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<ol class="chapter"><li class="chapter-item expanded "><a href="intro.html"><strong aria-hidden="true">1.</strong> Introduction to Kanidm</a></li><li class="chapter-item expanded "><a href="installing_the_server.html"><strong aria-hidden="true">2.</strong> Installing the Server</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="server_configuration.html"><strong aria-hidden="true">2.1.</strong> Server Configuration</a></li><li class="chapter-item expanded "><a href="security_hardening.html"><strong aria-hidden="true">2.2.</strong> Security Hardening</a></li></ol></li><li class="chapter-item expanded "><a href="client_tools.html"><strong aria-hidden="true">3.</strong> Client Tools</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="installing_client_tools.html"><strong aria-hidden="true">3.1.</strong> Installing client tools</a></li></ol></li><li class="chapter-item expanded "><a href="accounts_and_groups.html"><strong aria-hidden="true">4.</strong> Accounts and Groups</a></li><li class="chapter-item expanded "><a href="administrivia.html"><strong aria-hidden="true">5.</strong> Administrative Tasks</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="monitoring.html"><strong aria-hidden="true">5.1.</strong> Monitoring the platform</a></li><li class="chapter-item expanded "><a href="password_quality.html"><strong aria-hidden="true">5.2.</strong> Password Quality and Badlisting</a></li><li class="chapter-item expanded "><a href="posix_accounts.html" class="active"><strong aria-hidden="true">5.3.</strong> POSIX Accounts and Groups</a></li><li class="chapter-item expanded "><a href="ssh_key_dist.html"><strong aria-hidden="true">5.4.</strong> SSH Key Distribution</a></li><li class="chapter-item expanded "><a href="recycle_bin.html"><strong aria-hidden="true">5.5.</strong> The Recycle Bin</a></li></ol></li><li class="chapter-item expanded "><a href="oauth2.html"><strong aria-hidden="true">6.</strong> Oauth2</a></li><li class="chapter-item expanded "><a href="pam_and_nsswitch.html"><strong aria-hidden="true">7.</strong> PAM and nsswitch</a></li><li class="chapter-item expanded "><a href="radius.html"><strong aria-hidden="true">8.</strong> RADIUS</a></li><li class="chapter-item expanded "><a href="ldap.html"><strong aria-hidden="true">9.</strong> LDAP</a></li><li class="chapter-item expanded "><a href="why_tls.html"><strong aria-hidden="true">10.</strong> Why TLS?</a></li><li class="chapter-item expanded "><a href="DEVELOPER_README.html"><strong aria-hidden="true">11.</strong> Developer Guide</a></li></ol>
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<h1 id="posix-accounts-and-groups"><a class="header" href="#posix-accounts-and-groups">POSIX Accounts and Groups</a></h1>
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<p>Kanidm has features that enable its accounts and groups to be consumed on
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POSIX-like machines, such as Linux, FreeBSD, or others.</p>
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<h2 id="notes-on-posix-features"><a class="header" href="#notes-on-posix-features">Notes on POSIX Features</a></h2>
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<p>Many design decisions have been made in the POSIX features
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of Kanidm that are intended to make distributed systems easier to manage and
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client systems more secure.</p>
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<h3 id="uid-and-gid-numbers"><a class="header" href="#uid-and-gid-numbers">UID and GID Numbers</a></h3>
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<p>In Kanidm there is no difference between a UID and a GID number. On most UNIX systems
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a user will create all files with a primary user and group. The primary group is
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effectively equivalent to the permissions of the user. It is very easy to see scenarios
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where someone may change the account to have a shared primary group (ie <code>allusers</code>),
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but without changing the umask on all client systems. This can cause users' data to be
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compromised by any member of the same shared group.</p>
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<p>To prevent this, many systems create a "user private group", or UPG. This group has the
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GID number matching the UID of the user, and the user sets their primary
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group ID to the GID number of the UPG.</p>
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<p>As there is now an equivalence between the UID and GID number of the user and the UPG,
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there is no benefit in separating these values. As a result Kanidm accounts <em>only</em>
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have a GID number, which is also considered to be its UID number as well. This has the benefit
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of preventing the accidental creation of a separate group that has an overlapping GID number
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(the <code>uniqueness</code> attribute of the schema will block the creation).</p>
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<h3 id="upg-generation"><a class="header" href="#upg-generation">UPG Generation</a></h3>
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<p>Due to the requirement that a user have a UPG for security, many systems create these as
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two independent items. For example in /etc/passwd and /etc/group:</p>
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<pre><code># passwd
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william:x:654401105:654401105::/home/william:/bin/zsh
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# group
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william:x:654401105:
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</code></pre>
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<p>Other systems like FreeIPA use a plugin that generates a UPG as a database record on
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creation of the account.</p>
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<p>Kanidm does neither of these. As the GID number of the user must be unique, and a user
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implies the UPG must exist, we can generate UPG's on-demand from the account.
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This has a single side effect - that you are unable to add any members to a
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UPG - given the nature of a user private group, this is the point.</p>
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<h3 id="gid-number-generation"><a class="header" href="#gid-number-generation">GID Number Generation</a></h3>
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<p>In the future, Kanidm plans to have asynchronous replication as a feature between writable
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database servers. In this case, we need to be able to allocate stable and reliable
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GID numbers to accounts on replicas that may not be in continual communication.</p>
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<p>To do this, we use the last 32 bits of the account or group's UUID to
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generate the GID number.</p>
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<p>A valid concern is the possibility of duplication in the lower 32 bits. Given the
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birthday problem, if you have 77,000 groups and accounts, you have a 50% chance
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of duplication. With 50,000 you have a 20% chance, 9,300 you have a 1% chance and
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with 2900 you have a 0.1% chance.</p>
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<p>We advise that if you have a site with >10,000 users you should use an external system
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to allocate GID numbers serially or consistently to avoid potential duplication events.</p>
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<p>This design decision is made as most small sites will benefit greatly from the
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auto-allocation policy and the simplicity of its design, while larger enterprises
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will already have IDM or business process applications for HR/People that are
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capable of supplying this kind of data in batch jobs.</p>
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<h2 id="enabling-posix-attributes"><a class="header" href="#enabling-posix-attributes">Enabling POSIX Attributes</a></h2>
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<h3 id="enabling-posix-attributes-on-accounts"><a class="header" href="#enabling-posix-attributes-on-accounts">Enabling POSIX Attributes on Accounts</a></h3>
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<p>To enable POSIX account features and IDs on an account, you require the permission
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<code>idm_account_unix_extend_priv</code>. This is provided to <code>idm_admins</code> in the default database.</p>
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<p>You can then use the following command to enable POSIX extensions.</p>
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<pre><code>kanidm account posix set --name idm_admin <account_id> [--shell SHELL --gidnumber GID]
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kanidm account posix set --name idm_admin demo_user
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kanidm account posix set --name idm_admin demo_user --shell /bin/zsh
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kanidm account posix set --name idm_admin demo_user --gidnumber 2001
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</code></pre>
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<p>You can view the accounts POSIX token details with:</p>
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<pre><code>kanidm account posix show --name anonymous demo_user
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</code></pre>
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<h3 id="enabling-posix-attributes-on-groups"><a class="header" href="#enabling-posix-attributes-on-groups">Enabling POSIX Attributes on Groups</a></h3>
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<p>To enable POSIX group features and IDs on an account, you require the permission <code>idm_group_unix_extend_priv</code>.
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This is provided to <code>idm_admins</code> in the default database.</p>
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<p>You can then use the following command to enable POSIX extensions:</p>
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<pre><code>kanidm group posix set --name idm_admin <group_id> [--gidnumber GID]
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kanidm group posix set --name idm_admin demo_group
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kanidm group posix set --name idm_admin demo_group --gidnumber 2001
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</code></pre>
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<p>You can view the accounts POSIX token details with:</p>
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<pre><code>kanidm group posix show --name anonymous demo_group
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</code></pre>
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<p>POSIX-enabled groups will supply their members as POSIX members to clients. There is no
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special or separate type of membership for POSIX members required.</p>
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<h2 id="troubleshooting-common-issues"><a class="header" href="#troubleshooting-common-issues">Troubleshooting Common Issues</a></h2>
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<h3 id="subuid-conflicts-with-podman"><a class="header" href="#subuid-conflicts-with-podman">subuid conflicts with Podman</a></h3>
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<p>Due to the way that Podman operates, in some cases using the Kanidm client inside non-root containers
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with Kanidm accounts may fail with an error such as:</p>
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<pre><code>ERRO[0000] cannot find UID/GID for user NAME: No subuid ranges found for user "NAME" in /etc/subuid
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</code></pre>
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<p>This is a fault in Podman and how it attempts to provide non-root containers, when UID/GIDs
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are greater than 65535. In this case you may manually allocate your users GID number to be
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between 1000 - 65535, which may not trigger the fault.</p>
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