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SLAPD.ACCESS(5)
NAME
slapd.access - access configuration for slapd, the stand-alone LDAP daemon
SYNOPSIS
/usr/internet/openldap/etc/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 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 <WHAT> 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 context.
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) indicates 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 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.
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 <WHO> 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
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 objectClass 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 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>) 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 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. 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>. As an example, peername.ip=127.0.0.1 alows
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 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 <ACCESS> 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 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 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 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 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.
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.
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 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 controls require specific access privileges. The proxyAuthz control
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) privileges 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=$1,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=$1,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
/usr/internet/openldap/etc/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.
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