Re: psql with GSS can crash

Magnus Hagander píše v po 01. 03. 2010 v 16:55 +0100:
> 2010/3/1 Zdenek Kotala <Zdenek(dot)Kotala(at)sun(dot)com>:
> > Magnus Hagander píše v čt 25. 02. 2010 v 15:17 +0100:
> >> On Thu, Feb 25, 2010 at 15:04, Zdenek Kotala <Zdenek(dot)Kotala(at)sun(dot)com> wrote:
> >> > Hi all,
> >> >
> >> > I got following stack:
> >> >
> >> > fffffd7ffed14b70 strlen () + 40
> >> > fffffd7ffed71665 snprintf () + e5
> >> > fffffd7fff36d088 pg_GSS_startup () + 88
> >> > fffffd7fff36d43a pg_fe_sendauth () + 15a
> >> > fffffd7fff36e557 PQconnectPoll () + 3b7
> >> > fffffd7fff36e152 connectDBComplete () + a2
> >> > fffffd7fff36dc32 PQsetdbLogin () + 1b2
> >> > 000000000041e96d main () + 30d
> >> > 000000000041302c ???????? ()
> >> >
> >> > It seems that connection is not fully configured and krbsrvname or pghost is
> >> > not filled. Following code in fe-auth.c pg_GSS_startup() causes a crash:
> >> >
> >> > 440 maxlen = NI_MAXHOST + strlen(conn->krbsrvname) + 2;
> >> > 441 temp_gbuf.value = (char *) malloc(maxlen);
> >> > 442 snprintf(temp_gbuf.value, maxlen, "%s(at)%s",
> >> > 443 conn->krbsrvname, conn->pghost);
> >> > 444 temp_gbuf.length = strlen(temp_gbuf.value);
> >> >
> >> > And following code in fe-connect.c fillPGconn() fill NULL value.
> >> >
> >> > 571 tmp = conninfo_getval(connOptions, "krbsrvname");
> >> > 572 conn->krbsrvname = tmp ? strdup(tmp) : NULL;
> >> >
> >> > I think that pg_GSS_startup should sanity the input.
> >>
> >> How did you get NULL in there? :-)
> >> There's a default set for that one that's PG_KRB_SRVNAM, so it really
> >> should never come out as NULL, I think...
> >
> > Yeah, you are right. conn->krbsrvname is "postgres" and conn->pghost is
> > null
>
> Ah, good. We should defentd against that then.
>
>
> >> As for pghost, that certainly seems to be a bug. We check that one in
> >> krb5 and SSPI, but for some reason we seem to be missing it in GSSAPI.
> >
> > Yes. The check should be in GSSAPI too.
> >
> > However what I see in pg_hba.conf is following line:
> >
> > local all all gss
> >
> > Gss is used on local unix socket which probably cause a problem that
> > conn->pghost is not filled when psql tries to connect.
>
> So there are really two errors - because we should disallow that.
>
> See attached patch - can you confirm it removes the crash with just
> the client side applied, and then that it properly rejects GSS with
> the server side applied as well?

I tested it, but I cannot reproduce crash because I cannot setup illegal
combination now ;-). I think it is OK.

Thanks Zdenek