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           The  rwm overlay to slapd(8) performs basic DN/data rewrite and object-
           Class/attributeType mapping.  Its usage is mostly intended  to  provide
           virtual views of existing data either remotely, in conjunction with the
           proxy backend described in slapd-ldap(5), or  locally,  in  conjunction
           with the relay backend described in slapd-relay(5).
           This overlay is experimental.


           An  important  feature  of  the  rwm  overlay  is the capability to map
           objectClasses and attributeTypes from the local set (or a subset of it)
           to a foreign set, and vice versa.  This is accomplished by means of the
           rwm-map directive.
           rwm-map {attribute | objectclass} [<local name> | *] {<foreign name>  |
                  Map attributeTypes and objectClasses from the foreign server  to
                  different  values  on  the local slapd.  The reason is that some
                  attributes might not be part of the local slapd's  schema,  some
                  attribute  names  might be different but serve the same purpose,
                  etc.  If local or foreign name is '*', the  name  is  preserved.
                  If local name is omitted, the foreign name is removed.  Unmapped
                  names are preserved if both local and foreign name are '*',  and
                  removed if local name is omitted and foreign name is '*'.
           The local objectClasses and attributeTypes must be defined in the local
           schema; the foreign ones do not have to, but users  are  encouraged  to
           explicitly  define the remote attributeTypes and the objectClasses they
           intend to map.  All in all, when remapping a remote  server  via  back-
           ldap  (slapd-ldap(5)) or back-meta (slapd-meta(5)) their definition can
           be easily obtained by querying  the  subschemaSubentry  of  the  remote
           server;  the  problem should not exist when remapping a local database.
           Note, however, that the decision whether to rewrite or  not  attribute-
           Types  with  distinguishedName  syntax,  requires  the knowledge of the
           attributeType syntax.  See the REWRITING section for details.
           Note that when mapping DN-valued attributes from local to remote, first
           the  DN  is rewritten, and then the attributeType is mapped; while map-
           ping from remote to local, first the attributeType is mapped, and  then
           the  DN  is  rewritten.   As  such,  it  is  important  that  the local
           attributeType is appropriately defined as using  the  distinguishedName
           syntax.   Also,  note that there are DN-related syntaxes (i.e. compound
           types with a portion that is DN-valued), like nameAndOptionalUID, whose
           values are currently not rewritten.
           If the foreign type of an attribute mapping is not defined on the local
           server, it might be desirable to have the attribute  values  normalized
           after the mapping process. Not normalizing the values can lead to wrong
                  in place, so that  subsequent  modules  can  further  manipulate
                  them.   In any case, unrequested attributes will be omitted from
                  search results by the frontend, when the search  entry  response
                  package is encoded.  The default value of this setting is "yes".


           A basic feature of the rwm overlay is the capability to perform  suffix
           massaging  between  a virtual and a real naming context by means of the
           rwm-suffixmassage directive.  This, in conjunction with proxy backends,
           slapd-ldap(5)   and   slapd-meta(5),   or   with   the  relay  backend,
           slapd-relay(5), allows to create virtual views of databases.  A distin-
           guishing  feature of this overlay is that, when instantiated before any
           database, it can modify the DN of requests before  database  selection.
           For this reason, rules that rewrite the empty DN ("") or the subschema-
           Subentry DN (usually "cn=subschema"), would prevent clients from  read-
           ing the root DSE or the DSA's schema.
           rwm-suffixmassage [<virtual naming context>] <real naming context>
                  Shortcut  to  implement  naming  context rewriting; the trailing
                  part of the DN is rewritten from the virtual to the real  naming
                  context  in the bindDN, searchDN, searchFilterAttrDN, compareDN,
                  compareAttrDN, addDN, addAttrDN, modifyDN, modifyAttrDN, modrDN,
                  newSuperiorDN,  deleteDN, exopPasswdDN, and from the real to the
                  virtual naming context in the  searchEntryDN,  searchAttrDN  and
                  matchedDN  rewrite contexts.  By default no rewriting occurs for
                  the searchFilter  and  for  the  referralAttrDN  and  referralDN
                  rewrite  contexts.  If no <virtual naming context> is given, the
                  first suffix of the database is used; this requires the rwm-suf-
                  fixmassage directive be defined after the database suffix direc-
                  tive.  The rwm-suffixmassage directive  automatically  sets  the
                  rwm-rewriteEngine to ON.
           See the REWRITING section for details.


           A  string  is  rewritten according to a set of rules, called a 'rewrite
           context'.  The rules are based on POSIX (''extended'') regular  expres-
           sions with substring matching; basic variable substitution and map res-
           olution of substrings is allowed by specific mechanisms detailed in the
           following.   The  behavior  of  pattern  matching/substitution  can  be
           altered by a set of flags.
                  <rewrite context> ::= <rewrite rule> [...]
                  <rewrite rule> ::= <pattern> <action> [<flags>]
           The underlying concept is to build a lightweight rewrite module for the
           slapd server (initially dedicated to the LDAP backend):


           An incoming string is matched against a set of rewriteRules.  Rules are
           made of a regex match pattern, a substitution  pattern  and  a  set  of

    Pattern Matching Flags

           'C'    honors case in matching (default is case insensitive)
           'R'    use    POSIX   ''basic''   regular   expressions   (default   is
           '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{32}'  returns the value '32' (indicating noSuchObject) after
                  exactly one execution of the rule, if the pattern matches.  As a
                  consequence,  its behavior is equivalent to '@', with the return
                  code set to n; or, in other words, '@' is equivalent to  'U{0}'.
                  Positive  errors  are allowed, indicating the related LDAP error
                  codes as specified in draft-ietf-ldapbis-protocol.
           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) and/or re_format(7).

    Substitution Pattern Syntax

           Everything starting with '$' requires substitution;
           the only obvious exception is '$$', which is turned into a single '$';
           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 IMPLEMENTED YET)
           &      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 dereferenced 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 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
           client -> server:
                  (default)            if defined and no specific context
                  newSuperiorDN        modrdn (the new parent DN, if any)
                  newRDN               modrdn (the new relative DN)
                  deleteDN             delete
                  exopPasswdDN         password modify extended operation DN
           server -> client:
                  searchEntryDN        search (only if defined; no default;
                                       acts on DN of search entries)
                  searchAttrDN         search AVA (only if defined; defaults
                                       to searchEntryDN; acts on DN-syntax
                                       attributes of search results)
                  matchedDN            all ops (only if applicable; defaults
                                       to searchEntryDN)
                  referralDN           all ops (only if applicable; defaults
                                       to none)

    Basic Configuration Syntax

           All rewrite/remap directives start with the prefix rwm-; for  backwards
           compatibility  with  the  historical  slapd-ldap(5)  and  slapd-meta(5)
           builtin rewrite/remap capabilities, the prefix may be omitted, but this
           practice is strongly discouraged.
           rwm-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).
           rwm-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 alias another one.  In this  case  the
                  alias  context  contains  no  rule, and any reference to it will
                  result in accessing the aliased one.
           rwm-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

           rwm-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.
           rwm-rewriteParam <param name> <param value>
                  Sets  a value with global scope, that can be dereferenced by the
                  command '${$paramName}'.
           Supported maps are:
           LDAP <URI> [bindwhen=<when>] [version=<version>] [binddn=<DN>] [creden-
                  The LDAP map expands a value by performing a simple LDAP search.
                  Its  configuration is based on a mandatory URI, whose attrs por-
                  tion must contain exactly one attribute (use  entryDN  to  fetch
                  the  DN of an entry).  If a multi-valued attribute is used, only
                  the first value is considered.
                  The parameter bindwhen determines when the connection is  estab-
                  lished.   It  can  take  the  values  now, later, and everytime,
                  respectively indicating that the connection should be created at
                  startup,  when  required, or any time it is used.  In the former
                  two cases, the connection is cached, while in the latter a fresh
                  new one is used all times.  This is the default.
                  The  parameters  binddn and credentials represent the DN and the
                  password that is used to perform an  authenticated  simple  bind
                  before  performing the search operation; if not given, an anony-
                  mous connection is used.
                  The parameter version can be 2 or 3  to  indicate  the  protocol
                  version that must be used.  The default is 3.
           slapd <URI>
                  The  slapd  map  expands  a value by performing an internal LDAP
                  search.  Its configuration is based on a  mandatory  URI,  which
                  must  begin  with  ldap:/// (i.e., it must be an LDAP URI and it
                  must not specify a host).  As with the LDAP map, the attrs  por-
                  tion  must  contain exactly one attribute, and if a multi-valued
                  attribute is used, only the first value is considered.


           # set to 'off' to disable rewriting
           rwm-rewriteEngine on
           # the rules the "suffixmassage" directive implies
           rwm-rewriteEngine on
           # all dataflow from client to server referring to DNs
           rwm-rewriteContext default
           rwm-rewriteRule "(.+,)?<virtualnamingcontext>$" "$1<realnamingcontext>" ":"
           # empty filter rule
           rwm-rewriteContext searchFilter
           # all dataflow from server to client
           rwm-rewriteContext searchEntryDN
           rwm-rewriteRule "(.+,)?<realnamingcontext>$" "$1<virtualnamingcontext>" ":"
           rwm-rewriteContext searchAttrDN alias searchEntryDN
           rwm-rewriteContext matchedDN alias searchEntryDN
           rwm-rewriteRule "(.+,)?dc=home,dc=net$"
                       "$1dc=OpenLDAP,dc=org"  ":"
           # Start a new context (ends input of the previous one).
           # This rule adds blanks between DN parts if not present.
           rwm-rewriteContext  addBlanks
           rwm-rewriteRule     "(.*),([^ ].*)" "$1, $2"
           # This one eats blanks
           rwm-rewriteContext  eatBlanks
           rwm-rewriteRule     "(.*), (.*)" "$1,$2"
           # Here control goes back to the default rewrite
           # context; rules are appended to the existing ones.
           # anything that gets here is piped into rule 'addBlanks'
           rwm-rewriteContext  default
           rwm-rewriteRule     ".*" "${>addBlanks($0)}" ":"
           # Rewrite the search base according to 'default' rules.
           rwm-rewriteContext  searchDN alias default
           # Search results with OpenLDAP DN are rewritten back with
           # 'dc=home,dc=net' naming context, with spaces eaten.
           rwm-rewriteContext  searchEntryDN
           rwm-rewriteRule     "(.*[^ ],)?[ ]?dc=OpenLDAP,[ ]?dc=org$"
                           "${>eatBlanks($1)}dc=home,dc=net"    ":"
           # Bind with email instead of full DN: we first need
           # an ldap map that turns attributes into a DN (the
           # argument used when invoking the map is appended to
           # the URI and acts as the filter portion)
           rwm-rewriteMap ldap attr2dn "ldap://host/dc=my,dc=org?dn?sub"
           # Then we need to detect DN made up of a single email,
           # e.g. ''; note that the rule
           # in case of match stops rewriting; in case of error,
           # it is ignored.  In case we are mapping virtual
           # to real naming contexts, we also need to rewrite
           # regular DNs, because the definition of a bindDN
           # rewrite context overrides the default definition.
           rwm-rewriteContext bindDN
           rwm-rewriteRule "^mail=[^,]+@[^,]+$" "${attr2dn($0)}" ":@I"
           # This is a rather sophisticated example. It massages a
           # search filter in case who performs the search has
           # administrative privileges.  First we need to keep
           # track of the bind DN of the incoming request, which is
           # stored in a variable called 'binddn' with session scope,
           # and left in place to allow regular binding:
           rwm-rewriteContext  bindDN
           rwm-rewriteRule     ".+" "${&&binddn($0)}$0" ":"
           rwm-rewriteRule "(.*\\()uid=([a-z0-9_]+)(\\).*)"
           rwm-rewriteRule "^[^,]+,ou=admin,dc=home,dc=net$"
             "${*prefix}|(uid=${*arg})(cn=${*arg})${*suffix}" ":@I"
           rwm-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.
           rwm-rewriteContext searchEntryDN
           rwm-rewriteRule ".+,ou=People,dc=example,dc=com$" "$0" ":@"
           rwm-rewriteRule ".*" "" "#"


           The following directives map the object  class  'groupOfNames'  to  the
           object  class  'groupOfUniqueNames'  and the attribute type 'member' to
           the attribute type 'uniqueMember':
                  map objectclass groupOfNames groupOfUniqueNames
                  map attribute uniqueMember member
           This presents a limited attribute set from the foreign server:
                  map attribute cn *
                  map attribute sn *
                  map attribute manager *
                  map attribute description *
                  map attribute *
           These lines map cn, sn, manager, and description to themselves, and any
           other attribute gets "removed" from the object before it is sent to the
           client (or sent up to the LDAP server).  This is obviously a simplistic
           example, but you get the point.


                  default slapd configuration file


           slapd.conf(5),     slapd-config(5),    slapd-ldap(5),    slapd-meta(5),
           slapd-relay(5), slapd(8), regex(7), re_format(7).


           Pierangelo Masarati;  based  on  back-ldap  rewrite/remap  features  by
           Howard Chu, Pierangelo Masarati.

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