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), fol-
lowed by zero or more database backend definitions that contain infor-
mation 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 direc-
tives from the global configuration section are then used.
For entries not held in any backend (such as a root DSE), the direc-
tives of the first backend (and any global directives) 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
(specified by <who>).
THE FIELD
The field <what> specifies the entity the access control directive
applies to. It can have the forms
*
[dn[.<dnstyle>]=<DN>]
[filter=<ldapfilter>]
[attrs=<attrlist>[ val[.<style>]=<attrval>]]
The wildcard * stands for all the entries.
The statement dn=<DN> selects the entries based on their naming con-
text. The pattern is a string representation of the entry's DN. base,
the default, or exact (an alias of base) indicates the entry whose DN
is equal to the pattern; one (synonym of onelevel) indicates all the
entries immediately below the pattern, sub (synonym of subtree) indi-
cates all entries in the subtree at the pattern, children indicates all
the entries below (subordinate to) the pattern.
If the <dnstyle> qualifier is regex, then the value is a regular
expression pattern, as detailed in regex(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 2254.
The statement attrs=<attrlist> selects the attributes the access con-
trol 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. Actu-
ally, 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.
Using the form 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 <style> of exact (the default)
uses the attribute's equality matching rule to compare the value. If
the value <style> is regex, the provided value is used as a regular
expression pattern. If the attribute has DN syntax, the value <style>
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.
THE 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
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[.<setstyle>]=<pattern>
ssf=<n>
transport_ssf=<n>
tls_ssf=<n>
sasl_ssf=<n>
aci=<attrname>
with
<dnstyle>={{exact|base}|regex|sub(tree)|one(level)|children}
<groupstyle>={exact|expand}
<style>={exact|regex|expand}
<peernamestyle>={<style>|ip|path}
<domainstyle>={exact|regex|sub(tree)}
<setstyle>={exact|regex}
<modifier>={expand}
They may be specified in combination.
The wildcard * refers to everybody.
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).
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 1 to 9. 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. 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.
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 object-
Class and the member attributeType of the group entry. 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 exact, which means that exact match will be
used.
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=<domain>, and sockurl=<sockurl> mean that the contacting host IP
(in the form IP=<ip>:<port>) 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(7) match of the corresponding connec-
tion 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 inter-
prets 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. When checking
access privileges, the IP portion of the peername is extracted, elimi-
nating the IP= prefix and the :<port> part, and it is compared against
the <ip> portion of the pattern after masking with <mask>. As an exam-
ple, peername.ip=127.0.0.1 alows 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
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 aci=<attrname> means that the access control is deter-
mined 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
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|0}+
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 triv-
ial, 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 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 w for write, r for read, s
for search, c for compare, and x for authentication. 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).
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.
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 back-
ends may (and often do) differ.
The add operation requires write (=w) privileges on the pseudo-
attribute entry of the entry being added, and write (=w) privileges on
the pseudo-attribute children of the entry's parent.
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 write (=w) privileges on the pseudo-
attribute entry of the entry being deleted, and write (=w) privileges
on the children pseudo-attribute of the entry's parent.
The modify operation requires write (=w) privileges on the attibutes
being modified.
The modrdn operation requires write (=w) privileges on the pseudo-
attribute entry of the entry whose relative DN is being modified, write
(=w) privileges on the pseudo-attribute children of the old and new
entry's parents, and write (=w) privileges on the attributes that are
present in the new relative DN. Write (=w) privileges are also
required on the attributes that are present in the old relative DN if
deleteoldrdn is set to 1.
The search operation, for each entry, requires search (=s) privileges
on the attributes that are defined in the filter. Then, the resulting
entries are 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 refer-
ral 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 controls require specific access privileges. The proxyAuthz con-
trol requires 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 sasl-regexp directives). It also requires auth (=x) privi-
leges on the saslAuthzTo attribute of the authorizing identity and/or
on the saslAuthzFrom attribute of the authorized identity.
CAVEATS
It is strongly recommended to explicitly use the most appropriate
<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.
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 to 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.
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.
OpenLDAP 2.2.30 2005/11/18 SLAPD.ACCESS(5)
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