security.sdf

OpenLdap是LDAP的开源项目

# Copyright 1999-2007 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 supports 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 {{F:ldap://}}
sessions and port 636/tcp for {{F:ldaps://}}) sessions.  {{slapd}}(8)
may be configured to listen on other ports.

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

{{slapd}}(8) 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: Data Integrity and Confidentiality Protection

{{TERM[expand]TLS}} (TLS) can be used to provide data integrity and
confidentiality protection.  OpenLDAP supports negotiation of
{{TERM:TLS}} ({{TERM:SSL}}) via both StartTLS and {{F:ldaps://}}.
See the {{SECT:Using TLS}} chapter for more information.  StartTLS
is the standard track mechanism.

A number of {{TERM[expand]SASL}} (SASL) mechanisms, such as DIGEST-MD5
and {{TERM:GSSAPI}}, also provide data 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 requested by providing no name and no password
to the "simple" bind operation.  Unauthenticated access is requested
by providing a name but no password.  Authenticated access is
requested by providing a valid name and password.

An anonymous bind results in an {{anonymous}} authorization
association.  Anonymous bind mechanism is enabled by default, but
can be disabled by specifying "{{EX:disallow bind_anon}}" in
{{slapd.conf}}(5).  Note that disabling the anonymous bind mechanism
does not prevent anonymous access to the directory.  To require
authentication to access the directory, one should instead
specify "{{EX:require authc}}".

An unauthenticated bind also results in an {{anonymous}} authorization
association.  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 remain disabled.

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 itself 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 using the {{EX:security}} directive's {{EX:simple_bind}}
option, which provides fine grain control over the level of confidential
protection to require for {{simple}} user/password authentication.
E.g., using {{EX:security simple_bind=56}} would require {{simple}}
binds to use encryption of DES equivalent or better.

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 association.


H3: SASL method

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