Re: libpq support for NegotiateProtocolVersion

On 09.11.22 00:08, Jacob Champion wrote:
> On 11/8/22 00:40, Peter Eisentraut wrote:
>> On 02.11.22 20:02, Jacob Champion wrote:
>>> This new code path doesn't go through the message length checks that are
>>> done for the 'R' and 'E' cases, and pqGetNegotiateProtocolVersion3()
>>> doesn't take the message length to know where to stop anyway, so a
>>> misbehaving server can chew up client resources.
>>
>> Fixed in new patch.
>
> pqGetNegotiateProtocolVersion3() is still ignoring the message length,
> though; it won't necessarily stop at the message boundary.

I don't follow. The calls to pqGetInt(), pqGets(), etc. check the
message length. Do you have something else in mind? Can you give an
example or existing code?

>>> I think the documentation on NegotiateProtocolVersion (not introduced in
>>> this patch) is misleading/wrong; it says that the version number sent
>>> back is the "newest minor protocol version supported by the server for
>>> the major protocol version requested by the client" which doesn't seem
>>> to match the actual usage seen here.
>>
>> I don't follow. If libpq sends a protocol version of 3.1, then the
>> server responds by saying it supports only 3.0. What are you seeing?
>
> I see what you've described on my end, too. The sentence I quoted seemed
> to imply that the server should respond with only the minor version (the
> least significant 16 bits). I think it should probably just say "newest
> protocol version" in the docs.

Ok, I see the distinction.