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Re: ITS#8866 (was: ITS review 6/14/2019)

On 6/27/19 6:37 PM, Howard Chu wrote:
> Michael Ströder wrote:
>> On 6/27/19 6:23 PM, Michael Ströder wrote:
>>> On 6/27/19 6:18 PM, Howard Chu wrote:
>>>> Michael Ströder wrote:
>>>>> On 6/14/19 5:15 PM, Quanah Gibson-Mount wrote:
>>>>>> Thanks to Ondrej, this list is a bit shorter now. :)
>>>>>
>>>>> But one more I'd love to see in 2.4.48:
>>>>>
>>>>> ITS#8866: RFE: slapo-constraint to return filter used in diagnostic message
>>>>>
>>>>> https://www.openldap.org/its/index.cgi?findid=8866
>>>>
>>>> I don't believe the information disclosure issues have been
>>>> sufficiently answered there. Overall it's a bad idea and goes against
>>>> our standing policy of minimal disclosure.
>>> Sorry, you already have the disclosure.
>>>
>>> Citing from my old e-mail found here:
>>> https://www.openldap.org/lists/openldap-devel/201711/msg00003.html
>>>
>>>> But this problem exists anyway because an attacker can probe
>>>> values by adding entries with non-unique attributes and determine
>>>> whether an attribute value exists or not by distinguishing the result
>>>> code constraintViolation(19) vs. insufficientAccessRights(50).
>>>> Even worse this even works in case the attacker does not have read
>>>> access anywhere!
> 
> Then that's a bug that should be fixed.

If you really want to fix this bug then you have to fully enforce access
control when processing the write operation *before* enforcing the
constraints. (I guess this is not easily done with the current overlay
stack processing.)

But if you fixed it then the disclosure will only happen if the user is
authorized to modify the entry. So same fix for the very same problem. ;-)

Conclusion:
1. Applying ITS#8866 patch to RE24 will not make things worse.
2. The real fix will also fix the disclosure issue.

Ciao, Michael.