omero admin start: add warning for deprecated TLS protocols

The message should be raised either if omero.glacier2.IceSSL.Protocols
is unset or if TLS 1.0 or 1.1 are found in the list of allowed protocols

src/omero/plugins/admin.py

@@ -800,6 +800,21 @@ def startasync(self, args, config):
                 "sysadmins/server-performance.html?highlight=poolsize\n"
                 "for more information.")
 
+        ssl_protocols = config.get("omero.glacier2.IceSSL.Protocols", "")
+        # TLS 1.0 and 1.1 were deprecated in https://datatracker.ietf.org/doc/html/rfc8996
+        # Both protocols are included in the default value of IceSSL.Protocols
+        # https://doc.zeroc.com/ice/3.6/property-reference/icessl#id-.IceSSL.*v3.6-IceSSL.Protocols
+        has_deprecated_tls = (
+            ssl_protocols == "" or
+            "TLS1_0" in ssl_protocols or
+            "TLS1_1" in ssl_protocols
+        )
+        if has_deprecated_tls:
+            self.ctx.out(
+                "WARNING: Your server is configured to allow a deprecated TLS protocol.\n"
+                "\nPlease refer to https://omero.readthedocs.io/en/stable/sysadmins/server-upgrade.html"
+                " for instructions on how to upgrade the protocols.")
+
         self._initDir()
         # Do a check to see if we've started before.
         self._regdata()