[Freeipa-devel] [RANT] --setattr validation is a minefield.

[Stephen Ingram]

On Tue, Apr 10, 2012 at 10:25 AM, Petr Viktorin <pviktori at redhat.com> wrote:
> On 04/10/2012 07:07 PM, Martin Kosek wrote:
>>
>> On Tue, 2012-04-10 at 17:03 +0200, Jan Cholasta wrote:
>>>
>>> On 10.4.2012 16:00, Petr Viktorin wrote:
>>>>
>>>> I'm aware that we have backwards compatibility requirements so we have
>>>> to stick with unfortunate decisions, but I wanted you to know what I
>>>> think. Please tell me I'm wrong!
>>>>
>>>>
>>>>
>>>> It is not clear what --{set,add,del}attr and friends should do. On the
>>>> one hand they should be powerful -- presumably as powerful as
>>>> ldapmodify. On the other hand they should be checked to ensure they
>>>> can't be used to break the system. These requirements are contradictory.
>>>> And in either case we're doing it wrong:
>>>> - If they should be all-powerful, we shouldn't validate them.
>>>> - If they shouldn't break the system we can just disable them for
>>>> IPA-managed attributes. My understanding is that they were originally
>>>> only added for attributes IPA doesn't know about. People can still use
>>>> ldapmodify to bypass validation if they want.
>>>> - If somewhere in between, we need to clearly define what they should
>>>> do, instead of drawing the line ad-hoc based on individual details we
>>>> forgot about, as tickets come from QE.
>>>>
>>>>
>>>> I would hope people won't use --setattr for IPA-managed attributes.
>>>> Which would however mean we won't get much community testing for all
>>>> this extra code.
>>>>
>>>>
>>>> Then, there's an unfortunate detail in IPA implementation: attribute
>>>> Params need to be cloned to method objects (Create, Update, etc.) to
>>>> work properly (e.g. get the `attribute` flag set). If they are marked
>>>> no_update, they don't get cloned, so they don't work properly.
>>>> Yet --setattr apparently needs to be able to update and validate
>>>> attributes marked no_update (this ties to the confusing requirements on
>>>> --setattr I already mentioned). This leads to doing the same work again,
>>>> slightly differently.
>>>>
>>>>
>>>>
>>>> tl;dr: --setattr work on IPA-managed attributes (with validation) is a
>>>> mistake. It adds no functionality, only complexity. We don't want people
>>>> to use it. It will cost us a lot of maintenance work to support.
>>>>
>>>>
>>>> Thank you for listening. A patch for the newest regression is coming up.
>>>>
>>>
>>> I wholeheartedly agree.
>>
>>
>> This is indeed a mine field and we need to make a look from at the issue
>> from all sides before accepting a decision.
>
>
> Yes.
>
>
>>>
>>> Like you said above, we should either not validate --{set,add,del}attr
>>> or don't allow them on known attributes.
>>
>>
>> IMHO, validating attributes we manage in the same way for both --setattr
>> and standard attrs is not that wrong. It is a good precaution, because
>> if we let an unvalidated value in, it can make even a bigger mess later
>> in our pre_callbacks or post_callbacks where we assume that at this
>> point everything is valid.
>
>
> Then we should validate *exactly* the same way, including not allowing
> no_update attributes to be updated.
>
>
>> If somebody wants to modify attributes in an uncontrolled, unvalidated
>> way, he is free to use ldapmodify or other tool to play with raw LDAP
>> values. Without our guarantee of course.
>
>
> That's clear.
>
>
>> But if he chooses to use our --{set,add,del}attr we should at least help
>> him to not shoot himself to the leg and validate/normalize/encode the
>> value. I don't know how many users use this API, but removing a support
>> for all managed attributes seems as a big compatibility break to me.
>
>
> Well, it was broken (see https://fedorahosted.org/freeipa/ticket/2405, 2407,
> 2408), so I don't think many people used it.
>
> Anyway, what's the use case? Why would the user want to use --setattr for
> validated attributes? Is our regular API lacking something?

As a user of the IPA I thought I would throw in our use scenario. Let
me first say that I come to IPA having used Kerberos/LDAP solution
previously so I *really* appreciate what you've been able to do here.
That said, one of the things we are using IPA for is email
configuration. Although the mail attribute is available, we need to
separate by attribute the primary address from the aliases (for
searching the directory) so we need mailAlternateAddress. Luckily, it
is already in the schema. All we have to do is add the mailRecipient
objectclass. It's really nice to be able to add (and hopefully soon
remove) one objectclass without having to go back to ldap commands. I
certainly wouldn't anticipate changing or removing any IPA attributes,
but it sure is nice to have this feature for extra attributes.

Steve