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 ( 188.8.131.52.4.1.159184.108.40.206 NAME 'sudoUser' DESC 'User(s) who may run sudo' EQUALITY caseExactIA5Match SUBSTR caseExactIA5SubstringsMatch SYNTAX 220.127.116.11.4.1.1418.104.22.168.26 ) attributetype ( 22.214.171.124.4.1.159126.96.36.199 NAME 'sudoHost' DESC 'Host(s) who may run sudo' EQUALITY caseExactIA5Match SUBSTR caseExactIA5SubstringsMatch SYNTAX 188.8.131.52.4.1.14184.108.40.206.26 ) attributetype ( 220.127.116.11.4.1.15918.104.22.168 NAME 'sudoCommand' DESC 'Command(s) to be executed by sudo' EQUALITY caseExactIA5Match SYNTAX 22.214.171.124.4.1.14126.96.36.199.26 ) attributetype ( 188.8.131.52.4.1.159184.108.40.206 NAME 'sudoRunAs' DESC 'User(s) impersonated by sudo' EQUALITY caseExactIA5Match SYNTAX 220.127.116.11.4.1.1418.104.22.168.26 ) attributetype ( 22.214.171.124.4.1.159126.96.36.199 NAME 'sudoOption' DESC 'Options(s) followed by sudo' EQUALITY caseExactIA5Match SYNTAX 188.8.131.52.4.1.14184.108.40.206.26 ) attributetype ( 220.127.116.11.4.1.15918.104.22.168 NAME 'sudoRunAsUser' DESC 'User(s) impersonated by sudo' EQUALITY caseExactIA5Match SYNTAX 22.214.171.124.4.1.14126.96.36.199.26 ) attributetype ( 188.8.131.52.4.1.159184.108.40.206 NAME 'sudoRunAsGroup' DESC 'Group(s) impersonated by sudo' EQUALITY caseExactIA5Match SYNTAX 220.127.116.11.4.1.1418.104.22.168.26 ) objectclass ( 22.214.171.124.4.1.159126.96.36.199 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.