focal (5) slapd-ldap.5.gz

Provided by: slapd_2.4.49+dfsg-2ubuntu1.10_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, 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    {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_cipher_suite=<ciphers>] [tls_crlcheck=none|peer|all]
              Specify TLS settings for regular connections.

              The first parameter only applies to ldap:// connections and so at the moment, none and  ldaps  are
              equivalent.

              With  propagate,  the  proxy  issues  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" 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/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