slapd-relay(5) — Linux manual page


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

NAME         top

       slapd-relay - relay backend to slapd

SYNOPSIS         top


DESCRIPTION         top

       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

MASSAGING         top

       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         top

       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         top

       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

       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.

EXAMPLES         top

       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

       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                mdb
         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, respectively.

ACCESS CONTROL         top

       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

FILES         top

              default slapd configuration file

SEE ALSO         top

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

COLOPHON         top

       This page is part of the OpenLDAP (an open source implementation of
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OpenLDAP LDVERSION               RELEASEDATE                  SLAPD-RELAY(5)

Pages that refer to this page: slapd.backends(5)slapd-ldap(5)slapd-meta(5)slapo-rwm(5)