User:Dennisvd@nikhef.nl/lijmwijzer

The Administrator's guide to grid security middleware

Odds and ends

See if any of the following statements apply.

I would like to do policy management, user mapping and user banning all from one place

The default choice is to set up Argus[1], and configure your resources to use it (see below).

I use dynamic secondary group mappings which require LDAP updates

In this case, you need to use the LDAP enforcement plugin for LCMAPS. This cannot be used in conjunction with Argus; use SCAS as the default alternative.

My cluster is set up to do local mappings to match users to job slots

This is a special case, which can be handled by setting up LCMAPS without a central authorization service (i.e. node-local).

I'm using 3rd party plugins for LCMAPS

We can't say in general if a plugin will or will not work with either Argus or SCAS in this case. You should try Argus first, SCAS next, and node-local setups finally.

I've tried Argus and it didn't work; now what?

Open a support ticket in GGUS[2] for Argus and get it fixed. In the meantime, try to use SCAS as an alternative.

I don't want/need central policy management, mapping or banning

You should set up LCMAPS independently per resource, possibly with a shared NFS gridmapdir to keep consistency between mappings.

This guide will help you choose and configure security middleware components to suite the local setup at your site. Warning: this guide will not explain how to set up site security in general.

The following text applies to sites that are part of the EGEE grid infrastructure[3]. For other Grids, a separate guide will be provided.

Old versus New

Step 2: Resource configuration

Depending on the selections in step 1, apply the detailed configurations below.

The configurations are marked with symbols to indicate how well they are supported:

• Configurations with this marker are found in production systems all over, and are proven to work well.
• 
• 

Central account mapping

Managing the (pool) user and group account mappings on a site is typically done centrally. If for some reason a central authorization service is not chosen, the gridmapdir and/or groupmapdir could be shared (with NFS) among all services where mappings are performed, for consistency.

Node-local mapping

In special cases the scope of the account mappings is kept local to a node; these use-cases are typically found when users are mapped to a job slot on a worker node. Node local mapping can be mixed with centralized mapping, for instance when using secondary group ids from the central group mapping.

Special Cases

The following items should be considered before a final choice can be made.

LDAP enforcement

The LCMAPS plugin for LDAP enforcement is used for sites that have dynamic mappings to users and groups, which requires a modification of the LDAP database every time a (new) mapping is done. Zie elders. Applies to: WN, CE.

This plugin will not work together with the ARGUS framework.

LDAP enforcement with SCAS

(This situation is supposed to work, but not found in production as such.)

On the WN:

get_account_on_wn:
verify_proxy -> scas_client
scas_client -> ldap_enf
ldap_enf -> posix_enf

On the CE:

get_account_on_ce:
scas_client -> ldap_enf
ldap_enf -> posix_enf

On SCAS:

get_account_on_scas:
voms_pool_group -> voms_local_group | voms_local_group
voms_local_group -> voms_pool_account

LDAP enforcement with node-local mapping

On the WN:

get_account_on_wn:
verify_proxy -> voms_pool_group | voms_local_group
voms_pool_group -> voms_local_group
voms_local_group -> voms_pool_account
voms_pool_account -> ldap_enf
ldap_enf -> posix_enf

On the CE:

get_account_on_ce:
voms_pool_group -> voms_local_group | voms_local_group
voms_local_group -> voms_pool_account
voms_pool_account -> ldap_enf
ldap_enf -> posix_enf

AFS integration

If your site makes use of AFS for file access (e.g. AFS home directories that require AFS tokens) then you need the AFS enforcement plugin. Applies to: CE, WN.

using an ARGUS backend

On the WN:

get_account_on_wn:
verify_proxy -> pepc
pepc -> afs_enf
afs_enf -> posix_enf

On the CE:

get_account_on_ce:
pepc -> afs_enf
afs_enf -> posix_enf

using a SCAS backend

On the WN:

get_account_on_wn:
verify_proxy -> scas_client
scas_client -> afs_enf
afs_enf -> posix_enf

On the CE:

get_account_on_ce:
scas_client -> afs_enf
afs_enf -> posix_enf

On SCAS:

get_account_on_scas:
voms_local_group -> voms_pool_account

AFS enforcement with node-local mapping

This case is used when there is no centrally arranged authorization; the gridmapdir should be shared (e.g. through NFS) between services for consistent mappings.

On the WN:

get_account_on_wn:
verify_proxy -> voms_local_group
voms_local_group -> voms_pool_account
voms_pool_account -> afs_enf
afs_enf -> posix_enf

On the CE:

get_account_on_ce:
voms_local_group -> voms_pool_account
voms_pool_account -> afs_enf
afs_enf -> posix_enf

Third party plugins

Some sites use LCMAPS plugins not provided with the base LCMAPS software; the functioning and side-effects of such plugins is specific to the site and the implementation. In general, it cannot be determined a priori if a plugin will or will not work with either ARGUS or SCAS. YMMV.

Service types

Compute Element

CREAM CE

There are two services that independently use LCMAPS on a CREAM CE: gLExec and gridftpd. It is vital that mappings for both are consistent, otherwise e.g. proxies and sandboxes cannot be read. Differences between the configuration for gLExec and the gridftpd are allowed only if the flow of the plugin execution and the initialization parameters of the plugins result in a consistent mapping.

Examples:

gridftpd:

withvoms:
vomslocalgroup -> vomslocalaccount
vomslocalaccount -> posix_enf | vomspoolaccount
vomspoolaccount -> posix_enf

standard:
localaccount -> posix_enf | poolaccount
poolaccount -> posix_enf

gLExec:

withvoms:
verify_proxy -> vomslocalgroup
vomslocalgroup -> vomslocalaccount
vomslocalaccount -> posix_enf | vomspoolaccount
vomspoolaccount -> posix_enf

standard:
verify_proxy -> localaccount
localaccount -> posix_enf | poolaccount
poolaccount -> posix_enf