Backport of #8197 to stable6

This extends mimetypes.list.php to be a white-list of known secure mime
types as well as offering secure alternatives for know potentially
malicious mime types.
I kept this in the OC_Helper and OC\Files\Type\Detection classes as
each backend has its own way of detecting mime types.

This supersedes #8184 as discussed in owncloud/security-tracker#56

4 files changed, 156 insertions, 89 deletions

diff --git a/lib/private/connector/sabre/file.php b/lib/private/connector/sabre/file.php
index ed27cef440d..d61d97938c7 100644
--- a/lib/private/connector/sabre/file.php
+++ b/lib/private/connector/sabre/file.php
@@ -199,11 +199,12 @@ class OC_Connector_Sabre_File extends OC_Connector_Sabre_Node implements Sabre_D
 	 */
 	public function getContentType() {
 		if (isset($this->fileinfo_cache['mimetype'])) {
-			return $this->fileinfo_cache['mimetype'];
+			$mimeType = $this->fileinfo_cache['mimetype'];
+		} else {
+			$mimeType = \OC\Files\Filesystem::getMimeType($this->path);
 		}
 
-		return \OC\Files\Filesystem::getMimeType($this->path);
-
+		return \OC_Helper::getSecureMimeType($mimeType);
 	}
 
 	private function createFileChunked($data)
diff --git a/lib/private/files/type/detection.php b/lib/private/files/type/detection.php
index d7cc9ebbf4e..f989000fa47 100644
--- a/lib/private/files/type/detection.php
+++ b/lib/private/files/type/detection.php
@@ -17,15 +17,22 @@ namespace OC\Files\Type;
  */
 class Detection {
 	protected $mimetypes = array();
+	protected $secureMimeTypes = array();
 
 	/**
-	 * add an extension -> mimetype mapping
+	 * Add an extension -> mimetype mapping
+	 *
+	 * $mimetype is the assumed correct mime type
+	 * The optional $secureMimeType is an alternative to send to send
+	 * to avoid potential XSS.
 	 *
 	 * @param string $extension
 	 * @param string $mimetype
+	 * @param string|null $secureMimeType
 	 */
-	public function registerType($extension, $mimetype) {
-		$this->mimetypes[$extension] = $mimetype;
+	public function registerType($extension, $mimetype, $secureMimeType = null) {
+		$this->mimetypes[$extension] = array($mimetype, $secureMimeType);
+		$this->secureMimeTypes[$mimetype] = $secureMimeType ?: $mimetype;
 	}
 
 	/**
@@ -35,6 +42,11 @@ class Detection {
 	 */
 	public function registerTypeArray($types) {
 		$this->mimetypes = array_merge($this->mimetypes, $types);
+
+		// Update the alternative mimetypes to avoid having to look them up each time.
+		foreach ($this->mimetypes as $mimeType) {
+			$this->secureMimeTypes[$mimeType[0]] = $mimeType[1] ?: $mimeType[0];
+		}
 	}
 
 	/**
@@ -48,8 +60,10 @@ class Detection {
 			//try to guess the type by the file extension
 			$extension = strtolower(strrchr(basename($path), "."));
 			$extension = substr($extension, 1); //remove leading .
-			return (isset($this->mimetypes[$extension])) ? $this->mimetypes[$extension] : 'application/octet-stream';
-		} else {
+			return (isset($this->mimetypes[$extension]) && isset($this->mimetypes[$extension][0]))
+				? $this->mimetypes[$extension][0]
+				: 'application/octet-stream';
+			} else {
 			return 'application/octet-stream';
 		}
 	}
@@ -122,4 +136,16 @@ class Detection {
 			return $mime;
 		}
 	}
+	
+	/**
+	 * Get a secure mimetype that won't expose potential XSS.
+	 *
+	 * @param string $mimeType
+	 * @return string
+	 */
+	public function getSecureMimeType($mimeType) {
+		return isset($this->secureMimeTypes[$mimeType])
+			? $this->secureMimeTypes[$mimeType]
+			: 'application/octet-stream';
+	}
 }
diff --git a/lib/private/helper.php b/lib/private/helper.php
index 29054f2980b..5182f57f797 100644
--- a/lib/private/helper.php
+++ b/lib/private/helper.php
@@ -399,6 +399,16 @@ class OC_Helper {
 	}
 
 	/**
+	 * Get a secure mimetype that won't expose potential XSS.
+	 *
+	 * @param string $mimeType
+	 * @return string
+	 */
+	static function getSecureMimeType($mimeType) {
+		return self::getMimetypeDetector()->getSecureMimeType($mimeType);
+	}
+	
+	/**
 	 * get the mimetype form a data string
 	 *
 	 * @param string $data
diff --git a/lib/private/mimetypes.list.php b/lib/private/mimetypes.list.php
index d68fe5b02f0..538fa385791 100644
--- a/lib/private/mimetypes.list.php
+++ b/lib/private/mimetypes.list.php
@@ -21,86 +21,116 @@
 */
 
 /**
- * list of mimetypes by extension
+ * Array mapping file extensions to mimetypes (in alphabetical order).
+ *
+ * The first index in the mime type array is the assumed correct mimetype
+ * and the second is either a secure alternative or null if the correct
+ * is considered secure.
  */
-
 return array(
-	'css'=>'text/css',
-	'flac'=>'audio/flac',
-	'gif'=>'image/gif',
-	'gzip'=>'application/x-gzip',
-	'gz'=>'application/x-gzip',
-	'html'=>'text/html',
-	'htm'=>'text/html',
-	'ics'=>'text/calendar',
-	'ical'=>'text/calendar',
-	'jpeg'=>'image/jpeg',
-	'jpg'=>'image/jpeg',
-	'js'=>'application/javascript',
-	'oga'=>'audio/ogg',
-	'ogg'=>'audio/ogg',
-	'ogv'=>'video/ogg',
-	'pdf'=>'application/pdf',
-	'png'=>'image/png',
-	'svg'=>'image/svg+xml',
-	'tar'=>'application/x-tar',
-	'tgz'=>'application/x-compressed',
-	'tar.gz'=>'application/x-compressed',
-	'tif'=>'image/tiff',
-	'tiff'=>'image/tiff',
-	'txt'=>'text/plain',
-	'zip'=>'application/zip',
-	'wav'=>'audio/wav',
-	'odt'=>'application/vnd.oasis.opendocument.text',
-	'ods'=>'application/vnd.oasis.opendocument.spreadsheet',
-	'odg'=>'application/vnd.oasis.opendocument.graphics',
-	'odp'=>'application/vnd.oasis.opendocument.presentation',
-	'pages'=>'application/x-iwork-pages-sffpages',
-	'numbers'=>'application/x-iwork-numbers-sffnumbers',
-	'keynote'=>'application/x-iwork-keynote-sffkey',
-	'kra'=>'application/x-krita',
-	'mp3'=>'audio/mpeg',
-	'doc'=>'application/msword',
-	'docx'=>'application/msword',
-	'xls'=>'application/msexcel',
-	'xlsx'=>'application/msexcel',
-	'php'=>'application/x-php',
-	'exe'=>'application/x-ms-dos-executable',
-	'msi'=>'application/x-msi',
-	'pl'=>'application/x-pearl',
-	'py'=>'application/x-python',
-	'blend'=>'application/x-blender',
-	'xcf'=>'application/x-gimp',
-	'psd'=>'application/x-photoshop',
-	'xml'=>'application/xml',
-	'avi'=>'video/x-msvideo',
-	'dv'=>'video/dv',
-	'm2t'=>'video/mp2t',
-	'mp4'=>'video/mp4',
-	'm4v'=>'video/mp4',
-	'mpg'=>'video/mpeg',
-	'mpeg'=>'video/mpeg',
-	'mov'=>'video/quicktime',
-	'webm'=>'video/webm',
-	'wmv'=>'video/x-ms-asf',
-	'py'=>'text/x-script.phyton',
-	'vcf' => 'text/vcard',
-	'vcard' => 'text/vcard',
-	'doc'=>'application/msword',
-	'docx'=>'application/vnd.openxmlformats-officedocument.wordprocessingml.document',
-	'xls'=>'application/msexcel',
-	'xlsx'=>'application/vnd.openxmlformats-officedocument.spreadsheetml.sheet',
-	'ppt'=>'application/mspowerpoint',
-	'pptx'=>'application/vnd.openxmlformats-officedocument.presentationml.presentation',
-	'sgf' => 'application/sgf',
-	'cdr' => 'application/coreldraw',
-	'impress' => 'text/impress',
-	'ai' => 'application/illustrator',
-	'epub' => 'application/epub+zip',
-	'mobi' => 'application/x-mobipocket-ebook',
-	'md' => 'text/markdown',
-	'markdown' => 'text/markdown',
-	'mdown' => 'text/markdown',
-	'mdwn' => 'text/markdown',
-	'reveal' => 'text/reveal'
-);
+	'7z' => array('application/x-7z-compressed', null),
+	'accdb' => array('application/msaccess', null),
+	'ai' => array('application/illustrator', null),
+	'avi' => array('video/x-msvideo', null),
+	'bash' => array('text/x-shellscript', null),
+	'blend' => array('application/x-blender', null),
+	'bin' => array('application/x-bin', null),
+	'bmp' => array('image/bmp', null),
+	'cb7' => array('application/x-cbr', null),
+	'cba' => array('application/x-cbr', null),
+	'cbr' => array('application/x-cbr', null),
+	'cbt' => array('application/x-cbr', null),
+	'cbtc' => array('application/x-cbr', null),
+	'cbz' => array('application/x-cbr', null),
+	'cc' => array('text/x-c', null),
+	'cdr' => array('application/coreldraw', null),
+	'cpp' => array('text/x-c++src', null),
+	'css' => array('text/css', null),
+	'csv' => array('text/csv', null),
+	'cvbdl' => array('application/x-cbr', null),
+	'c' => array('text/x-c', null),
+	'c++' => array('text/x-c++src', null),
+	'deb' => array('application/x-deb', null),
+	'doc' => array('application/msword', null),
+	'docx' => array('application/vnd.openxmlformats-officedocument.wordprocessingml.document', null),
+	'dot' => array('application/msword', null),
+	'dotx' => array('application/vnd.openxmlformats-officedocument.wordprocessingml.template', null),
+	'dv' => array('video/dv', null),
+	'eot' => array('application/vnd.ms-fontobject', null),
+	'epub' => array('application/epub+zip', null),
+	'exe' => array('application/x-ms-dos-executable', null),
+	'flac' => array('audio/flac', null),
+	'gif' => array('image/gif', null),
+	'gz' => array('application/x-gzip', null),
+	'gzip' => array('application/x-gzip', null),
+	'html' => array('text/html', 'text/plain'),
+	'htm' => array('text/html', 'text/plain'),
+	'ical' => array('text/calendar', null),
+	'ics' => array('text/calendar', null),
+	'impress' => array('text/impress', null),
+	'jpeg' => array('image/jpeg', null),
+	'jpg' => array('image/jpeg', null),
+	'js' => array('application/javascript', 'text/plain'),
+	'json' => array('application/json', 'text/plain'),
+	'keynote' => array('application/x-iwork-keynote-sffkey', null),
+	'kra' => array('application/x-krita', null),
+	'm2t' => array('video/mp2t', null),
+	'm4v' => array('video/mp4', null),
+	'markdown' => array('text/markdown', null),
+	'mdown' => array('text/markdown', null),
+	'md' => array('text/markdown', null),
+	'mdb' => array('application/msaccess', null),
+	'mdwn' => array('text/markdown', null),
+	'mkv' => array('video/x-matroska', null),
+	'mobi' => array('application/x-mobipocket-ebook', null),
+	'mov' => array('video/quicktime', null),
+	'mp3' => array('audio/mpeg', null),
+	'mp4' => array('video/mp4', null),
+	'mpeg' => array('video/mpeg', null),
+	'mpg' => array('video/mpeg', null),
+	'msi' => array('application/x-msi', null),
+	'numbers' => array('application/x-iwork-numbers-sffnumbers', null),
+	'odg' => array('application/vnd.oasis.opendocument.graphics', null),
+	'odp' => array('application/vnd.oasis.opendocument.presentation', null),
+	'ods' => array('application/vnd.oasis.opendocument.spreadsheet', null),
+	'odt' => array('application/vnd.oasis.opendocument.text', null),
+	'oga' => array('audio/ogg', null),
+	'ogg' => array('audio/ogg', null),
+	'ogv' => array('video/ogg', null),
+	'otf' => array('font/opentype', null),
+	'pages' => array('application/x-iwork-pages-sffpages', null),
+	'pdf' => array('application/pdf', null),
+	'php' => array('application/x-php', null),
+	'pl' => array('application/x-perl', null),
+	'png' => array('image/png', null),
+	'ppt' => array('application/mspowerpoint', null),
+	'pptx' => array('application/vnd.openxmlformats-officedocument.presentationml.presentation', null),
+	'psd' => array('application/x-photoshop', null),
+	'py' => array('text/x-python', null),
+	'rar' => array('application/x-rar-compressed', null),
+	'reveal' => array('text/reveal', null),
+	'sgf' => array('application/sgf', null),
+	'sh-lib' => array('text/x-shellscript', null),
+	'sh' => array('text/x-shellscript', null),
+	'svg' => array('image/svg+xml', 'text/plain'),
+	'swf' => array('application/x-shockwave-flash', 'application/octet-stream'),
+	'tar' => array('application/x-tar', null),
+	'tar.gz' => array('application/x-compressed', null),
+	'tex' => array('application/x-tex', null),
+	'tgz' => array('application/x-compressed', null),
+	'tiff' => array('image/tiff', null),
+	'tif' => array('image/tiff', null),
+	'ttf' => array('application/x-font-ttf', null),
+	'txt' => array('text/plain', null),
+	'vcard' => array('text/vcard', null),
+	'vcf' => array('text/vcard', null),
+	'wav' => array('audio/wav', null),
+	'webm' => array('video/webm', null),
+	'woff' => array('application/font-woff', null),
+	'wmv' => array('video/x-ms-asf', null),
+	'xcf' => array('application/x-gimp', null),
+	'xls' => array('application/msexcel', null),
+	'xlsx' => array('application/vnd.openxmlformats-officedocument.spreadsheetml.sheet', null),
+	'xml' => array('application/xml', 'text/plain'),
+	'zip' => array('application/zip', null),
+);
\ No newline at end of file