slapd-ldap.5

OpenLdap是LDAP的开源项目

.TH SLAPD-LDAP 5 "RELEASEDATE" "OpenLDAP LDVERSION"
.\" Copyright 1998-2007 The OpenLDAP Foundation All Rights Reserved.
.\" Copying restrictions apply.  See COPYRIGHT/LICENSE.
.\" $OpenLDAP: pkg/ldap/doc/man/man5/slapd-ldap.5,v 1.24.2.17 2007/01/02 21:43:45 kurt Exp $
.SH NAME
slapd-ldap \- LDAP backend to slapd
.SH SYNOPSIS
ETCDIR/slapd.conf
.SH DESCRIPTION
The LDAP backend to
.BR slapd (8)
is not an actual database; instead it acts as a proxy to forward incoming
requests to another LDAP server. While processing requests it will also
chase referrals, so that referrals are fully processed instead of being
returned to the slapd client.

Sessions that explicitly Bind to the back-ldap database always create their
own private connection to the remote LDAP server. Anonymous sessions will
share a single anonymous connection to the remote server. For sessions bound
through other mechanisms, all sessions with the same DN will share the
same connection. This connection pooling strategy can enhance the proxy's
efficiency by reducing the overhead of repeatedly making/breaking multiple
connections.

The ldap database can also act as an information service, i.e. the identity
of locally authenticated clients is asserted to the remote server, possibly
in some modified form.
For this purpose, the proxy binds to the remote server with some 
administrative identity, and, if required, authorizes the asserted identity.
See the 
.IR idassert- *
rules below.
The administrative identity of the proxy, on the remote server, must be 
allowed to authorize by means of appropriate
.B authzTo
rules; see 
.BR slapd.conf (5)
for details.

.LP
Note: When looping back to the same instance of \fBslapd\fP(8), 
each connection requires a new thread; as a consequence, \fBslapd\fP(8)
must be compiled with thread support, and the \fBthreads\fP parameter 
may need some tuning; in those cases, one may consider using 
\fBslapd-relay\fP(5) instead, which performs the relayed operation 
internally and thus reuses the same connection.

.SH CONFIGURATION
These
.B slapd.conf
options apply to the LDAP backend database.
That is, they must follow a "database ldap" line and come before any
subsequent "backend" or "database" lines.
Other database options are described in the
.BR slapd.conf (5)
manual page.

.LP
Note: In early versions of back-ldap it was recommended to always set
.LP
.RS
.nf
lastmod  off
.fi
.RE
.LP
for every
.B ldap
and
.B meta
database.
This is because operational attributes related to entry creation and
modification should not be proxied, as they could be mistakenly written
to the target server(s), generating an error.
The current implementation automatically sets lastmod to off, so its use
is redundant and should be omitted, because the lastmod directive will
be deprecated in the future.

.TP
.B uri <ldapurl>
LDAP server to use.  Multiple URIs can be set in in a single
.B ldapurl
argument, resulting in the underlying library automatically 
call the first server of the list that responds, e.g. 

\fBuri "ldap://host/ ldap://backup-host/"\fP

The URI list is space- or comma-separated.
.\"This statement is mandatory.
.\".TP
.\".B server <hostport>
.\"Obsolete option; same as `uri ldap://<hostport>/'.
.HP
.hy 0
.B acl-bind
.B bindmethod=simple|sasl [binddn=<simple DN>] [credentials=<simple password>]
.B [saslmech=<SASL mech>] [secprops=<properties>] [realm=<realm>]
.B [authcId=<authentication ID>] [authzId=<authorization ID>]
.RS
Allows to define the parameters of the authentication method that is 
internally used by the proxy to collect info related to access control.
The identity defined by this directive, according to the properties
associated to the authentication method, is supposed to have read access 
on the target server to attributes used on the proxy for ACL checking.
There is no risk of giving away such values; they are only used to
check permissions.
The default is to use
.BR simple 
bind, with empty \fIbinddn\fP and \fIcredentials\fP,
which means that the related operations will be performed anonymously.

.B This identity is by no means implicitly used by the proxy 
.B when the client connects anonymously.
The
.B idassert-bind
feature, instead, in some cases can be crafted to implement that behavior,
which is \fIintrinsically unsafe and should be used with extreme care\fP.
This directive obsoletes
.BR acl-authcDN ,
and
.BR acl-passwd .
.RE

.TP
.B chase-referrals {YES|no}
enable/disable automatic referral chasing, which is delegated to the
underlying libldap, with rebinding eventually performed if the
\fBrebind-as-user\fP directive is used.  The default is to chase referrals.

.TP
.B conn-ttl <time>
This directive causes a cached connection to be dropped an recreated
after a given ttl, regardless of being idle or not.

.TP
.B idassert-authzFrom <authz-regexp>
if defined, selects what
.I local
identities are authorized to exploit the identity assertion feature.
The string
.B <authz-regexp>
follows the rules defined for the
.I authzFrom
attribute.
See 
.BR slapd.conf (5),
section related to
.BR authz-policy ,
for details on the syntax of this field.

.HP
.hy 0
.B idassert-bind
.B bindmethod=none|simple|sasl [binddn=<simple DN>] [credentials=<simple password>]
.B [saslmech=<SASL mech>] [secprops=<properties>] [realm=<realm>]
.B [authcId=<authentication ID>] [authzId=<authorization ID>]
.B [authz={native|proxyauthz}] [mode=<mode>] [flags=<flags>]
.RS
Allows to define the parameters of the authentication method that is 
internally used by the proxy to authorize connections that are 
authenticated by other databases.
The identity defined by this directive, according to the properties
associated to the authentication method, is supposed to have auth access 
on the target server to attributes used on the proxy for authentication
and authorization, and to be allowed to authorize the users.
This requires to have
.B proxyAuthz
privileges on a wide set of DNs, e.g.
.BR authzTo=dn.subtree:"" ,
and the remote server to have
.B authz-policy
set to
.B to
or
.BR both .
See
.BR slapd.conf (5)
for details on these statements and for remarks and drawbacks about
their usage.
The supported bindmethods are

\fBnone|simple|sasl\fP

where
.B none
is the default, i.e. no \fIidentity assertion\fP is performed.

The authz parameter is used to instruct the SASL bind to exploit 
.B native 
SASL authorization, if available; since connections are cached,
this should only be used when authorizing with a fixed identity
(e.g. by means of the 
.B authzDN
or
.B authzID
parameters).
Otherwise, the default
.B proxyauthz
is used, i.e. the proxyAuthz control is added to all operations.

The supported modes are:

\fB<mode> := {legacy|anonymous|none|self}\fP

If 
.B <mode>
is not present, and 
.B authzId
is given, the proxy always authorizes that identity.
.B <authorization ID>
can be 

\fBu:<user>\fP

\fB[dn:]<DN>\fP

The former is supposed to be expanded by the remote server according 
to the authz rules; see
.BR slapd.conf (5)
for details.
In the latter case, whether or not the 
.B dn:
prefix is present, the string must pass DN validation and normalization.

The default mode is 
.BR legacy ,
which implies that the proxy will either perform a simple bind as the
.I authcDN
or a SASL bind as the
.I authcID
and assert the client's identity when it is not anonymous.
Direct binds are always proxied.
The other modes imply that the proxy will always either perform a simple bind 
as the
.IR authcDN
or a SASL bind as the
.IR authcID ,
unless restricted by
.BR idassert-authzFrom
rules (see below), in which case the operation will fail;
eventually, it will assert some other identity according to
.BR <mode> .
Other identity assertion modes are
.BR anonymous
and
.BR self ,
which respectively mean that the 
.I empty 
or the 
.IR client 's 
identity
will be asserted;
.BR none ,
which means that no proxyAuthz control will be used, so the
.I authcDN
or the
.I authcID
identity will be asserted.
For all modes that require the use of the
.I proxyAuthz 
control, on the remote server the proxy identity must have appropriate 
.I authzTo
permissions, or the asserted identities must have appropriate
.I authzFrom 
permissions.  Note, however, that the ID assertion feature is mostly 
useful when the asserted identities do not exist on the remote server.

Flags can be