Re: pgcrypto decrypt_iv() issue

On 01/27/2012 07:06 PM, Marko Kreen wrote:
> On Fri, Jan 27, 2012 at 8:00 PM, Magnus Hagander <magnus@hagander.net> wrote:
>> On Fri, Jan 27, 2012 at 18:54, Marko Kreen <markokr@gmail.com> wrote:
>>> On Fri, Jan 27, 2012 at 7:34 PM, Stefan Kaltenbrunner
>>> <stefan@kaltenbrunner.cc> wrote:
>>>> On 01/27/2012 04:20 PM, Marko Kreen wrote:
>>>>> On Fri, Jan 27, 2012 at 01:37:11AM -0500, Tom Lane wrote:
>>>>> Yeah, it should be fixed.  But note that "random data" is part of
>>>>> decrypt() spec - the validation it can do is a joke.
>>>>>
>>>>> Its more important to do proper checks in encrypt() to avoid invalid
>>>>> stored data, but there the recommended modes (CBC, CFB) can work
>>>>> with any length data, so even there the impact is low.
>>>>
>>>> I agree - but in my case the input to those functions is actually coming
>>>> from external untrusted systems - so if the data is (completely) invalid
>>>> really want to get a proper error message instead of random memory content.
>>>
>>> You *will* get random memory content.  If your app is exploitable with
>>> invalid data, you *will* get exploited.  The decrypt() checks are
>>> more for developer convenience than anything more serious.
>>
>> Hold on. I hope there's some misunderstanding here.
>>
>> I hope you are you saying that feeding random data to the decrypt
>> functions should be expected to return random data out of previously
>> free()d areas? Surely you're not?
>>
>> Obviouly, if you send in invalid data or an invalid key, it will
>> decrypt into incorrect data, that goes without saying. But it should
>> still be the same block size and not contain random unrelated memory
>> blocks, shouldn' it?
>
> Yes, it should not contain unrelated data.

hmm - see the last example I had in my original report - not sure i
consider the path to pgcrypto.so "related" data and I most definitly do
not expect to get that back from sending invalid data to the database...


Stefan