FS#1048 [LDAP] backslashes in DN cause ldap error

When, after having authenticated, and after having retrieved the user details, dokuwiki starts to look for the groups the user is member of, it does this search:

$conf['auth']['ldap']['groupfilter'] = '(&(objectClass=group)(member=%{dn}))'

Here, the LDAP server is a Microsoft Active directory/Exchange server, the DNs are like:

dn: CN=Chazelas\, Stephane,OU=...

Note the "" to escape the ",".

I find that unless I double the backslash in the groupfilter (see patch attached), I am not able to retrieve that list of groups. Instead I get an LDAP error with something like a "filter parse error".

dokuwiki is running on Linux debian unstable.

apache2 2.2.3-3.2 Next generation, scalable, extendable web server
dokuwiki 0.0.20061106-1 a standards compliant simple to use wiki
libapache2-mod-php5 5.2.0-8 server-side, HTML-embedded scripting language (apache 2 module)
libldap2 2.1.30-13.2 OpenLDAP libraries
php5-ldap 5.2.0-8 LDAP module for php5

doku-ldap.diff text/x-patch

FS#1048 [LDAP] backslashes in DN cause ldap error

ACL & Authentication