SLAPD.ACCESS(5) File Formats Manual SLAPD.ACCESS(5)
NAME
slapd.access - access configuration for slapd, the stand-alone LDAP dae-
mon
SYNOPSIS
/etc/ldap/slapd.conf
DESCRIPTION
The slapd.conf(5) file contains configuration information for the
slapd(8) daemon. This configuration file is also used by the SLAPD tools
slapacl(8), slapadd(8), slapauth(8), slapcat(8), slapdn(8), slapin-
dex(8), slapmodify(8), and slaptest(8).
The slapd.conf file consists of a series of global configuration options
that apply to slapd as a whole (including all backends), followed by
zero or more database backend definitions that contain information spe-
cific to a backend instance.
The general format of slapd.conf is as follows:
# comment - these options apply to every database
<global configuration options>
# first database definition & configuration options
database <backend 1 type>
<configuration options specific to backend 1>
# subsequent database definitions & configuration options
...
Both the global configuration and each backend-specific section can con-
tain access information. Backend-specific access control directives are
used for those entries that belong to the backend, according to their
naming context. In case no access control directives are defined for a
backend or those which are defined are not applicable, the directives
from the global configuration section are then used.
If no access controls are present, the default policy allows anyone and
everyone to read anything but restricts updates to rootdn. (e.g., "ac-
cess to * by * read").
When dealing with an access list, because the global access list is ef-
fectively appended to each per-database list, if the resulting list is
non-empty then the access list will end with an implicit access to * by
* none directive. If there are no access directives applicable to a
backend, then a default read is used.
Be warned: the rootdn can always read and write EVERYTHING!
For entries not held in any backend (such as a root DSE), the global di-
rectives are used.
Arguments that should be replaced by actual text are shown in brackets
<>.
THE ACCESS DIRECTIVE
The structure of the access control directives is
access to <what> [ by <who> [ <access> ] [ <control> ] ]+
Grant access (specified by <access>) to a set of entries and/or
attributes (specified by <what>) by one or more requestors (spec-
ified by <who>).
Lists of access directives are evaluated in the order they appear in
slapd.conf. When a <what> clause matches the datum whose access is be-
ing evaluated, its <who> clause list is checked. When a <who> clause
matches the accessor's properties, its <access> and <control> clauses
are evaluated.
Access control checking stops at the first match of the <what> and <who>
clause, unless otherwise dictated by the <control> clause. Each <who>
clause list is implicitly terminated by a
by * none stop
<control> clause. This implicit <control> stops access directive evalu-
ation with no more access privileges granted to anyone else. To stop
access directive evaluation only when both <who> and <what> match, add
an explicit
by * break
to the end of the <who> clause list.
Each <what> clause list is implicitly terminated by a
access to *
by * none
clause that results in granting no access privileges to an otherwise un-
specified datum.
THE <WHAT> FIELD
The field <what> specifies the entity the access control directive ap-
plies to. It can have the forms
dn[.<dnstyle>]=<dnpattern>
filter=<ldapfilter>
attrs=<attrlist>[ val[/matchingRule][.<attrstyle>]=<attrval>]
with
<dnstyle>={{exact|base(object)}|regex
|one(level)|sub(tree)|children}
<attrlist>={<attr>|[{!|@}]<objectClass>}[,<attrlist>]
<attrstyle>={{exact|base(object)}|regex
|one(level)|sub(tree)|children}
The statement dn=<dnpattern> selects the entries based on their naming
context. The <dnpattern> is a string representation of the entry's DN.
The wildcard * stands for all the entries, and it is implied if no dn
form is given.
The <dnstyle> is optional; however, it is recommended to specify it to
avoid ambiguities. Base (synonym of baseObject), the default, or exact
(an alias of base) indicates the entry whose DN is equal to the <dnpat-
tern>; one (synonym of onelevel) indicates all the entries immediately
below the <dnpattern>, sub (synonym of subtree) indicates all entries in
the subtree at the <dnpattern>, children indicates all the entries below
(subordinate to) the <dnpattern>.
If the <dnstyle> qualifier is regex, then <dnpattern> is a POSIX (''ex-
tended'') regular expression pattern, as detailed in regex(7) and/or
re_format(7), matching a normalized string representation of the entry's
DN. The regex form of the pattern does not (yet) support UTF-8.
The statement filter=<ldapfilter> selects the entries based on a valid
LDAP filter as described in RFC 4515. A filter of (objectClass=*) is
implied if no filter form is given.
The statement attrs=<attrlist> selects the attributes the access control
rule applies to. It is a comma-separated list of attribute types, plus
the special names entry, indicating access to the entry itself, and
children, indicating access to the entry's children. ObjectClass names
may also be specified in this list, which will affect all the attributes
that are required and/or allowed by that objectClass. Actually, names
in <attrlist> that are prefixed by @ are directly treated as objectClass
names. A name prefixed by ! is also treated as an objectClass, but in
this case the access rule affects the attributes that are not required
nor allowed by that objectClass. If no attrs form is given, attrs=@ex-
tensibleObject is implied, i.e. all attributes are addressed.
Using the form attrs=<attr> val[/matchingRule][.<attrstyle>]=<attrval>
specifies access to a particular value of a single attribute. In this
case, only a single attribute type may be given. The <attrstyle> exact
(the default) uses the attribute's equality matching rule to compare the
value, unless a different (and compatible) matching rule is specified.
If the <attrstyle> is regex, the provided value is used as a POSIX
(''extended'') regular expression pattern. If the attribute has DN syn-
tax, the <attrstyle> can be any of base, onelevel, subtree or children,
resulting in base, onelevel, subtree or children match, respectively.
The dn, filter, and attrs statements are additive; they can be used in
sequence to select entities the access rule applies to based on naming
context, value and attribute type simultaneously. Submatches resulting
from regex matching can be dereferenced in the <who> field using the
syntax ${v<n>}, where <n> is the submatch number. The default syntax,
$<n>, is actually an alias for ${d<n>}, that corresponds to dereferenc-
ing submatches from the dnpattern portion of the <what> field.
THE <WHO> FIELD
The field <who> indicates whom the access rules apply to. Multiple
<who> statements can appear in an access control statement, indicating
the different access privileges to the same resource that apply to dif-
ferent accessee. It can have the forms
*
anonymous
users
self[.<selfstyle>]
dn[.<dnstyle>[,<modifier>]]=<DN>
dnattr=<attrname>
realanonymous
realusers
realself[.<selfstyle>]
realdn[.<dnstyle>[,<modifier>]]=<DN>
realdnattr=<attrname>
group[/<objectclass>[/<attrname>]]
[.<groupstyle>]=<group>
peername[.<peernamestyle>]=<peername>
sockname[.<style>]=<sockname>
domain[.<domainstyle>[,<modifier>]]=<domain>
sockurl[.<style>]=<sockurl>
set[.<setstyle>]=<pattern>
ssf=<n>
transport_ssf=<n>
tls_ssf=<n>
sasl_ssf=<n>
dynacl/<name>[/<options>][.<dynstyle>][=<pattern>]
with
<style>={exact|regex|expand}
<selfstyle>={level{<n>}}
<dnstyle>={{exact|base(object)}|regex
|one(level)|sub(tree)|children|level{<n>}}
<groupstyle>={exact|expand}
<peernamestyle>={<style>|ip|ipv6|path}
<domainstyle>={exact|regex|sub(tree)}
<setstyle>={exact|expand}
<modifier>={expand}
<name>=aci <pattern>=<attrname>]
They may be specified in combination.
The wildcard * refers to everybody.
The keywords prefixed by real act as their counterparts without prefix;
the checking respectively occurs with the authentication DN and the au-
thorization DN.
The keyword anonymous means access is granted to unauthenticated
clients; it is mostly used to limit access to authentication resources
(e.g. the userPassword attribute) to unauthenticated clients for authen-
tication purposes.
The keyword users means access is granted to authenticated clients.
The keyword self means access to an entry is allowed to the entry itself
(e.g. the entry being accessed and the requesting entry must be the
same). It allows the level{<n>} style, where <n> indicates what ances-
tor of the DN is to be used in matches. A positive value indicates that
the <n>-th ancestor of the user's DN is to be considered; a negative
value indicates that the <n>-th ancestor of the target is to be consid-
ered. For example, a "by self.level{1} ..." clause would match when the
object "dc=example,dc=com" is accessed by "cn=User,dc=example,dc=com".
A "by self.level{-1} ..." clause would match when the same user accesses
the object "ou=Address Book,cn=User,dc=example,dc=com".
The statement dn=<DN> means that access is granted to the matching DN.
The optional style qualifier dnstyle allows the same choices of the dn
form of the <what> field. In addition, the regex style can exploit sub-
string substitution of submatches in the <what> dn.regex clause by using
the form $<digit>, with digit ranging from 0 to 9 (where 0 matches the
entire string), or the form ${<digit>+}, for submatches higher than 9.
Substring substitution from attribute value can be done in using the
form ${v<digit>+}. Since the dollar character is used to indicate a
substring replacement, the dollar character that is used to indicate
match up to the end of the string must be escaped by a second dollar
character, e.g.
access to dn.regex="^(.+,)?uid=([^,]+),dc=[^,]+,dc=com$"
by dn.regex="^uid=$2,dc=[^,]+,dc=com$$" write
The style qualifier allows an optional modifier. At present, the only
type allowed is expand, which causes substring substitution of sub-
matches to take place even if dnstyle is not regex. Note that the regex
dnstyle in the above example may be of use only if the <by> clause needs
to be a regex; otherwise, if the value of the second (from the right)
dc= portion of the DN in the above example were fixed, the form
access to dn.regex="^(.+,)?uid=([^,]+),dc=example,dc=com$"
by dn.exact,expand="uid=$2,dc=example,dc=com" write
could be used; if it had to match the value in the <what> clause, the
form
access to dn.regex="^(.+,)?uid=([^,]+),dc=([^,]+),dc=com$"
by dn.exact,expand="uid=$2,dc=$3,dc=com" write
could be used.
Forms of the <what> clause other than regex may provide submatches as
well. The base(object), the sub(tree), the one(level), and the children
forms provide $0 as the match of the entire string. The sub(tree), the
one(level), and the children forms also provide $1 as the match of the
rightmost part of the DN as defined in the <what> clause. This may be
useful, for instance, to provide access to all the ancestors of a user
by defining
access to dn.subtree="dc=com"
by dn.subtree,expand="$1" read
which means that only access to entries that appear in the DN of the
<by> clause is allowed.
The level{<n>} form is an extension and a generalization of the onelevel
form, which matches all DNs whose <n>-th ancestor is the pattern. So,
level{1} is equivalent to onelevel, and level{0} is equivalent to base.
It is perfectly useless to give any access privileges to a DN that ex-
actly matches the rootdn of the database the ACLs apply to, because it
implicitly possesses write privileges for the entire tree of that data-
base. Actually, access control is bypassed for the rootdn, to solve the
intrinsic chicken-and-egg problem.
The statement dnattr=<attrname> means that access is granted to requests
whose DN is listed in the entry being accessed under the <attrname> at-
tribute.
The statement group=<group> means that access is granted to requests
whose DN is listed in the group entry whose DN is given by <group>. The
optional parameters <objectclass> and <attrname> define the objectClass
and the member attributeType of the group entry. The defaults are
groupOfNames and member, respectively. The optional style qualifier
<style> can be expand, which means that <group> will be expanded as a
replacement string (but not as a regular expression) according to
regex(7) and/or re_format(7), and exact, which means that exact match
will be used. If the style of the DN portion of the <what> clause is
regex, the submatches are made available according to regex(7) and/or
re_format(7); other styles provide limited submatches as discussed above
about the DN form of the <by> clause.
For static groups, the specified attributeType must have Distinguished-
Name or NameAndOptionalUID syntax. For dynamic groups the attributeType
must be a subtype of the labeledURI attributeType. Only LDAP URIs of the
form ldap:///<base>??<scope>?<filter> will be evaluated in a dynamic
group, by searching the local server only.
The statements peername=<peername>, sockname=<sockname>, domain=<do-
main>, and sockurl=<sockurl> mean that the contacting host IP (in the
form IP=<ip>:<port> for IPv4, or IP=[<ipv6>]:<port> for IPv6) or the
contacting host named pipe file name (in the form PATH=<path> if con-
necting through a named pipe) for peername, the named pipe file name for
sockname, the contacting host name for domain, and the contacting URL
for sockurl are compared against pattern to determine access. The same
style rules for pattern match described for the group case apply, plus
the regex style, which implies submatch expand and regex match of the
corresponding connection parameters. The exact style of the <peername>
clause (the default) implies a case-exact match on the client's IP, in-
cluding the IP= prefix and the trailing :<port>, or the client's path,
including the PATH= prefix if connecting through a named pipe. The spe-
cial ip style interprets the pattern as <peername>=<ip>[%<mask>][{<n>}],
where <ip> and <mask> are dotted digit representations of the IP and the
mask, while <n>, delimited by curly brackets, is an optional port. The
same applies to IPv6 addresses when the special ipv6 style is used.
When checking access privileges, the IP portion of the peername is ex-
tracted, eliminating the IP= prefix and the :<port> part, and it is com-
pared against the <ip> portion of the pattern after masking with <mask>:
((peername & <mask>) == <ip>). As an example, peername.ip=127.0.0.1 and
peername.ipv6=::1 allow connections only from localhost, peer-
name.ip=192.168.1.0%255.255.255.0 allows connections from any IP in the
192.168.1 class C domain, and peer-
name.ip=192.168.1.16%255.255.255.240{9009} allows connections from any
IP in the 192.168.1.[16-31] range of the same domain, only if port 9009
is used. The special path style eliminates the PATH= prefix from the
peername when connecting through a named pipe, and performs an exact
match on the given pattern. The <domain> clause also allows the subtree
style, which succeeds when a fully qualified name exactly matches the
domain pattern, or its trailing part, after a dot, exactly matches the
domain pattern. The expand style is allowed, implying an exact match
with submatch expansion; the use of expand as a style modifier is con-
sidered more appropriate. As an example, domain.subtree=example.com
will match www.example.com, but will not match www.anotherexample.com.
The domain of the contacting host is determined by performing a DNS re-
verse lookup. As this lookup can easily be spoofed, use of the domain
statement is strongly discouraged. By default, reverse lookups are dis-
abled. The optional domainstyle qualifier of the <domain> clause allows
a modifier option; the only value currently supported is expand, which
causes substring substitution of submatches to take place even if the
domainstyle is not regex, much like the analogous usage in <dn> clause.
The statement set=<pattern> is undocumented yet.
The statement dynacl/<name>[/<options>][.<dynstyle>][=<pattern>] means
that access checking is delegated to the admin-defined method indicated
by <name>, which can be registered at run-time by means of the module-
load statement. The fields <options>, <dynstyle> and <pattern> are op-
tional, and are directly passed to the registered parsing routine. Dy-
nacl is experimental; it must be enabled at compile time.
The statement dynacl/aci[=<attrname>] means that the access control is
determined by the values in the attrname of the entry itself. The op-
tional <attrname> indicates what attributeType holds the ACI information
in the entry. By default, the OpenLDAPaci operational attribute is
used. ACIs are experimental; they must be enabled at compile time.
The statements ssf=<n>, transport_ssf=<n>, tls_ssf=<n>, and sasl_ssf=<n>
set the minimum required Security Strength Factor (ssf) needed to grant
access. The value should be positive integer.
THE <ACCESS> FIELD
The optional field <access> ::= [[real]self]{<level>|<priv>} determines
the access level or the specific access privileges the who field will
have. Its component are defined as
<level> ::= none|disclose|auth|compare|search|read|{write|add|delete}|manage
<priv> ::= {=|+|-}{0|d|x|c|s|r|{w|a|z}|m}+
The modifier self allows special operations like having a certain access
level or privilege only in case the operation involves the name of the
user that's requesting the access. It implies the user that requests
access is authorized. The modifier realself refers to the authenticated
DN as opposed to the authorized DN of the self modifier. An example is
the selfwrite access to the member attribute of a group, which allows
one to add/delete its own DN from the member list of a group, while be-
ing not allowed to affect other members.
The level access model relies on an incremental interpretation of the
access privileges. The possible levels are none, disclose, auth, com-
pare, search, read, write, and manage. Each access level implies all
the preceding ones, thus manage grants all access including administra-
tive access. This access allows some modifications which would otherwise
be prohibited by the LDAP data model or the directory schema, e.g.
changing the structural objectclass of an entry, or modifying an opera-
tional attribute that is defined as not user modifiable. The write ac-
cess is actually the combination of add and delete, which respectively
restrict the write privilege to add or delete the specified <what>.
The none access level disallows all access including disclosure on er-
ror.
The disclose access level allows disclosure of information on error.
The auth access level means that one is allowed access to an attribute
to perform authentication/authorization operations (e.g. bind) with no
other access. This is useful to grant unauthenticated clients the least
possible access level to critical resources, like passwords.
The priv access model relies on the explicit setting of access privi-
leges for each clause. The = sign resets previously defined accesses;
as a consequence, the final access privileges will be only those defined
by the clause. The + and - signs add/remove access privileges to the
existing ones. The privileges are m for manage, w for write, a for add,
z for delete, r for read, s for search, c for compare, x for authentica-
tion, and d for disclose. More than one of the above privileges can be
added in one statement. 0 indicates no privileges and is used only by
itself (e.g., +0). Note that +az is equivalent to +w.
If no access is given, it defaults to +0.
THE <CONTROL> FIELD
The optional field <control> controls the flow of access rule applica-
tion. It can have the forms
stop
continue
break
where stop, the default, means access checking stops in case of match.
The other two forms are used to keep on processing access clauses. In
detail, the continue form allows for other <who> clauses in the same
<access> clause to be considered, so that they may result in incremen-
tally altering the privileges, while the break form allows for other
<access> clauses that match the same target to be processed. Consider
the (silly) example
access to dn.subtree="dc=example,dc=com" attrs=cn
by * =cs break
access to dn.subtree="ou=People,dc=example,dc=com"
by * +r
which allows search and compare privileges to everybody under the
"dc=example,dc=com" tree, with the second rule allowing also read in the
"ou=People" subtree, or the (even more silly) example
access to dn.subtree="dc=example,dc=com" attrs=cn
by * =cs continue
by users +r
which grants everybody search and compare privileges, and adds read
privileges to authenticated clients.
One useful application is to easily grant write privileges to an updat-
edn that is different from the rootdn. In this case, since the updatedn
needs write access to (almost) all data, one can use
access to *
by dn.exact="cn=The Update DN,dc=example,dc=com" write
by * break
as the first access rule. As a consequence, unless the operation is
performed with the updatedn identity, control is passed straight to the
subsequent rules.
OPERATION REQUIREMENTS
Operations require different privileges on different portions of en-
tries. The following summary applies to primary MDB database backend.
Requirements for other backends may (and often do) differ.
The add operation requires add (=a) privileges on the pseudo-attribute
entry of the entry being added, and add (=a) privileges on the pseudo-
attribute children of the entry's parent. When adding the suffix entry
of a database, add access to children of the empty DN ("") is required.
Also if Add content ACL checking has been configured on the database
(see the slapd.conf(5) or slapd-config(5) manual page), add (=a) will be
required on all of the attributes being added.
The bind operation, when credentials are stored in the directory, re-
quires auth (=x) privileges on the attribute the credentials are stored
in (usually userPassword).
The compare operation requires compare (=c) privileges on the attribute
that is being compared.
The delete operation requires delete (=z) privileges on the pseudo-at-
tribute entry of the entry being deleted, and delete (=d) privileges on
the children pseudo-attribute of the entry's parent.
The modify operation requires write (=w) privileges on the attributes
being modified. In detail, add (=a) is required to add new values,
delete (=z) is required to delete existing values, and both delete and
add (=az), or write (=w), are required to replace existing values.
The modrdn operation requires write (=w) privileges on the pseudo-at-
tribute entry of the entry whose relative DN is being modified, delete
(=z) privileges on the pseudo-attribute children of the old entry's par-
ents, add (=a) privileges on the pseudo-attribute children of the new
entry's parents, and add (=a) privileges on the attributes that are
present in the new relative DN. Delete (=z) privileges are also re-
quired on the attributes that are present in the old relative DN if
deleteoldrdn is set to 1.
The search operation, requires search (=s) privileges on the entry
pseudo-attribute of the searchBase (NOTE: this was introduced with
OpenLDAP 2.4). Then, for each entry, it requires search (=s) privileges
on the attributes that are defined in the filter. The resulting entries
are finally tested for read (=r) privileges on the pseudo-attribute en-
try (for read access to the entry itself) and for read (=r) access on
each value of each attribute that is requested. Also, for each referral
object used in generating continuation references, the operation re-
quires read (=r) access on the pseudo-attribute entry (for read access
to the referral object itself), as well as read (=r) access to the at-
tribute holding the referral information (generally the ref attribute).
Some internal operations and some controls require specific access priv-
ileges.
The SASL authzID mapping and the LDAP proxyAuthz control require auth
(=x) privileges on all the attributes that are present in the search
filter of the URI regexp maps (the right-hand side of the authz-regexp
directives). Auth (=x) privileges are also required on the authzTo at-
tribute of the authorizing identity and/or on the authzFrom attribute of
the authorized identity. In both cases, it is the authorizing identity
that requires the privileges (i.e. the identity that has authenticated
and is now trying to do some operation using another entity's permis-
sions).
In general, when an internal lookup is performed for authentication or
authorization purposes, search-specific privileges (see the access re-
quirements for the search operation illustrated above) are relaxed to
auth.
Access control to search entries is checked by the frontend, so it is
fully honored by all backends; for all other operations and for the dis-
covery phase of the search operation, full ACL semantics is only sup-
ported by the primary backends, i.e. slapd-mdb(5).
Some other backend, like slapd-sql(5), may fully support them; others
may only support a portion of the described semantics, or even differ in
some aspects. The relevant details are described in the backend-spe-
cific man pages.
CAVEATS
It is strongly recommended to explicitly use the most appropriate
<dnstyle> in <what> and <who> clauses, to avoid possible incorrect spec-
ifications of the access rules as well as for performance (avoid unnec-
essary regex matching when an exact match suffices) reasons.
An administrator might create a rule of the form:
access to dn.regex="dc=example,dc=com"
by ...
expecting it to match all entries in the subtree "dc=example,dc=com".
However, this rule actually matches any DN which contains anywhere the
substring "dc=example,dc=com". That is, the rule matches both
"uid=joe,dc=example,dc=com" and "dc=example,dc=com,uid=joe".
To match the desired subtree, the rule would be more precisely written:
access to dn.regex="^(.+,)?dc=example,dc=com$"
by ...
For performance reasons, it would be better to use the subtree style.
access to dn.subtree="dc=example,dc=com"
by ...
When writing submatch rules, it may be convenient to avoid unnecessary
regex <dnstyle> use; for instance, to allow access to the subtree of the
user that matches the <what> clause, one could use
access to dn.regex="^(.+,)?uid=([^,]+),dc=example,dc=com$"
by dn.regex="^uid=$2,dc=example,dc=com$$" write
by ...
However, since all that is required in the <by> clause is substring ex-
pansion, a more efficient solution is
access to dn.regex="^(.+,)?uid=([^,]+),dc=example,dc=com$"
by dn.exact,expand="uid=$2,dc=example,dc=com" write
by ...
In fact, while a <dnstyle> of regex implies substring expansion, exact,
as well as all the other DN specific <dnstyle> values, does not, so it
must be explicitly requested.
FILES
/etc/ldap/slapd.conf
default slapd configuration file
SEE ALSO
slapd(8), slapd-*(5), slapacl(8), regex(7), re_format(7)
"OpenLDAP Administrator's Guide" (http://www.OpenLDAP.org/doc/admin/)
ACKNOWLEDGEMENTS
OpenLDAP Software is developed and maintained by The OpenLDAP Project
<http://www.openldap.org/>. OpenLDAP Software is derived from the Uni-
versity of Michigan LDAP 3.3 Release.
OpenLDAP 2.6.10+dfsg-1 2025/05/22 SLAPD.ACCESS(5)
Generated by dwww version 1.16 on Tue Dec 16 05:00:50 CET 2025.