Ubuntu Manpage: pam_ldap - LDAP pluggable authentication module

Provided by: libpam-ldap_184-8.7ubuntu1_amd64

NAME

       pam_ldap - LDAP pluggable authentication module

DESCRIPTION

The pam_ldap module is a Pluggable Authentication Module (PAM) which provides for authentication,
authorization and password changing against LDAP servers.

Features of the PADL pam_ldap module include support for transport layer security, SASL authentication,
directory server-enforced password policy, and host- and group- based logon authorization.

The present version of pam_ldap supports AIX 5L, FreeBSD 3.x and above, HP-UX 11i, IRIX 6.x, Linux, Mac
OS X 10.2 and above, and Solaris 2.6 and above. Many vendors provide their own LDAP authentication
providers, often also called pam_ldap. This manual page applies to the PADL pam_ldap module only. If you
are using a vendor provided module, consult the relevant documentation instead.

When authenticating or authorizing a user, pam_ldap first maps the user's login name to a distinguished
name by searching the directory server. This must be possible using the local system's identity,
specified in ldap.conf. (Note that presently only simple authentication is supported for authenticating
in this initial step.)

To authenticate a user, pam_ldap attempts to bind to the directory server using the distinguished name of
the user (retrieved previously). Both simple and SASL authentication mechanisms are supported; in the
former case, one should take care to use transport security to prevent the user's password being
transmitted in the clear.

A variety of authorization primitives are supported by pam_ldap, discussed in the configuration section
below.

Finally, pam_ldap supports a number of password change protocols used by directory servers from various
vendors. (Some directory servers support more than one password change protocol.)

Whilst pam_ldap is generally configured in the system LDAP naming configuration file (ldap.conf), some
options can be configured in the PAM configuration file, to allow for per-service granularity. These
options include the path to the LDAP naming configuration file to use, so in effect all options can be
configured on a per-service basis. Options are listed below under PAM Configuration.

CONFIGURATION

pam_ldap stores its configuration in the ldap.conf file. (It should be noted that some LDAP client
libraries, such as OpenLDAP, also use a configuration file of the same name. pam_ldap supports many of
the same configuration file options as OpenLDAP, but it adds several that are specific to the
functionality it provides. It is not guaranteed that pam_ldap will continue to match the configuration
file semantics of OpenLDAP. You may wish to use different files.)

Configuration file options consist of a keyword followed by a space and any arguments. The following
options are supported by both pam_ldap and the PADL nss_ldap module:

host <name:port ...>
Specifies the name(s) or IP address(es) of the LDAP server(s) to connect to. In the case that
nss_ldap is used for host name resolution, each server should be specified as an IP address or
name that can be resolved without using LDAP. Multiple servers may be specified, each separated
by a space. The failover time depends on whether the LDAP client library supports configurable
network or connect timeouts (see bind_timelimit below).

base <base>
Specifies the default base distinguished name (DN) to use for searches.

uri <ldap[is]://[name[:port]] ...>
For LDAP client libraries that support it, specifies the URI(s) of the LDAP server(s) to connect
to. The URI scheme may be ldap, ldapi, or ldaps, specifying LDAP over TCP, IPC and SSL
respectively. If applicable, a port number can be specified; the default port number for the
selected protocol is used if omitted. This option takes precedence over the host option; it is not
possible to combine the two.

ldap_version <version>
Specifies the version of the LDAP protocol to use. Presently version must be 2 or 3. The default
is to use the maximum version supported by the client library.

binddn <binddn>
Specifies the distinguished name with which to bind to the directory server(s). This option is
optional; the default is to bind anonymously.

bindpw <bindpw>
Specifies the cleartext credentials with which to bind. This option is only applicable when used
with binddn above. The default is no credential (anonymous bind). When binding to the directory
using SASL or other authentication mechanisms apart from simple binds, this option is not used.

rootbinddn <binddn>
This option has the same syntax and effect as the binddn option above, except it applies when the
effective user ID is zero. If not specified, then the identity specified in binddn is used
instead. Because the configuration file may be readable by many users, the root bind DN
credentials are stored in the ldap.secret file instead. This file is usually in the same directory
as the configuration file.

port <port>
Specifies the port to connect to; this option is used with the host option, and is ignored with
the uri option.

scope <sub|one|base>
Specifies the search scope (subtree, one level or base object). The default scope is subtree; base
scope is almost never useful for nameservice lookups.

deref <never|searching|finding|always>
Specifies the policy for dereferencing aliases. The default policy is to never dereference
aliases.

timelimit <timelimit>
Specifies the time limit (in seconds) to use when performing searches. A value of zero (0), which
is the default, is to wait indefinitely for searches to be completed.

bind_timelimit <timelimit>
Specifies the time limit (in seconds) to use when connecting to the directory server. This is
distinct from the time limit specified in timelimit and affects the initial server connection
only. (Server connections are otherwise cached.) Only some LDAP client libraries have the
underlying functionality necessary to support this option. The default bind timelimit is 30
seconds.

referrals <yes|no>
Specifies whether automatic referral chasing should be enabled. The default behaviour is specifed
by the LDAP client library.

restart <yes|no>
Specifies whether the LDAP client library should restart the select(2) system call when
interrupted. This feature is not supported by all client libraries.

logdir <directory>
Specifies the directory used for logging by the LDAP client library. This feature is not supported
by all client libraries.

debug <level>
Specifies the debug level used for logging by the LDAP client library. This feature is not
supported by all client libraries, and does not apply to the nss_ldap and pam_ldap modules
themselves (debugging, if any, is configured separately and usually at compile time).

ssl <on|off|start_tls>
Specifies whether to use SSL/TLS or not (the default is not to). If start_tls is specified then
StartTLS is used rather than raw LDAP over SSL. Not all LDAP client libraries support both SSL
and StartTLS, and all related configuration options.

sslpath <cert7_path>
For the Netscape and Mozilla LDAP client libraries only, this specifies the path to the X.509
certificate database.

tls_checkpeer <yes|no>
Specifies whether to require and verify the server certificate or not, when using SSL/TLS with the
OpenLDAP client library. The default is to use the default behaviour of the client library; for
OpenLDAP 2.0 and earlier it is "no", for OpenLDAP 2.1 and later it is "yes". At least one of
tls_cacertdir and tls_cacertfile is required if peer verification is enabled.

tls_cacertdir <certificate_dir>
Specifies the directory containing X.509 certificates for peer authentication.

tls_cacertfile <certificate_file>
Specifies the path to the X.509 certificate for peer authentication.

tls_randfile <entropy_file>
Specifies the path to an entropy source.

tls_ciphers <ciphers>
Specifies the ciphers to use for TLS. See your TLS implementation's documentation for further
information.

tls_cert <certificate_file>
Specifies the path to the file containing the local certificate for client TLS authentication.

tls_key <key_file>
Specifies the path to the file containing the private key for client TLS authentication.

The following configuration options apply to pam_ldap only:

pam_login_attribute <attribute>
Specifies the attribute to use when constructing the attribute value assertion for retrieving a
directory entry for a user's login name. The default is "uid", for compatibility with RFC 2307.

pam_filter <filter>
Specifies a filter to use when retrieving user information. The user entry must match the
attribute value assertion of (pam_login_attribute=login_name) as well as any filter specified
here. There is no default for this option.

pam_lookup_policy <yes|no>
Specifies whether to search the root DSE for password policy. The default is "no".

pam_check_host_attr <yes|no>
Specifies whether the "host" attribute should be checked for logon authorization ("account" in the
PAM stack). The default is not to. If set to "yes" and a user has no value for the "host"
attribute, then the user will be unable to login.

pam_check_service_attr <yes|no>
Specifies whether the "authorizedService" attribute should be checked for logon authorization
("account" in the PAM stack). The default is not to. If set to "yes" and a user has no value for
the "authorizedService" attribute, then the user will be unable to login.

pam_groupdn <groupdn>
Specifies the distinguished name of a group to which a user must belong for logon authorization to
succeed. pam_member_attribute <attribute> Specifies the attribute to use when testing a user's
membership of a group specified in the pam_groupdn option.

pam_min_uid <uid>
If specified, a user must have a POSIX user ID of at least uid in order for logon authorization to
succeed.

pam_max_uid <uid>
If specified, a user must have a POSIX user ID of no greater than uid in order for logon
authorization to succeed.

pam_template_login_attribute <attribute>
When using template users (not supported by all PAM applications), specifies the attribute
containing the user's actual login name. The pam_ldap module will set PAM_USER to the value of
this attribute if present in the user's entry, otherwise it defaults to the user specified in the
pam_template_login option.

pam_template_login <user>
When using template users (not supported by all PAM applications), pam_ldap will set PAM_USER to
the value of this option if the user does not contain a template login attribute.

pam_password <protocol>
Specifies the password change protocol to use. The following protocols are supported:

clear Change password using an LDAPModify request, replacing the userPassword value with the new
cleartext password.

clear_remove_old
Change password using an LDAPModify request, first removing the userPassword value
containing the old cleartext password, and then adding the userPassword value with the new
cleartext password. This protocol is necessary for use with Novell NDS and IBM RACF.

crypt Change password using an LDAPModify request, first generating a one way hash of the new
password using crypt(3) and then replacing userPassword value with the new hashed password.

md5 Change password using an LDAPModify request, first generating a one way hash of the new
password using MD5 and then replacing userPassword value with the new hashed password.

nds This is an alias for clear_remove_old.

racf This is an alias for clear_remove_old.

ad Change password using an LDAPModify request, using the Active Directory Services Interface
(ADSI) password change protocol.

exop Change password using the RFC 3062 password modify extended operation (only the new
password is sent).

exop_send_old
Change password using the RFC 3062 password modify extended operation (both the old and new
passwords are sent).

pam_password_prohibit_message <message>
Specifies a message to send to users indicating that passwords cannot be changed. This could be
used to redirect users to another means of changing passwords.

pam_sasl_mech <mechanism>
Specifies the SASL mechanism to use for PAM authentication. This requires SASL libraries be
installed. Support for this functionality presently experimental and does not support password
policy controls.

PAM CONFIGURATION

It is possible to configure some aspects of pam_ldap on a per-service basis, in the PAM configuration
file (this is usually /etc/pam.conf; for PAM implementations based on Linux-PAM, per-service files in
/etc/pam.d are also supported).

The following options may be specified as arguments to the pam_ldap module:

config=<path>
Specifies that pam_ldap should use the configuration file in path instead of ldap.conf to retrieve
its global configuration. Configuring multiple instances of pam_ldap for the same service with
different configuration files is not supported, because the configuration information is cached.

use_first_pass
Specifies that pam_ldap should always use the first password provided in the authentication stack.

try_first_pass
Specifies that pam_ldap should first try the first password provided in the authentication stack,
and then prompt the user for their LDAP password if authentication fails.

ignore_unknown_user
Specifies that pam_ldap should return PAM_IGNORE for users that are not present in LDAP. This
forces the PAM framework to ignore the pam_ldap module. This option is useful where certain
accounts do not reside in LDAP, but one wishes to make pam_ldap "required" for all accounts in the
directory. In this case one would make both pam_ldap and the other module (for example, pam_unix)
"required" and enable the ignore_unknown_user option. (For this to work, the other module must
behave similarly for users in the directory; in the case of a module such as pam_unix that uses
the system accounts database, using nss_ldap(5) should be sufficient to meet this requirement.)

ignore_authinfo_unavail
Specifies that pam_ldap should return PAM_IGNORE if it cannot contact the LDAP server. This option
forces the PAM framework to ignore the pam_ldap module in this case.

no_warn
Specifies that warning messages should not be propagated to the PAM application.

use_authtok
Analogous to use_first_pass for password changing only.

debug This option is recognized by pam_ldap but is presently ignored.

AUTHOR

       The pam_ldap module was developed by PADL Software Pty Ltd (www.padl.com).

FILES