To use AuthExternal in your apache configuration you need the authnz-external mod. Install on Ubuntu/Debian with:
apt-get install libapache2-mod-authnz-external
cd /usr/local/bin/
git clone https://github.com/Degola/jira-authentication-apache-mod-authnz-external
cd jira-authentication-apache-mod-authnz-external
composer update
Example HTTP Configuration:
<Location />
AuthType Basic
AuthName "Restricted"
AuthBasicProvider external
AuthExternal jira-backend
require valid-user
</Location>
AddExternalAuth jira-backend "/usr/local/bin/jira-auth/bin/jira-auth.php https://your-jira-url.com/jira/ your-logstash-server.com:1234 i-have-access-group"
SetExternalAuthMethod jira-backend pipe
i-have-access-group is the corresponding jira group which has to be assigned to the user who tries to login.