SLAPD.ACCESS(5)

NAME
slapd.access - access configuration for slapd, the stand-alone LDAP daemon

SYNOPSIS
/etc/openldap/slapd.conf

DESCRIPTION
The slapd.conf(5) file contains configuration information for the slapd(8) daemon. This configuration file is also used by the slurpd(8) replication daemon and by the SLAPD tools slapadd(8), slapcat(8), and slapindex(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.

For entries not held in any backend (such as a root DSE), the directives of the first backend (and any 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>).

The field <what> specifies the entity the access control directive applies to. It can have the forms

	*
	[dn[.<dnstyle>]=<pattern>]
	[filter=<ldapfilter>]
	[attrs=<attrlist>]

The wildcard * stands for all the entries.

The statement dn=<pattern> selects the entries based on their naming context. The optional style qualifier <dnstyle> can be regex (the default) implies that pattern is a regular expression, as detailed in regex(7), matching a normalized string representation of the entry's DN. The regex form of the pattern does not support UTF-8 yet.

For all other qualifiers, the pattern is a string representation of the entry's DN. base or exact (an alias of base) indicates the entry whose DN is equal to the pattern. one to indicate all the entries immediately below the pattern, subtree to indicate all entries in the subtree at the pattern, children to indicate all entries below (subordinate) to the pattern. Note that dn=".*" is equivalent to *.

The statement filter=<ldapfilter> selects the entries based on a valid LDAP filter as described in RFC 2254.

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.

The last three 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.

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
	dn[.<dnstyle>[,<modifier>]]=<pattern>
	dnattr=<attrname>
	group[/<objectclass>[/<attrname>]]
		[.<style>]=<pattern>
	peername[.<style>]=<pattern>
	sockname[.<style>]=<pattern>
	domain[.<domainstyle>[,<modifier>]]=<pattern>
	sockurl[.<style>]=<pattern>
	set[.<style>]=<pattern>
	ssf=<n>
	transport_ssf=<n>
	tls_ssf=<n>
	sasl_ssf=<n>
	aci=<attrname>

They may be specified in combination.

The wildcard * refers to everybody.

The keyword anonymous means access is granted to unauthenticated users; it is moslty used to limit access to authentication resources (e.g. the userPassword attribute) to unauthenticated users for authentication purposes.

The keyword users means access is granted to authenticated users.

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).

The statement dn=<pattern> 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 form of pattern can exploit substring substitution of submatches in the <what> dn.regex clause by using the form $<digit>, with digit ranging from 1 to 9.

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=<pattern> means that access is granted to requests whose DN is listed in the group entry whose DN is given by pattern. The optional parameters objectclass and attrname define the objectClass and the member attributeType of the group entry. The optional style qualifier style can be regex, which means that pattern will be expanded accorging to regex (7), and base or exact (an alias of base), which means that exact match will be used.

The statements peername=<pattern>, sockname=<pattern>, domain=<pattern>, and sockurl=<pattern> mean that the contacting host IP 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. 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 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 statement set=<pattern> is undocumented yet.

The statement aci=<attrname> means that the access control is determined by the values in the attrname of the entry itself. 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 required Security Strength Factor (ssf) required to grant access.

The field <access> ::= [self]{<level>|<priv>} determines the access level or the specific access privileges the who field will have. Its component are defined as

	<level> ::= none|auth|compare|search|read|write
	<priv> ::= {=|+|-}{w|r|s|c|x}+

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 bound. 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, without affecting other members.

The level access model relies on an incremental interpretation of the access privileges. The possible levels are none, auth, compare, search, read, and write. Each access level implies all the preceding ones, thus write access will imply all accesses. While none is trivial, auth access 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 users 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 w for write, r for read, s for search, c for compare, and x for authentication. More than one privilege can be added in one statement.

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.

CAVEATS
It is strongly recommended to explicitly use the most appropriate DN style, to avoid possible incorrect specifications of the access rules as well as for performance (avoid unrequired regex matching when an exact match suffices) reasons.

An adminisistrator might create a rule of the form:

	access to dn="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 ...

FILES

/etc/openldap/slapd.conf
    default slapd configuration file

SEE ALSO
slapd(8),

"OpenLDAP Administrator's Guide" (http://www.OpenLDAP.org/doc/admin/)

ACKNOWLEDGEMENTS
OpenLDAP is developed and maintained by The OpenLDAP Project (http://www.openldap.org/). OpenLDAP is derived from University of Michigan LDAP 3.3 Release.