SUDOERS.LDAPSection: MAINTENANCE COMMANDS (5)
Updated: July 12, 2010
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NAMEsudoers.ldap - sudo LDAP configuration
DESCRIPTIONIn 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:
- 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.
- 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.
- 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.
- 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 containerThe sudoers configuration is contained in the ou=SUDOers
Sudo first looks for the
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
. It consists of the following components:
- A user name, uid (prefixed with '#'), Unix group (prefixed with a '%') or user netgroup (prefixed with a '+').
A host name, IP address, IP network, or host netgroup (prefixed
with a '+').
The special value
will match any host.
A Unix command with optional command line arguments, potentially
including globbing characters (aka wild cards).
The special value
will match any command. If a command is prefixed with an exclamation point '!', the user will be prohibited from running that command.
Identical in function to the global options described above, but
specific to the
in which it resides.
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
The special value
will match any user.
A Unix group or gid (prefixed with '#') that commands may be run as.
The special value
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
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 lookupWhen 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 sudoersThere 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 SchemaIn 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.
Configuring ldap.confSudo reads the /etc/sudo-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/sudo-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/sudo-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
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://
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
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/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
, 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
, 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.
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
- 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.
Configuring nsswitch.confUnless 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
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:
If the /etc/nsswitch.conf file is not present or there is no sudoers line, the following default is assumed:
Configuring netsvc.confOn 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
qualfier only affects user lookups; both LDAP and sudoers will be queried for Defaults
If the /etc/netsvc.conf file is not present or there is no sudoers line, the following default is assumed:
sudoers = files
- LDAP configuration file
- determines sudoers source order
- determines sudoers source order on AIX
# 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 OpenLDAPThe 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 ( 184.108.40.206.4.1.159220.127.116.11 NAME 'sudoUser' DESC 'User(s) who may run sudo' EQUALITY caseExactIA5Match SUBSTR caseExactIA5SubstringsMatch SYNTAX 18.104.22.168.4.1.1422.214.171.124.26 ) attributetype ( 126.96.36.199.4.1.159188.8.131.52 NAME 'sudoHost' DESC 'Host(s) who may run sudo' EQUALITY caseExactIA5Match SUBSTR caseExactIA5SubstringsMatch SYNTAX 184.108.40.206.4.1.14220.127.116.11.26 ) attributetype ( 18.104.22.168.4.1.15922.214.171.124 NAME 'sudoCommand' DESC 'Command(s) to be executed by sudo' EQUALITY caseExactIA5Match SYNTAX 126.96.36.199.4.1.14188.8.131.52.26 ) attributetype ( 184.108.40.206.4.1.159220.127.116.11 NAME 'sudoRunAs' DESC 'User(s) impersonated by sudo' EQUALITY caseExactIA5Match SYNTAX 18.104.22.168.4.1.1422.214.171.124.26 ) attributetype ( 126.96.36.199.4.1.159188.8.131.52 NAME 'sudoOption' DESC 'Options(s) followed by sudo' EQUALITY caseExactIA5Match SYNTAX 184.108.40.206.4.1.14220.127.116.11.26 ) attributetype ( 18.104.22.168.4.1.15922.214.171.124 NAME 'sudoRunAsUser' DESC 'User(s) impersonated by sudo' EQUALITY caseExactIA5Match SYNTAX 126.96.36.199.4.1.14188.8.131.52.26 ) attributetype ( 184.108.40.206.4.1.159220.127.116.11 NAME 'sudoRunAsGroup' DESC 'Group(s) impersonated by sudo' EQUALITY caseExactIA5Match SYNTAX 18.104.22.168.4.1.1422.214.171.124.26 ) objectclass ( 126.96.36.199.4.1.159188.8.131.52 NAME 'sudoRole' SUP top STRUCTURAL DESC 'Sudoer Entries' MUST ( cn ) MAY ( sudoUser $ sudoHost $ sudoCommand $ sudoRunAs $ sudoRunAsUser $ sudoRunAsGroup $ sudoOption $ description ) )
SEE ALSOldap.conf(5), sudoers(5)
CAVEATSThe 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.
BUGSIf you feel you have found a bug in sudo, please submit a bug report at http://www.sudo.ws/sudo/bugs/
SUPPORTLimited 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.
DISCLAIMERsudo 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.
- SEE ALSO
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Time: 05:34:00 GMT, December 24, 2015