Hi Tazky,
Based on the error in the logs, it seems you do not have TLS/SSL configured on your Mattermost Server.
“http_code”:302,“err_details”:“err=error validating response: unable to decrypt encrypted assertion: cannot decrypt, error retrieving private key: decryption tls. Certificate has no public certs attached
For configuring SAML, you will need to configure TLS/SSL on the Mattermost Server.
For SAML config, the authorization server MUST require the use of TLS … The redirection endpoint SHOULD require the use of TLS … Access token credentials MUST only be transmitted using TLS.
Next Steps:
- You could follow this link to install NGINX and configure TLS/SSL How To Create a Self-Signed SSL Certificate for Nginx in Ubuntu 18.04 | DigitalOcean. You can skip Step 1: Create the SSL Certificate because you have already created the certificate mattermost-x509.crt & mattermost-x509.key.
- Configure TLS/SSL on Mattermost server using this link Redirect