slapd.access
NAME
slapd.access - access configuration for slapd, the stand-alone LDAP daemon
SYNOPSIS
/etc/ldap/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
R <access> )
to a set of entries and/or attributes (specified by
R <what> )
by one or more requestors (specified by
R <who> ).
THE <WHAT> FIELD
The field
R <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
R baseObject ),
the default,
or
exact
(an alias of
R base )
indicates the entry whose DN is equal to the
R <dnpattern> ;
one
(synonym of
R onelevel )
indicates all the entries immediately below the
R <dnpattern> ,
sub
(synonym of
R subtree )
indicates all entries in the subtree at the
R <dnpattern> ,
children
indicates all the entries below (subordinate to) the
R <dnpattern> .
If the
<dnstyle>
qualifier is
R 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
R entry ,
indicating access to the entry itself, and
R 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
R 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
R base ,
R onelevel ,
subtree
or
R 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
R $<digit> ,
with
digit
ranging from 0 to 9 (where 0 matches the entire string),
or the form
R ${<digit>+} ,
for submatches higher than 9.
Since the dollar character is used to indicate a substring replacement,
the dollar character that is used to indicate match up to the end of
the string must be escaped by a second dollar character, e.g.
access to dn.regex="^(.+,)?uid=([^,]+),dc=[^,]+,dc=com$"
by dn.regex="^uid=$2,dc=[^,]+,dc=com$$" write
The style qualifier
allows an optional
R modifier .
At present, the only type allowed is
R expand ,
which causes substring substitution of submatches to take place
even if
dnstyle
is not
R 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
R base(object) ,
the
R sub(tree) ,
the
R one(level) ,
and the
R children
forms provide
$0
as the match of the entire string.
The
R sub(tree) ,
the
R one(level) ,
and the
R 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
R level{<n>}
form is an extension and a generalization of the
R 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
R 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
R <group> .
The optional parameters
<objectclass>
and
<attrname>
define the objectClass and the member attributeType of the group entry.
The defaults are
groupOfNames
and
R member ,
respectively.
The optional style qualifier
<style>
can be
R 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
R 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
R peername=<peername> ,
R sockname=<sockname> ,
R domain=<domain> ,
and
R sockurl=<sockurl>
mean that the contacting host IP (in the form
R IP=<ip>:<port> )
or the contacting host named pipe file name (in the form
PATH=<path>
if connecting through a named pipe) for
R peername ,
the named pipe file name for
R sockname ,
the contacting host name for
R domain ,
and the contacting URL for
R 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
R <peername>
clause (the default) implies a case-exact match on the client's
R IP ,
including the
IP=
prefix and the trailing
R :<port> ,
or the client's
R path ,
including the
PATH=
prefix if connecting through a named pipe.
The special
ip
style interprets the pattern as
R <peername>=<ip>[%<mask>][{<n>}] ,
where
<ip>
and
<mask>
are dotted digit representations of the IP and the mask, while
R <n> ,
delimited by curly brackets, is an optional port.
When checking access privileges, the IP portion of the
R 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
R <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
R <domain>
clause also allows the
subtree
style, which succeeds when a fully qualified name exactly matches the
R domain
pattern, or its trailing part, after a
R dot ,
exactly matches the
R 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
R expand ,
which causes substring substitution of submatches to take place even if
the
domainstyle
is not
R 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
R <name> ,
which can be registered at run-time by means of the
moduleload
statement.
The fields
R <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,
R <patten>=<attrname> .
However, the original ACI syntax is preserved for backward compatibility.
The statements
R ssf=<n> ,
R transport_ssf=<n> ,
R tls_ssf=<n> ,
and
R 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
R none ,
R disclose ,
R auth ,
R compare ,
R search ,
R read ,
and
R 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.
R 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
R +0 .
THE <CONTROL> FIELD
The optional field
<control>
controls the flow of access rule application.
It can have the forms
stop continue break
where
R 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
R 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
R 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,
R exact ,
as well as all the other DN specific
<dnstyle>
values, does not, so it must be explicitly requested.
FILES
/etc/ldap/slapd.conf
default slapd configuration file
SEE ALSO
"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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