[Freeipa-devel] [PATCH 0002] Port from python-krbV to python-gssapi

[Michael Šimáček]

On 2015-08-25 18:43, Robbie Harwood wrote:
> Jan Cholasta <jcholast at redhat.com> writes:
>
>> On 25.8.2015 12:46, Michael Šimáček wrote:
>>> On 2015-08-25 12:38, Alexander Bokovoy wrote:
>>>> On Tue, 25 Aug 2015, Michael Šimáček wrote:
>>>>> On 2015-08-24 20:29, Robbie Harwood wrote:
>>>>>> Michael Šimáček <msimacek at redhat.com> writes:
>>>>>>> On 2015-08-24 17:49, Simo Sorce wrote:
>>>>>>>> On Mon, 2015-08-24 at 17:18 +0200, Michael Šimáček wrote:
>>>>>>>>> On 2015-08-24 14:50, Jan Cholasta wrote:
>>>>>>>>>
>>>>>>>>> Fixed. python-gssapi has a display_as method that could pull the
>>>>>>>>> name
>>>>>>>>> from it, but it doesn't work in current version, therefore using
>>>>>>>>> partition to split on '@'
>>>>>>
>>>>>> It's actually a bug in MIT Krb5, as we noted in your bug[0].  So this:
>>>>>>
>>>>>>> -        user = api.Command.user_show(unicode(principal[0]))['result']
>>>>>>> +        user =
>>>>>>> api.Command.user_show(principal.partition('@')[0])['result']
>>>>>>
>>>>>> is working around a bug in specific Kerberos versions.  If people are
>>>>>> okay with merging such code, then I guess this is fine; I would
>>>>>> personally not do so because there is not a clear point at which it can
>>>>>> be removed.  At the very least, we should wait until we see what
>>>>>> versions of krb5 MIT is going to fix.
>>>>>>
>>>>>> Otherwise, looks good.
>>>>>>
>>>>>> [0]: https://github.com/pythongssapi/python-gssapi/issues/79
>>>>>>
>>>>>
>>>>> python-krbV migration is blocking support for Python 3. The bug
>>>>> doesn't have any fix upstream yet and there are two bugs actually, the
>>>>> second one is in python-gssapi, which I've just reported [1]. Waiting
>>>>> for two bugs to be fixed could be detrimental to py3 migration as we
>>>>> don't have much time left. And I'm no longer sure that display_as
>>>>
>>>> I don't buy this.
>>>>
>>>> We have plenty of time for solving these bugs. Remember, that Samba
>>>> DCE RPC bindings aren't migrated to Python 3 either and will not be
>>>> before release of Samba 4.4. For Samba 4.3 it is simply too late.
>>>>
>>>> So we are still far away from full Python3 migration for FreeIPA and
>>>> waiting for solving these two bugs is OK.
>>>
>>> If fixing them solves anything at all. I planned to use
>>> display_as(NameType.user), but when trying it on Name object with
>>> name_type set (which doesn't trigger the segfault), it doesn't seem to
>>> work either. I get:
>>> gssapi.raw.exceptions.OperationUnavailableError: Major (1048576): The
>>> operation or option is not available or unsupported, Minor (0): Unknown
>>> error
>>>
>>> Robbie, can you clarify whether display_as could be actually used to get
>>> the first component of the principal reliably?
>
> display_as should behave in accordance with its docs; anything else is a
> bug report, which you filed.  I don't know what you're asking me for
> beyond that.
>

Why I mentioned display_as at all is that I initially assumed it could 
be used for this, but it was only an assumption because I couldn't get 
around the segfault. Later on, the cause of the segfault was found and I 
was able to try the method and I found out that it probably cannot be 
used for this purpose (i. e. extracting the first component of the 
principal) regardless of the two bugs. How I thought it would be used:
import gssapi
cred = gssapi.Credentials()
user = cred.name.display_as(gssapi.NameType.user)

What I got:
gssapi.raw.exceptions.OperationUnavailableError: Major (1048576): The 
operation or option is not available or unsupported, Minor (0): Unknown 
error

This seems more like the method is not intended to be used this way. So 
I'm asking you whether it is a bug or whether there is another way to do 
it. Otherwise display_as cannot be used here.

>> As I have written in the other thread, we use "principal.split('@')" in
>> other parts of IPA, so "principal.partition('@')" should be OK as well.
>>
>> This patch works for me, so ACK.
>>
>> Unless there are any further objections, I would like to push it.
>
> I think the newest iteration of this
>
>> user = api.Command.user_show(principal.partition('@')[0].partition('/')[0])['result']
>
> is even worse, but if it is decided to merge, then hopefully we can be
> rid of it quickly.

It is splitting a string of known format in a way that is used in other 
places of freeipa. What is specifically so bad about it? What do you 
suggest as an alternative?