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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 v3] secilc/docs: document expandtypeattribute
Date: Fri, 31 Jul 2020 23:07:17 +0200
Message-ID: <ypjlpn8bl7ga.fsf@defensec.nl> (raw)
In-Reply-To: <CAP+JOzSgp1Xgv29v__SAjZthonqRw=ZmYJ_3=MZm5FX8EOjDBw@mail.gmail.com> (James Carter's message of "Fri, 31 Jul 2020 16:22:44 -0400")

James Carter <jwcart2@gmail.com> writes:

> On Fri, Jul 31, 2020 at 4:12 PM Dominick Grift
> <dominick.grift@defensec.nl> wrote:
>>
>> James Carter <jwcart2@gmail.com> writes:
>>
>> > On Fri, Jul 31, 2020 at 3:26 AM Dominick Grift
>> > <dominick.grift@defensec.nl> wrote:
>> >>
>> >> James Carter <jwcart2@gmail.com> writes:
>> >>
>> >> > On Thu, Jul 30, 2020 at 9:14 AM Dominick Grift
>> >> > <dominick.grift@defensec.nl> wrote:
>> >> >>
>> >> >> This was added for Androids Treble in 2017.
>> >> >>
>> >> >> I was unsure whether this belongs in type_statements or in conditional_statements.
>> >> >>
>> >> >
>> >> > I think that it fits best with the type statements as you have it.
>> >> >
>> >> >> Signed-off-by: Dominick Grift <dominick.grift@defensec.nl>
>> >> >> ---
>> >> >> v2: overriden is overridden
>> >> >> v3: add link to README.md
>> >> >>
>> >> >>  secilc/docs/README.md              |  1 +
>> >> >>  secilc/docs/cil_type_statements.md | 38 ++++++++++++++++++++++++++++++
>> >> >>  2 files changed, 39 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..f819b3c6 100644
>> >> >> --- a/secilc/docs/cil_type_statements.md
>> >> >> +++ b/secilc/docs/cil_type_statements.md
>> >> >> @@ -213,6 +213,44 @@ This example is equivalent to `{ domain -kernel.process -ueventd.process -init.p
>> >> >>          )
>> >> >>      )
>> >> >>
>> >> >> +expandtypeattribute
>> >> >> +-------------------
>> >> >> +
>> >> >> +Allows expansion compiler defaults for one or more previously declared [`typeattribute`](cil_type_statements.md#typeattribute) identifiers to be overridden.
>> >> >
>> >> > The wording confused me at first.
>> >> > I think "Overrides the compiler defaults for the expansion of one ...
>> >> > identifiers." would be clearer.
>> >> >
>> >> >> +
>> >> >> +**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.</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>
>> >> >> +
>> >> >> +**Example:**
>> >> >> +
>> >> >> +This example will use the expandtypeattribute statement to forcibly expand a previously declared `domain` type attribute.
>> >> >> +
>> >> >> +    (expandtypeattribute domain true)
>> >> >> +
>> >> >
>> >> > It would be nice to have another example that shows a list of type
>> >> > attributes, so there is an example of that syntax as well.
>> >>
>> >> I was looking into an example but turns out that either i am
>> >> misunderstanding this functionality or that it does not work as advertised:
>> >>
>> >> Example:
>> >>
>> >> 1. compiler defaults to expand typeattributes with less
>> >> than four members
>> >> 2. override pets and dogs expansion in policy
>> >>
>> >> # cat > mytest.cil <<EOF
>> >> (sid mysid)
>> >> (sidorder (mysid))
>> >>
>> >> (class myclass (mypermission))
>> >> (classorder (unordered myclass))
>> >>
>> >> (type blue)
>> >> (type green)
>> >> (type red)
>> >> (typeattribute colors)
>> >> (typeattributeset colors (blue green red))
>> >>
>> >> (type dog)
>> >> (type cat)
>> >> (type goldfish)
>> >> (typeattribute pets)
>> >> (typeattributeset pets (dog cat goldfish))
>> >>
>> >> (dontaudit pets colors (myclass (mypermission)))
>> >>
>> >> (expandtypeattribute (colors pets) false)
>> >> EOF
>> >>
>> >> # secilc -v -X 4 mytest.cil
>> >> # sesearch policy.32 --dontaudit
>> >>
>> >
>> > The key is that expandtypeattribute works differently for the default
>> > behavior than when you ask for attributes to be expanded.
>> >
>> > The default rules for removing attributes are complex. In general,
>> > attributes automatically created when converting a binary module to
>> > CIL; attributes that are not used in allow and dontaudit rules; and
>> > attributes that have only one type assigned are all removed. This
>> > means that the attribute rule and the typeattributeset rules for the
>> > attribute are removed and all rules using the attribute are expanded.
>> > Using expandtypeattribute in this case will keep the attribute
>> > declaration, the typeattributeset rules, and any allow rules.
>> >
>> > When you use "-X SIZE" all allow rules with attributes that contain
>> > less than SIZE types will be expanded and the attribute removed. Using
>> > expandtypeattribute in this case will cause the attribute declaration
>> > and the typeattributeset rules to be retained, but the allow rules
>> > will still be expanded.
>> >
>> > I just verified that everything does work like that.
>> >
>> > It is a bit of a mess, but it is working as intended.
>> >
>> > I probably need to document how the default expansion works. ;)
>>
>>
>> So that makes the "false" scenario practically irrelevant? when would
>> one ever use "false" instead of "true"?
>>
>
> That is actually the most valuable option. It is the way to ensure
> that an attribute definition is not removed. It is being used, for
> example, by Google to keep attributes that are used in the neverallow
> rules in their compatibility test suite from being expanded.

Good thing it is friday. I think i need to sleep on this a couple of
day's and see if I can make some sense out of all of this.

>
> Jim
>
>> >
>> > Thanks,
>> > Jim
>> >
>> >
>> >> >
>> >> > Thanks for doing this.
>> >> > Jim
>> >> >
>> >> >>  typebounds
>> >> >>  ----------
>> >> >>
>> >> >> --
>> >> >> 2.28.0.rc1
>> >> >>
>> >>
>> >> --
>> >> 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: 19+ 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 [this message]
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
2020-08-05 19:23                     ` James Carter
2020-08-05 19:48                       ` [PATCH v5] " Dominick Grift
2020-08-05 20:22                         ` James Carter

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