| SSSD-LDAP(5) | File Formats and Conventions | SSSD-LDAP(5) |
NAME¶
sssd-ldap - SSSD LDAP provider
DESCRIPTION¶
This manual page describes the configuration of LDAP domains for sssd(8). Refer to the “FILE FORMAT” section of the sssd.conf(5) manual page for detailed syntax information.
You can configure SSSD to use more than one LDAP domain.
LDAP back end supports id, auth, access and chpass providers. If you want to authenticate against an LDAP server either TLS/SSL or LDAPS is required. sssd does not support authentication over an unencrypted channel. If the LDAP server is used only as an identity provider, an encrypted channel is not needed. Please refer to “ldap_access_filter” config option for more information about using LDAP as an access provider.
CONFIGURATION OPTIONS¶
All of the common configuration options that apply to SSSD domains also apply to LDAP domains. Refer to the “DOMAIN SECTIONS” section of the sssd.conf(5) manual page for full details.
ldap_uri, ldap_backup_uri (string)
The format of the URI must match the format defined in RFC 2732:
ldap[s]://<host>[:port]
For explicit IPv6 addresses, <host> must be enclosed in brackets []
example: ldap://[fc00::126:25]:389
ldap_chpass_uri, ldap_chpass_backup_uri (string)
To enable service discovery ldap_chpass_dns_service_name must be set.
Default: empty, i.e. ldap_uri is used.
ldap_search_base (string)
Starting with SSSD 1.7.0, SSSD supports multiple search bases using the syntax:
search_base[?scope?[filter][?search_base?scope?[filter]]*]
The scope can be one of "base", "onelevel" or "subtree".
The filter must be a valid LDAP search filter as specified by http://www.ietf.org/rfc/rfc2254.txt
Examples:
ldap_search_base = dc=example,dc=com (which is equivalent to) ldap_search_base = dc=example,dc=com?subtree?
ldap_search_base = cn=host_specific,dc=example,dc=com?subtree?(host=thishost)?dc=example.com?subtree?
Note: It is unsupported to have multiple search bases which reference identically-named objects (for example, groups with the same name in two different search bases). This will lead to unpredictable behavior on client machines.
Default: If not set, the value of the defaultNamingContext or namingContexts attribute from the RootDSE of the LDAP server is used. If defaultNamingContext does not exist or has an empty value namingContexts is used. The namingContexts attribute must have a single value with the DN of the search base of the LDAP server to make this work. Multiple values are are not supported.
ldap_schema (string)
Four schema types are currently supported:
The main difference between these schema types is how group memberships are recorded in the server. With rfc2307, group members are listed by name in the memberUid attribute. With rfc2307bis and IPA, group members are listed by DN and stored in the member attribute. The AD schema type sets the attributes to correspond with Active Directory 2008r2 values.
Default: rfc2307
ldap_default_bind_dn (string)
ldap_default_authtok_type (string)
The two mechanisms currently supported are:
password
obfuscated_password
Default: password
ldap_default_authtok (string)
ldap_user_object_class (string)
Default: posixAccount
ldap_user_name (string)
Default: uid (rfc2307, rfc2307bis and IPA), sAMAccountName (AD)
ldap_user_uid_number (string)
Default: uidNumber
ldap_user_gid_number (string)
Default: gidNumber
ldap_user_gecos (string)
Default: gecos
ldap_user_home_directory (string)
Default: homeDirectory
ldap_user_shell (string)
Default: loginShell
ldap_user_uuid (string)
Default: not set in the general case, objectGUID for AD and ipaUniqueID for IPA
ldap_user_objectsid (string)
Default: objectSid for ActiveDirectory, not set for other servers.
ldap_user_modify_timestamp (string)
Default: modifyTimestamp
ldap_user_shadow_last_change (string)
Default: shadowLastChange
ldap_user_shadow_min (string)
Default: shadowMin
ldap_user_shadow_max (string)
Default: shadowMax
ldap_user_shadow_warning (string)
Default: shadowWarning
ldap_user_shadow_inactive (string)
Default: shadowInactive
ldap_user_shadow_expire (string)
Default: shadowExpire
ldap_user_krb_last_pwd_change (string)
Default: krbLastPwdChange
ldap_user_krb_password_expiration (string)
Default: krbPasswordExpiration
ldap_user_ad_account_expires (string)
Default: accountExpires
ldap_user_ad_user_account_control (string)
Default: userAccountControl
ldap_ns_account_lock (string)
Default: nsAccountLock
ldap_user_nds_login_disabled (string)
Default: loginDisabled
ldap_user_nds_login_expiration_time (string)
Default: loginDisabled
ldap_user_nds_login_allowed_time_map (string)
Default: loginAllowedTimeMap
ldap_user_principal (string)
Default: krbPrincipalName
ldap_user_extra_attrs (string)
The list can either contain LDAP attribute names only, or colon-separated tuples of SSSD cache attribute name and LDAP attribute name. In case only LDAP attribute name is specified, the attribute is saved to the cache verbatim. Using a custom SSSD attribute name might be required by environments that configure several SSSD domains with different LDAP schemas.
Please note that several attribute names are reserved by SSSD, notably the “name” attribute. SSSD would report an error if any of the reserved attribute names is used as an extra attribute name.
Examples:
ldap_user_extra_attrs = telephoneNumber
Save the “telephoneNumber” attribute from LDAP as “telephoneNumber” to the cache.
ldap_user_extra_attrs = phone:telephoneNumber
Save the “telephoneNumber” attribute from LDAP as “phone” to the cache.
Default: not set
ldap_user_ssh_public_key (string)
Default: sshPublicKey
ldap_force_upper_case_realm (boolean)
Default: false
ldap_enumeration_refresh_timeout (integer)
Default: 300
ldap_purge_cache_timeout (integer)
Setting this option to zero will disable the cache cleanup operation. Please note that if enumeration is enabled, the cleanup task is required in order to detect entries removed from the server and can´t be disabled. By default, the cleanup task will run every 3 hours with enumeration enabled.
Default: 0 (disabled)
ldap_user_fullname (string)
Default: cn
ldap_user_member_of (string)
Default: memberOf
ldap_user_authorized_service (string)
An explicit deny (!svc) is resolved first. Second, SSSD searches for explicit allow (svc) and finally for allow_all (*).
Please note that the ldap_access_order configuration option must include “authorized_service” in order for the ldap_user_authorized_service option to work.
Default: authorizedService
ldap_user_authorized_host (string)
An explicit deny (!host) is resolved first. Second, SSSD searches for explicit allow (host) and finally for allow_all (*).
Please note that the ldap_access_order configuration option must include “host” in order for the ldap_user_authorized_host option to work.
Default: host
ldap_user_certificate (string)
Default: no set in the general case, userCertificate;binary for IPA
ldap_group_object_class (string)
Default: posixGroup
ldap_group_name (string)
Default: cn (rfc2307, rfc2307bis and IPA), sAMAccountName (AD)
ldap_group_gid_number (string)
Default: gidNumber
ldap_group_member (string)
Default: memberuid (rfc2307) / member (rfc2307bis)
ldap_group_uuid (string)
Default: not set in the general case, objectGUID for AD and ipaUniqueID for IPA
ldap_group_objectsid (string)
Default: objectSid for ActiveDirectory, not set for other servers.
ldap_group_modify_timestamp (string)
Default: modifyTimestamp
ldap_group_type (integer)
This attribute is currently only used by the AD provider to determine if a group is a domain local groups and has to be filtered out for trusted domains.
Default: groupType in the AD provider, othewise not set
ldap_group_nesting_level (integer)
Note: This option specifies the guaranteed level of nested groups to be processed for any lookup. However, nested groups beyond this limit may be returned if previous lookups already resolved the deeper nesting levels. Also, subsequent lookups for other groups may enlarge the result set for original lookup if re-queried.
If ldap_group_nesting_level is set to 0 then no nested groups are processed at all. However, when connected to Active-Directory Server 2008 and later using “id_provider=ad” it is furthermore required to disable usage of Token-Groups by setting ldap_use_tokengroups to false in order to restrict group nesting.
Default: 2
ldap_groups_use_matching_rule_in_chain
In most common cases, it is best to leave this option disabled. It generally only provides a performance increase on very complex nestings.
If this option is enabled, SSSD will use it if it detects that the server supports it during initial connection. So "True" here essentially means "auto-detect".
Note: This feature is currently known to work only with Active Directory 2008 R1 and later. See MSDN(TM) documentation[1] for more details.
Default: False
ldap_initgroups_use_matching_rule_in_chain
If this option is enabled, SSSD will use it if it detects that the server supports it during initial connection. So "True" here essentially means "auto-detect".
Note: This feature is currently known to work only with Active Directory 2008 R1 and later. See MSDN(TM) documentation[1] for more details.
Default: False
ldap_use_tokengroups
Default: True for AD and IPA otherwise False.
ldap_netgroup_object_class (string)
In IPA provider, ipa_netgroup_object_class should be used instead.
Default: nisNetgroup
ldap_netgroup_name (string)
In IPA provider, ipa_netgroup_name should be used instead.
Default: cn
ldap_netgroup_member (string)
In IPA provider, ipa_netgroup_member should be used instead.
Default: memberNisNetgroup
ldap_netgroup_triple (string)
This option is not available in IPA provider.
Default: nisNetgroupTriple
ldap_netgroup_modify_timestamp (string)
This option is not available in IPA provider.
Default: modifyTimestamp
ldap_service_object_class (string)
Default: ipService
ldap_service_name (string)
Default: cn
ldap_service_port (string)
Default: ipServicePort
ldap_service_proto (string)
Default: ipServiceProtocol
ldap_service_search_base (string)
syntax:
search_base[?scope?[filter][?search_base?scope?[filter]]*]
The scope can be one of "base", "onelevel" or "subtree". The scope functions as specified in section 4.5.1.2 of http://tools.ietf.org/html/rfc4511
The filter must be a valid LDAP search filter as specified by http://www.ietf.org/rfc/rfc2254.txt
For examples of this syntax, please refer to the “ldap_search_base” examples section.
Default: the value of ldap_search_base
Please note that specifying scope or filter is not supported for searches against an Active Directory Server that might yield a large number of results and trigger the Range Retrieval extension in the response.
ldap_search_timeout (integer)
Note: this option is subject to change in future versions of the SSSD. It will likely be replaced at some point by a series of timeouts for specific lookup types.
Default: 6
ldap_enumeration_search_timeout (integer)
Default: 60
ldap_network_timeout (integer)
Default: 6
ldap_opt_timeout (integer)
Default: 6
ldap_connection_expire_timeout (integer)
Default: 900 (15 minutes)
ldap_page_size (integer)
Default: 1000
ldap_disable_paging (boolean)
Example: OpenLDAP servers with the paging control module installed on the server but not enabled will report it in the RootDSE but be unable to use it.
Example: 389 DS has a bug where it can only support a one paging control at a time on a single connection. On busy clients, this can result in some requests being denied.
Default: False
ldap_disable_range_retrieval (boolean)
Active Directory limits the number of members to be retrieved in a single lookup using the MaxValRange policy (which defaults to 1500 members). If a group contains more members, the reply would include an AD-specific range extension. This option disables parsing of the range extension, therefore large groups will appear as having no members.
Default: False
ldap_sasl_minssf (integer)
Default: Use the system default (usually specified by ldap.conf)
ldap_deref_threshold (integer)
You can turn off dereference lookups completely by setting the value to 0.
A dereference lookup is a means of fetching all group members in a single LDAP call. Different LDAP servers may implement different dereference methods. The currently supported servers are 389/RHDS, OpenLDAP and Active Directory.
Note: If any of the search bases specifies a search filter, then the dereference lookup performance enhancement will be disabled regardless of this setting.
Default: 10
ldap_tls_reqcert (string)
never = The client will not request or check any server certificate.
allow = The server certificate is requested. If no certificate is provided, the session proceeds normally. If a bad certificate is provided, it will be ignored and the session proceeds normally.
try = The server certificate is requested. If no certificate is provided, the session proceeds normally. If a bad certificate is provided, the session is immediately terminated.
demand = The server certificate is requested. If no certificate is provided, or a bad certificate is provided, the session is immediately terminated.
hard = Same as “demand”
Default: hard
ldap_tls_cacert (string)
Default: use OpenLDAP defaults, typically in /etc/openldap/ldap.conf
ldap_tls_cacertdir (string)
Default: use OpenLDAP defaults, typically in /etc/openldap/ldap.conf
ldap_tls_cert (string)
Default: not set
ldap_tls_key (string)
Default: not set
ldap_tls_cipher_suite (string)
Default: use OpenLDAP defaults, typically in /etc/openldap/ldap.conf
ldap_id_use_start_tls (boolean)
Default: false
ldap_id_mapping (boolean)
Currently this feature supports only ActiveDirectory objectSID mapping.
Default: false
ldap_min_id, ldap_max_id (interger)
Default: not set (both options are set to 0)
ldap_sasl_mech (string)
Default: not set
ldap_sasl_authid (string)
Default: host/hostname@REALM
ldap_sasl_realm (string)
Default: the value of krb5_realm.
ldap_sasl_canonicalize (boolean)
Default: false;
ldap_krb5_keytab (string)
Default: System keytab, normally /etc/krb5.keytab
ldap_krb5_init_creds (boolean)
Default: true
ldap_krb5_ticket_lifetime (integer)
Default: 86400 (24 hours)
krb5_server, krb5_backup_server (string)
When using service discovery for KDC or kpasswd servers, SSSD first searches for DNS entries that specify _udp as the protocol and falls back to _tcp if none are found.
This option was named “krb5_kdcip” in earlier releases of SSSD. While the legacy name is recognized for the time being, users are advised to migrate their config files to use “krb5_server” instead.
krb5_realm (string)
Default: System defaults, see /etc/krb5.conf
krb5_canonicalize (boolean)
Default: false
krb5_use_kdcinfo (boolean)
See the sssd_krb5_locator_plugin(8) manual page for more information on the locator plugin.
Default: true
ldap_pwd_policy (string)
none - No evaluation on the client side. This option cannot disable server-side password policies.
shadow - Use shadow(5) style attributes to evaluate if the password has expired.
mit_kerberos - Use the attributes used by MIT Kerberos to determine if the password has expired. Use chpass_provider=krb5 to update these attributes when the password is changed.
Default: none
Note: if a password policy is configured on server side, it always takes precedence over policy set with this option.
ldap_referrals (boolean)
Please note that sssd only supports referral chasing when it is compiled with OpenLDAP version 2.4.13 or higher.
Chasing referrals may incur a performance penalty in environments that use them heavily, a notable example is Microsoft Active Directory. If your setup does not in fact require the use of referrals, setting this option to false might bring a noticeable performance improvement.
Default: true
ldap_dns_service_name (string)
Default: ldap
ldap_chpass_dns_service_name (string)
Default: not set, i.e. service discovery is disabled
ldap_chpass_update_last_change (bool)
Default: False
ldap_access_filter (string)
Example:
access_provider = ldap ldap_access_filter = (employeeType=admin)
This example means that access to this host is restricted to users whose employeeType attribute is set to "admin".
Offline caching for this feature is limited to determining whether the user´s last online login was granted access permission. If they were granted access during their last login, they will continue to be granted access while offline and vice-versa.
Default: Empty
ldap_account_expire_policy (string)
Please note that it is always recommended to use server side access control, i.e. the LDAP server should deny the bind request with a suitable error code even if the password is correct.
The following values are allowed:
shadow: use the value of ldap_user_shadow_expire to determine if the account is expired.
ad: use the value of the 32bit field ldap_user_ad_user_account_control and allow access if the second bit is not set. If the attribute is missing access is granted. Also the expiration time of the account is checked.
rhds, ipa, 389ds: use the value of ldap_ns_account_lock to check if access is allowed or not.
nds: the values of ldap_user_nds_login_allowed_time_map, ldap_user_nds_login_disabled and ldap_user_nds_login_expiration_time are used to check if access is allowed. If both attributes are missing access is granted. This is an experimental feature, please use http://fedorahosted.org/sssd to report any issues.
Please note that the ldap_access_order configuration option must include “expire” in order for the ldap_account_expire_policy option to work.
Default: Empty
ldap_access_order (string)
filter: use ldap_access_filter
lockout: use account locking. If set, this option denies access in case that ldap attribute ´pwdAccountLockedTime´ is present and has value of ´000001010000Z´. Please see the option ldap_pwdlockout_dn. Please note that ´access_provider = ldap´ must be set for this feature to work.
Please note that this option is superseded by the “ppolicy” option and might be removed in a future release.
ppolicy: use account locking. If set, this option denies access in case that ldap attribute ´pwdAccountLockedTime´ is present and has value of ´000001010000Z´ or represents any time in the past. The value of the ´pwdAccountLockedTime´ attribute must end with ´Z´, which denotes the UTC time zone. Other time zones are not currently supported and will result in "access-denied" when users attempt to log in. Please see the option ldap_pwdlockout_dn. Please note that ´access_provider = ldap´ must be set for this feature to work.
expire: use ldap_account_expire_policy
pwd_expire_policy_reject, pwd_expire_policy_warn, pwd_expire_policy_renew: These options are useful if users are interested in being warned that password is about to expire and authentication is based on using a different method than passwords - for example SSH keys.
The difference between these options is the action taken if user password is expired: pwd_expire_policy_reject - user is denied to log in, pwd_expire_policy_warn - user is still able to log in, pwd_expire_policy_renew - user is prompted to change his password immediately.
Note If user password is expired no explicit message is prompted by SSSD.
Please note that ´access_provider = ldap´ must be set for this feature to work. Also ´ldap_pwd_policy´ must be set to an appropriate password policy.
authorized_service: use the authorizedService attribute to determine access
host: use the host attribute to determine access
Default: filter
Please note that it is a configuration error if a value is used more than once.
ldap_pwdlockout_dn (string)
Example: cn=ppolicy,ou=policies,dc=example,dc=com
Default: cn=ppolicy,ou=policies,$ldap_search_base
ldap_deref (string)
never: Aliases are never dereferenced.
searching: Aliases are dereferenced in subordinates of the base object, but not in locating the base object of the search.
finding: Aliases are only dereferenced when locating the base object of the search.
always: Aliases are dereferenced both in searching and in locating the base object of the search.
Default: Empty (this is handled as never by the LDAP client libraries)
ldap_rfc2307_fallback_to_local_users (boolean)
In some environments where the RFC2307 schema is used, local users are made members of LDAP groups by adding their names to the memberUid attribute. The self-consistency of the domain is compromised when this is done, so SSSD would normally remove the "missing" users from the cached group memberships as soon as nsswitch tries to fetch information about the user via getpw*() or initgroups() calls.
This option falls back to checking if local users are referenced, and caches them so that later initgroups() calls will augment the local users with the additional LDAP groups.
Default: false
wildcart_limit (integer)
At the moment, only the InfoPipe responder supports wildcard lookups.
Default: 1000 (often the size of one page)
SUDO OPTIONS¶
The detailed instructions for configuration of sudo_provider are in the manual page sssd-sudo(5).
ldap_sudorule_object_class (string)
Default: sudoRole
ldap_sudorule_name (string)
Default: cn
ldap_sudorule_command (string)
Default: sudoCommand
ldap_sudorule_host (string)
Default: sudoHost
ldap_sudorule_user (string)
Default: sudoUser
ldap_sudorule_option (string)
Default: sudoOption
ldap_sudorule_runasuser (string)
Default: sudoRunAsUser
ldap_sudorule_runasgroup (string)
Default: sudoRunAsGroup
ldap_sudorule_notbefore (string)
Default: sudoNotBefore
ldap_sudorule_notafter (string)
Default: sudoNotAfter
ldap_sudorule_order (string)
Default: sudoOrder
ldap_sudo_full_refresh_interval (integer)
The value must be greater than ldap_sudo_smart_refresh_interval
Default: 21600 (6 hours)
ldap_sudo_smart_refresh_interval (integer)
If USN attributes are not supported by the server, the modifyTimestamp attribute is used instead.
Default: 900 (15 minutes)
ldap_sudo_use_host_filter (boolean)
Default: true
ldap_sudo_hostnames (string)
If this option is empty, SSSD will try to discover the hostname and the fully qualified domain name automatically.
If ldap_sudo_use_host_filter is false then this option has no effect.
Default: not specified
ldap_sudo_ip (string)
If this option is empty, SSSD will try to discover the addresses automatically.
If ldap_sudo_use_host_filter is false then this option has no effect.
Default: not specified
ldap_sudo_include_netgroups (boolean)
If ldap_sudo_use_host_filter is false then this option has no effect.
Default: true
ldap_sudo_include_regexp (boolean)
If ldap_sudo_use_host_filter is false then this option has no effect.
Default: true
This manual page only describes attribute name mapping. For detailed explanation of sudo related attribute semantics, see sudoers.ldap(5)
AUTOFS OPTIONS¶
Some of the defaults for the parameters below are dependent on the LDAP schema.
ldap_autofs_map_master_name (string)
Default: auto.master
ldap_autofs_map_object_class (string)
Default: automountMap
ldap_autofs_map_name (string)
Default: ou (rfc2307), automountMapName (rfc2307bis, ipa, ad)
ldap_autofs_entry_object_class (string)
Default: automount
ldap_autofs_entry_key (string)
Default: cn (rfc2307), automountKey (rfc2307bis, ipa, ad)
ldap_autofs_entry_value (string)
Default: automountInformation
Please note that the automounter only reads the master map on startup, so if any autofs-related changes are made to the sssd.conf, you typically also need to restart the automounter daemon after restarting the SSSD.
ADVANCED OPTIONS¶
These options are supported by LDAP domains, but they should be used with caution. Please include them in your configuration only if you know what you are doing.
ldap_netgroup_search_base (string)
syntax:
search_base[?scope?[filter][?search_base?scope?[filter]]*]
The scope can be one of "base", "onelevel" or "subtree". The scope functions as specified in section 4.5.1.2 of http://tools.ietf.org/html/rfc4511
The filter must be a valid LDAP search filter as specified by http://www.ietf.org/rfc/rfc2254.txt
For examples of this syntax, please refer to the “ldap_search_base” examples section.
Default: the value of ldap_search_base
Please note that specifying scope or filter is not supported for searches against an Active Directory Server that might yield a large number of results and trigger the Range Retrieval extension in the response.
ldap_user_search_base (string)
syntax:
search_base[?scope?[filter][?search_base?scope?[filter]]*]
The scope can be one of "base", "onelevel" or "subtree". The scope functions as specified in section 4.5.1.2 of http://tools.ietf.org/html/rfc4511
The filter must be a valid LDAP search filter as specified by http://www.ietf.org/rfc/rfc2254.txt
For examples of this syntax, please refer to the “ldap_search_base” examples section.
Default: the value of ldap_search_base
Please note that specifying scope or filter is not supported for searches against an Active Directory Server that might yield a large number of results and trigger the Range Retrieval extension in the response.
ldap_group_search_base (string)
syntax:
search_base[?scope?[filter][?search_base?scope?[filter]]*]
The scope can be one of "base", "onelevel" or "subtree". The scope functions as specified in section 4.5.1.2 of http://tools.ietf.org/html/rfc4511
The filter must be a valid LDAP search filter as specified by http://www.ietf.org/rfc/rfc2254.txt
For examples of this syntax, please refer to the “ldap_search_base” examples section.
Default: the value of ldap_search_base
Please note that specifying scope or filter is not supported for searches against an Active Directory Server that might yield a large number of results and trigger the Range Retrieval extension in the response.
Note
If the option “ldap_use_tokengroups” is enabled. The searches against Active Directory will not be restricted and return all groups memberships, even with no gid mapping. It is recommended to disable this feature, if group names are not being displayed correctly.
ldap_sudo_search_base (string)
syntax:
search_base[?scope?[filter][?search_base?scope?[filter]]*]
The scope can be one of "base", "onelevel" or "subtree". The scope functions as specified in section 4.5.1.2 of http://tools.ietf.org/html/rfc4511
The filter must be a valid LDAP search filter as specified by http://www.ietf.org/rfc/rfc2254.txt
For examples of this syntax, please refer to the “ldap_search_base” examples section.
Default: the value of ldap_search_base
Please note that specifying scope or filter is not supported for searches against an Active Directory Server that might yield a large number of results and trigger the Range Retrieval extension in the response.
ldap_autofs_search_base (string)
syntax:
search_base[?scope?[filter][?search_base?scope?[filter]]*]
The scope can be one of "base", "onelevel" or "subtree". The scope functions as specified in section 4.5.1.2 of http://tools.ietf.org/html/rfc4511
The filter must be a valid LDAP search filter as specified by http://www.ietf.org/rfc/rfc2254.txt
For examples of this syntax, please refer to the “ldap_search_base” examples section.
Default: the value of ldap_search_base
Please note that specifying scope or filter is not supported for searches against an Active Directory Server that might yield a large number of results and trigger the Range Retrieval extension in the response.
FAILOVER¶
The failover feature allows back ends to automatically switch to a different server if the current server fails.
Failover Syntax¶
The list of servers is given as a comma-separated list; any number of spaces is allowed around the comma. The servers are listed in order of preference. The list can contain any number of servers.
For each failover-enabled config option, two variants exist: primary and backup. The idea is that servers in the primary list are preferred and backup servers are only searched if no primary servers can be reached. If a backup server is selected, a timeout of 31 seconds is set. After this timeout SSSD will periodically try to reconnect to one of the primary servers. If it succeeds, it will replace the current active (backup) server.
The Failover Mechanism¶
The failover mechanism distinguishes between a machine and a service. The back end first tries to resolve the hostname of a given machine; if this resolution attempt fails, the machine is considered offline. No further attempts are made to connect to this machine for any other service. If the resolution attempt succeeds, the back end tries to connect to a service on this machine. If the service connection attempt fails, then only this particular service is considered offline and the back end automatically switches over to the next service. The machine is still considered online and might still be tried for another service.
Further connection attempts are made to machines or services marked as offline after a specified period of time; this is currently hard coded to 30 seconds.
If there are no more machines to try, the back end as a whole switches to offline mode, and then attempts to reconnect every 30 seconds.
SERVICE DISCOVERY¶
The service discovery feature allows back ends to automatically find the appropriate servers to connect to using a special DNS query. This feature is not supported for backup servers.
Configuration¶
If no servers are specified, the back end automatically uses service discovery to try to find a server. Optionally, the user may choose to use both fixed server addresses and service discovery by inserting a special keyword, “_srv_”, in the list of servers. The order of preference is maintained. This feature is useful if, for example, the user prefers to use service discovery whenever possible, and fall back to a specific server when no servers can be discovered using DNS.
The domain name¶
Please refer to the “dns_discovery_domain” parameter in the sssd.conf(5) manual page for more details.
The protocol¶
The queries usually specify _tcp as the protocol. Exceptions are documented in respective option description.
See Also¶
For more information on the service discovery mechanism, refer to RFC 2782.
ID MAPPING¶
The ID-mapping feature allows SSSD to act as a client of Active Directory without requiring administrators to extend user attributes to support POSIX attributes for user and group identifiers.
NOTE: When ID-mapping is enabled, the uidNumber and gidNumber attributes are ignored. This is to avoid the possibility of conflicts between automatically-assigned and manually-assigned values. If you need to use manually-assigned values, ALL values must be manually-assigned.
Please note that changing the ID mapping related configuration options will cause user and group IDs to change. At the moment, SSSD does not support changing IDs, so the SSSD database must be removed. Because cached passwords are also stored in the database, removing the database should only be performed while the authentication servers are reachable, otherwise users might get locked out. In order to cache the password, an authentication must be performed. It is not sufficient to use sss_cache(8) to remove the database, rather the process consists of:
Moreover, as the change of IDs might necessitate the adjustment of other system properties such as file and directory ownership, it´s advisable to plan ahead and test the ID mapping configuration thoroughly.
Mapping Algorithm¶
Active Directory provides an objectSID for every user and group object in the directory. This objectSID can be broken up into components that represent the Active Directory domain identity and the relative identifier (RID) of the user or group object.
The SSSD ID-mapping algorithm takes a range of available UIDs and divides it into equally-sized component sections - called "slices"-. Each slice represents the space available to an Active Directory domain.
When a user or group entry for a particular domain is encountered for the first time, the SSSD allocates one of the available slices for that domain. In order to make this slice-assignment repeatable on different client machines, we select the slice based on the following algorithm:
The SID string is passed through the murmurhash3 algorithm to convert it to a 32-bit hashed value. We then take the modulus of this value with the total number of available slices to pick the slice.
NOTE: It is possible to encounter collisions in the hash and subsequent modulus. In these situations, we will select the next available slice, but it may not be possible to reproduce the same exact set of slices on other machines (since the order that they are encountered will determine their slice). In this situation, it is recommended to either switch to using explicit POSIX attributes in Active Directory (disabling ID-mapping) or configure a default domain to guarantee that at least one is always consistent. See “Configuration” for details.
Configuration¶
Minimum configuration (in the “[domain/DOMAINNAME]” section):
ldap_id_mapping = True ldap_schema = ad
The default configuration results in configuring 10,000 slices, each capable of holding up to 200,000 IDs, starting from 10,001 and going up to 2,000,100,000. This should be sufficient for most deployments.
Advanced Configuration
ldap_idmap_range_min (integer)
NOTE: This option is different from “min_id” in that “min_id” acts to filter the output of requests to this domain, whereas this option controls the range of ID assignment. This is a subtle distinction, but the good general advice would be to have “min_id” be less-than or equal to “ldap_idmap_range_min”
Default: 200000
ldap_idmap_range_max (integer)
NOTE: This option is different from “max_id” in that “max_id” acts to filter the output of requests to this domain, whereas this option controls the range of ID assignment. This is a subtle distinction, but the good general advice would be to have “max_id” be greater-than or equal to “ldap_idmap_range_max”
Default: 2000200000
ldap_idmap_range_size (integer)
NOTE: The value of this option must be at least as large as the highest user RID planned for use on the Active Directory server. User lookups and login will fail for any user whose RID is greater than this value.
For example, if your most recently-added Active Directory user has objectSid=S-1-5-21-2153326666-2176343378-3404031434-1107, “ldap_idmap_range_size” must be at least 1108 as range size is equal to maximal SID minus minimal SID plus one (e.g. 1108 = 1107 - 0 + 1).
It is important to plan ahead for future expansion, as changing this value will result in changing all of the ID mappings on the system, leading to users with different local IDs than they previously had.
Default: 200000
ldap_idmap_default_domain_sid (string)
Default: not set
ldap_idmap_default_domain (string)
Default: not set
ldap_idmap_autorid_compat (boolean)
When this option is configured, domains will be allocated starting with slice zero and increasing monatomically with each additional domain.
NOTE: This algorithm is non-deterministic (it depends on the order that users and groups are requested). If this mode is required for compatibility with machines running winbind, it is recommended to also use the “ldap_idmap_default_domain_sid” option to guarantee that at least one domain is consistently allocated to slice zero.
Default: False
ldap_idmap_helper_table_size (integer)
Note: Additional secondary slices might be generated when SID is being mapped to UNIX id and RID part of SID is out of range for secondary slices generated so far. If value of ldap_idmap_helper_table_size is equal to 0 then no additional secondary slices are generated.
Default: 10
Well-Known SIDs¶
SSSD supports to look up the names of Well-Known SIDs, i.e. SIDs with a special hardcoded meaning. Since the generic users and groups related to those Well-Known SIDs have no equivalent in a Linux/UNIX environment no POSIX IDs are available for those objects.
The SID name space is organized in authorities which can be seen as different domains. The authorities for the Well-Known SIDs are
The capitalized version of these names are used as domain names when returning the fully qualified name of a Well-Known SID.
Since some utilities allow to modify SID based access control information with the help of a name instead of using the SID directly SSSD supports to look up the SID by the name as well. To avoid collisions only the fully qualified names can be used to look up Well-Known SIDs. As a result the domain names “NULL AUTHORITY”, “WORLD AUTHORITY”, “ LOCAL AUTHORITY”, “CREATOR AUTHORITY”, “NT AUTHORITY” and “BUILTIN” should not be used as domain names in sssd.conf.
EXAMPLE¶
The following example assumes that SSSD is correctly configured and LDAP is set to one of the domains in the [domains] section.
[domain/LDAP] id_provider = ldap auth_provider = ldap ldap_uri = ldap://ldap.mydomain.org ldap_search_base = dc=mydomain,dc=org ldap_tls_reqcert = demand cache_credentials = true
LDAP ACCESS FILTER EXAMPLE¶
The following example assumes that SSSD is correctly configured and to use the ldap_access_order=lockout.
[domain/LDAP] id_provider = ldap auth_provider = ldap access_provider = ldap ldap_access_order = lockout ldap_pwdlockout_dn = cn=ppolicy,ou=policies,dc=mydomain,dc=org ldap_uri = ldap://ldap.mydomain.org ldap_search_base = dc=mydomain,dc=org ldap_tls_reqcert = demand cache_credentials = true
NOTES¶
The descriptions of some of the configuration options in this manual page are based on the ldap.conf(5) manual page from the OpenLDAP 2.4 distribution.
SEE ALSO¶
sssd(8), sssd.conf(5), sssd-ldap(5), sssd-krb5(5), sssd-simple(5), sssd-ipa(5), sssd-ad(5), sssd-sudo(5), sss_cache(8), sss_debuglevel(8), sss_groupadd(8), sss_groupdel(8), sss_groupshow(8), sss_groupmod(8), sss_useradd(8), sss_userdel(8), sss_usermod(8), sss_obfuscate(8), sss_seed(8), sssd_krb5_locator_plugin(8), sss_ssh_authorizedkeys(8), sss_ssh_knownhostsproxy(8), sssd-ifp(5), pam_sss(8). sss_rpcidmapd(5)
AUTHORS¶
The SSSD upstream - http://fedorahosted.org/sssd
NOTES¶
- 1.
- MSDN(TM) documentation
| 01/16/2019 | SSSD |