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



NAME
       slapd-relay - relay backend to slapd

SYNOPSIS
       /etc/ldap/slapd.conf

DESCRIPTION
       The primary purpose of this slapd(8) backend is to map a naming context defined in a data‐
       base running in the same slapd(8) instance into a virtual naming context, with  attribute‐
       Type 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  con‐
              text.   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  con‐
              text.


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  opera‐
       tion.   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 data‐
       base, 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 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, 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/ldap/slapd.conf
              default slapd configuration file

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



OpenLDAP                                    2014/09/20                             SLAPD-RELAY(5)