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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 slapacl(8), slapadd(8), slapauth(8),
slapcat(8), slapdn(8), slapindex(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"). The rootdn can always read and write EVERYTHING!
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>]=<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 2254. 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.
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[.<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>
aci[=<attrname>]
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|path}
<domainstyle>={exact|regex|sub(tree)}
<setstyle>={exact|regex}
<modifier>={expand}
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 ${<digit>+}, for submatches higher than 9. Since the
dollar character is used to indicate a substring replacement, the dollar
character that is used to indicate match up to the end of the string must
be escaped by a second dollar character, e.g.
access to dn.regex="^(.+,)?uid=([^,]+),dc=[^,]+,dc=com$"
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>) 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. 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 allows 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. 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 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. If dynacl and ACIs are
both enabled, ACIs are cast into the dynacl scheme, where <name>=aci and,
optionally, <patten>=<attrname>. However, the original ACI syntax is
preserved for backward compatibility.
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 <ACCESS> FIELD
The 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
<priv> ::= {=|+|-}{w|r|s|c|x|d|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
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, without affecting
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, and write. Each access level implies all the preceding ones,
thus write access will imply all accesses.
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 w for write, 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). If no access is given, it defaults
to +0.
THE <CONTROL> FIELD
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.
OPERATION REQUIREMENTS
Operations require different privileges on different portions of entries.
The following summary applies to primary database backends such as the 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. When adding the suffix entry of
a database, write access to children of the empty DN ("") is required.
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 attributes 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, requires search (=s) privileges on the entry pseudo-
attribute of the searchBase (NOTE: this was introduced with 2.3). 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 authzID mapping and the 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.
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. back-bdb(5), and back-hdb(5).
Some other backend, like back-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.
CAVEATS
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.
FILES
/usr/internet/openldap/etc/slapd.conf
default slapd configuration file
SEE ALSO
slapd(8), slapd-*(5), slapacl(8), regex(7), re_format(7)
"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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