To: "Tom Lane" <tgl@sss.pgh.pa.us>
Cc: <pgsql-hackers@postgreSQL.org>
Subject: Re: Should creating a new base type require superuser status?
In-Reply-To: <19715.1217447413@sss.pgh.pa.us> (Tom Lane's message of "Wed\,
	30 Jul 2008 15\:50\:13 -0400")
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References: <19715.1217447413@sss.pgh.pa.us>
From: Gregory Stark <stark@enterprisedb.com>
Organization: EnterpriseDB
Date: Wed, 30 Jul 2008 22:19:36 +0100
Message-ID: <87sktrgjdj.fsf@oxford.xeocode.com>
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"Tom Lane" <tgl@sss.pgh.pa.us> writes:

> If you're not clear on why CREATE TYPE in the hands of a bad guy is
> dangerous, here are a couple of reasons:
>
> * By specifying type representation details (len/byval/align) that are
> different from what the type's functions expect, you could trivially
> crash the backend, and less trivially use a pass-by-reference I/O
> function to read out the contents of backend memory.

I know when I was first starting out it was a big source of frustration that
you have to get those arguments right.. Until I figured out what they all
meant and how to use them I was constantly crashing the server.

It seems to me we should be able to do better. To have some kind of struct in
the C code associated with the input/output functions from which the create
type command picks up these parameters.

As a consequence we could perhaps aim to make creating new types safe rather
than just deal with the fact that it's not safe currently? It would be nice if
non-superusers could create types which used an existing set of input/output
functions but defined new semantics.

> * The just-added ability to specify a new type's type category and
> "preferred" status could allow subverting the behavior of existing
> queries that expect ambiguous operators to be resolved in a particular
> way.  A new preferred type could "capture" such queries and thereby
> provide a trojan-horse vector for executing functions as some other
> user.

Would it be enough to only require super-user to create a preferred type?

-- 
  Gregory Stark
  EnterpriseDB          http://www.enterprisedb.com
  Ask me about EnterpriseDB's Slony Replication support!