Re: pg_cryptohash_final possible out-of-bounds access (per Coverity)

On Wed, Feb 10, 2021 at 09:14:46AM -0300, Ranier Vilela wrote:
> It is necessary to correct the interfaces. To caller, inform the size of
> the buffer it created.

Well, Coverity likes nannyism, so each one of its reports is to take
with a pinch of salt, so there is no point to change something that
does not make sense just to please a static analyzer. The context
of the code matters.

Now, the patch you sent has no need to be that complicated, and it
partially works while not actually solving at all the problem you are
trying to solve (nothing done for MD5 or OpenSSL). Attached is an
example of what I finish with while poking at this issue. There is IMO
no point to touch the internals of SCRAM that all rely on the same
digest lengths for the proof generation with SHA256.

> I think it should be error-out, because the buffer can be malloc.

I don't understand what you mean here, but cryptohash[_openssl].c
should not issue an error directly, just return a status code that the
caller can consume to generate an error.
--
Michael