Re: psql with GSS can crash

2010/3/7 Zdenek Kotala <Zdenek(dot)Kotala(at)sun(dot)com>:
> 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.

Ok, thanks for testing. I've been unable to break it in my testing as
well so - applied, and back-patched.

--
Magnus Hagander
Me: http://www.hagander.net/
Work: http://www.redpill-linpro.com/