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 context.

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

       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 frontend.

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 the Lightweight Directory Access Protocol) project.
       Information about the project can be found at 
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       manual page, see ⟨⟩.  This page was
       obtained from the project's upstream Git repository
       ⟨⟩ on 2023-12-22.
       (At that time, the date of the most recent commit that was found
       in the repository was 2023-12-19.)  If you discover any rendering
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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)