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slapd.access — access configuration for slapd, the stand-alone LDAP daemon
ETCDIR/slapd.conf
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), slapindex(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
specific 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 contain 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., "access to * by * read").
When dealing with an access list, because the global access list is effectively 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 directives are used.
Arguments that should be replaced by actual text are shown in brackets <>.
The structure of the access control directives is
Grant access (specified by <access>) to a
set of entries and/or attributes (specified by
<what>)
by one or more requestors (specified 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 being
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
clause that results in stopping the access control
with no access privileges granted. Each <what> clause
list is implicitly terminated by a
access to *
by * none
clause that results in granting no access privileges to an otherwise unspecified datum.
The field <what> specifies the
entity the access control directive applies 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 <dnpattern>; 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
(''extended'') 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=@extensibleObject 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 syntax, 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 dereferencing submatches from the dnpattern portion of the
<what>
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 different 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
authorization
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 authentication 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 ancestor 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 considered. 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 substring 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 submatches 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 exactly matches the rootdn of the database the
ACLs apply to, because it implicitly possesses write
privileges for the entire tree of that database. 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>
attribute.
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
DistinguishedName
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=<domain>, 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
connecting 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, including the IP= prefix and the trailing
:<port>, or
the client's path,
including the PATH=
prefix if connecting through a named pipe. The special
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 extracted,
eliminating the IP=
prefix and the :<port> part, and it is
compared 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, peername.ip=192.168.1.0%255.255.255.0
allows connections from any IP in the 192.168.1 class C
domain, and peername.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
considered 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 reverse lookup. As this
lookup can easily be spoofed, use of the domain statement is strongly
discouraged. By default, reverse lookups are disabled. 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 moduleload statement. The
fields <options>, <dynstyle> and
<pattern> are
optional, and are directly passed to the registered parsing
routine. Dynacl 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 optional <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 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 being 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, compare, search, read, write, and manage. Each access level
implies all the preceding ones, thus manage grants all access
including administrative access. The write access 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 error.
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 privileges 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
authentication, 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 optional field <control> controls the
flow of access rule application. 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 incrementally 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 updatedn 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.
Operations require different privileges on different portions of entries. The following summary applies to primary database backends such as the BDB and HDB backends. 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,
requires 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-attribute
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-attribute
entry of the entry
whose relative DN is being modified, delete (=z) privileges on the
pseudo-attribute children of the old entry's
parents, 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 required 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 entry (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 requires
read (=r) access on
the pseudo-attribute entry (for read access to the
referral object itself), as well as read (=r) access to the attribute
holding the referral information (generally the ref attribute).
Some internal operations and some controls require specific
access privileges. The authzID mapping and the
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 attribute of the
authorizing identity and/or on the authzFrom attribute of the
authorized identity. In general, when an internal lookup is
performed for authentication or authorization purposes,
search-specific privileges (see the access requirements 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 discovery phase of the search operation, full ACL semantics is only supported by the primary backends, i.e. back-bdb(5), and back-hdb(5).
Some other backend, like back-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-specific man pages.
It is strongly recommended to explicitly use the most
appropriate <dnstyle> in <what> and <who> clauses, to avoid
possible incorrect specifications of the access rules as well
as for performance (avoid unnecessary 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 expansion, 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.
slapd(8), slapd-*(5), slapacl(8), regex(7), re_format(7)
"OpenLDAP Administrator's Guide" (http://www.OpenLDAP.org/doc/admin/)
OpenLDAP Software is developed and maintained by The OpenLDAP Project <http://www.openldap.org/>. OpenLDAP Software is derived from University of Michigan LDAP 3.3 Release.