sssd-kcm(8)

1SSSD-KCM(8)              File Formats and Conventions              SSSD-KCM(8)
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NAME

6       sssd-kcm - SSSD Kerberos Cache Manager
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DESCRIPTION

9       This manual page describes the configuration of the SSSD Kerberos Cache
10       Manager (KCM). KCM is a process that stores, tracks and manages
11       Kerberos credential caches. It originates in the Heimdal Kerberos
12       project, although the MIT Kerberos library also provides client side
13       (more details on that below) support for the KCM credential cache.
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15       In a setup where Kerberos caches are managed by KCM, the Kerberos
16       library (typically used through an application, like e.g., kinit(1), is
17       a “"KCM client"” and the KCM daemon is being referred to as a “"KCM
18       server"”. The client and server communicate over a UNIX socket.
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20       The KCM server keeps track of each credential caches's owner and
21       performs access check control based on the UID and GID of the KCM
22       client. The root user has access to all credential caches.
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24       The KCM credential cache has several interesting properties:
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26       ·   since the process runs in userspace, it is subject to UID
27           namespacing, unlike the kernel keyring
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29       ·   unlike the kernel keyring-based cache, which is shared between all
30           containers, the KCM server is a separate process whose entry point
31           is a UNIX socket
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33       ·   the SSSD implementation stores the ccaches in a database, typically
34           located at /var/lib/sss/secrets allowing the ccaches to survive KCM
35           server restarts or machine reboots.
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37       This allows the system to use a collection-aware credential cache, yet
38       share the credential cache between some or no containers by
39       bind-mounting the socket.
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41       The KCM default client idle timeout is 5 minutes, this allows more time
42       for user interaction with command line tools such as kinit.
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USING THE KCM CREDENTIAL CACHE

45       In order to use KCM credential cache, it must be selected as the
46       default credential type in krb5.conf(5), The credentials cache name
47       must be only “KCM:” without any template expansions. For example:
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49           [libdefaults]
50               default_ccache_name = KCM:
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53       Next, make sure the Kerberos client libraries and the KCM server must
54       agree on the UNIX socket path. By default, both use the same path
55       /var/run/.heim_org.h5l.kcm-socket. To configure the Kerberos library,
56       change its “kcm_socket” option which is described in the krb5.conf(5)
57       manual page.
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59       Finally, make sure the SSSD KCM server can be contacted. The KCM
60       service is typically socket-activated by systemd(1). Unlike other SSSD
61       services, it cannot be started by adding the “kcm” string to the
62       “service” directive.
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64           systemctl start sssd-kcm.socket
65           systemctl enable sssd-kcm.socket
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68       Please note your distribution may already configure the units for you.
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THE CREDENTIAL CACHE STORAGE

71       The credential caches are stored in a database, much like SSSD caches
72       user or group entries. The database is typically located at
73       “/var/lib/sss/secrets”.
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OBTAINING DEBUG LOGS

76       The sssd-kcm service is typically socket-activated systemd(1). To
77       generate debug logs, add the following either to the
78       /etc/sssd/sssd.conf file directly or as a configuration snippet to
79       /etc/sssd/conf.d/ directory:
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81           [kcm]
82           debug_level = 10
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85       Then, restart the sssd-kcm service:
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87           systemctl restart sssd-kcm.service
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89
90       Finally, run whatever use-case doesn't work for you. The KCM logs will
91       be generated at /var/log/sssd/sssd_kcm.log. It is recommended to
92       disable the debug logs when you no longer need the debugging to be
93       enabled as the sssd-kcm service can generate quite a large amount of
94       debugging information.
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96       Please note that configuration snippets are, at the moment, only
97       processed if the main configuration file at /etc/sssd/sssd.conf exists
98       at all.
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CONFIGURATION OPTIONS

101       The KCM service is configured in the “kcm” section of the sssd.conf
102       file. Please note that because the KCM service is typically
103       socket-activated, it is enough to just restart the “sssd-kcm” service
104       after changing options in the “kcm” section of sssd.conf:
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106           systemctl restart sssd-kcm.service
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109       The KCM service is configured in the “kcm” For a detailed syntax
110       reference, refer to the “FILE FORMAT” section of the sssd.conf(5)
111       manual page.
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113       The generic SSSD service options such as “debug_level” or “fd_limit”
114       are accepted by the kcm service. Please refer to the sssd.conf(5)
115       manual page for a complete list. In addition, there are some
116       KCM-specific options as well.
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118       socket_path (string)
119           The socket the KCM service will listen on.
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121           Default: /var/run/.heim_org.h5l.kcm-socket
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123           Note: on platforms where systemd is supported, the socket path is
124           overwritten by the one defined in the sssd-kcm.socket unit file.
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126       max_ccaches (integer)
127           How many credential caches does the KCM database allow for all
128           users.
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130           Default: 0 (unlimited, only the per-UID quota is enforced)
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132       max_uid_ccaches (integer)
133           How many credential caches does the KCM database allow per UID.
134           This is equivalent to “with how many principals you can kinit”.
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136           Default: 64
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138       max_ccache_size (integer)
139           How big can a credential cache be per ccache. Each service ticket
140           accounts into this quota.
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142           Default: 65536
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AUTHORS

148       The SSSD upstream - https://github.com/SSSD/sssd/
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152SSSD                              02/19/2021                       SSSD-KCM(8)