Selection of authorization plugins for xrootd4j that allows dCache to be used as an ALICE storage element.

dCache is a distributed storage system frequently used in the Worldwide LHC Computing Grid, high energy physics, photon sciences, and other communities.

ALICE is one of the LHC experiments. ALICE heavily relies on the xrootd data access protocol. The xrootd protocol is supported by dCache out of the box and implemented in the xrootd4j library.

ALICE relies on a proprietary authorization scheme using cryptographically signed authorization tokens. This project provides plugins for dCache 2.0 and newer. The plugins implement various versions of the ALICE authorization scheme. Using the plugins, dCache can be used as an ALICE storage element.

The provider is compiled with:

mvn package

Untar the tarball:

cd /tmp
tar xzf xrootd4j-authz-plugin-alice-VERSION.tar.gz

Add the directory in which the tarball was unpacked (not the directory contained in the tarball) to the plugin search path:

java -Dlog=debug -DxrootdAuthzKeystore=/etc/dcache/xrootd/keystore \
     -jar xrootd4j-standalone-1.0.0-jar-with-dependencies.jar \
     --plugins /tmp/ \
     --authz alice-token-1

The plugin ships with dCache 2.1 and can be enabled by adding the following line to dcache.conf:

xrootdAuthzPlugin=alice-token-1

We are currently considering to backport xrootd4j to dCache 1.9.12 and will include the Alice plugin.

This is currently the only plugin included, although more plugins will be added.

The plugin is nearly identical to the token authorization plugin used in earlier releases of dCache. The only difference is that stat and statx optionally accept an authorization token. The original plugin ignored the authorization token even if present.

To identify the keystore, define the following parameter (in dcache.conf for dCache or on the command line of xrootd4j):

xrootdAuthzKeystore=/etc/dcache/keystore

A possible keystore file is:

KEY VO:*   PRIVKEY:/etc/dcache/privkey.der  PUBKEY:/etc/dcache/pubkey.der

With privkey.der and pubkey.der being the ALICE xrootd keypair.

The code was originally written by Martin Radicke and sponsored by DESY. It has since been maintained by Thomas Zangerl and Gerd Behrmann, both sponsored by NDGF.