Merge pull request #19569 from nextcloud/enh/noid/restrict-user-enumeration-to-groups

Restrict sharing user enumeration to groups

apps/dav/lib/CardDAV/SystemAddressbook.php

@@ -40,7 +40,9 @@ class SystemAddressbook extends AddressBook {
 	}
 
 	public function getChildren() {
-		if ($this->config->getAppValue('core', 'shareapi_allow_share_dialog_user_enumeration', 'yes') !== 'yes') {
+		$shareEnumeration = $this->config->getAppValue('core', 'shareapi_allow_share_dialog_user_enumeration', 'yes') === 'yes';
+		$restrictShareEnumeration = $this->config->getAppValue('core', 'shareapi_restrict_user_enumeration_to_group', 'yes') === 'yes';
+		if (!$shareEnumeration || ($shareEnumeration && $restrictShareEnumeration)) {
 			return [];
 		}
 

apps/dav/lib/Connector/Sabre/Principal.php

@@ -245,7 +245,8 @@ class Principal implements BackendInterface {
 			return [];
 		}
 
-		$allowEnumeration = $this->config->getAppValue('core', 'shareapi_allow_share_dialog_user_enumeration', 'yes') === 'yes';
+		$allowEnumeration = $this->shareManager->allowEnumeration();
+		$limitEnumeration = $this->shareManager->limitEnumerationToGroups();
 
 		// If sharing is restricted to group members only,
 		// return only members that have groups in common
@@ -259,6 +260,14 @@ class Principal implements BackendInterface {
 			$restrictGroups = $this->groupManager->getUserGroupIds($user);
 		}
 
+		$currentUserGroups = [];
+		if ($limitEnumeration) {
+			$currentUser = $this->userSession->getUser();
+			if ($currentUser) {
+				$currentUserGroups = $this->groupManager->getUserGroupIds($currentUser);
+			}
+		}
+
 		foreach ($searchProperties as $prop => $value) {
 			switch ($prop) {
 				case '{http://sabredav.org/ns}email-address':
@@ -270,6 +279,15 @@ class Principal implements BackendInterface {
 						});
 					}
 
+					if ($limitEnumeration) {
+						$users = \array_filter($users, function (IUser $user) use ($currentUserGroups, $value) {
+							return !empty(array_intersect(
+									$this->groupManager->getUserGroupIds($user),
+									$currentUserGroups
+								)) || $user->getEMailAddress() === $value;
+						});
+					}
+
 					$results[] = array_reduce($users, function(array $carry, IUser $user) use ($restrictGroups) {
 						// is sharing restricted to groups only?
 						if ($restrictGroups !== false) {
@@ -293,6 +311,15 @@ class Principal implements BackendInterface {
 						});
 					}
 
+					if ($limitEnumeration) {
+						$users = \array_filter($users, function (IUser $user) use ($currentUserGroups, $value) {
+							return !empty(array_intersect(
+									$this->groupManager->getUserGroupIds($user),
+									$currentUserGroups
+								)) || $user->getDisplayName() === $value;
+						});
+					}
+
 					$results[] = array_reduce($users, function(array $carry, IUser $user) use ($restrictGroups) {
 						// is sharing restricted to groups only?
 						if ($restrictGroups !== false) {

apps/dav/tests/unit/Connector/Sabre/PrincipalTest.php

@@ -431,10 +431,9 @@ class PrincipalTest extends TestCase {
 			->will($this->returnValue($sharingEnabled));
 
 		if ($sharingEnabled) {
-			$this->config->expects($this->once())
+			$this->shareManager->expects($this->once())
-				->method('getAppValue')
+				->method('allowEnumeration')
-				->with('core', 'shareapi_allow_share_dialog_user_enumeration', 'yes')
+				->willReturn(true);
-				->willReturn('yes');
 
 			$this->shareManager->expects($this->once())
 				->method('shareWithGroupMembersOnly')
@@ -526,10 +525,9 @@ class PrincipalTest extends TestCase {
 			->method('shareAPIEnabled')
 			->will($this->returnValue(true));
 
-		$this->config->expects($this->exactly(2))
+		$this->shareManager->expects($this->exactly(2))
-			->method('getAppValue')
+			->method('allowEnumeration')
-			->with('core', 'shareapi_allow_share_dialog_user_enumeration', 'yes')
+			->willReturn(true);
-			->willReturn('yes');
 
 		$this->shareManager->expects($this->exactly(2))
 			->method('shareWithGroupMembersOnly')
@@ -557,10 +555,9 @@ class PrincipalTest extends TestCase {
 			->method('shareAPIEnabled')
 			->will($this->returnValue(true));
 
-		$this->config->expects($this->once())
+		$this->shareManager->expects($this->once())
-			->method('getAppValue')
+			->method('allowEnumeration')
-			->with('core', 'shareapi_allow_share_dialog_user_enumeration', 'yes')
+			->willReturn(false);
-			->willReturn('no');
 
 		$this->shareManager->expects($this->once())
 			->method('shareWithGroupMembersOnly')
@@ -593,10 +590,9 @@ class PrincipalTest extends TestCase {
 			->method('shareAPIEnabled')
 			->will($this->returnValue(true));
 
-		$this->config->expects($this->once())
+		$this->shareManager->expects($this->once())
-			->method('getAppValue')
+			->method('allowEnumeration')
-			->with('core', 'shareapi_allow_share_dialog_user_enumeration', 'yes')
+			->willReturn(false);
-			->willReturn('no');
 
 		$this->shareManager->expects($this->once())
 			->method('shareWithGroupMembersOnly')
@@ -624,6 +620,128 @@ class PrincipalTest extends TestCase {
 			['{http://sabredav.org/ns}email-address' => 'user2@foo.bar']));
 	}
 
+	public function testSearchPrincipalWithEnumerationLimitedDisplayname() {
+		$this->shareManager->expects($this->at(0))
+			->method('shareAPIEnabled')
+			->will($this->returnValue(true));
+
+		$this->shareManager->expects($this->at(1))
+			->method('allowEnumeration')
+			->willReturn(true);
+
+		$this->shareManager->expects($this->at(2))
+			->method('limitEnumerationToGroups')
+			->willReturn(true);
+
+		$this->shareManager->expects($this->once())
+			->method('shareWithGroupMembersOnly')
+			->will($this->returnValue(false));
+
+		$user2 = $this->createMock(IUser::class);
+		$user2->method('getUID')->will($this->returnValue('user2'));
+		$user2->method('getDisplayName')->will($this->returnValue('User 2'));
+		$user2->method('getEMailAddress')->will($this->returnValue('user2@foo.bar'));
+		$user3 = $this->createMock(IUser::class);
+		$user3->method('getUID')->will($this->returnValue('user3'));
+		$user3->method('getDisplayName')->will($this->returnValue('User 22'));
+		$user3->method('getEMailAddress')->will($this->returnValue('user2@foo.bar123'));
+		$user4 = $this->createMock(IUser::class);
+		$user4->method('getUID')->will($this->returnValue('user4'));
+		$user4->method('getDisplayName')->will($this->returnValue('User 222'));
+		$user4->method('getEMailAddress')->will($this->returnValue('user2@foo.bar456'));
+
+
+		$this->userSession->expects($this->at(0))
+			->method('getUser')
+			->willReturn($user2);
+
+		$this->groupManager->expects($this->at(0))
+			->method('getUserGroupIds')
+			->willReturn(['group1']);
+		$this->groupManager->expects($this->at(1))
+			->method('getUserGroupIds')
+			->willReturn(['group1']);
+		$this->groupManager->expects($this->at(2))
+			->method('getUserGroupIds')
+			->willReturn(['group1']);
+		$this->groupManager->expects($this->at(3))
+			->method('getUserGroupIds')
+			->willReturn(['group2']);
+
+		$this->userManager->expects($this->at(0))
+			->method('searchDisplayName')
+			->with('User')
+			->willReturn([$user2, $user3, $user4]);
+
+
+		$this->assertEquals([
+			'principals/users/user2',
+			'principals/users/user3',
+		], $this->connector->searchPrincipals('principals/users',
+			['{DAV:}displayname' => 'User']));
+	}
+
+	public function testSearchPrincipalWithEnumerationLimitedMail() {
+		$this->shareManager->expects($this->at(0))
+			->method('shareAPIEnabled')
+			->will($this->returnValue(true));
+
+		$this->shareManager->expects($this->at(1))
+			->method('allowEnumeration')
+			->willReturn(true);
+
+		$this->shareManager->expects($this->at(2))
+			->method('limitEnumerationToGroups')
+			->willReturn(true);
+
+		$this->shareManager->expects($this->once())
+			->method('shareWithGroupMembersOnly')
+			->will($this->returnValue(false));
+
+		$user2 = $this->createMock(IUser::class);
+		$user2->method('getUID')->will($this->returnValue('user2'));
+		$user2->method('getDisplayName')->will($this->returnValue('User 2'));
+		$user2->method('getEMailAddress')->will($this->returnValue('user2@foo.bar'));
+		$user3 = $this->createMock(IUser::class);
+		$user3->method('getUID')->will($this->returnValue('user3'));
+		$user3->method('getDisplayName')->will($this->returnValue('User 22'));
+		$user3->method('getEMailAddress')->will($this->returnValue('user2@foo.bar123'));
+		$user4 = $this->createMock(IUser::class);
+		$user4->method('getUID')->will($this->returnValue('user4'));
+		$user4->method('getDisplayName')->will($this->returnValue('User 222'));
+		$user4->method('getEMailAddress')->will($this->returnValue('user2@foo.bar456'));
+
+
+		$this->userSession->expects($this->at(0))
+			->method('getUser')
+			->willReturn($user2);
+
+		$this->groupManager->expects($this->at(0))
+			->method('getUserGroupIds')
+			->willReturn(['group1']);
+		$this->groupManager->expects($this->at(1))
+			->method('getUserGroupIds')
+			->willReturn(['group1']);
+		$this->groupManager->expects($this->at(2))
+			->method('getUserGroupIds')
+			->willReturn(['group1']);
+		$this->groupManager->expects($this->at(3))
+			->method('getUserGroupIds')
+			->willReturn(['group2']);
+
+		$this->userManager->expects($this->at(0))
+			->method('getByEmail')
+			->with('user')
+			->willReturn([$user2, $user3, $user4]);
+
+
+		$this->assertEquals([
+			'principals/users/user2',
+			'principals/users/user3'
+		], $this->connector->searchPrincipals('principals/users',
+			['{http://sabredav.org/ns}email-address' => 'user']));
+	}
+
 	public function testFindByUriSharingApiDisabled() {
 		$this->shareManager->expects($this->once())
 			->method('shareApiEnabled')

apps/files_sharing/lib/Controller/ShareesAPIController.php

@@ -66,12 +66,6 @@ class ShareesAPIController extends OCSController {
 	/** @var IManager */
 	protected $shareManager;
 
-	/** @var bool */
-	protected $shareWithGroupOnly = false;
-
-	/** @var bool */
-	protected $shareeEnumeration = true;
-
 	/** @var int */
 	protected $offset = 0;
 
@@ -205,8 +199,6 @@ class ShareesAPIController extends OCSController {
 		}
 		sort($shareTypes);
 
-		$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->limit = (int) $perPage;
 		$this->offset = $perPage * ($page - 1);
 

apps/files_sharing/tests/Controller/ShareesAPIControllerTest.php

@@ -237,12 +237,10 @@ class ShareesAPIControllerTest extends TestCase {
 
 		/** @var IConfig|\PHPUnit_Framework_MockObject_MockObject $config */
 		$config = $this->createMock(IConfig::class);
-		$config->expects($this->exactly(3))
+		$config->expects($this->exactly(1))
 			->method('getAppValue')
 			->with($this->anything(), $this->anything(), $this->anything())
 			->willReturnMap([
-				['core', 'shareapi_only_share_with_group_members', 'no', $apiSetting],
-				['core', 'shareapi_allow_share_dialog_user_enumeration', 'yes', $enumSetting],
 				['files_sharing', 'lookupServerEnabled', 'yes', 'yes'],
 			]);
 
@@ -302,9 +300,6 @@ class ShareesAPIControllerTest extends TestCase {
 			}));
 
 		$this->assertInstanceOf(Http\DataResponse::class, $sharees->search($search, $itemType, $page, $perPage, $shareType));
-
-		$this->assertSame($shareWithGroupOnly, $this->invokePrivate($sharees, 'shareWithGroupOnly'));
-		$this->assertSame($shareeEnumeration, $this->invokePrivate($sharees, 'shareeEnumeration'));
 	}
 
 	public function dataSearchInvalid() {

apps/settings/js/admin.js

@@ -142,6 +142,10 @@ $(document).ready(function(){
 		savePublicShareDisclaimerText(this.value);
 	});
 
+	$('#shareapi_allow_share_dialog_user_enumeration').on('change', function() {
+		$('#shareapi_restrict_user_enumeration_to_group_setting').toggleClass('hidden', !this.checked);
+	})
+
 	$('#allowLinks').change(function() {
 		$("#publicLinkSettings").toggleClass('hidden', !this.checked);
 		$('#setDefaultExpireDate').toggleClass('hidden', !(this.checked && $('#shareapiDefaultExpireDate')[0].checked));

apps/settings/lib/Settings/Admin/Sharing.php

@@ -73,6 +73,7 @@ class Sharing implements ISettings {
 			'allowPublicUpload'                    => $this->config->getAppValue('core', 'shareapi_allow_public_upload', 'yes'),
 			'allowResharing'                       => $this->config->getAppValue('core', 'shareapi_allow_resharing', 'yes'),
 			'allowShareDialogUserEnumeration'      => $this->config->getAppValue('core', 'shareapi_allow_share_dialog_user_enumeration', 'yes'),
+			'restrictUserEnumerationToGroup'       => $this->config->getAppValue('core', 'shareapi_restrict_user_enumeration_to_group', 'no'),
 			'enforceLinkPassword'                  => Util::isPublicLinkPasswordRequired(),
 			'onlyShareWithGroupMembers'            => $this->shareManager->shareWithGroupMembersOnly(),
 			'shareAPIEnabled'                      => $this->config->getAppValue('core', 'shareapi_enabled', 'yes'),

apps/settings/templates/settings/admin/sharing.php

@@ -109,11 +109,19 @@
 		<br />
 		<em><?php p($l->t('These groups will still be able to receive shares, but not to initiate them.')); ?></em>
 	</p>
+
 	<p class="<?php if ($_['shareAPIEnabled'] === 'no') p('hidden');?>">
 		<input type="checkbox" name="shareapi_allow_share_dialog_user_enumeration" value="1" id="shareapi_allow_share_dialog_user_enumeration" class="checkbox"
 			<?php if ($_['allowShareDialogUserEnumeration'] === 'yes') print_unescaped('checked="checked"'); ?> />
 		<label for="shareapi_allow_share_dialog_user_enumeration"><?php p($l->t('Allow username autocompletion in share dialog. If this is disabled the full username or email address needs to be entered.'));?></label><br />
 	</p>
+
+	<p id="shareapi_restrict_user_enumeration_to_group_setting" class="indent <?php if ($_['shareAPIEnabled'] === 'no' || $_['allowShareDialogUserEnumeration'] === 'no') p('hidden');?>">
+		<input type="checkbox" name="shareapi_restrict_user_enumeration_to_group" value="1" id="shareapi_restrict_user_enumeration_to_group" class="checkbox"
+			<?php if ($_['restrictUserEnumerationToGroup'] === 'yes') print_unescaped('checked="checked"'); ?> />
+		<label for="shareapi_restrict_user_enumeration_to_group"><?php p($l->t('Restrict username autocompletion to users within the same groups'));?></label><br />
+	</p>
+
 	<p>
 		<input type="checkbox" id="publicShareDisclaimer" class="checkbox noJSAutoUpdate"
 			<?php if ($_['publicShareDisclaimerText'] !== null) print_unescaped('checked="checked"'); ?> />

apps/settings/tests/Settings/Admin/SharingTest.php

@@ -94,55 +94,60 @@ class SharingTest extends TestCase {
 		$this->config
 			->expects($this->at(6))
 			->method('getAppValue')
+			->with('core', 'shareapi_restrict_user_enumeration_to_group', 'no')
+			->willReturn('no');
+		$this->config
+			->expects($this->at(7))
+			->method('getAppValue')
 			->with('core', 'shareapi_enabled', 'yes')
 			->willReturn('yes');
 		$this->config
-			->expects($this->at(7))
+			->expects($this->at(8))
 			->method('getAppValue')
 			->with('core', 'shareapi_default_expire_date', 'no')
 			->willReturn('no');
 		$this->config
-			->expects($this->at(8))
+			->expects($this->at(9))
 			->method('getAppValue')
 			->with('core', 'shareapi_expire_after_n_days', '7')
 			->willReturn('7');
 		$this->config
-			->expects($this->at(9))
+			->expects($this->at(10))
 			->method('getAppValue')
 			->with('core', 'shareapi_enforce_expire_date', 'no')
 			->willReturn('no');
 		$this->config
-			->expects($this->at(10))
+			->expects($this->at(11))
 			->method('getAppValue')
 			->with('core', 'shareapi_exclude_groups', 'no')
 			->willReturn('no');
 		$this->config
-			->expects($this->at(11))
+			->expects($this->at(12))
 			->method('getAppValue')
 			->with('core', 'shareapi_public_link_disclaimertext', null)
 			->willReturn('Lorem ipsum');
 		$this->config
-			->expects($this->at(12))
+			->expects($this->at(13))
 			->method('getAppValue')
 			->with('core', 'shareapi_enable_link_password_by_default', 'no')
 			->willReturn('yes');
 		$this->config
-			->expects($this->at(13))
+			->expects($this->at(14))
 			->method('getAppValue')
 			->with('core', 'shareapi_default_permissions', Constants::PERMISSION_ALL)
 			->willReturn(Constants::PERMISSION_ALL);
 		$this->config
-			->expects($this->at(14))
+			->expects($this->at(15))
 			->method('getAppValue')
 			->with('core', 'shareapi_default_internal_expire_date', 'no')
 			->willReturn('no');
 		$this->config
-			->expects($this->at(15))
+			->expects($this->at(16))
 			->method('getAppValue')
 			->with('core', 'shareapi_internal_expire_after_n_days', '7')
 			->willReturn('7');
 		$this->config
-			->expects($this->at(16))
+			->expects($this->at(17))
 			->method('getAppValue')
 			->with('core', 'shareapi_enforce_internal_expire_date', 'no')
 			->willReturn('no');
@@ -156,6 +161,7 @@ class SharingTest extends TestCase {
 				'allowPublicUpload'               => 'yes',
 				'allowResharing'                  => 'yes',
 				'allowShareDialogUserEnumeration' => 'yes',
+				'restrictUserEnumerationToGroup'  => 'no',
 				'enforceLinkPassword'             => false,
 				'onlyShareWithGroupMembers'       => false,
 				'shareAPIEnabled'                 => 'yes',
@@ -212,55 +218,60 @@ class SharingTest extends TestCase {
 		$this->config
 			->expects($this->at(6))
 			->method('getAppValue')
+			->with('core', 'shareapi_restrict_user_enumeration_to_group', 'no')
+			->willReturn('no');
+		$this->config
+			->expects($this->at(7))
+			->method('getAppValue')
 			->with('core', 'shareapi_enabled', 'yes')
 			->willReturn('yes');
 		$this->config
-			->expects($this->at(7))
+			->expects($this->at(8))
 			->method('getAppValue')
 			->with('core', 'shareapi_default_expire_date', 'no')
 			->willReturn('no');
 		$this->config
-			->expects($this->at(8))
+			->expects($this->at(9))
 			->method('getAppValue')
 			->with('core', 'shareapi_expire_after_n_days', '7')
 			->willReturn('7');
 		$this->config
-			->expects($this->at(9))
+			->expects($this->at(10))
 			->method('getAppValue')
 			->with('core', 'shareapi_enforce_expire_date', 'no')
 			->willReturn('no');
 		$this->config
-			->expects($this->at(10))
+			->expects($this->at(11))
 			->method('getAppValue')
 			->with('core', 'shareapi_exclude_groups', 'no')
 			->willReturn('yes');
 		$this->config
-			->expects($this->at(11))
+			->expects($this->at(12))
 			->method('getAppValue')
 			->with('core', 'shareapi_public_link_disclaimertext', null)
 			->willReturn('Lorem ipsum');
 		$this->config
-			->expects($this->at(12))
+			->expects($this->at(13))
 			->method('getAppValue')
 			->with('core', 'shareapi_enable_link_password_by_default', 'no')
 			->willReturn('yes');
 		$this->config
-			->expects($this->at(13))
+			->expects($this->at(14))
 			->method('getAppValue')
 			->with('core', 'shareapi_default_permissions', Constants::PERMISSION_ALL)
 			->willReturn(Constants::PERMISSION_ALL);
 		$this->config
-			->expects($this->at(14))
+			->expects($this->at(15))
 			->method('getAppValue')
 			->with('core', 'shareapi_default_internal_expire_date', 'no')
 			->willReturn('no');
 		$this->config
-			->expects($this->at(15))
+			->expects($this->at(16))
 			->method('getAppValue')
 			->with('core', 'shareapi_internal_expire_after_n_days', '7')
 			->willReturn('7');
 		$this->config
-			->expects($this->at(16))
+			->expects($this->at(17))
 			->method('getAppValue')
 			->with('core', 'shareapi_enforce_internal_expire_date', 'no')
 			->willReturn('no');
@@ -275,6 +286,7 @@ class SharingTest extends TestCase {
 				'allowPublicUpload'               => 'yes',
 				'allowResharing'                  => 'yes',
 				'allowShareDialogUserEnumeration' => 'yes',
+				'restrictUserEnumerationToGroup'  => 'no',
 				'enforceLinkPassword'             => false,
 				'onlyShareWithGroupMembers'       => false,
 				'shareAPIEnabled'                 => 'yes',

lib/private/Collaboration/Collaborators/GroupPlugin.php

@@ -52,6 +52,7 @@ class GroupPlugin implements ISearchPlugin {
 
 		$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';
 	}
 
 	public function search($search, $limit, $offset, ISearchResult $searchResult) {
@@ -66,7 +67,7 @@ class GroupPlugin implements ISearchPlugin {
 		}
 
 		$userGroups =  [];
-		if (!empty($groups) && $this->shareWithGroupOnly) {
+		if (!empty($groups) && ($this->shareWithGroupOnly || $this->shareeEnumerationInGroupOnly)) {
 			// Intersect all the groups that match with the groups this user is a member of
 			$userGroups = $this->groupManager->getUserGroups($this->userSession->getUser());
 			$userGroups = array_map(function (IGroup $group) { return $group->getGID(); }, $userGroups);
@@ -93,6 +94,9 @@ class GroupPlugin implements ISearchPlugin {
 					],
 				];
 			} else {
+				if ($this->shareeEnumerationInGroupOnly && !in_array($group->getGID(), $userGroups, true)) {
+					continue;
+				}
 				$result['wide'][] = [
 					'label' => $group->getDisplayName(),
 					'value' => [

lib/private/Collaboration/Collaborators/MailPlugin.php

@@ -65,6 +65,8 @@ class MailPlugin implements ISearchPlugin {
 
 		$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';
+
 	}
 
 	/**
@@ -150,7 +152,18 @@ class MailPlugin implements ISearchPlugin {
 								continue;
 							}
 
-							if (!$this->isCurrentUser($cloud) && !$searchResult->hasResult($userType, $cloud->getUser())) {
+							$addToWide = !$this->shareeEnumerationInGroupOnly;
+							if ($this->shareeEnumerationInGroupOnly) {
+								$addToWide = false;
+								$userGroups = $this->groupManager->getUserGroupIds($this->userSession->getUser());
+								foreach ($userGroups as $userGroup) {
+									if ($this->groupManager->isInGroup($contact['UID'], $userGroup)) {
+										$addToWide = true;
+										break;
+									}
+								}
+							}
+							if ($addToWide && !$this->isCurrentUser($cloud) && !$searchResult->hasResult($userType, $cloud->getUser())) {
 								$userResults['wide'][] = [
 									'label' => $displayName,
 									'uuid' => $contact['UID'],
@@ -160,6 +173,7 @@ class MailPlugin implements ISearchPlugin {
 										'shareWith' => $cloud->getUser(),
 									],
 								];
+								continue;
 							}
 						}
 						continue;

lib/private/Collaboration/Collaborators/UserPlugin.php

@@ -36,11 +36,13 @@ use OCP\IUser;
 use OCP\IUserManager;
 use OCP\IUserSession;
 use OCP\Share;
+use OCP\Share\IShare;
 
 class UserPlugin implements ISearchPlugin {
 	/* @var bool */
 	protected $shareWithGroupOnly;
 	protected $shareeEnumeration;
+	protected $shareeEnumerationInGroupOnly;
 
 	/** @var IConfig */
 	private $config;
@@ -60,11 +62,13 @@ class UserPlugin implements ISearchPlugin {
 
 		$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';
 	}
 
 	public function search($search, $limit, $offset, ISearchResult $searchResult) {
 		$result = ['wide' => [], 'exact' => []];
 		$users = [];
+		$autoCompleteUsers = [];
 		$hasMoreResults = false;
 
 		$userGroups = [];
@@ -80,10 +84,32 @@ class UserPlugin implements ISearchPlugin {
 		} else {
 			// Search in all users
 			$usersTmp = $this->userManager->searchDisplayName($search, $limit, $offset);
-
+			$currentUserGroups = $this->groupManager->getUserGroupIds($this->userSession->getUser());
 			foreach ($usersTmp as $user) {
 				if ($user->isEnabled()) { // Don't keep deactivated users
 					$users[(string) $user->getUID()] = $user->getDisplayName();
+
+					$addToWideResults = false;
+					if ($this->shareeEnumeration && !$this->shareeEnumerationInGroupOnly) {
+						$addToWideResults = true;
+					}
+
+					if ($this->shareeEnumerationInGroupOnly) {
+						$commonGroups = array_intersect($currentUserGroups, $this->groupManager->getUserGroupIds($user));
+						if (!empty($commonGroups)) {
+							$addToWideResults = true;
+						}
+					}
+
+					if ($addToWideResults) {
+						$autoCompleteUsers[] = [
+							'label' => $user->getDisplayName(),
+							'value' => [
+								'shareType' => IShare::TYPE_USER,
+								'shareWith' => (string)$user->getUID(),
+							],
+						];
+					}
 				}
 			}
 		}
@@ -145,8 +171,9 @@ class UserPlugin implements ISearchPlugin {
 			}
 		}
 
-		if (!$this->shareeEnumeration) {
+		// overwrite wide matches if they are limited
-			$result['wide'] = [];
+		if (!$this->shareeEnumeration || $this->shareeEnumerationInGroupOnly) {
+			$result['wide'] = $autoCompleteUsers;
 		}
 
 		$type = new SearchResultType('users');

lib/private/Contacts/ContactsMenu/ContactsStore.php

@@ -107,12 +107,13 @@ 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', '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';
+		$ownGroupsOnly = $this->config->getAppValue('core', 'shareapi_only_share_with_group_members', 'no') === 'yes' || $restrictEnumeration;
 
 		$selfGroups = $this->groupManager->getUserGroupIds($self);
 

lib/private/Share20/Manager.php

@@ -1764,6 +1764,15 @@ class Manager implements IManager {
 		return $this->config->getAppValue('core', 'shareapi_allow_group_sharing', 'yes') === 'yes';
 	}
 
+	public function allowEnumeration(): bool {
+		return $this->config->getAppValue('core', 'shareapi_allow_share_dialog_user_enumeration', 'yes') === 'yes';
+	}
+
+	public function limitEnumerationToGroups(): bool {
+		return $this->allowEnumeration() &&
+			$this->config->getAppValue('core', 'shareapi_restrict_user_enumeration_to_group', 'no') === 'yes';
+	}
+
 	/**
 	 * Copied from \OC_Util::isSharingDisabledForUser
 	 *

lib/public/Share/IManager.php

@@ -368,6 +368,22 @@ interface IManager {
 	 */
 	public function allowGroupSharing();
 
+	/**
+	 * Check if user enumeration is allowed
+	 *
+	 * @return bool
+	 * @since 19.0.0
+	 */
+	public function allowEnumeration(): bool;
+
+	/**
+	 * Check if user enumeration is limited to the users groups
+	 *
+	 * @return bool
+	 * @since 19.0.0
+	 */
+	public function limitEnumerationToGroups(): bool;
+
 	/**
 	 * Check if sharing is disabled for the given user
 	 *

tests/lib/Collaboration/Collaborators/UserPluginTest.php

@@ -89,7 +89,27 @@ class UserPluginTest extends TestCase {
 		);
 	}
 
-	public function getUserMock($uid, $displayName, $enabled = true) {
+	public function mockConfig($shareWithGroupOnly, $shareeEnumeration, $shareeEnumerationLimitToGroup) {
+		$this->config->expects($this->any())
+			->method('getAppValue')
+			->willReturnCallback(
+				function($appName, $key, $default)
+				use ($shareWithGroupOnly, $shareeEnumeration, $shareeEnumerationLimitToGroup)
+				{
+					if ($appName === 'core' && $key === 'shareapi_only_share_with_group_members') {
+						return $shareWithGroupOnly ? 'yes' : 'no';
+					} else if ($appName === 'core' && $key === 'shareapi_allow_share_dialog_user_enumeration') {
+						return $shareeEnumeration ? 'yes' : 'no';
+					} else if ($appName === 'core' && $key === 'shareapi_restrict_user_enumeration_to_group') {
+						return $shareeEnumerationLimitToGroup ? 'yes' : 'no';
+					}
+					return $default;
+				}
+			);
+
+	}
+
+	public function getUserMock($uid, $displayName, $enabled = true, $groups = []) {
 		$user = $this->createMock(IUser::class);
 
 		$user->expects($this->any())
@@ -383,21 +403,7 @@ class UserPluginTest extends TestCase {
 		$reachedEnd,
 		$singleUser
 	) {
-		$this->config->expects($this->any())
+		$this->mockConfig($shareWithGroupOnly, $shareeEnumeration, false);
-			->method('getAppValue')
-			->willReturnCallback(
-				function($appName, $key, $default)
-				use ($shareWithGroupOnly, $shareeEnumeration)
-				{
-					if ($appName === 'core' && $key === 'shareapi_only_share_with_group_members') {
-						return $shareWithGroupOnly ? 'yes' : 'no';
-					} else if ($appName === 'core' && $key === 'shareapi_allow_share_dialog_user_enumeration') {
-						return $shareeEnumeration ? 'yes' : 'no';
-					}
-					return $default;
-				}
-			);
-
 		$this->instantiatePlugin();
 
 		$this->session->expects($this->any())
@@ -493,4 +499,110 @@ class UserPluginTest extends TestCase {
 		$this->plugin->takeOutCurrentUser($users);
 		$this->assertSame($expectedUIDs, array_keys($users));
 	}
+
+	public function dataSearchEnumeration() {
+		return [
+			[
+				'test',
+				['groupA'],
+				[
+					[ 'uid' => 'test1', 'groups' => ['groupA'] ],
+					[ 'uid' => 'test2', 'groups' => ['groupB'] ]
+				],
+				['test1']
+			],
+			[
+				'test',
+				['groupA'],
+				[
+					[ 'uid' => 'test1', 'groups' => ['groupA'] ],
+					[ 'uid' => 'test2', 'groups' => ['groupB', 'groupA'] ]
+				],
+				['test1', 'test2']
+			],
+			[
+				'test',
+				['groupA'],
+				[
+					[ 'uid' => 'test1', 'groups' => ['groupA', 'groupC'] ],
+					[ 'uid' => 'test2', 'groups' => ['groupB', 'groupA'] ]
+				],
+				['test1', 'test2']
+			],
+			[
+				'test',
+				['groupC', 'groupB'],
+				[
+					[ 'uid' => 'test1', 'groups' => ['groupA', 'groupC'] ],
+					[ 'uid' => 'test2', 'groups' => ['groupB', 'groupA'] ]
+				],
+				['test1', 'test2']
+			],
+			[
+				'test',
+				[],
+				[
+					[ 'uid' => 'test1', 'groups' => ['groupA'] ],
+					[ 'uid' => 'test2', 'groups' => ['groupB', 'groupA'] ]
+				],
+				[]
+			],
+			[
+				'test',
+				['groupC', 'groupB'],
+				[
+					[ 'uid' => 'test1', 'groups' => [] ],
+					[ 'uid' => 'test2', 'groups' => [] ]
+				],
+				[]
+			],
+		];
+	}
+
+	/**
+	 * @dataProvider dataSearchEnumeration
+	 */
+	public function testSearchEnumerationLimit($search, $userGroups, $matchingUsers, $result) {
+		$this->mockConfig(false, true, true);
+
+		$userResults = array_map(function ($user) {
+			return $this->getUserMock($user['uid'], $user['uid']);
+		}, $matchingUsers);
+
+		$mappedResult = array_map(function ($user) {
+			return ['label' => $user, 'value' => [ 'shareType' => 0, 'shareWith' => $user ]];
+		}, $result);
+
+		$this->userManager->expects($this->once())
+			->method('searchDisplayName')
+			->willReturn($userResults);
+		$this->session->expects($this->any())
+			->method('getUser')
+			->willReturn($this->getUserMock('test', 'foo'));
+		// current user
+		$this->groupManager->expects($this->at(0))
+			->method('getUserGroupIds')
+			->willReturn($userGroups);
+		$this->groupManager->expects($this->any())
+			->method('getUserGroupIds')
+			->willReturnCallback(function ($user) use ($matchingUsers) {
+				$neededObject = array_filter(
+					$matchingUsers,
+					function ($e) use ($user) {
+						return $user->getUID() === $e['uid'];
+					}
+				);
+				if (count($neededObject) > 0) {
+					return array_shift($neededObject)['groups'];
+				}
+				return [];
+			});
+
+		$this->instantiatePlugin();
+		$this->plugin->search($search, $this->limit, $this->offset, $this->searchResult);
+		$result = $this->searchResult->asArray();
+
+		$this->assertEquals([], $result['exact']['users']);
+		$this->assertEquals($mappedResult, $result['users']);
+	}
 }

tests/lib/Contacts/ContactsMenu/ContactsStoreTest.php

@@ -177,16 +177,21 @@ class ContactsStoreTest extends TestCase {
 			->willReturn('yes');
 
 		$this->config->expects($this->at(1))
+			->method('getAppValue')
+			->with($this->equalTo('core'), $this->equalTo('shareapi_restrict_user_enumeration_to_group'), $this->equalTo('yes'))
+			->willReturn('no');
+
+		$this->config->expects($this->at(2))
 			->method('getAppValue')
 			->with($this->equalTo('core'), $this->equalTo('shareapi_exclude_groups'), $this->equalTo('no'))
 			->willReturn('yes');
 
-		$this->config->expects($this->at(2))
+		$this->config->expects($this->at(3))
 			->method('getAppValue')
 			->with($this->equalTo('core'), $this->equalTo('shareapi_only_share_with_group_members'), $this->equalTo('no'))
 			->willReturn('yes');
 
-		$this->config->expects($this->at(3))
+		$this->config->expects($this->at(4))
 			->method('getAppValue')
 			->with($this->equalTo('core'), $this->equalTo('shareapi_exclude_groups_list'), $this->equalTo(''))
 			->willReturn('["group1", "group5", "group6"]');
@@ -223,16 +228,20 @@ class ContactsStoreTest extends TestCase {
 		$this->assertCount(0, $entries);
 	}
 
-	public function testGetContactsOnlyIfInTheSameGroup() {
+	public function testGetContactsOnlyShareIfInTheSameGroup() {
 		$this->config->expects($this->at(0))->method('getAppValue')
 			->with($this->equalTo('core'), $this->equalTo('shareapi_allow_share_dialog_user_enumeration'), $this->equalTo('yes'))
 			->willReturn('yes');
 
 		$this->config->expects($this->at(1)) ->method('getAppValue')
+			->with($this->equalTo('core'), $this->equalTo('shareapi_restrict_user_enumeration_to_group'), $this->equalTo('yes'))
+			->willReturn('no');
+
+		$this->config->expects($this->at(2)) ->method('getAppValue')
 			->with($this->equalTo('core'), $this->equalTo('shareapi_exclude_groups'), $this->equalTo('no'))
 			->willReturn('no');
 
-		$this->config->expects($this->at(2))
+		$this->config->expects($this->at(3))
 			->method('getAppValue')
 			->with($this->equalTo('core'), $this->equalTo('shareapi_only_share_with_group_members'), $this->equalTo('no'))
 			->willReturn('yes');
@@ -305,6 +314,92 @@ class ContactsStoreTest extends TestCase {
 		$this->assertEquals('contact', $entries[2]->getProperty('UID'));
 	}
 
+	public function testGetContactsOnlyEnumerateIfInTheSameGroup() {
+		$this->config->expects($this->at(0))->method('getAppValue')
+			->with($this->equalTo('core'), $this->equalTo('shareapi_allow_share_dialog_user_enumeration'), $this->equalTo('yes'))
+			->willReturn('yes');
+
+		$this->config->expects($this->at(1)) ->method('getAppValue')
+			->with($this->equalTo('core'), $this->equalTo('shareapi_restrict_user_enumeration_to_group'), $this->equalTo('yes'))
+			->willReturn('yes');
+
+		$this->config->expects($this->at(2)) ->method('getAppValue')
+			->with($this->equalTo('core'), $this->equalTo('shareapi_exclude_groups'), $this->equalTo('no'))
+			->willReturn('no');
+
+		$this->config->expects($this->at(3))
+			->method('getAppValue')
+			->with($this->equalTo('core'), $this->equalTo('shareapi_only_share_with_group_members'), $this->equalTo('no'))
+			->willReturn('no');
+
+		/** @var IUser|PHPUnit_Framework_MockObject_MockObject $currentUser */
+		$currentUser = $this->createMock(IUser::class);
+		$currentUser->expects($this->once())
+			->method('getUID')
+			->willReturn('user001');
+
+		$this->groupManager->expects($this->at(0))
+			->method('getUserGroupIds')
+			->with($this->equalTo($currentUser))
+			->willReturn(['group1', 'group2', 'group3']);
+
+		$user1 = $this->createMock(IUser::class);
+		$this->userManager->expects($this->at(0))
+			->method('get')
+			->with('user1')
+			->willReturn($user1);
+		$this->groupManager->expects($this->at(1))
+			->method('getUserGroupIds')
+			->with($this->equalTo($user1))
+			->willReturn(['group1']);
+		$user2 = $this->createMock(IUser::class);
+		$this->userManager->expects($this->at(1))
+			->method('get')
+			->with('user2')
+			->willReturn($user2);
+		$this->groupManager->expects($this->at(2))
+			->method('getUserGroupIds')
+			->with($this->equalTo($user2))
+			->willReturn(['group2', 'group3']);
+		$user3 = $this->createMock(IUser::class);
+		$this->userManager->expects($this->at(2))
+			->method('get')
+			->with('user3')
+			->willReturn($user3);
+		$this->groupManager->expects($this->at(3))
+			->method('getUserGroupIds')
+			->with($this->equalTo($user3))
+			->willReturn(['group8', 'group9']);
+
+		$this->contactsManager->expects($this->once())
+			->method('search')
+			->with($this->equalTo(''), $this->equalTo(['FN', 'EMAIL']))
+			->willReturn([
+				[
+					'UID' => 'user1',
+					'isLocalSystemBook' => true
+				],
+				[
+					'UID' => 'user2',
+					'isLocalSystemBook' => true
+				],
+				[
+					'UID' => 'user3',
+					'isLocalSystemBook' => true
+				],
+				[
+					'UID' => 'contact',
+				],
+			]);
+
+		$entries = $this->contactsStore->getContacts($currentUser, '');
+
+		$this->assertCount(3, $entries);
+		$this->assertEquals('user1', $entries[0]->getProperty('UID'));
+		$this->assertEquals('user2', $entries[1]->getProperty('UID'));
+		$this->assertEquals('contact', $entries[2]->getProperty('UID'));
+	}
+
 	public function testGetContactsWithFilter() {
 		$this->config->expects($this->at(0))->method('getAppValue')
 			->with($this->equalTo('core'), $this->equalTo('shareapi_allow_share_dialog_user_enumeration'), $this->equalTo('yes'))