XProc to access XML data from FTP (with authentication)

Question

My goal is to access an XML document sitting on an FTP server via an XProc. This particular FTP server requires authentication.

I am using the latest version of Calabash (1.1.6-96) on Java 8.

The following XProc works perfectly when authentication is not required:

<p:declare-step xmlns:p="http://www.w3.org/ns/xproc"
xmlns:c="http://www.w3.org/ns/xproc-step" version="1.0">
    <p:input port="source">
    <p:document href="ftp://ftp.hq.nasa.gov/index.html"/>
    </p:input>
    <p:output port="result"/>
    <p:identity/>
</p:declare-step>

But if you try to access an FTP server that requires authentication:

<p:declare-step xmlns:p="http://www.w3.org/ns/xproc"
xmlns:c="http://www.w3.org/ns/xproc-step" version="1.0">
    <p:input port="source">
        <p:document href="ftp://user:passwordd@ftp.example.org/example.xml"/>
    </p:input>
    <p:output port="result"/>
    <p:identity/>
 </p:declare-step>

Calabash will return the error:

ERROR: It is a dynamic error if the resource referenced by a p:document element does not exist, cannot be accessed, or is not a well-formed XML document.

Indicating that it cannot access the document.

Strangely, I have an older install of Oxygen (16.0) which came with an older version of Calabash (1.0.*) and the second XProc, which uses authentication, works perfectly fine. So, either something has changed within Calabash, or there is something else related to the older Oxygen/Calabash configuration that just makes it work.

I'm also open to alternative methods for accessing this file. I've already tried swapping out <p:document> for <p:http-request>, but this didn't pan out.