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 in‐
22 tended 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, the slapd(8) threads pa‐
38 rameter may need some tuning. In those cases, unless the multiple tar‐
39 get feature is required, one may consider using slapd-relay(5) instead,
40 which performs the relayed operation internally and thus reuses the
41 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 at‐
60 tributes related to entry creation and modification should not be prox‐
61 ied, as they could be mistakenly written to the target server(s), gen‐
62 erating an error. The current implementation automatically sets last‐
63 mod 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-pool-max <int>
74 This directive defines the maximum size of the privileged con‐
75 nections pool.
76 conn-ttl <time>
79 This directive causes a cached connection to be dropped an
80 recreated after a given ttl, regardless of being idle or not.
81 default-target none
84 This directive forces the backend to reject all those operations
85 that must resolve to a single target in case none or multiple
86 targets are selected. They include: add, delete, modify, mod‐
87 rdn; compare is not included, as well as bind since, as they
88 don't alter entries, in case of multiple matches an attempt is
89 made to perform the operation on any candidate target, with the
90 constraint that at most one must succeed. This directive can
91 also be used when processing targets to mark a specific target
92 as default.
93 dncache-ttl {DISABLED|forever|<ttl>}
96 This directive sets the time-to-live of the DN cache. This
97 caches the target that holds a given DN to speed up target se‐
98 lection in case multiple targets would result from an uncached
99 search; forever means cache never expires; disabled means no DN
100 caching; otherwise a valid ( > 0 ) ttl is required, in the for‐
101 mat illustrated for the idle-timeout directive.
102 onerr {CONTINUE|report|stop}
105 This directive allows one to select the behavior in case an er‐
106 ror is returned by one target during a search. The default,
107 continue, consists in continuing the operation, trying to return
108 as much data as possible. If the value is set to stop, the
109 search is terminated as soon as an error is returned by one tar‐
110 get, and the error is immediately propagated to the client. If
111 the value is set to report, the search is continued to the end
112 but, in case at least one target returned an error code, the
113 first non-success error code is returned.
114 norefs <NO|yes>
117 If yes, do not return search reference responses. By default,
118 they are returned unless request is LDAPv2. If set before any
119 target specification, it affects all targets, unless overridden
120 by any per-target directive.
121 noundeffilter <NO|yes>
124 If yes, return success instead of searching if a filter is unde‐
125 fined or contains undefined portions. By default, the search is
126 propagated after replacing undefined portions with (!(object‐
127 Class=*)), which corresponds to the empty result set. If set
128 before any target specification, it affects all targets, unless
129 overridden by any per-target directive.
130 protocol-version {0,2,3}
133 This directive indicates what protocol version must be used to
134 contact the remote server. If set to 0 (the default), the proxy
135 uses the same protocol version used by the client, otherwise the
136 requested protocol is used. The proxy returns unwillingToPer‐
137 form if an operation that is incompatible with the requested
138 protocol is attempted. If set before any target specification,
139 it affects all targets, unless overridden by any per-target di‐
140 rective.
141 pseudoroot-bind-defer {YES|no}
144 This directive, when set to yes, causes the authentication to
145 the remote servers with the pseudo-root identity (the identity
146 defined in each idassert-bind directive) to be deferred until
147 actually needed by subsequent operations. Otherwise, all binds
148 as the rootdn are propagated to the targets.
149 quarantine <interval>,<num>[;<interval>,<num>[...]]
152 Turns on quarantine of URIs that returned LDAP_UNAVAILABLE, so
153 that an attempt to reconnect only occurs at given intervals in‐
154 stead of any time a client requests an operation. The pattern
155 is: retry only after at least interval seconds elapsed since
156 last attempt, for exactly num times; then use the next pattern.
157 If num for the last pattern is "+", it retries forever; other‐
158 wise, no more retries occur. This directive must appear before
159 any target specification; it affects all targets with the same
160 pattern.
161 rebind-as-user {NO|yes}
164 If this option is given, the client's bind credentials are re‐
165 membered for rebinds, when trying to re-establish a broken con‐
166 nection, or when chasing a referral, if chase-referrals is set
167 to yes.
168 session-tracking-request {NO|yes}
171 Adds session tracking control for all requests. The client's IP
172 and hostname, and the identity associated to each request, if
173 known, are sent to the remote server for informational purposes.
174 This directive is incompatible with setting protocol-version to
175 2. If set before any target specification, it affects all tar‐
176 gets, unless overridden by any per-target directive.
177 single-conn {NO|yes}
180 Discards current cached connection when the client rebinds.
181 use-temporary-conn {NO|yes}
184 when set to yes, create a temporary connection whenever compet‐
185 ing with other threads for a shared one; otherwise, wait until
186 the shared connection is available.
187
190 Target specification starts with a "uri" directive:
191 uri <protocol>://[<host>]/<naming context> [...]
194 The <protocol> part can be anything ldap_initialize(3) accepts
195 ({ldap|ldaps|ldapi} and variants); the <host> may be omitted,
196 defaulting to whatever is set in ldap.conf(5). The <naming con‐
197 text> part is mandatory for the first URI, but it must be omit‐
198 ted for subsequent ones, if any. The naming context part must
199 be within the naming context defined for the backend, e.g.:
200 suffix "dc=foo,dc=com"
202 uri "ldap://x.foo.com/dc=x,dc=foo,dc=com"
203 The <naming context> part doesn't need to be unique across the
205 targets; it may also match one of the values of the "suffix" di‐
206 rective. Multiple URIs may be defined in a single URI state‐
207 ment. The additional URIs must be separate arguments and must
208 not have any <naming context> part. This causes the underlying
209 library to contact the first server of the list that responds.
210 For example, if l1.foo.com and l2.foo.com are shadows of the
211 same server, the directive
212 suffix "dc=foo,dc=com"
214 uri "ldap://l1.foo.com/dc=foo,dc=com" "ldap://l2.foo.com/"
215 causes l2.foo.com to be contacted whenever l1.foo.com does not
217 respond. In that case, the URI list is internally rearranged,
218 by moving unavailable URIs to the end, so that further connec‐
219 tion attempts occur with respect to the last URI that succeeded.
220 acl-authcDN <administrative DN for access control purposes>
223 DN which is used to query the target server for acl checking, as
224 in the LDAP backend; it is supposed to have read access on the
225 target server to attributes used on the proxy for acl checking.
226 There is no risk of giving away such values; they are only used
227 to check permissions. The acl-authcDN identity is by no means
228 implicitly used by the proxy when the client connects anony‐
229 mously.
230 acl-passwd <password>
233 Password used with the acl-authcDN above.
234 bind-timeout <microseconds>
237 This directive defines the timeout, in microseconds, used when
238 polling for response after an asynchronous bind connection. The
239 initial call to ldap_result(3) is performed with a trade-off
240 timeout of 100000 us; if that results in a timeout exceeded,
241 subsequent calls use the value provided with bind-timeout. The
242 default value is used also for subsequent calls if bind-timeout
243 is not specified. If set before any target specification, it
244 affects all targets, unless overridden by any per-target direc‐
245 tive.
246 chase-referrals {YES|no}
249 enable/disable automatic referral chasing, which is delegated to
250 the underlying libldap, with rebinding eventually performed if
251 the rebind-as-user directive is used. The default is to chase
252 referrals. If set before any target specification, it affects
253 all targets, unless overridden by any per-target directive.
254 client-pr {accept-unsolicited|DISABLE|<size>}
257 This feature allows one to use RFC 2696 Paged Results control
258 when performing search operations with a specific target, irre‐
259 spective of the client's request. When set to a numeric value,
260 Paged Results control is always used with size as the page size.
261 When set to accept-unsolicited, unsolicited Paged Results con‐
262 trol responses are accepted and honored for compatibility with
263 broken remote DSAs. The client is not exposed to paged results
264 handling between slapd-meta(5) and the remote servers. By de‐
265 fault (disabled), Paged Results control is not used and re‐
266 sponses are not accepted. If set before any target specifica‐
267 tion, it affects all targets, unless overridden by any per-tar‐
268 get directive.
269 default-target [<target>]
272 The "default-target" directive can also be used during target
273 specification. With no arguments it marks the current target as
274 the default. The optional number marks target <target> as the
275 default one, starting from 1. Target <target> must be defined.
276 filter <pattern>
279 This directive allows specifying a regex(5) pattern to indicate
280 what search filter terms are actually served by a target.
281 In a search request, if the search filter matches the pattern
283 the target is considered while fulfilling the request; otherwise
284 the target is ignored. There may be multiple occurrences of the
285 filter directive for each target.
286 idassert-authzFrom <authz-regexp>
289 if defined, selects what local identities are authorized to ex‐
290 ploit the identity assertion feature. The string <authz-regexp>
291 follows the rules defined for the authzFrom attribute. See
292 slapd.conf(5), section related to authz-policy, for details on
293 the syntax of this field.
294 idassert-bind bindmethod=none|simple|sasl [binddn=<simple DN>]
297 [credentials=<simple password>] [saslmech=<SASL mech>]
298 [secprops=<properties>] [realm=<realm>] [authcId=<authentication
299 ID>] [authzId=<authorization ID>] [authz={native|proxyauthz}]
300 [mode=<mode>] [flags=<flags>] [starttls=no|yes|critical]
301 [tls_cert=<file>] [tls_key=<file>] [tls_cacert=<file>]
302 [tls_cacertdir=<path>] [tls_reqcert=never|allow|try|demand]
303 [tls_reqsan=never|allow|try|demand] [tls_cipher_suite=<ciphers>]
304 [tls_ecname=<ciphers>] [tls_protocol_min=<major>[.<minor>]]
305 [tls_crlcheck=none|peer|all]
306 Allows one to define the parameters of the authentication method
307 that is internally used by the proxy to authorize connections
308 that are authenticated by other databases. The identity defined
309 by this directive, according to the properties associated to the
310 authentication method, is supposed to have auth access on the
311 target server to attributes used on the proxy for authentication
312 and authorization, and to be allowed to authorize the users.
313 This requires to have proxyAuthz privileges on a wide set of
314 DNs, e.g. authzTo=dn.subtree:"", and the remote server to have
315 authz-policy set to to or both. See slapd.conf(5) for details
316 on these statements and for remarks and drawbacks about their
317 usage. The supported bindmethods are
318 none|simple|sasl
320 where none is the default, i.e. no identity assertion is
322 performed.
323 The authz parameter is used to instruct the SASL bind to exploit
325 native SASL authorization, if available; since connections are
326 cached, this should only be used when authorizing with a fixed
327 identity (e.g. by means of the authzDN or authzID parameters).
328 Otherwise, the default proxyauthz is used, i.e. the proxyAuthz
329 control (Proxied Authorization, RFC 4370) is added to all
330 operations.
331 The supported modes are:
333 <mode> := {legacy|anonymous|none|self}
335 If <mode> is not present, and authzId is given, the proxy always
337 authorizes that identity. <authorization ID> can be
338 u:<user>
340 [dn:]<DN>
342 The former is supposed to be expanded by the remote server
344 according to the authz rules; see slapd.conf(5) for details. In
345 the latter case, whether or not the dn: prefix is present, the
346 string must pass DN validation and normalization.
347 The default mode is legacy, which implies that the proxy will
349 either perform a simple bind as the authcDN or a SASL bind as
350 the authcID and assert the client's identity when it is not
351 anonymous. Direct binds are always proxied. The other modes
352 imply that the proxy will always either perform a simple bind as
353 the authcDN or a SASL bind as the authcID, unless restricted by
354 idassert-authzFrom rules (see below), in which case the
355 operation will fail; eventually, it will assert some other
356 identity according to <mode>. Other identity assertion modes
357 are anonymous and self, which respectively mean that the empty
358 or the client's identity will be asserted; none, which means
359 that no proxyAuthz control will be used, so the authcDN or the
360 authcID identity will be asserted. For all modes that require
361 the use of the proxyAuthz control, on the remote server the
362 proxy identity must have appropriate authzTo permissions, or the
363 asserted identities must have appropriate authzFrom permissions.
364 Note, however, that the ID assertion feature is mostly useful
365 when the asserted identities do not exist on the remote server.
366 When bindmethod is SASL, the authcDN must be specified in
367 addition to the authcID, although it is not used within the
368 authentication process.
369 Flags can be
371 override,[non-]prescriptive,proxy-authz-[non-]critical
373 When the override flag is used, identity assertion takes place
375 even when the database is authorizing for the identity of the
376 client, i.e. after binding with the provided identity, and thus
377 authenticating it, the proxy performs the identity assertion
378 using the configured identity and authentication method.
379 When the prescriptive flag is used (the default), operations
381 fail with inappropriateAuthentication for those identities whose
382 assertion is not allowed by the idassert-authzFrom patterns. If
383 the non-prescriptive flag is used, operations are performed
384 anonymously for those identities whose assertion is not allowed
385 by the idassert-authzFrom patterns.
386 When the proxy-authz-non-critical flag is used (the default),
388 the proxyAuthz control is not marked as critical, in violation
389 of RFC 4370. Use of proxy-authz-critical is recommended.
390 The TLS settings default to the same as the main slapd TLS
392 settings, except for tls_reqcert which defaults to "demand", and
393 tls_reqsan which defaults to "allow"..
394 The identity associated to this directive is also used for
396 privileged operations whenever idassert-bind is defined and
397 acl-bind is not. See acl-bind for details.
398 idle-timeout <time>
401 This directive causes a cached connection to be dropped an
402 recreated after it has been idle for the specified time. The
403 value can be specified as
404 [<d>d][<h>h][<m>m][<s>[s]]
406 where <d>, <h>, <m> and <s> are respectively treated as days,
408 hours, minutes and seconds. If set before any target
409 specification, it affects all targets, unless overridden by any
410 per-target directive.
411 keepalive <idle>:<probes>:<interval>
414 The keepalive parameter sets the values of idle, probes, and
415 interval used to check whether a socket is alive; idle is the
416 number of seconds a connection needs to remain idle before TCP
417 starts sending keepalive probes; probes is the maximum number of
418 keepalive probes TCP should send before dropping the connection;
419 interval is interval in seconds between individual keepalive
420 probes. Only some systems support the customization of these
421 values; the keepalive parameter is ignored otherwise, and
422 system-wide settings are used.
423 tcp-user-timeout <milliseconds>
426 If non-zero, corresponds to the TCP_USER_TIMEOUT set on the
427 target connections, overriding the operating system setting.
428 Only some systems support the customization of this parameter,
429 it is ignored otherwise and system-wide settings are used.
430 map {attribute|objectclass} [<local name>|*] {<foreign name>|*}
433 This maps object classes and attributes as in the LDAP backend.
434 See slapd-ldap(5).
435 network-timeout <time>
438 Sets the network timeout value after which poll(2)/select(2)
439 following a connect(2) returns in case of no activity. The
440 value is in seconds, and it can be specified as for
441 idle-timeout. If set before any target specification, it
442 affects all targets, unless overridden by any per-target
443 directive.
444 nretries {forever|never|<nretries>}
447 This directive defines how many times a bind should be retried
448 in case of temporary failure in contacting a target. If defined
449 before any target specification, it applies to all targets (by
450 default, 3 times); the global value can be overridden by
451 redefinitions inside each target specification.
452 rewrite* ...
455 The rewrite options are described in the "REWRITING" section.
456 subtree-{exclude|include} <rule>
459 This directive allows one to indicate what subtrees are actually
460 served by a target. The syntax of the supported rules is
461 <rule>: [dn[.<style>]:]<pattern>
463 <style>: subtree|children|regex
465 When <style> is either subtree or children the <pattern> is a DN
467 that must be within the naming context served by the target.
468 When <style> is regex the <pattern> is a regex(5) pattern. If
469 the dn.<style>: prefix is omitted, dn.subtree: is implicitly
470 assumed for backward compatibility.
471 In the subtree-exclude form if the request DN matches at least
473 one rule, the target is not considered while fulfilling the
474 request; otherwise, the target is considered based on the value
475 of the request DN. When the request is a search, also the scope
476 is considered.
477 In the subtree-include form if the request DN matches at least
479 one rule, the target is considered while fulfilling the request;
480 otherwise the target is ignored.
481 | match | exclude |
484 +---------+---------+-------------------+
485 | T | T | not candidate |
486 | F | T | continue checking |
487 +---------+---------+-------------------+
488 | T | F | candidate |
489 | F | F | not candidate |
490 +---------+---------+-------------------+
491 There may be multiple occurrences of the subtree-exclude or
493 subtree-include directive for each of the targets, but they are
494 mutually exclusive.
495 suffixmassage <virtual naming context> <real naming context>
498 All the directives starting with "rewrite" refer to the rewrite
499 engine that has been added to slapd. The "suffixmassage"
500 directive was introduced in the LDAP backend to allow suffix
501 massaging while proxying. It has been obsoleted by the
502 rewriting tools. However, both for backward compatibility and
503 for ease of configuration when simple suffix massage is
504 required, it has been preserved. It wraps the basic rewriting
505 instructions that perform suffix massaging. See the "REWRITING"
506 section for a detailed list of the rewrite rules it implies.
507 t-f-support {NO|yes|discover}
510 enable if the remote server supports absolute filters (see RFC
511 4526 for details). If set to discover, support is detected by
512 reading the remote server's root DSE. If set before any target
513 specification, it affects all targets, unless overridden by any
514 per-target directive.
515 timeout [<op>=]<val> [...]
518 This directive allows one to set per-operation timeouts.
519 Operations can be
520 <op> ::= bind, add, delete, modrdn, modify, compare, search
522 The overall duration of the search operation is controlled
524 either by the timelimit parameter or by server-side enforced
525 time limits (see timelimit and limits in slapd.conf(5) for
526 details). This timeout parameter controls how long the target
527 can be irresponsive before the operation is aborted. Timeout is
528 meaningless for the remaining operations, unbind and abandon,
529 which do not imply any response, while it is not yet implemented
530 in currently supported extended operations. If no operation is
531 specified, the timeout val affects all supported operations. If
532 specified before any target definition, it affects all targets
533 unless overridden by per-target directives.
534 Note: if the timeout is exceeded, the operation is cancelled
536 (according to the cancel directive); the protocol does not
537 provide any means to rollback operations, so the client will not
538 be notified about the result of the operation, which may
539 eventually succeeded or not. In case the timeout is exceeded
540 during a bind operation, the connection is destroyed, according
541 to RFC4511.
542 tls {none|[try-]start|[try-]propagate|ldaps}
545 [starttls=no] [tls_cert=<file>] [tls_key=<file>]
546 [tls_cacert=<file>] [tls_cacertdir=<path>]
547 [tls_reqcert=never|allow|try|demand]
548 [tls_reqsan=never|allow|try|demand] [tls_cipher_suite=<ciphers>]
549 [tls_ecname=<names>] [tls_crlcheck=none|peer|all]
550 Specify TLS settings regular connections.
551 If the first parameter is not "none" then this configures the
553 TLS settings to be used for regular connections. The StartTLS
554 extended operation will be used when establishing the connection
555 unless the URI directive protocol scheme is ldaps://. In that
556 case this keyword may only be set to "ldaps" and the StartTLS
557 operation will not be used.
558 With propagate, the proxy issues the StartTLS operation only if
560 the original connection has a TLS layer set up. The try- prefix
561 instructs the proxy to continue operations if the StartTLS
562 operation failed; its use is not recommended.
563 The TLS settings default to the same as the main slapd TLS
565 settings, except for tls_reqcert which defaults to "demand",
566 tls_reqsan which defaults to "allow", and starttls which is
567 overshadowed by the first keyword and thus ignored.
568 If set before any target specification, it affects all targets,
570 unless overridden by any per-target directive.
571
574 A powerful (and in some sense dangerous) rewrite engine has been added
575 to both the LDAP and Meta backends. While the former can gain limited
576 beneficial effects from rewriting stuff, the latter can become an
577 amazingly powerful tool.
578 Consider a couple of scenarios first.
580 1) Two directory servers share two levels of naming context; say
582 "dc=a,dc=foo,dc=com" and "dc=b,dc=foo,dc=com". Then, an unambiguous
583 Meta database can be configured as:
584 database meta
586 suffix "dc=foo,dc=com"
587 uri "ldap://a.foo.com/dc=a,dc=foo,dc=com"
588 uri "ldap://b.foo.com/dc=b,dc=foo,dc=com"
589 Operations directed to a specific target can be easily resolved because
591 there are no ambiguities. The only operation that may resolve to
592 multiple targets is a search with base "dc=foo,dc=com" and scope at
593 least "one", which results in spawning two searches to the targets.
594 2a) Two directory servers don't share any portion of naming context,
596 but they'd present as a single DIT [Caveat: uniqueness of (massaged)
597 entries among the two servers is assumed; integrity checks risk to
598 incur in excessive overhead and have not been implemented]. Say we
599 have "dc=bar,dc=org" and "o=Foo,c=US", and we'd like them to appear as
600 branches of "dc=foo,dc=com", say "dc=a,dc=foo,dc=com" and
601 "dc=b,dc=foo,dc=com". Then we need to configure our Meta backend as:
602 database meta
604 suffix "dc=foo,dc=com"
605 uri "ldap://a.bar.com/dc=a,dc=foo,dc=com"
607 suffixmassage "dc=a,dc=foo,dc=com" "dc=bar,dc=org"
608 uri "ldap://b.foo.com/dc=b,dc=foo,dc=com"
610 suffixmassage "dc=b,dc=foo,dc=com" "o=Foo,c=US"
611 Again, operations can be resolved without ambiguity, although some
613 rewriting is required. Notice that the virtual naming context of each
614 target is a branch of the database's naming context; it is rewritten
615 back and forth when operations are performed towards the target
616 servers. What "back and forth" means will be clarified later.
617 When a search with base "dc=foo,dc=com" is attempted, if the scope is
619 "base" it fails with "no such object"; in fact, the common root of the
620 two targets (prior to massaging) does not exist. If the scope is
621 "one", both targets are contacted with the base replaced by each
622 target's base; the scope is derated to "base". In general, a scope
623 "one" search is honored, and the scope is derated, only when the
624 incoming base is at most one level lower of a target's naming context
625 (prior to massaging).
626 Finally, if the scope is "sub" the incoming base is replaced by each
628 target's unmassaged naming context, and the scope is not altered.
629 2b) Consider the above reported scenario with the two servers sharing
631 the same naming context:
632 database meta
634 suffix "dc=foo,dc=com"
635 uri "ldap://a.bar.com/dc=foo,dc=com"
637 suffixmassage "dc=foo,dc=com" "dc=bar,dc=org"
638 uri "ldap://b.foo.com/dc=foo,dc=com"
640 suffixmassage "dc=foo,dc=com" "o=Foo,c=US"
641 All the previous considerations hold, except that now there is no way
643 to unambiguously resolve a DN. In this case, all the operations that
644 require an unambiguous target selection will fail unless the DN is
645 already cached or a default target has been set. Practical
646 configurations may result as a combination of all the above scenarios.
647
649 Note on ACLs: at present you may add whatever ACL rule you desire to
650 the Meta (and LDAP) backends. However, the meaning of an ACL on a
651 proxy may require some considerations. Two philosophies may be
652 considered:
653 a) the remote server dictates the permissions; the proxy simply passes
655 back what it gets from the remote server.
656 b) the remote server unveils "everything"; the proxy is responsible for
658 protecting data from unauthorized access.
659 Of course the latter sounds unreasonable, but it is not. It is
661 possible to imagine scenarios in which a remote host discloses data
662 that can be considered "public" inside an intranet, and a proxy that
663 connects it to the internet may impose additional constraints. To this
664 purpose, the proxy should be able to comply with all the ACL matching
665 criteria that the server supports. This has been achieved with regard
666 to all the criteria supported by slapd except a special subtle case
667 (please file an ITS if you can find other exceptions:
668 <http://www.openldap.org/its/>). The rule
669 access to dn="<dn>" attrs=<attr>
671 by dnattr=<dnattr> read
672 by * none
673 cannot be matched iff the attribute that is being requested, <attr>, is
675 NOT <dnattr>, and the attribute that determines membership, <dnattr>,
676 has not been requested (e.g. in a search)
677 In fact this ACL is resolved by slapd using the portion of entry it
679 retrieved from the remote server without requiring any further
680 intervention of the backend, so, if the <dnattr> attribute has not been
681 fetched, the match cannot be assessed because the attribute is not
682 present, not because no value matches the requirement!
683 Note on ACLs and attribute mapping: ACLs are applied to the mapped
685 attributes; for instance, if the attribute locally known as "foo" is
686 mapped to "bar" on a remote server, then local ACLs apply to attribute
687 "foo" and are totally unaware of its remote name. The remote server
688 will check permissions for "bar", and the local server will possibly
689 enforce additional restrictions to "foo".
690
692 A string is rewritten according to a set of rules, called a `rewrite
693 context'. The rules are based on POSIX (''extended'') regular
694 expressions (regex) with substring matching; basic variable
695 substitution and map resolution of substrings is allowed by specific
696 mechanisms detailed in the following. The behavior of pattern
697 matching/substitution can be altered by a set of flags.
698 The underlying concept is to build a lightweight rewrite module for the
700 slapd server (initially dedicated to the LDAP backend).
701
703 An incoming string is matched against a set of rules. Rules are made
704 of a regex match pattern, a substitution pattern and a set of actions,
705 described by a set of flags. In case of match a string rewriting is
706 performed according to the substitution pattern that allows one to
707 refer to substrings matched in the incoming string. The actions, if
708 any, are finally performed. The substitution pattern allows map
709 resolution of substrings. A map is a generic object that maps a
710 substitution pattern to a value. The flags are divided in "Pattern
711 matching Flags" and "Action Flags"; the former alter the regex match
712 pattern behavior while the latter alter the action that is taken after
713 substitution.
714
716 `C' honors case in matching (default is case insensitive)
717 `R' use POSIX ''basic'' regular expressions (default is
719 ''extended'')
720 `M{n}' allow no more than n recursive passes for a specific rule; does
722 not alter the max total count of passes, so it can only enforce
723 a stricter limit for a specific rule.
724
726 `:' apply the rule once only (default is recursive)
727 `@' stop applying rules in case of match; the current rule is still
729 applied recursively; combine with `:' to apply the current rule
730 only once and then stop.
731 `#' stop current operation if the rule matches, and issue an
733 `unwilling to perform' error.
734 `G{n}' jump n rules back and forth (watch for loops!). Note that
736 `G{1}' is implicit in every rule.
737 `I' ignores errors in rule; this means, in case of error, e.g.
739 issued by a map, the error is treated as a missed match. The
740 `unwilling to perform' is not overridden.
741 `U{n}' uses n as return code if the rule matches; the flag does not
743 alter the recursive behavior of the rule, so, to have it
744 performed only once, it must be used in combination with `:',
745 e.g. `:U{16}' returns the value `16' after exactly one
746 execution of the rule, if the pattern matches. As a
747 consequence, its behavior is equivalent to `@', with the return
748 code set to n; or, in other words, `@' is equivalent to `U{0}'.
749 By convention, the freely available codes are above 16 included;
750 the others are reserved.
751 The ordering of the flags can be significant. For instance: `IG{2}'
753 means ignore errors and jump two lines ahead both in case of match and
754 in case of error, while `G{2}I' means ignore errors, but jump two lines
755 ahead only in case of match.
756 More flags (mainly Action Flags) will be added as needed.
758
760 See regex(7) and/or re_format(7).
761
763 Everything starting with `%' requires substitution;
764 the only obvious exception is `%%', which is left as is;
766 the basic substitution is `%d', where `d' is a digit; 0 means the whole
768 string, while 1-9 is a submatch;
769 a `%' followed by a `{' invokes an advanced substitution. The pattern
771 is:
772 `%' `{' [ <op> ] <name> `(' <substitution> `)' `}'
774 where <name> must be a legal name for the map, i.e.
776 <name> ::= [a-z][a-z0-9]* (case insensitive)
778 <op> ::= `>' `|' `&' `&&' `*' `**' `$'
779 and <substitution> must be a legal substitution pattern, with no limits
781 on the nesting level.
782 The operators are:
784 > sub context invocation; <name> must be a legal, already defined
786 rewrite context name
787 | external command invocation; <name> must refer to a legal,
789 already defined command name (NOT IMPL.)
790 & variable assignment; <name> defines a variable in the running
792 operation structure which can be dereferenced later; operator &
793 assigns a variable in the rewrite context scope; operator &&
794 assigns a variable that scopes the entire session, e.g. its
795 value can be dereferenced later by other rewrite contexts
796 * variable dereferencing; <name> must refer to a variable that is
798 defined and assigned for the running operation; operator *
799 dereferences a variable scoping the rewrite context; operator **
800 dereferences a variable scoping the whole session, e.g. the
801 value is passed across rewrite contexts
802 $ parameter dereferencing; <name> must refer to an existing
804 parameter; the idea is to make some run-time parameters set by
805 the system available to the rewrite engine, as the client host
806 name, the bind DN if any, constant parameters initialized at
807 config time, and so on; no parameter is currently set by either
808 back-ldap or back-meta, but constant parameters can be defined
809 in the configuration file by using the rewriteParam directive.
810 Substitution escaping has been delegated to the `%' symbol, which is
812 used instead of `\' in string substitution patterns because `\' is
813 already escaped by slapd's low level parsing routines; as a
814 consequence, regex escaping requires two `\' symbols, e.g.
815 `.*\.foo\.bar' must be written as `.*\\.foo\\.bar'.
816
818 A rewrite context is a set of rules which are applied in sequence. The
819 basic idea is to have an application initialize a rewrite engine (think
820 of Apache's mod_rewrite ...) with a set of rewrite contexts; when
821 string rewriting is required, one invokes the appropriate rewrite
822 context with the input string and obtains the newly rewritten one if no
823 errors occur.
824 Each basic server operation is associated to a rewrite context; they
826 are divided in two main groups: client -> server and server -> client
827 rewriting.
828 client -> server:
830 (default) if defined and no specific context
832 is available
833 bindDN bind
834 searchBase search
835 searchFilter search
836 searchFilterAttrDN search
837 compareDN compare
838 compareAttrDN compare AVA
839 addDN add
840 addAttrDN add AVA
841 modifyDN modify
842 modifyAttrDN modify AVA
843 modrDN modrdn
844 newSuperiorDN modrdn
845 deleteDN delete
846 exopPasswdDN password modify extended operation DN if proxy
847 server -> client:
849 searchResult search (only if defined; no default;
851 acts on DN and DN-syntax attributes
852 of search results)
853 searchAttrDN search AVA
854 matchedDN all ops (only if applicable)
855
857 rewriteEngine { on | off }
858 If `on', the requested rewriting is performed; if `off', no
859 rewriting takes place (an easy way to stop rewriting without
860 altering too much the configuration file).
861 rewriteContext <context name> [ alias <aliased context name> ]
863 <Context name> is the name that identifies the context, i.e. the
864 name used by the application to refer to the set of rules it
865 contains. It is used also to reference sub contexts in string
866 rewriting. A context may alias another one. In this case the
867 alias context contains no rule, and any reference to it will
868 result in accessing the aliased one.
869 rewriteRule <regex match pattern> <substitution pattern> [ <flags> ]
871 Determines how a string can be rewritten if a pattern is
872 matched. Examples are reported below.
873
875 rewriteMap <map type> <map name> [ <map attrs> ]
876 Allows one to define a map that transforms substring rewriting
877 into something else. The map is referenced inside the
878 substitution pattern of a rule.
879 rewriteParam <param name> <param value>
881 Sets a value with global scope, that can be dereferenced by the
882 command `%{$paramName}'.
883 rewriteMaxPasses <number of passes> [<number of passes per rule>]
885 Sets the maximum number of total rewriting passes that can be
886 performed in a single rewrite operation (to avoid loops). A
887 safe default is set to 100; note that reaching this limit is
888 still treated as a success; recursive invocation of rules is
889 simply interrupted. The count applies to the rewriting
890 operation as a whole, not to any single rule; an optional per-
891 rule limit can be set. This limit is overridden by setting
892 specific per-rule limits with the `M{n}' flag.
893
895 # set to `off' to disable rewriting
896 rewriteEngine on
897 # the rules the "suffixmassage" directive implies
899 rewriteEngine on
900 # all dataflow from client to server referring to DNs
901 rewriteContext default
902 rewriteRule "(.*)<virtualnamingcontext>$" "%1<realnamingcontext>" ":"
903 # empty filter rule
904 rewriteContext searchFilter
905 # all dataflow from server to client
906 rewriteContext searchResult
907 rewriteRule "(.*)<realnamingcontext>$" "%1<virtualnamingcontext>" ":"
908 rewriteContext searchAttrDN alias searchResult
909 rewriteContext matchedDN alias searchResult
910 # Everything defined here goes into the `default' context.
912 # This rule changes the naming context of anything sent
913 # to `dc=home,dc=net' to `dc=OpenLDAP, dc=org'
914 rewriteRule "(.*)dc=home,[ ]?dc=net"
916 "%1dc=OpenLDAP, dc=org" ":"
917 # since a pretty/normalized DN does not include spaces
919 # after rdn separators, e.g. `,', this rule suffices:
920 rewriteRule "(.*)dc=home,dc=net"
922 "%1dc=OpenLDAP,dc=org" ":"
923 # Start a new context (ends input of the previous one).
925 # This rule adds blanks between DN parts if not present.
926 rewriteContext addBlanks
927 rewriteRule "(.*),([^ ].*)" "%1, %2"
928 # This one eats blanks
930 rewriteContext eatBlanks
931 rewriteRule "(.*),[ ](.*)" "%1,%2"
932 # Here control goes back to the default rewrite
934 # context; rules are appended to the existing ones.
935 # anything that gets here is piped into rule `addBlanks'
936 rewriteContext default
937 rewriteRule ".*" "%{>addBlanks(%0)}" ":"
938 # Rewrite the search base according to `default' rules.
940 rewriteContext searchBase alias default
941 # Search results with OpenLDAP DN are rewritten back with
943 # `dc=home,dc=net' naming context, with spaces eaten.
944 rewriteContext searchResult
945 rewriteRule "(.*[^ ]?)[ ]?dc=OpenLDAP,[ ]?dc=org"
946 "%{>eatBlanks(%1)}dc=home,dc=net" ":"
947 # Bind with email instead of full DN: we first need
949 # an ldap map that turns attributes into a DN (the
950 # argument used when invoking the map is appended to
951 # the URI and acts as the filter portion)
952 rewriteMap ldap attr2dn "ldap://host/dc=my,dc=org?dn?sub"
953 # Then we need to detect DN made up of a single email,
955 # e.g. `mail=someone@example.com'; note that the rule
956 # in case of match stops rewriting; in case of error,
957 # it is ignored. In case we are mapping virtual
958 # to real naming contexts, we also need to rewrite
959 # regular DNs, because the definition of a bindDn
960 # rewrite context overrides the default definition.
961 rewriteContext bindDN
962 rewriteRule "^mail=[^,]+@[^,]+$" "%{attr2dn(%0)}" ":@I"
963 # This is a rather sophisticated example. It massages a
965 # search filter in case who performs the search has
966 # administrative privileges. First we need to keep
967 # track of the bind DN of the incoming request, which is
968 # stored in a variable called `binddn' with session scope,
969 # and left in place to allow regular binding:
970 rewriteContext bindDN
971 rewriteRule ".+" "%{&&binddn(%0)}%0" ":"
972 # A search filter containing `uid=' is rewritten only
974 # if an appropriate DN is bound.
975 # To do this, in the first rule the bound DN is
976 # dereferenced, while the filter is decomposed in a
977 # prefix, in the value of the `uid=<arg>' AVA, and
978 # in a suffix. A tag `<>' is appended to the DN.
979 # If the DN refers to an entry in the `ou=admin' subtree,
980 # the filter is rewritten OR-ing the `uid=<arg>' with
981 # `cn=<arg>'; otherwise it is left as is. This could be
982 # useful, for instance, to allow apache's auth_ldap-1.4
983 # module to authenticate users with both `uid' and
984 # `cn', but only if the request comes from a possible
985 # `cn=Web auth,ou=admin,dc=home,dc=net' user.
986 rewriteContext searchFilter
987 rewriteRule "(.*\\()uid=([a-z0-9_]+)(\\).*)"
988 "%{**binddn}<>%{&prefix(%1)}%{&arg(%2)}%{&suffix(%3)}"
989 ":I"
990 rewriteRule "[^,]+,ou=admin,dc=home,dc=net"
991 "%{*prefix}|(uid=%{*arg})(cn=%{*arg})%{*suffix}" ":@I"
992 rewriteRule ".*<>" "%{*prefix}uid=%{*arg}%{*suffix}" ":"
993 # This example shows how to strip unwanted DN-valued
995 # attribute values from a search result; the first rule
996 # matches DN values below "ou=People,dc=example,dc=com";
997 # in case of match the rewriting exits successfully.
998 # The second rule matches everything else and causes
999 # the value to be rejected.
1000 rewriteContext searchResult
1001 rewriteRule ".*,ou=People,dc=example,dc=com" "%0" ":@"
1002 rewriteRule ".*" "" "#"
1003
1005 In case the rewritten DN is an LDAP URI, the operation is initiated
1006 towards the host[:port] indicated in the uri, if it does not refer to
1007 the local server. E.g.:
1008 rewriteRule '^cn=root,.*' '%0' 'G{3}'
1010 rewriteRule '^cn=[a-l].*' 'ldap://ldap1.my.org/%0' ':@'
1011 rewriteRule '^cn=[m-z].*' 'ldap://ldap2.my.org/%0' ':@'
1012 rewriteRule '.*' 'ldap://ldap3.my.org/%0' ':@'
1013 (Rule 1 is simply there to illustrate the `G{n}' action; it could have
1015 been written:
1016 rewriteRule '^cn=root,.*' 'ldap://ldap3.my.org/%0' ':@'
1018 with the advantage of saving one rewrite pass ...)
1020
1023 The meta backend does not honor all ACL semantics as described in
1024 slapd.access(5). In general, access checking is delegated to the
1025 remote server(s). Only read (=r) access to the entry pseudo-attribute
1026 and to the other attribute values of the entries returned by the search
1027 operation is honored, which is performed by the frontend.
1028
1031 The proxy cache overlay allows caching of LDAP search requests
1032 (queries) in a local database. See slapo-pcache(5) for details.
1033
1036 The following statements have been deprecated and should no longer be
1037 used.
1038 pseudorootdn <substitute DN in case of rootdn bind>
1041 Use idassert-bind instead.
1042 pseudorootpw <substitute password in case of rootdn bind>
1045 Use idassert-bind instead.
1046
1051 /etc/openldap/slapd.conf
1052 default slapd configuration file
1053
1055 slapd.conf(5), slapd-asyncmeta(5), slapd-ldap(5), slapo-pcache(5),
1056 slapd(8), regex(7), re_format(7).
1057
1059 Pierangelo Masarati, based on back-ldap by Howard Chu
1060OpenLDAP 2.6.3 2022/07/14 SLAPD-META(5)