Provided by: slapd_2.6.7+dfsg-1~exp1ubuntu8.2_amd64 
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 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.
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 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
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 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
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.
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 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
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 2.6.7+dfsg-1~exp1ubuntu8.2 2024/01/29 SLAPD-RELAY(5)