Apache2 reverse proxy issues with OTRS

Question

I have asked this question in OTRS forum but their primary focus is the functionality of OTRS and not really the interaction with an apache proxy.

I have an internal server running OTRS (Perl based support ticket system). I have a reverse proxy in my DMZ that performs proxy and SSL offload for internal web pages/applications. My proxy server is Ubuntu 18 with Apache2. It mostly works except that for OTRS I get weird page errors. It used to not be bad but since update from OTRS 5 to OTRS6 it is so bad that we cannot we https except to log in.

If I use https it throws a message that "OTRS has detected possible network issues" and says to reload the page or wait till the browser establishes connection on it's own. If I wait just a bit I get a new message that states "the connection has been re-established after a temporary connection loss. Due to this elements on this page could have stopped working correctly" it goes on to say that you need to reload the page. But it just keeps cycling through these message in a flapping error.

I also get additional slash marks ( / ) each time I move to a new ticket. Like so: https://myotrs.mydomain.com/otrs////////////index.pl ?

The slash mark addition happens on both http and https through the proxy. It only happens on the OTRS site, not on my others handled by the same proxy.

Here is sample of my proxy vhost file.

<VirtualHost *:443>
ServerName help.mydomain.com
ServerAlias help.mydomain.net
ServerAdmin it@mydomain.com
ErrorLog /var/log/apache2/proxiedhosts-ssl_error.log
  # Possible values include: debug, info, notice, warn, error, crit,
  # alert, emerg.
  LogLevel info
  CustomLog /var/log/apache2/access-ssl.log combined
ProxyRequests off
ProxyPass / http://helpdesk.mydomain.local/
<Location /otrs>
 ProxyPassReverse http://helpdesk.mydomain.local/otrs/
</Location>
<Location /otrs-web>
 ProxyPassReverse http://helpdesk.mydomain.local/otrs-web/
</Location>
# Use mod_proxy_html to rewrite URLs
  SetOutputFilter proxy-html
# commented out
https://help.mydomain.com/otrs/
https://help.mydomain.com/otrs-web/
# Disable compressed communication between Apache and target server
  RequestHeader unset  Accept-Encoding
  #   SSL Engine Switch:
  #   Enable/Disable SSL for this virtual host.
  SSLEngine on
  # Allows the proxying of an SSL connection
  SSLProxyEngine On
  # certificate
  SSLCertificateFile /etc/ssl/certs/help.mydomain.com/help.mydomain.com.crt
  SSLCertificateKeyFile /etc/ssl/private/SHA2_mydomain.key
</VirtualHost>

Answer 1

I have checked out your config file, and i suggest you try to change

<Location /otrs>
     ProxyPassReverse http://helpdesk.mydomain.local/otrs/
</Location>

to

<Location /otrs/>
     ProxyPassReverse http://helpdesk.mydomain.local/otrs/
</Location>

In the original config file, if you browse https://myotrs.mydomain.com/otrs/index.pl you will be redirect to https://myotrs.mydomain.com/otrs//index.pl . And then, if you click the page, you will be redirect to https://myotrs.mydomain.com/otrs///index.pl . Then you are stuck in the circulation.