openldap/doc/man/man5/slapd.access.5

.TH SLAPD.ACCESS 5 "RELEASEDATE" "OpenLDAP LDVERSION"
.\" Copyright 1998-2004 The OpenLDAP Foundation All Rights Reserved.
.\" Copying restrictions apply.  See COPYRIGHT/LICENSE.
.SH NAME
slapd.access \- access configuration for slapd, the stand-alone LDAP daemon
.SH SYNOPSIS
ETCDIR/slapd.conf
.SH DESCRIPTION
The 
.BR slapd.conf (5)
file contains configuration information for the
.BR slapd (8)
daemon. This configuration file is also used by the
.BR slurpd (8)
replication daemon and by the SLAPD tools
.BR slapadd (8),
.BR slapcat (8),
and
.BR slapindex (8).
.LP
The
.B slapd.conf
file consists of a series of global configuration options that apply to
.B slapd
as a whole (including all backends), followed by zero or more database
backend definitions that contain information specific to a backend
instance.
.LP
The general format of
.B slapd.conf
is as follows:
.LP
.nf
    # 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
    ...
.fi
.LP
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.
.LP
For entries not held in any backend (such as a root DSE), the
directives of the first backend (and any global directives) are
used.
.LP
Arguments that should be replaced by actual text are shown in
brackets <>.
.SH THE ACCESS DIRECTIVE
The structure of the access control directives is
.TP
.B access to <what> "[ by <who> <access> [ <control> ] ]+"
Grant access (specified by 
.BR <access> ) 
to a set of entries and/or attributes (specified by 
.BR <what> ) 
by one or more requestors (specified by 
.BR <who> ).
.SH THE <WHAT> FIELD
The field
.BR <what>
specifies the entity the access control directive applies to.
It can have the forms
.LP
.nf
	*
	[dn[.<dnstyle>]=<DN>] 
	[filter=<ldapfilter>]
	[attrs=<attrlist>[ val[.<style>]=<attrval>]]
.fi
.LP
The wildcard
.B *
stands for all the entries.
.LP
The statement
.B dn=<DN>
selects the entries based on their naming context.
The pattern is a string representation of the entry's DN.
.BR base ,
the default,
or
.B exact 
(an alias of 
.BR base )
indicates the entry whose DN is equal to the pattern;
.B one
(synonym of
.BR onelevel )
indicates all the entries immediately below the
.BR pattern ,
.B sub
(synonym of
.BR subtree )
indicates all entries in the subtree at the pattern,
.B children
indicates all the entries below (subordinate to) the pattern.
.LP
If the
.B <dnstyle>
qualifier is
.BR regex ,
then the value is a regular expression pattern,
as detailed in
.BR regex (7),
matching a normalized string representation of the entry's DN.
The regex form of the pattern does not (yet) support UTF-8.
.LP
The statement
.B filter=<ldapfilter>
selects the entries based on a valid LDAP filter as described in RFC 2254.
.LP
The statement
.B attrs=<attrlist>
selects the attributes the access control rule applies to.
It is a comma-separated list of attribute types, plus the special names
.BR entry ,
indicating access to the entry itself, and
.BR 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 
.B <attrlist>
that are prefixed by
.B @
are directly treated as objectClass names.  A name prefixed by
.B !
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.
.LP
Using the form
.B attrs=<attr> val[.<style>]=<value>
specifies access to a particular value of a single attribute.
In this case, only a single attribute type may be given. A value
.B <style>
of
.B exact
(the default) uses the attribute's equality matching rule to compare the
value. If the value
.B <style>
is
.BR regex ,
the provided value is used as a regular expression pattern.
If the attribute has DN syntax, the value
.B <style>
can be any of
.BR base ,
.BR onelevel ,
.B subtree
or
.BR children ,
resulting in base, onelevel, subtree or children match, respectively.
.LP
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.
.SH THE <WHO> FIELD
The field
.B <who>
indicates whom the access rules apply to.
Multiple 
.B <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
.LP
.nf
	*
	anonymous
	users
	self

	dn[.<dnstyle>[,<modifier>]]=<DN>
	dnattr=<attrname>
	group[/<objectclass>[/<attrname>]]
		[.<groupstyle>]=<group>
	peername[.<peernamestyle>]=<peername>
	sockname[.<style>]=<sockname>
	domain[.<domainstyle>[,<modifier>]]=<domain>
	sockurl[.<style>]=<sockurl>
	set[.<style>]=<pattern>

	ssf=<n>
	transport_ssf=<n>
	tls_ssf=<n>
	sasl_ssf=<n>

	aci=<attrname>
.fi
.LP
with
.LP
.nf
	<dnstyle>={{exact|base}|regex|sub(tree)|one(level)|children}
	<groupstyle>={exact|expand}
	<style>={exact|regex}
	<peernamestyle>={exact|regex|ip|path}
	<domainstyle>={exact|regex|sub(tree)}
	<modifier>={expand}
.fi
.LP
They may be specified in combination.
.LP
.nf
.fi
.LP
The wildcard
.B *
refers to everybody.
.LP
The keyword
.B anonymous
means access is granted to unauthenticated clients; it is mostly used 
to limit access to authentication resources (e.g. the
.B userPassword
attribute) to unauthenticated clients for authentication purposes.
.LP
The keyword
.B users
means access is granted to authenticated clients.
.LP
The keyword
.B 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).
.LP
The statement
.B dn=<DN>
means that access is granted to the matching DN.
The optional style qualifier
.B dnstyle
allows the same choices of the dn form of the
.B <what>
field.  In addition, the
.B regex
style can exploit substring substitution of submatches in the
.B <what>
dn.regex clause by using the form
.BR $<digit> ,
with 
.B digit
ranging from 1 to 9.
The style qualifier
allows an optional
.BR modifier .
At present, the only type allowed is 
.BR expand ,
which causes substring substitution of submatches to take place
even if 
.B dnstyle
is not 
.BR regex .
It is perfectly useless to give any access privileges to a DN 
that exactly matches the
.B rootdn
of the database the ACLs apply to, because it implicitly
possesses write privileges for the entire tree of that database.
.LP
The statement
.B dnattr=<attrname>
means that access is granted to requests whose DN is listed in the
entry being accessed under the 
.B <attrname>
attribute.
.LP
The statement
.B group=<group>
means that access is granted to requests whose DN is listed
in the group entry whose DN is given by
.BR <group> .
The optional parameters
.B <objectclass>
and
.B <attrname>
define the objectClass and the member attributeType of the group entry.
The optional style qualifier
.B <style>
can be
.BR expand ,
which means that
.B <group>
will be expanded as a replacement string (but not as a regular expression)
according to regex (7), and
.BR exact ,
which means that exact match will be used.
.LP
For static groups, the specified attributeType must have
.B DistinguishedName
or
.B NameAndOptionalUID
syntax. For dynamic groups the attributeType must
be a subtype of the
.B labeledURI
attributeType. Only LDAP URIs of the form
.B ldap:///<base>??<scope>?<filter>
will be evaluated in a dynamic group, by searching the local server only.
.LP
The statements
.BR peername=<peername> ,
.BR sockname=<sockname> ,
.BR domain=<domain> ,
and
.BR sockurl=<sockurl>
mean that the contacting host IP (in the form 
.BR "IP=<ip>:<port>" )
or the contacting host named pipe file name (in the form
.B "PATH=<path>"
if connecting through a named pipe) for
.BR peername ,
the named pipe file name for
.BR sockname ,
the contacting host name for
.BR domain ,
and the contacting URL for
.BR sockurl
are compared against
.B pattern
to determine access.
The same
.B style
rules for pattern match described for the
.B group
case apply. 
The
.B exact
style of the
.BR peername
clause (the default) implies a case-exact match on the client's
.BR IP , 
including the
.B "IP="
prefix and the trailing
.BR ":<port>" , 
or the client's 
.BR path ,
including the
.B "PATH="
prefix if connecting through a named pipe.
The special
.B ip
style interprets the pattern as 
.BR <peername>=<ip>[%<mask>][{<n>}] ,
where
.B <ip>
and 
.B <mask>
are dotted digit representations of the IP and the mask, while
.BR <n> ,
delimited by curly brackets, is an optional port.
When checking access privileges, the IP portion of the
.BR peername 
is extracted, eliminating the
.B "IP="
prefix and the
.B ":<port>"
part, and it is compared against the
.B <ip>
portion of the pattern after masking with
.BR <mask> .
As an example, 
.B peername.ip=127.0.0.1
alows connections only from localhost,
.B peername.ip=192.168.1.0%255.255.255.0 
allows connections from any IP in the 192.168.1 class C domain, and
.B 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 
.B path
style eliminates the 
.B "PATH="
prefix from the 
.B peername
when connecting through a named pipe, and performs an exact match 
on the given pattern.
The
.BR domain 
clause also allows the
.B subtree
style, which succeeds when a fully qualified name exactly matches the
.BR domain
pattern, or its trailing part, after a 
.BR dot ,
exactly matches the 
.BR domain
pattern.
As an example,
.B domain.subtree=example.com
will match www.example.com, but will not match www.anotherexample.com.
The
.B domain
of the contacting host is determined by performing a DNS reverse lookup.
As this lookup can easily be spoofed, use of the
.B domain
statement is strongly discouraged.  By default, reverse lookups are disabled.
The optional
.B domainstyle
qualifier of the
.B domain
clause allows a
.B modifier
option; the only value currently supported is
.BR expand ,
which causes substring substitution of submatches to take place even if
the 
.B domainstyle
is not 
.BR regex ,
much like the analogous usage in 
.B dn
clause.
.LP
The statement
.B set=<pattern>
is undocumented yet.
.LP
The statement
.B aci=<attrname>
means that the access control is determined by the values in the
.B attrname
of the entry itself.
ACIs are experimental; they must be enabled at compile time.
.LP
The statements
.BR ssf=<n> ,
.BR transport_ssf=<n> ,
.BR tls_ssf=<n> ,
and
.BR sasl_ssf=<n>
set the required Security Strength Factor (ssf) required to grant access.
.SH THE <ACCESS> FIELD
The field
.B <access> ::= [self]{<level>|<priv>}
determines the access level or the specific access privileges the
.B who 
field will have.
Its component are defined as
.LP
.nf
	<level> ::= none|auth|compare|search|read|write
	<priv> ::= {=|+|-}{w|r|s|c|x|0}+
.fi
.LP
The modifier
.B 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
.B 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.
.LP
The 
.B level 
access model relies on an incremental interpretation of the access
privileges.
The possible levels are
.BR none ,
.BR auth ,
.BR compare ,
.BR search ,
.BR read ,
and
.BR write .
Each access level implies all the preceding ones, thus 
.B write
access will imply all accesses.
While
.B none
is trivial, 
.B auth
access means that one is allowed access to an attribute to perform
authentication/authorization operations (e.g.
.BR bind )
with no other access.
This is useful to grant unauthenticated clients the least possible 
access level to critical resources, like passwords.
.LP
The
.B priv
access model relies on the explicit setting of access privileges
for each clause.
The
.B =
sign resets previously defined accesses; as a consequence, the final 
access privileges will be only those defined by the clause.
The 
.B +
and
.B -
signs add/remove access privileges to the existing ones.
The privileges are
.B w
for write,
.B r
for read,
.B s 
for search,
.B c 
for compare, and
.B x
for authentication.
More than one of the above privileges can be added in one statement.
.B 0
indicates no privileges and is used only by itself (e.g., +0).
.LP
The optional field
.B <control>
controls the flow of access rule application.
It can have the forms
.LP
.nf
	stop
	continue
	break
.fi
.LP
where
.BR 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
.B continue
form allows for other 
.B <who>
clauses in the same 
.B <access>
clause to be considered, so that they may result in incrementally altering
the privileges, while the
.B break
form allows for other
.B <access>
clauses that match the same target to be processed.
Consider the (silly) example
.LP
.nf
	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
.fi
.LP
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
.LP
.nf
	access to dn.subtree="dc=example,dc=com" attrs=cn
		by * =cs continue
		by users +r
.fi
.LP
which grants everybody search and compare privileges, and adds read
privileges to authenticated clients.
.SH OPERATION REQUIREMENTS
Operations require different privileges on different portions of entries.
The following summary applies to primary database backends such as
the LDBM, BDB, and HDB backends.   Requirements for other backends may
(and often do) differ.
.LP
The
.B add
operation requires
.B write (=w)
privileges on the pseudo-attribute 
.B entry
of the entry being added, and 
.B write (=w)
privileges on the pseudo-attribute
.B children
of the entry's parent.
.LP
The 
.B bind
operation, when credentials are stored in the directory, requires 
.B auth (=x)
privileges on the attribute the credentials are stored in (usually
.BR userPassword ).
.LP
The
.B compare
operation requires 
.B compare (=c)
privileges on the attribute that is being compared.
.LP
The
.B delete
operation requires
.B write (=w)
privileges on the pseudo-attribute
.B entry 
of the entry being deleted, and
.B write (=w)
privileges on the
.B children
pseudo-attribute of the entry's parent.
.LP
The
.B modify
operation requires 
.B write (=w)
privileges on the attibutes being modified.
.LP
The
.B modrdn
operation requires
.B write (=w)
privileges on the pseudo-attribute
.B entry
of the entry whose relative DN is being modified,
.B write (=w)
privileges on the pseudo-attribute
.B children
of the old and new entry's parents, and
.B write (=w)
privileges on the attributes that are present in the new relative DN.
.B Write (=w)
privileges are also required on the attributes that are present 
in the old relative DN if 
.B deleteoldrdn
is set to 1.
.LP
The
.B search
operation, for each entry, requires
.B search (=s)
privileges on the attributes that are defined in the filter.
Then, the resulting entries are tested for 
.B read (=r)
privileges on the pseudo-attribute
.B entry
(for read access to the entry itself)
and for
.B read (=r)
access on each value of each attribute that is requested.
Also, for each
.B referral
object used in generating continuation references, the operation requires
.B read (=r)
access on the pseudo-attribute
.B entry
(for read access to the referral object itself),
as well as
.B read (=r)
access to the attribute holding the referral information
(generally the
.B ref
attribute).
.LP
Some
.B controls
require specific access privileges.
The
.B proxyAuthz
control requires
.B 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
.B sasl-regexp
directives).
It also requires
.B auth (=x)
privileges on the
.B saslAuthzTo
attribute of the authorizing identity and/or on the 
.B saslAuthzFrom
attribute of the authorized identity.
.SH CAVEATS
It is strongly recommended to explicitly use the most appropriate
.BR <dnstyle> ,
to avoid possible incorrect specifications of the access rules as well
as for performance (avoid unrequired regex matching when an exact
match suffices) reasons.
.LP
An administrator might create a rule of the form:
.LP
.nf
	access to dn.regex="dc=example,dc=com"
		by ...
.fi
.LP
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".
.LP
To match the desired subtree, the rule would be more precisely
written:
.LP
.nf
	access to dn.regex="^(.+,)?dc=example,dc=com$$"
		by ...
.fi
.LP
For performance reasons, it would be better to use the subtree style.
.LP
.nf
	access to dn.subtree="dc=example,dc=com"
		by ...
.fi
.LP
When writing submatch rules, it may be convenient to avoid unnecessary
.B regex
.B <dnstyle>
use; for instance, to allow access to the subtree of the user 
that matches the
.B what
clause, one could use
.LP
.nf
	access to dn.regex="^(.+,)?uid=([^,]+),dc=example,dc=com$$"
		by dn.regex="^uid=$1,dc=example,dc=com$$" write
		by ...
.fi
.LP
However, since all that is required in the 
.B to
clause is substring expansion, a more efficient solution is
.LP
.nf
	access to dn.regex="^(.+,)?uid=([^,]+),dc=example,dc=com$$"
		by dn.exact,expand="uid=$1,dc=example,dc=com" write
		by ...
.fi
.LP
In fact, while a
.B <dnstyle>
of
.B regex
implies substring expansion, 
.BR exact ,
as well as all the other DN specific
.B <dnstyle>
values, does not, so it must be explicitly requested.
.LP
.SH FILES
.TP
ETCDIR/slapd.conf
default slapd configuration file
.SH SEE ALSO
.BR slapd (8),
.LP
"OpenLDAP Administrator's Guide" (http://www.OpenLDAP.org/doc/admin/)
.SH ACKNOWLEDGEMENTS
.B OpenLDAP
is developed and maintained by The OpenLDAP Project (http://www.openldap.org/).
.B OpenLDAP
is derived from University of Michigan LDAP 3.3 Release.