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 default-target [<target>]
252 The "default-target" directive can also be used during target
253 specification. With no arguments it marks the current target as
254 the default. The optional number marks target <target> as the
255 default one, starting from 1. Target <target> must be defined.
256 idassert-authzFrom <authz-regexp>
259 if defined, selects what local identities are authorized to
260 exploit the identity assertion feature. The string <authz-reg‐
261 exp> follows the rules defined for the authzFrom attribute. See
262 slapd.conf(5), section related to authz-policy, for details on
263 the syntax of this field.
264 idassert-bind bindmethod=none|simple|sasl [binddn=<simple DN>]
267 [credentials=<simple password>] [saslmech=<SASL mech>]
268 [secprops=<properties>] [realm=<realm>] [authcId=<authentication
269 ID>] [authzId=<authorization ID>] [authz={native|proxyauthz}]
270 [mode=<mode>] [flags=<flags>] [starttls=no|yes|critical]
271 [tls_cert=<file>] [tls_key=<file>] [tls_cacert=<file>]
272 [tls_cacertdir=<path>] [tls_reqcert=never|allow|try|demand]
273 [tls_ciphersuite=<ciphers>] [tls_protocol_min=<version>]
274 [tls_crlcheck=none|peer|all]
275 Allows to define the parameters of the authentication method
276 that is internally used by the proxy to authorize connections
277 that are authenticated by other databases. The identity defined
278 by this directive, according to the properties associated to the
279 authentication method, is supposed to have auth access on the
280 target server to attributes used on the proxy for authentication
281 and authorization, and to be allowed to authorize the users.
282 This requires to have proxyAuthz privileges on a wide set of
283 DNs, e.g. authzTo=dn.subtree:"", and the remote server to have
284 authz-policy set to to or both. See slapd.conf(5) for details
285 on these statements and for remarks and drawbacks about their
286 usage. The supported bindmethods are
287 none|simple|sasl
289 where none is the default, i.e. no identity assertion is
291 performed.
292 The authz parameter is used to instruct the SASL bind to exploit
294 native SASL authorization, if available; since connections are
295 cached, this should only be used when authorizing with a fixed
296 identity (e.g. by means of the authzDN or authzID parameters).
297 Otherwise, the default proxyauthz is used, i.e. the proxyAuthz
298 control (Proxied Authorization, RFC 4370) is added to all
299 operations.
300 The supported modes are:
302 <mode> := {legacy|anonymous|none|self}
304 If <mode> is not present, and authzId is given, the proxy always
306 authorizes that identity. <authorization ID> can be
307 u:<user>
309 [dn:]<DN>
311 The former is supposed to be expanded by the remote server
313 according to the authz rules; see slapd.conf(5) for details. In
314 the latter case, whether or not the dn: prefix is present, the
315 string must pass DN validation and normalization.
316 The default mode is legacy, which implies that the proxy will
318 either perform a simple bind as the authcDN or a SASL bind as
319 the authcID and assert the client's identity when it is not
320 anonymous. Direct binds are always proxied. The other modes
321 imply that the proxy will always either perform a simple bind as
322 the authcDN or a SASL bind as the authcID, unless restricted by
323 idassert-authzFrom rules (see below), in which case the
324 operation will fail; eventually, it will assert some other
325 identity according to <mode>. Other identity assertion modes
326 are anonymous and self, which respectively mean that the empty
327 or the client's identity will be asserted; none, which means
328 that no proxyAuthz control will be used, so the authcDN or the
329 authcID identity will be asserted. For all modes that require
330 the use of the proxyAuthz control, on the remote server the
331 proxy identity must have appropriate authzTo permissions, or the
332 asserted identities must have appropriate authzFrom permissions.
333 Note, however, that the ID assertion feature is mostly useful
334 when the asserted identities do not exist on the remote server.
335 Flags can be
337 override,[non-]prescriptive,proxy-authz-[non-]critical
339 When the override flag is used, identity assertion takes place
341 even when the database is authorizing for the identity of the
342 client, i.e. after binding with the provided identity, and thus
343 authenticating it, the proxy performs the identity assertion
344 using the configured identity and authentication method.
345 When the prescriptive flag is used (the default), operations
347 fail with inappropriateAuthentication for those identities whose
348 assertion is not allowed by the idassert-authzFrom patterns. If
349 the non-prescriptive flag is used, operations are performed
350 anonymously for those identities whose assertion is not allowed
351 by the idassert-authzFrom patterns.
352 When the proxy-authz-non-critical flag is used (the default),
354 the proxyAuthz control is not marked as critical, in violation
355 of RFC 4370. Use of proxy-authz-critical is recommended.
356 The TLS settings default to the same as the main slapd TLS
358 settings, except for tls_reqcert which defaults to "demand".
359 The identity associated to this directive is also used for
361 privileged operations whenever idassert-bind is defined and
362 acl-bind is not. See acl-bind for details.
363 idle-timeout <time>
366 This directive causes a cached connection to be dropped an
367 recreated after it has been idle for the specified time. The
368 value can be specified as
369 [<d>d][<h>h][<m>m][<s>[s]]
371 where <d>, <h>, <m> and <s> are respectively treated as days,
373 hours, minutes and seconds. If set before any target
374 specification, it affects all targets, unless overridden by any
375 per-target directive.
376 map {attribute|objectclass} [<local name>|*] {<foreign name>|*}
379 This maps object classes and attributes as in the LDAP backend.
380 See slapd-ldap(5).
381 network-timeout <time>
384 Sets the network timeout value after which poll(2)/select(2)
385 following a connect(2) returns in case of no activity. The
386 value is in seconds, and it can be specified as for
387 idle-timeout. If set before any target specification, it
388 affects all targets, unless overridden by any per-target
389 directive.
390 nretries {forever|never|<nretries>}
393 This directive defines how many times a bind should be retried
394 in case of temporary failure in contacting a target. If defined
395 before any target specification, it applies to all targets (by
396 default, 3 times); the global value can be overridden by
397 redefinitions inside each target specification.
398 pseudorootdn <substitute DN in case of rootdn bind>
401 Deprecated; use idassert-bind instead.
402 pseudorootpw <substitute password in case of rootdn bind>
405 Deprecated; use idassert-bind instead.
406 rewrite* ...
409 The rewrite options are described in the "REWRITING" section.
410 subtree-exclude <DN>
413 This directive instructs back-meta to ignore the current target
414 for operations whose requestDN is subordinate to DN. There may
415 be multiple occurrences of the subtree-exclude directive for
416 each of the targets.
417 suffixmassage <virtual naming context> <real naming context>
420 All the directives starting with "rewrite" refer to the rewrite
421 engine that has been added to slapd. The "suffixmassage"
422 directive was introduced in the LDAP backend to allow suffix
423 massaging while proxying. It has been obsoleted by the
424 rewriting tools. However, both for backward compatibility and
425 for ease of configuration when simple suffix massage is
426 required, it has been preserved. It wraps the basic rewriting
427 instructions that perform suffix massaging. See the "REWRITING"
428 section for a detailed list of the rewrite rules it implies.
429 t-f-support {NO|yes|discover}
432 enable if the remote server supports absolute filters (see
433 draft-zeilenga-ldap-t-f for details). If set to discover,
434 support is detected by reading the remote server's root DSE. If
435 set before any target specification, it affects all targets,
436 unless overridden by any per-target directive.
437 timeout [<op>=]<val> [...]
440 This directive allows to set per-operation timeouts. Operations
441 can be
442 <op> ::= bind, add, delete, modrdn, modify, compare, search
444 The overall duration of the search operation is controlled
446 either by the timelimit parameter or by server-side enforced
447 time limits (see timelimit and limits in slapd.conf(5) for
448 details). This timeout parameter controls how long the target
449 can be irresponsive before the operation is aborted. Timeout is
450 meaningless for the remaining operations, unbind and abandon,
451 which do not imply any response, while it is not yet implemented
452 in currently supported extended operations. If no operation is
453 specified, the timeout val affects all supported operations. If
454 specified before any target definition, it affects all targets
455 unless overridden by per-target directives.
456 Note: if the timeout is exceeded, the operation is cancelled
458 (according to the cancel directive); the protocol does not
459 provide any means to rollback operations, so the client will not
460 be notified about the result of the operation, which may
461 eventually succeeded or not. In case the timeout is exceeded
462 during a bind operation, the connection is destroyed, according
463 to RFC4511.
464 tls {[try-]start|[try-]propagate}
467 execute the StartTLS extended operation when the connection is
468 initialized; only works if the URI directive protocol scheme is
469 not ldaps://. propagate issues the StartTLS operation only if
470 the original connection did. The try- prefix instructs the
471 proxy to continue operations if the StartTLS operation failed;
472 its use is highly deprecated. If set before any target
473 specification, it affects all targets, unless overridden by any
474 per-target directive.
475
478 A powerful (and in some sense dangerous) rewrite engine has been added
479 to both the LDAP and Meta backends. While the former can gain limited
480 beneficial effects from rewriting stuff, the latter can become an
481 amazingly powerful tool.
482 Consider a couple of scenarios first.
484 1) Two directory servers share two levels of naming context; say
486 "dc=a,dc=foo,dc=com" and "dc=b,dc=foo,dc=com". Then, an unambiguous
487 Meta database can be configured as:
488 database meta
490 suffix "dc=foo,dc=com"
491 uri "ldap://a.foo.com/dc=a,dc=foo,dc=com"
492 uri "ldap://b.foo.com/dc=b,dc=foo,dc=com"
493 Operations directed to a specific target can be easily resolved because
495 there are no ambiguities. The only operation that may resolve to
496 multiple targets is a search with base "dc=foo,dc=com" and scope at
497 least "one", which results in spawning two searches to the targets.
498 2a) Two directory servers don't share any portion of naming context,
500 but they'd present as a single DIT [Caveat: uniqueness of (massaged)
501 entries among the two servers is assumed; integrity checks risk to
502 incur in excessive overhead and have not been implemented]. Say we
503 have "dc=bar,dc=org" and "o=Foo,c=US", and we'd like them to appear as
504 branches of "dc=foo,dc=com", say "dc=a,dc=foo,dc=com" and
505 "dc=b,dc=foo,dc=com". Then we need to configure our Meta backend as:
506 database meta
508 suffix "dc=foo,dc=com"
509 uri "ldap://a.bar.com/dc=a,dc=foo,dc=com"
511 suffixmassage "dc=a,dc=foo,dc=com" "dc=bar,dc=org"
512 uri "ldap://b.foo.com/dc=b,dc=foo,dc=com"
514 suffixmassage "dc=b,dc=foo,dc=com" "o=Foo,c=US"
515 Again, operations can be resolved without ambiguity, although some
517 rewriting is required. Notice that the virtual naming context of each
518 target is a branch of the database's naming context; it is rewritten
519 back and forth when operations are performed towards the target
520 servers. What "back and forth" means will be clarified later.
521 When a search with base "dc=foo,dc=com" is attempted, if the scope is
523 "base" it fails with "no such object"; in fact, the common root of the
524 two targets (prior to massaging) does not exist. If the scope is
525 "one", both targets are contacted with the base replaced by each
526 target's base; the scope is derated to "base". In general, a scope
527 "one" search is honored, and the scope is derated, only when the
528 incoming base is at most one level lower of a target's naming context
529 (prior to massaging).
530 Finally, if the scope is "sub" the incoming base is replaced by each
532 target's unmassaged naming context, and the scope is not altered.
533 2b) Consider the above reported scenario with the two servers sharing
535 the same naming context:
536 database meta
538 suffix "dc=foo,dc=com"
539 uri "ldap://a.bar.com/dc=foo,dc=com"
541 suffixmassage "dc=foo,dc=com" "dc=bar,dc=org"
542 uri "ldap://b.foo.com/dc=foo,dc=com"
544 suffixmassage "dc=foo,dc=com" "o=Foo,c=US"
545 All the previous considerations hold, except that now there is no way
547 to unambiguously resolve a DN. In this case, all the operations that
548 require an unambiguous target selection will fail unless the DN is
549 already cached or a default target has been set. Practical
550 configurations may result as a combination of all the above scenarios.
551
553 Note on ACLs: at present you may add whatever ACL rule you desire to to
554 the Meta (and LDAP) backends. However, the meaning of an ACL on a
555 proxy may require some considerations. Two philosophies may be
556 considered:
557 a) the remote server dictates the permissions; the proxy simply passes
559 back what it gets from the remote server.
560 b) the remote server unveils "everything"; the proxy is responsible for
562 protecting data from unauthorized access.
563 Of course the latter sounds unreasonable, but it is not. It is
565 possible to imagine scenarios in which a remote host discloses data
566 that can be considered "public" inside an intranet, and a proxy that
567 connects it to the internet may impose additional constraints. To this
568 purpose, the proxy should be able to comply with all the ACL matching
569 criteria that the server supports. This has been achieved with regard
570 to all the criteria supported by slapd except a special subtle case
571 (please drop me a note if you can find other exceptions:
572 <ando@openldap.org>). The rule
573 access to dn="<dn>" attrs=<attr>
575 by dnattr=<dnattr> read
576 by * none
577 cannot be matched iff the attribute that is being requested, <attr>, is
579 NOT <dnattr>, and the attribute that determines membership, <dnattr>,
580 has not been requested (e.g. in a search)
581 In fact this ACL is resolved by slapd using the portion of entry it
583 retrieved from the remote server without requiring any further
584 intervention of the backend, so, if the <dnattr> attribute has not been
585 fetched, the match cannot be assessed because the attribute is not
586 present, not because no value matches the requirement!
587 Note on ACLs and attribute mapping: ACLs are applied to the mapped
589 attributes; for instance, if the attribute locally known as "foo" is
590 mapped to "bar" on a remote server, then local ACLs apply to attribute
591 "foo" and are totally unaware of its remote name. The remote server
592 will check permissions for "bar", and the local server will possibly
593 enforce additional restrictions to "foo".
594
596 A string is rewritten according to a set of rules, called a `rewrite
597 context'. The rules are based on POSIX (''extended'') regular
598 expressions (regex) with substring matching; basic variable
599 substitution and map resolution of substrings is allowed by specific
600 mechanisms detailed in the following. The behavior of pattern
601 matching/substitution can be altered by a set of flags.
602 The underlying concept is to build a lightweight rewrite module for the
604 slapd server (initially dedicated to the LDAP backend).
605
607 An incoming string is matched against a set of rules. Rules are made
608 of a regex match pattern, a substitution pattern and a set of actions,
609 described by a set of flags. In case of match a string rewriting is
610 performed according to the substitution pattern that allows to refer to
611 substrings matched in the incoming string. The actions, if any, are
612 finally performed. The substitution pattern allows map resolution of
613 substrings. A map is a generic object that maps a substitution pattern
614 to a value. The flags are divided in "Pattern matching Flags" and
615 "Action Flags"; the former alter the regex match pattern behavior while
616 the latter alter the action that is taken after substitution.
617
619 `C' honors case in matching (default is case insensitive)
620 `R' use POSIX ''basic'' regular expressions (default is
622 ''extended'')
623 `M{n}' allow no more than n recursive passes for a specific rule; does
625 not alter the max total count of passes, so it can only enforce
626 a stricter limit for a specific rule.
627
629 `:' apply the rule once only (default is recursive)
630 `@' stop applying rules in case of match; the current rule is still
632 applied recursively; combine with `:' to apply the current rule
633 only once and then stop.
634 `#' stop current operation if the rule matches, and issue an
636 `unwilling to perform' error.
637 `G{n}' jump n rules back and forth (watch for loops!). Note that
639 `G{1}' is implicit in every rule.
640 `I' ignores errors in rule; this means, in case of error, e.g.
642 issued by a map, the error is treated as a missed match. The
643 `unwilling to perform' is not overridden.
644 `U{n}' uses n as return code if the rule matches; the flag does not
646 alter the recursive behavior of the rule, so, to have it
647 performed only once, it must be used in combination with `:',
648 e.g. `:U{16}' returns the value `16' after exactly one
649 execution of the rule, if the pattern matches. As a
650 consequence, its behavior is equivalent to `@', with the return
651 code set to n; or, in other words, `@' is equivalent to `U{0}'.
652 By convention, the freely available codes are above 16 included;
653 the others are reserved.
654 The ordering of the flags can be significant. For instance: `IG{2}'
656 means ignore errors and jump two lines ahead both in case of match and
657 in case of error, while `G{2}I' means ignore errors, but jump two lines
658 ahead only in case of match.
659 More flags (mainly Action Flags) will be added as needed.
661
663 See regex(7) and/or re_format(7).
664
666 Everything starting with `%' requires substitution;
667 the only obvious exception is `%%', which is left as is;
669 the basic substitution is `%d', where `d' is a digit; 0 means the whole
671 string, while 1-9 is a submatch;
672 a `%' followed by a `{' invokes an advanced substitution. The pattern
674 is:
675 `%' `{' [ <op> ] <name> `(' <substitution> `)' `}'
677 where <name> must be a legal name for the map, i.e.
679 <name> ::= [a-z][a-z0-9]* (case insensitive)
681 <op> ::= `>' `|' `&' `&&' `*' `**' `$'
682 and <substitution> must be a legal substitution pattern, with no limits
684 on the nesting level.
685 The operators are:
687 > sub context invocation; <name> must be a legal, already defined
689 rewrite context name
690 | external command invocation; <name> must refer to a legal,
692 already defined command name (NOT IMPL.)
693 & variable assignment; <name> defines a variable in the running
695 operation structure which can be dereferenced later; operator &
696 assigns a variable in the rewrite context scope; operator &&
697 assigns a variable that scopes the entire session, e.g. its
698 value can be dereferenced later by other rewrite contexts
699 * variable dereferencing; <name> must refer to a variable that is
701 defined and assigned for the running operation; operator *
702 dereferences a variable scoping the rewrite context; operator **
703 dereferences a variable scoping the whole session, e.g. the
704 value is passed across rewrite contexts
705 $ parameter dereferencing; <name> must refer to an existing
707 parameter; the idea is to make some run-time parameters set by
708 the system available to the rewrite engine, as the client host
709 name, the bind DN if any, constant parameters initialized at
710 config time, and so on; no parameter is currently set by either
711 back-ldap or back-meta, but constant parameters can be defined
712 in the configuration file by using the rewriteParam directive.
713 Substitution escaping has been delegated to the `%' symbol, which is
715 used instead of `\' in string substitution patterns because `\' is
716 already escaped by slapd's low level parsing routines; as a
717 consequence, regex escaping requires two `\' symbols, e.g.
718 `.*\.foo\.bar' must be written as `.*\\.foo\\.bar'.
719
721 A rewrite context is a set of rules which are applied in sequence. The
722 basic idea is to have an application initialize a rewrite engine (think
723 of Apache's mod_rewrite ...) with a set of rewrite contexts; when
724 string rewriting is required, one invokes the appropriate rewrite
725 context with the input string and obtains the newly rewritten one if no
726 errors occur.
727 Each basic server operation is associated to a rewrite context; they
729 are divided in two main groups: client -> server and server -> client
730 rewriting.
731 client -> server:
733 (default) if defined and no specific context
735 is available
736 bindDN bind
737 searchBase search
738 searchFilter search
739 searchFilterAttrDN search
740 compareDN compare
741 compareAttrDN compare AVA
742 addDN add
743 addAttrDN add AVA
744 modifyDN modify
745 modifyAttrDN modify AVA
746 modrDN modrdn
747 newSuperiorDN modrdn
748 deleteDN delete
749 exopPasswdDN password modify extended operation DN if proxy
750 server -> client:
752 searchResult search (only if defined; no default;
754 acts on DN and DN-syntax attributes
755 of search results)
756 searchAttrDN search AVA
757 matchedDN all ops (only if applicable)
758
760 rewriteEngine { on | off }
761 If `on', the requested rewriting is performed; if `off', no
762 rewriting takes place (an easy way to stop rewriting without
763 altering too much the configuration file).
764 rewriteContext <context name> [ alias <aliased context name> ]
766 <Context name> is the name that identifies the context, i.e. the
767 name used by the application to refer to the set of rules it
768 contains. It is used also to reference sub contexts in string
769 rewriting. A context may alias another one. In this case the
770 alias context contains no rule, and any reference to it will
771 result in accessing the aliased one.
772 rewriteRule <regex match pattern> <substitution pattern> [ <flags> ]
774 Determines how a string can be rewritten if a pattern is
775 matched. Examples are reported below.
776
778 rewriteMap <map type> <map name> [ <map attrs> ]
779 Allows to define a map that transforms substring rewriting into
780 something else. The map is referenced inside the substitution
781 pattern of a rule.
782 rewriteParam <param name> <param value>
784 Sets a value with global scope, that can be dereferenced by the
785 command `%{$paramName}'.
786 rewriteMaxPasses <number of passes> [<number of passes per rule>]
788 Sets the maximum number of total rewriting passes that can be
789 performed in a single rewrite operation (to avoid loops). A
790 safe default is set to 100; note that reaching this limit is
791 still treated as a success; recursive invocation of rules is
792 simply interrupted. The count applies to the rewriting
793 operation as a whole, not to any single rule; an optional per-
794 rule limit can be set. This limit is overridden by setting
795 specific per-rule limits with the `M{n}' flag.
796
798 # set to `off' to disable rewriting
799 rewriteEngine on
800 # the rules the "suffixmassage" directive implies
802 rewriteEngine on
803 # all dataflow from client to server referring to DNs
804 rewriteContext default
805 rewriteRule "(.*)<virtualnamingcontext>$" "%1<realnamingcontext>" ":"
806 # empty filter rule
807 rewriteContext searchFilter
808 # all dataflow from server to client
809 rewriteContext searchResult
810 rewriteRule "(.*)<realnamingcontext>$" "%1<virtualnamingcontext>" ":"
811 rewriteContext searchAttrDN alias searchResult
812 rewriteContext matchedDN alias searchResult
813 # Everything defined here goes into the `default' context.
815 # This rule changes the naming context of anything sent
816 # to `dc=home,dc=net' to `dc=OpenLDAP, dc=org'
817 rewriteRule "(.*)dc=home,[ ]?dc=net"
819 "%1dc=OpenLDAP, dc=org" ":"
820 # since a pretty/normalized DN does not include spaces
822 # after rdn separators, e.g. `,', this rule suffices:
823 rewriteRule "(.*)dc=home,dc=net"
825 "%1dc=OpenLDAP,dc=org" ":"
826 # Start a new context (ends input of the previous one).
828 # This rule adds blanks between DN parts if not present.
829 rewriteContext addBlanks
830 rewriteRule "(.*),([^ ].*)" "%1, %2"
831 # This one eats blanks
833 rewriteContext eatBlanks
834 rewriteRule "(.*),[ ](.*)" "%1,%2"
835 # Here control goes back to the default rewrite
837 # context; rules are appended to the existing ones.
838 # anything that gets here is piped into rule `addBlanks'
839 rewriteContext default
840 rewriteRule ".*" "%{>addBlanks(%0)}" ":"
841 # Rewrite the search base according to `default' rules.
843 rewriteContext searchBase alias default
844 # Search results with OpenLDAP DN are rewritten back with
846 # `dc=home,dc=net' naming context, with spaces eaten.
847 rewriteContext searchResult
848 rewriteRule "(.*[^ ]?)[ ]?dc=OpenLDAP,[ ]?dc=org"
849 "%{>eatBlanks(%1)}dc=home,dc=net" ":"
850 # Bind with email instead of full DN: we first need
852 # an ldap map that turns attributes into a DN (the
853 # argument used when invoking the map is appended to
854 # the URI and acts as the filter portion)
855 rewriteMap ldap attr2dn "ldap://host/dc=my,dc=org?dn?sub"
856 # Then we need to detect DN made up of a single email,
858 # e.g. `mail=someone@example.com'; note that the rule
859 # in case of match stops rewriting; in case of error,
860 # it is ignored. In case we are mapping virtual
861 # to real naming contexts, we also need to rewrite
862 # regular DNs, because the definition of a bindDn
863 # rewrite context overrides the default definition.
864 rewriteContext bindDN
865 rewriteRule "^mail=[^,]+@[^,]+$" "%{attr2dn(%0)}" ":@I"
866 # This is a rather sophisticated example. It massages a
868 # search filter in case who performs the search has
869 # administrative privileges. First we need to keep
870 # track of the bind DN of the incoming request, which is
871 # stored in a variable called `binddn' with session scope,
872 # and left in place to allow regular binding:
873 rewriteContext bindDN
874 rewriteRule ".+" "%{&&binddn(%0)}%0" ":"
875 # A search filter containing `uid=' is rewritten only
877 # if an appropriate DN is bound.
878 # To do this, in the first rule the bound DN is
879 # dereferenced, while the filter is decomposed in a
880 # prefix, in the value of the `uid=<arg>' AVA, and
881 # in a suffix. A tag `<>' is appended to the DN.
882 # If the DN refers to an entry in the `ou=admin' subtree,
883 # the filter is rewritten OR-ing the `uid=<arg>' with
884 # `cn=<arg>'; otherwise it is left as is. This could be
885 # useful, for instance, to allow apache's auth_ldap-1.4
886 # module to authenticate users with both `uid' and
887 # `cn', but only if the request comes from a possible
888 # `cn=Web auth,ou=admin,dc=home,dc=net' user.
889 rewriteContext searchFilter
890 rewriteRule "(.*\\()uid=([a-z0-9_]+)(\\).*)"
891 "%{**binddn}<>%{&prefix(%1)}%{&arg(%2)}%{&suffix(%3)}"
892 ":I"
893 rewriteRule "[^,]+,ou=admin,dc=home,dc=net"
894 "%{*prefix}|(uid=%{*arg})(cn=%{*arg})%{*suffix}" ":@I"
895 rewriteRule ".*<>" "%{*prefix}uid=%{*arg}%{*suffix}" ":"
896 # This example shows how to strip unwanted DN-valued
898 # attribute values from a search result; the first rule
899 # matches DN values below "ou=People,dc=example,dc=com";
900 # in case of match the rewriting exits successfully.
901 # The second rule matches everything else and causes
902 # the value to be rejected.
903 rewriteContext searchResult
904 rewriteRule ".*,ou=People,dc=example,dc=com" "%0" ":@"
905 rewriteRule ".*" "" "#"
906
908 In case the rewritten DN is an LDAP URI, the operation is initiated
909 towards the host[:port] indicated in the uri, if it does not refer to
910 the local server. E.g.:
911 rewriteRule '^cn=root,.*' '%0' 'G{3}'
913 rewriteRule '^cn=[a-l].*' 'ldap://ldap1.my.org/%0' ':@'
914 rewriteRule '^cn=[m-z].*' 'ldap://ldap2.my.org/%0' ':@'
915 rewriteRule '.*' 'ldap://ldap3.my.org/%0' ':@'
916 (Rule 1 is simply there to illustrate the `G{n}' action; it could have
918 been written:
919 rewriteRule '^cn=root,.*' 'ldap://ldap3.my.org/%0' ':@'
921 with the advantage of saving one rewrite pass ...)
923
926 The meta backend does not honor all ACL semantics as described in
927 slapd.access(5). In general, access checking is delegated to the
928 remote server(s). Only read (=r) access to the entry pseudo-attribute
929 and to the other attribute values of the entries returned by the search
930 operation is honored, which is performed by the frontend.
931
934 The proxy cache overlay allows caching of LDAP search requests
935 (queries) in a local database. See slapo-pcache(5) for details.
936
938 /etc/openldap/slapd.conf
939 default slapd configuration file
940
942 slapd.conf(5), slapd-ldap(5), slapo-pcache(5), slapd(8), regex(7),
943 re_format(7).
944
946 Pierangelo Masarati, based on back-ldap by Howard Chu
947OpenLDAP 2.4.23 2010/06/30 SLAPD-META(5)