jammy (5) slapd-ldap.5.gz

Provided by: slapd_2.5.18+dfsg-0ubuntu0.22.04.3_amd64 bug

NAME

       slapd-ldap - LDAP backend to slapd

SYNOPSIS

       /etc/ldap/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, the slapd(8) 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_reqsan=never|allow|try|demand]       [tls_cipher_suite=<ciphers>]        [tls_ecname=<names>]
              [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.

              The  TLS settings default to the same as the main slapd TLS settings, except for tls_reqcert which
              defaults to "demand", and tls_reqsan which defaults to "allow".

       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-pool-max <int>
              This directive defines the maximum size of the privileged connections pool.

       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> mostly 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.  This
              parameter differs from the documented behavior in relation to the meaning of *, which in this case
              allows anonymous rather than denies.

       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_reqsan=never|allow|try|demand]
              [tls_cipher_suite=<ciphers>]           [tls_ecname=<names>]           [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", and tls_reqsan which defaults to "allow".

              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.

       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.

       tcp-user-timeout <milliseconds>
              If non-zero, corresponds to the TCP_USER_TIMEOUT set on the  target  connections,  overriding  the
              operating  system  setting.   Only some systems support the customization of this parameter, it 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    {none|[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_reqsan=never|allow|try|demand]        [tls_cipher_suite=<ciphers>]       [tls_ecname=<names>]
              [tls_crlcheck=none|peer|all]
              Specify TLS settings for regular connections.

              If the first parameter is not "none" then this configures the TLS settings to be used for  regular
              connections.  The StartTLS extended operation will be used when establishing the connection 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.

              With  propagate, the proxy issues the StartTLS operation only if the original connection has a TLS
              layer set up.  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", tls_reqsan which defaults to "allow", 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.

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/ldap/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