path: root/usr.bin/sudo/sudoers.ldap.pod

Copyright (c) 2003-2008
	Todd C. Miller <Todd.Miller@courtesan.com>

Permission to use, copy, modify, and distribute this software for any
purpose with or without fee is hereby granted, provided that the above
copyright notice and this permission notice appear in all copies.

THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

$Sudo: sudoers.ldap.pod,v 1.10 2008/05/10 13:18:47 millert Exp $
=pod

=head1 NAME

sudoers.ldap - sudo LDAP configuration

=head1 DESCRIPTION

In addition to the standard I<sudoers> file, B<sudo> may be configured
via LAP.  This can be especially useful for synchronizing I<sudoers>
in a large, distributed environment.

Using LDAP for I<sudoers> has several benefits:

=over 4

=item *

B<sudo> no longer needs to read I<sudoers> in its entirety.  When
LDAP is used, there are only two or three LDAP queries per invocation.
This makes it especially fast and particularly usable in LDAP
environments.

=item *

B<sudo> no longer exits if there is a typo in I<sudoers>.
It is not possible to load LDAP data into the server that does
not conform to the sudoers schema, so proper syntax is guaranteed.
It is still possible to have typos in a user or host name, but
this will not prevent B<sudo> from running.

=item *

It is possible to specify per-entry options that override the global
default options.  F<@sysconfdir@/sudoers> only supports default options and
limited options associated with user/host/commands/aliases.  The
syntax is complicated and can be difficult for users to understand.
Placing the options directly in the entry is more natural.

=item *

The B<visudo> program is no longer needed.  B<visudo> provides
locking and syntax checking of the F<@sysconfdir@/sudoers> file.
Since LDAP updates are atomic, locking is no longer necessary.
Because syntax is checked when the data is inserted into LDAP, there
is no need for a specialized tool to check syntax.

=back

Another major difference between LDAP and file-based I<sudoers>
is that in LDAP, B<sudo>-specific Aliases are not supported.

For the most part, there is really no need for B<sudo>-specific
Aliases.  Unix groups or user netgroups can be used in place of
User_Aliases and RunasAliases.  Host netgroups can be used in place
of HostAliases.  Since Unix groups and netgroups can also be stored
in LDAP there is no real need for B<sudo>-specific aliases.

Cmnd_Aliases are not really required either since it is possible
to have multiple users listed in a sudoRole.  Instead of defining
a Cmnd_Alias that is referenced by multiple users, one can create
a sudoRole that contains the commands and assign multiple users
to it.

=head2 SUDOers LDAP container

The I<sudoers> configuration is contained in the C<ou=SUDOers> LDAP
container.

Sudo first looks for the C<cn=default> entry in the SUDOers container.
If found, the multi-valued C<sudoOption> attribute is parsed in the
same manner as a global C<Defaults> line in F<@sysconfdir@/sudoers>.  In
the following example, the C<SSH_AUTH_SOCK> variable will be preserved
in the environment for all users.

    dn: cn=defaults,ou=SUDOers,dc=example,dc=com
    objectClass: top
    objectClass: sudoRole
    cn: defaults
    description: Default sudoOption's go here
    sudoOption: env_keep+=SSH_AUTH_SOCK
 
The equivalent of a sudoer in LDAP is a C<sudoRole>.  It consists of
the following components:

=over 4

=item B<sudoUser>

A user name, uid (prefixed with C<'#'>), Unix group (prefixed with
a C<'%'>) or user netgroup (prefixed with a C<'+'>).

=item B<sudoHost>

A host name, IP address, IP network, or host netgroup (prefixed
with a C<'+'>).
The special value C<ALL> will match any host.

=item B<sudoCommand>

A Unix command with optional command line arguments, potentially
including globbing characters (aka wild cards).
The special value C<ALL> will match any command.
If a command is prefixed with an exclamation point C<'!'>, the
user will be prohibited from running that command.

=item B<sudoOption>

Identical in function to the global options described above, but
specific to the C<sudoRole> in which it resides.

=item B<sudoRunAsUser>

A user name or uid (prefixed with C<'#'>) that commands may be run
as or a Unix group (prefixed with a C<'%'>) or user netgroup (prefixed
with a C<'+'>) that contains a list of users that commands may be
run as.
The special value C<ALL> will match any user.

=item B<sudoRunAsGroup>

A Unix group or gid (prefixed with C<'#'>) that commands may be run as.
The special value C<ALL> will match any group.

=back

Each component listed above should contain a single value, but there
may be multiple instances of each component type.  A sudoRole must
contain at least one C<sudoUser>, C<sudoHost> and C<sudoCommand>.

The following example allows users in group wheel to run any command
on any host via B<sudo>:

    dn: cn=%wheel,ou=SUDOers,dc=example,dc=com
    objectClass: top
    objectClass: sudoRole
    cn: %wheel
    sudoUser: %wheel
    sudoHost: ALL
    sudoCommand: ALL

=head2 Anatomy of LDAP sudoers lookup

When looking up a sudoer using LDAP there are only two or three
LDAP queries per invocation.  The first query is to parse the global
options.  The second is to match against the user's name and the
groups that the user belongs to.  (The special ALL tag is matched
in this query too.)  If no match is returned for the user's name
and groups, a third query returns all entries containing user
netgroups and checks to see if the user belongs to any of them.

=head2 Differences between LDAP and non-LDAP sudoers

There are some subtle differences in the way sudoers is handled
once in LDAP.  Probably the biggest is that according to the RFC,
LDAP ordering is arbitrary and you cannot expect that Attributes
and Entries are returned in any specific order.  If there are
conflicting command rules on an entry, the negative takes precedence.
This is called paranoid behavior (not necessarily the most specific
match).

Here is an example:

    # /etc/sudoers:
    # Allow all commands except shell
    johnny  ALL=(root) ALL,!/bin/sh
    # Always allows all commands because ALL is matched last
    puddles ALL=(root) !/bin/sh,ALL

    # LDAP equivalent of johnny
    # Allows all commands except shell
    dn: cn=role1,ou=Sudoers,dc=my-domain,dc=com
    objectClass: sudoRole
    objectClass: top
    cn: role1
    sudoUser: johnny
    sudoHost: ALL
    sudoCommand: ALL
    sudoCommand: !/bin/sh

    # LDAP equivalent of puddles
    # Notice that even though ALL comes last, it still behaves like
    # role1 since the LDAP code assumes the more paranoid configuration
    dn: cn=role2,ou=Sudoers,dc=my-domain,dc=com
    objectClass: sudoRole
    objectClass: top
    cn: role2
    sudoUser: puddles
    sudoHost: ALL
    sudoCommand: !/bin/sh
    sudoCommand: ALL

Another difference is that negations on the Host, User or Runas are
currently ignorred.  For example, the following attributes do not
behave the way one might expect.

    # does not match all but joe
    # rather, does not match anyone
    sudoUser: !joe

    # does not match all but joe
    # rather, matches everyone including Joe
    sudoUser: ALL
    sudoUser: !joe

    # does not match all but web01
    # rather, matches all hosts including web01
    sudoHost: ALL
    sudoHost: !web01

=head2 Sudoers Schema

In order to use B<sudo>'s LDAP support, the B<sudo> schema must be
installed on your LDAP server.  In addition, be sure to index the
'sudoUser' attribute.

Three versions of the schema: one for OpenLDAP servers (F<schema.OpenLDAP>),
one for Netscape-derived servers (F<schema.iPlanet>), and one for
Microsoft Active Directory (F<schema.ActiveDirectory>) may
be found in the B<sudo> distribution.

The schema for B<sudo> in OpenLDAP form is included in the L<EXAMPLES>
section.

=head2 Configuring ldap.conf

Sudo reads the F<@ldap_conf@> file for LDAP-specific configuration.
Typically, this file is shared amongst different LDAP-aware clients.
As such, most of the settings are not B<sudo>-specific.  Note that
B<sudo> parses F<@ldap_conf@> itself and may support options
that differ from those described in the L<ldap.conf(5)> manual.

Also note that on systems using the OpenLDAP libraries, default
values specified in F</etc/openldap/ldap.conf> or the user's
F<.ldaprc> files are not used.

Only those options explicitly listed in F<@ldap_conf@> that are
supported by B<sudo> are honored.  Configuration options are listed
below in upper case but are parsed in a case-independent manner.

=over 4

=item B<URI> ldap[s]://[hostname[:port]] ...

Specifies a whitespace-delimited list of one or more URIs describing
the LDAP server(s) to connect to.  The I<protocol> may be either B<ldap>
or B<ldaps>, the latter being for servers that support TLS (SSL)
encryption.  If no I<port> is specified, the default is port 389 for
C<ldap://> or port 636 for C<ldaps://>.  If no I<hostname> is specified,
B<sudo> will connect to B<localhost>.  Only systems using the OpenSSL
libraries support the mixing of C<ldap://> and C<ldaps://> URIs.
The Netscape-derived libraries used on most commercial versions of
Unix are only capable of supporting one or the other.

=item B<HOST> name[:port] ...

If no B<URI> is specified, the B<HOST> parameter specifies a
whitespace-delimited list of LDAP servers to connect to.  Each host
may include an optional I<port> separated by a colon (':').  The
B<HOST> parameter is deprecated in favor of the B<URI> specification
and is included for backwards compatibility.

=item B<PORT> port_number

If no B<URI> is specified, the B<PORT> parameter specifies the
default port to connect to on the LDAP server if a B<HOST> parameter
does not specify the port itself.  If no B<PORT> parameter is used,
the default is port 389 for LDAP and port 636 for LDAP over TLS
(SSL).  The B<PORT> parameter is deprecated in favor of the B<URI>
specification and is included for backwards compatibility.

=item B<BIND_TIMELIMIT> seconds

The B<BIND_TIMELIMIT> parameter specifies the amount of time, in seconds,
to wait while trying to connect to an LDAP server.  If multiple B<URI>s or
B<HOST>s are specified, this is the amount of time to wait before trying
the next one in the list.

=item B<TIMELIMIT> seconds

The B<TIMELIMIT> parameter specifies the amount of time, in seconds,
to wait for a response to an LDAP query.

=item B<SUDOERS_BASE> base

The base DN to use when performing B<sudo> LDAP queries.  Typically
this is of the form C<ou=SUDOers,dc=example,dc=com> for the domain
C<example.com>.

=item B<SUDOERS_DEBUG> debug_level

This sets the debug level for B<sudo> LDAP queries.  Debugging
information is printed to the standard error.  A value of 1 results
in a moderate amount of debugging information.  A value of 2 shows
the results of the matches themselves.  This parameter should not
be set in a production environment as the extra information is
likely to confuse users.

=item B<BINDDN> DN

The B<BINDDN> parameter specifies the identity, in the form of a
Distinguished Name (DN), to use when performing LDAP operations.
If not specified, LDAP operations are performed with an anonymous
identity.  By default, most LDAP servers will allow anonymous access.

=item B<BINDPW> secret

The B<BINDPW> parameter specifies the password to use when performing
LDAP operations.  This is typically used in conjunction with the
B<BINDDN> parameter.

=item B<ROOTBINDDN> DN

The B<ROOTBINDDN> parameter specifies the identity, in the form of
a Distinguished Name (DN), to use when performing privileged LDAP
operations, such as I<sudoers> queries.  The password corresponding
to the identity should be stored in F<@ldap_secret@>.
If not specified, the B<BINDDN> identity is used (if any).

=item B<LDAP_VERSION> number

The version of the LDAP protocol to use when connecting to the server.
The default value is protocol version 3.

=item B<SSL> on/true/yes/off/false/no

If the B<SSL> parameter is set to C<on>, C<true> or C<yes>, TLS
(SSL) encryption is always used when communicating with the LDAP
server.  Typically, this involves connecting to the server on port
636 (ldaps).

=item B<SSL> start_tls

If the B<SSL> parameter is set to C<start_tls>, the LDAP server
connection is initiated normally and TLS encryption is begun before
the bind credentials are sent.  This has the advantage of not
requiring a dedicated port for encrypted communications.  This
parameter is only supported by LDAP servers that honor the C<start_tls>
extension, such as the OpenLDAP server.

=item B<TLS_CHECKPEER> on/true/yes/off/false/no

If enabled, B<TLS_CHECKPEER> will cause the LDAP server's TLS
certificated to be verified.  If the server's TLS certificate cannot
be verified (usually because it is signed by an unknown certificate
authority), B<sudo> will be unable to connect to it.  If B<TLS_CHECKPEER>
is disabled, no check is made.

=item B<TLS_CACERTFILE> file name

The path to a certificate authority bundle which contains the certificates
for all the Certificate Authorities the client knows to be valid,
e.g. F</etc/ssl/ca-bundle.pem>.
This option is only supported by the OpenLDAP libraries.

=item B<TLS_CACERTDIR> directory

Similar to B<TLS_CACERTFILE> but instead of a file, it is a
directory containing individual Certificate Authority certificates,
e.g. F</etc/ssl/certs>.
The directory specified by B<TLS_CACERTDIR> is checked after
B<TLS_CACERTFILE>.
This option is only supported by the OpenLDAP libraries.

=item B<TLS_CERT> file name

The path to a file containing the client certificate which can
be used to authenticate the client to the LDAP server.
The certificate type depends on the LDAP libraries used.

OpenLDAP:
    C<tls_cert /etc/ssl/client_cert.pem>

Netscape-derived:
    C<tls_cert /var/ldap/cert7.db>

When using Netscape-derived libraries, this file may also contain
Certificate Authority certificates.

=item B<TLS_KEY> file name

The path to a file containing the private key which matches the
certificate specified by B<TLS_CERT>.  The private key must not be
password-protected.  The key type depends on the LDAP libraries
used.

OpenLDAP:
    C<tls_key /etc/ssl/client_key.pem>

Netscape-derived:
    C<tls_key /var/ldap/key3.db>

=item B<TLS_RANDFILE> file name

The B<TLS_RANDFILE> parameter specifies the path to an entropy
source for systems that lack a random device.  It is generally used
in conjunction with I<prngd> or I<egd>.
This option is only supported by the OpenLDAP libraries.

=item B<TLS_CIPHERS> cipher list

The B<TLS_CIPHERS> parameter allows the administer to restrict
which encryption algorithms may be used for TLS (SSL) connections.
See the OpenSSL manual for a list of valid ciphers.
This option is only supported by the OpenLDAP libraries.

=item B<USE_SASL> on/true/yes/off/false/no

Enable B<USE_SASL> for LDAP servers that support SASL authentication.

=item B<SASL_AUTH_ID> identity

The SASL user name to use when connecting to the LDAP server.
By default, B<sudo> will use an anonymous connection.

=item B<ROOTUSE_SASL> on/true/yes/off/false/no

Enable B<ROOTUSE_SASL> to enable SASL authentication when connecting
to an LDAP server from a privileged process, such as B<sudo>.

=item B<ROOTSASL_AUTH_ID> identity

The SASL user name to use when B<ROOTUSE_SASL> is enabled.

=item B<SASL_SECPROPS> none/properties

SASL security properties or I<none> for no properties.  See the
SASL programmer's manual for details.

=item B<KRB5_CCNAME> file name

The path to the Kerberos 5 credential cache to use when authenticating
with the remote server.

=back

See the C<ldap.conf> entry in the L<EXAMPLES> section.

=head2 Configuring nsswitch.conf

Unless it is disabled at build time, B<sudo> consults the Name
Service Switch file, F<@nsswitch_conf@>, to specify the I<sudoers>
search order.  Sudo looks for a line beginning with C<sudoers:> and
uses this to determine the search order.  Note that B<sudo> does
not stop searching after the first match and later matches take
precedence over earlier ones.

The following sources are recognized:

    files	read sudoers from F<@sysconfdir@/sudoers>
    ldap	read sudoers from LDAP

In addition, the entry C<[NOTFOUND=return]> will short-circuit the
search if the user was not found in the preceding source.

To consult LDAP first followed by the local sudoers file (if it
exists), use:

    sudoers: ldap files

The local I<sudoers> file can be ignored completely by using:

    sudoers: ldap

If the F<@nsswitch_conf@> file is not present or there is no
sudoers line, the following default is assumed:

    sudoers: files

Note that F<@nsswitch_conf@> is supported even when the underlying
operating system does not use an nsswitch.conf file.

=head1 FILES

=over 24

=item F<@ldap_conf@>

LDAP configuration file

=item F<@nsswitch_conf@>

determines sudoers source order

=back

=head1 EXAMPLES

=head2 Example ldap.conf

  # Either specify one or more URIs or one or more host:port pairs.
  # If neither is specified sudo will default to localhost, port 389.
  #
  #host          ldapserver
  #host          ldapserver1 ldapserver2:390
  #
  # Default port if host is specified without one, defaults to 389.
  #port          389
  #
  # URI will override the host and port settings.
  uri            ldap://ldapserver
  #uri            ldaps://secureldapserver
  #uri            ldaps://secureldapserver ldap://ldapserver
  #
  # The amount of time, in seconds, to wait while trying to connect to
  # an LDAP server.
  bind_timelimit 30
  #
  # The amount of time, in seconds, to wait while performing an LDAP query.
  timelimit 30
  #
  # must be set or sudo will ignore LDAP
  sudoers_base   ou=SUDOers,dc=example,dc=com
  #
  # verbose sudoers matching from ldap
  #sudoers_debug 2
  #
  # optional proxy credentials
  #binddn        <who to search as>
  #bindpw        <password>
  #rootbinddn    <who to search as, uses /etc/ldap.secret for bindpw>
  #
  # LDAP protocol version, defaults to 3
  #ldap_version 3
  #
  # Define if you want to use an encrypted LDAP connection.
  # Typically, you must also set the port to 636 (ldaps).
  #ssl on
  #
  # Define if you want to use port 389 and switch to
  # encryption before the bind credentials are sent.
  # Only supported by LDAP servers that support the start_tls
  # extension such as OpenLDAP.
  #ssl start_tls
  #
  # Additional TLS options follow that allow tweaking of the
  # SSL/TLS connection.
  #
  #tls_checkpeer yes # verify server SSL certificate
  #tls_checkpeer no  # ignore server SSL certificate
  #
  # If you enable tls_checkpeer, specify either tls_cacertfile
  # or tls_cacertdir.  Only supported when using OpenLDAP.
  #
  #tls_cacertfile /etc/certs/trusted_signers.pem
  #tls_cacertdir  /etc/certs
  #
  # For systems that don't have /dev/random
  # use this along with PRNGD or EGD.pl to seed the
  # random number pool to generate cryptographic session keys.
  # Only supported when using OpenLDAP.
  #
  #tls_randfile /etc/egd-pool
  #
  # You may restrict which ciphers are used.  Consult your SSL
  # documentation for which options go here.
  # Only supported when using OpenLDAP.
  #
  #tls_ciphers <cipher-list>
  #
  # Sudo can provide a client certificate when communicating to
  # the LDAP server.
  # Tips:
  #   * Enable both lines at the same time.
  #   * Do not password protect the key file.
  #   * Ensure the keyfile is only readable by root.
  #
  # For OpenLDAP:
  #tls_cert /etc/certs/client_cert.pem
  #tls_key  /etc/certs/client_key.pem
  #
  # For SunONE or iPlanet LDAP, the file specified by tls_cert may
  # contain CA certs and/or the client's cert.  If the client's
  # cert is included, tls_key should be specified as well.
  # For backward compatibility, sslpath may be used in place of tls_cert.
  #tls_cert /var/ldap/cert7.db
  #tls_key /var/ldap/key3.db
  #
  # If using SASL authentication for LDAP (OpenSSL)
  # use_sasl yes
  # sasl_auth_id <SASL username>
  # rootuse_sasl yes
  # rootsasl_auth_id <SASL username for root access>
  # sasl_secprops none
  # krb5_ccname /etc/.ldapcache

=head2 Sudo schema for OpenLDAP 

The following schema is in OpenLDAP format.  Simply copy it to the
schema directory (e.g. F</etc/openldap/schema>), add the proper
C<include> line in C<slapd.conf> and restart B<slapd>.

 attributetype ( 1.3.6.1.4.1.15953.9.1.1
    NAME 'sudoUser'
    DESC 'User(s) who may  run sudo'
    EQUALITY caseExactIA5Match
    SUBSTR caseExactIA5SubstringsMatch
    SYNTAX 1.3.6.1.4.1.1466.115.121.1.26 )

 attributetype ( 1.3.6.1.4.1.15953.9.1.2
    NAME 'sudoHost'
    DESC 'Host(s) who may run sudo'
    EQUALITY caseExactIA5Match
    SUBSTR caseExactIA5SubstringsMatch
    SYNTAX 1.3.6.1.4.1.1466.115.121.1.26 )

 attributetype ( 1.3.6.1.4.1.15953.9.1.3
    NAME 'sudoCommand'
    DESC 'Command(s) to be executed by sudo'
    EQUALITY caseExactIA5Match
    SYNTAX 1.3.6.1.4.1.1466.115.121.1.26 )

 attributetype ( 1.3.6.1.4.1.15953.9.1.4
    NAME 'sudoRunAs'
    DESC 'User(s) impersonated by sudo'
    EQUALITY caseExactIA5Match
    SYNTAX 1.3.6.1.4.1.1466.115.121.1.26 )

 attributetype ( 1.3.6.1.4.1.15953.9.1.5
    NAME 'sudoOption'
    DESC 'Options(s) followed by sudo'
    EQUALITY caseExactIA5Match
    SYNTAX 1.3.6.1.4.1.1466.115.121.1.26 )

 attributetype ( 1.3.6.1.4.1.15953.9.1.6
    NAME 'sudoRunAsUser'
    DESC 'User(s) impersonated by sudo'
    EQUALITY caseExactIA5Match
    SYNTAX 1.3.6.1.4.1.1466.115.121.1.26 )

 attributetype ( 1.3.6.1.4.1.15953.9.1.7
    NAME 'sudoRunAsGroup'
    DESC 'Group(s) impersonated by sudo'
    EQUALITY caseExactIA5Match
    SYNTAX 1.3.6.1.4.1.1466.115.121.1.26 )

 objectclass ( 1.3.6.1.4.1.15953.9.2.1 NAME 'sudoRole' SUP top STRUCTURAL
    DESC 'Sudoer Entries'
    MUST ( cn )
    MAY ( sudoUser $ sudoHost $ sudoCommand $ sudoRunAs $ sudoRunAsUser $
	  sudoRunAsGroup $ sudoOption $ description )
    )

=for comment

Add nsswitch.conf example?
Add more exhaustive sudoers ldif example?

=head1 SEE ALSO

L<ldap.conf(5)>, L<sudoers(5)>

=head1 CAVEATS

The way that I<sudoers> is parsed differs between Note that there
are differences in the way that LDAP-based I<sudoers> is parsed
compared to file-based I<sudoers>.  See the L<Differences between
LDAP and non-LDAP sudoers> section for more information.

=head1 BUGS

If you feel you have found a bug in B<sudo>, please submit a bug report
at http://www.sudo.ws/sudo/bugs/

=head1 SUPPORT

Limited free support is available via the sudo-users mailing list,
see http://www.sudo.ws/mailman/listinfo/sudo-users to subscribe or
search the archives.

=head1 DISCLAIMER

B<sudo> is provided ``AS IS'' and any express or implied warranties,
including, but not limited to, the implied warranties of merchantability
and fitness for a particular purpose are disclaimed.  See the LICENSE
file distributed with B<sudo> or http://www.sudo.ws/sudo/license.html
for complete details.