slapo-rwm.5

ldap服务器源码

.TH SLAPO-RWM 5 "RELEASEDATE" "OpenLDAP LDVERSION"
.\" Copyright 1998-2007 The OpenLDAP Foundation, All Rights Reserved.
.\" Copying restrictions apply.  See the COPYRIGHT file.
.\" Copyright 2004, Pierangelo Masarati, All rights reserved. <[e-mail]>
.\" $OpenLDAP: pkg/ldap/doc/man/man5/slapo-rwm.5,v 1.8.2.7 2007/01/02 21:43:45 kurt Exp $
.\"
.\" Portions of this document should probably be moved to slapd-ldap(5)
.\" and maybe manual pages for librewrite.
.\"
.SH NAME
slapo-rwm \- rewrite/remap overlay
.SH SYNOPSIS
ETCDIR/slapd.conf
.SH DESCRIPTION
The
.B rwm
overlay to
.BR 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
.BR slapd-ldap (5),
or locally, in conjunction with the relay backend described in
.BR slapd-relay (5).
.LP
This overlay is experimental.
.SH MAPPING
An important feature of the
.B 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 
.B rwm-map
directive.
.TP
.B 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 `*'.
.LP
The local 
.I objectClasses 
and 
.I 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 (\fBslapd-ldap\fP(5)) 
or back-meta (\fBslapd-meta\fP(5))
their definition can be easily obtained by querying the \fIsubschemaSubentry\fP
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 
.IR "distinguishedName syntax" ,
requires the knowledge of the attributeType syntax.
See the REWRITING section for details.
.LP
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.
.SH SUFFIX MASSAGING
A basic feature of the
.B rwm
overlay is the capability to perform suffix massaging between a virtual
and a real naming context by means of the 
.B rwm-suffixmassage
directive.
.TP
.B 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 \fI<virtual naming context>\fP is given, the first suffix of the
database is used; this requires the 
.B rwm-suffixmassage
directive be defined \fIafter\fP the database
.B suffix
directive.
The
.B rwm-suffixmassage
directive automatically sets the
.B rwm-rewriteEngine
to
.BR ON .
.LP
See the REWRITING section for details.
.SH 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.
.LP
.RS
.nf
<rewrite context> ::= <rewrite rule> [...]
<rewrite rule> ::= <pattern> <action> [<flags>]
.fi
.RE
.LP
The underlying concept is to build a lightweight rewrite module
for the slapd server (initially dedicated to the LDAP backend):
.LP
.SH Passes
An incoming string is matched against a set of
.IR rewriteRules .
Rules are made of a 
.IR "regex match pattern" , 
a 
.I "substitution pattern"
and a set of actions, described by a set of 
.IR "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
.B 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.
.SH "Pattern Matching Flags"
.TP
.B `C'
honors case in matching (default is case insensitive)
.TP
.B `R'
use POSIX ''basic'' regular expressions (default is ''extended'')
.TP
.B `M{n}'
allow no more than
.B 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.
.SH "Action Flags"
.TP
.B `:'
apply the rule once only (default is recursive)
.TP
.B `@'
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.
.TP
.B `#'
stop current operation if the rule matches, and issue an `unwilling to
perform' error.
.TP
.B `G{n}'
jump
.B n
rules back and forth (watch for loops!).
Note that `G{1}' is implicit in every rule.
.TP
.B `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.
.TP
.B `U{n}'
uses
.B
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.
.B `: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
.BR n ;
or, in other words, `@' is equivalent to `U{0}'.
Positive errors are allowed, indicating the related LDAP error codes
as specified in \fIdraft-ietf-ldapbis-protocol\fP.
.LP
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.
.LP
More flags (mainly Action Flags) will be added as needed.
.SH "Pattern Matching"
See
.BR regex (7)
and/or
.BR re_format (7).
.SH "Substitution Pattern Syntax"
Everything starting with `$' requires substitution;
.LP
the only obvious exception is `$$', which is turned into a single `$';
.LP
the basic substitution is `$<d>', where `<d>' is a digit;
0 means the whole string, while 1-9 is a submatch, as discussed in 
.BR regex (7)
and/or
.BR re_format (7).
.LP
a `$' followed by a `{' invokes an advanced substitution.
The pattern is:
.LP
.RS
`$' `{' [ <operator> ] <name> `(' <substitution> `)' `}'
.RE
.LP
where <name> must be a legal name for the map, i.e.
.LP
.RS
.nf
<name> ::= [a-z][a-z0-9]* (case insensitive)
<operator> ::= `>' `|' `&' `&&' `*' `**' `$'
.fi
.RE
.LP
and <substitution> must be a legal substitution
pattern, with no limits on the nesting level.
.LP
The operators are:
.TP
.B >
sub-context invocation; <name> must be a legal, already defined
rewrite context name
.TP
.B |
external command invocation; <name> must refer to a legal, already
defined command name (NOT IMPLEMENTED YET)
.TP
.B &
variable assignment; <name> defines a variable in the running
operation structure which can be dereferenced later; operator
.B &
assigns a variable in the rewrite context scope; operator
.B &&
assigns a variable that scopes the entire session, e.g. its value
can be dereferenced later by other rewrite contexts
.TP
.B *
variable dereferencing; <name> must refer to a variable that is
defined and assigned for the running operation; operator
.B *
dereferences a variable scoping the rewrite context; operator
.B **
dereferences a variable scoping the whole session, e.g. the value
is passed across rewrite contexts
.TP
.B $
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 
.B back\-ldap
or
.BR back\-meta ,
but constant parameters can be defined in the configuration file
by using the
.B rewriteParam
directive.
.LP