Add custom mime type mapping for downloadable files

Author: szatyinadam

custom/conf/app.example.ini

@@ -2037,3 +2037,8 @@ PATH =
 ;;
 ;; Minio enabled ssl only available when STORAGE_TYPE is `minio`
 ;MINIO_USE_SSL = false
+
+; Custom mime type mapping for downloadable files
+;[download.mimetype.mapping]
+;.apk=application/vnd.android.package-archive
+;.js=application/javascript

modules/setting/mime_type_map.go

@@ -0,0 +1,29 @@
+// Copyright 2021 The Gitea Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package setting
+
+var (
+	// MimeTypeMap defines custom mime type mapping settings
+	MimeTypeMap = struct {
+		Enabled bool
+		Map     map[string]string
+	}{
+		Enabled: false,
+		Map:     map[string]string{},
+	}
+)
+
+func newMimeTypeMap() {
+	sec := Cfg.Section("download.mimetype.mapping")
+	keys := sec.Keys()
+	m := make(map[string]string, len(keys))
+	for _, key := range keys {
+		m[key.Name()] = key.Value()
+	}
+	MimeTypeMap.Map = m
+	if len(keys) > 0 {
+		MimeTypeMap.Enabled = true
+	}
+}

modules/setting/setting.go

@@ -1177,4 +1177,5 @@ func NewServices() {
 	newTaskService()
 	NewQueueService()
 	newProject()
+	newMimeTypeMap()
 }

routers/repo/download.go

@@ -19,6 +19,7 @@ import (
 	"code.gitea.io/gitea/modules/httpcache"
 	"code.gitea.io/gitea/modules/lfs"
 	"code.gitea.io/gitea/modules/log"
+	"code.gitea.io/gitea/modules/setting"
 )
 
 // ServeData download file from io.Reader
@@ -62,8 +63,10 @@ func ServeData(ctx *context.Context, name string, size int64, reader io.Reader)
 	} else {
 		ctx.Resp.Header().Set("Content-Disposition", fmt.Sprintf(`attachment; filename="%s"`, name))
 		ctx.Resp.Header().Set("Access-Control-Expose-Headers", "Content-Disposition")
-		if strings.EqualFold(".apk", filepath.Ext(name)) && base.IsZipFile(buf) {
-			ctx.Resp.Header().Set("Content-Type", "application/vnd.android.package-archive")
+		if setting.MimeTypeMap.Enabled {
+			if mimetype, ok := setting.MimeTypeMap.Map[filepath.Ext(name)]; ok {
+				ctx.Resp.Header().Set("Content-Type", mimetype)
+			}
 		}
 	}