Merge pull request #26031 from nextcloud/feature/noid/allow-autocomplete-based-on-phone-sync

Allow autocomplete based on phone sync

10 files changed, 381 insertions, 58 deletions

diff --git a/lib/composer/composer/autoload_classmap.php b/lib/composer/composer/autoload_classmap.php
index 2e6b68f35bb..65f050ed265 100644
--- a/lib/composer/composer/autoload_classmap.php
+++ b/lib/composer/composer/autoload_classmap.php
@@ -948,6 +948,7 @@ return array(
     'OC\\Core\\Migrations\\Version21000Date20201120141228' => $baseDir . '/core/Migrations/Version21000Date20201120141228.php',
     'OC\\Core\\Migrations\\Version21000Date20201202095923' => $baseDir . '/core/Migrations/Version21000Date20201202095923.php',
     'OC\\Core\\Migrations\\Version21000Date20210119195004' => $baseDir . '/core/Migrations/Version21000Date20210119195004.php',
+    'OC\\Core\\Migrations\\Version21000Date20210309185126' => $baseDir . '/core/Migrations/Version21000Date20210309185126.php',
     'OC\\Core\\Migrations\\Version22000Date20210216080825' => $baseDir . '/core/Migrations/Version22000Date20210216080825.php',
     'OC\\Core\\Notification\\CoreNotifier' => $baseDir . '/core/Notification/CoreNotifier.php',
     'OC\\Core\\Service\\LoginFlowV2Service' => $baseDir . '/core/Service/LoginFlowV2Service.php',
@@ -1165,6 +1166,9 @@ return array(
     'OC\\IntegrityCheck\\Helpers\\FileAccessHelper' => $baseDir . '/lib/private/IntegrityCheck/Helpers/FileAccessHelper.php',
     'OC\\IntegrityCheck\\Iterator\\ExcludeFileByNameFilterIterator' => $baseDir . '/lib/private/IntegrityCheck/Iterator/ExcludeFileByNameFilterIterator.php',
     'OC\\IntegrityCheck\\Iterator\\ExcludeFoldersByPathFilterIterator' => $baseDir . '/lib/private/IntegrityCheck/Iterator/ExcludeFoldersByPathFilterIterator.php',
+    'OC\\KnownUser\\KnownUser' => $baseDir . '/lib/private/KnownUser/KnownUser.php',
+    'OC\\KnownUser\\KnownUserMapper' => $baseDir . '/lib/private/KnownUser/KnownUserMapper.php',
+    'OC\\KnownUser\\KnownUserService' => $baseDir . '/lib/private/KnownUser/KnownUserService.php',
     'OC\\L10N\\Factory' => $baseDir . '/lib/private/L10N/Factory.php',
     'OC\\L10N\\L10N' => $baseDir . '/lib/private/L10N/L10N.php',
     'OC\\L10N\\L10NString' => $baseDir . '/lib/private/L10N/L10NString.php',
diff --git a/lib/composer/composer/autoload_static.php b/lib/composer/composer/autoload_static.php
index 0a7ebd3ea38..de07f1831bb 100644
--- a/lib/composer/composer/autoload_static.php
+++ b/lib/composer/composer/autoload_static.php
@@ -977,6 +977,7 @@ class ComposerStaticInit53792487c5a8370acc0b06b1a864ff4c
         'OC\\Core\\Migrations\\Version21000Date20201120141228' => __DIR__ . '/../../..' . '/core/Migrations/Version21000Date20201120141228.php',
         'OC\\Core\\Migrations\\Version21000Date20201202095923' => __DIR__ . '/../../..' . '/core/Migrations/Version21000Date20201202095923.php',
         'OC\\Core\\Migrations\\Version21000Date20210119195004' => __DIR__ . '/../../..' . '/core/Migrations/Version21000Date20210119195004.php',
+        'OC\\Core\\Migrations\\Version21000Date20210309185126' => __DIR__ . '/../../..' . '/core/Migrations/Version21000Date20210309185126.php',
         'OC\\Core\\Migrations\\Version22000Date20210216080825' => __DIR__ . '/../../..' . '/core/Migrations/Version22000Date20210216080825.php',
         'OC\\Core\\Notification\\CoreNotifier' => __DIR__ . '/../../..' . '/core/Notification/CoreNotifier.php',
         'OC\\Core\\Service\\LoginFlowV2Service' => __DIR__ . '/../../..' . '/core/Service/LoginFlowV2Service.php',
@@ -1194,6 +1195,9 @@ class ComposerStaticInit53792487c5a8370acc0b06b1a864ff4c
         'OC\\IntegrityCheck\\Helpers\\FileAccessHelper' => __DIR__ . '/../../..' . '/lib/private/IntegrityCheck/Helpers/FileAccessHelper.php',
         'OC\\IntegrityCheck\\Iterator\\ExcludeFileByNameFilterIterator' => __DIR__ . '/../../..' . '/lib/private/IntegrityCheck/Iterator/ExcludeFileByNameFilterIterator.php',
         'OC\\IntegrityCheck\\Iterator\\ExcludeFoldersByPathFilterIterator' => __DIR__ . '/../../..' . '/lib/private/IntegrityCheck/Iterator/ExcludeFoldersByPathFilterIterator.php',
+        'OC\\KnownUser\\KnownUser' => __DIR__ . '/../../..' . '/lib/private/KnownUser/KnownUser.php',
+        'OC\\KnownUser\\KnownUserMapper' => __DIR__ . '/../../..' . '/lib/private/KnownUser/KnownUserMapper.php',
+        'OC\\KnownUser\\KnownUserService' => __DIR__ . '/../../..' . '/lib/private/KnownUser/KnownUserService.php',
         'OC\\L10N\\Factory' => __DIR__ . '/../../..' . '/lib/private/L10N/Factory.php',
         'OC\\L10N\\L10N' => __DIR__ . '/../../..' . '/lib/private/L10N/L10N.php',
         'OC\\L10N\\L10NString' => __DIR__ . '/../../..' . '/lib/private/L10N/L10NString.php',
diff --git a/lib/private/Collaboration/Collaborators/MailPlugin.php b/lib/private/Collaboration/Collaborators/MailPlugin.php
index 7bdd29afc4e..240e16374d5 100644
--- a/lib/private/Collaboration/Collaborators/MailPlugin.php
+++ b/lib/private/Collaboration/Collaborators/MailPlugin.php
@@ -27,6 +27,7 @@
 
 namespace OC\Collaboration\Collaborators;
 
+use OC\KnownUser\KnownUserService;
 use OCP\Collaboration\Collaborators\ISearchPlugin;
 use OCP\Collaboration\Collaborators\ISearchResult;
 use OCP\Collaboration\Collaborators\SearchResultType;
@@ -40,8 +41,16 @@ use OCP\IUserSession;
 use OCP\Share\IShare;
 
 class MailPlugin implements ISearchPlugin {
-	protected $shareeEnumeration;
+	/* @var bool */
 	protected $shareWithGroupOnly;
+	/* @var bool */
+	protected $shareeEnumeration;
+	/* @var bool */
+	protected $shareeEnumerationInGroupOnly;
+	/* @var bool */
+	protected $shareeEnumerationPhone;
+	/* @var bool */
+	protected $shareeEnumerationFullMatch;
 
 	/** @var IManager */
 	private $contactsManager;
@@ -52,20 +61,29 @@ class MailPlugin implements ISearchPlugin {
 
 	/** @var IGroupManager */
 	private $groupManager;
-
+	/** @var KnownUserService */
+	private $knownUserService;
 	/** @var IUserSession */
 	private $userSession;
 
-	public function __construct(IManager $contactsManager, ICloudIdManager $cloudIdManager, IConfig $config, IGroupManager $groupManager, IUserSession $userSession) {
+	public function __construct(IManager $contactsManager,
+								ICloudIdManager $cloudIdManager,
+								IConfig $config,
+								IGroupManager $groupManager,
+								KnownUserService $knownUserService,
+								IUserSession $userSession) {
 		$this->contactsManager = $contactsManager;
 		$this->cloudIdManager = $cloudIdManager;
 		$this->config = $config;
 		$this->groupManager = $groupManager;
+		$this->knownUserService = $knownUserService;
 		$this->userSession = $userSession;
 
 		$this->shareeEnumeration = $this->config->getAppValue('core', 'shareapi_allow_share_dialog_user_enumeration', 'yes') === 'yes';
 		$this->shareWithGroupOnly = $this->config->getAppValue('core', 'shareapi_only_share_with_group_members', 'no') === 'yes';
 		$this->shareeEnumerationInGroupOnly = $this->shareeEnumeration && $this->config->getAppValue('core', 'shareapi_restrict_user_enumeration_to_group', 'no') === 'yes';
+		$this->shareeEnumerationPhone = $this->shareeEnumeration && $this->config->getAppValue('core', 'shareapi_restrict_user_enumeration_to_phone', 'no') === 'yes';
+		$this->shareeEnumerationFullMatch = $this->config->getAppValue('core', 'shareapi_restrict_user_enumeration_full_match', 'yes') === 'yes';
 	}
 
 	/**
@@ -77,6 +95,8 @@ class MailPlugin implements ISearchPlugin {
 	 * @since 13.0.0
 	 */
 	public function search($search, $limit, $offset, ISearchResult $searchResult) {
+		$currentUserId = $this->userSession->getUser()->getUID();
+
 		$result = $userResults = ['wide' => [], 'exact' => []];
 		$userType = new SearchResultType('users');
 		$emailType = new SearchResultType('emails');
@@ -120,7 +140,7 @@ class MailPlugin implements ISearchPlugin {
 								continue;
 							}
 						}
-						if ($exactEmailMatch) {
+						if ($exactEmailMatch && $this->shareeEnumerationFullMatch) {
 							try {
 								$cloud = $this->cloudIdManager->resolveCloudId($contact['CLOUD'][0]);
 							} catch (\InvalidArgumentException $e) {
@@ -152,8 +172,12 @@ class MailPlugin implements ISearchPlugin {
 								continue;
 							}
 
-							$addToWide = !$this->shareeEnumerationInGroupOnly;
-							if ($this->shareeEnumerationInGroupOnly) {
+							$addToWide = !($this->shareeEnumerationInGroupOnly || $this->shareeEnumerationPhone);
+							if (!$addToWide && $this->shareeEnumerationPhone && $this->knownUserService->isKnownToUser($currentUserId, $contact['UID'])) {
+								$addToWide = true;
+							}
+
+							if (!$addToWide && $this->shareeEnumerationInGroupOnly) {
 								$addToWide = false;
 								$userGroups = $this->groupManager->getUserGroupIds($this->userSession->getUser());
 								foreach ($userGroups as $userGroup) {
@@ -181,7 +205,7 @@ class MailPlugin implements ISearchPlugin {
 					}
 
 					if ($exactEmailMatch
-						|| isset($contact['FN']) && strtolower($contact['FN']) === $lowerSearch) {
+						|| (isset($contact['FN']) && strtolower($contact['FN']) === $lowerSearch)) {
 						if ($exactEmailMatch) {
 							$searchResult->markExactIdMatch($emailType);
 						}
diff --git a/lib/private/Collaboration/Collaborators/UserPlugin.php b/lib/private/Collaboration/Collaborators/UserPlugin.php
index d832a42000c..06a8c6f0efd 100644
--- a/lib/private/Collaboration/Collaborators/UserPlugin.php
+++ b/lib/private/Collaboration/Collaborators/UserPlugin.php
@@ -32,6 +32,7 @@
 
 namespace OC\Collaboration\Collaborators;
 
+use OC\KnownUser\KnownUserService;
 use OCP\Collaboration\Collaborators\ISearchPlugin;
 use OCP\Collaboration\Collaborators\ISearchResult;
 use OCP\Collaboration\Collaborators\SearchResultType;
@@ -46,8 +47,14 @@ use OCP\UserStatus\IManager as IUserStatusManager;
 class UserPlugin implements ISearchPlugin {
 	/* @var bool */
 	protected $shareWithGroupOnly;
+	/* @var bool */
 	protected $shareeEnumeration;
+	/* @var bool */
 	protected $shareeEnumerationInGroupOnly;
+	/* @var bool */
+	protected $shareeEnumerationPhone;
+	/* @var bool */
+	protected $shareeEnumerationFullMatch;
 
 	/** @var IConfig */
 	private $config;
@@ -57,33 +64,30 @@ class UserPlugin implements ISearchPlugin {
 	private $userSession;
 	/** @var IUserManager */
 	private $userManager;
+	/** @var KnownUserService */
+	private $knownUserService;
 	/** @var IUserStatusManager */
 	private $userStatusManager;
 
-	/**
-	 * UserPlugin constructor.
-	 *
-	 * @param IConfig $config
-	 * @param IUserManager $userManager
-	 * @param IGroupManager $groupManager
-	 * @param IUserSession $userSession
-	 * @param IUserStatusManager $userStatusManager
-	 */
 	public function __construct(IConfig $config,
 								IUserManager $userManager,
 								IGroupManager $groupManager,
 								IUserSession $userSession,
+								KnownUserService $knownUserService,
 								IUserStatusManager $userStatusManager) {
 		$this->config = $config;
 
 		$this->groupManager = $groupManager;
 		$this->userSession = $userSession;
 		$this->userManager = $userManager;
+		$this->knownUserService = $knownUserService;
 		$this->userStatusManager = $userStatusManager;
 
 		$this->shareWithGroupOnly = $this->config->getAppValue('core', 'shareapi_only_share_with_group_members', 'no') === 'yes';
 		$this->shareeEnumeration = $this->config->getAppValue('core', 'shareapi_allow_share_dialog_user_enumeration', 'yes') === 'yes';
 		$this->shareeEnumerationInGroupOnly = $this->shareeEnumeration && $this->config->getAppValue('core', 'shareapi_restrict_user_enumeration_to_group', 'no') === 'yes';
+		$this->shareeEnumerationPhone = $this->shareeEnumeration && $this->config->getAppValue('core', 'shareapi_restrict_user_enumeration_to_phone', 'no') === 'yes';
+		$this->shareeEnumerationFullMatch = $this->config->getAppValue('core', 'shareapi_restrict_user_enumeration_full_match', 'yes') === 'yes';
 	}
 
 	public function search($search, $limit, $offset, ISearchResult $searchResult) {
@@ -91,6 +95,7 @@ class UserPlugin implements ISearchPlugin {
 		$users = [];
 		$hasMoreResults = false;
 
+		$currentUserId = $this->userSession->getUser()->getUID();
 		$currentUserGroups = $this->groupManager->getUserGroupIds($this->userSession->getUser());
 		if ($this->shareWithGroupOnly) {
 			// Search in all the groups this user is part of
@@ -148,6 +153,7 @@ class UserPlugin implements ISearchPlugin {
 
 
 			if (
+				$this->shareeEnumerationFullMatch &&
 				$lowerSearch !== '' && (strtolower($uid) === $lowerSearch ||
 				strtolower($userDisplayName) === $lowerSearch ||
 				strtolower($userEmail) === $lowerSearch)
@@ -168,11 +174,16 @@ class UserPlugin implements ISearchPlugin {
 				];
 			} else {
 				$addToWideResults = false;
-				if ($this->shareeEnumeration && !$this->shareeEnumerationInGroupOnly) {
+				if ($this->shareeEnumeration &&
+					!($this->shareeEnumerationInGroupOnly || $this->shareeEnumerationPhone)) {
+					$addToWideResults = true;
+				}
+
+				if ($this->shareeEnumerationPhone && $this->knownUserService->isKnownToUser($currentUserId, $user->getUID())) {
 					$addToWideResults = true;
 				}
 
-				if ($this->shareeEnumerationInGroupOnly) {
+				if (!$addToWideResults && $this->shareeEnumerationInGroupOnly) {
 					$commonGroups = array_intersect($currentUserGroups, $this->groupManager->getUserGroupIds($user));
 					if (!empty($commonGroups)) {
 						$addToWideResults = true;
@@ -195,7 +206,7 @@ class UserPlugin implements ISearchPlugin {
 			}
 		}
 
-		if ($offset === 0 && !$foundUserById) {
+		if ($this->shareeEnumerationFullMatch && $offset === 0 && !$foundUserById) {
 			// On page one we try if the search result has a direct hit on the
 			// user id and if so, we add that to the exact match list
 			$user = $this->userManager->get($search);
diff --git a/lib/private/Contacts/ContactsMenu/ContactsStore.php b/lib/private/Contacts/ContactsMenu/ContactsStore.php
index e2bd7edc63d..69f26c7969f 100644
--- a/lib/private/Contacts/ContactsMenu/ContactsStore.php
+++ b/lib/private/Contacts/ContactsMenu/ContactsStore.php
@@ -31,6 +31,7 @@
 
 namespace OC\Contacts\ContactsMenu;
 
+use OC\KnownUser\KnownUserService;
 use OCP\Contacts\ContactsMenu\IContactsStore;
 use OCP\Contacts\ContactsMenu\IEntry;
 use OCP\Contacts\IManager;
@@ -53,20 +54,19 @@ class ContactsStore implements IContactsStore {
 	/** @var IGroupManager */
 	private $groupManager;
 
-	/**
-	 * @param IManager $contactsManager
-	 * @param IConfig $config
-	 * @param IUserManager $userManager
-	 * @param IGroupManager $groupManager
-	 */
+	/** @var KnownUserService */
+	private $knownUserService;
+
 	public function __construct(IManager $contactsManager,
 								IConfig $config,
 								IUserManager $userManager,
-								IGroupManager $groupManager) {
+								IGroupManager $groupManager,
+								KnownUserService $knownUserService) {
 		$this->contactsManager = $contactsManager;
 		$this->config = $config;
 		$this->userManager = $userManager;
 		$this->groupManager = $groupManager;
+		$this->knownUserService = $knownUserService;
 	}
 
 	/**
@@ -103,7 +103,7 @@ class ContactsStore implements IContactsStore {
 	}
 
 	/**
-	 * Filters the contacts. Applies 3 filters:
+	 * Filters the contacts. Applied filters:
 	 *  1. filter the current user
 	 *  2. if the `shareapi_allow_share_dialog_user_enumeration` config option is
 	 * enabled it will filter all local users
@@ -122,20 +122,22 @@ class ContactsStore implements IContactsStore {
 									array $entries,
 									$filter) {
 		$disallowEnumeration = $this->config->getAppValue('core', 'shareapi_allow_share_dialog_user_enumeration', 'yes') !== 'yes';
-		$restrictEnumeration = $this->config->getAppValue('core', 'shareapi_restrict_user_enumeration_to_group', 'no') === 'yes';
+		$restrictEnumerationGroup = $this->config->getAppValue('core', 'shareapi_restrict_user_enumeration_to_group', 'no') === 'yes';
+		$restrictEnumerationPhone = $this->config->getAppValue('core', 'shareapi_restrict_user_enumeration_to_phone', 'no') === 'yes';
+		$allowEnumerationFullMatch = $this->config->getAppValue('core', 'shareapi_restrict_user_enumeration_full_match', 'yes') === 'yes';
 		$excludedGroups = $this->config->getAppValue('core', 'shareapi_exclude_groups', 'no') === 'yes';
 
 		// whether to filter out local users
 		$skipLocal = false;
-		// whether to filter out all users which doesn't have the same group as the current user
-		$ownGroupsOnly = $this->config->getAppValue('core', 'shareapi_only_share_with_group_members', 'no') === 'yes' || $restrictEnumeration;
+		// whether to filter out all users which don't have a common group as the current user
+		$ownGroupsOnly = $this->config->getAppValue('core', 'shareapi_only_share_with_group_members', 'no') === 'yes';
 
 		$selfGroups = $this->groupManager->getUserGroupIds($self);
 
 		if ($excludedGroups) {
 			$excludedGroups = $this->config->getAppValue('core', 'shareapi_exclude_groups_list', '');
 			$decodedExcludeGroups = json_decode($excludedGroups, true);
-			$excludeGroupsList = ($decodedExcludeGroups !== null) ? $decodedExcludeGroups : [];
+			$excludeGroupsList = $decodedExcludeGroups ?? [];
 
 			if (count(array_intersect($excludeGroupsList, $selfGroups)) !== 0) {
 				// a group of the current user is excluded -> filter all local users
@@ -145,47 +147,80 @@ class ContactsStore implements IContactsStore {
 
 		$selfUID = $self->getUID();
 
-		return array_values(array_filter($entries, function (IEntry $entry) use ($self, $skipLocal, $ownGroupsOnly, $selfGroups, $selfUID, $disallowEnumeration, $filter) {
-			if ($skipLocal && $entry->getProperty('isLocalSystemBook') === true) {
+		return array_values(array_filter($entries, function (IEntry $entry) use ($skipLocal, $ownGroupsOnly, $selfGroups, $selfUID, $disallowEnumeration, $restrictEnumerationGroup, $restrictEnumerationPhone, $allowEnumerationFullMatch, $filter) {
+			if ($entry->getProperty('UID') === $selfUID) {
 				return false;
 			}
 
-			// Prevent enumerating local users
-			if ($disallowEnumeration && $entry->getProperty('isLocalSystemBook')) {
-				$filterUser = true;
+			if ($entry->getProperty('isLocalSystemBook')) {
+				if ($skipLocal) {
+					return false;
+				}
+
+				$checkedCommonGroupAlready = false;
 
-				$mailAddresses = $entry->getEMailAddresses();
-				foreach ($mailAddresses as $mailAddress) {
-					if ($mailAddress === $filter) {
-						$filterUser = false;
-						break;
+				// Prevent enumerating local users
+				if ($disallowEnumeration) {
+					if (!$allowEnumerationFullMatch) {
+						return false;
 					}
-				}
 
-				if ($entry->getProperty('UID') && $entry->getProperty('UID') === $filter) {
-					$filterUser = false;
-				}
+					$filterOutUser = true;
 
-				if ($filterUser) {
-					return false;
-				}
-			}
+					$mailAddresses = $entry->getEMailAddresses();
+					foreach ($mailAddresses as $mailAddress) {
+						if ($mailAddress === $filter) {
+							$filterOutUser = false;
+							break;
+						}
+					}
 
-			if ($ownGroupsOnly && $entry->getProperty('isLocalSystemBook') === true) {
-				$uid = $this->userManager->get($entry->getProperty('UID'));
+					if ($entry->getProperty('UID') && $entry->getProperty('UID') === $filter) {
+						$filterOutUser = false;
+					}
 
-				if ($uid === null) {
-					return false;
+					if ($filterOutUser) {
+						return false;
+					}
+				} elseif ($restrictEnumerationPhone || $restrictEnumerationGroup) {
+					$canEnumerate = false;
+					if ($restrictEnumerationPhone) {
+						$canEnumerate = $this->knownUserService->isKnownToUser($selfUID, $entry->getProperty('UID'));
+					}
+
+					if (!$canEnumerate && $restrictEnumerationGroup) {
+						$user = $this->userManager->get($entry->getProperty('UID'));
+
+						if ($user === null) {
+							return false;
+						}
+
+						$contactGroups = $this->groupManager->getUserGroupIds($user);
+						$canEnumerate = !empty(array_intersect($contactGroups, $selfGroups));
+						$checkedCommonGroupAlready = true;
+					}
+
+					if (!$canEnumerate) {
+						return false;
+					}
 				}
 
-				$contactGroups = $this->groupManager->getUserGroupIds($uid);
-				if (count(array_intersect($contactGroups, $selfGroups)) === 0) {
-					// no groups in common, so shouldn't see the contact
-					return false;
+				if ($ownGroupsOnly && !$checkedCommonGroupAlready) {
+					$user = $this->userManager->get($entry->getProperty('UID'));
+
+					if (!$user instanceof IUser) {
+						return false;
+					}
+
+					$contactGroups = $this->groupManager->getUserGroupIds($user);
+					if (empty(array_intersect($contactGroups, $selfGroups))) {
+						// no groups in common, so shouldn't see the contact
+						return false;
+					}
 				}
 			}
 
-			return $entry->getProperty('UID') !== $selfUID;
+			return true;
 		}));
 	}
 
diff --git a/lib/private/KnownUser/KnownUser.php b/lib/private/KnownUser/KnownUser.php
new file mode 100644
index 00000000000..939c9199c79
--- /dev/null
+++ b/lib/private/KnownUser/KnownUser.php
@@ -0,0 +1,46 @@
+<?php
+
+declare(strict_types=1);
+/**
+ * @copyright Copyright (c) 2021 Joas Schilling <coding@schilljs.com>
+ *
+ * @license GNU AGPL version 3 or any later version
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+namespace OC\KnownUser;
+
+use OCP\AppFramework\Db\Entity;
+
+/**
+ * @method void setKnownTo(string $knownTo)
+ * @method string getKnownTo()
+ * @method void setKnownUser(string $knownUser)
+ * @method string getKnownUser()
+ */
+class KnownUser extends Entity {
+
+	/** @var string */
+	protected $knownTo;
+
+	/** @var string */
+	protected $knownUser;
+
+	public function __construct() {
+		$this->addType('knownTo', 'string');
+		$this->addType('knownUser', 'string');
+	}
+}
diff --git a/lib/private/KnownUser/KnownUserMapper.php b/lib/private/KnownUser/KnownUserMapper.php
new file mode 100644
index 00000000000..e77e4752702
--- /dev/null
+++ b/lib/private/KnownUser/KnownUserMapper.php
@@ -0,0 +1,87 @@
+<?php
+
+declare(strict_types=1);
+/**
+ * @copyright Copyright (c) 2021 Joas Schilling <coding@schilljs.com>
+ *
+ * @license GNU AGPL version 3 or any later version
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+namespace OC\KnownUser;
+
+use OCP\AppFramework\Db\QBMapper;
+use OCP\IDBConnection;
+
+/**
+ * @method KnownUser mapRowToEntity(array $row)
+ */
+class KnownUserMapper extends QBMapper {
+
+	/**
+	 * @param IDBConnection $db
+	 */
+	public function __construct(IDBConnection $db) {
+		parent::__construct($db, 'known_users', KnownUser::class);
+	}
+
+	/**
+	 * @param string $knownTo
+	 * @return int Number of deleted entities
+	 */
+	public function deleteKnownTo(string $knownTo): int {
+		$query = $this->db->getQueryBuilder();
+		$query->delete($this->getTableName())
+			->where($query->expr()->eq('known_to', $query->createNamedParameter($knownTo)));
+
+		return (int) $query->execute();
+	}
+
+	/**
+	 * @param string $knownUser
+	 * @return int Number of deleted entities
+	 */
+	public function deleteKnownUser(string $knownUser): int {
+		$query = $this->db->getQueryBuilder();
+		$query->delete($this->getTableName())
+			->where($query->expr()->eq('known_user', $query->createNamedParameter($knownUser)));
+
+		return (int) $query->execute();
+	}
+
+	/**
+	 * Returns all "known users" for the given "known to" user
+	 *
+	 * @param string $knownTo
+	 * @return KnownUser[]
+	 */
+	public function getKnownUsers(string $knownTo): array {
+		$query = $this->db->getQueryBuilder();
+		$query->select('*')
+			->from($this->getTableName())
+			->where($query->expr()->eq('known_to', $query->createNamedParameter($knownTo)));
+
+		return $this->findEntities($query);
+	}
+
+	public function createKnownUserFromRow(array $row): KnownUser {
+		return $this->mapRowToEntity([
+			'id' => $row['s_id'],
+			'known_to' => $row['known_to'],
+			'known_user' => $row['known_user'],
+		]);
+	}
+}
diff --git a/lib/private/KnownUser/KnownUserService.php b/lib/private/KnownUser/KnownUserService.php
new file mode 100644
index 00000000000..96af21c836f
--- /dev/null
+++ b/lib/private/KnownUser/KnownUserService.php
@@ -0,0 +1,87 @@
+<?php
+
+declare(strict_types=1);
+/**
+ * @copyright Copyright (c) 2021 Joas Schilling <coding@schilljs.com>
+ *
+ * @license GNU AGPL version 3 or any later version
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+namespace OC\KnownUser;
+
+class KnownUserService {
+	/** @var KnownUserMapper */
+	protected $mapper;
+	/** @var array */
+	protected $knownUsers = [];
+
+	public function __construct(KnownUserMapper $mapper) {
+		$this->mapper = $mapper;
+	}
+
+	/**
+	 * Delete all matches where the given user is the owner of the phonebook
+	 *
+	 * @param string $knownTo
+	 * @return int Number of deleted matches
+	 */
+	public function deleteKnownTo(string $knownTo): int {
+		return $this->mapper->deleteKnownTo($knownTo);
+	}
+
+	/**
+	 * Delete all matches where the given user is the one in the phonebook
+	 *
+	 * @param string $contactUserId
+	 * @return int Number of deleted matches
+	 */
+	public function deleteByContactUserId(string $contactUserId): int {
+		return $this->mapper->deleteKnownUser($contactUserId);
+	}
+
+	/**
+	 * Store a match because $knownTo has $contactUserId in his phonebook
+	 *
+	 * @param string $knownTo User id of the owner of the phonebook
+	 * @param string $contactUserId User id of the contact in the phonebook
+	 */
+	public function storeIsKnownToUser(string $knownTo, string $contactUserId): void {
+		$entity = new KnownUser();
+		$entity->setKnownTo($knownTo);
+		$entity->setKnownUser($contactUserId);
+		$this->mapper->insert($entity);
+	}
+
+	/**
+	 * Check if $contactUserId is in the phonebook of $knownTo
+	 *
+	 * @param string $knownTo User id of the owner of the phonebook
+	 * @param string $contactUserId User id of the contact in the phonebook
+	 * @return bool
+	 */
+	public function isKnownToUser(string $knownTo, string $contactUserId): bool {
+		if (!isset($this->knownUsers[$knownTo])) {
+			$entities = $this->mapper->getKnownUsers($knownTo);
+			$this->knownUsers[$knownTo] = [];
+			foreach ($entities as $entity) {
+				$this->knownUsers[$knownTo][$entity->getKnownUser()] = true;
+			}
+		}
+
+		return isset($this->knownUsers[$knownTo][$contactUserId]);
+	}
+}
diff --git a/lib/private/Share20/Manager.php b/lib/private/Share20/Manager.php
index 5c8dba5915a..ce1ec1d60f6 100644
--- a/lib/private/Share20/Manager.php
+++ b/lib/private/Share20/Manager.php
@@ -1829,6 +1829,15 @@ class Manager implements IManager {
 			$this->config->getAppValue('core', 'shareapi_restrict_user_enumeration_to_group', 'no') === 'yes';
 	}
 
+	public function limitEnumerationToPhone(): bool {
+		return $this->allowEnumeration() &&
+			$this->config->getAppValue('core', 'shareapi_restrict_user_enumeration_to_phone', 'no') === 'yes';
+	}
+
+	public function allowEnumerationFullMatch(): bool {
+		return $this->config->getAppValue('core', 'shareapi_restrict_user_enumeration_full_match', 'yes') === 'yes';
+	}
+
 	/**
 	 * Copied from \OC_Util::isSharingDisabledForUser
 	 *
diff --git a/lib/public/Share/IManager.php b/lib/public/Share/IManager.php
index 635ccc1483d..606e6429918 100644
--- a/lib/public/Share/IManager.php
+++ b/lib/public/Share/IManager.php
@@ -385,6 +385,22 @@ interface IManager {
 	public function limitEnumerationToGroups(): bool;
 
 	/**
+	 * Check if user enumeration is limited to the phonebook matches
+	 *
+	 * @return bool
+	 * @since 21.0.1
+	 */
+	public function limitEnumerationToPhone(): bool;
+
+	/**
+	 * Check if user enumeration is allowed to return on full match
+	 *
+	 * @return bool
+	 * @since 21.0.1
+	 */
+	public function allowEnumerationFullMatch(): bool;
+
+	/**
 	 * Check if sharing is disabled for the given user
 	 *
 	 * @param string $userId