Fix Shibboleth back-channel logout for DB sessions

Given a Moodle instance with: $CFG->dbsessions enabled and working; the shibboleth authentication module enabled; a user successfully logged in with shibboleth Find that user's Shibboleth Session ID (from the browser using console to inspect the headers). It can look like "_shibsession_64656661756c7468747470733a2f2f6c6f63616c686f73742f70722f73686962626f6c657468=_47d2e8208c3d89b8bc3ff5dd854dc681" the "_47d2e8208c3d89b8bc3ff5dd854dc681" is what you want. Create a test.sh file in your wwwroot and add the following (make sure to replace HOST and SESSIONID - #!/bin/sh HOST=dev.moodle.net URL=https: //${HOST}/auth/shibboleth/logout.php SESSIONID=$ 1   tmp=`mktemp` cat <<EOF > $tmp <s:Envelope xmlns:s= "http://schemas.xmlsoap.org/soap/envelope/" >   <s:Body>     <LogoutNotification xmlns= "urn:mace:shibboleth:2.0:sp:notify" type= "global" >       <SessionID>$SESSIONID</SessionID>     </LogoutNotification>   </s:Body> </s:Envelope> EOF   curl -X POST -H "Content-Type: text/xml" --data-binary @$tmp $URL Run the bash script. Refresh the page, the user should be logged out.