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SUDOERS.LDAP(5) MAINTENANCE COMMANDS SUDOERS.LDAP(5)
NAME
sudoers.ldap - sudo LDAP configuration
DESCRIPTION
In addition to the standard sudoers file, sudo may be configured via LDAP. This can be especially useful for
synchronizing sudoers in a large, distributed environment.
Using LDAP for sudoers has several benefits:
o sudo no longer needs to read 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.
o sudo no longer exits if there is a typo in 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 sudo from running.
o It is possible to specify per-entry options that override the global default options. /etc/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.
o The visudo program is no longer needed. visudo provides locking and syntax checking of the /etc/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.
Another major difference between LDAP and file-based sudoers is that in LDAP, sudo-specific Aliases are not supported.
For the most part, there is really no need for 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 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.
SUDOers LDAP container
The sudoers configuration is contained in the ou=SUDOers LDAP container.
Sudo first looks for the cn=default entry in the SUDOers container. If found, the multi-valued sudoOption attribute is
parsed in the same manner as a global Defaults line in /etc/sudoers. In the following example, the 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 sudoRole. It consists of the following components:
sudoUser
A user name, uid (prefixed with '#'), Unix group (prefixed with a '%') or user netgroup (prefixed with a '+').
sudoHost
A host name, IP address, IP network, or host netgroup (prefixed with a '+'). The special value ALL will match any
host.
sudoCommand
A Unix command with optional command line arguments, potentially including globbing characters (aka wild cards). The
special value ALL will match any command. If a command is prefixed with an exclamation point '!', the user will be
prohibited from running that command.
sudoOption
Identical in function to the global options described above, but specific to the sudoRole in which it resides.
sudoRunAsUser
A user name or uid (prefixed with '#') that commands may be run as or a Unix group (prefixed with a '%') or user
netgroup (prefixed with a '+') that contains a list of users that commands may be run as. The special value ALL will
match any user.
sudoRunAsGroup
A Unix group or gid (prefixed with '#') that commands may be run as. The special value ALL will match any group.
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 sudoUser, sudoHost and sudoCommand.
The following example allows users in group wheel to run any command on any host via sudo:
dn: cn=%wheel,ou=SUDOers,dc=example,dc=com
objectClass: top
objectClass: sudoRole
cn: %wheel
sudoUser: %wheel
sudoHost: ALL
sudoCommand: ALL
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.
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
Sudoers Schema
In order to use sudo's LDAP support, the 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 (schema.OpenLDAP), one for Netscape-derived servers
(schema.iPlanet), and one for Microsoft Active Directory (schema.ActiveDirectory) may be found in the sudo distribution.
The schema for sudo in OpenLDAP form is included in the EXAMPLES section.
Configuring ldap.conf
Sudo reads the /etc/nss_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 sudo-specific. Note that sudo parses /etc/nss_ldap.conf
itself and may support options that differ from those described in the ldap.conf(5) manual.
Also note that on systems using the OpenLDAP libraries, default values specified in /etc/openldap/ldap.conf or the user's
.ldaprc files are not used.
Only those options explicitly listed in /etc/nss_ldap.conf that are supported by sudo are honored. Configuration options
are listed below in upper case but are parsed in a case-independent manner.
URI ldap[s]://[hostname[:port]] ...
Specifies a whitespace-delimited list of one or more URIs describing the LDAP server(s) to connect to. The protocol
may be either ldap or ldaps, the latter being for servers that support TLS (SSL) encryption. If no port is
specified, the default is port 389 for ldap:// or port 636 for ldaps://. If no hostname is specified, sudo will
connect to localhost. Multiple URI lines are treated identically to a URI line containing multiple entries. Only
systems using the OpenSSL libraries support the mixing of ldap:// and ldaps:// URIs. The Netscape-derived libraries
used on most commercial versions of Unix are only capable of supporting one or the other.
HOST name[:port] ...
If no URI is specified, the HOST parameter specifies a whitespace-delimited list of LDAP servers to connect to. Each
host may include an optional port separated by a colon (':'). The HOST parameter is deprecated in favor of the URI
specification and is included for backwards compatibility.
PORT port_number
If no URI is specified, the PORT parameter specifies the default port to connect to on the LDAP server if a HOST
parameter does not specify the port itself. If no PORT parameter is used, the default is port 389 for LDAP and port
636 for LDAP over TLS (SSL). The PORT parameter is deprecated in favor of the URI specification and is included for
backwards compatibility.
BIND_TIMELIMIT seconds
The BIND_TIMELIMIT parameter specifies the amount of time, in seconds, to wait while trying to connect to an LDAP
server. If multiple URIs or HOSTs are specified, this is the amount of time to wait before trying the next one in
the list.
TIMELIMIT seconds
The TIMELIMIT parameter specifies the amount of time, in seconds, to wait for a response to an LDAP query.
SUDOERS_BASE base
The base DN to use when performing sudo LDAP queries. Typically this is of the form ou=SUDOers,dc=example,dc=com for
the domain example.com. Multiple SUDOERS_BASE lines may be specified, in which case they are queried in the order
specified.
SUDOERS_DEBUG debug_level
This sets the debug level for 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.
BINDDN DN
The 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.
BINDPW secret
The BINDPW parameter specifies the password to use when performing LDAP operations. This is typically used in
conjunction with the BINDDN parameter.
ROOTBINDDN DN
The ROOTBINDDN parameter specifies the identity, in the form of a Distinguished Name (DN), to use when performing
privileged LDAP operations, such as sudoers queries. The password corresponding to the identity should be stored in
/etc/nss_ldap.secret. If not specified, the BINDDN identity is used (if any).
LDAP_VERSION number
The version of the LDAP protocol to use when connecting to the server. The default value is protocol version 3.
SSL on/true/yes/off/false/no
If the SSL parameter is set to on, true or yes, TLS (SSL) encryption is always used when communicating with the LDAP
server. Typically, this involves connecting to the server on port 636 (ldaps).
SSL start_tls
If the SSL parameter is set to 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 start_tls extension, such as the
OpenLDAP server.
TLS_CHECKPEER on/true/yes/off/false/no
If enabled, 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), sudo will be
unable to connect to it. If TLS_CHECKPEER is disabled, no check is made. Note that disabling the check creates an
opportunity for man-in-the-middle attacks since the server's identity will not be authenticated. If possible, the
CA's certificate should be installed locally so it can be verified.
TLS_CACERT file name
An alias for TLS_CACERTFILE.
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. /etc/ssl/ca-bundle.pem. This option is only supported by the OpenLDAP libraries.
Netscape-derived LDAP libraries use the same certificate database for CA and client certificates (see TLS_CERT).
TLS_CACERTDIR directory
Similar to TLS_CACERTFILE but instead of a file, it is a directory containing individual Certificate Authority
certificates, e.g. /etc/ssl/certs. The directory specified by TLS_CACERTDIR is checked after TLS_CACERTFILE. This
option is only supported by the OpenLDAP libraries.
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:
tls_cert /etc/ssl/client_cert.pem
Netscape-derived:
tls_cert /var/ldap/cert7.db
When using Netscape-derived libraries, this file may also contain Certificate Authority certificates.
TLS_KEY file name
The path to a file containing the private key which matches the certificate specified by TLS_CERT. The private key
must not be password-protected. The key type depends on the LDAP libraries used.
OpenLDAP:
tls_key /etc/ssl/client_key.pem
Netscape-derived:
tls_key /var/ldap/key3.db
TLS_RANDFILE file name
The TLS_RANDFILE parameter specifies the path to an entropy source for systems that lack a random device. It is
generally used in conjunction with prngd or egd. This option is only supported by the OpenLDAP libraries.
TLS_CIPHERS cipher list
The 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.
USE_SASL on/true/yes/off/false/no
Enable USE_SASL for LDAP servers that support SASL authentication.
SASL_AUTH_ID identity
The SASL user name to use when connecting to the LDAP server. By default, sudo will use an anonymous connection.
ROOTUSE_SASL on/true/yes/off/false/no
Enable ROOTUSE_SASL to enable SASL authentication when connecting to an LDAP server from a privileged process, such
as sudo.
ROOTSASL_AUTH_ID identity
The SASL user name to use when ROOTUSE_SASL is enabled.
SASL_SECPROPS none/properties
SASL security properties or none for no properties. See the SASL programmer's manual for details.
KRB5_CCNAME file name
The path to the Kerberos 5 credential cache to use when authenticating with the remote server.
See the ldap.conf entry in the EXAMPLES section.
Configuring nsswitch.conf
Unless it is disabled at build time, sudo consults the Name Service Switch file, /etc/nsswitch.conf, to specify the
sudoers search order. Sudo looks for a line beginning with sudoers: and uses this to determine the search order. Note
that 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</etc/sudoers>
ldap read sudoers from LDAP
In addition, the entry [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 sudoers file can be ignored completely by using:
sudoers: ldap
If the /etc/nsswitch.conf file is not present or there is no sudoers line, the following default is assumed:
sudoers: files
Note that /etc/nsswitch.conf is supported even when the underlying operating system does not use an nsswitch.conf file.
Configuring netsvc.conf
On AIX systems, the /etc/netsvc.conf file is consulted instead of /etc/nsswitch.conf. sudo simply treats netsvc.conf as
a variant of nsswitch.conf; information in the previous section unrelated to the file format itself still applies.
To consult LDAP first followed by the local sudoers file (if it exists), use:
sudoers = ldap, files
The local sudoers file can be ignored completely by using:
sudoers = ldap
To treat LDAP as authoratative and only use the local sudoers file if the user is not present in LDAP, use:
sudoers = ldap = auth, files
Note that in the above example, the auth qualfier only affects user lookups; both LDAP and sudoers will be queried for
Defaults entries.
If the /etc/netsvc.conf file is not present or there is no sudoers line, the following default is assumed:
sudoers = files
FILES
/etc/nss_ldap.conf LDAP configuration file
/etc/nsswitch.conf determines sudoers source order
/etc/netsvc.conf determines sudoers source order on AIX
EXAMPLES
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; may be specified multiple times.
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, tls_cert and tls_key may specify either
# a directory, in which case the files in the directory must have the
# default names (e.g. cert8.db and key4.db), or the path to the cert
# and key files themselves. However, a bug in version 5.0 of the LDAP
# SDK will prevent specific file names from working. For this reason
# it is suggested that tls_cert and tls_key be set to a directory,
# not a file name.
#
# The certificate database 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
#tls_key /var/ldap
#
# If using SASL authentication for LDAP (OpenSSL)
# use_sasl yes
# sasl_auth_id <SASL user name>
# rootuse_sasl yes
# rootsasl_auth_id <SASL user name for root access>
# sasl_secprops none
# krb5_ccname /etc/.ldapcache
Sudo schema for OpenLDAP
The following schema is in OpenLDAP format. Simply copy it to the schema directory (e.g. /etc/openldap/schema), add the
proper include line in slapd.conf and restart 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 )
)
SEE ALSO
ldap.conf(5), sudoers(5)
CAVEATS
The way that sudoers is parsed differs between Note that there are differences in the way that LDAP-based sudoers is
parsed compared to file-based sudoers. See the "Differences between LDAP and non-LDAP sudoers" section for more
information.
BUGS
If you feel you have found a bug in sudo, please submit a bug report at http://www.sudo.ws/sudo/bugs/
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.
DISCLAIMER
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 sudo or
http://www.sudo.ws/sudo/license.html for complete details.
1.7.4 July 12, 2010 SUDOERS.LDAP(5)
