libxslt offers the ability to read and write both files and URLs through
stylesheet commands, thus allowing unprivileged database users to both read
and write data with the privileges of the database server. Disable that
through proper use of libxslt's security options.
Also, remove xslt_process()'s ability to fetch documents and stylesheets
from external files/URLs. While this was a documented "feature", it was
long regarded as a terrible idea. The fix for CVE-2012-3489 broke that
capability, and rather than expend effort on trying to fix it, we're just
going to summarily remove it.
While the ability to write as well as read makes this security hole
considerably worse than CVE-2012-3489, the problem is mitigated by the fact
that xslt_process() is not available unless contrib/xml2 is installed,
and the longstanding warnings about security risks from that should have
discouraged prudent DBAs from installing it in security-exposed databases.
Reported and fixed by Peter Eisentraut.
Security: CVE-2012-3488
This isn't fully tested as yet, in particular I'm not sure that the
"foo--unpackaged--1.0.sql" scripts are OK. But it's time to get some
buildfarm cycles on it.
sepgsql is not converted to an extension, mainly because it seems to
require a very nonstandard installation process.
Dimitri Fontaine and Tom Lane
pairs that can be handled by xslt_process().
There is much else to do here, but this patch seems useful in its own right
for as long as this code survives.
Pavel Stehule, reviewed by Mike Fowler
This involves modifying the module to have a stable ABI, that is, the
xslt_process() function still exists even without libxslt. It throws a
runtime error if called, but doesn't prevent executing the CREATE FUNCTION
call. This is a good thing anyway to simplify cross-version upgrades.
Get rid of the code that attempted to funnel libxml2's memory allocations
into palloc. We already knew from experience with the core xml datatype
that trying to do this is simply not reliable. Unlike the core code, I
did not bother adding a lot of PG_TRY/PG_CATCH logic to try to ensure that
everything is cleaned up on error exit. Hence, we might leak some memory
if one of these functions fails partway through. Given the deprecated
status of this contrib module and the fact that errors partway through
the functions shouldn't be too common, it doesn't seem worth worrying about.
Also fix a separate bug in xpath_table, that it did the wrong things
if given a result tuple descriptor with less than 2 columns. While
such a case isn't very useful in practice, we shouldn't fail or stomp
memory when it occurs.
Add some simple regression tests based on all the reported crash cases
that I have on hand.
This should be back-patched, but let's see if the buildfarm likes it first.
