https://github.com/picketlink/picketlink/blob/master/modules/federation/src/main/java/org/picketlink/identity/federation/web/util/PostBindingUtil.java#L145

is setting the content length to the response body length but at

https://github.com/picketlink/picketlink/blob/master/modules/federation/src/main/java/org/picketlink/identity/federation/web/util/PostBindingUtil.java#L147

the println method is used to write the body causing an extra newline character to be written and causing an outputstream closed exception on Jetty.