SLAPD-RELAY(5)							File Formats Manual						    SLAPD-RELAY(5)

NAME

       slapd-relay - relay backend to slapd

SYNOPSIS

       /etc/openldap/slapd.conf

DESCRIPTION

       The  primary purpose of this slapd(8) backend is to map a naming context defined in a database running in the same slapd(8) instance into a
       virtual naming context, with attributeType and objectClass manipulation, if required.  It requires the slapo-rwm(5) overlay.

       This backend and the above mentioned overlay are experimental.

CONFIGURATION

       The following slapd.conf directives apply to the relay backend database.  That is, they must follow a "database relay" line and come before
       any  subsequent	"backend"  or  "database"  lines.   Other database options are described in the slapd.conf(5) manual page; only the suffix
       directive is allowed by the relay backend.

       relay <real naming context>
	      The naming context of the database that is presented under a virtual naming context.  The presence of this  directive  implies  that
	      one specific database, i.e. the one serving the real naming context, will be presented under a virtual naming context.

MASSAGING

       The relay database does not automatically rewrite the naming context of requests and responses.	For this purpose, the slapo-rwm(5) overlay
       must be explicitly instantiated, and configured as appropriate.	Usually, the rwm-suffixmassage directive suffices if only  naming  context
       rewriting is required.

ACCESS RULES

       One important issue is that access rules are based on the identity that issued the operation.  After massaging from the virtual to the real
       naming context, the frontend sees the operation as performed by the identity in	the  real  naming  context.   Moreover,  since	back-relay
       bypasses  the  real  database  frontend	operations  by short-circuiting operations through the internal backend API, the original database
       access rules do not apply but in selected cases, i.e. when the backend itself applies access control.  As a consequence, the  instances	of
       the  relay database must provide own access rules that are consistent with those of the original database, possibly adding further specific
       restrictions.  So, access rules in the relay database must refer to identities in the real naming context.  Examples are  reported  in  the
       EXAMPLES section.

SCENARIOS

       If no relay directive is given, the relay database does not refer to any specific database, but the most appropriate one is looked-up after
       rewriting the request DN for the operation that is being handled.

       This allows to write carefully crafted rewrite rules that cause some of the requests to be directed to one database, and some  to  another;
       e.g.,  authentication can be mapped to one database, and searches to another, or different target databases can be selected based on the DN
       of the request, and so.

       Another possibility is to map the same operation to different databases based on details of the virtual naming context, e.g. groups on  one
       database and persons on another.

EXAMPLES

       To implement a plain virtual naming context mapping that refers to a single database, use

	 database		 relay
	 suffix 		 "dc=virtual,dc=naming,dc=context"
	 relay			 "dc=real,dc=naming,dc=context"
	 overlay		 rwm
	 rwm-suffixmassage	 "dc=real,dc=naming,dc=context"

       To implement a plain virtual naming context mapping that looks up the real naming context for each operation, use

	 database		 relay
	 suffix 		 "dc=virtual,dc=naming,dc=context"
	 overlay		 rwm
	 rwm-suffixmassage	 "dc=real,dc=naming,dc=context"

       This  is  useful, for instance, to relay different databases that share the terminal portion of the naming context (the one that is rewrit-
       ten).

       To implement the old-fashioned suffixalias, e.g. mapping the virtual to the real naming context, but not the results back from the real	to
       the virtual naming context, use

	 database		 relay
	 suffix 		 "dc=virtual,dc=naming,dc=context"
	 relay			 "dc=real,dc=naming,dc=context"
	 overlay		 rwm
	 rwm-rewriteEngine	 on
	 rwm-rewriteContext	 default
	 rwm-rewriteRule	 "dc=virtual,dc=naming,dc=context"
				 "dc=real,dc=naming,dc=context" ":@"
	 rwm-rewriteContext	 searchFilter
	 rwm-rewriteContext	 searchEntryDN
	 rwm-rewriteContext	 searchAttrDN
	 rwm-rewriteContext	 matchedDN

       Note  that  the	slapo-rwm(5)  overlay is instantiated, but the rewrite rules are written explicitly, rather than automatically as with the
       rwm-suffixmassage statement, to map all the virtual to real naming context data flow, but none of the real to virtual.

       Access rules:

	 database		 bdb
	 suffix 		 "dc=example,dc=com"
	 # skip...
	 access to dn.subtree="dc=example,dc=com"
		 by dn.exact="cn=Supervisor,dc=example,dc=com" write
		 by * read

	 database		 relay
	 suffix 		 "o=Example,c=US"
	 relay			 "dc=example,dc=com"
	 overlay		 rwm
	 rwm-suffixmassage	 "dc=example,dc=com"
	 # skip ...
	 access to dn.subtree="o=Example,c=US"
		 by dn.exact="cn=Supervisor,dc=example,dc=com" write
		 by dn.exact="cn=Relay Supervisor,dc=example,dc=com" write
		 by * read

       Note that, in both databases, the identities (the <who> clause) are in the real naming context, i.e.  `dc=example,dc=com', while  the  tar-
       gets (the <what> clause) are in the real and in the virtual naming context, respectively.

ACCESS CONTROL

       The  relay  backend does not honor any of the access control semantics described in slapd.access(5); all access control is delegated to the
       relayed database(s).  Only read (=r) access to the entry pseudo-attribute and to the other attribute values of the entries returned by  the
       search operation is honored, which is performed by the frontend.

FILES

       /etc/openldap/slapd.conf
	      default slapd configuration file

SEE ALSO

       slapd.conf(5), slapd-config(5), slapo-rwm(5), slapd(8).

OpenLDAP 2.4.28 						    2011/11/24							    SLAPD-RELAY(5)