openldap/doc/guide/admin/security.sdf

# Copyright 1999-2001, The OpenLDAP Foundation, All Rights Reserved.
# COPYING RESTRICTIONS APPLY, see COPYRIGHT.

H1: Security Considerations

OpenLDAP Software is designed to run in a wide variety of computing
environments from tightly-controlled closed networks to the global
Internet.  Hence, OpenLDAP Software provides many different security
mechanisms.  This chapter describes these mechanisms and discusses
security considerations for using OpenLDAP Software.

H2: Network Security

H3: Selective Listening

By default, {{slapd}}(8) will listen on both the IPv4 and IPv6 "any"
addresses.  It is often desirable to have {{slapd}} listen on select
address/port pairs.  For example, listening only on the IPv4 address
{{EX:127.0.0.1}} will disallow remote access to the directory server.
E.g.:

>	slapd -h ldap://127.0.0.1

While the server can be configured to listen on a particular interface
address, this doesn't necessarily restrict access to the server to
only those networks accessible via that interface.   To selective
restrict remote access, it is recommend that an {{SECT:IP Firewall}}
be used to restrict access.

See {{SECT:Command-line Options}} and {{slapd}}(8) for more
information.


H3: IP Firewall

{{TERM:IP}} firewall capabilities of the server system can be used
to restrict access based upon the client's IP address and/or network
interface used to communicate with the client.

Generally, {{slapd}}(8) listens on port 389/tcp for LDAP over
{{TERM:TCP}} (e.g.  {{F:ldap://}}) and port 636/tcp for LDAP over
{{TERM:SSL}} (e.g.  {{F:ldaps://}}).  Note that LDAP over TCP
sessions can be protected by {{TERM:TLS}} through the use of
{{StartTLS}}.  StartTLS is the Standard Track mechanism for protecting
LDAP sessions with TLS.

As specifics of how to configure IP firewall are dependent on the
particular kind of IP firewall used, no examples are provided here.
See the document associated with your IP firewall.


H3: TCP Wrappers

OpenLDAP supports {{TERM:TCP}} Wrappers.  TCP Wrappers provide a rule-based
access control system for controlling TCP/IP access to the server.
For example, the {{host_options}}(5) rule:

>	slapd: 10.0.0.0/255.0.0.0 127.0.0.1 : ALLOW
>	slapd: ALL : DENY

allows only incoming connections from the private network {{F:10.0.0.0}}
and localhost ({{F:127.0.0.1}}) to access the directory service.
Note that IP addresses are used as {{slapd}}(8) is not normally
configured to perform reverse lookups.

It is noted that TCP wrappers require the connection to be accepted.
As significant processing is required just to deny a connection,
it is generally advised that IP firewall protection be used instead
of TCP wrappers.

See {{hosts_access}}(5) for more information on TCP wrapper rules.


H2: Integrity and Confidentiality Protection

{{TERM[expand]TLS}} (TLS) can be used to provide integrity and
confidentiality protection.  OpenLDAP supports both StartTLS and
{{F:ldaps://}}.  See the {{SECT:Using TLS}} chapter for more
information.

A number of {{TERM[expand]SASL}} (SASL) mechanisms, such as DIGEST-MD5
and {{TERM:GSSAPI}}, also provide integrity and confidentiality
protection.  See the {{SECT:Using SASL}} chapter for more information.


H3: Security Strength Factors

The server uses {{TERM[expand]SSF}}s (SSF) to indicate the relative
strength of protection.  A SSF of zero (0) indicates no protections
are in place.  A SSF of one (1) indicates integrity protection are
in place.  A SSF greater than one (>1) roughly correlates to the
effective encryption key length.  For example, {{TERM:DES}} is 56,
{{TERM:3DES}} is 112, and {{TERM:AES}} 128, 192, or 256.

A number of administrative controls rely on SSFs associated with
TLS and SASL protection in place on an LDAP session.

{{EX:security}} controls disallow operations when appropriate
protections are not in place.  For example:

>	security ssf=1 update_ssf=112

requires integrity protection for all operations and encryption
protection, 3DES equivalent, for update operations (e.g. add, delete,
modify, etc.).  See {{slapd.conf}}(5) for details.

For fine-grained control, SSFs may be used in access controls.  See
{{SECT:Access Control}} section of the {{SECT:The slapd Configuration
File}} for more information.


H2: Authentication Methods

H3: "simple" method

The LDAP "simple" method has three modes of operation:

* anonymous,
* unauthenticated, and
* user/password authenticated.

Anonymous access is obtained by providing no name and no password
to the "simple" bind operation.  Unauthenticated access is obtained
by providing a name but no password.  Authenticated access is obtain
by providing a valid name and password.

An anonymous bind results in an {{anonymous}} authorization.
Anonymous bind mechanism is enabled by default, but can be disabled
by specifying "{{EX:disallow bind_anon}}" in {{slapd.conf}}(5).

An unauthenticated bind results in an {{anonymous}} authorization.
Unauthenticated bind mechanism is disabled by default, but can be
enabled by specifying "{{EX:allow bind_anon_cred}}" in {{slapd.conf}}(5).
As a number of LDAP applications mistakenly generate unauthenticated
bind request when authenticated access was intended (that is, they
do not ensure a password was provided), this mechanism should
generally not be enabled.

A successful user/password authenticated bind results in a user
authorization identity, the provided name, being associated with
the session.  User/password authenticated bind is enabled by default.
However, as this mechanism offers no evesdropping protection (e.g.,
the password is set in the clear), it is recommended that it be
used only in tightly controlled systems or when the LDAP session
is protected by other means (e.g., TLS, {{TERM:IPSEC}}).  Where the
administrator relies on TLS to protect the password, it is recommended
that unprotected authentication be disabled.  This is done by setting
"{{EX:disallow bind_simple_unprotected}}" in {{slapd.conf}}(5).
The user/password authenticated bind mechanism can be completely
disabled by setting "{{EX:disallow bind_simple}}".

Note:  An unsuccessful bind always results in the session having
an {{anonymous}} authorization state.


H3: SASL method

The LDAP SASL method allows use of any SASL authentication
mechanism.  The {{SECT:Using SASL}} discusses use of SASL.