Require the secret config to be configured

If it's not configured the instance will look like it is working but
various features will silently break (end to end encryption, setting
alternate email and probably more).

One issue is that changing the secret from empty to something will
break various other stuff (app token). I don't think there is a good way
to solve this issue other than breaking early instead of having to
handle a painful migration later on.

Signed-off-by: Carl Schwan <carl@carlschwan.eu>

.github/workflows/s3-external.yml

@@ -55,7 +55,7 @@ jobs:
           php -S localhost:8080 &
       - name: PHPUnit
         run: |
-          echo "<?php return ['run' => true,'hostname' => 'localhost','key' => 'minio','secret' => 'minio123', 'bucket' => 'bucket', 'port' => 9000, 'use_ssl' => false, 'autocreate' => true, 'use_path_style' => true];" > apps/${{ env.APP_NAME }}/tests/config.amazons3.php
+          echo "<?php return ['run' => true, 'secret' => 'actually-not-secret', 'hostname' => 'localhost','key' => 'minio','secret' => 'minio123', 'bucket' => 'bucket', 'port' => 9000, 'use_ssl' => false, 'autocreate' => true, 'use_path_style' => true];" > apps/${{ env.APP_NAME }}/tests/config.amazons3.php
           phpunit --configuration tests/phpunit-autotest-external.xml apps/files_external/tests/Storage/Amazons3Test.php
           phpunit --configuration tests/phpunit-autotest-external.xml apps/files_external/tests/Storage/VersionedAmazonS3Test.php
       - name: S3 logs

lib/private/legacy/OC_Util.php

@@ -969,6 +969,13 @@ public static function checkServer(\OC\SystemConfig $config) {
 			];
 		}
 
+		if ($config->getValue('secret', '') === '' && !\OC::$CLI) {
+			$errors[] = [
+				'error' => $l->t('The required \'secret\' config variable is not configued in the config.php file.'),
+				'hint' => $l->t('Please ask your server administrator to check the Nextcloud configuration.')
+			];
+		}
+
 		$errors = array_merge($errors, self::checkDatabaseVersion());
 
 		// Cache the result of this function

tests/travis/install.sh

@@ -44,6 +44,7 @@ echo "Using database $DATABASENAME"
 cat > ./tests/autoconfig-sqlite.php <<DELIM
 <?php
 \$AUTOCONFIG = array (
+  'secret' => 'actually-not-secret',
   'installed' => false,
   'dbtype' => 'sqlite',
   'dbtableprefix' => 'oc_',
@@ -56,6 +57,7 @@ DELIM
 cat > ./tests/autoconfig-mysql.php <<DELIM
 <?php
 \$AUTOCONFIG = array (
+  'secret' => 'actually-not-secret',
   'installed' => false,
   'dbtype' => 'mysql',
   'dbtableprefix' => 'oc_',
@@ -72,6 +74,7 @@ DELIM
 cat > ./tests/autoconfig-pgsql.php <<DELIM
 <?php
 \$AUTOCONFIG = array (
+  'secret' => 'actually-not-secret',
   'installed' => false,
   'dbtype' => 'pgsql',
   'dbtableprefix' => 'oc_',
@@ -88,6 +91,7 @@ DELIM
 cat > ./tests/autoconfig-oracle.php <<DELIM
 <?php
 \$AUTOCONFIG = array (
+  'secret' => 'actually-not-secret',
   'installed' => false,
   'dbtype' => 'oci',
   'dbtableprefix' => 'oc_',