Provided by: slapd_2.4.28-1.1ubuntu4_amd64 bug

NAME

       slapo-rwm - rewrite/remap overlay to slapd

SYNOPSIS

       /etc/ldap/slapd.conf

DESCRIPTION

       The  rwm  overlay to slapd(8) performs basic DN/data rewrite and objectClass/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.

MAPPING

       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  attributeTypes  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 mapping 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 results, when the rwm overlay  is  used  together
       with  e.g.  the  pcache  overlay.  This  normalization  can  be  enabled  by  means of the
       rwm-normalize-mapped-attrs directive.

       rwm-normalize-mapped-attrs {yes|no}
              Set this to "yes", if the rwm  overlay  should  try  to  normalize  the  values  of
              attributes  that  are  mapped  from  an attribute type that is unknown to the local
              server. The default value of this setting is "no".

       rwm-drop-unrequested-attrs {yes|no}
              Set this to "yes",  if  the  rwm  overlay  should  drop  attributes  that  are  not
              explicitly  requested  by  a  search  operation.  When this is set to "no", the rwm
              overlay will leave all attributes 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".

SUFFIX MASSAGING

       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  distinguishing
       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 subschemaSubentry DN (usually "cn=subschema"), would prevent clients from
       reading 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-suffixmassage directive be defined after the database  suffix  directive.   The
              rwm-suffixmassage directive automatically sets the rwm-rewriteEngine to ON.

       See the REWRITING section for details.

REWRITING

       A  string is rewritten according to a set of rules, called a `rewrite context'.  The rules
       are based on POSIX (''extended'')  regular  expressions  with  substring  matching;  basic
       variable  substitution  and map resolution 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):

Passes

       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 actions, described by a set of optional
       flags.  In case of match, 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.  Each rule  is  executed  recursively,  unless  altered  by
       specific  action  flags; see "Action Flags" for details.  A default limit on the recursion
       level is set, and can be altered by the rwm-rewriteMaxPasses directive, as detailed in the
       "Additional Configuration Syntax" section.  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 behavior, while the latter alter the  actions  that  are  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 performed 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 `$';

       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) and/or re_format(7).

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

              `$' `{' [ <operator> ] <name> `(' <substitution> `)' `}'

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

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

       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 parameter; 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  consequence,  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 context 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
              searchDN             search
              searchFilter         search
              searchFilterAttrDN   search
              compareDN            compare
              compareAttrDN        compare AVA
              addDN                add
              addAttrDN            add AVA (DN portion of "ref" excluded)
              modifyDN             modify
              modifyAttrDN         modify AVA (DN portion of "ref" excluded)
              referralAttrDN       add/modify DN portion of referrals
                                   (default to none)
              renameDN             modrdn (the old DN)
              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}'.

       rwm-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 operation 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.

MAPS

       Currently, few maps are builtin but additional map types may be registered at runtime.

       Supported maps are:

       LDAP <URI> [bindwhen=<when>] [version=<version>] [binddn=<DN>] [credentials=<cred>]
              The LDAP map expands a value by performing a simple LDAP search.  Its configuration
              is based on a mandatory URI, whose attrs portion 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 established.  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 anonymous 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 portion must contain exactly one attribute, and if a  multi-valued  attribute
              is used, only the first value is considered.

REWRITE CONFIGURATION EXAMPLES

       # 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
       # misc empty rules
       rwm-rewriteContext referralAttrDN
       rwm-rewriteContext referralDN

       # 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'

       rwm-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:

       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. `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.
       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" ":"

       # 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.
       rwm-rewriteContext searchFilter
       rwm-rewriteRule "(.*\\()uid=([a-z0-9_]+)(\\).*)"
         "${**binddn}<>${&prefix($1)}${&arg($2)}${&suffix($3)}"
         ":I"
       rwm-rewriteRule "^[^,]+,ou=admin,dc=home,dc=net$"
         "${*prefix}|(uid=${*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 ".*" "" "#"

MAPPING EXAMPLES

       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.

FILES

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

SEE ALSO

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

AUTHOR

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