Provided by: sssd-ad_1.11.8-0ubuntu0.7_amd64 
NAME
sssd-ad - the configuration file for SSSD
DESCRIPTION
This manual page describes the configuration of the AD provider for sssd(8). For a
detailed syntax reference, refer to the “FILE FORMAT” section of the sssd.conf(5) manual
page.
The AD provider is a back end used to connect to an Active Directory server. This provider
requires that the machine be joined to the AD domain and a keytab is available.
The AD provider supports connecting to Active Directory 2008 R2 or later. Earlier versions
may work, but are unsupported.
The AD provider is able to provide identity information and authentication for entities
from trusted domains as well. Currently only trusted domains in the same forest are
recognized.
The AD provider accepts the same options used by the sssd-ldap(5) identity provider and
the sssd-krb5(5) authentication provider with some exceptions described below.
However, it is neither necessary nor recommended to set these options. The AD provider can
also be used as an access, chpass and sudo provider. No configuration of the access
provider is required on the client side.
By default, the AD provider will map UID and GID values from the objectSID parameter in
Active Directory. For details on this, see the “ID MAPPING” section below. If you want to
disable ID mapping and instead rely on POSIX attributes defined in Active Directory, you
should set
ldap_id_mapping = False
In order to retrieve users and groups using POSIX attributes from trusted domains, the AD
administrator must make sure that the POSIX attributes are replicated to the Global
Catalog.
Users, groups and other entities served by SSSD are always treated as case-insensitive in
the AD provider for compatibility with Active Directory's LDAP implementation.
CONFIGURATION OPTIONS
Refer to the section “DOMAIN SECTIONS” of the sssd.conf(5) manual page for details on the
configuration of an SSSD domain.
ad_domain (string)
Specifies the name of the Active Directory domain. This is optional. If not provided,
the configuration domain name is used.
For proper operation, this option should be specified as the lower-case version of the
long version of the Active Directory domain.
The short domain name (also known as the NetBIOS or the flat name) is autodetected by
the SSSD.
ad_server, ad_backup_server (string)
The comma-separated list of hostnames of the AD servers to which SSSD should connect
in order of preference. For more information on failover and server redundancy, see
the “FAILOVER” section. This is optional if autodiscovery is enabled. For more
information on service discovery, refer to the “SERVICE DISCOVERY” section.
ad_hostname (string)
Optional. May be set on machines where the hostname(5) does not reflect the fully
qualified name used in the Active Directory domain to identify this host.
This field is used to determine the host principal in use in the keytab. It must match
the hostname for which the keytab was issued.
ad_enable_dns_sites (boolean)
Enables DNS sites - location based service discovery.
If true and service discovery (see Service Discovery paragraph at the bottom of the
man page) is enabled, the SSSD will first attempt to discover the Active Directory
server to connect to using the Active Directory Site Discovery and fall back to the
DNS SRV records if no AD site is found. The DNS SRV configuration, including the
discovery domain, is used during site discovery as well.
Default: true
ad_access_filter (boolean)
This option specifies LDAP access control filter that the user must match in order to
be allowed access. Please note that the “access_provider” option must be explicitly
set to “ad” in order for this option to have an effect.
The option also supports specifying different filters per domain or forest. This
extended filter would consist of: “KEYWORD:NAME:FILTER”. The keyword can be either
“DOM”, “FOREST” or missing.
If the keyword equals to “DOM” or is missing, then “NAME” specifies the domain or
subdomain the filter applies to. If the keyword equals to “FOREST”, then the filter
equals to all domains from the forest specified by “NAME”.
Multiple filters can be separated with the “?” character, similarly to how search
bases work.
The most specific match is always used. For example, if the option specified filter
for a domain the user is a member of and a global filter, the per-domain filter would
be applied. If there are more matches with the same specification, the first one is
used.
Examples:
# apply filter on domain called dom1 only:
dom1:(memberOf=cn=admins,ou=groups,dc=dom1,dc=com)
# apply filter on domain called dom2 only:
DOM:dom2:(memberOf=cn=admins,ou=groups,dc=dom2,dc=com)
# apply filter on forest called EXAMPLE.COM only:
FOREST:EXAMPLE.COM:(memberOf=cn=admins,ou=groups,dc=example,dc=com)
Default: Not set
ad_site (string)
Specify AD site to which client should try to connect. If this option is not provided,
the AD site will be auto-discovered.
Default: Not set
ad_enable_gc (boolean)
By default, the SSSD connects to the Global Catalog first to retrieve users from
trusted domains and uses the LDAP port to retrieve group memberships or as a fallback.
Disabling this option makes the SSSD only connect to the LDAP port of the current AD
server.
Please note that disabling Global Catalog support does not disable retrieving users
from trusted domains. The SSSD would connect to the LDAP port of trusted domains
instead. However, Global Catalog must be used in order to resolve cross-domain group
memberships.
Default: true
dyndns_update (boolean)
Optional. This option tells SSSD to automatically update the Active Directory DNS
server with the IP address of this client. The update is secured using GSS-TSIG. As a
consequence, the Active Directory administrator only needs to allow secure updates for
the DNS zone. The IP address of the AD LDAP connection is used for the updates, if it
is not otherwise specified by using the “dyndns_iface” option.
NOTE: On older systems (such as RHEL 5), for this behavior to work reliably, the
default Kerberos realm must be set properly in /etc/krb5.conf
Default: true
dyndns_ttl (integer)
The TTL to apply to the client DNS record when updating it. If dyndns_update is false
this has no effect. This will override the TTL serverside if set by an administrator.
Default: 3600 (seconds)
dyndns_iface (string)
Optional. Applicable only when dyndns_update is true. Choose the interface whose IP
address should be used for dynamic DNS updates.
Default: Use the IP address of the AD LDAP connection
dyndns_refresh_interval (integer)
How often should the back end perform periodic DNS update in addition to the automatic
update performed when the back end goes online. This option is optional and applicable
only when dyndns_update is true.
Default: 86400 (24 hours)
dyndns_update_ptr (bool)
Whether the PTR record should also be explicitly updated when updating the client's
DNS records. Applicable only when dyndns_update is true.
Default: True
dyndns_force_tcp (bool)
Whether the nsupdate utility should default to using TCP for communicating with the
DNS server.
Default: False (let nsupdate choose the protocol)
override_homedir (string)
Override the user's home directory. You can either provide an absolute value or a
template. In the template, the following sequences are substituted:
%u
login name
%U
UID number
%d
domain name
%f
fully qualified user name (user@domain)
%o
The original home directory retrieved from the identity provider.
%H
The value of configure option homedir_substring.
%%
a literal '%'
This option can also be set per-domain.
example:
override_homedir = /home/%u
Default: Not set (SSSD will use the value retrieved from LDAP)
homedir_substring (string)
The value of this option will be used in the expansion of the override_homedir option
if the template contains the format string %H. An LDAP directory entry can directly
contain this template so that this option can be used to expand the home directory
path for each client machine (or operating system). It can be set per-domain or
globally in the [nss] section. A value specified in a domain section will override one
set in the [nss] section.
Default: /home
krb5_use_enterprise_principal (boolean)
Specifies if the user principal should be treated as enterprise principal. See section
5 of RFC 6806 for more details about enterprise principals.
Default: true
Note that this default differs from the traditional Kerberos provider back end.
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:
• Making sure the remote servers are reachable
• Stopping the SSSD service
• Removing the database
• Starting the SSSD service
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)
Specifies the lower bound of the range of POSIX IDs to use for mapping Active
Directory user and group SIDs.
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)
Specifies the upper bound of the range of POSIX IDs to use for mapping Active
Directory user and group SIDs.
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)
Specifies the number of IDs available for each slice. If the range size does not
divide evenly into the min and max values, it will create as many complete slices
as it can.
Default: 200000
ldap_idmap_default_domain_sid (string)
Specify the domain SID of the default domain. This will guarantee that this domain
will always be assigned to slice zero in the ID map, bypassing the murmurhash
algorithm described above.
Default: not set
ldap_idmap_default_domain (string)
Specify the name of the default domain.
Default: not set
ldap_idmap_autorid_compat (boolean)
Changes the behavior of the ID-mapping algorithm to behave more similarly to
winbind's “idmap_autorid” algorithm.
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
EXAMPLE
The following example assumes that SSSD is correctly configured and example.com is one of
the domains in the [sssd] section. This example shows only the AD provider-specific
options.
[domain/EXAMPLE]
id_provider = ad
auth_provider = ad
access_provider = ad
chpass_provider = ad
ad_server = dc1.example.com
ad_hostname = client.example.com
ad_domain = example.com
NOTES
The AD access control provider checks if the account is expired. It has the same effect as
the following configuration of the LDAP provider:
access_provider = ldap
ldap_access_order = expire
ldap_account_expire_policy = ad
However, unless the “ad” access control provider is explicitly configured, the default
access provider is “permit”.
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).
AUTHORS
The SSSD upstream - http://fedorahosted.org/sssd