ -213,6 +213,50 @@ This example is equivalent to `{ domain -kernel.process -ueventd.process -init.p
>> >> >>          )
>> >> >>      )
>> >> >>
>> >> >> +expandtypeattribute
>> >> >> +-------------------
>> >> >> +
>> >> >> +Overrides the compiler defaults for the expansion of one or more previously declared [`typeattribute`](cil_type_statements.md#typeattribute) identifiers.
>> >> >> +
>> >> >> +Note that this statement can be overridden at compile-time with `secilc -X SIZE` and that this functionality is not intended to override `secilc -X SIZE` for individual type attributes!
>> >> >> +
>> >>
>> >> <snip>
>> >> > When the value
>> >> > is false, the type attribute will not be removed from the policy, even
>> >> > if the default expand rules or "-X" option cause the rules involving
>> >> > the type attribute to be expanded.
>> >>
>> >> Yes but I cannot produce that. In my earlier test the type attribute
>> >> was expanded regardless of the -X option.
>> >>
>> >> In my test I instructed secilc to expand all attributes with more than 3
>> >> members (-X 4), then I added a expandtypeattribute statement telling
>> >> secilc to not expand pets and colors.
>> >>
>> >> The result was that it expanded pets and colors anyway.
>> >>
>> >
>> > I see the source of your confusion now. "-X 4" means that all
>> > attributes with LESS than 4 types associated with it will be expanded.
>>
>> I think its important to clarify this in the documentation. ie:
>> expandattribute false will not work if you use -X (-X will override the
>> false statement)
>>
>> I think that is unintuitive, I would actually want to be able to for
>> example expand all attributes with less then 4 members except a few
>> specific ones.
>>
>
> It is poorly named at this point. I think it was a victim of multiple
> changes over time. A better name now would be removeattribute. That
> would be more accurate, because what is really being controlled is
> whether the attribute is kept as defined in the policy or not.
>
> I am not sure what advantage there would be to expanding and removing
> all except a few selected attributes with less than 4 members, except
> for the case when you needed those selected attributes to remain
> defined in the policy.  Not much space is going to be saved by not
> expanding them. Ok, I guess the advantage would be that the name of
> the rule would make more sense. I will grant that.
>
> At any rate, the name stinks, but the functionality is exactly what is
> needed. I can trade a large policy for quicker access checks by using
> the "-X SIZE" option and I can retain the definitions of the
> attributes that need to be defined using expandattribute false.
>
> This whole discussion is why keeping the selinux-notebook in sync with
> language changes will be very valuable practice.

I agree and that is why I added the "Note", so that readers have some
reference when they figure out that they cannot override -X for
specified attributes.

If you still do not like this v4 patch then tell me (again) what you
want in there and I will put it in there without argueing so that we can
wrap this up.

>
> Thanks,
> Jim
>
>> >
>> > Jim
>> >
>> >> >
>> >> > Thanks,
>> >> > Jim
>> >> >
>> >> >> +**Statement definition:**
>> >> >> +
>> >> >> +    (expandtypeattribute typeattribute_id true|false)
>> >> >> +
>> >> >> +**Where:**
>> >> >> +
>> >> >> +<table>
>> >> >> +<colgroup>
>> >> >> +<col width="25%" />
>> >> >> +<col width="75%" />
>> >> >> +</colgroup>
>> >> >> +<tbody>
>> >> >> +<tr class="odd">
>> >> >> +<td align="left"><p><code>expandtypeattribute</code></p></td>
>> >> >> +<td align="left"><p>The <code>expandtypeattribute</code> keyword.</p></td>
>> >> >> +</tr>
>> >> >> +<tr class="even">
>> >> >> +<td align="left"><p><code>typeattribute_id</code></p></td>
>> >> >> +<td align="left"><p>One or more previously declared
>> >> >> <code>typeattribute</code> identifiers. Multiple entries consist of
>> >> >> a space separated list enclosed in parentheses '()'.</p></td>
>> >> >> +</tr>
>> >> >> +<tr class="odd">
>> >> >> +<td align="left"><p><code>true | false</code></p></td>
>> >> >> +<td align="left"><p>Either true or false.</p></td>
>> >> >> +</tr>
>> >> >> +</tbody>
>> >> >> +</table>
>> >> >> +
>> >> >> +**Examples:**
>> >> >> +
>> >> >> +This example uses the expandtypeattribute statement to forcibly expand a previously declared `domain` type attribute.
>> >> >> +
>> >> >> +    (expandtypeattribute domain true)
>> >> >> +
>> >> >> +This example uses the expandtypeattribute statement to not expand
>> >> >> previously declared `file_type` and `port_type` type attributes
>> >> >> regardless of compiler defaults.
>> >> >> +
>> >> >> +    (expandtypeattribute (file_type port_type) false)
>> >> >> +
>> >> >>  typebounds
>> >> >>  ----------
>> >> >>
>> >> >> --
>> >> >> 2.28.0
>> >> >>
>> >>
>> >> --
>> >> gpg --locate-keys dominick.grift@defensec.nl
>> >> Key fingerprint = FCD2 3660 5D6B 9D27 7FC6  E0FF DA7E 521F 10F6 4098
>> >> https://sks-keyservers.net/pks/lookup?op=get&search=0xDA7E521F10F64098
>> >> Dominick Grift
>>
>> --
>> gpg --locate-keys dominick.grift@defensec.nl
>> Key fingerprint = FCD2 3660 5D6B 9D27 7FC6  E0FF DA7E 521F 10F6 4098
>> https://sks-keyservers.net/pks/lookup?op=get&search=0xDA7E521F10F64098
>> Dominick Grift

-- 
gpg --locate-keys dominick.grift@defensec.nl
Key fingerprint = FCD2 3660 5D6B 9D27 7FC6  E0FF DA7E 521F 10F6 4098
https://sks-keyservers.net/pks/lookup?op=get&search=0xDA7E521F10F64098
Dominick Grift

  reply index

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-30  9:23 [PATCH] " Dominick Grift
2020-07-30 11:45 ` [PATCH v2] " Dominick Grift
2020-07-30 13:11   ` [PATCH v3] " Dominick Grift
2020-07-30 22:22     ` James Carter
2020-07-31  7:26       ` Dominick Grift
2020-07-31 19:50         ` James Carter
2020-07-31 20:12           ` Dominick Grift
2020-07-31 20:22             ` James Carter
2020-07-31 21:07               ` Dominick Grift
2020-08-02 12:34       ` [PATCH v4] " Dominick Grift
2020-08-03 20:56         ` James Carter
2020-08-04  7:18           ` Dominick Grift
2020-08-04 14:45             ` James Carter
2020-08-04 15:48               ` Dominick Grift
2020-08-04 20:23                 ` James Carter
2020-08-04 20:29                   ` Dominick Grift [this message]
2020-08-05 19:23                     ` James Carter
2020-08-05 19:48                       ` [PATCH v5] " Dominick Grift
2020-08-05 20:22                         ` James Carter
2020-08-17 15:57                           ` Stephen Smalley

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