1 .TH SLAPD-META 5 "RELEASEDATE" "OpenLDAP LDVERSION"
2 .\" Copyright 1998-2012 The OpenLDAP Foundation, All Rights Reserved.
3 .\" Copying restrictions apply. See the COPYRIGHT file.
4 .\" Copyright 2001, Pierangelo Masarati, All rights reserved. <ando@sys-net.it>
7 .\" Portions of this document should probably be moved to slapd-ldap(5)
8 .\" and maybe manual pages for librewrite.
11 slapd\-meta \- metadirectory backend to slapd
19 performs basic LDAP proxying with respect to a set of remote LDAP
20 servers, called "targets".
21 The information contained in these servers can be presented as
22 belonging to a single Directory Information Tree (DIT).
24 A basic knowledge of the functionality of the
26 backend is recommended.
27 This backend has been designed as an enhancement of the ldap backend.
28 The two backends share many features (actually they also share
32 backend is intended to proxy operations directed to a single server, the
34 backend is mainly intended for proxying of multiple servers and possibly
35 naming context masquerading.
36 These features, although useful in many scenarios, may result in
37 excessive overhead for some applications, so its use should be
39 In the examples section, some typical scenarios will be discussed.
43 must contain schema information for the attributes and objectClasses
44 used in filters, request DN and request-related data in general.
45 It should also contain schema information for the data returned
46 by the proxied server.
47 It is the responsibility of the proxy administrator to keep the schema
48 of the proxy lined up with that of the proxied server.
51 Note: When looping back to the same instance of \fBslapd\fP(8),
52 each connection requires a new thread; as a consequence, \fBslapd\fP(8)
53 must be compiled with thread support, and the \fBthreads\fP parameter
54 may need some tuning; in those cases, unless the multiple target feature
55 is required, one may consider using \fBslapd\-relay\fP(5) instead,
56 which performs the relayed operation internally and thus reuses
60 There are examples in various places in this document, as well as in the
61 slapd/back\-meta/data/ directory in the OpenLDAP source tree.
65 options apply to the META backend database.
66 That is, they must follow a "database meta" line and come before any
67 subsequent "backend" or "database" lines.
68 Other database options are described in the
72 Note: In early versions of back-ldap and back-meta it was recommended to always set
85 This was required because operational attributes related to entry creation
86 and modification should not be proxied, as they could be mistakenly written
87 to the target server(s), generating an error.
88 The current implementation automatically sets lastmod to \fBoff\fP,
89 so its use is redundant and should be omitted.
91 .SH SPECIAL CONFIGURATION DIRECTIVES
92 Target configuration starts with the "uri" directive.
93 All the configuration directives that are not specific to targets
94 should be defined first for clarity, including those that are common
100 This directive causes a cached connection to be dropped an recreated
101 after a given ttl, regardless of being idle or not.
104 .B default\-target none
105 This directive forces the backend to reject all those operations
106 that must resolve to a single target in case none or multiple
107 targets are selected.
108 They include: add, delete, modify, modrdn; compare is not included, as
109 well as bind since, as they don't alter entries, in case of multiple
110 matches an attempt is made to perform the operation on any candidate
111 target, with the constraint that at most one must succeed.
112 This directive can also be used when processing targets to mark a
113 specific target as default.
116 .B dncache\-ttl {DISABLED|forever|<ttl>}
117 This directive sets the time-to-live of the DN cache.
118 This caches the target that holds a given DN to speed up target
119 selection in case multiple targets would result from an uncached
120 search; forever means cache never expires; disabled means no DN
121 caching; otherwise a valid ( > 0 ) ttl is required, in the format
127 .B onerr {CONTINUE|report|stop}
128 This directive allows to select the behavior in case an error is returned
129 by one target during a search.
130 The default, \fBcontinue\fP, consists in continuing the operation,
131 trying to return as much data as possible.
132 If the value is set to \fBstop\fP, the search is terminated as soon
133 as an error is returned by one target, and the error is immediately
134 propagated to the client.
135 If the value is set to \fBreport\fP, the search is continuated to the end
136 but, in case at least one target returned an error code, the first
137 non-success error code is returned.
143 do not return search reference responses.
144 By default, they are returned unless request is LDAPv2.
145 If set before any target specification, it affects all targets, unless
146 overridden by any per-target directive.
149 .B noundeffilter <NO|yes>
152 return success instead of searching if a filter is undefined or contains
154 By default, the search is propagated after replacing undefined portions
156 .BR (!(objectClass=*)) ,
157 which corresponds to the empty result set.
158 If set before any target specification, it affects all targets, unless
159 overridden by any per-target directive.
162 .B protocol\-version {0,2,3}
163 This directive indicates what protocol version must be used to contact
165 If set to 0 (the default), the proxy uses the same protocol version
166 used by the client, otherwise the requested protocol is used.
167 The proxy returns \fIunwillingToPerform\fP if an operation that is
168 incompatible with the requested protocol is attempted.
169 If set before any target specification, it affects all targets, unless
170 overridden by any per-target directive.
173 .B pseudoroot\-bind\-defer {YES|no}
174 This directive, when set to
176 causes the authentication to the remote servers with the pseudo-root
177 identity (the identity defined in each
179 directive) to be deferred until actually needed by subsequent operations.
180 Otherwise, all binds as the rootdn are propagated to the targets.
183 .B quarantine <interval>,<num>[;<interval>,<num>[...]]
184 Turns on quarantine of URIs that returned
185 .IR LDAP_UNAVAILABLE ,
186 so that an attempt to reconnect only occurs at given intervals instead
187 of any time a client requests an operation.
188 The pattern is: retry only after at least
190 seconds elapsed since last attempt, for exactly
192 times; then use the next pattern.
195 for the last pattern is "\fB+\fP", it retries forever; otherwise,
196 no more retries occur.
197 This directive must appear before any target specification;
198 it affects all targets with the same pattern.
201 .B rebind\-as\-user {NO|yes}
202 If this option is given, the client's bind credentials are remembered
203 for rebinds, when trying to re-establish a broken connection,
204 or when chasing a referral, if
210 .B session\-tracking\-request {NO|yes}
211 Adds session tracking control for all requests.
212 The client's IP and hostname, and the identity associated to each request,
213 if known, are sent to the remote server for informational purposes.
214 This directive is incompatible with setting \fIprotocol\-version\fP to 2.
215 If set before any target specification, it affects all targets, unless
216 overridden by any per-target directive.
219 .B single\-conn {NO|yes}
220 Discards current cached connection when the client rebinds.
223 .B use\-temporary\-conn {NO|yes}
226 create a temporary connection whenever competing with other threads
227 for a shared one; otherwise, wait until the shared connection is available.
229 .SH TARGET SPECIFICATION
230 Target specification starts with a "uri" directive:
233 .B uri <protocol>://[<host>]/<naming context> [...]
234 The <protocol> part can be anything
235 .BR ldap_initialize (3)
236 accepts ({ldap|ldaps|ldapi} and variants); the <host> may be
237 omitted, defaulting to whatever is set in
239 The <naming context> part is \fImandatory\fP for the first URI,
240 but it \fImust be omitted\fP for subsequent ones, if any.
241 The naming context part must be within the naming context defined for the backend,
246 suffix "\fBdc=foo,dc=com\fP"
247 uri "ldap://x.foo.com/dc=x,\fBdc=foo,dc=com\fP"
252 The <naming context> part doesn't need to be unique across the targets;
253 it may also match one of the values of the "suffix" directive.
254 Multiple URIs may be defined in a single URI statement.
255 The additional URIs must be separate arguments and must not have any
256 <naming context> part. This causes the underlying library
257 to contact the first server of the list that responds.
258 For example, if \fIl1.foo.com\fP and \fIl2.foo.com\fP are shadows
259 of the same server, the directive
262 suffix "\fBdc=foo,dc=com\fP"
263 uri "ldap://l1.foo.com/\fBdc=foo,dc=com\fP" "ldap://l2.foo.com/"
268 causes \fIl2.foo.com\fP to be contacted whenever \fIl1.foo.com\fP
270 In that case, the URI list is internally rearranged, by moving unavailable
271 URIs to the end, so that further connection attempts occur with respect to
272 the last URI that succeeded.
276 .B acl\-authcDN "<administrative DN for access control purposes>"
277 DN which is used to query the target server for acl checking,
278 as in the LDAP backend; it is supposed to have read access
279 on the target server to attributes used on the proxy for acl checking.
280 There is no risk of giving away such values; they are only used to
282 .B The acl\-authcDN identity is by no means implicitly used by the proxy
283 .B when the client connects anonymously.
286 .B acl\-passwd <password>
287 Password used with the
293 .B bind\-timeout <microseconds>
294 This directive defines the timeout, in microseconds, used when polling
295 for response after an asynchronous bind connection. The initial call
296 to ldap_result(3) is performed with a trade-off timeout of 100000 us;
297 if that results in a timeout exceeded, subsequent calls use the value
300 The default value is used also for subsequent calls if
303 If set before any target specification, it affects all targets, unless
304 overridden by any per-target directive.
307 .B chase\-referrals {YES|no}
308 enable/disable automatic referral chasing, which is delegated to the
309 underlying libldap, with rebinding eventually performed if the
310 \fBrebind\-as\-user\fP directive is used. The default is to chase referrals.
311 If set before any target specification, it affects all targets, unless
312 overridden by any per-target directive.
315 .B client\-pr {accept-unsolicited|DISABLE|<size>}
316 This feature allows to use RFC 2696 Paged Results control when performing
317 search operations with a specific target,
318 irrespective of the client's request.
319 When set to a numeric value, Paged Results control is always
320 used with \fIsize\fP as the page size.
321 When set to \fIaccept-unsolicited\fP, unsolicited Paged Results
322 control responses are accepted and honored
323 for compatibility with broken remote DSAs.
324 The client is not exposed to paged results handling
327 and the remote servers.
328 By default (disabled), Paged Results control is not used
329 and responses are not accepted.
330 If set before any target specification, it affects all targets, unless
331 overridden by any per-target directive.
334 .B default\-target [<target>]
335 The "default\-target" directive can also be used during target specification.
336 With no arguments it marks the current target as the default.
337 The optional number marks target <target> as the default one, starting
339 Target <target> must be defined.
342 .B idassert\-authzFrom <authz-regexp>
343 if defined, selects what
345 identities are authorized to exploit the identity assertion feature.
348 follows the rules defined for the
355 for details on the syntax of this field.
360 .B bindmethod=none|simple|sasl [binddn=<simple DN>] [credentials=<simple password>]
361 .B [saslmech=<SASL mech>] [secprops=<properties>] [realm=<realm>]
362 .B [authcId=<authentication ID>] [authzId=<authorization ID>]
363 .B [authz={native|proxyauthz}] [mode=<mode>] [flags=<flags>]
364 .B [starttls=no|yes|critical]
367 .B [tls_cacert=<file>]
368 .B [tls_cacertdir=<path>]
369 .B [tls_reqcert=never|allow|try|demand]
370 .B [tls_ciphersuite=<ciphers>]
371 .B [tls_protocol_min=<version>]
372 .B [tls_crlcheck=none|peer|all]
374 Allows to define the parameters of the authentication method that is
375 internally used by the proxy to authorize connections that are
376 authenticated by other databases.
377 The identity defined by this directive, according to the properties
378 associated to the authentication method, is supposed to have auth access
379 on the target server to attributes used on the proxy for authentication
380 and authorization, and to be allowed to authorize the users.
381 This requires to have
383 privileges on a wide set of DNs, e.g.
384 .BR authzTo=dn.subtree:"" ,
385 and the remote server to have
393 for details on these statements and for remarks and drawbacks about
395 The supported bindmethods are
397 \fBnone|simple|sasl\fP
401 is the default, i.e. no \fIidentity assertion\fP is performed.
403 The authz parameter is used to instruct the SASL bind to exploit
405 SASL authorization, if available; since connections are cached,
406 this should only be used when authorizing with a fixed identity
407 (e.g. by means of the
412 Otherwise, the default
414 is used, i.e. the proxyAuthz control (Proxied Authorization, RFC 4370)
415 is added to all operations.
417 The supported modes are:
419 \fB<mode> := {legacy|anonymous|none|self}\fP
425 is given, the proxy always authorizes that identity.
426 .B <authorization ID>
433 The former is supposed to be expanded by the remote server according
434 to the authz rules; see
437 In the latter case, whether or not the
439 prefix is present, the string must pass DN validation and normalization.
443 which implies that the proxy will either perform a simple bind as the
445 or a SASL bind as the
447 and assert the client's identity when it is not anonymous.
448 Direct binds are always proxied.
449 The other modes imply that the proxy will always either perform a simple bind
452 or a SASL bind as the
455 .BR idassert\-authzFrom
456 rules (see below), in which case the operation will fail;
457 eventually, it will assert some other identity according to
459 Other identity assertion modes are
463 which respectively mean that the
470 which means that no proxyAuthz control will be used, so the
474 identity will be asserted.
475 For all modes that require the use of the
477 control, on the remote server the proxy identity must have appropriate
479 permissions, or the asserted identities must have appropriate
481 permissions. Note, however, that the ID assertion feature is mostly
482 useful when the asserted identities do not exist on the remote server.
486 \fBoverride,[non\-]prescriptive,proxy\-authz\-[non\-]critical\fP
490 flag is used, identity assertion takes place even when the database
491 is authorizing for the identity of the client, i.e. after binding
492 with the provided identity, and thus authenticating it, the proxy
493 performs the identity assertion using the configured identity and
494 authentication method.
498 flag is used (the default), operations fail with
499 \fIinappropriateAuthentication\fP
500 for those identities whose assertion is not allowed by the
501 .B idassert\-authzFrom
505 flag is used, operations are performed anonymously for those identities
506 whose assertion is not allowed by the
507 .B idassert\-authzFrom
511 .B proxy\-authz\-non\-critical
512 flag is used (the default), the proxyAuthz control is not marked as critical,
513 in violation of RFC 4370. Use of
514 .B proxy\-authz\-critical
517 The TLS settings default to the same as the main slapd TLS settings,
520 which defaults to "demand".
522 The identity associated to this directive is also used for privileged
523 operations whenever \fBidassert\-bind\fP is defined and \fBacl\-bind\fP
524 is not. See \fBacl\-bind\fP for details.
528 .B idle\-timeout <time>
529 This directive causes a cached connection to be dropped an recreated
530 after it has been idle for the specified time.
531 The value can be specified as
533 [<d>d][<h>h][<m>m][<s>[s]]
535 where <d>, <h>, <m> and <s> are respectively treated as days, hours,
537 If set before any target specification, it affects all targets, unless
538 overridden by any per-target directive.
541 .B map "{attribute|objectclass} [<local name>|*] {<foreign name>|*}"
542 This maps object classes and attributes as in the LDAP backend.
547 .B network\-timeout <time>
548 Sets the network timeout value after which
549 .BR poll (2)/ select (2)
552 returns in case of no activity.
553 The value is in seconds, and it can be specified as for
555 If set before any target specification, it affects all targets, unless
556 overridden by any per-target directive.
559 .B nretries {forever|never|<nretries>}
560 This directive defines how many times a bind should be retried
561 in case of temporary failure in contacting a target. If defined
562 before any target specification, it applies to all targets (by default,
565 the global value can be overridden by redefinitions inside each target
570 The rewrite options are described in the "REWRITING" section.
573 .B subtree\-{exclude|include} "<rule>"
574 This directive allows to indicate what subtrees are actually served
576 The syntax of the supported rules is
578 \fB<rule>: [dn[.<style>]:]<pattern>\fP
580 \fB<style>: subtree|children|regex\fP
582 When \fB<style>\fP is either \fBsubtree\fP or \fBchildren\fP
583 the \fB<pattern>\fP is a DN that must be within the naming context
584 served by the target.
585 When \fB<style>\fP is \fBregex\fP the \fB<pattern>\fP is a
588 If the \fBdn.<style>:\fP prefix is omitted, \fBdn.subtree:\fP
589 is implicitly assumed for backward compatibility.
593 form if the \fIrequest DN\fP matches at least one rule,
594 the target is not considered while fulfilling the request;
595 otherwise, the target is considered based on the value of the \fIrequest DN\fP.
596 When the request is a search, also the \fIscope\fP is considered.
600 form if the \fIrequest DN\fP matches at least one rule,
601 the target is considered while fulfilling the request;
602 otherwise the target is ignored.
608 +---------+---------+-------------------+
609 | T | T | not candidate |
610 | F | T | continue checking |
611 +---------+---------+-------------------+
612 | T | F | candidate |
613 | F | F | not candidate |
614 +---------+---------+-------------------+
619 There may be multiple occurrences of the
623 directive for each of the targets, but they are mutually exclusive.
627 .B suffixmassage "<virtual naming context>" "<real naming context>"
628 All the directives starting with "rewrite" refer to the rewrite engine
629 that has been added to slapd.
630 The "suffixmassage" directive was introduced in the LDAP backend to
631 allow suffix massaging while proxying.
632 It has been obsoleted by the rewriting tools.
633 However, both for backward compatibility and for ease of configuration
634 when simple suffix massage is required, it has been preserved.
635 It wraps the basic rewriting instructions that perform suffix
636 massaging. See the "REWRITING" section for a detailed list
637 of the rewrite rules it implies.
640 .B t\-f\-support {NO|yes|discover}
641 enable if the remote server supports absolute filters
642 (see \fIRFC 4526\fP for details).
645 support is detected by reading the remote server's root DSE.
646 If set before any target specification, it affects all targets, unless
647 overridden by any per-target directive.
650 .B timeout [<op>=]<val> [...]
651 This directive allows to set per-operation timeouts.
654 \fB<op> ::= bind, add, delete, modrdn, modify, compare, search\fP
656 The overall duration of the \fBsearch\fP operation is controlled either
657 by the \fBtimelimit\fP parameter or by server-side enforced
658 time limits (see \fBtimelimit\fP and \fBlimits\fP in
661 This \fBtimeout\fP parameter controls how long the target can be
662 irresponsive before the operation is aborted.
663 Timeout is meaningless for the remaining operations,
664 \fBunbind\fP and \fBabandon\fP, which do not imply any response,
665 while it is not yet implemented in currently supported \fBextended\fP
667 If no operation is specified, the timeout \fBval\fP affects all
668 supported operations.
669 If specified before any target definition, it affects all targets
670 unless overridden by per-target directives.
672 Note: if the timeout is exceeded, the operation is cancelled
673 (according to the \fBcancel\fP directive);
674 the protocol does not provide any means to rollback operations,
675 so the client will not be notified about the result of the operation,
676 which may eventually succeeded or not.
677 In case the timeout is exceeded during a bind operation, the connection
678 is destroyed, according to RFC4511.
681 .B tls {[try\-]start|[try\-]propagate}
682 execute the StartTLS extended operation when the connection is initialized;
683 only works if the URI directive protocol scheme is not \fBldaps://\fP.
684 \fBpropagate\fP issues the StartTLS operation only if the original
686 The \fBtry\-\fP prefix instructs the proxy to continue operations
687 if the StartTLS operation failed; its use is highly deprecated.
688 If set before any target specification, it affects all targets, unless
689 overridden by any per-target directive.
692 A powerful (and in some sense dangerous) rewrite engine has been added
693 to both the LDAP and Meta backends.
694 While the former can gain limited beneficial effects from rewriting
695 stuff, the latter can become an amazingly powerful tool.
697 Consider a couple of scenarios first.
699 1) Two directory servers share two levels of naming context;
700 say "dc=a,dc=foo,dc=com" and "dc=b,dc=foo,dc=com".
701 Then, an unambiguous Meta database can be configured as:
706 suffix "\fBdc=foo,dc=com\fP"
707 uri "ldap://a.foo.com/dc=a,\fBdc=foo,dc=com\fP"
708 uri "ldap://b.foo.com/dc=b,\fBdc=foo,dc=com\fP"
712 Operations directed to a specific target can be easily resolved
713 because there are no ambiguities.
714 The only operation that may resolve to multiple targets is a search
715 with base "dc=foo,dc=com" and scope at least "one", which results in
716 spawning two searches to the targets.
718 2a) Two directory servers don't share any portion of naming context,
719 but they'd present as a single DIT
720 [Caveat: uniqueness of (massaged) entries among the two servers is
721 assumed; integrity checks risk to incur in excessive overhead and have
722 not been implemented].
723 Say we have "dc=bar,dc=org" and "o=Foo,c=US",
724 and we'd like them to appear as branches of "dc=foo,dc=com", say
725 "dc=a,dc=foo,dc=com" and "dc=b,dc=foo,dc=com".
726 Then we need to configure our Meta backend as:
731 suffix "dc=foo,dc=com"
733 uri "ldap://a.bar.com/\fBdc=a,dc=foo,dc=com\fP"
734 suffixmassage "\fBdc=a,dc=foo,dc=com\fP" "dc=bar,dc=org"
736 uri "ldap://b.foo.com/\fBdc=b,dc=foo,dc=com\fP"
737 suffixmassage "\fBdc=b,dc=foo,dc=com\fP" "o=Foo,c=US"
741 Again, operations can be resolved without ambiguity, although
742 some rewriting is required.
743 Notice that the virtual naming context of each target is a branch of
744 the database's naming context; it is rewritten back and forth when
745 operations are performed towards the target servers.
746 What "back and forth" means will be clarified later.
748 When a search with base "dc=foo,dc=com" is attempted, if the
749 scope is "base" it fails with "no such object"; in fact, the
750 common root of the two targets (prior to massaging) does not
752 If the scope is "one", both targets are contacted with the base
753 replaced by each target's base; the scope is derated to "base".
754 In general, a scope "one" search is honored, and the scope is derated,
755 only when the incoming base is at most one level lower of a target's
756 naming context (prior to massaging).
758 Finally, if the scope is "sub" the incoming base is replaced
759 by each target's unmassaged naming context, and the scope
762 2b) Consider the above reported scenario with the two servers
763 sharing the same naming context:
768 suffix "\fBdc=foo,dc=com\fP"
770 uri "ldap://a.bar.com/\fBdc=foo,dc=com\fP"
771 suffixmassage "\fBdc=foo,dc=com\fP" "dc=bar,dc=org"
773 uri "ldap://b.foo.com/\fBdc=foo,dc=com\fP"
774 suffixmassage "\fBdc=foo,dc=com\fP" "o=Foo,c=US"
778 All the previous considerations hold, except that now there is
779 no way to unambiguously resolve a DN.
780 In this case, all the operations that require an unambiguous target
781 selection will fail unless the DN is already cached or a default
783 Practical configurations may result as a combination of all the
786 Note on ACLs: at present you may add whatever ACL rule you desire
787 to to the Meta (and LDAP) backends.
788 However, the meaning of an ACL on a proxy may require some
790 Two philosophies may be considered:
792 a) the remote server dictates the permissions; the proxy simply passes
793 back what it gets from the remote server.
795 b) the remote server unveils "everything"; the proxy is responsible
796 for protecting data from unauthorized access.
798 Of course the latter sounds unreasonable, but it is not.
799 It is possible to imagine scenarios in which a remote host discloses
800 data that can be considered "public" inside an intranet, and a proxy
801 that connects it to the internet may impose additional constraints.
802 To this purpose, the proxy should be able to comply with all the ACL
803 matching criteria that the server supports.
804 This has been achieved with regard to all the criteria supported by
805 slapd except a special subtle case (please file an ITS if you can
806 find other exceptions: <http://www.openldap.org/its/>).
811 access to dn="<dn>" attrs=<attr>
812 by dnattr=<dnattr> read
817 cannot be matched iff the attribute that is being requested, <attr>,
818 is NOT <dnattr>, and the attribute that determines membership,
819 <dnattr>, has not been requested (e.g. in a search)
821 In fact this ACL is resolved by slapd using the portion of entry it
822 retrieved from the remote server without requiring any further
823 intervention of the backend, so, if the <dnattr> attribute has not
824 been fetched, the match cannot be assessed because the attribute is
825 not present, not because no value matches the requirement!
827 Note on ACLs and attribute mapping: ACLs are applied to the mapped
828 attributes; for instance, if the attribute locally known as "foo" is
829 mapped to "bar" on a remote server, then local ACLs apply to attribute
830 "foo" and are totally unaware of its remote name.
831 The remote server will check permissions for "bar", and the local
832 server will possibly enforce additional restrictions to "foo".
834 .\" If this section is moved, also update the reference in
835 .\" libraries/librewrite/RATIONALE.
838 A string is rewritten according to a set of rules, called a `rewrite
840 The rules are based on POSIX (''extended'') regular expressions (regex)
841 with substring matching; basic variable substitution and map resolution
842 of substrings is allowed by specific mechanisms detailed in the following.
843 The behavior of pattern matching/substitution can be altered by a set
846 The underlying concept is to build a lightweight rewrite module
847 for the slapd server (initially dedicated to the LDAP backend).
849 An incoming string is matched against a set of rules.
850 Rules are made of a regex match pattern, a substitution pattern
851 and a set of actions, described by a set of flags.
852 In case of match a string rewriting is performed according to the
853 substitution pattern that allows to refer to substrings matched in the
855 The actions, if any, are finally performed.
856 The substitution pattern allows map resolution of substrings.
857 A map is a generic object that maps a substitution pattern to a value.
858 The flags are divided in "Pattern matching Flags" and "Action Flags";
859 the former alter the regex match pattern behavior while the latter
860 alter the action that is taken after substitution.
861 .SH "Pattern Matching Flags"
864 honors case in matching (default is case insensitive)
867 use POSIX ''basic'' regular expressions (default is ''extended'')
872 recursive passes for a specific rule; does not alter the max total count
873 of passes, so it can only enforce a stricter limit for a specific rule.
877 apply the rule once only (default is recursive)
880 stop applying rules in case of match; the current rule is still applied
881 recursively; combine with `:' to apply the current rule only once
885 stop current operation if the rule matches, and issue an `unwilling to
891 rules back and forth (watch for loops!).
892 Note that `G{1}' is implicit in every rule.
895 ignores errors in rule; this means, in case of error, e.g. issued by a
896 map, the error is treated as a missed match.
897 The `unwilling to perform' is not overridden.
903 as return code if the rule matches; the flag does not alter the recursive
904 behavior of the rule, so, to have it performed only once, it must be used
905 in combination with `:', e.g.
907 returns the value `16' after exactly one execution of the rule, if the
909 As a consequence, its behavior is equivalent to `@', with the return
912 or, in other words, `@' is equivalent to `U{0}'.
913 By convention, the freely available codes are above 16 included;
914 the others are reserved.
916 The ordering of the flags can be significant.
917 For instance: `IG{2}' means ignore errors and jump two lines ahead
918 both in case of match and in case of error, while `G{2}I' means ignore
919 errors, but jump two lines ahead only in case of match.
921 More flags (mainly Action Flags) will be added as needed.
922 .SH "Pattern matching:"
927 .SH "Substitution Pattern Syntax:"
928 Everything starting with `%' requires substitution;
930 the only obvious exception is `%%', which is left as is;
932 the basic substitution is `%d', where `d' is a digit;
933 0 means the whole string, while 1-9 is a submatch;
935 a `%' followed by a `{' invokes an advanced substitution.
939 `%' `{' [ <op> ] <name> `(' <substitution> `)' `}'
942 where <name> must be a legal name for the map, i.e.
946 <name> ::= [a-z][a-z0-9]* (case insensitive)
947 <op> ::= `>' `|' `&' `&&' `*' `**' `$'
951 and <substitution> must be a legal substitution
952 pattern, with no limits on the nesting level.
957 sub context invocation; <name> must be a legal, already defined
961 external command invocation; <name> must refer to a legal, already
962 defined command name (NOT IMPL.)
965 variable assignment; <name> defines a variable in the running
966 operation structure which can be dereferenced later; operator
968 assigns a variable in the rewrite context scope; operator
970 assigns a variable that scopes the entire session, e.g. its value
971 can be dereferenced later by other rewrite contexts
974 variable dereferencing; <name> must refer to a variable that is
975 defined and assigned for the running operation; operator
977 dereferences a variable scoping the rewrite context; operator
979 dereferences a variable scoping the whole session, e.g. the value
980 is passed across rewrite contexts
983 parameter dereferencing; <name> must refer to an existing parameter;
984 the idea is to make some run-time parameters set by the system
985 available to the rewrite engine, as the client host name, the bind DN
986 if any, constant parameters initialized at config time, and so on;
987 no parameter is currently set by either
991 but constant parameters can be defined in the configuration file
996 Substitution escaping has been delegated to the `%' symbol,
997 which is used instead of `\e' in string substitution patterns
998 because `\e' is already escaped by slapd's low level parsing routines;
999 as a consequence, regex escaping requires two `\e' symbols,
1000 e.g. `\fB.*\e.foo\e.bar\fP' must be written as `\fB.*\e\e.foo\e\e.bar\fP'.
1002 .\" The symbol can be altered at will by redefining the related macro in
1003 .\" "rewrite-int.h".
1005 .SH "Rewrite context:"
1006 A rewrite context is a set of rules which are applied in sequence.
1007 The basic idea is to have an application initialize a rewrite
1008 engine (think of Apache's mod_rewrite ...) with a set of rewrite
1009 contexts; when string rewriting is required, one invokes the
1010 appropriate rewrite context with the input string and obtains the
1011 newly rewritten one if no errors occur.
1013 Each basic server operation is associated to a rewrite context;
1014 they are divided in two main groups: client \-> server and
1015 server \-> client rewriting.
1021 (default) if defined and no specific context
1026 searchFilterAttrDN search
1028 compareAttrDN compare AVA
1032 modifyAttrDN modify AVA
1034 newSuperiorDN modrdn
1036 exopPasswdDN password modify extended operation DN if proxy
1044 searchResult search (only if defined; no default;
1045 acts on DN and DN-syntax attributes
1047 searchAttrDN search AVA
1048 matchedDN all ops (only if applicable)
1052 .SH "Basic configuration syntax"
1054 .B rewriteEngine { on | off }
1055 If `on', the requested rewriting is performed; if `off', no
1056 rewriting takes place (an easy way to stop rewriting without
1057 altering too much the configuration file).
1059 .B rewriteContext <context name> "[ alias <aliased context name> ]"
1060 <Context name> is the name that identifies the context, i.e. the name
1061 used by the application to refer to the set of rules it contains.
1062 It is used also to reference sub contexts in string rewriting.
1063 A context may alias another one.
1064 In this case the alias context contains no rule, and any reference to
1065 it will result in accessing the aliased one.
1067 .B rewriteRule "<regex match pattern>" "<substitution pattern>" "[ <flags> ]"
1068 Determines how a string can be rewritten if a pattern is matched.
1069 Examples are reported below.
1070 .SH "Additional configuration syntax:"
1072 .B rewriteMap "<map type>" "<map name>" "[ <map attrs> ]"
1073 Allows to define a map that transforms substring rewriting into
1075 The map is referenced inside the substitution pattern of a rule.
1077 .B rewriteParam <param name> <param value>
1078 Sets a value with global scope, that can be dereferenced by the
1079 command `%{$paramName}'.
1081 .B rewriteMaxPasses <number of passes> [<number of passes per rule>]
1082 Sets the maximum number of total rewriting passes that can be
1083 performed in a single rewrite operation (to avoid loops).
1084 A safe default is set to 100; note that reaching this limit is still
1085 treated as a success; recursive invocation of rules is simply
1087 The count applies to the rewriting operation as a whole, not
1088 to any single rule; an optional per-rule limit can be set.
1089 This limit is overridden by setting specific per-rule limits
1090 with the `M{n}' flag.
1091 .SH "Configuration examples:"
1093 # set to `off' to disable rewriting
1096 # the rules the "suffixmassage" directive implies
1098 # all dataflow from client to server referring to DNs
1099 rewriteContext default
1100 rewriteRule "(.*)<virtualnamingcontext>$" "%1<realnamingcontext>" ":"
1102 rewriteContext searchFilter
1103 # all dataflow from server to client
1104 rewriteContext searchResult
1105 rewriteRule "(.*)<realnamingcontext>$" "%1<virtualnamingcontext>" ":"
1106 rewriteContext searchAttrDN alias searchResult
1107 rewriteContext matchedDN alias searchResult
1109 # Everything defined here goes into the `default' context.
1110 # This rule changes the naming context of anything sent
1111 # to `dc=home,dc=net' to `dc=OpenLDAP, dc=org'
1113 rewriteRule "(.*)dc=home,[ ]?dc=net"
1114 "%1dc=OpenLDAP, dc=org" ":"
1116 # since a pretty/normalized DN does not include spaces
1117 # after rdn separators, e.g. `,', this rule suffices:
1119 rewriteRule "(.*)dc=home,dc=net"
1120 "%1dc=OpenLDAP,dc=org" ":"
1122 # Start a new context (ends input of the previous one).
1123 # This rule adds blanks between DN parts if not present.
1124 rewriteContext addBlanks
1125 rewriteRule "(.*),([^ ].*)" "%1, %2"
1127 # This one eats blanks
1128 rewriteContext eatBlanks
1129 rewriteRule "(.*),[ ](.*)" "%1,%2"
1131 # Here control goes back to the default rewrite
1132 # context; rules are appended to the existing ones.
1133 # anything that gets here is piped into rule `addBlanks'
1134 rewriteContext default
1135 rewriteRule ".*" "%{>addBlanks(%0)}" ":"
1137 .\" # Anything with `uid=username' is looked up in
1138 .\" # /etc/passwd for gecos (I know it's nearly useless,
1139 .\" # but it is there just as a guideline to implementing
1141 .\" # Note the `I' flag that leaves `uid=username' in place
1142 .\" # if `username' does not have a valid account, and the
1143 .\" # `:' that forces the rule to be processed exactly once.
1144 .\" rewriteContext uid2Gecos
1145 .\" rewriteRule "(.*)uid=([a-z0-9]+),(.+)"
1146 .\" "%1cn=%2{xpasswd},%3" "I:"
1148 .\" # Finally, in a bind, if one uses a `uid=username' DN,
1149 .\" # it is rewritten in `cn=name surname' if possible.
1150 .\" rewriteContext bindDN
1151 .\" rewriteRule ".*" "%{>addBlanks(%{>uid2Gecos(%0)})}" ":"
1153 # Rewrite the search base according to `default' rules.
1154 rewriteContext searchBase alias default
1156 # Search results with OpenLDAP DN are rewritten back with
1157 # `dc=home,dc=net' naming context, with spaces eaten.
1158 rewriteContext searchResult
1159 rewriteRule "(.*[^ ]?)[ ]?dc=OpenLDAP,[ ]?dc=org"
1160 "%{>eatBlanks(%1)}dc=home,dc=net" ":"
1162 # Bind with email instead of full DN: we first need
1163 # an ldap map that turns attributes into a DN (the
1164 # argument used when invoking the map is appended to
1165 # the URI and acts as the filter portion)
1166 rewriteMap ldap attr2dn "ldap://host/dc=my,dc=org?dn?sub"
1168 # Then we need to detect DN made up of a single email,
1169 # e.g. `mail=someone@example.com'; note that the rule
1170 # in case of match stops rewriting; in case of error,
1171 # it is ignored. In case we are mapping virtual
1172 # to real naming contexts, we also need to rewrite
1173 # regular DNs, because the definition of a bindDn
1174 # rewrite context overrides the default definition.
1175 rewriteContext bindDN
1176 rewriteRule "^mail=[^,]+@[^,]+$" "%{attr2dn(%0)}" ":@I"
1178 # This is a rather sophisticated example. It massages a
1179 # search filter in case who performs the search has
1180 # administrative privileges. First we need to keep
1181 # track of the bind DN of the incoming request, which is
1182 # stored in a variable called `binddn' with session scope,
1183 # and left in place to allow regular binding:
1184 rewriteContext bindDN
1185 rewriteRule ".+" "%{&&binddn(%0)}%0" ":"
1187 # A search filter containing `uid=' is rewritten only
1188 # if an appropriate DN is bound.
1189 # To do this, in the first rule the bound DN is
1190 # dereferenced, while the filter is decomposed in a
1191 # prefix, in the value of the `uid=<arg>' AVA, and
1192 # in a suffix. A tag `<>' is appended to the DN.
1193 # If the DN refers to an entry in the `ou=admin' subtree,
1194 # the filter is rewritten OR-ing the `uid=<arg>' with
1195 # `cn=<arg>'; otherwise it is left as is. This could be
1196 # useful, for instance, to allow apache's auth_ldap-1.4
1197 # module to authenticate users with both `uid' and
1198 # `cn', but only if the request comes from a possible
1199 # `cn=Web auth,ou=admin,dc=home,dc=net' user.
1200 rewriteContext searchFilter
1201 rewriteRule "(.*\e\e()uid=([a-z0-9_]+)(\e\e).*)"
1202 "%{**binddn}<>%{&prefix(%1)}%{&arg(%2)}%{&suffix(%3)}"
1204 rewriteRule "[^,]+,ou=admin,dc=home,dc=net"
1205 "%{*prefix}|(uid=%{*arg})(cn=%{*arg})%{*suffix}" ":@I"
1206 rewriteRule ".*<>" "%{*prefix}uid=%{*arg}%{*suffix}" ":"
1208 # This example shows how to strip unwanted DN-valued
1209 # attribute values from a search result; the first rule
1210 # matches DN values below "ou=People,dc=example,dc=com";
1211 # in case of match the rewriting exits successfully.
1212 # The second rule matches everything else and causes
1213 # the value to be rejected.
1214 rewriteContext searchResult
1215 rewriteRule ".*,ou=People,dc=example,dc=com" "%0" ":@"
1216 rewriteRule ".*" "" "#"
1218 .SH "LDAP Proxy resolution (a possible evolution of slapd\-ldap(5)):"
1219 In case the rewritten DN is an LDAP URI, the operation is initiated
1220 towards the host[:port] indicated in the uri, if it does not refer
1221 to the local server.
1225 rewriteRule '^cn=root,.*' '%0' 'G{3}'
1226 rewriteRule '^cn=[a-l].*' 'ldap://ldap1.my.org/%0' ':@'
1227 rewriteRule '^cn=[m-z].*' 'ldap://ldap2.my.org/%0' ':@'
1228 rewriteRule '.*' 'ldap://ldap3.my.org/%0' ':@'
1231 (Rule 1 is simply there to illustrate the `G{n}' action; it could have
1235 rewriteRule '^cn=root,.*' 'ldap://ldap3.my.org/%0' ':@'
1238 with the advantage of saving one rewrite pass ...)
1243 backend does not honor all ACL semantics as described in
1244 .BR slapd.access (5).
1245 In general, access checking is delegated to the remote server(s).
1250 pseudo-attribute and to the other attribute values of the entries
1253 operation is honored, which is performed by the frontend.
1255 .SH PROXY CACHE OVERLAY
1256 The proxy cache overlay
1257 allows caching of LDAP search requests (queries) in a local database.
1259 .BR slapo\-pcache (5)
1262 .SH DEPRECATED STATEMENTS
1263 The following statements have been deprecated and should no longer be used.
1266 .B pseudorootdn "<substitute DN in case of rootdn bind>"
1272 .B pseudorootpw "<substitute password in case of rootdn bind>"
1282 default slapd configuration file
1285 .BR slapd\-ldap (5),
1286 .BR slapo\-pcache (5),
1291 Pierangelo Masarati, based on back-ldap by Howard Chu