[Web][Dovecot][SOGo][DockerApi] Add mailbox groups, shared mailboxes and identity provider sync

data/web/inc/lib/mailcow/Identity/Service/LinkService.php

@@ -0,0 +1,51 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Mailcow\Identity\Service;
+
+use Mailcow\Identity\Repository\IdentityRepository;
+
+/**
+ * Links of mailboxes to IdP users, checked at IdP logins (REST, LDAP bind, OIDC). Mailboxes are found by email,
+ * so the IdP user id has to match the link: an address taken over by another IdP user must not open the old
+ * mailbox. Unlinked mailboxes are linked on their first login.
+ */
+class LinkService
+{
+    public function __construct(private IdentityRepository $repo)
+    {
+    }
+
+    /** The IdP user may log in to the mailbox; links the mailbox when it has no link yet */
+    public function verify(string $provider, string $username, string $externalId): bool
+    {
+        if ($externalId === '') {
+            return false;
+        }
+        $link = $this->repo->findLink($username);
+        if ($link !== null && $link['provider'] === $provider && $link['external_id'] !== null) {
+            return hash_equals((string)$link['external_id'], $externalId);
+        }
+        if (!$this->mayCreate($provider, $username, $externalId)) {
+            return false;
+        }
+        $this->repo->link($username, $provider, $externalId);
+        return true;
+    }
+
+    /** The IdP user owns no other mailbox (checked before a mailbox is created on login) */
+    public function mayCreate(string $provider, string $username, string $externalId): bool
+    {
+        $owner = ($externalId === '') ? null : $this->repo->usernameOf($provider, $externalId);
+        return $externalId !== '' && ($owner === null || $owner === $username);
+    }
+
+    /** Links a mailbox created on login */
+    public function link(string $provider, string $username, string $externalId): void
+    {
+        if ($externalId !== '') {
+            $this->repo->link($username, $provider, $externalId);
+        }
+    }
+}