NAME
slapo-chain - chain overlay to slapd
SYNOPSIS
/etc/ldap/slapd.conf
DESCRIPTION
The chain overlay to slapd(8) allows automatic referral chasing. Any
time a referral is returned (except for bind operations), it is chased
by using an instance of the ldap backend. If operations are performed
with an identity (i.e. after a bind), that identity can be asserted
while chasing the referrals by means of the identity assertion feature
of back-ldap (see slapd-ldap(5) for details), which is essentially
based on the proxied authorization control [RFC 4370]. Referral
chasing can be controlled by the client by issuing the chaining control
(see draft-sermersheim-ldap-chaining for details.)
The config directives that are specific to the chain overlay are
prefixed by chain-, to avoid potential conflicts with directives
specific to the underlying database or to other stacked overlays.
There are very few chain overlay specific directives; however,
directives related to the instances of the ldap backend that may be
implicitly instantiated by the overlay may assume a special meaning
when used in conjunction with this overlay. They are described in
slapd-ldap(5), and they also need to be prefixed by chain-.
Note: this overlay is built into the ldap backend; it is not a separate
module.
overlay chain
This directive adds the chain overlay to the current backend.
The chain overlay may be used with any backend, but it is mainly
intended for use with local storage backends that may return
referrals. It is useless in conjunction with the slapd-ldap and
slapd-meta backends because they already exploit the libldap
specific referral chase feature. [Note: this may change in the
future, as the ldap(5) and meta(5) backends might no longer
chase referrals on their own.]
chain-cache-uri {FALSE|true}
This directive instructs the chain overlay to cache connections
to URIs parsed out of referrals that are not predefined, to be
reused for later chaining. These URIs inherit the properties
configured for the underlying slapd-ldap(5) before any
occurrence of the chain-uri directive; basically, they are
chained anonymously.
chain-chaining [resolve=<r>] [continuation=<c>] [critical]
This directive enables the chaining control (see draft-
sermersheim-ldap-chaining for details) with the desired resolve
and continuation behaviors and criticality. The resolve
parameter refers to the behavior while discovering a resource,
namely when accessing the object indicated by the request DN;
the continuation parameter refers to the behavior while handling
intermediate responses, which is mostly significant for the
search operation, but may affect extended operations that return
intermediate responses. The values r and c can be any of
chainingPreferred, chainingRequired, referralsPreferred,
referralsRequired. If the critical flag affects the control
criticality if provided. [This control is experimental and its
support may change in the future.]
chain-max-depth <n>
In case a referral is returned during referral chasing, further
chasing occurs at most <n> levels deep. Set to 1 (the default)
to disable further referral chasing.
chain-return-error {FALSE|true}
In case referral chasing fails, the real error is returned
instead of the original referral. In case multiple referral
URIs are present, only the first error is returned. This
behavior may not be always appropriate nor desirable, since
failures in referral chasing might be better resolved by the
client (e.g. when caused by distributed authentication issues).
chain-uri <ldapuri>
This directive instantiates a new underlying ldap database and
instructs it about which URI to contact to chase referrals. As
opposed to what stated in slapd-ldap(5), only one URI can appear
after this directive; all subsequent slapd-ldap(5) directives
prefixed by chain- refer to this specific instance of a remote
server.
Directives for configuring the underlying ldap database may also be
required, as shown in this example:
overlay chain
chain-rebind-as-user FALSE
chain-uri "ldap://ldap1.example.com"
chain-rebind-as-user TRUE
chain-idassert-bind bindmethod="simple"
binddn="cn=Auth,dc=example,dc=com"
credentials="secret"
mode="self"
chain-uri "ldap://ldap2.example.com"
chain-idassert-bind bindmethod="simple"
binddn="cn=Auth,dc=example,dc=com"
credentials="secret"
mode="none"
Any valid directives for the ldap database may be used; see
slapd-ldap(5) for details. Multiple occurrences of the chain-uri
directive may appear, to define multiple "trusted" URIs where
operations with identity assertion are chained. All URIs not listed in
the configuration are chained anonymously. All slapd-ldap(5)
directives appearing before the first occurrence of chain-uri are
inherited by all URIs, unless specifically overridden inside each URI
configuration.
FILES
/etc/ldap/slapd.conf
default slapd configuration file
SEE ALSO
slapd.conf(5), slapd-config(5), slapd-ldap(5), slapd(8).
AUTHOR
Originally implemented by Howard Chu; extended by Pierangelo Masarati.