Our certificates are issued by Comodo, and the Linux Citrix client didn't support the root server for some reason.
- I used Firefox to view the certificate by clicking on the blue part at the start of the URL.
- Click 'More Information'
- Click 'View certificate'
- Click 'Details'
- Click the Root Certificate at the top of the heirarchy
- Click 'Export'
- Save the certificate as type 'X.509 Certificate DER'
- Save the certificate as 'RootCAName.crt' (Replace RootCAName with actual name)
- Copy the certificate to /opt/Citrix/ICAClient/keystore/cacerts.
I have read that you can copy the CACerts from Firefox, but I haven't tried that.
Thanks to http://www.itswapshop.com/tutorial/how-install-citrix-receiver-linux-120-opensuse-121 for the pointers.