SUDOers LDAP container¶

The sudoers configuration is contained in the ‘ou=SUDOers’ LDAP container.

Sudo first looks for the ‘cn=defaults’ entry in the SUDOers container. If found, the multi-valued sudoOption attribute is parsed in the same manner as a global Defaults line in /usr/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=my-domain,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:

sudoUser

A user name, user-ID (prefixed with ‘#’), Unix group name or ID (prefixed with ‘%’ or ‘%#’ respectively), user netgroup (prefixed with ‘+’), or non-Unix group name or ID (prefixed with ‘%:’ or ‘%:#’ respectively). User netgroups are matched using the user and domain members only; the host member is not used when matching. Non-Unix group support is only available when an appropriate group_plugin is defined in the global defaults sudoRole object. If a sudoUser entry is preceded by an exclamation point, ‘!’, and the entry matches, the sudoRole in which it resides will be ignored. Negated sudoUser entries are only supported by version 1.9.9 or higher.

sudoHost

A host name, IP address, IP network, or host netgroup (prefixed with a ‘+’). The special value ALL will match any host. Host netgroups are matched using the host (both qualified and unqualified) and domain members only; the user member is not used when matching. If a sudoHost entry is preceded by an exclamation point, ‘!’, and the entry matches, the sudoRole in which it resides will be ignored. Negated sudoHost entries are only supported by version 1.8.18 or higher.

sudoCommand

A fully-qualified Unix command name with optional command line arguments, potentially including globbing characters (aka wild cards). If a command name is preceded by an exclamation point, ‘!’, the user will be prohibited from running that command.

The built-in command “sudoedit” is used to permit a user to run sudo with the -e option (or as sudoedit). It may take command line arguments just as a normal command does. Unlike other commands, “sudoedit” is a built into sudo itself and must be specified in without a leading path.

The special value ALL will match any command.

If a command name is prefixed with a SHA-2 digest, it will only be allowed if the digest matches. This may be useful in situations where the user invoking sudo has write access to the command or its parent directory. The following digest formats are supported: sha224, sha256, sha384, and sha512. The digest name must be followed by a colon (‘:’) and then the actual digest, in either hex or base64 format. For example, given the following value for sudoCommand:

sha224:0GomF8mNN3wlDt1HD9XldjJ3SNgpFdbjO1+NsQ /bin/ls

The user may only run /bin/ls if its sha224 digest matches the specified value. Command digests are only supported by version 1.8.7 or higher.

sudoOption

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

sudoRunAsUser

A user name or user-ID (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. If a sudoRunAsUser entry is preceded by an exclamation point, ‘!’, and the entry matches, the sudoRole in which it resides will be ignored. If sudoRunAsUser is specified but empty, it will match the invoking user. If neither sudoRunAsUser nor sudoRunAsGroup are present, the value of the runas_default sudoOption is used (defaults to root).

The sudoRunAsUser attribute is only available in sudo versions 1.7.0 and higher. Older versions of sudo use the sudoRunAs attribute instead. Negated sudoRunAsUser entries are only supported by version 1.8.26 or higher.

sudoRunAsGroup

A Unix group or group-ID (prefixed with ‘#’) that commands may be run as. The special value ALL will match any group. If a sudoRunAsGroup entry is preceded by an exclamation point, ‘!’, and the entry matches, the sudoRole in which it resides will be ignored.

The sudoRunAsGroup attribute is only available in sudo versions 1.7.0 and higher. Negated sudoRunAsGroup entries are only supported by version 1.8.26 or higher.

sudoNotBefore

A timestamp in the form ‘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. 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.

sudoNotAfter

A timestamp in the form ‘yyyymmddHHMMSSZ’ that indicates an expiration date/time, after which the sudoRole will no longer be valid. If multiple sudoNotAfter entries are present, the last one is used. 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.

sudoOrder

The 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 behavior of the sudoers file, where the order 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=my-domain,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 other non-Unix groups and checks to see if the user belongs to any of them.

If timed entries are enabled with the SUDOERS_TIMED parameter, the LDAP queries include a sub-filter that limits retrieval to entries that satisfy the time constraints, if any.

If the NETGROUP_BASE parameter is present and NETGROUP_QUERY has not been disabled (see Configuring ldap.conf below), queries are performed to determine the list of netgroups the user belongs to before the sudoers query. This makes it possible to include netgroups in the sudoers query string in the same manner as Unix groups. The third query mentioned above is not performed unless a group provider plugin is also configured. The actual LDAP queries performed by sudo are as follows:

1. Match all nisNetgroup records with a nisNetgroupTriple containing the user, host, and NIS domain. The query will match nisNetgroupTriple entries with either the short or long form of the host name or no host name specified in the tuple. If the NIS domain is set, the query will match only match entries that include the domain or for which there is no domain present. If the NIS domain is not set, a wildcard is used to match any domain name but be aware that the NIS schema used by some LDAP servers may not support wild cards for nisNetgroupTriple.
2. Repeated queries are performed to find any nested nisNetgroup records with a memberNisNetgroup entry that refers to an already-matched record.

For sites with a large number of netgroups, using NETGROUP_BASE can significantly speed up sudo's execution time as long as the LDAP server supports querying the nisNetgroup object by its nisNetgroupTriple attribute.

Differences between LDAP and non-LDAP sudoers¶

One of the major differences between LDAP and file-based sudoers is that in LDAP, sudo-specific Aliases are not supported.

For the most part, there is little need for sudo-specific Aliases. Unix groups, non-Unix groups (via the group_plugin), 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 groups and netgroups can also be stored in LDAP there is no real need for sudo-specific aliases.

There are also 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

Converting between file-based and LDAP sudoers¶

The cvtsudoers(1) utility can be used to convert between file-based and LDAP sudoers. However, there are features in the file-based sudoers that have no equivalent in LDAP-based sudoers (and vice versa). These cannot be converted automatically.

For example, a Cmnd_Alias in a sudoers file may be converted to a sudoRole that contains multiple commands. Multiple users and/or groups may be assigned to the sudoRole.

Also, host, user, runas, and command-based Defaults entries are not supported. However, a sudoRole may contain one or more sudoOption attributes which can often serve the same purpose.

Consider the following sudoers lines:

Cmnd_Alias PAGERS = /usr/bin/more, /usr/bin/pg, /usr/bin/less
Defaults!PAGERS noexec
alice, bob ALL = ALL

In this example, alice and bob are allowed to run all commands, but the commands listed in PAGERS will have the noexec flag set, preventing shell escapes.

When converting this to LDAP, two sudoRole objects can be used:

dn: cn=PAGERS,ou=SUDOers,dc=my-domain,dc=com
objectClass: top
objectClass: sudoRole
cn: PAGERS
sudoUser: alice
sudoUser: bob
sudoHost: ALL
sudoCommand: /usr/bin/more
sudoCommand: /usr/bin/pg
sudoCommand: /usr/bin/less
sudoOption: noexec
sudoOrder: 900

dn: cn=ADMINS,ou=SUDOers,dc=my-domain,dc=com
objectClass: top
objectClass: sudoRole
cn: ADMINS
sudoUser: alice
sudoUser: bob
sudoHost: ALL
sudoCommand: ALL
sudoOrder: 100

In the LDAP version, the sudoOrder attribute is used to guarantee that the PAGERS sudoRole with noexec has precedence. Unlike the sudoers version, the LDAP version requires that all users for whom the restriction should apply be assigned to the PAGERS sudoRole. Using a Unix group or netgroup in PAGERS rather than listing each user would make this easier to maintain.

Per-user Defaults entries can be emulated by using one or more sudoOption attributes in a sudoRole. Consider the following sudoers lines:

User_Alias ADMINS = john, sally
Defaults:ADMINS !authenticate
ADMINS ALL = (ALL:ALL) ALL

In this example, john and sally are allowed to run any command as any user or group.

When converting this to LDAP, we can use a Unix group instead of the User_Alias.

dn: cn=admins,ou=SUDOers,dc=my-domain,dc=com
objectClass: top
objectClass: sudoRole
cn: admins
sudoUser: %admin
sudoHost: ALL
sudoRunAsUser: ALL
sudoRunAsGroup: ALL
sudoCommand: ALL
sudoOption: !authenticate

This assumes that users john and sally are members of the “admins” Unix group.

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.

The sudo distribution includes versions of the sudoers schema for multiple LDAP servers:

schema.OpenLDAP

OpenLDAP slapd and OpenBSD ldapd

schema.olcSudo

OpenLDAP slapd 2.3 and higher when on-line configuration is enabled

schema.iPlanet

Netscape-derived servers such as the iPlanet, Oracle, and 389 Directory Servers

schema.ActiveDirectory

Microsoft Active Directory

The schema in OpenLDAP format is also included in the EXAMPLES section.

Configuring ldap.conf¶

Sudo reads the /etc/ldap.conf file for LDAP-specific configuration. Typically, this file is shared between different LDAP-aware clients. As such, most of the settings are not sudo-specific. The /etc/ldap.conf file is parsed by sudo itself and may support options that differ from those described in the system's ldap.conf(5) manual. The path to ldap.conf may be overridden via the ldap_conf plugin argument in sudo.conf(5).

On systems using the OpenLDAP libraries, default values specified in /etc/openldap/ldap.conf or the user's .ldaprc files are not used.

sudo supports a variety of LDAP library implementations, including OpenLDAP, Netscape-derived (also used by Solaris and HP-UX), and IBM LDAP (aka Tivoli). Some options are specific to certain LDAP implementations or have implementation-specific behavior. These differences are noted below where applicable.

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.

Lines beginning with a pound sign (‘#’) are ignored. Leading white space is removed from the beginning of lines.

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.

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. The secret may be a plaintext password or a base64-encoded string with a “base64:” prefix. For example:

BINDPW base64:dGVzdA==

If a plaintext password is used, it should be a simple string without quotes. Plain text passwords may not include the comment character (‘#’) and the escaping of special characters with a backslash (‘\’) is not supported.

DEREF never/searching/finding/always

How alias dereferencing is to be performed when searching. See the ldap.conf(5) manual for a full description of this option.

HOST name[:port] ...

If no URI is specified (see below), the HOST parameter specifies a white space-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 backward compatibility only.

KRB5_CCNAME file name

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

This option is only relevant when using SASL authentication (see below).

LDAP_VERSION number

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

NETGROUP_BASE base

The base DN to use when performing LDAP netgroup queries. Typically this is of the form ‘ou=netgroup,dc=my-domain,dc=com’ for the domain my-domain.com. Multiple NETGROUP_BASE lines may be specified, in which case they are queried in the order specified.

When this option is enabled, sudo will query the LDAP server directly when matching netgroups present in a sudoRole instead of relying on the C library's innetgr() function.

Additionally, if the NETGROUP_QUERY parameter (which is enabled by default) has not been disabled, the user's netgroups will be queried directly via LDAP for use in the main sudoers query. This is usually faster than fetching every sudoRole object containing a sudoUser that begins with a ‘+’ prefix and checking whether the user is a member of each one. The NIS schema used by some LDAP servers needs a modification to support querying the nisNetgroup object by its nisNetgroupTriple attribute. For example, OpenLDAP's slapd requires the following change to the nisNetgroupTriple attribute:

attributetype ( 1.3.6.1.1.1.1.14 NAME 'nisNetgroupTriple'
   DESC 'Netgroup triple'
   EQUALITY caseIgnoreIA5Match
   SUBSTR caseIgnoreIA5SubstringsMatch
   SYNTAX 1.3.6.1.4.1.1466.115.121.1.26 )

Before enabling NETGROUP_BASE, you should verify that your LDAP server supports matching nisNetgroupTriple. For example, using ldapsearch:

$ ldapsearch -b $NETGROUP_BASE \
  '(&(objectClass=nisNetgroup)(nisNetgroupTriple=\28*,USER,\29))'

where your nisNetgroup data includes an object with the following nisNetgroupTriple:

nisNetgroupTriple: (,USER,)

NETGROUP_QUERY on/true/yes/off/false/no

The NETGROUP_QUERY parameter indicates whether or not the LDAP server supports querying nisNetgroup objects by matching on nisNetgroupTriple attributes. By default, sudoers expects to be able to perform queries that match on nisNetgroupTriple attributes when NETGROUP_BASE is set, but not all LDAP servers support this.

If NETGROUP_QUERY is disabled, sudoers will not attempt to determine the list of netgroups the user belongs to, but will still use NETGROUP_BASE directly when matching netgroups. This can be used to support netgroups on systems that lack the innetgr() C library function. See the description of the NETGROUP_BASE parameter for more information.

NETGROUP_SEARCH_FILTER ldap_filter

An LDAP filter which is used to restrict the set of records returned when performing an LDAP netgroup query. Typically, this is of the form ‘attribute=value’ or ‘(&(attribute=value)(attribute2=value2))’. The default search filter is: ‘objectClass=nisNetgroup’. If ldap_filter is omitted, no search filter will be used.

This option is only used when querying netgroups directly via LDAP.

NETWORK_TIMEOUT seconds

An alias for BIND_TIMELIMIT provided for OpenLDAP 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 backward compatibility only.

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 the or the path specified by the ldap_secret plugin argument in sudo.conf(5), which defaults to /etc/ldap.secret. If no ROOTBINDDN is specified, the BINDDN identity is used (if any).

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.

SASL_AUTH_ID identity

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

This option is only relevant when using SASL authentication.

SASL_MECH mechanisms

A white space-delimited list of SASL authentication mechanisms to use. By default, sudo will use GSSAPI authentication.

SASL_SECPROPS none/properties

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

This option is only relevant when using SASL authentication.

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 and IBM Tivoli Directory servers.

SUDOERS_BASE base

The base DN to use when performing sudo LDAP queries. Typically this is of the form ‘ou=SUDOers,dc=my-domain,dc=com’ for the domain my-domain.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.

The SUDOERS_DEBUG parameter is deprecated and will be removed in a future release. The same information is now logged via the sudo debugging framework using the “ldap” subsystem at priorities diag and info for debug_level values 1 and 2 respectively. See the sudo.conf(5) manual for details on how to configure sudo debugging.

SUDOERS_SEARCH_FILTER ldap_filter

An LDAP filter which is used to restrict the set of records returned when performing a sudo LDAP query. Typically, this is of the form ‘attribute=value’ or ‘(&(attribute=value)(attribute2=value2))’. The default search filter is: ‘objectClass=sudoRole’. If ldap_filter is omitted, no search filter will be used.

SUDOERS_TIMED on/true/yes/off/false/no

Whether or not to evaluate the sudoNotBefore and sudoNotAfter attributes that implement time-dependent sudoers entries.

TIMELIMIT seconds

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

TIMEOUT seconds

The TIMEOUT parameter specifies the amount of time, in seconds, to wait for a response from the various LDAP APIs.

TLS_CACERT file name

An alias for TLS_CACERTFILE for OpenLDAP compatibility.

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’

IBM LDAP:

Unused, the key database specified by TLS_KEY contains both keys and certificates.

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

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. Disabling this 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 IBM LDAP libraries.

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’

IBM LDAP:

‘tls_key /usr/ldap/ldapkey.kdb’

When using IBM LDAP libraries, this file may also contain Certificate Authority and client certificates and may be encrypted.

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 OpenLDAP or IBM Tivoli Directory Server manual for a list of valid ciphers.

This option is not supported by Netscape-derived libraries.

TLS_KEYPW secret

The TLS_KEYPW contains the password used to decrypt the key database on clients using the IBM LDAP library. The secret may be a plaintext password or a base64-encoded string with a “base64:” prefix. For example:

TLS_KEYPW base64:dGVzdA==

If a plaintext password is used, it should be a simple string without quotes. Plain text passwords may not include the comment character (‘#’) and the escaping of special characters with a backslash (‘\’) is not supported. If this option is used, /etc/ldap.conf must not be world-readable to avoid exposing the password. Alternately, a stash file can be used to store the password in encrypted form (see below).

If no TLS_KEYPW is specified, a stash file will be used if it exists. The stash file must have the same path as the file specified by TLS_KEY, but use a ‘.sth’ file extension instead of ‘.kdb’, for example ‘ldapkey.sth’. The default ‘ldapkey.kdb’ that ships with the IBM Tivoli Directory Server is encrypted with the password ‘ssl_password’. The gsk8capicmd utility can be used to manage the key database and create a stash file.

This option is only supported by the IBM LDAP libraries.

TLS_REQCERT level

The TLS_REQCERT parameter controls how the LDAP server's TLS certificated will be verified (if at all). 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. The following level values are supported:

never

The server certificate will not be requested or checked.

allow

The server certificate will be requested. A missing or invalid certificate is ignored and not considered an error.

try

The server certificate will be requested. A missing certificate is ignored but an invalid certificate will result in a connection error.

demand | hard

The server certificate will be requested. A missing or invalid certificate will result in a connection error. This is the default behavior.

This option is only supported by the OpenLDAP libraries. Other LDAP libraries only support the TLS_CHECKPEER parameter.

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.

URI ldap[s]://[hostname[:port]] ...

Specifies a white space-delimited list of one or more URIs describing the LDAP server(s) to connect to. The protocol may be either ldap 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. Both the Netscape-derived and IBM LDAP libraries used on most commercial versions of Unix are only capable of supporting one or the other.

USE_SASL on/true/yes/off/false/no

Enable USE_SASL for LDAP servers that support SASL authentication.

ROOTSASL_AUTH_ID identity

The SASL user name to use when ROOTUSE_SASL is enabled.

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. By default, sudo does not stop searching after the first match and later matches take precedence over earlier ones (unless ‘[SUCCESS=return]’ is used, see below). The following sources are recognized:

In addition, a subset of nsswitch.conf-style action statements is supported, specifically ‘[SUCCESS=return]’ and ‘[NOTFOUND=return]’. These will unconditionally terminate the search if the user was either found ‘[SUCCESS=return]’ or not found ‘[NOTFOUND=return]’ in the immediately preceding source. Other action statements tokens are not supported, nor is test negation with ‘!’.

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

sudoers: ldap files

To consult LDAP only when no match is found in the local sudoers file (if it exists), use:

sudoers: files [SUCCESS=return] ldap

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

The /etc/nsswitch.conf file is supported even when the underlying operating system does not support it, except on AIX (see below).

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 authoritative and only use the local sudoers file if the user is not present in LDAP, use:

sudoers = ldap = auth, files

In the above example, the auth qualifier 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

Integration with sssd¶

On systems with the System Security Services Daemon (SSSD) and where sudo has been built with SSSD support, it is possible to use SSSD to cache LDAP sudoers rules. To use SSSD as the sudoers source, you should use sss instead of ldap for the sudoers entry in /etc/nsswitch.conf. The /etc/ldap.conf file is not used by the SSSD sudo back end. See sssd-sudo(5) for more information on configuring sudo to work with SSSD.

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=my-domain,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 Netscape-derived 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

Sudoers schema for OpenLDAP¶

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. Sites using the optional on-line configuration supported by OpenLDAP 2.3 and higher should apply the schema.olcSudo file instead.

attributetype ( 1.3.6.1.4.1.15953.9.1.1
   NAME 'sudoUser'
   DESC 'User(s) who may  run sudo'
   EQUALITY caseExactMatch
   SUBSTR caseExactSubstringsMatch
   SYNTAX 1.3.6.1.4.1.1466.115.121.1.15 )

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 caseExactMatch
   SYNTAX 1.3.6.1.4.1.1466.115.121.1.15 )

attributetype ( 1.3.6.1.4.1.15953.9.1.7
   NAME 'sudoRunAsGroup'
   DESC 'Group(s) impersonated by sudo'
   EQUALITY caseExactMatch
   SYNTAX 1.3.6.1.4.1.1466.115.121.1.15 )

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 )

attributetype ( 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 )
   )