Theta42 Group & Permission Model

This is the canonical reference for how groups and permissions work across the theta42 suite (SSO Manager, Proxy, Jump-Host) and how downstream apps and Linux hosts should read and use them. It is written to be implementable by both humans and LLM agents.

Everything below assumes LDAP is the single source of truth for identity and group membership. Group membership is managed in the SSO Manager Directory, generated from adopted resources — there is no standalone "Groups" page.

1. Principles

1. Groups are a projection of the resource graph. Every adopted host and app in the Directory gets its own groups, auto-created from its identity. Group membership is managed on the resource's modal.
2. Two orthogonal resource namespaces: host and app. A host administers hosts; an app administers apps. They do not inherit from each other.
3. Three levels per resource: admin, access, and opaque capability. admin implies access. Capabilities are explicit and never implied by admin.
4. Multi-site by prefix. Each site's groups are fully independent, scoped by the site slug.
5. Hosts map, LDAP stays clean. Directory groups are groupOfNames (RBAC) with no gidNumber. A Linux host uses SSSD to import only the groups it needs and generate their GIDs on the fly (see §8) — no mass import, no GID bloat. Only the meta groups are never imported by hosts.
6. The directory is the only place groups are created. god_admin is the sole group that does not belong to a resource or site.

2. Group schema

S = site slug (see §7 for normalization). <host>/<app> = the resource slug. <capability> = an opaque, app-defined capability token (see §4).

Meta groups (implicit membership — not POSIX, no gidNumber)

These are resolved by the directory (any authenticated user passes), never enumerated as LDAP members, and cannot be used as Unix groups.

3. Naming, normalization & reserved rules

• The structural delimiter is _. It appears only between the fixed segments of a group name.
• Site, host, and app slugs never contain _. Normalize to lowercase; spaces and _ → -; strip other non-[a-z0-9-]. A host named Web 01 and a site Main Office produce slugs web-01 and main-office.
• Aggregate groups use the plural kind (hosts, apps); per-resource groups use the singular (host, app). This makes S_hosts_admin unambiguous even if a host were named admin (that host would be S_host_admin_admin).
• The last segment is the level. If it is admin or access it is a known level; any other value is an opaque capability owned by a downstream app.
• Total length budget: keep a group cn under ~120 chars; reject group creation that would exceed it.
• Groups are groupOfNames (RFC 2307bis) with no gidNumber. GIDs are generated on the host by SSSD for only the groups that host imports (see §8).

4. Levels and opaque capabilities

• admin — manage (create/update/delete/config) the resource.
• access — use/read the resource.
• <capability> — an arbitrary token the SSO does not interpret. The SSO manages membership and exposes the group to the app; the downstream app defines and enforces what the capability means (e.g. emby_admin, gitea_maintain, reboot, backup).

The directory recognizes admin, access, super_admin, and the meta groups. Everything else on a resource group is treated as an opaque capability group and passed through to consumers.

5. Permission resolution (inheritance)

Define a user's effective permission on a resource by checking, from most specific to most general, whether they are a member of any applicable group. The rule: a higher group implies everything below it.

On host H at site S

On app A at site S

Identical, with app/apps substituted for host/hosts.

Management console (SSO / Proxy / Jump-Host)

Each console is registered as an app on its site, so console admin is:

god_admin · S_super_admin · S_app_<console>_admin

Pseudocode

def effective(resource, level_or_cap, site):
    if user in "god_admin":                  return True
    if user in f"{site}_super_admin":        return True
    if level_or_cap in ("admin","access"):
        agg = f"{site}_{resource.kind}s_{level_or_cap}"
        if user in agg:                      return True
    specific = f"{site}_{resource.kind}_{resource.slug}_{level_or_cap}"
    if user in specific:                     return True
    if level_or_cap == "access":             return effective(resource, "admin", site)
    if level_or_cap == "admin":              return False          # access does not imply admin
    return False

everyone / S_everyone are a special grantee: if a resource grants a group to everyone (or S_everyone), any authenticated user (at that site) passes.

6. Where groups live — the Directory, generated from adopted resources

• There is no standalone Groups page. Group creation/management happens on an adopted resource in the Directory.
• When a host or app is adopted (promoted from Discovered Inventory to managed), the directory auto-creates its _admin and _access groups (and site aggregates if configured). Capability groups are created on demand.
• Membership (add/remove users) and capability grants are managed on that resource's modal.
• Deleting a resource removes its per-resource groups.
• The S_super_admin, S_hosts_*, S_apps_*, S_everyone site groups and the global god_admin/everyone are managed at the site level (not on a single host/app resource).

7. Multi-site isolation

One LDAP tree can serve many sites ("Main Office", "Branch Office", "co-lo", "Mikes Homelab", …). Each site S has its own fully independent set of S_* groups behind its prefix. A main-office_super_admin or main-office_hosts_admin touches nothing in branch-office_* or steves-homelab_*. Only god_admin and everyone cross site boundaries.

8. Unix/POSIX groups — mapped on the host, not in LDAP

Directory groups are groupOfNames (RFC 2307bis) and carry no gidNumber. There are hundreds of them and only a handful matter on any given host, so we do not bloat LDAP with GIDs. Instead, each Linux host uses SSSD to import only the groups it cares about and map them to GIDs on the fly (algorithmic ID mapping). This keeps the directory clean and the per-host surface tiny.

SSSD — generate GIDs on the fly, import only what you need

[domain/example]
id_provider = ldap
auth_provider = ldap
ldap_uri = ldaps://ldap.example
ldap_search_base = dc=example,dc=com

# groupOfNames (RFC 2307bis) schema
ldap_schema = rfc2307bis
ldap_group_object_class = groupOfNames
ldap_group_member = member

# Map GIDs mathematically from the LDAP UUID — no gidNumber in LDAP
ldap_id_mapping = true
ldap_group_uuid = entryUUID

# Import ONLY the groups this host needs (e.g. a naming convention or an OU)
ldap_group_search_filter = (&(objectClass=groupOfNames)(cn=linux-*))

Key ideas:

• ldap_id_mapping = true + ldap_group_uuid = entryUUID make SSSD derive a stable GID for any group it imports, so no gidNumber attribute is required in LDAP.
• ldap_group_search_filter is the gatekeeper: SSSD imports only groups that match, discarding the other hundreds. After changing the filter, clear the cache (sss_cache -E; rm -f /var/lib/sss/db/*; restart sssd) and verify with getent group <cn>.

What filter to use — the naming convention is the answer

A host should import its own resource groups (plus any explicitly granted ones). Because the schema is predictable, ldap-client can generate the per-host ldap_group_search_filter from the enrolled host's identity, e.g. a host web01 at site main-office imports:

(&(objectClass=groupOfNames)(|(cn=main-office_host_web01_access)
                               (cn=main-office_host_web01_admin)
                               (cn=main-office_host_web01_sudo)))

So the operator (or ldap-client) selects a small allowlist of the host's _access / _admin / capability groups to feed sudoers, SSH AllowGroups, and filesystem ACLs. Only those groups are imported — no GID bloat, no mass import.

Aliasing an LDAP group into a local group (e.g. input)

SSSD cannot merge an LDAP group into a local group whose GID varies per host. Two host-side mechanisms cover it:

• pam_exec — a script in the login stack adds the user to the local group for the session:

  #!/bin/bash
  if id -Gn "$PAM_USER" | grep -q "host_input"; then usermod -a -G input "$PAM_USER"; fi
  

  session optional pam_exec.so /usr/local/bin/add_to_input.sh in /etc/pam.d/common-session.

• nss-groupmerge — merge an LDAP group into a local group at NSS time (/etc/groupmerge.conf: input: host_input, then group: files sssd groupmerge in /etc/nsswitch.conf), so any service querying input sees the LDAP group's members regardless of the local GID.

Meta groups

god_admin, everyone, and S_everyone are NOT imported by hosts — they have implicit membership and are resolved by the directory only.

9. Downstream-app consumption guide

A downstream app (Emby, Gitea, a custom service, a shell script) reads group membership from LDAP and interprets it as follows:

1. Discover the user's groups — bind with the user's credentials (or use a service account + memberOf). Groups are groupOfNames (member DN), so query by the user's DN, e.g. (&(objectClass=groupOfNames)(member=<user_dn>)), or use the memberOf reverse attribute on the user's entry.
2. Match each group to a scope:
   • god_admin → the user is a global administrator.
   • {site}_super_admin → site administrator for that site.
   • {site}_hosts_* / {site}_app_* (aggregate) → applies to all hosts/apps at the site.
   • {site}_host_<host>_* / {site}_app_<app>_* → applies to that one resource.
   • everyone / {site}_everyone → the user is implicitly a member.
3. Interpret the last segment:
   • admin → full control of that resource.
   • access → read/use.
   • anything else → a capability you define; act on it or ignore it.
4. A user with {site}_host_web01_access can reach web01; a user with {site}_host_web01_reboot (if you define reboot) may reboot it; a user with {site}_app_emby_emby_admin administers Emby.

The app must never treat an unknown last segment as admin or access.

10. Migration from the legacy app_* groups

The current global groups (app_sso_admin, app_super_admin, app_sso_directory_admin, app_jump_admin) are replaced by the new model:

During the transition the legacy groups may be kept as short-lived aliases that resolve to the same effective permission; once everything is moved, remove them.

11. The management consoles are apps

The SSO, Proxy, and Jump-Host each register themselves as an app on their site and receive their auto-generated groups (S_app_sso_admin, S_app_proxy_admin, S_app_jump_admin, plus _access). Their admin UIs gate on god_admin · S_super_admin · S_app_<console>_admin. This keeps everything self-consistent: the SSO is "just another app."