Re: Snapshot synchronization, again...

On Tue, Feb 22, 2011 at 8:01 AM, Heikki Linnakangas
<heikki(dot)linnakangas(at)enterprisedb(dot)com> wrote:
> This is hashing, not encryption, there is no key. The point is that even if
> the attacker has the hash value and knows the algorithm, he can not
> construct *another* snapshot that has the same hash.

What good does that do us?

> Yes. It would be good to perform those sanity checks anyway.

I don't think it's good; I think it's absolutely necessary. Otherwise
someone can generate arbitrary garbage, hash it, and feed it to us.
No?

> But even if we don't allow it, there's no harm in sending the whole snapshot
> to the client, anyway. Ie. instead of "1" as the identifier, use the
> snapshot itself. That leaves the door open for allowing it in the future,
> should we choose to do so.

The door is open either way, AFAICS: we could eventually allow:

BEGIN TRANSACTION (SNAPSHOT '1');
and also
BEGIN TRANSACTION (SNAPSHOT '{xmin 123 xmax 456 xids 128 149 201}');

--
Robert Haas
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