slapd-ldap

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



NAME
       slapd-ldap - LDAP backend to slapd

SYNOPSIS
       /etc/openldap/slapd.conf

DESCRIPTION
       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
       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

              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.

              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} [starttls=no] [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" and
              starttls which is overshadowed by the first keyword and thus
              ignored.


       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
       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
       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
       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
       /etc/openldap/slapd.conf
              default slapd configuration file

SEE ALSO
       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
       Howard Chu, with enhancements by Pierangelo Masarati



OpenLDAP 2.4.48                   2019/07/24                     SLAPD-LDAP(5)