On installing an Ubuntu 16.04 desktop from scratch and putting Citrix Receiver on it, I found I couldn’t connect to one of the servers that I need to for work. The strange error suggested that the Citrix client doesn’t trust the VeriSign Class 3 Public Primary Certification Authority – G5.
This seemed confusing at first – I have the CA certificate in /usr/share/ca-certificates/mozilla. A quick look at where Citrix Receiver installed itself quickly found what was going on.
Citrix Receiver only has a handful of CA certificates installed in /opt/Citrix/ICAClient/keystore/cacerts, so if you’re connecting to a server with an SSL certificate other than the dozen or so in here, simply copy the .crt or .pem file and you’re sorted.