Recently, I deployed OpenSSO as a web single sign on service for a number of web servers, one of which was running MediaWiki. I haven’t yet written a SAML2 plugin for MediaWiki, so I am running an OpenSSO web agent for Apache, with the LDAP plugin doing auto-authentication.

After deploying the web agent, MediaWiki started parsing things incorrectly. Wiki-syntax like:

== Test ==
== Test2 ==
=== Test 3 ===

Was being corrupted, and turning into something like:

== Test ==== Test2 ===== Test3 ===

I traced it down to a conflict between the OpenSSO web agent and php-xml (dom.so specifically). I’m not sure exactly what the issue is, but removing the php-xml package from Red Hat Enterprise Linux 5 (RHEL 5) solved the parsing problem. Unfortunately, some MediaWiki extensions, like ImageMap, require php-xml.

I was able to fix the issue in MediaWiki’s configuration by telling the parser to use plain PHP arrays for temporary storage instead of PHP’s DOM. I did this by putting the following into LocalSettings.php:

$wgParserConf = array(
        'class' => 'Parser',
        'preprocessorClass' => 'Preprocessor_Hash',
);

If anyone has an idea on a better way to fix this, I’m all ears. I’d like to not have a nasty workaround like this.

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1. New OpenSSO authentication plugin for MediaWiki
2. Using the LDAP Authentication Plugin for MediaWiki – The Basics (Part 2)
3. Using the LDAP Authentication Plugin for MediaWiki – The Basics (Part 1)
4. Using the LDAP Authentication Plugin for MediaWiki – The Basics (Part 3)
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