Re: [PATCH ghak21 V2 3/4] audit: add refused symlink to audit_names

[Paul Moore]

On Tue, Mar 13, 2018 at 6:52 AM, Richard Guy Briggs <rgb@xxxxxxxxxx> wrote:
> On 2018-03-13 11:38, Steve Grubb wrote:
>> On Tue, 13 Mar 2018 06:11:08 -0400
>> Richard Guy Briggs <rgb@xxxxxxxxxx> wrote:
>>
>> > On 2018-03-13 09:35, Steve Grubb wrote:
>> > > On Mon, 12 Mar 2018 11:52:56 -0400
>> > > Richard Guy Briggs <rgb@xxxxxxxxxx> wrote:
>> > >
>> > > > On 2018-03-12 11:53, Paul Moore wrote:
>> > > > > On Mon, Mar 12, 2018 at 11:26 AM, Richard Guy Briggs
>> > > > > <rgb@xxxxxxxxxx> wrote:
>> > > > > > On 2018-03-12 11:12, Paul Moore wrote:
>> > > > > >> On Mon, Mar 12, 2018 at 2:31 AM, Richard Guy Briggs
>> > > > > >> <rgb@xxxxxxxxxx> wrote:
>> > > > > >> > Audit link denied events for symlinks had duplicate PATH
>> > > > > >> > records rather than just updating the existing PATH record.
>> > > > > >> > Update the symlink's PATH record with the current dentry
>> > > > > >> > and inode information.
>> > > > > >> >
>> > > > > >> > See: https://github.com/linux-audit/audit-kernel/issues/21
>> > > > > >> > Signed-off-by: Richard Guy Briggs <rgb@xxxxxxxxxx>
>> > > > > >> > ---
>> > > > > >> >  fs/namei.c | 1 +
>> > > > > >> >  1 file changed, 1 insertion(+)
>> > > > > >>
>> > > > > >> Why didn't you include this in patch 4/4 like I asked during
>> > > > > >> the previous review?
>> > > > > >
>> > > > > > Please see the last comment of:
>> > > > > > https://www.redhat.com/archives/linux-audit/2018-March/msg00070.html
>> > > > >
>> > > > > Yes, I just saw that ... I hadn't seen your replies on the v1
>> > > > > patches until I had finished reviewing v2.  I just replied to
>> > > > > that mail in the v1 thread, but basically you need to figure
>> > > > > out what is necessary here and let us know.  If I have to
>> > > > > figure it out it likely isn't going to get done with enough
>> > > > > soak time prior to the upcoming merge window.
>> > > >
>> > > > Steve?  I was hoping you could chime in here.
>> > >
>> > > If the CWD record will always be the same as the PARENT record,
>> > > then we do not need the parent record. Duplicate information is
>> > > bad. Like all the duplicate SYSCALL information.
>> >
>> > The CWD record could be different from the PARENT record, since I
>> > could have SYMLINK=/tmp/test/symlink, CWD=/tmp, PARENT=/tmp/test.
>> > Does the parent record even matter since it might not be a directory
>> > operation like creat, unlink or rename?
>>
>> There's 2 issues. One is creating the path if what we have is relative.
>> In this situation CWD should be enough. But if the question is whether
>> the PARENT directory should be included...what if the PARENT
>> permissions do not allow the successful name resolution? In that case
>> we might only get a PARENT record no? In that case we would need it.
>
> I think in the case of symlink creation, normal file create code path
> would be in effect, and would properly log parent and symlink source
> file paths (if a rule to log it was in effect) which is not something
> that would trigger a symlink link denied error.  Symlink link denied
> happens only when trying to actually follow the link before
> resolving the target path of a read/write/exec of the symlink target.
>
> If the parent permissions of the link's target don't allow successful
> name resolution then the symlink link denied condition isn't met, but
> rather any other rule that applies to the target path.

I'm guessing you are in the process of tracking all this down, but if
not, lets get to a point where we can answer this definitively and not
guess :)

-- 
paul moore
www.paul-moore.com