diff options
Diffstat (limited to 'src/man/br/include/ldap_id_mapping.xml')
| -rw-r--r-- | src/man/br/include/ldap_id_mapping.xml | 284 |
1 files changed, 284 insertions, 0 deletions
diff --git a/src/man/br/include/ldap_id_mapping.xml b/src/man/br/include/ldap_id_mapping.xml new file mode 100644 index 0000000..f80be8d --- /dev/null +++ b/src/man/br/include/ldap_id_mapping.xml @@ -0,0 +1,284 @@ +<refsect1 id='idmap'> + <title>ID MAPPING</title> + <para> + 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. + </para> + <para> + 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. + </para> + <para> + 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 <citerefentry> +<refentrytitle>sss_cache</refentrytitle> <manvolnum>8</manvolnum> +</citerefentry> to remove the database, rather the process consists of: + <itemizedlist> + <listitem> + <para> + Making sure the remote servers are reachable + </para> + </listitem> + <listitem> + <para> + Stopping the SSSD service + </para> + </listitem> + <listitem> + <para> + Removing the database + </para> + </listitem> + <listitem> + <para> + Starting the SSSD service + </para> + </listitem> + </itemizedlist> + 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. + </para> + + <refsect2 id='idmap_algorithm'> + <title>Mapping Algorithm</title> + <para> + 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. + </para> + <para> + 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. + </para> + <para> + 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: + </para> + <para> + 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. + </para> + <para> + 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 <quote>Configuration</quote> for details. + </para> + </refsect2> + + <refsect2 id='idmap_config'> + <title>Configuration</title> + <para> + Minimum configuration (in the <quote>[domain/DOMAINNAME]</quote> section): + </para> + <para> +<programlisting> +ldap_id_mapping = True +ldap_schema = ad +</programlisting> + </para> + <para> + The default configuration results in configuring 10,000 slices, each capable +of holding up to 200,000 IDs, starting from 200,000 and going up to +2,000,200,000. This should be sufficient for most deployments. + </para> + <refsect3 id='idmap_advanced_config'> + <title>Advanced Configuration</title> + <variablelist> + <varlistentry> + <term>ldap_idmap_range_min (integer)</term> + <listitem> + <para> + Specifies the lower (inclusive) bound of the range of POSIX IDs to use for +mapping Active Directory user and group SIDs. It is the first POSIX ID which +can be used for the mapping. + </para> + <para> + NOTE: This option is different from <quote>min_id</quote> in that +<quote>min_id</quote> 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 +<quote>min_id</quote> be less-than or equal to +<quote>ldap_idmap_range_min</quote> + </para> + <para> + Default: 200000 + </para> + </listitem> + </varlistentry> + <varlistentry> + <term>ldap_idmap_range_max (integer)</term> + <listitem> + <para> + Specifies the upper (exclusive) bound of the range of POSIX IDs to use for +mapping Active Directory user and group SIDs. It is the first POSIX ID which +cannot be used for the mapping anymore, i.e. one larger than the last one +which can be used for the mapping. + </para> + <para> + NOTE: This option is different from <quote>max_id</quote> in that +<quote>max_id</quote> 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 +<quote>max_id</quote> be greater-than or equal to +<quote>ldap_idmap_range_max</quote> + </para> + <para> + Default: 2000200000 + </para> + </listitem> + </varlistentry> + <varlistentry> + <term>ldap_idmap_range_size (integer)</term> + <listitem> + <para> + 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. + </para> + <para> + 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. + </para> + <para> + For example, if your most recently-added Active Directory user has +objectSid=S-1-5-21-2153326666-2176343378-3404031434-1107, +<quote>ldap_idmap_range_size</quote> must be at least 1108 as range size is +equal to maximal SID minus minimal SID plus one (e.g. 1108 = 1107 - 0 + 1). + </para> + <para> + 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. + </para> + <para> + Default: 200000 + </para> + </listitem> + </varlistentry> + <varlistentry> + <term>ldap_idmap_default_domain_sid (string)</term> + <listitem> + <para> + 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. + </para> + <para> + Default: not set + </para> + </listitem> + </varlistentry> + <varlistentry> + <term>ldap_idmap_default_domain (string)</term> + <listitem> + <para> + Specify the name of the default domain. + </para> + <para> + Default: not set + </para> + </listitem> + </varlistentry> + <varlistentry> + <term>ldap_idmap_autorid_compat (boolean)</term> + <listitem> + <para> + Changes the behavior of the ID-mapping algorithm to behave more similarly to +winbind's <quote>idmap_autorid</quote> algorithm. + </para> + <para> + When this option is configured, domains will be allocated starting with +slice zero and increasing monotonically with each additional domain. + </para> + <para> + 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 +<quote>ldap_idmap_default_domain_sid</quote> option to guarantee that at +least one domain is consistently allocated to slice zero. + </para> + <para> + Default: False + </para> + </listitem> + </varlistentry> + <varlistentry> + <term>ldap_idmap_helper_table_size (integer)</term> + <listitem> + <para> + Maximal number of secondary slices that is tried when performing mapping +from UNIX id to SID. + </para> + <para> + 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. + </para> + <para> + Default: 10 + </para> + </listitem> + </varlistentry> + </variablelist> + </refsect3> + </refsect2> + + <refsect2 id='well_known_sids'> + <title>Well-Known SIDs</title> + <para> + 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. + </para> + <para> + The SID name space is organized in authorities which can be seen as +different domains. The authorities for the Well-Known SIDs are + <itemizedlist> + <listitem><para>Null Authority</para></listitem> + <listitem><para>World Authority</para></listitem> + <listitem><para>Local Authority</para></listitem> + <listitem><para>Creator Authority</para></listitem> + <listitem><para>Mandatory Label Authority</para></listitem> + <listitem><para>Authentication Authority</para></listitem> + <listitem><para>NT Authority</para></listitem> + <listitem><para>Built-in</para></listitem> + </itemizedlist> + The capitalized version of these names are used as domain names when +returning the fully qualified name of a Well-Known SID. + </para> + <para> + 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 <quote>NULL AUTHORITY</quote>, <quote>WORLD AUTHORITY</quote>, +<quote>LOCAL AUTHORITY</quote>, <quote>CREATOR AUTHORITY</quote>, +<quote>MANDATORY LABEL AUTHORITY</quote>, <quote>AUTHENTICATION +AUTHORITY</quote>, <quote>NT AUTHORITY</quote> and <quote>BUILTIN</quote> +should not be used as domain names in <filename>sssd.conf</filename>. + </para> + </refsect2> + +</refsect1> |