SLAPD.ACCESS(5) File Formats Manual SLAPD.ACCESS(5)
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), 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 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
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 (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
<control> clause. This implicit <control> stops access directive
evaluation 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 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. 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 operational attribute
that is defined as not user modifiable. 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 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,
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 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 attribute 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 permissions).
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. 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-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.
ETCDIR/slapd.conf
default slapd configuration file
slapd(8), slapd-*(5), slapacl(8), regex(7), re_format(7)
"OpenLDAP Administrator's Guide"
(http://www.OpenLDAP.org/doc/admin/)
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