Debian's OpenJDK 11 as supplied under Debian 10 "buster"
Other Java distributions that are substantially identical or meant to be fully compatible with OpenJDK 11 are of course likely to work, but are officially regarded as unsupported to limit the range of environments we need to be able to reproduce problems under to a manageable set.
Other platform/version requirements
A servlet container implementing Servlet API 3.1 is required. For example:
Jetty 9.4 or later (but not Jetty 11)
Tomcat 9 or later (while some older versions of Tomcat are nominally suitable, they have not been tested and have been obsoleted in any case)
We also do not officially support any "packaged" containers provided by OS vendors. We do not test on these containers so we cannot assess what changes may have been made by the packaging process, and they frequently contain unwarranted and ill-considered changes from the upstream software.
The recommended container implementation is Jetty and all development and most testing time by the core project team is confined to the Jetty platform. At present, Jetty 9.4 is recommended.
There are no specific requirements regarding Operating Systems, but in practice this is inherently limited by the Java distributions supported, as noted above.
Unusable Platforms and Versions
The following common configurations, and versions often in use with prior IdP versions, are specifically NOT usable:
Java version 10 or earlier
Tomcat 7 or earlier
Jetty 9.3 or earlier
Jetty 11 or later
User Agent Assumptions
There are no specific requirements regarding Browsers, but we test on only relatively recent, mainstream software, and certain features like HTML Local Storage assume standards-compliant software.
The IdP requires the use of first-party cookies and is not designed to function without them.
The IdP does not require third-party cookies to be enabled and does not support the embedding of the supported user interfaces in frames hosted by a third party. While this may work, it is not guaranteed to work, and we ship with a configuration that explicitly blocks the use of frames via response headers. The blocking behavior is configurable and can be disabled, though this is not recommended for newer deployments.
Alternative JAXP Implementations
While we support only the Oracle and OpenJDK Java implementations and the JAXP XML Parser implementation included with them, it is possible in principle to use alternatives. They will not in general be likely to work out of the box (or at least not safely) because our default configuration includes settings to secure the XML parser that are built into the Java reference implementation. We strongly recommend against use of an alternative parser, but there are hooks built into the software to allow for it.
An alternative XML parser configuration can be established by defining a custom bean of type ParserPool, and providing its name via the idp.xml.parserPool property. This is typically done through reuse of the BasicParserPool class by copying the system-provided bean (see shibboleth.DefaultParserPool in this system file) into a new bean in conf/global.xml and adjusting the default attributes and features to match the JAXP implementation in use. Any appropriate security measures and protections required are the deployer's responsibility, and there is no guarantee of interoperability.