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slapd-meta(5)





NAME

       slapd-meta - metadirectory backend


SYNOPSIS

       /etc/openldap/slapd.conf


DESCRIPTION

       The  meta backend to slapd(8) performs basic LDAP proxying with respect
       to a set of remote LDAP servers,  called  "targets".   The  information
       contained  in  these  servers can be presented as belonging to a single
       Directory Information Tree (DIT).

       A basic knowledge of the functionality of the slapd-ldap(5) backend  is
       recommended.   This  backend has been designed as an enhancement of the
       ldap backend.  The two backends share many features (actually they also
       share  portions  of code).  While the ldap backend is intended to proxy
       operations directed to a single server,  the  meta  backend  is  mainly
       intended  for  proxying of multiple servers and possibly naming context
       masquerading.  These features, although useful in many  scenarios,  may
       result  in  excessive overhead for some applications, so its use should
       be carefully considered.  In the examples section, some typical scenar-
       ios will be discussed.


EXAMPLES

       There  are  examples  in various places in this document, as well as in
       the slapd/back-meta/data/ directory in the OpenLDAP source tree.


CONFIGURATION

       These slapd.conf options apply to the META backend database.  That  is,
       they  must follow a "database meta" line and come before any subsequent
       "backend" or "database" lines.  Other database options are described in
       the slapd.conf(5) manual page.

       Note: as with the ldap backend, operational attributes related to entry
       creation/modification should not be used, as they would  be  passed  to
       the  target  servers,  generating  an error.  Moreover, it makes little
       sense to use such attributes in proxying, as the proxy  server  doesn't
       actually store data, so it should have no knowledge of such attributes.
       While code to strip the modification attributes has been put  in  place
       (and  #ifdef'd),  it  implies  unmotivated overhead.  So it is strongly
       recommended to set
              lastmod  off
       for every ldap and meta backend.


SPECIAL CONFIGURATION DIRECTIVES

       Target configuration starts with the "uri" directive.  All the configu-
       ration  directives  that  are not specific to targets should be defined
       first for clarity, including those that are  common  to  all  backends.
       They are:

       default-target none
              This directive forces the backend to reject all those operations
              that must resolve to a single target in case  none  or  multiple
              targets  are  selected.  They include: add, delete, modify, mod-
              rdn; compare is not included, as well as  bind  since,  as  they
              don't  alter  entries, in case of multiple matches an attempt is
              made to perform the operation on any candidate target, with  the
              constraint  that  at  most one must succeed.  This directive can
              also be used when processing targets to mark a  specific  target
              as default.

       dncache-ttl {forever|disabled|<ttl>}
              This  directive  sets  the  time-to-live  of the DN cache.  This
              caches the target that holds a  given  DN  to  speed  up  target
              selection in case multiple targets would result from an uncached
              search; forever means cache never expires; disabled means no  DN
              caching; otherwise a valid ( > 0 ) ttl in seconds is required.


TARGET SPECIFICATION

       Target specification starts with a "uri" directive:

       uri <protocol>://[<host>[:<port>]]/<naming context>
              The  "server"  directive  that  was  allowed in the LDAP backend
              (although deprecated) has been discarded in  the  Meta  backend.
              The  <protocol>  part can be anything ldap_initialize(3) accepts
              ({ldap|ldaps|ldapi} and variants);  <host>  and  <port>  may  be
              omitted,  defaulting  to whatever is set in /etc/ldap.conf.  The
              <naming context> part is mandatory.  It must end with one of the
              naming contexts defined for the backend, e.g.:

              suffix "dc=foo,dc=com"
              uri    "ldap://x.foo.com/dc=x,dc=foo,dc=com"

       The <naming context> part doesn't need to be unique across the targets;
       it may also match one of the values of the "suffix" directive.   Multi-
       ple  URIs  may be defined in a single argument.  The URIs must be sepa-
       rated by TABs (e.g. '\t'), and the additional URIs must have no <naming
       context> part.  This causes the underlying library to contact the first
       server of the list that responds.

       default-target [<target>]
              The "default-target" directive can also be  used  during  target
              specification.  With no arguments it marks the current target as
              the default.  The optional number marks target <target>  as  the
              default  one, starting from 1.  Target <target> must be defined.

       binddn <administrative DN for access control purposes>
              This directive, as in the LDAP backend, allows to define the  DN
              that  is  used  to  query the target server for acl checking; it
              should have read access on the target server to attributes  used
              on  the proxy for acl checking.  There is no risk of giving away
              such values; they are only used to check permissions.

       bindpw <password for access control purposes>
              This directive sets the password for acl checking in conjunction
              with the above mentioned "binddn" directive.

       rebind-as-user
              If  this  option  is  given,  the  client's bind credentials are
              remembered for rebinds when chasing referrals.

       pseudorootdn <substitute DN in case of rootdn bind>
              This directive, if present, sets the DN that will be substituted
              to  the  bind DN if a bind with the backend's "rootdn" succeeds.
              The true "rootdn" of the target server ought  not  be  used;  an
              arbitrary administrative DN should used instead.

       pseudorootpw <substitute password in case of rootdn bind>
              This  directive  sets the credential that will be used in case a
              bind with the backend's "rootdn" succeeds, and the bind is prop-
              agated to the target using the "pseudorootdn" DN.

       Note:  cleartext  credentials  must be supplied here; as a consequence,
       using the pseudorootdn/pseudorootpw directives is inherently unsafe.

       rewrite* ...
              The rewrite options are described in the "REWRITING" section.

       suffixmassage <virtual naming context> <real naming context>
              All the directives starting with "rewrite" refer to the  rewrite
              engine that has been added to slapd.  The "suffixmassage" direc-
              tive was introduced in the LDAP backend to allow suffix  massag-
              ing  while  proxying.   It  has  been obsoleted by the rewriting
              tools.  However, both for backward compatibility and for ease of
              configuration  when  simple  suffix  massage is required, it has
              been preserved.  It wraps the basic rewriting instructions  that
              perform  suffix  massaging.   See  the "REWRITING" section for a
              detailed list of the rewrite rules it implies.

       Note: this also fixes a flaw in suffix  massaging,  which  operated  on
       (case  insensitive)  DNs instead of normalized DNs, so "dc=foo, dc=com"
       would not match "dc=foo,dc=com".

       See the "REWRITING" section.

       map {attribute|objectclass} [<local name>|*] {<foreign name>|*}
              This maps object classes and attributes as in the LDAP  backend.
              See slapd-ldap(5).


SCENARIOS

       A  powerful (and in some sense dangerous) rewrite engine has been added
       to both the LDAP and Meta backends.  While the former can gain  limited
       beneficial effects from rewriting stuff, the latter can become an amaz-
       ingly powerful tool.

       Consider a couple of scenarios first.

       1) Two directory servers  share  two  levels  of  naming  context;  say
       "dc=a,dc=foo,dc=com"  and  "dc=b,dc=foo,dc=com".   Then, an unambiguous
       Meta database can be configured as:

              database meta
              suffix   "dc=foo,dc=com"
              uri      "ldap://a.foo.com/dc=a,dc=foo,dc=com"
              uri      "ldap://b.foo.com/dc=b,dc=foo,dc=com"

       Operations directed to a specific target can be easily resolved because
       there  are no ambiguities.  The only operation that may resolve to mul-
       tiple targets is a search with base "dc=foo,dc=com" and scope at  least
       "one", which results in spawning two searches to the targets.

       2a)  Two  directory  servers don't share any portion of naming context,
       but they'd present as a single DIT [Caveat:  uniqueness  of  (massaged)
       entries  among  the  two  servers  is assumed; integrity checks risk to
       incur in excessive overhead and have not  been  implemented].   Say  we
       have  "dc=bar,dc=org" and "o=Foo,c=US", and we'd like them to appear as
       branches   of    "dc=foo,dc=com",    say    "dc=a,dc=foo,dc=com"    and
       "dc=b,dc=foo,dc=com".  Then we need to configure our Meta backend as:

              database      meta
              suffix        "dc=foo,dc=com"

              uri           "ldap://a.bar.com/dc=a,dc=foo,dc=com"
              suffixmassage "dc=a,dc=foo,dc=com" "dc=bar,dc=org"

              uri           "ldap://b.foo.com/dc=b,dc=foo,dc=com"
              suffixmassage "dc=b,dc=foo,dc=com" "o=Foo,c=US"

       Again,  operations  can  be  resolved  without ambiguity, although some
       rewriting is required.  Notice that the virtual naming context of  each
       target  is  a  branch of the database's naming context; it is rewritten
       back and  forth  when  operations  are  performed  towards  the  target
       servers.  What "back and forth" means will be clarified later.

       When  a  search with base "dc=foo,dc=com" is attempted, if the scope is
       "base" it fails with "no such object"; in fact, the common root of  the
       two  targets  (prior  to  massaging)  does  not exist.  If the scope is
       "one", both targets are contacted with the base replaced by  each  tar-
       get's  base; the scope is derated to "base".  In general, a scope "one"
       search is honored, and the scope is derated,  only  when  the  incoming
       base  is at most one level lower of a target's naming context (prior to
       massaging).

       Finally, if the scope is "sub" the incoming base is  replaced  by  each
       target's unmassaged naming context, and the scope is not altered.

       2b)  Consider  the above reported scenario with the two servers sharing
       the same naming context:

              database      meta
              suffix        "dc=foo,dc=com"

              uri           "ldap://a.bar.com/dc=foo,dc=com"
              suffixmassage "dc=foo,dc=com" "dc=bar,dc=org"

              uri           "ldap://b.foo.com/dc=foo,dc=com"
              suffixmassage "dc=foo,dc=com" "o=Foo,c=US"

       All the previous considerations hold, except that now there is  no  way
       to  unambiguously  resolve a DN.  In this case, all the operations that
       require an unambiguous target selection will  fail  unless  the  DN  is
       already  cached or a default target has been set.  Practical configura-
       tions may result as a combination of all the above scenarios.


ACLs

       Note on ACLs: at present you may add whatever ACL rule you desire to to
       the  Meta  (and  LDAP)  backends.   However, the meaning of an ACL on a
       proxy may require some considerations.  Two philosophies may be consid-
       ered:

       a)  the remote server dictates the permissions; the proxy simply passes
       back what it gets from the remote server.

       b) the remote server unveils "everything"; the proxy is responsible for
       protecting data from unauthorized access.

       Of  course the latter sounds unreasonable, but it is not.  It is possi-
       ble to imagine scenarios in which a remote host discloses data that can
       be considered "public" inside an intranet, and a proxy that connects it
       to the internet may impose additional constraints.   To  this  purpose,
       the  proxy  should be able to comply with all the ACL matching criteria
       that the server supports.  This has been achieved with  regard  to  all
       the  criteria  supported  by slapd except a special subtle case (please
       drop me a note if you can find other exceptions:  <ando@openldap.org>).
       The rule

              access to dn="<dn>" attr=<attr>
                     by dnattr=<dnattr> read
                     by * none

       cannot be matched iff the attribute that is being requested, <attr>, is
       NOT <dnattr>, and the attribute that determines  membership,  <dnattr>,
       has not been requested (e.g. in a search)

       In  fact  this  ACL  is resolved by slapd using the portion of entry it
       retrieved from the remote server without requiring any  further  inter-
       vention  of  the  backend,  so,  if the <dnattr> attribute has not been
       fetched, the match cannot be assessed  because  the  attribute  is  not
       present, not because no value matches the requirement!

       Note  on  ACLs  and  attribute  mapping: ACLs are applied to the mapped
       attributes; for instance, if the attribute locally known  as  "foo"  is
       mapped  to "bar" on a remote server, then local ACLs apply to attribute
       "foo" and are totally unaware of its remote name.   The  remote  server
       will  check  permissions  for "bar", and the local server will possibly
       enforce additional restrictions to "foo".


REWRITING

       A string is rewritten according to a set of rules,  called  a  `rewrite
       context'.   The  rules  are  based on Regular Expressions (POSIX regex)
       with substring matching; basic variable substitution and map resolution
       of substrings is allowed by specific mechanisms detailed in the follow-
       ing.  The behavior of pattern matching/substitution can be altered by a
       set of flags.

       The underlying concept is to build a lightweight rewrite module for the
       slapd server (initially dedicated to the LDAP backend).


Passes

       An incoming string is matched agains a set of rules.  Rules are made of
       a  regex  match  pattern,  a substitution pattern and a set of actions,
       described by a set of flags.  In case of match a  string  rewriting  is
       performed according to the substitution pattern that allows to refer to
       substrings matched in the incoming string.  The actions,  if  any,  are
       finally  performed.   The substitution pattern allows map resolution of
       substrings.  A map is a generic object that maps a substitution pattern
       to  a  value.   The  flags  are divided in "Pattern matching Flags" and
       "Action Flags"; the former alter  the  regex  match  pattern  behaviorm
       while the latter alter the action that is taken after substitution.


Pattern Matching Flags

       `C'    honors case in matching (default is case insensitive)

       `R'    use POSIX Basic Regular Expressions (default is Extended)

       `M{n}' allow  no more than n recursive passes for a specific rule; does
              not alter the max total count of passes, so it can only  enforce
              a stricter limit for a specific rule.


Action Flags

       `:'    apply the rule once only (default is recursive)

       `@'    stop  applying rules in case of match; the current rule is still
              applied recursively; combine with `:' to apply the current  rule
              only once and then stop.

       `#'    stop  current  operation  if  the  rule  matches,  and  issue an
              `unwilling to perform' error.

       `G{n}' jump n rules back and  forth  (watch  for  loops!).   Note  that
              `G{1}' is implicit in every rule.

       `I'    ignores  errors  in  rule;  this  means,  in case of error, e.g.
              issued by a map, the error is treated as a  missed  match.   The
              `unwilling to perform' is not overridden.

       `U{n}' uses  n  as  return  code if the rule matches; the flag does not
              alter the recursive behavior of the rule, so, to  have  it  per-
              formed  only once, it must be used in combination with `:', e.g.
              `:U{16}' returns the value `16' after exactly one  execution  of
              the  rule, if the pattern matches.  As a consequence, its behav-
              ior is equivalent to `@', with the return code set to n; or,  in
              other  words,  `@'  is equivalent to `U{0}'.  By convention, the
              freely available codes are above 16  included;  the  others  are
              reserved.

       The  ordering  of  the flags can be significant.  For instance: `IG{2}'
       means ignore errors and jump two lines ahead both in case of match  and
       in case of error, while `G{2}I' means ignore errors, but jump two lines
       ahead only in case of match.

       More flags (mainly Action Flags) will be added as needed.


Pattern matching:

       See regex(7).


Substitution Pattern Syntax:

       Everything starting with `%' requires substitution;

       the only obvious exception is `%%', which is left as is;

       the basic substitution is `%d', where `d' is a digit; 0 means the whole
       string, while 1-9 is a submatch, as discussed in regex(7);

       a  `%' followed by a `{' invokes an advanced substitution.  The pattern
       is:

              `%' `{' [ <op> ] <name> `(' <substitution> `)' `}'

       where <name> must be a legal name for the map, i.e.

              <name> ::= [a-z][a-z0-9]* (case insensitive)
              <op> ::= `>' `|' `&' `&&' `*' `**' `$'

       and <substitution> must be a legal substitution pattern, with no limits
       on the nesting level.

       The operators are:

       >      sub  context invocation; <name> must be a legal, already defined
              rewrite context name

       |      external command invocation;  <name>  must  refer  to  a  legal,
              already defined command name (NOT IMPL.)

       &      variable  assignment;  <name>  defines a variable in the running
              operation structure which can be dereferenced later; operator  &
              assigns  a  variable  in  the rewrite context scope; operator &&
              assigns a variable that scopes  the  entire  session,  e.g.  its
              value can be derefenced later by other rewrite contexts

       *      variable  dereferencing; <name> must refer to a variable that is
              defined and assigned  for  the  running  operation;  operator  *
              dereferences a variable scoping the rewrite context; operator **
              dereferences a variable scoping  the  whole  session,  e.g.  the
              value is passed across rewrite contexts

       $      parameter dereferencing; <name> must refer to an existing param-
              eter; the idea is to make some run-time parameters  set  by  the
              system available to the rewrite engine, as the client host name,
              the bind DN if any, constant parameters  initialized  at  config
              time,  and  so  on;  no  parameter  is  currently  set by either
              back-ldap or back-meta, but constant parameters can  be  defined
              in the configuration file by using the rewriteParam directive.

       Substitution  escaping  has  been delegated to the `%' symbol, which is
       used instead of `\' in string  substitution  patterns  because  `\'  is
       already  escaped  by  slapd's  low  level parsing routines; as a conse-
       quence, regex(7) escaping requires two `\' symbols, e.g. `.*\.foo\.bar'
       must be written as `.*\\.foo\\.bar'.


Rewrite context:

       A rewrite context is a set of rules which are applied in sequence.  The
       basic idea is to have an application initialize a rewrite engine (think
       of  Apache's  mod_rewrite  ...)  with  a  set of rewrite contexts; when
       string rewriting is required, one invokes the appropriate rewrite  con-
       text  with  the  input string and obtains the newly rewritten one if no
       errors occur.

       Each basic server operation is associated to a  rewrite  context;  they
       are  divided  in two main groups: client -> server and server -> client
       rewriting.

       client -> server:

              (default)            if defined and no specific context
                                   is available
              bindDN               bind
              searchBase           search
              searchFilter         search
              searchFilterAttrDN   search
              compareDN            compare
              compareAttrDN        compare AVA
              addDN                add
              addAttrDN            add AVA
              modifyDN             modify
              modifyAttrDN         modify AVA
              modrDN               modrdn
              newSuperiorDN        modrdn
              deleteDN             delete
              exopPasswdDN         passwd exop DN if proxy

       server -> client:

              searchResult         search (only if defined; no default;
                                   acts on DN and DN-syntax attributes
                                   of search results)
              searchAttrDN         search AVA
              matchedDN            all ops (only if applicable)


Basic configuration syntax

       rewriteEngine { on | off }
              If `on', the requested rewriting  is  performed;  if  `off',  no
              rewriting  takes  place  (an  easy way to stop rewriting without
              altering too much the configuration file).

       rewriteContext <context name> [ alias <aliased context name> ]
              <Context name> is the name that identifies the context, i.e. the
              name  used  by  the  application to refer to the set of rules it
              contains.  It is used also to reference sub contexts  in  string
              rewriting.   A context may aliase another one.  In this case the
              alias context contains no rule, and any  reference  to  it  will
              result in accessing the aliased one.

       rewriteRule <regex match pattern> <substitution pattern> [ <flags> ]
              Determines  how  a  string  can  be  rewritten  if  a pattern is
              matched.  Examples are reported below.


Additional configuration syntax:

       rewriteMap <map type> <map name> [ <map attrs> ]
              Allows to define a map that transforms substring rewriting  into
              something  else.   The map is referenced inside the substitution
              pattern of a rule.

       rewriteParam <param name> <param value>
              Sets a value with global scope, that can be dereferenced by  the
              command `%{$paramName}'.

       rewriteMaxPasses <number of passes> [<number of passes per rule>]
              Sets  the  maximum  number of total rewriting passes that can be
              performed in a single rewrite operation  (to  avoid  loops).   A
              safe  default  is  set  to 100; note that reaching this limit is
              still treated as a success; recursive  invocation  of  rules  is
              simply  interrupted.   The count applies to the rewriting opera-
              tion as a whole, not to any single rule;  an  optional  per-rule
              limit  can be set.  This limit is overridden by setting specific
              per-rule limits with the `M{n}' flag.


Configuration examples:

       # set to `off' to disable rewriting
       rewriteEngine on

       # the rules the "suffixmassage" directive implies
       rewriteEngine on
       # all dataflow from client to server referring to DNs
       rewriteContext default
       rewriteRule "(.*)<virtualnamingcontext>$" "%1<realnamingcontext>" ":"
       # empty filter rule
       rewriteContext searchFilter
       # all dataflow from server to client
       rewriteContext searchResult
       rewriteRule "(.*)<realnamingcontext>$" "%1<virtualnamingcontext>" ":"
       rewriteContext searchAttrDN alias searchResult
       rewriteContext matchedDN alias searchResult

       # Everything defined here goes into the `default' context.
       # This rule changes the naming context of anything sent
       # to `dc=home,dc=net' to `dc=OpenLDAP, dc=org'

       rewriteRule "(.*)dc=home,[ ]?dc=net"
                   "%1dc=OpenLDAP, dc=org"  ":"

       # since a pretty/normalized DN does not include spaces
       # after rdn separators, e.g. `,', this rule suffices:

       rewriteRule "(.*)dc=home,dc=net"
                   "%1dc=OpenLDAP,dc=org"  ":"

       # Start a new context (ends input of the previous one).
       # This rule adds blanks between DN parts if not present.
       rewriteContext  addBlanks
       rewriteRule     "(.*),([^ ].*)" "%1, %2"

       # This one eats blanks
       rewriteContext  eatBlanks
       rewriteRule     "(.*),[ ](.*)" "%1,%2"

       # Here control goes back to the default rewrite
       # context; rules are appended to the existing ones.
       # anything that gets here is piped into rule `addBlanks'
       rewriteContext  default
       rewriteRule     ".*" "%{>addBlanks(%0)}" ":"

       # Rewrite the search base according to `default' rules.
       rewriteContext  searchBase alias default

       # Search results with OpenLDAP DN are rewritten back with
       # `dc=home,dc=net' naming context, with spaces eaten.
       rewriteContext  searchResult
       rewriteRule     "(.*[^ ]?)[ ]?dc=OpenLDAP,[ ]?dc=org"
                       "%{>eatBlanks(%1)}dc=home,dc=net"    ":"

       # Bind with email instead of full DN: we first need
       # an ldap map that turns attributes into a DN (the
       # argument used when invoking the map is appended to
       # the URI and acts as the filter portion)
       rewriteMap ldap attr2dn "ldap://host/dc=my,dc=org?dn?sub"

       # Then we need to detect DN made up of a single email,
       # e.g. `mail=someone@example.com'; note that the rule
       # in case of match stops rewriting; in case of error,
       # it is ignored.  In case we are mapping virtual
       # to real naming contexts, we also need to rewrite
       # regular DNs, because the definition of a bindDn
       # rewrite context overrides the default definition.
       rewriteContext bindDN
       rewriteRule "^mail=[^,]+@[^,]+$" "%{attr2dn(%0)}" ":@I"

       # This is a rather sophisticated example. It massages a
       # search filter in case who performs the search has
       # administrative privileges.  First we need to keep
       # track of the bind DN of the incoming request, which is
       # stored in a variable called `binddn' with session scope,
       # and left in place to allow regular binding:
       rewriteContext  bindDN
       rewriteRule     ".+" "%{&&binddn(%0)}%0" ":"

       # A search filter containing `uid=' is rewritten only
       # if an appropriate DN is bound.
       # To do this, in the first rule the bound DN is
       # dereferenced, while the filter is decomposed in a
       # prefix, in the value of the `uid=<arg>' AVA, and
       # in a suffix. A tag `<>' is appended to the DN.
       # If the DN refers to an entry in the `ou=admin' subtree,
       # the filter is rewritten OR-ing the `uid=<arg>' with
       # `cn=<arg>'; otherwise it is left as is. This could be
       # useful, for instance, to allow apache's auth_ldap-1.4
       # module to authenticate users with both `uid' and
       # `cn', but only if the request comes from a possible
       # `cn=Web auth,ou=admin,dc=home,dc=net' user.
       rewriteContext searchFilter
       rewriteRule "(.*\\()uid=([a-z0-9_]+)(\\).*)"
         "%{**binddn}<>%{&prefix(%1)}%{&arg(%2)}%{&suffix(%3)}"
         ":I"
       rewriteRule "[^,]+,ou=admin,dc=home,dc=net"
         "%{*prefix}|(uid=%{*arg})(cn=%{*arg})%{*suffix}" ":@I"
       rewriteRule ".*<>" "%{*prefix}uid=%{*arg}%{*suffix}" ":"

       # This example shows how to strip unwanted DN-valued
       # attribute values from a search result; the first rule
       # matches DN values below "ou=People,dc=example,dc=com";
       # in case of match the rewriting exits successfully.
       # The second rule matches everything else and causes
       # the value to be rejected.
       rewriteContext searchResult
       rewriteRule ".*,ou=People,dc=example,dc=com" "%0" ":@"
       rewriteRule ".*" "" "#"


LDAP Proxy resolution (a possible evolution of slapd-ldap(5)):

       In case the rewritten DN is an LDAP URI,  the  operation  is  initiated
       towards  the  host[:port] indicated in the uri, if it does not refer to
       the local server.  E.g.:

         rewriteRule '^cn=root,.*' '%0'                     'G{3}'
         rewriteRule '^cn=[a-l].*' 'ldap://ldap1.my.org/%0' ':@'
         rewriteRule '^cn=[m-z].*' 'ldap://ldap2.my.org/%0' ':@'
         rewriteRule '.*'          'ldap://ldap3.my.org/%0' ':@'

       (Rule 1 is simply there to illustrate the `G{n}' action; it could  have
       been written:

         rewriteRule '^cn=root,.*' 'ldap://ldap3.my.org/%0' ':@'

       with the advantage of saving one rewrite pass ...)


PROXY CACHE OVERLAY

       The  proxy  cache  overlay  allows  caching  of  LDAP  search  requests
       (queries) in a local database.  For an incoming query, the proxy  cache
       determines its corresponding template. If the template was specified as
       cacheable using the proxytemplate directive and  the  request  is  con-
       tained in a cached request, it is answered from the proxy cache. Other-
       wise, the search is performed as usual and cacheable search results are
       saved in the cache for use in future queries.

       A template is defined by a filter string and an index identifying a set
       of attributes. The template string for  a  query  can  be  obtained  by
       removing  assertion  values  from  the  RFC  2254 representation of its
       search filter. A query belongs to a template if its template string and
       set  of  projected attributes correspond to a cacheable template. Exam-
       ples of template strings  are  (mail=),  (|(sn=)(cn=)),  (&(sn=)(given-
       Name=)).

       The  following  cache  specific directives can be used to configure the
       proxy cache:

       overlay proxycache
              This directive adds the proxycache overlay to the current  back-
              end.  The proxycache overlay may be used with any backend but is
              intended for use with the ldap and meta backends.

       proxycache   <database>   <max_entries>   <numattrsets>   <entry_limit>
       <cc_period>
              The directive enables proxy caching in the current  backend  and
              sets general cache parameters. A <database> backend will be used
              internally to maintain the cached entries. The  chosen  database
              will  need  to  be  configured  as  well,  as shown below. Cache
              replacement  is  invoked  when   the   cache   size   grows   to
              <max_entries>  entries  and  continues till the cache size drops
              below this size.  <numattrsets> should be equal to the number of
              following  proxyattrset  directives.  Queries are cached only if
              they correspond to a cacheable template (specified by the  prox-
              ytemplate  directive) and the number of entries returned is less
              than  <entry_limit>.  Consistency  check  is   performed   every
              <cc_period>  duration (specified in secs). In each cycle queries
              with expired "time to live(TTL)" are  removed.  A  sample  cache
              configuration is:

              proxycache bdb 10000 1 50 100

       proxyattrset <index> <attrs...>
              Used to associate a set of attributes <attrs..> with an <index>.
              Each attribute set is associated  with  an  integer  from  0  to
              <numattrsets>-1.  These  indices  are  used by the proxytemplate
              directive to define cacheable templates.

       proxytemplate <template_string> <attrset_index> <ttl>
              Specifies a cacheable template and "time to live" (in sec) <ttl>
              of queries belonging to the template.

       The  following  adds  a template with filter string (&sn=)(givenName=))
       and attributes mail, postaladdress, telephonenumber  and  a  TTL  of  1
       hour.

              proxyattrset 0 mail postaladdress telephonenumber
              proxytemplate (&(sn=)(givenName=)) 0 3600

       Directives  for configuring the underlying database must also be given,
       as shown here:

              directory /var/tmp/cache
              cachesize 100

       Any valid directives for the chosen database type may be used.


FILES

       /etc/openldap/slapd.conf
              default slapd configuration file


SEE ALSO

       slapd.conf(5), slapd-ldap(5), slapd(8), regex(7).


AUTHOR

       Pierangelo Masarati, based on back-ldap by Howard Chu

OpenLDAP 2.2.30                   2005/11/18                     SLAPD-META(5)

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