Re: psql with GSS can crash

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?

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