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NAME | SYNOPSIS | DESCRIPTION | CONFIGURATION | MASSAGING | ACCESS RULES | SCENARIOS | EXAMPLES | ACCESS CONTROL | FILES | SEE ALSO | COLOPHON |
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SLAPD-RELAY(5) File Formats Manual SLAPD-RELAY(5)
slapd-relay - relay backend to slapd
ETCDIR/slapd.conf
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 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.
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.
ETCDIR/slapd.conf
default slapd configuration file
slapd.conf(5), slapd-config(5), slapo-rwm(5), slapd(8).
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
⟨http://www.openldap.org/⟩. If you have a bug report for this
manual page, see ⟨http://www.openldap.org/its/⟩. This page was
obtained from the project's upstream Git repository
⟨https://git.openldap.org/openldap/openldap.git⟩ on 2025-08-11.
(At that time, the date of the most recent commit that was found
in the repository was 2025-08-05.) If you discover any rendering
problems in this HTML version of the page, or you believe there is
a better or more up-to-date source for the page, or you have
corrections or improvements to the information in this COLOPHON
(which is not part of the original manual page), send a mail to
[email protected]
OpenLDAP LDVERSION RELEASEDATE SLAPD-RELAY(5)
Pages that refer to this page: slapd.backends(5), slapd-ldap(5), slapd-meta(5), slapo-rwm(5)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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