slapd.access (5)

Contents

NAME
SYNOPSIS
DESCRIPTION
THE ACCESS DIRECTIVE
THE <WHAT> FIELD
THE <WHO> FIELD
THE <ACCESS> FIELD
THE <CONTROL> FIELD
OPERATION REQUIREMENTS
CAVEATS
FILES
SEE ALSO
ACKNOWLEDGEMENTS

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 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").

When dealing with an access list, because the global access list is effectively appended to each per-database list, if the resulting list is non-empty then the access list will end with an implicit access to * by * none directive. If there are no access directives applicable to a backend, then a default read is used.

Be warned: the rootdn can always read and write EVERYTHING!

For entries not held in any backend (such as a root DSE), the 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>).

Lists of access directives are evaluated in the order they appear in slapd.conf. When a <what> clause matches the datum whose access is being evaluated, its <who> clause list is checked. When a <who> clause matches the accessor's properties, its <access> and <control> clauses are evaluated. Access control checking stops at the first match of the <what> and <who> clause, unless otherwise dictated by the <control> clause. Each <who> clause list is implicitly terminated by a 

        by * none stop

clause that results in stopping the access control with no access privileges granted. Each <what> clause list is implicitly terminated by a 

        access to *
                by * none

clause that results in granting no access privileges to an otherwise unspecified datum.

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 4515. 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. Submatches resulting from regex matching can be dereferenced in the <who> field using the syntax ${v<n>}, where <n> is the submatch number. The default syntax, $<n>, is actually an alias for ${d<n>}, that corresponds to dereferencing submatches from the dnpattern portion of the <what> field.

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>

        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|ipv6|path}
        <domainstyle>={exact|regex|sub(tree)}
        <setstyle>={exact|expand}
        <modifier>={expand}
        <name>=aci              <pattern>=<attrname>]

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.
Substring substitution from attribute value can
be done in 
using the form
${v<digit>+}.

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>

for IPv4, or
IP=[<ipv6>]:<port>

for IPv6)
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.
The same applies to IPv6 addresses when the special
ipv6

style is used.
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>:

((peername & <mask>) == <ip>).
As an example, 
peername.ip=127.0.0.1

and
peername.ipv6=::1

allow 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
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.



The statement
dynacl/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 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 optional 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|add|delete}|manage
        <priv> ::= {=|+|-}{0|d|x|c|s|r|{w|a|z}|m}+






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, while being not allowed
to affect 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,

write,

and
manage.

Each access level implies all the preceding ones, thus 
manage

grants all access including administrative access.
The 
write

access is actually the combination of
add

and
delete,

which respectively restrict the write privilege to add or delete
the specified
<what>.






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
m

for manage,
w

for write,
a

for add,
z

for delete,
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).
Note that
+az

is equivalent to
+w.




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
add (=a)

privileges on the pseudo-attribute 
entry

of the entry being added, and 
add (=a)

privileges on the pseudo-attribute
children

of the entry's parent.
When adding the suffix entry of a database,
add

access to
children

of the empty DN ("") is required. Also if
Add content ACL checking has been configured on
the database (see the
slapd.conf(5)

or
slapd-config(5)

manual page),
add (=a)

will be required on all of the attributes being added.





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
delete (=z)

privileges on the pseudo-attribute
entry 

of the entry being deleted, and
delete (=d)

privileges on the
children

pseudo-attribute of the entry's parent.





The
modify

operation requires 
write (=w)

privileges on the attributes being modified.
In detail, 
add (=a)

is required to add new values,
delete (=z)

is required to delete existing values,
and both
delete

and
add (=az),

or
write (=w),

are required to replace existing values.





The
modrdn

operation requires
write (=w)

privileges on the pseudo-attribute
entry

of the entry whose relative DN is being modified,
delete (=z)

privileges on the pseudo-attribute
children

of the old entry's parents,
add (=a)

privileges on the pseudo-attribute
children

of the new entry's parents, and
add (=a)

privileges on the attributes that are present in the new relative DN.
Delete (=z)

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 OpenLDAP 2.4).
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.
In general, when an internal lookup is performed for authentication
or authorization purposes, search-specific privileges (see the access
requirements for the search operation illustrated above) are relaxed to
auth.






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





/etc/ldap/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 Software

is developed and maintained by The OpenLDAP Project <http://www.openldap.org/>.
OpenLDAP Software

is derived from University of Michigan LDAP 3.3 Release.