SLAPD-RELAY(5) SLAPD-RELAY(5)
NAME
slapd-relay - relay backend to slapd
SYNOPSIS
/etc/openldap/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 rwm 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 required by the
relay backend.
relay <real naming context> [massage]
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. This directive automati-cally automatically
cally instantiates the rwm overlay. If the optional massage keyword is present, the suffix
massaging is automatically configured as well; otherwise, specific massaging instructions are
required by means of the rewrite directives described in slapo-rwm(5).
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 thru the internal backend API, the original data-base database
base 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 han-dled. handled.
dled.
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 vir-tual virtual
tual naming context, e.g. groups on one database and persons on another.
Caveats
The rwm overlay is experimental.
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" massage
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
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"
rewriteEngine on
rewriteContext default
rewriteRule "dc=virtual,dc=naming,dc=context"
"dc=real,dc=naming,dc=context" ":@"
rewriteContext searchFilter
rewriteContext searchEntryDN
rewriteContext searchAttrDN
rewriteContext matchedDN
Note that the virtual database is bound to a single real database, so the rwm overlay is automati-cally automatically
cally instantiated, but the rewrite rules are written explicitly to map all the virtual to real nam-ing naming
ing 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" massage
# 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/openldap/slapd.conf
default slapd configuration file
SEE ALSO
slapd.conf(5), slapo-rwm(5), slapd(8).
OpenLDAP 2.3.27 2006/08/19 SLAPD-RELAY(5)
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