sudoers.ldap
—
sudo LDAP configuration
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:
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.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
Runas_Aliases. Host netgroups can be used in place of Host_Aliases. 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.
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
attributes:
#
’), Unix group (prefixed with
‘%
’), Unix group ID (prefixed with
‘%#
’), or user netgroup (prefixed
with ‘+
’).+
’). The special value
ALL
will match any host.ALL
will match any command. If a command is
prefixed with an exclamation point
‘!
’, the user will be prohibited
from running that command.sudoRole
in which it resides.#
’) 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.
The sudoRunAsUser
attribute is only
available in sudo
versions 1.7.0 and higher.
Older versions of sudo
use the
sudoRunAs
attribute instead.
#
’) that commands may be run as.
The special value ALL
will match any group.
The sudoRunAsGroup
attribute is only
available in sudo
versions 1.7.0 and higher.
yyyymmddHHMMSSZ
that can
be used to provide a start date/time for when the
sudoRole
will be valid. If multiple
sudoNotBefore
entries are present, the earliest is
used. Note that timestamps must be in Coordinated Universal Time (UTC),
not the local timezone. The minute and seconds portions are optional, but
some LDAP servers require that they be present (contrary to the RFC).
The sudoNotBefore
attribute is only
available in sudo
versions 1.7.5 and higher and
must be explicitly enabled via the SUDOERS_TIMED
option in /etc/ldap.conf.
yyyymmddHHMMSSZ
that
indicates an expiration date/time, after which the
sudoRole
will no longer be valid. If multiple
sudoNotBefore
entries are present, the last one is
used. Note that timestamps must be in Coordinated Universal Time (UTC),
not the local timezone. The minute and seconds portions are optional, but
some LDAP servers require that they be present (contrary to the RFC).
The sudoNotAfter
attribute is only
available in sudo
versions 1.7.5 and higher and
must be explicitly enabled via the SUDOERS_TIMED
option in /etc/ldap.conf.
sudoRole
entries retrieved from the LDAP
directory have no inherent order. The sudoOrder
attribute is an integer (or floating point value for LDAP servers that
support it) that is used to sort the matching entries. This allows
LDAP-based sudoers entries to more closely mimic the behaviour of the
sudoers file, where the of the entries influences the result. If multiple
entries match, the entry with the highest
sudoOrder
attribute is chosen. This corresponds to
the “last match” behavior of the sudoers file. If the
sudoOrder
attribute is not present, a value of 0
is assumed.
The sudoOrder
attribute is only
available in sudo
versions 1.7.5 and higher.
Each attribute listed above should contain a single value, but
there may be multiple instances of each attribute 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
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.
If timed entries are enabled with the SUDOERS_TIMED configuration directive, the LDAP queries include a subfilter that limits retrieval to entries that satisfy the time constraints, if any.
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.
The order in which different entries are applied can be controlled
using the sudoOrder
attribute, but there is no way
to guarantee the order of attributes within a specific entry. If there are
conflicting command rules in 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 ignored. 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
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
also included in the EXAMPLES
section.
Sudo reads the /etc/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/ldap.conf
itself and may support options that differ from those described in the
system's ldap.conf(8) 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/ldap.conf as being supported by
sudo
are honored. Configuration options are listed
below in upper case but are parsed in a case-independent manner.
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.
Both the Netscape-derived and Tivoli LDAP libraries used on most
commercial versions of Unix are only capable of supporting one or the
other.:
’). The
HOST parameter is deprecated in favor of the
URI specification and is included for backwards
compatibility.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.sudo
LDAP query. Typically, this is
of the form attribute=value
or
(&(attribute=value)(attribute2=value2))
.sudoNotBefore
and
sudoNotAfter
attributes that implement
time-dependent sudoers entries.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.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).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 and Tivoli Directory servers.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. This option is not supported by the Tivoli Directory Server LDAP
libraries.tls_cert
/etc/ssl/client_cert.pem
tls_cert
/var/ldap/cert7.db
When using Netscape-derived libraries, this file may also contain Certificate Authority certificates.
tls_key
/etc/ssl/client_key.pem
tls_key
/var/ldap/key3.db
tls_cert
/usr/ldap/ldapkey.kdb
.sth
file extension instead of
.kdb
, e.g. ldapkey.sth
.
The default ldapkey.kdb
that ships with Tivoli
Directory Server is encrypted with the password
ssl_password
. This option is only supported by the
Tivoli LDAP libraries.sudo
will use an anonymous connection.sudo
.See the ldap.conf entry in the EXAMPLES section.
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:
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, except on AIX (see below).
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
# 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 # # Enable support for time-based entries in sudoers. #sudoers_timed yes # # 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
The following schema, in OpenLDAP format, is included with
sudo
source and binary distributions as
schema.OpenLDAP. 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 ) attributetype ( 1.3.6.1.4.1.15953.9.1.8 NAME 'sudoNotBefore' DESC 'Start of time interval for which the entry is valid' EQUALITY generalizedTimeMatch ORDERING generalizedTimeOrderingMatch SYNTAX 1.3.6.1.4.1.1466.115.121.1.24 ) attributetype ( 1.3.6.1.4.1.15953.9.1.9 NAME 'sudoNotAfter' DESC 'End of time interval for which the entry is valid' EQUALITY generalizedTimeMatch ORDERING generalizedTimeOrderingMatch SYNTAX 1.3.6.1.4.1.1466.115.121.1.24 ) attributeTypes ( 1.3.6.1.4.1.15953.9.1.10 NAME 'sudoOrder' DESC 'an integer to order the sudoRole entries' EQUALITY integerMatch ORDERING integerOrderingMatch SYNTAX 1.3.6.1.4.1.1466.115.121.1.27 ) 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 $ sudoNotBefore $ sudoNotAfter $ sudoOrder $ description ) )
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.
If you feel you have found a bug in sudo
,
please submit a bug report at https://www.sudo.ws/sudo/bugs/
Limited free support is available via the sudo-users mailing list, see https://www.sudo.ws/mailman/listinfo/sudo-users to subscribe or search the archives.
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 https://www.sudo.ws/sudo/license.html for
complete details.