NAME | SYNOPSIS | DESCRIPTION | CONFIGURATION | BACKWARD COMPATIBILITY | ACCESS CONTROL | OVERLAYS | FILES | SEE ALSO | AUTHOR | COLOPHON

SLAPD-LDAP(5)                File Formats Manual               SLAPD-LDAP(5)

NAME         top

       slapd-ldap - LDAP backend to slapd

SYNOPSIS         top

       ETCDIR/slapd.conf

DESCRIPTION         top

       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.

CONFIGURATION         top

       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.

       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.

BACKWARD COMPATIBILITY         top

       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 crendentials 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.

ACCESS CONTROL         top

       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.

OVERLAYS         top

       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.

FILES         top

       ETCDIR/slapd.conf
              default slapd configuration file

SEE ALSO         top

       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).

AUTHOR         top

       Howard Chu, with enhancements by Pierangelo Masarati

COLOPHON         top

       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 2017-07-05.  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)