From 4e00237cc43542abd72d69bbf03bcd738a16af48 Mon Sep 17 00:00:00 2001
From: Aleksander Machniak <alec@alec.pl>
Date: Sun, 7 Jun 2020 10:45:33 +0200
Subject: [PATCH] Allow opening application/octet-stream attachments according
 to filename extension (#6821)

---
 CHANGELOG                            |  1 +
 program/lib/Roundcube/rcube_mime.php | 44 +++++++++++++++++++---------
 program/steps/mail/get.inc           |  4 +--
 program/steps/mail/show.inc          |  6 +++-
 4 files changed, 38 insertions(+), 17 deletions(-)

diff --git a/CHANGELOG b/CHANGELOG
index d0f5b1b5b..e13507722 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -8,6 +8,7 @@ CHANGELOG Roundcube Webmail
 - MySQL: Use utf8mb4 charset and utf8mb4_unicode_ci collation (#6535, #7113)
 - Support for language codes up to 16 chars long (e.g. es-419) in database schema (#6851)
 - Relaxed domain name validation for extended TLDs support (#5588)
+- Allow opening application/octet-stream attachments according to filename extension (#6821)
 - Added support for INSERT OR REPLACE queries (#6771)
 - Extract RFC2231 attachment name from message headers (#6729, #6783)
 - Archive: Added options to split archive by year or year+month and folder (#7216)
diff --git a/program/lib/Roundcube/rcube_mime.php b/program/lib/Roundcube/rcube_mime.php
index 7d75d6b00..e0204d545 100644
--- a/program/lib/Roundcube/rcube_mime.php
+++ b/program/lib/Roundcube/rcube_mime.php
@@ -699,7 +699,7 @@ class rcube_mime
      * @param string  $name        File name (with suffix)
      * @param string  $failover    Mime type supplied for failover
      * @param boolean $is_stream   Set to True if $path contains file contents
-     * @param boolean $skip_suffix Set to True if the config/mimetypes.php mappig should be ignored
+     * @param boolean $skip_suffix Set to True if the config/mimetypes.php map should be ignored
      *
      * @return string
      * @author Till Klampaeckel <till@php.net>
@@ -708,22 +708,12 @@ class rcube_mime
      */
     public static function file_content_type($path, $name, $failover = 'application/octet-stream', $is_stream = false, $skip_suffix = false)
     {
-        static $mime_ext = array();
-
         $mime_type = null;
         $config    = rcube::get_instance()->config;
 
-        if (!$skip_suffix && empty($mime_ext)) {
-            foreach ($config->resolve_paths('mimetypes.php') as $fpath) {
-                $mime_ext = array_merge($mime_ext, (array) @include($fpath));
-            }
-        }
-
-        // use file name suffix with hard-coded mime-type map
-        if (!$skip_suffix && is_array($mime_ext) && $name) {
-            if ($suffix = substr($name, strrpos($name, '.')+1)) {
-                $mime_type = $mime_ext[strtolower($suffix)];
-            }
+        // Detect mimetype using filename extension
+        if (!$skip_suffix) {
+            $mime_type = self::file_ext_type($name);
         }
 
         // try fileinfo extension if available
@@ -758,6 +748,32 @@ class rcube_mime
         return $mime_type;
     }
 
+    /**
+     * File type detection based on file name only.
+     *
+     * @param string $filename Path to the file or file contents
+     *
+     * @return string|null Mimetype label
+     */
+    public static function file_ext_type($filename)
+    {
+        static $mime_ext = array();
+
+        if (empty($mime_ext)) {
+            foreach (rcube::get_instance()->config->resolve_paths('mimetypes.php') as $fpath) {
+                $mime_ext = array_merge($mime_ext, (array) @include($fpath));
+            }
+        }
+
+        // use file name suffix with hard-coded mime-type map
+        if (!empty($mime_ext) && $filename) {
+            $ext = strtolower(pathinfo($filename, PATHINFO_EXTENSION));
+            if ($ext && !empty($mime_ext[$ext])) {
+                return $mime_ext[$ext];
+            }
+        }
+    }
+
     /**
      * Get mimetype => file extension mapping
      *
diff --git a/program/steps/mail/get.inc b/program/steps/mail/get.inc
index 9327307f5..92745a37d 100644
--- a/program/steps/mail/get.inc
+++ b/program/steps/mail/get.inc
@@ -150,8 +150,8 @@ if (empty($_GET['_thumb']) && $attachment->is_valid()) {
                 $valid_extension = !$file_extension || empty($extensions) || in_array($file_extension, (array)$extensions);
             }
 
-            // fix mimetype for images wrongly declared as octet-stream
-            if ($mimetype == 'application/octet-stream' && strpos($real_mimetype, 'image/') === 0 && $valid_extension) {
+            // fix mimetype for files wrongly declared as octet-stream
+            if ($mimetype == 'application/octet-stream' && $valid_extension) {
                 $mimetype = $real_mimetype;
             }
             // fix mimetype for images with wrong mimetype
diff --git a/program/steps/mail/show.inc b/program/steps/mail/show.inc
index a36dce918..1c11583d7 100644
--- a/program/steps/mail/show.inc
+++ b/program/steps/mail/show.inc
@@ -194,10 +194,14 @@ function rcmail_message_attachments($attrib)
         foreach ($MESSAGE->attachments as $attach_prop) {
             $filename = rcmail_attachment_name($attach_prop, true);
             $filesize = $RCMAIL->message_part_size($attach_prop);
-            $mimetype = $attach_prop->mimetype;
+            $mimetype = rcube_mime::fix_mimetype($attach_prop->mimetype);
             $class    = rcube_utils::file2class($mimetype, $filename);
             $id       = 'attach' . $attach_prop->mime_id;
 
+            if ($mimetype == 'application/octet-stream' && ($type = rcube_mime::file_ext_type($filename))) {
+                $mimetype = $type;
+            }
+
             if ($attrib['maxlength'] && mb_strlen($filename) > $attrib['maxlength']) {
                 $title    = $filename;
                 $filename = abbreviate_string($filename, $attrib['maxlength']);