matrix: file extension is added even for non-image attachments

Author: selfhoster1312

bridge/matrix/matrix.go

@@ -787,26 +787,39 @@ func (b *Bmatrix) handleDownloadFile(rmsg *config.Message, content event.Content
 		return fmt.Errorf("mtype isn't a %T", mtype)
 	}
 
-	// check if we have an image uploaded without extension
-	if !strings.Contains(name, ".") {
-		if msgtype == "m.image" {
-			mext, _ := mime.ExtensionsByType(mtype)
-			if len(mext) > 0 {
-				name += mext[0]
-			}
-		} else {
-			// just a default .png extension if we don't have mime info
-			name += ".png"
+	b.Log.Debugf("Processing attachment %s with mimetype %s", name, mtype)
+
+	// If the mime library can't guess an appropriate extension for that
+	// content-type, we're not going to deal with that content because other
+	// bridges will have problems too.
+	mext, err := mime.ExtensionsByType(mtype)
+	if err != nil {
+		return err
+	}
+
+	// Make sure file has an extension matching the mimetype.
+	foundExt := false
+
+	for _, ext := range mext {
+		if strings.HasSuffix(name, ext) {
+			foundExt = true
+			break
 		}
 	}
 
+	if !foundExt {
+		// No extension was found, set the first matching extension
+		// according to the mime library.
+		name += mext[0]
+	}
+
 	// Now that we have performed sanity checks and edited the filename,
 	// remove the message "body" (which was parsed into the filename) so
 	// we don't have duplicates later on.
 	rmsg.Text = ""
 
 	// TODO: add attachment ID?
-	err := b.AddAttachmentFromProtectedURL(rmsg, name, "", caption, url)
+	err = b.AddAttachmentFromProtectedURL(rmsg, name, "", caption, url)
 	if err != nil {
 		return err
 	}

changelog.md

@@ -52,7 +52,10 @@
     the return code is not 200 to avoid saving trash data ([#20](https://github.com/matterbridge-org/matterbridge/pull/20))
 - matrix
   - attachments received from matrix are working again, with authenticated media (MSC3916) implemented ([#61](https://github.com/matterbridge-org/matterbridge/pull/61))
-  - attachment body is treated as attachment caption and will no longer produce bogus text messages on other bridges
+  - attachment body is treated as attachment caption and will no longer produce bogus text messages on other bridges ([#169](https://github.com/matterbridge-org/matterbridge/pull/169/))
+  - attachment filenames without extension how have an extension added according to mimetype, even when they're not images ;
+    when they are images, it's no longer assumed that they are PNG ([#169](https://github.com/matterbridge-org/matterbridge/pull/169/))
+  - attachments with an unknown mimetype are discarded to avoid producing more errors further down ([#169](https://github.com/matterbridge-org/matterbridge/pull/169/))
   - image attachments are now sent as images with more metadata ([#61](https://github.com/matterbridge-org/matterbridge/pull/61))
 - xmpp
   - various upstream go-xmpp changes fix connection on SASL2 with PLAIN auth