SLAPD-META(5) File Formats Manual SLAPD-META(5)
slapd-meta - metadirectory backend to slapd
ETCDIR/slapd.conf
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 scenarios will be discussed.
The proxy instance of slapd(8) must contain schema information for
the attributes and objectClasses used in filters, request DN and
request-related data in general. It should also contain schema
information for the data returned by the proxied server. It is the
responsibility of the proxy administrator to keep the schema of the
proxy lined up with that of the proxied server.
Note: When looping back to the same instance of slapd(8), each
connection requires a new thread; as a consequence, slapd(8) must be
compiled with thread support, and the threads parameter may need some
tuning; in those cases, unless the multiple target feature is
required, one may consider using slapd-relay(5) instead, which
performs the relayed operation internally and thus reuses the same
connection.
There are examples in various places in this document, as well as in
the slapd/back-meta/data/ directory in the OpenLDAP source tree.
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: In early versions of back-ldap and back-meta it was recommended
to always set
lastmod off
for ldap and meta databases. This was required because operational
attributes related to entry creation and modification should not be
proxied, as they could be mistakenly written to the target server(s),
generating an error. The current implementation automatically sets
lastmod to off, so its use is redundant and should be omitted.
Target configuration starts with the "uri" directive. All the
configuration directives that are not specific to targets should be
defined first for clarity, including those that are common to all
backends. They are:
conn-ttl <time>
This directive causes a cached connection to be dropped an
recreated after a given ttl, regardless of being idle or not.
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, modrdn; 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 {DISABLED|forever|<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 is
required, in the format illustrated for the idle-timeout
directive.
onerr {CONTINUE|report|stop}
This directive allows one to select the behavior in case an
error is returned by one target during a search. The default,
continue, consists in continuing the operation, trying to
return as much data as possible. If the value is set to stop,
the search is terminated as soon as an error is returned by
one target, and the error is immediately propagated to the
client. If the value is set to report, the search is
continuated to the end but, in case at least one target
returned an error code, the first non-success error code is
returned.
norefs <NO|yes>
If yes, do not return search reference responses. By default,
they are returned unless request is LDAPv2. If set before any
target specification, it affects all targets, unless
overridden by any per-target directive.
noundeffilter <NO|yes>
If yes, return success instead of searching if a filter is
undefined or contains undefined portions. By default, the
search is propagated after replacing undefined portions with
(!(objectClass=*)), which corresponds to the empty result set.
If set before any target specification, it affects all
targets, unless overridden by any per-target directive.
protocol-version {0,2,3}
This directive indicates what protocol version must be used to
contact the remote server. If set to 0 (the default), the
proxy uses the same protocol version used by the client,
otherwise the requested protocol is used. The proxy returns
unwillingToPerform if an operation that is incompatible with
the requested protocol is attempted. If set before any target
specification, it affects all targets, unless overridden by
any per-target directive.
pseudoroot-bind-defer {YES|no}
This directive, when set to yes, causes the authentication to
the remote servers with the pseudo-root identity (the identity
defined in each idassert-bind directive) to be deferred until
actually needed by subsequent operations. Otherwise, all
binds as the rootdn are propagated to the targets.
quarantine <interval>,<num>[;<interval>,<num>[...]]
Turns on quarantine of URIs that returned LDAP_UNAVAILABLE, so
that an attempt to reconnect only occurs at given intervals
instead of any time a client requests an operation. The
pattern is: retry only after at least interval seconds elapsed
since last attempt, for exactly num times; then use the next
pattern. If num for the last pattern is "+", it retries
forever; otherwise, no more retries occur. This directive
must appear before any target specification; it affects all
targets with the same pattern.
rebind-as-user {NO|yes}
If this option is given, the client's bind credentials are
remembered for rebinds, when trying to re-establish a broken
connection, or when chasing a referral, if chase-referrals is
set to yes.
session-tracking-request {NO|yes}
Adds session tracking control for all requests. The client's
IP and hostname, and the identity associated to each request,
if known, are sent to the remote server for informational
purposes. This directive is incompatible with setting
protocol-version to 2. If set before any target
specification, it affects all targets, unless overridden by
any per-target directive.
single-conn {NO|yes}
Discards current cached connection when the client rebinds.
use-temporary-conn {NO|yes}
when set to yes, create a temporary connection whenever
competing with other threads for a shared one; otherwise, wait
until the shared connection is available.
Target specification starts with a "uri" directive:
uri <protocol>://[<host>]/<naming context> [...]
The <protocol> part can be anything ldap_initialize(3) accepts
({ldap|ldaps|ldapi} and variants); the <host> may be omitted,
defaulting to whatever is set in ldap.conf(5). The <naming
context> part is mandatory for the first URI, but it must be
omitted for subsequent ones, if any. The naming context part
must be within the naming context 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. Multiple URIs may be defined in a single URI
statement. The additional URIs must be separate arguments and
must not have any <naming context> part. This causes the
underlying library to contact the first server of the list
that responds. For example, if l1.foo.com and l2.foo.com are
shadows of the same server, the directive
suffix "dc=foo,dc=com"
uri "ldap://l1.foo.com/dc=foo,dc=com" "ldap://l2.foo.com/"
causes l2.foo.com to be contacted whenever l1.foo.com does not
respond. In that case, the URI list is internally rearranged,
by moving unavailable URIs to the end, so that further
connection attempts occur with respect to the last URI that
succeeded.
acl-authcDN <administrative DN for access control purposes>
DN which is used to query the target server for acl checking,
as in the LDAP backend; it is supposed to 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. The acl-authcDN identity
is by no means implicitly used by the proxy when the client
connects anonymously.
acl-passwd <password>
Password used with the acl-authcDN above.
bind-timeout <microseconds>
This directive defines the timeout, in microseconds, used when
polling for response after an asynchronous bind connection.
The initial call to ldap_result(3) is performed with a trade-
off timeout of 100000 us; if that results in a timeout
exceeded, subsequent calls use the value provided with
bind-timeout. The default value is used also for subsequent
calls if bind-timeout is not specified. If set before any
target specification, it affects all targets, unless
overridden by any per-target directive.
chase-referrals {YES|no}
enable/disable automatic referral chasing, which is delegated
to the underlying libldap, with rebinding eventually performed
if the rebind-as-user directive is used. The default is to
chase referrals. If set before any target specification, it
affects all targets, unless overridden by any per-target
directive.
client-pr {accept-unsolicited|DISABLE|<size>}
This feature allows one to use RFC 2696 Paged Results control
when performing search operations with a specific target,
irrespective of the client's request. When set to a numeric
value, Paged Results control is always used with size as the
page size. When set to accept-unsolicited, unsolicited Paged
Results control responses are accepted and honored for
compatibility with broken remote DSAs. The client is not
exposed to paged results handling between slapd-meta(5) and
the remote servers. By default (disabled), Paged Results
control is not used and responses are not accepted. If set
before any target specification, it affects all targets,
unless overridden by any per-target directive.
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.
filter <pattern>
This directive allows specifying a regex(5) pattern to
indicate what search filter terms are actually served by a
target.
In a search request, if the search filter matches the pattern
the target is considered while fulfilling the request;
otherwise the target is ignored. There may be multiple
occurrences of the filter directive for each target.
idassert-authzFrom <authz-regexp>
if defined, selects what local identities are authorized to
exploit the identity assertion feature. The string <authz-
regexp> follows the rules defined for the authzFrom attribute.
See slapd.conf(5), section related to authz-policy, for
details on the syntax of this field.
idassert-bind bindmethod=none|simple|sasl [binddn=<simple DN>]
[credentials=<simple password>] [saslmech=<SASL mech>]
[secprops=<properties>] [realm=<realm>]
[authcId=<authentication ID>] [authzId=<authorization ID>]
[authz={native|proxyauthz}] [mode=<mode>] [flags=<flags>]
[starttls=no|yes|critical] [tls_cert=<file>] [tls_key=<file>]
[tls_cacert=<file>] [tls_cacertdir=<path>]
[tls_reqcert=never|allow|try|demand]
[tls_cipher_suite=<ciphers>]
[tls_protocol_min=<major>[.<minor>]]
[tls_crlcheck=none|peer|all]
Allows one to define the parameters of the authentication
method that is internally used by the proxy to authorize
connections that are authenticated by other databases. The
identity defined by this directive, according to the
properties associated to the authentication method, is
supposed to have auth access on the target server to
attributes used on the proxy for authentication and
authorization, and to be allowed to authorize the users. This
requires to have proxyAuthz privileges on a wide set of DNs,
e.g. authzTo=dn.subtree:"", and the remote server to have
authz-policy set to to or both. See slapd.conf(5) for details
on these statements and for remarks and drawbacks about their
usage. The supported bindmethods are
none|simple|sasl
where none is the default, i.e. no identity assertion is
performed.
The authz parameter is used to instruct the SASL bind to
exploit native SASL authorization, if available; since
connections are cached, this should only be used when
authorizing with a fixed identity (e.g. by means of the
authzDN or authzID parameters). Otherwise, the default
proxyauthz is used, i.e. the proxyAuthz control (Proxied
Authorization, RFC 4370) is added to all operations.
The supported modes are:
<mode> := {legacy|anonymous|none|self}
If <mode> is not present, and authzId is given, the proxy
always authorizes that identity. <authorization ID> can be
u:<user>
[dn:]<DN>
The former is supposed to be expanded by the remote server
according to the authz rules; see slapd.conf(5) for details.
In the latter case, whether or not the dn: prefix is present,
the string must pass DN validation and normalization.
The default mode is legacy, which implies that the proxy will
either perform a simple bind as the authcDN or a SASL bind as
the authcID and assert the client's identity when it is not
anonymous. Direct binds are always proxied. The other modes
imply that the proxy will always either perform a simple bind
as the authcDN or a SASL bind as the authcID, unless
restricted by idassert-authzFrom rules (see below), in which
case the operation will fail; eventually, it will assert some
other identity according to <mode>. Other identity assertion
modes are anonymous and self, which respectively mean that the
empty or the client's identity will be asserted; none, which
means that no proxyAuthz control will be used, so the authcDN
or the authcID identity will be asserted. For all modes that
require the use of the proxyAuthz control, on the remote
server the proxy identity must have appropriate authzTo
permissions, or the asserted identities must have appropriate
authzFrom permissions. Note, however, that the ID assertion
feature is mostly useful when the asserted identities do not
exist on the remote server. When bindmethod is SASL, the
authcDN must be specified in addition to the authcID, although
it is not used within the authentication process.
Flags can be
override,[non-]prescriptive,proxy-authz-[non-]critical
When the override flag is used, identity assertion takes place
even when the database is authorizing for the identity of the
client, i.e. after binding with the provided identity, and
thus authenticating it, the proxy performs the identity
assertion using the configured identity and authentication
method.
When the prescriptive flag is used (the default), operations
fail with inappropriateAuthentication for those identities
whose assertion is not allowed by the idassert-authzFrom
patterns. If the non-prescriptive flag is used, operations
are performed anonymously for those identities whose assertion
is not allowed by the idassert-authzFrom patterns.
When the proxy-authz-non-critical flag is used (the default),
the proxyAuthz control is not marked as critical, in violation
of RFC 4370. Use of proxy-authz-critical is recommended.
The TLS settings default to the same as the main slapd TLS
settings, except for tls_reqcert which defaults to "demand".
The identity associated to this directive is also used for
privileged operations whenever idassert-bind is defined and
acl-bind is not. See acl-bind for details.
idle-timeout <time>
This directive causes a cached connection to be dropped an
recreated after it has been idle for the specified time. The
value can be specified as
[<d>d][<h>h][<m>m][<s>[s]]
where <d>, <h>, <m> and <s> are respectively treated as days,
hours, minutes and seconds. If set before any target
specification, it affects all targets, unless overridden by
any per-target directive.
keepalive <idle>:<probes>:<interval>
The keepalive parameter sets the values of idle, probes, and
interval used to check whether a socket is alive; idle is the
number of seconds a connection needs to remain idle before TCP
starts sending keepalive probes; probes is the maximum number
of keepalive probes TCP should send before dropping the
connection; interval is interval in seconds between individual
keepalive probes. Only some systems support the customization
of these values; the keepalive parameter is ignored otherwise,
and system-wide settings are used.
map {attribute|objectclass} [<local name>|*] {<foreign name>|*}
This maps object classes and attributes as in the LDAP
backend. See slapd-ldap(5).
network-timeout <time>
Sets the network timeout value after which poll(2)/select(2)
following a connect(2) returns in case of no activity. The
value is in seconds, and it can be specified as for
idle-timeout. If set before any target specification, it
affects all targets, unless overridden by any per-target
directive.
nretries {forever|never|<nretries>}
This directive defines how many times a bind should be retried
in case of temporary failure in contacting a target. If
defined before any target specification, it applies to all
targets (by default, 3 times); the global value can be
overridden by redefinitions inside each target specification.
rewrite* ...
The rewrite options are described in the "REWRITING" section.
subtree-{exclude|include} <rule>
This directive allows one to indicate what subtrees are
actually served by a target. The syntax of the supported
rules is
<rule>: [dn[.<style>]:]<pattern>
<style>: subtree|children|regex
When <style> is either subtree or children the <pattern> is a
DN that must be within the naming context served by the
target. When <style> is regex the <pattern> is a regex(5)
pattern. If the dn.<style>: prefix is omitted, dn.subtree: is
implicitly assumed for backward compatibility.
In the subtree-exclude form if the request DN matches at least
one rule, the target is not considered while fulfilling the
request; otherwise, the target is considered based on the
value of the request DN. When the request is a search, also
the scope is considered.
In the subtree-include form if the request DN matches at least
one rule, the target is considered while fulfilling the
request; otherwise the target is ignored.
| match | exclude |
+---------+---------+-------------------+
| T | T | not candidate |
| F | T | continue checking |
+---------+---------+-------------------+
| T | F | candidate |
| F | F | not candidate |
+---------+---------+-------------------+
There may be multiple occurrences of the subtree-exclude or
subtree-include directive for each of the targets, but they
are mutually exclusive.
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" directive was introduced in the LDAP backend
to allow suffix massaging 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.
t-f-support {NO|yes|discover}
enable if the remote server supports absolute filters (see RFC
4526 for details). If set to discover, support is detected by
reading the remote server's root DSE. If set before any
target specification, it affects all targets, unless
overridden by any per-target directive.
timeout [<op>=]<val> [...]
This directive allows one to set per-operation timeouts.
Operations can be
<op> ::= bind, add, delete, modrdn, modify, compare, search
The overall duration of the search operation is controlled
either by the timelimit parameter or by server-side enforced
time limits (see timelimit and limits in slapd.conf(5) for
details). This timeout parameter controls how long the target
can be irresponsive before the operation is aborted. Timeout
is meaningless for the remaining operations, unbind and
abandon, which do not imply any response, while it is not yet
implemented in currently supported extended operations. If no
operation is specified, the timeout val affects all supported
operations. If specified before any target definition, it
affects all targets unless overridden by per-target
directives.
Note: if the timeout is exceeded, the operation is cancelled
(according to the cancel directive); the protocol does not
provide any means to rollback operations, so the client will
not be notified about the result of the operation, which may
eventually succeeded or not. In case the timeout is exceeded
during a bind operation, the connection is destroyed,
according to RFC4511.
tls {[try-]start|[try-]propagate}
execute the StartTLS extended operation when the connection is
initialized; only works if the URI directive protocol scheme
is not ldaps://. propagate issues the StartTLS operation only
if the original connection did. The try- prefix instructs the
proxy to continue operations if the StartTLS operation failed;
its use is highly deprecated. If set before any target
specification, it affects all targets, unless overridden by
any per-target directive.
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 amazingly 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 multiple 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
target'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
configurations may result as a combination of all the above
scenarios.
Note on ACLs: at present you may add whatever ACL rule you desire to
the Meta (and LDAP) backends. However, the meaning of an ACL on a
proxy may require some considerations. Two philosophies may be
considered:
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
possible 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 file an ITS if you can find other exceptions:
<http://www.openldap.org/its/>). The rule
access to dn="<dn>" attrs=<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
intervention 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".
A string is rewritten according to a set of rules, called a `rewrite
context'. The rules are based on POSIX (''extended'') regular
expressions (regex) 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.
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 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 one 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 behavior while the latter alter the action that
is taken after substitution.
`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.
`:' 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{16}' returns the value `16' 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}'. 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.
See regex(7) and/or re_format(7).
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;
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 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'.
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
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 password modify extended operation 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)
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 alias 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.
rewriteMap <map type> <map name> [ <map attrs> ]
Allows one 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 `%{$paramName}'.
rewriteMaxPasses <number of passes> [<number of passes per rule>]
Sets the maximum number of total rewriting passes that can be
performed in a single rewrite operation (to avoid loops). A
safe default is set to 100; note that reaching this limit is
still treated as a success; recursive invocation of rules is
simply interrupted. The count applies to the rewriting
operation as a whole, not to any single rule; an optional per-
rule limit can be set. This limit is overridden by setting
specific per-rule limits with the `M{n}' flag.
# set to `off' to disable rewriting
rewriteEngine on
# the rules the "suffixmassage" directive implies
rewriteEngine on
# all dataflow from client to server referring to DNs
rewriteContext default
rewriteRule "(.*)<virtualnamingcontext>$" "%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 ".*" "" "#"
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 ...)
The meta backend does not honor all ACL semantics as described in
slapd.access(5). In general, access checking is delegated to the
remote server(s). Only read (=r) access to the entry pseudo-
attribute and to the other attribute values of the entries returned
by the search operation is honored, which is performed by the
frontend.
The proxy cache overlay allows caching of LDAP search requests
(queries) in a local database. See slapo-pcache(5) for details.
The following statements have been deprecated and should no longer be
used.
pseudorootdn <substitute DN in case of rootdn bind>
Use idassert-bind instead.
pseudorootpw <substitute password in case of rootdn bind>
Use idassert-bind instead.
ETCDIR/slapd.conf
default slapd configuration file
slapd.conf(5), slapd-ldap(5), slapo-pcache(5), slapd(8), regex(7),
re_format(7).
Pierangelo Masarati, based on back-ldap by Howard Chu
This page is part of the OpenLDAP (an open source implementation of
the Lightweight Directory Access Protocol) project. Information
about the project can be found at ⟨http://www.openldap.org/⟩. If you
have a bug report for this manual page, see
⟨http://www.openldap.org/its/⟩. This page was obtained from the
project's upstream Git repository
⟨git://git.openldap.org/openldap.git⟩ on 2017-07-05. If you discover
any rendering problems in this HTML version of the page, or you
believe there is a better or more up-to-date source for the page, or
you have corrections or improvements to the information in this
COLOPHON (which is not part of the original manual page), send a mail
to man-pages@man7.org
OpenLDAP LDVERSION RELEASEDATE SLAPD-META(5)
Pages that refer to this page: slapd-asyncmeta(5), slapd.backends(5), slapd-ldap(5), slapd-meta(5), slapd.overlays(5), slapo-pcache(5), slapo-rwm(5), slapo-translucent(5)