Add some generic default headers as well via PHP

.htaccess

@@ -1,11 +1,25 @@
 # Version: 8.1.0
+<IfModule mod_headers.c>
   <IfModule mod_fcgid.c>
     <IfModule mod_setenvif.c>
-<IfModule mod_headers.c>
        SetEnvIfNoCase ^Authorization$ "(.+)" XAUTHORIZATION=$1
        RequestHeader set XAuthorization %{XAUTHORIZATION}e env=XAUTHORIZATION
     </IfModule>
   </IfModule>
+
+  <IfModule mod_env.c>
+    # Add security and privacy related headers
+    Header set X-Content-Type-Options "nosniff"
+    Header set X-XSS-Protection "1; mode=block"
+    Header set X-Robots-Tag "none"
+    Header set X-Frame-Options "SAMEORIGIN"
+    SetEnv modHeadersAvailable true
+  </IfModule>
+
+  # Add cache control for CSS and JS files
+  <FilesMatch "\.(css|js)$">
+    Header set Cache-Control "max-age=7200, public"
+  </FilesMatch>
 </IfModule>
 <IfModule mod_php5.c>
 php_value upload_max_filesize 513M
@@ -44,12 +58,3 @@ Options -Indexes
 <IfModule pagespeed_module>
   ModPagespeed Off
 </IfModule>
-<IfModule mod_headers.c>
-  Header set X-Content-Type-Options "nosniff"
-  Header set X-XSS-Protection "1; mode=block"
-  Header set X-Robots-Tag "none"
-  Header set X-Frame-Options "SAMEORIGIN"
-  <FilesMatch "\.(css|js)$">
-    Header set Cache-Control "max-age=7200, public"
-  </FilesMatch>
-</IfModule>

core/js/setupchecks.js

@@ -115,9 +115,9 @@
 				};
 
 				for (var header in securityHeaders) {
-					if(xhr.getResponseHeader(header) !== securityHeaders[header]) {
+					if(!xhr.getResponseHeader(header) || xhr.getResponseHeader(header).toLowerCase() !== securityHeaders[header].toLowerCase()) {
 						messages.push(
-							t('core', 'The "{header}" HTTP header is not configured to equal to "{expected}". This is a potential security risk and we recommend adjusting this setting.', {header: header, expected: securityHeaders[header]})
+							t('core', 'The "{header}" HTTP header is not configured to equal to "{expected}". This is a potential security or privacy risk and we recommend adjusting this setting.', {header: header, expected: securityHeaders[header]})
 						);
 					}
 				}

core/js/tests/specs/setupchecksSpec.js

@@ -140,7 +140,7 @@ describe('OC.SetupChecks tests', function() {
 			);
 
 			async.done(function( data, s, x ){
-				expect(data).toEqual(['The "X-XSS-Protection" HTTP header is not configured to equal to "1; mode=block". This is a potential security risk and we recommend adjusting this setting.', 'The "X-Content-Type-Options" HTTP header is not configured to equal to "nosniff". This is a potential security risk and we recommend adjusting this setting.', 'The "X-Robots-Tag" HTTP header is not configured to equal to "none". This is a potential security risk and we recommend adjusting this setting.', 'The "X-Frame-Options" HTTP header is not configured to equal to "SAMEORIGIN". This is a potential security risk and we recommend adjusting this setting.']);
+				expect(data).toEqual(['The "X-XSS-Protection" HTTP header is not configured to equal to "1; mode=block". This is a potential security or privacy risk and we recommend adjusting this setting.', 'The "X-Content-Type-Options" HTTP header is not configured to equal to "nosniff". This is a potential security or privacy risk and we recommend adjusting this setting.', 'The "X-Robots-Tag" HTTP header is not configured to equal to "none". This is a potential security or privacy risk and we recommend adjusting this setting.', 'The "X-Frame-Options" HTTP header is not configured to equal to "SAMEORIGIN". This is a potential security or privacy risk and we recommend adjusting this setting.']);
 				done();
 			});
 		});
@@ -155,12 +155,11 @@ describe('OC.SetupChecks tests', function() {
 					'X-Robots-Tag': 'none',
 					'X-Frame-Options': 'SAMEORIGIN',
 					'Strict-Transport-Security': '2678400'
-
 				}
 			);
 
 			async.done(function( data, s, x ){
-				expect(data).toEqual(['The "X-XSS-Protection" HTTP header is not configured to equal to "1; mode=block". This is a potential security risk and we recommend adjusting this setting.', 'The "X-Content-Type-Options" HTTP header is not configured to equal to "nosniff". This is a potential security risk and we recommend adjusting this setting.']);
+				expect(data).toEqual(['The "X-XSS-Protection" HTTP header is not configured to equal to "1; mode=block". This is a potential security or privacy risk and we recommend adjusting this setting.', 'The "X-Content-Type-Options" HTTP header is not configured to equal to "nosniff". This is a potential security or privacy risk and we recommend adjusting this setting.']);
 				done();
 			});
 		});

lib/private/response.php

@@ -229,6 +229,15 @@ class OC_Response {
 			. 'media-src *; ' 
 			. 'connect-src *';
 		header('Content-Security-Policy:' . $policy);
+
+		// Send fallback headers for installations that don't have the possibility to send
+		// custom headers on the webserver side
+		if(getenv('modHeadersAvailable') !== 'true') {
+			header('X-XSS-Protection: 1; mode=block'); // Enforce browser based XSS filters
+			header('X-Content-Type-Options: nosniff'); // Disable sniffing the content type for IE
+			header('X-Frame-Options: Sameorigin'); // Disallow iFraming from other domains
+			header('X-Robots-Tag: none'); // https://developers.google.com/webmasters/control-crawl-index/docs/robots_meta_tag
+		}
 	}
 
 }

settings/templates/admin.php

@@ -444,6 +444,7 @@ if ($_['cronErrors']) {
 		<li><a target="_blank" href="<?php p(link_to_docs('admin-performance')); ?>"><?php p($l->t('Performance tuning'));?> ↗</a></li>
 		<li><a target="_blank" href="<?php p(link_to_docs('admin-config')); ?>"><?php p($l->t('Improving the config.php'));?> ↗</a></li>
 		<li><a target="_blank" href="<?php p(link_to_docs('developer-theming')); ?>"><?php p($l->t('Theming'));?> ↗</a></li>
+		<li><a target="_blank" href="<?php p(link_to_docs('admin-security')); ?>"><?php p($l->t('Hardening and security guidance'));?> ↗</a></li>
 	</ul>
 </div>