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NAME | SYNOPSIS | DESCRIPTION | CONFIGURATION | BACKWARD COMPATIBILITY | ACCESS CONTROL | OVERLAYS | FILES | SEE ALSO | AUTHOR | COLOPHON |
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SLAPD-LDAP(5) File Formats Manual SLAPD-LDAP(5)
slapd-ldap - LDAP backend to slapd
ETCDIR/slapd.conf
The LDAP backend to 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 idassert-* rules
below. The administrative identity of the proxy, on the remote
server, must be allowed to authorize by means of appropriate authzTo
rules; see slapd.conf(5) for details.
The proxy instance of slapd(8) must contain schema information for
the attributes and objectClasses used in filters, request DNs and
request-related data in general. It should also contain schema
information for the data returned by the proxied server. It is the
responsibility of the proxy administrator to keep the schema of the
proxy lined up with that of the proxied server.
Note: When looping back to the same instance of slapd(8), each
connection requires a new thread; as a consequence, slapd(8) must be
compiled with thread support, and the threads parameter may need some
tuning; in those cases, one may consider using slapd-relay(5)
instead, which performs the relayed operation internally and thus
reuses the same connection.
These 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 slapd.conf(5) manual page.
Note: In early versions of back-ldap it was recommended to always set
lastmod off
for ldap and meta databases. This was required 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.
uri <ldapurl>
LDAP server to use. Multiple URIs can be set in a single
ldapurl argument, resulting in the underlying library
automatically calling the first server of the list that
responds, e.g.
uri "ldap://host/ ldap://backup-host/"
The URI list is space- or comma-separated. Whenever the
server that responds is not the first one in the list, the
list is rearranged and the responsive server is moved to the
head, so that it will be first contacted the next time a
connection needs to be created.
acl-bind bindmethod=simple|sasl [binddn=<simple DN>]
[credentials=<simple password>] [saslmech=<SASL mech>]
[secprops=<properties>] [realm=<realm>]
[authcId=<authentication ID>] [authzId=<authorization ID>]
[starttls=no|yes|critical] [tls_cert=<file>] [tls_key=<file>]
[tls_cacert=<file>] [tls_cacertdir=<path>]
[tls_reqcert=never|allow|try|demand]
[tls_cipher_suite=<ciphers>]
[tls_protocol_min=<major>[.<minor>]]
[tls_crlcheck=none|peer|all]
Allows one to define the parameters of the authentication
method that is internally used by the proxy to collect info
related to access control, and whenever an operation occurs
with the identity of the rootdn of the LDAP proxy database.
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 simple bind,
with empty binddn and credentials, which means that the
related operations will be performed anonymously. If not set,
and if idassert-bind is defined, this latter identity is used
instead. See idassert-bind for details.
The connection between the proxy database and the remote
server associated to this identity is cached regardless of the
lifespan of the client-proxy connection that first established
it.
This identity is not implicitly used by the proxy when the
client connects anonymously. The idassert-bind feature,
instead, in some cases can be crafted to implement that
behavior, which is intrinsically unsafe and should be used
with extreme care. This directive obsoletes acl-authcDN, and
acl-passwd.
The TLS settings default to the same as the main slapd TLS
settings, except for tls_reqcert which defaults to "demand".
cancel {ABANDON|ignore|exop[-discover]}
Defines how to handle operation cancellation. By default,
abandon is invoked, so the operation is abandoned immediately.
If set to ignore, no action is taken and any further response
is ignored; this may result in further response messages to be
queued for that connection, so it is recommended that long
lasting connections are timed out either by idle-timeout or
conn-ttl, so that resources eventually get released. If set
to exop, a cancel operation (RFC 3909) is issued, resulting in
the cancellation of the current operation; the cancel
operation waits for remote server response, so its use may not
be recommended. If set to exop-discover, support of the
cancel extended operation is detected by reading the remote
server's root DSE.
chase-referrals {YES|no}
enable/disable automatic referral chasing, which is delegated
to the underlying libldap, with rebinding eventually performed
if the rebind-as-user directive is used. The default is to
chase referrals.
conn-ttl <time>
This directive causes a cached connection to be dropped and
recreated after a given ttl, regardless of being idle or not.
idassert-authzFrom <authz-regexp>
if defined, selects what local identities are authorized to
exploit the identity assertion feature. The string <authz-
regexp> follows the rules defined for the authzFrom attribute.
See slapd.conf(5), section related to authz-policy, for
details on the syntax of this field.
idassert-bind bindmethod=none|simple|sasl [binddn=<simple DN>]
[credentials=<simple password>] [saslmech=<SASL mech>]
[secprops=<properties>] [realm=<realm>]
[authcId=<authentication ID>] [authzId=<authorization ID>]
[authz={native|proxyauthz}] [mode=<mode>] [flags=<flags>]
[starttls=no|yes|critical] [tls_cert=<file>] [tls_key=<file>]
[tls_cacert=<file>] [tls_cacertdir=<path>]
[tls_reqcert=never|allow|try|demand]
[tls_cipher_suite=<ciphers>] [tls_protocol_min=<version>]
[tls_crlcheck=none|peer|all]
Allows one to define the parameters of the authentication
method that is internally used by the proxy to authorize
connections that are authenticated by other databases. Direct
binds are always proxied without any idassert handling.
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 proxyAuthz privileges on a wide set of DNs,
e.g. authzTo=dn.subtree:"", and the remote server to have
authz-policy set to to or both. See slapd.conf(5) for details
on these statements and for remarks and drawbacks about their
usage. The supported bindmethods are
none|simple|sasl
where none is the default, i.e. no identity assertion is
performed.
The authz parameter is used to instruct the SASL bind to
exploit 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
authzDN or authzID parameters). Otherwise, the default
proxyauthz is used, i.e. the proxyAuthz control (Proxied
Authorization, RFC 4370) is added to all operations.
The supported modes are:
<mode> := {legacy|anonymous|none|self}
If <mode> is not present, and authzId is given, the proxy
always authorizes that identity. <authorization ID> can be
u:<user>
[dn:]<DN>
The former is supposed to be expanded by the remote server
according to the authz rules; see slapd.conf(5) for details.
In the latter case, whether or not the dn: prefix is present,
the string must pass DN validation and normalization.
The default mode is legacy, which implies that the proxy will
either perform a simple bind as the authcDN or a SASL bind as
the authcID and assert the client's identity when it is not
anonymous. The other modes imply that the proxy will always
either perform a simple bind as the authcDN or a SASL bind as
the authcID, unless restricted by idassert-authzFrom rules
(see below), in which case the operation will fail;
eventually, it will assert some other identity according to
<mode>. Other identity assertion modes are anonymous and
self, which respectively mean that the empty or the client's
identity will be asserted; none, which means that no
proxyAuthz control will be used, so the authcDN or the authcID
identity will be asserted. For all modes that require the use
of the proxyAuthz control, on the remote server the proxy
identity must have appropriate authzTo permissions, or the
asserted identities must have appropriate 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
override,[non-]prescriptive,proxy-authz-[non-]critical,dn-{authzid|whoami}
When the override flag is used, identity assertion takes place
even when the database is authorizing for the identity of the
client, i.e. after binding with the provided identity, and
thus authenticating it, the proxy performs the identity
assertion using the configured identity and authentication
method.
When the prescriptive flag is used (the default), operations
fail with inappropriateAuthentication for those identities
whose assertion is not allowed by the idassert-authzFrom
patterns. If the non-prescriptive flag is used, operations
are performed anonymously for those identities whose assertion
is not allowed by the idassert-authzFrom patterns.
When the proxy-authz-non-critical flag is used (the default),
the proxyAuthz control is not marked as critical, in violation
of RFC 4370. Use of proxy-authz-critical is recommended.
When the dn-authzid flag is used, RFC 3829 LDAP Authorization
Identity Controls is used to retrieve the identity associated
to the SASL identity; when the dn-whoami flag is used, RFC
4532 LDAP Who am I? Operation is performed after the bind for
the same purpose.
The TLS settings default to the same as the main slapd TLS
settings, except for tls_reqcert which defaults to "demand".
The identity associated to this directive is also used for
privileged operations whenever idassert-bind is defined and
acl-bind is not. See acl-bind for details.
This directive obsoletes idassert-authcDN, idassert-passwd,
idassert-mode, and idassert-method.
idassert-passthru <authz-regexp>
if defined, selects what local identities bypass the identity
assertion feature. Those identities need to be known by the
remote host. The string <authz-regexp> follows the rules
defined for the authzFrom attribute. See slapd.conf(5),
section related to authz-policy, for details on the syntax of
this field.
idle-timeout <time>
This directive causes a cached connection to be dropped an
recreated after it has been idle for the specified time.
keepalive <idle>:<probes>:<interval>
The keepalive parameter sets the values of idle, probes, and
interval used to check whether a socket is alive; idle is the
number of seconds a connection needs to remain idle before TCP
starts sending keepalive probes; probes is the maximum number
of keepalive probes TCP should send before dropping the
connection; interval is interval in seconds between individual
keepalive probes. Only some systems support the customization
of these values; the keepalive parameter is ignored otherwise,
and system-wide settings are used.
network-timeout <time>
Sets the network timeout value after which poll(2)/select(2)
following a connect(2) returns in case of no activity. The
value is in seconds, and it can be specified as for
idle-timeout.
norefs <NO|yes>
If yes, do not return search reference responses. By default,
they are returned unless request is LDAPv2.
omit-unknown-schema <NO|yes>
If yes, do not return objectClasses or attributes that are not
known to the local server. The default is to return all
schema elements.
noundeffilter <NO|yes>
If yes, return success instead of searching if a filter is
undefined or contains undefined portions. By default, the
search is propagated after replacing undefined portions with
(!(objectClass=*)), which corresponds to the empty result set.
onerr {CONTINUE|stop}
This directive allows one to select the behavior in case an
error is returned by the remote server during a search. The
default, continue, consists in returning success. If the
value is set to stop, the error is returned to the client.
protocol-version {0,2,3}
This directive indicates what protocol version must be used to
contact the remote server. If set to 0 (the default), the
proxy uses the same protocol version used by the client,
otherwise the requested protocol is used. The proxy returns
unwillingToPerform if an operation that is incompatible with
the requested protocol is attempted.
proxy-whoami {NO|yes}
Turns on proxying of the WhoAmI extended operation. If this
option is given, back-ldap will replace slapd's original
WhoAmI routine with its own. On slapd sessions that were
authenticated by back-ldap, the WhoAmI request will be
forwarded to the remote LDAP server. Other sessions will be
handled by the local slapd, as before. This option is mainly
useful in conjunction with Proxy Authorization.
quarantine <interval>,<num>[;<interval>,<num>[...]]
Turns on quarantine of URIs that returned LDAP_UNAVAILABLE, so
that an attempt to reconnect only occurs at given intervals
instead of any time a client requests an operation. The
pattern is: retry only after at least interval seconds elapsed
since last attempt, for exactly num times; then use the next
pattern. If num for the last pattern is "+", it retries
forever; otherwise, no more retries occur. The process can be
restarted by resetting the olcDbQuarantine attribute of the
database entry in the configuration backend.
rebind-as-user {NO|yes}
If this option is given, the client's bind credentials are
remembered for rebinds, when trying to re-establish a broken
connection, or when chasing a referral, if chase-referrals is
set to yes.
session-tracking-request {NO|yes}
Adds session tracking control for all requests. The client's
IP and hostname, and the identity associated to each request,
if known, are sent to the remote server for informational
purposes. This directive is incompatible with setting
protocol-version to 2.
single-conn {NO|yes}
Discards current cached connection when the client rebinds.
t-f-support {NO|yes|discover}
enable if the remote server supports absolute filters (see RFC
4526 for details). If set to discover, support is detected by
reading the remote server's root DSE.
timeout [<op>=]<val> [...]
This directive allows one to set per-operation timeouts.
Operations can be
<op> ::= bind, add, delete, modrdn, modify, compare, search
The overall duration of the search operation is controlled
either by the timelimit parameter or by server-side enforced
time limits (see timelimit and limits in slapd.conf(5) for
details). This timeout parameter controls how long the target
can be irresponsive before the operation is aborted. Timeout
is meaningless for the remaining operations, unbind and
abandon, which do not imply any response, while it is not yet
implemented in currently supported extended operations. If no
operation is specified, the timeout val affects all supported
operations.
Note: if the timelimit is exceeded, the operation is cancelled
(according to the cancel directive); the protocol does not
provide any means to rollback operations, so the client will
not be notified about the result of the operation, which may
eventually succeeded or not. In case the timeout is exceeded
during a bind operation, the connection is destroyed,
according to RFC4511.
Note: in some cases, this backend may issue binds prior to
other operations (e.g. to bind anonymously or with some
prescribed identity according to the idassert-bind directive).
In this case, the timeout of the operation that resulted in
the bind is used.
tls {[try-]start|[try-]propagate|ldaps} [tls_cert=<file>]
[tls_key=<file>] [tls_cacert=<file>] [tls_cacertdir=<path>]
[tls_reqcert=never|allow|try|demand]
[tls_cipher_suite=<ciphers>] [tls_crlcheck=none|peer|all]
Specify the use of TLS when a regular connection is
initialized. The StartTLS extended operation will be used
unless the URI directive protocol scheme is ldaps://. In that
case this keyword may only be set to "ldaps" and the StartTLS
operation will not be used. propagate issues the StartTLS
operation only if the original connection did. The try-
prefix instructs the proxy to continue operations if the
StartTLS operation failed; its use is not recommended.
The TLS settings default to the same as the main slapd TLS
settings, except for tls_reqcert which defaults to "demand".
use-temporary-conn {NO|yes}
when set to yes, create a temporary connection whenever
competing with other threads for a shared one; otherwise, wait
until the shared connection is available.
The LDAP backend has been heavily reworked between releases 2.2 and
2.3, and subsequently between 2.3 and 2.4. As a side-effect, some of
the traditional directives have been deprecated and should be no
longer used, as they might disappear in future releases.
acl-authcDN <administrative DN for access control purposes>
Formerly known as the binddn, it is the DN that is used to
query the target server for acl checking; it 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 acl-authcDN identity is by no means implicitly used by the
proxy when the client connects anonymously. The idassert-*
feature can be used (at own risk) for that purpose instead.
This directive is obsoleted by the binddn arg of acl-bind when
bindmethod=simple, and will be dismissed in the future.
acl-passwd <password>
Formerly known as the bindpw, it is the password used with the
above acl-authcDN directive. This directive is obsoleted by
the credentials arg of acl-bind when bindmethod=simple, and
will be dismissed in the future.
idassert-authcDN <administrative DN for proxyAuthz purposes>
DN which is used to propagate the client's identity to the
target by means of the proxyAuthz control when the client does
not belong to the DIT fragment that is being proxied by back-
ldap. This directive is obsoleted by the binddn arg of
idassert-bind when bindmethod=simple, and will be dismissed in
the future.
idassert-passwd <password>
Password used with the idassert-authcDN above. This directive
is obsoleted by the credentials arg of idassert-bind when
bindmethod=simple, and will be dismissed in the future.
idassert-mode <mode> [<flags>]
defines what type of identity assertion is used. This
directive is obsoleted by the mode arg of idassert-bind, and
will be dismissed in the future.
idassert-method <method> [<saslargs>]
This directive is obsoleted by the bindmethod arg of
idassert-bind, and will be dismissed in the future.
port <port>
this directive is no longer supported. Use the uri directive
as described above.
server <hostname[:port]>
this directive is no longer supported. Use the uri directive
as described above.
suffixmassage, map, rewrite*
These directives are no longer supported by back-ldap; their
functionality is now delegated to the rwm overlay.
Essentially, add a statement
overlay rwm
first, and prefix all rewrite/map statements with rwm- to
obtain the original behavior. See slapo-rwm(5) for details.
The ldap backend does not honor all ACL semantics as described in
slapd.access(5). In general, access checking is delegated to the
remote server(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.
The LDAP backend provides basic proxying functionalities to many
overlays. The chain overlay, described in slapo-chain(5), and the
translucent overlay, described in slapo-translucent(5), deserve a
special mention.
Conversely, there are many overlays that are best used in conjunction
with the LDAP backend. The proxycache overlay allows caching of LDAP
search requests (queries) in a local database. See slapo-pcache(5)
for details. The rwm overlay provides DN rewrite and
attribute/objectClass mapping capabilities to the underlying
database. See slapo-rwm(5) for details.
ETCDIR/slapd.conf
default slapd configuration file
slapd.conf(5), slapd-config(5), slapd-meta(5), slapo-chain(5),
slapo-pcache(5), slapo-rwm(5), slapo-translucent(5), slapd(8),
ldap(3).
Howard Chu, with enhancements by Pierangelo Masarati
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
⟨git://git.openldap.org/openldap.git⟩ on 2018-02-02. (At that time,
the date of the most recent commit that was found in the repository
was 2018-01-30.) 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 man-pages@man7.org
OpenLDAP LDVERSION RELEASEDATE SLAPD-LDAP(5)
Pages that refer to this page: slapd-asyncmeta(5), slapd.backends(5), slapd-meta(5), slapd.overlays(5), slapo-chain(5), slapo-pbind(5), slapo-pcache(5), slapo-rwm(5), slapo-translucent(5)
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