public inbox for [email protected]  

help / color / mirror / Atom feed

From: Tom Lane <[email protected]>
To: [email protected]
Subject: Should creating a new base type require superuser status?
Date: Wed, 30 Jul 2008 15:50:13 -0400
Message-ID: <[email protected]> (raw)

Currently, you're allowed to create a new base type if you own the I/O
functions for it.  That effectively restricts the command to superusers
anyway, since there's presently no way for a non-superuser to create
a function that would have the required signature.  However that's a
fairly indirect protection against letting a dangerous command be
executed by malicious users; and it would fail given such apparently
innocent-looking changes as allowing PL functions to take or return
cstring.  I wonder whether we shouldn't just restrict the command to
superusers explicitly, and thus affirmatively prevent possible future
security holes.

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.

* 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.

There might be some other attacks I've not thought of.

Comments?

			regards, tom lane

view thread (21+ messages)  latest in thread

reply

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Reply to all the recipients using the --to and --cc options:
  reply via email

  To: [email protected]
  Cc: [email protected], [email protected]
  Subject: Re: Should creating a new base type require superuser status?
  In-Reply-To: <[email protected]>

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

This inbox is served by agora; see mirroring instructions
for how to clone and mirror all data and code used for this inbox