Add mimetype mapping settings (go-gitea#15133)

* Fix APK's Content-Type header

* Fix case sensitive comparison

* Add custom mime type mapping for downloadable files

* Add documentation for MIME type mapping

* Rename download.mimetype.mapping configuration to repository.mimetype_mapping

Co-authored-by: zeripath <art27@cantab.net>

custom/conf/app.example.ini

@@ -903,6 +903,15 @@ PATH =
 ;; - approved: only sign when merging an approved pr to a protected branch
 ;MERGES = pubkey, twofa, basesigned, commitssigned
 
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;[repository.mimetype_mapping]
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;;
+;; Custom MIME type mapping for downloadable files
+;.apk=application/vnd.android.package-archive
+
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 ;[project]
@@ -912,7 +921,6 @@ PATH =
 ;PROJECT_BOARD_BASIC_KANBAN_TYPE = To Do, In Progress, Done
 ;PROJECT_BOARD_BUG_TRIAGE_TYPE = Needs Triage, High Priority, Low Priority, Closed
 
-
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 ;[cors]

docs/content/doc/advanced/config-cheat-sheet.en-us.md

@@ -143,6 +143,15 @@ Values containing `#` or `;` must be quoted using `` ` `` or `"""`.
 
 - `LOCAL_COPY_PATH`: **tmp/local-repo**: Path for temporary local repository copies. Defaults to `tmp/local-repo`
 
+## Repository -  MIME type mapping (`repository.mimetype_mapping`)
+
+Configuration for set the expected MIME type based on file extensions of downloadable files. Configuration presents in key-value pairs and file extensions starts with leading `.`.
+
+The following configuration set `Content-Type: application/vnd.android.package-archive` header when downloading files with `.apk` file extension.
+```ini
+.apk=application/vnd.android.package-archive
+```
+
 ## CORS (`cors`)
 
 - `ENABLED`: **false**: enable cors headers (disabled by default)

modules/setting/mime_type_map.go

@@ -0,0 +1,31 @@
+// 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
+
+import "strings"
+
+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("repository.mimetype_mapping")
+	keys := sec.Keys()
+	m := make(map[string]string, len(keys))
+	for _, key := range keys {
+		m[strings.ToLower(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

@@ -9,6 +9,7 @@ import (
 	"fmt"
 	"io"
 	"path"
+	"path/filepath"
 	"strings"
 
 	"code.gitea.io/gitea/modules/base"
@@ -18,6 +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
@@ -61,6 +63,12 @@ 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 setting.MimeTypeMap.Enabled {
+			fileExtension := strings.ToLower(filepath.Ext(name))
+			if mimetype, ok := setting.MimeTypeMap.Map[fileExtension]; ok {
+				ctx.Resp.Header().Set("Content-Type", mimetype)
+			}
+		}
 	}
 
 	_, err = ctx.Resp.Write(buf)