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

       slapd-relay - relay backend to slapd


       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.

       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.

       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.

       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.

       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 one 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.

       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 rewritten).

       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 targets
       (the <what> clause) are in the real and in the virtual naming context,

       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.

              default slapd configuration file

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

OpenLDAP 2.4.48                   2019/07/24                    SLAPD-RELAY(5)