On Fri, Jan 07, 2022 at 01:46:00PM -0500, Bruce Momjian wrote: > On Sat, Jan 1, 2022 at 11:25:05AM -0600, Justin Pryzby wrote: > > Thanks for working on this. The patch looks to be in good shape - I hope > > more > > people will help to review and test it. I took the liberty of creating a > > new > > CF entry. http://cfbot.cputube.org/daniil-zakhlystov.html > > > > +zpq_should_compress(ZpqStream * zpq, char msg_type, uint32 msg_len) > > +{ > > + return zpq_choose_compressor(zpq, msg_type, msg_len) == -1; > > > > I think this is backwards , and should say != -1 ? > > > > As written, the server GUC libpq_compression defaults to "on", and the > > client > > doesn't request compression. I think the server GUC should default to off. > > I failed to convince Kontantin about this last year. The reason is that 1) > > it's a new feature; 2) with security implications. An admin should need to > > "opt in" to this. I still wonder if this should be controlled by a new > > "TYPE" > > in pg_hba (rather than a GUC); that would make it exclusive of SSL. > > I assume this compression happens before it is encrypted for TLS > transport. Second, compression was removed from TLS because there were > too many ways for HTTP to weaken encryption. I assume the Postgres wire > protocol doesn't have similar exploit possibilities.
It's discussed in last year's thread. The thinking is that there tends to be *fewer* exploitable opportunities between application->DB than between browser->app. But it's still a known concern, and should default to off - as I said. That's also why I wondered if compression should be controlled by pg_hba, rather than a GUC. To require/allow an DBA to opt-in to it for specific hosts. Or to make it exclusive of ssl. We could choose to not suppose that case at all, or (depending on the implement) refuse that combination of layers. -- Justin
