Segfault in Ruby Ferret query parser

Whilst working with the Ruby text search engine library Ferret, I came across a segfault in the query parser. It had already been reported and fixed, but I realised it can lead to a denial of service.

If you use Ferret anywhere that allows users to execute queries, those users can crash the Ruby process with a specially crafted query.  This was quite serious for a number of my sites (not to mention slowing development of a current app) so I applied the fix to the released 0.11.4 source and repackaged it as 0.11.4.1.

Obviously this isn’t in any way official, but it works for me and I’m sharing here for anyone else affected. Gem, tgz and zip here and just the patch available here (derived from the author’s changeset to trunk).

The patch is against the release source, as the subversion repository seems to be down atm (I got the changeset from the web bases subversion viewer).

Get upgrading!