Configuring XRootD Authorization¶
There are several authorization options in XRootD available through the security plugins.
In this document, we will cover the
xrootd-lcmaps security option supported
in the OSG.
On the data nodes, the files will actually be owned by unix user
xrootd (or other daemon user), not as the user
authenticated to, under most circumstances.
XRootD will verify the permissions and authorization based on the user that the security plugin authenticates you
to, but, internally, the data node files will be owned by the
XRootD allows configuring fine-grained file access permissions based on usernames and paths.
This is configured in the authorization file
/etc/xrootd/auth_file on the data server node, which should be writable
only by the xrootd user, optionally readable by others.
/etc/xrootd/auth_file corresponds to the
acc.authdb parameter in your xrootd config.)
Here is an example
# This means that all the users have read access to the datasets, _except_ under /private u * -rl /data/xrootdfs/private /data/xrootdfs rl # Or the following, without a restricted /private dir # u * /data/xrootdfs rl # This means that all the users have full access to their private dirs u = /data/xrootdfs/home/@=/ a # This means that this privileged user can do everything # You need at least one user like that, in order to create the # private dirs for users willing to store their data in the facility u xrootd /data/xrootdfs a # This means that users in group 'biology' can do anything under this path g biology /data/xrootdfs/biology a
Here we assume that your storage path is
This path is relative to the
all.localroot configuration values, if either one is defined in the
xrootd config file.
Specific paths need to be specified before generic paths; e.g., this does not work:
u * rl /data/xrootdfs -rl /data/xrootdfs/private
More generally, each configuration line of the auth file has the following form:
idtype id path privs
|idtype||Type of id. Use
|id||Username (or groupname). Use
|path||The path prefix to be used for matching purposes.
|privs||Letter list of privileges:
For more details or examples on how to use templated user options, see XRootd Authorization Database File.
Ensure the auth file is owned by
xrootd (if you have created file as root), and that it is not writable by others.
[email protected] # chown xrootd:xrootd /etc/xrootd/auth_file [email protected] # chmod 0640 /etc/xrootd/auth_file # or 0644
Enabling xrootd-lcmaps authorization¶
The xrootd-lcmaps security plugin uses the
lcmaps library and the LCMAPS VOMS plugin
to authenticate and authorize users based on X509 certificates and VOMS attributes. Perform the following instructions
on all data nodes:
Follow the instructions for requesting a service certificate, using
xrootdfor both the
<OWNER>, resulting in a certificate and key in
Install and configure the LCMAPS VOMS plugin
xrootd-lcmapsand necessary configuration:
[email protected] # yum install xrootd-lcmaps vo-client
Configure access rights for mapped users by creating and modifying the XRootD authorization file
Modify your XRootD configuration:
Choose the configuration file to edit based on the following table:
If you are running XRootD in... Then modify the following file... Standalone mode
Add the following lines to the configuration that you chose above:
xrootd.seclib /usr/lib64/libXrdSec-4.so sec.protocol /usr/lib64 gsi -certdir:/etc/grid-security/certificates \ -cert:/etc/grid-security/xrd/xrdcert.pem \ -key:/etc/grid-security/xrd/xrdkey.pem -crl:1 \ -authzfun:libXrdLcmaps.so -authzfunparms:--loglevel,0,--policy,authorize_only \ -gmapopt:10 -gmapto:0 acc.authdb /etc/xrootd/auth_file ofs.authorize
Restart the relevant services
To verify the LCMAPS security, run the following commands from a machine with your user certificate/key pair,
Destroy any pre-existing proxies and attempt a copy to a directory (which we will refer to as
<DESTINATION PATH>) on the
<XROOTD HOST>to verify failure:
On the XRootD host, add your DN to /etc/grid-security/grid-mapfile
Add a line to
/etc/xrootd/auth_fileto ensure the mapped user can write to
Restart the xrootd service. (See this section for more information of managing XRootD services.)
Generate your proxy and verify that you can successfully transfer files:
[email protected] $ voms-proxy-init [email protected] $ xrdcp /bin/sh root://<XROOTD HOST>/<DESTINATION PATH> [938.1kB/938.1kB][100%][==================================================][938.1kB/s]
If your transfer does not succeed, run the previous command with
--debug 2for more information.