1SLAPD-META(5) File Formats Manual SLAPD-META(5)
2
6 slapd-meta - metadirectory backend to slapd
7
9 /etc/openldap/slapd.conf
10
12 The meta backend to slapd(8) performs basic LDAP proxying with respect
13 to a set of remote LDAP servers, called "targets". The information
14 contained in these servers can be presented as belonging to a single
15 Directory Information Tree (DIT).
16 A basic knowledge of the functionality of the slapd-ldap(5) backend is
18 recommended. This backend has been designed as an enhancement of the
19 ldap backend. The two backends share many features (actually they also
20 share portions of code). While the ldap backend is intended to proxy
21 operations directed to a single server, the meta backend is mainly
22 intended for proxying of multiple servers and possibly naming context
23 masquerading. These features, although useful in many scenarios, may
24 result in excessive overhead for some applications, so its use should
25 be carefully considered. In the examples section, some typical scenar‐
26 ios will be discussed.
27 The proxy instance of slapd(8) must contain schema information for the
29 attributes and objectClasses used in filters, request DN and request-
30 related data in general. It should also contain schema information for
31 the data returned by the proxied server. It is the responsibility of
32 the proxy administrator to keep the schema of the proxy lined up with
33 that of the proxied server.
34 Note: When looping back to the same instance of slapd(8), each connec‐
37 tion requires a new thread; as a consequence, slapd(8) must be compiled
38 with thread support, and the threads parameter may need some tuning; in
39 those cases, unless the multiple target feature is required, one may
40 consider using slapd-relay(5) instead, which performs the relayed oper‐
41 ation internally and thus reuses the same connection.
42
45 There are examples in various places in this document, as well as in
46 the slapd/back-meta/data/ directory in the OpenLDAP source tree.
47
49 These slapd.conf options apply to the META backend database. That is,
50 they must follow a "database meta" line and come before any subsequent
51 "backend" or "database" lines. Other database options are described in
52 the slapd.conf(5) manual page.
53 Note: In early versions of back-ldap and back-meta it was recommended
55 to always set
56 lastmod off
58 for ldap and meta databases. This was required because operational
60 attributes related to entry creation and modification should not be
61 proxied, as they could be mistakenly written to the target server(s),
62 generating an error. The current implementation automatically sets
63 lastmod to off, so its use is redundant and should be omitted.
64
67 Target configuration starts with the "uri" directive. All the configu‐
68 ration directives that are not specific to targets should be defined
69 first for clarity, including those that are common to all backends.
70 They are:
71 conn-ttl <time>
74 This directive causes a cached connection to be dropped an
75 recreated after a given ttl, regardless of being idle or not.
76 default-target none
79 This directive forces the backend to reject all those operations
80 that must resolve to a single target in case none or multiple
81 targets are selected. They include: add, delete, modify, mod‐
82 rdn; compare is not included, as well as bind since, as they
83 don't alter entries, in case of multiple matches an attempt is
84 made to perform the operation on any candidate target, with the
85 constraint that at most one must succeed. This directive can
86 also be used when processing targets to mark a specific target
87 as default.
88 dncache-ttl {DISABLED|forever|<ttl>}
91 This directive sets the time-to-live of the DN cache. This
92 caches the target that holds a given DN to speed up target
93 selection in case multiple targets would result from an uncached
94 search; forever means cache never expires; disabled means no DN
95 caching; otherwise a valid ( > 0 ) ttl is required, in the for‐
96 mat illustrated for the idle-timeout directive.
97 onerr {CONTINUE|report|stop}
100 This directive allows to select the behavior in case an error is
101 returned by one target during a search. The default, continue,
102 consists in continuing the operation, trying to return as much
103 data as possible. If the value is set to stop, the search is
104 terminated as soon as an error is returned by one target, and
105 the error is immediately propagated to the client. If the value
106 is set to report, the search is continuated to the end but, in
107 case at least one target returned an error code, the first non-
108 success error code is returned.
109 norefs <NO|yes>
112 If yes, do not return search reference responses. By default,
113 they are returned unless request is LDAPv2. If set before any
114 target specification, it affects all targets, unless overridden
115 by any per-target directive.
116 noundeffilter <NO|yes>
119 If yes, return success instead of searching if a filter is unde‐
120 fined or contains undefined portions. By default, the search is
121 propagated after replacing undefined portions with (!(object‐
122 Class=*)), which corresponds to the empty result set. If set
123 before any target specification, it affects all targets, unless
124 overridden by any per-target directive.
125 protocol-version {0,2,3}
128 This directive indicates what protocol version must be used to
129 contact the remote server. If set to 0 (the default), the proxy
130 uses the same protocol version used by the client, otherwise the
131 requested protocol is used. The proxy returns unwillingToPer‐
132 form if an operation that is incompatible with the requested
133 protocol is attempted. If set before any target specification,
134 it affects all targets, unless overridden by any per-target
135 directive.
136 pseudoroot-bind-defer {YES|no}
139 This directive, when set to yes, causes the authentication to
140 the remote servers with the pseudo-root identity (the identity
141 defined in each idassert-bind directive) to be deferred until
142 actually needed by subsequent operations. Otherwise, all binds
143 as the rootdn are propagated to the targets.
144 quarantine <interval>,<num>[;<interval>,<num>[...]]
147 Turns on quarantine of URIs that returned LDAP_UNAVAILABLE, so
148 that an attempt to reconnect only occurs at given intervals
149 instead of any time a client requests an operation. The pattern
150 is: retry only after at least interval seconds elapsed since
151 last attempt, for exactly num times; then use the next pattern.
152 If num for the last pattern is "+", it retries forever; other‐
153 wise, no more retries occur. This directive must appear before
154 any target specification; it affects all targets with the same
155 pattern.
156 rebind-as-user {NO|yes}
159 If this option is given, the client's bind credentials are
160 remembered for rebinds, when trying to re-establish a broken
161 connection, or when chasing a referral, if chase-referrals is
162 set to yes.
163 session-tracking-request {NO|yes}
166 Adds session tracking control for all requests. The client's IP
167 and hostname, and the identity associated to each request, if
168 known, are sent to the remote server for informational purposes.
169 This directive is incompatible with setting protocol-version to
170 2. If set before any target specification, it affects all tar‐
171 gets, unless overridden by any per-target directive.
172 single-conn {NO|yes}
175 Discards current cached connection when the client rebinds.
176 use-temporary-conn {NO|yes}
179 when set to yes, create a temporary connection whenever compet‐
180 ing with other threads for a shared one; otherwise, wait until
181 the shared connection is available.
182
185 Target specification starts with a "uri" directive:
186 uri <protocol>://[<host>]/<naming context> [...]
189 The <protocol> part can be anything ldap_initialize(3) accepts
190 ({ldap|ldaps|ldapi} and variants); the <host> may be omitted,
191 defaulting to whatever is set in ldap.conf(5). The <naming con‐
192 text> part is mandatory for the first URI, but it must be omit‐
193 ted for subsequent ones, if any. The naming context part must
194 be within the naming context defined for the backend, e.g.:
195 suffix "dc=foo,dc=com"
197 uri "ldap://x.foo.com/dc=x,dc=foo,dc=com"
198 The <naming context> part doesn't need to be unique across the
200 targets; it may also match one of the values of the "suffix"
201 directive. Multiple URIs may be defined in a single URI state‐
202 ment. The additional URIs must be separate arguments and must
203 not have any <naming context> part. This causes the underlying
204 library to contact the first server of the list that responds.
205 For example, if l1.foo.com and l2.foo.com are shadows of the
206 same server, the directive
207 suffix "dc=foo,dc=com"
209 uri "ldap://l1.foo.com/dc=foo,dc=com" "ldap://l2.foo.com/"
210 causes l2.foo.com to be contacted whenever l1.foo.com does not
212 respond. In that case, the URI list is internally rearranged,
213 by moving unavailable URIs to the end, so that further connec‐
214 tion attempts occur with respect to the last URI that succeeded.
215 acl-authcDN <administrative DN for access control purposes>
218 DN which is used to query the target server for acl checking, as
219 in the LDAP backend; it is supposed to have read access on the
220 target server to attributes used on the proxy for acl checking.
221 There is no risk of giving away such values; they are only used
222 to check permissions. The acl-authcDN identity is by no means
223 implicitly used by the proxy when the client connects anony‐
224 mously.
225 acl-passwd <password>
228 Password used with the acl-authcDN above.
229 bind-timeout <microseconds>
232 This directive defines the timeout, in microseconds, used when
233 polling for response after an asynchronous bind connection. The
234 initial call to ldap_result(3) is performed with a trade-off
235 timeout of 100000 us; if that results in a timeout exceeded,
236 subsequent calls use the value provided with bind-timeout. The
237 default value is used also for subsequent calls if bind-timeout
238 is not specified. If set before any target specification, it
239 affects all targets, unless overridden by any per-target direc‐
240 tive.
241 chase-referrals {YES|no}
244 enable/disable automatic referral chasing, which is delegated to
245 the underlying libldap, with rebinding eventually performed if
246 the rebind-as-user directive is used. The default is to chase
247 referrals. If set before any target specification, it affects
248 all targets, unless overridden by any per-target directive.
249 client-pr {accept-unsolicited|DISABLE|<size>}
252 This feature allows to use RFC 2696 Paged Results control when
253 performing search operations with a specific target, irrespec‐
254 tive of the client's request. When set to a numeric value,
255 Paged Results control is always used with size as the page size.
256 When set to accept-unsolicited, unsolicited Paged Results con‐
257 trol responses are accepted and honored for compatibility with
258 broken remote DSAs. The client is not exposed to paged results
259 handling between slapd-meta(5) and the remote servers. By
260 default (disabled), Paged Results control is not used and
261 responses are not accepted. If set before any target specifica‐
262 tion, it affects all targets, unless overridden by any per-tar‐
263 get directive.
264 default-target [<target>]
267 The "default-target" directive can also be used during target
268 specification. With no arguments it marks the current target as
269 the default. The optional number marks target <target> as the
270 default one, starting from 1. Target <target> must be defined.
271 filter <pattern>
274 This directive allows specifying a regex(5) pattern to indicate
275 what search filter terms are actually served by a target.
276 In a search request, if the search filter matches the pattern
278 the target is considered while fulfilling the request; otherwise
279 the target is ignored. There may be multiple occurrences of the
280 filter directive for each target.
281 idassert-authzFrom <authz-regexp>
284 if defined, selects what local identities are authorized to
285 exploit the identity assertion feature. The string <authz-reg‐
286 exp> follows the rules defined for the authzFrom attribute. See
287 slapd.conf(5), section related to authz-policy, for details on
288 the syntax of this field.
289 idassert-bind bindmethod=none|simple|sasl [binddn=<simple DN>]
292 [credentials=<simple password>] [saslmech=<SASL mech>]
293 [secprops=<properties>] [realm=<realm>] [authcId=<authentication
294 ID>] [authzId=<authorization ID>] [authz={native|proxyauthz}]
295 [mode=<mode>] [flags=<flags>] [starttls=no|yes|critical]
296 [tls_cert=<file>] [tls_key=<file>] [tls_cacert=<file>]
297 [tls_cacertdir=<path>] [tls_reqcert=never|allow|try|demand]
298 [tls_ciphersuite=<ciphers>] [tls_protocol_min=<major>[.<minor>]]
299 [tls_crlcheck=none|peer|all]
300 Allows to define the parameters of the authentication method
301 that is internally used by the proxy to authorize connections
302 that are authenticated by other databases. The identity defined
303 by this directive, according to the properties associated to the
304 authentication method, is supposed to have auth access on the
305 target server to attributes used on the proxy for authentication
306 and authorization, and to be allowed to authorize the users.
307 This requires to have proxyAuthz privileges on a wide set of
308 DNs, e.g. authzTo=dn.subtree:"", and the remote server to have
309 authz-policy set to to or both. See slapd.conf(5) for details
310 on these statements and for remarks and drawbacks about their
311 usage. The supported bindmethods are
312 none|simple|sasl
314 where none is the default, i.e. no identity assertion is
316 performed.
317 The authz parameter is used to instruct the SASL bind to exploit
319 native SASL authorization, if available; since connections are
320 cached, this should only be used when authorizing with a fixed
321 identity (e.g. by means of the authzDN or authzID parameters).
322 Otherwise, the default proxyauthz is used, i.e. the proxyAuthz
323 control (Proxied Authorization, RFC 4370) is added to all
324 operations.
325 The supported modes are:
327 <mode> := {legacy|anonymous|none|self}
329 If <mode> is not present, and authzId is given, the proxy always
331 authorizes that identity. <authorization ID> can be
332 u:<user>
334 [dn:]<DN>
336 The former is supposed to be expanded by the remote server
338 according to the authz rules; see slapd.conf(5) for details. In
339 the latter case, whether or not the dn: prefix is present, the
340 string must pass DN validation and normalization.
341 The default mode is legacy, which implies that the proxy will
343 either perform a simple bind as the authcDN or a SASL bind as
344 the authcID and assert the client's identity when it is not
345 anonymous. Direct binds are always proxied. The other modes
346 imply that the proxy will always either perform a simple bind as
347 the authcDN or a SASL bind as the authcID, unless restricted by
348 idassert-authzFrom rules (see below), in which case the
349 operation will fail; eventually, it will assert some other
350 identity according to <mode>. Other identity assertion modes
351 are anonymous and self, which respectively mean that the empty
352 or the client's identity will be asserted; none, which means
353 that no proxyAuthz control will be used, so the authcDN or the
354 authcID identity will be asserted. For all modes that require
355 the use of the proxyAuthz control, on the remote server the
356 proxy identity must have appropriate authzTo permissions, or the
357 asserted identities must have appropriate authzFrom permissions.
358 Note, however, that the ID assertion feature is mostly useful
359 when the asserted identities do not exist on the remote server.
360 Flags can be
362 override,[non-]prescriptive,proxy-authz-[non-]critical
364 When the override flag is used, identity assertion takes place
366 even when the database is authorizing for the identity of the
367 client, i.e. after binding with the provided identity, and thus
368 authenticating it, the proxy performs the identity assertion
369 using the configured identity and authentication method.
370 When the prescriptive flag is used (the default), operations
372 fail with inappropriateAuthentication for those identities whose
373 assertion is not allowed by the idassert-authzFrom patterns. If
374 the non-prescriptive flag is used, operations are performed
375 anonymously for those identities whose assertion is not allowed
376 by the idassert-authzFrom patterns.
377 When the proxy-authz-non-critical flag is used (the default),
379 the proxyAuthz control is not marked as critical, in violation
380 of RFC 4370. Use of proxy-authz-critical is recommended.
381 The TLS settings default to the same as the main slapd TLS
383 settings, except for tls_reqcert which defaults to "demand".
384 The identity associated to this directive is also used for
386 privileged operations whenever idassert-bind is defined and
387 acl-bind is not. See acl-bind for details.
388 idle-timeout <time>
391 This directive causes a cached connection to be dropped an
392 recreated after it has been idle for the specified time. The
393 value can be specified as
394 [<d>d][<h>h][<m>m][<s>[s]]
396 where <d>, <h>, <m> and <s> are respectively treated as days,
398 hours, minutes and seconds. If set before any target
399 specification, it affects all targets, unless overridden by any
400 per-target directive.
401 keepalive <idle>:<probes>:<interval>
404 The keepalive parameter sets the values of idle, probes, and
405 interval used to check whether a socket is alive; idle is the
406 number of seconds a connection needs to remain idle before TCP
407 starts sending keepalive probes; probes is the maximum number of
408 keepalive probes TCP should send before dropping the connection;
409 interval is interval in seconds between individual keepalive
410 probes. Only some systems support the customization of these
411 values; the keepalive parameter is ignored otherwise, and
412 system-wide settings are used.
413 map {attribute|objectclass} [<local name>|*] {<foreign name>|*}
416 This maps object classes and attributes as in the LDAP backend.
417 See slapd-ldap(5).
418 network-timeout <time>
421 Sets the network timeout value after which poll(2)/select(2)
422 following a connect(2) returns in case of no activity. The
423 value is in seconds, and it can be specified as for
424 idle-timeout. If set before any target specification, it
425 affects all targets, unless overridden by any per-target
426 directive.
427 nretries {forever|never|<nretries>}
430 This directive defines how many times a bind should be retried
431 in case of temporary failure in contacting a target. If defined
432 before any target specification, it applies to all targets (by
433 default, 3 times); the global value can be overridden by
434 redefinitions inside each target specification.
435 rewrite* ...
438 The rewrite options are described in the "REWRITING" section.
439 subtree-{exclude|include} <rule>
442 This directive allows to indicate what subtrees are actually
443 served by a target. The syntax of the supported rules is
444 <rule>: [dn[.<style>]:]<pattern>
446 <style>: subtree|children|regex
448 When <style> is either subtree or children the <pattern> is a DN
450 that must be within the naming context served by the target.
451 When <style> is regex the <pattern> is a regex(5) pattern. If
452 the dn.<style>: prefix is omitted, dn.subtree: is implicitly
453 assumed for backward compatibility.
454 In the subtree-exclude form if the request DN matches at least
456 one rule, the target is not considered while fulfilling the
457 request; otherwise, the target is considered based on the value
458 of the request DN. When the request is a search, also the scope
459 is considered.
460 In the subtree-include form if the request DN matches at least
462 one rule, the target is considered while fulfilling the request;
463 otherwise the target is ignored.
464 | match | exclude |
467 +---------+---------+-------------------+
468 | T | T | not candidate |
469 | F | T | continue checking |
470 +---------+---------+-------------------+
471 | T | F | candidate |
472 | F | F | not candidate |
473 +---------+---------+-------------------+
474 There may be multiple occurrences of the subtree-exclude or
476 subtree-include directive for each of the targets, but they are
477 mutually exclusive.
478 suffixmassage <virtual naming context> <real naming context>
481 All the directives starting with "rewrite" refer to the rewrite
482 engine that has been added to slapd. The "suffixmassage"
483 directive was introduced in the LDAP backend to allow suffix
484 massaging while proxying. It has been obsoleted by the
485 rewriting tools. However, both for backward compatibility and
486 for ease of configuration when simple suffix massage is
487 required, it has been preserved. It wraps the basic rewriting
488 instructions that perform suffix massaging. See the "REWRITING"
489 section for a detailed list of the rewrite rules it implies.
490 t-f-support {NO|yes|discover}
493 enable if the remote server supports absolute filters (see RFC
494 4526 for details). If set to discover, support is detected by
495 reading the remote server's root DSE. If set before any target
496 specification, it affects all targets, unless overridden by any
497 per-target directive.
498 timeout [<op>=]<val> [...]
501 This directive allows to set per-operation timeouts. Operations
502 can be
503 <op> ::= bind, add, delete, modrdn, modify, compare, search
505 The overall duration of the search operation is controlled
507 either by the timelimit parameter or by server-side enforced
508 time limits (see timelimit and limits in slapd.conf(5) for
509 details). This timeout parameter controls how long the target
510 can be irresponsive before the operation is aborted. Timeout is
511 meaningless for the remaining operations, unbind and abandon,
512 which do not imply any response, while it is not yet implemented
513 in currently supported extended operations. If no operation is
514 specified, the timeout val affects all supported operations. If
515 specified before any target definition, it affects all targets
516 unless overridden by per-target directives.
517 Note: if the timeout is exceeded, the operation is cancelled
519 (according to the cancel directive); the protocol does not
520 provide any means to rollback operations, so the client will not
521 be notified about the result of the operation, which may
522 eventually succeeded or not. In case the timeout is exceeded
523 during a bind operation, the connection is destroyed, according
524 to RFC4511.
525 tls {[try-]start|[try-]propagate}
528 execute the StartTLS extended operation when the connection is
529 initialized; only works if the URI directive protocol scheme is
530 not ldaps://. propagate issues the StartTLS operation only if
531 the original connection did. The try- prefix instructs the
532 proxy to continue operations if the StartTLS operation failed;
533 its use is highly deprecated. If set before any target
534 specification, it affects all targets, unless overridden by any
535 per-target directive.
536
539 A powerful (and in some sense dangerous) rewrite engine has been added
540 to both the LDAP and Meta backends. While the former can gain limited
541 beneficial effects from rewriting stuff, the latter can become an
542 amazingly powerful tool.
543 Consider a couple of scenarios first.
545 1) Two directory servers share two levels of naming context; say
547 "dc=a,dc=foo,dc=com" and "dc=b,dc=foo,dc=com". Then, an unambiguous
548 Meta database can be configured as:
549 database meta
551 suffix "dc=foo,dc=com"
552 uri "ldap://a.foo.com/dc=a,dc=foo,dc=com"
553 uri "ldap://b.foo.com/dc=b,dc=foo,dc=com"
554 Operations directed to a specific target can be easily resolved because
556 there are no ambiguities. The only operation that may resolve to
557 multiple targets is a search with base "dc=foo,dc=com" and scope at
558 least "one", which results in spawning two searches to the targets.
559 2a) Two directory servers don't share any portion of naming context,
561 but they'd present as a single DIT [Caveat: uniqueness of (massaged)
562 entries among the two servers is assumed; integrity checks risk to
563 incur in excessive overhead and have not been implemented]. Say we
564 have "dc=bar,dc=org" and "o=Foo,c=US", and we'd like them to appear as
565 branches of "dc=foo,dc=com", say "dc=a,dc=foo,dc=com" and
566 "dc=b,dc=foo,dc=com". Then we need to configure our Meta backend as:
567 database meta
569 suffix "dc=foo,dc=com"
570 uri "ldap://a.bar.com/dc=a,dc=foo,dc=com"
572 suffixmassage "dc=a,dc=foo,dc=com" "dc=bar,dc=org"
573 uri "ldap://b.foo.com/dc=b,dc=foo,dc=com"
575 suffixmassage "dc=b,dc=foo,dc=com" "o=Foo,c=US"
576 Again, operations can be resolved without ambiguity, although some
578 rewriting is required. Notice that the virtual naming context of each
579 target is a branch of the database's naming context; it is rewritten
580 back and forth when operations are performed towards the target
581 servers. What "back and forth" means will be clarified later.
582 When a search with base "dc=foo,dc=com" is attempted, if the scope is
584 "base" it fails with "no such object"; in fact, the common root of the
585 two targets (prior to massaging) does not exist. If the scope is
586 "one", both targets are contacted with the base replaced by each
587 target's base; the scope is derated to "base". In general, a scope
588 "one" search is honored, and the scope is derated, only when the
589 incoming base is at most one level lower of a target's naming context
590 (prior to massaging).
591 Finally, if the scope is "sub" the incoming base is replaced by each
593 target's unmassaged naming context, and the scope is not altered.
594 2b) Consider the above reported scenario with the two servers sharing
596 the same naming context:
597 database meta
599 suffix "dc=foo,dc=com"
600 uri "ldap://a.bar.com/dc=foo,dc=com"
602 suffixmassage "dc=foo,dc=com" "dc=bar,dc=org"
603 uri "ldap://b.foo.com/dc=foo,dc=com"
605 suffixmassage "dc=foo,dc=com" "o=Foo,c=US"
606 All the previous considerations hold, except that now there is no way
608 to unambiguously resolve a DN. In this case, all the operations that
609 require an unambiguous target selection will fail unless the DN is
610 already cached or a default target has been set. Practical
611 configurations may result as a combination of all the above scenarios.
612
614 Note on ACLs: at present you may add whatever ACL rule you desire to to
615 the Meta (and LDAP) backends. However, the meaning of an ACL on a
616 proxy may require some considerations. Two philosophies may be
617 considered:
618 a) the remote server dictates the permissions; the proxy simply passes
620 back what it gets from the remote server.
621 b) the remote server unveils "everything"; the proxy is responsible for
623 protecting data from unauthorized access.
624 Of course the latter sounds unreasonable, but it is not. It is
626 possible to imagine scenarios in which a remote host discloses data
627 that can be considered "public" inside an intranet, and a proxy that
628 connects it to the internet may impose additional constraints. To this
629 purpose, the proxy should be able to comply with all the ACL matching
630 criteria that the server supports. This has been achieved with regard
631 to all the criteria supported by slapd except a special subtle case
632 (please file an ITS if you can find other exceptions:
633 <http://www.openldap.org/its/>). The rule
634 access to dn="<dn>" attrs=<attr>
636 by dnattr=<dnattr> read
637 by * none
638 cannot be matched iff the attribute that is being requested, <attr>, is
640 NOT <dnattr>, and the attribute that determines membership, <dnattr>,
641 has not been requested (e.g. in a search)
642 In fact this ACL is resolved by slapd using the portion of entry it
644 retrieved from the remote server without requiring any further
645 intervention of the backend, so, if the <dnattr> attribute has not been
646 fetched, the match cannot be assessed because the attribute is not
647 present, not because no value matches the requirement!
648 Note on ACLs and attribute mapping: ACLs are applied to the mapped
650 attributes; for instance, if the attribute locally known as "foo" is
651 mapped to "bar" on a remote server, then local ACLs apply to attribute
652 "foo" and are totally unaware of its remote name. The remote server
653 will check permissions for "bar", and the local server will possibly
654 enforce additional restrictions to "foo".
655
657 A string is rewritten according to a set of rules, called a `rewrite
658 context'. The rules are based on POSIX (''extended'') regular
659 expressions (regex) with substring matching; basic variable
660 substitution and map resolution of substrings is allowed by specific
661 mechanisms detailed in the following. The behavior of pattern
662 matching/substitution can be altered by a set of flags.
663 The underlying concept is to build a lightweight rewrite module for the
665 slapd server (initially dedicated to the LDAP backend).
666
668 An incoming string is matched against a set of rules. Rules are made
669 of a regex match pattern, a substitution pattern and a set of actions,
670 described by a set of flags. In case of match a string rewriting is
671 performed according to the substitution pattern that allows to refer to
672 substrings matched in the incoming string. The actions, if any, are
673 finally performed. The substitution pattern allows map resolution of
674 substrings. A map is a generic object that maps a substitution pattern
675 to a value. The flags are divided in "Pattern matching Flags" and
676 "Action Flags"; the former alter the regex match pattern behavior while
677 the latter alter the action that is taken after substitution.
678
680 `C' honors case in matching (default is case insensitive)
681 `R' use POSIX ''basic'' regular expressions (default is
683 ''extended'')
684 `M{n}' allow no more than n recursive passes for a specific rule; does
686 not alter the max total count of passes, so it can only enforce
687 a stricter limit for a specific rule.
688
690 `:' apply the rule once only (default is recursive)
691 `@' stop applying rules in case of match; the current rule is still
693 applied recursively; combine with `:' to apply the current rule
694 only once and then stop.
695 `#' stop current operation if the rule matches, and issue an
697 `unwilling to perform' error.
698 `G{n}' jump n rules back and forth (watch for loops!). Note that
700 `G{1}' is implicit in every rule.
701 `I' ignores errors in rule; this means, in case of error, e.g.
703 issued by a map, the error is treated as a missed match. The
704 `unwilling to perform' is not overridden.
705 `U{n}' uses n as return code if the rule matches; the flag does not
707 alter the recursive behavior of the rule, so, to have it
708 performed only once, it must be used in combination with `:',
709 e.g. `:U{16}' returns the value `16' after exactly one
710 execution of the rule, if the pattern matches. As a
711 consequence, its behavior is equivalent to `@', with the return
712 code set to n; or, in other words, `@' is equivalent to `U{0}'.
713 By convention, the freely available codes are above 16 included;
714 the others are reserved.
715 The ordering of the flags can be significant. For instance: `IG{2}'
717 means ignore errors and jump two lines ahead both in case of match and
718 in case of error, while `G{2}I' means ignore errors, but jump two lines
719 ahead only in case of match.
720 More flags (mainly Action Flags) will be added as needed.
722
724 See regex(7) and/or re_format(7).
725
727 Everything starting with `%' requires substitution;
728 the only obvious exception is `%%', which is left as is;
730 the basic substitution is `%d', where `d' is a digit; 0 means the whole
732 string, while 1-9 is a submatch;
733 a `%' followed by a `{' invokes an advanced substitution. The pattern
735 is:
736 `%' `{' [ <op> ] <name> `(' <substitution> `)' `}'
738 where <name> must be a legal name for the map, i.e.
740 <name> ::= [a-z][a-z0-9]* (case insensitive)
742 <op> ::= `>' `|' `&' `&&' `*' `**' `$'
743 and <substitution> must be a legal substitution pattern, with no limits
745 on the nesting level.
746 The operators are:
748 > sub context invocation; <name> must be a legal, already defined
750 rewrite context name
751 | external command invocation; <name> must refer to a legal,
753 already defined command name (NOT IMPL.)
754 & variable assignment; <name> defines a variable in the running
756 operation structure which can be dereferenced later; operator &
757 assigns a variable in the rewrite context scope; operator &&
758 assigns a variable that scopes the entire session, e.g. its
759 value can be dereferenced later by other rewrite contexts
760 * variable dereferencing; <name> must refer to a variable that is
762 defined and assigned for the running operation; operator *
763 dereferences a variable scoping the rewrite context; operator **
764 dereferences a variable scoping the whole session, e.g. the
765 value is passed across rewrite contexts
766 $ parameter dereferencing; <name> must refer to an existing
768 parameter; the idea is to make some run-time parameters set by
769 the system available to the rewrite engine, as the client host
770 name, the bind DN if any, constant parameters initialized at
771 config time, and so on; no parameter is currently set by either
772 back-ldap or back-meta, but constant parameters can be defined
773 in the configuration file by using the rewriteParam directive.
774 Substitution escaping has been delegated to the `%' symbol, which is
776 used instead of `\' in string substitution patterns because `\' is
777 already escaped by slapd's low level parsing routines; as a
778 consequence, regex escaping requires two `\' symbols, e.g.
779 `.*\.foo\.bar' must be written as `.*\\.foo\\.bar'.
780
782 A rewrite context is a set of rules which are applied in sequence. The
783 basic idea is to have an application initialize a rewrite engine (think
784 of Apache's mod_rewrite ...) with a set of rewrite contexts; when
785 string rewriting is required, one invokes the appropriate rewrite
786 context with the input string and obtains the newly rewritten one if no
787 errors occur.
788 Each basic server operation is associated to a rewrite context; they
790 are divided in two main groups: client -> server and server -> client
791 rewriting.
792 client -> server:
794 (default) if defined and no specific context
796 is available
797 bindDN bind
798 searchBase search
799 searchFilter search
800 searchFilterAttrDN search
801 compareDN compare
802 compareAttrDN compare AVA
803 addDN add
804 addAttrDN add AVA
805 modifyDN modify
806 modifyAttrDN modify AVA
807 modrDN modrdn
808 newSuperiorDN modrdn
809 deleteDN delete
810 exopPasswdDN password modify extended operation DN if proxy
811 server -> client:
813 searchResult search (only if defined; no default;
815 acts on DN and DN-syntax attributes
816 of search results)
817 searchAttrDN search AVA
818 matchedDN all ops (only if applicable)
819
821 rewriteEngine { on | off }
822 If `on', the requested rewriting is performed; if `off', no
823 rewriting takes place (an easy way to stop rewriting without
824 altering too much the configuration file).
825 rewriteContext <context name> [ alias <aliased context name> ]
827 <Context name> is the name that identifies the context, i.e. the
828 name used by the application to refer to the set of rules it
829 contains. It is used also to reference sub contexts in string
830 rewriting. A context may alias another one. In this case the
831 alias context contains no rule, and any reference to it will
832 result in accessing the aliased one.
833 rewriteRule <regex match pattern> <substitution pattern> [ <flags> ]
835 Determines how a string can be rewritten if a pattern is
836 matched. Examples are reported below.
837
839 rewriteMap <map type> <map name> [ <map attrs> ]
840 Allows to define a map that transforms substring rewriting into
841 something else. The map is referenced inside the substitution
842 pattern of a rule.
843 rewriteParam <param name> <param value>
845 Sets a value with global scope, that can be dereferenced by the
846 command `%{$paramName}'.
847 rewriteMaxPasses <number of passes> [<number of passes per rule>]
849 Sets the maximum number of total rewriting passes that can be
850 performed in a single rewrite operation (to avoid loops). A
851 safe default is set to 100; note that reaching this limit is
852 still treated as a success; recursive invocation of rules is
853 simply interrupted. The count applies to the rewriting
854 operation as a whole, not to any single rule; an optional per-
855 rule limit can be set. This limit is overridden by setting
856 specific per-rule limits with the `M{n}' flag.
857
859 # set to `off' to disable rewriting
860 rewriteEngine on
861 # the rules the "suffixmassage" directive implies
863 rewriteEngine on
864 # all dataflow from client to server referring to DNs
865 rewriteContext default
866 rewriteRule "(.*)<virtualnamingcontext>$" "%1<realnamingcontext>" ":"
867 # empty filter rule
868 rewriteContext searchFilter
869 # all dataflow from server to client
870 rewriteContext searchResult
871 rewriteRule "(.*)<realnamingcontext>$" "%1<virtualnamingcontext>" ":"
872 rewriteContext searchAttrDN alias searchResult
873 rewriteContext matchedDN alias searchResult
874 # Everything defined here goes into the `default' context.
876 # This rule changes the naming context of anything sent
877 # to `dc=home,dc=net' to `dc=OpenLDAP, dc=org'
878 rewriteRule "(.*)dc=home,[ ]?dc=net"
880 "%1dc=OpenLDAP, dc=org" ":"
881 # since a pretty/normalized DN does not include spaces
883 # after rdn separators, e.g. `,', this rule suffices:
884 rewriteRule "(.*)dc=home,dc=net"
886 "%1dc=OpenLDAP,dc=org" ":"
887 # Start a new context (ends input of the previous one).
889 # This rule adds blanks between DN parts if not present.
890 rewriteContext addBlanks
891 rewriteRule "(.*),([^ ].*)" "%1, %2"
892 # This one eats blanks
894 rewriteContext eatBlanks
895 rewriteRule "(.*),[ ](.*)" "%1,%2"
896 # Here control goes back to the default rewrite
898 # context; rules are appended to the existing ones.
899 # anything that gets here is piped into rule `addBlanks'
900 rewriteContext default
901 rewriteRule ".*" "%{>addBlanks(%0)}" ":"
902 # Rewrite the search base according to `default' rules.
904 rewriteContext searchBase alias default
905 # Search results with OpenLDAP DN are rewritten back with
907 # `dc=home,dc=net' naming context, with spaces eaten.
908 rewriteContext searchResult
909 rewriteRule "(.*[^ ]?)[ ]?dc=OpenLDAP,[ ]?dc=org"
910 "%{>eatBlanks(%1)}dc=home,dc=net" ":"
911 # Bind with email instead of full DN: we first need
913 # an ldap map that turns attributes into a DN (the
914 # argument used when invoking the map is appended to
915 # the URI and acts as the filter portion)
916 rewriteMap ldap attr2dn "ldap://host/dc=my,dc=org?dn?sub"
917 # Then we need to detect DN made up of a single email,
919 # e.g. `mail=someone@example.com'; note that the rule
920 # in case of match stops rewriting; in case of error,
921 # it is ignored. In case we are mapping virtual
922 # to real naming contexts, we also need to rewrite
923 # regular DNs, because the definition of a bindDn
924 # rewrite context overrides the default definition.
925 rewriteContext bindDN
926 rewriteRule "^mail=[^,]+@[^,]+$" "%{attr2dn(%0)}" ":@I"
927 # This is a rather sophisticated example. It massages a
929 # search filter in case who performs the search has
930 # administrative privileges. First we need to keep
931 # track of the bind DN of the incoming request, which is
932 # stored in a variable called `binddn' with session scope,
933 # and left in place to allow regular binding:
934 rewriteContext bindDN
935 rewriteRule ".+" "%{&&binddn(%0)}%0" ":"
936 # A search filter containing `uid=' is rewritten only
938 # if an appropriate DN is bound.
939 # To do this, in the first rule the bound DN is
940 # dereferenced, while the filter is decomposed in a
941 # prefix, in the value of the `uid=<arg>' AVA, and
942 # in a suffix. A tag `<>' is appended to the DN.
943 # If the DN refers to an entry in the `ou=admin' subtree,
944 # the filter is rewritten OR-ing the `uid=<arg>' with
945 # `cn=<arg>'; otherwise it is left as is. This could be
946 # useful, for instance, to allow apache's auth_ldap-1.4
947 # module to authenticate users with both `uid' and
948 # `cn', but only if the request comes from a possible
949 # `cn=Web auth,ou=admin,dc=home,dc=net' user.
950 rewriteContext searchFilter
951 rewriteRule "(.*\\()uid=([a-z0-9_]+)(\\).*)"
952 "%{**binddn}<>%{&prefix(%1)}%{&arg(%2)}%{&suffix(%3)}"
953 ":I"
954 rewriteRule "[^,]+,ou=admin,dc=home,dc=net"
955 "%{*prefix}|(uid=%{*arg})(cn=%{*arg})%{*suffix}" ":@I"
956 rewriteRule ".*<>" "%{*prefix}uid=%{*arg}%{*suffix}" ":"
957 # This example shows how to strip unwanted DN-valued
959 # attribute values from a search result; the first rule
960 # matches DN values below "ou=People,dc=example,dc=com";
961 # in case of match the rewriting exits successfully.
962 # The second rule matches everything else and causes
963 # the value to be rejected.
964 rewriteContext searchResult
965 rewriteRule ".*,ou=People,dc=example,dc=com" "%0" ":@"
966 rewriteRule ".*" "" "#"
967
969 In case the rewritten DN is an LDAP URI, the operation is initiated
970 towards the host[:port] indicated in the uri, if it does not refer to
971 the local server. E.g.:
972 rewriteRule '^cn=root,.*' '%0' 'G{3}'
974 rewriteRule '^cn=[a-l].*' 'ldap://ldap1.my.org/%0' ':@'
975 rewriteRule '^cn=[m-z].*' 'ldap://ldap2.my.org/%0' ':@'
976 rewriteRule '.*' 'ldap://ldap3.my.org/%0' ':@'
977 (Rule 1 is simply there to illustrate the `G{n}' action; it could have
979 been written:
980 rewriteRule '^cn=root,.*' 'ldap://ldap3.my.org/%0' ':@'
982 with the advantage of saving one rewrite pass ...)
984
987 The meta backend does not honor all ACL semantics as described in
988 slapd.access(5). In general, access checking is delegated to the
989 remote server(s). Only read (=r) access to the entry pseudo-attribute
990 and to the other attribute values of the entries returned by the search
991 operation is honored, which is performed by the frontend.
992
995 The proxy cache overlay allows caching of LDAP search requests
996 (queries) in a local database. See slapo-pcache(5) for details.
997
1000 The following statements have been deprecated and should no longer be
1001 used.
1002 pseudorootdn <substitute DN in case of rootdn bind>
1005 Use idassert-bind instead.
1006 pseudorootpw <substitute password in case of rootdn bind>
1009 Use idassert-bind instead.
1010
1015 /etc/openldap/slapd.conf
1016 default slapd configuration file
1017
1019 slapd.conf(5), slapd-ldap(5), slapo-pcache(5), slapd(8), regex(7),
1020 re_format(7).
1021
1023 Pierangelo Masarati, based on back-ldap by Howard Chu
1024OpenLDAP 2.4.40 2014/09/20 SLAPD-META(5)