1 files changed, 40 insertions, 0 deletions
diff --git a/modules/public/mime_types.go b/modules/public/mime_types.go
new file mode 100644
index 0000000..32bdf3b
--- /dev/null
+++ b/modules/public/mime_types.go
@@ -0,0 +1,40 @@
+// Copyright 2022 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package public
+
+import "strings"
+
+// wellKnownMimeTypesLower comes from Golang's builtin mime package: `builtinTypesLower`, see the comment of detectWellKnownMimeType
+var wellKnownMimeTypesLower = map[string]string{
+	".avif": "image/avif",
+	".css":  "text/css; charset=utf-8",
+	".gif":  "image/gif",
+	".htm":  "text/html; charset=utf-8",
+	".html": "text/html; charset=utf-8",
+	".jpeg": "image/jpeg",
+	".jpg":  "image/jpeg",
+	".js":   "text/javascript; charset=utf-8",
+	".json": "application/json",
+	".mjs":  "text/javascript; charset=utf-8",
+	".pdf":  "application/pdf",
+	".png":  "image/png",
+	".svg":  "image/svg+xml",
+	".wasm": "application/wasm",
+	".webp": "image/webp",
+	".xml":  "text/xml; charset=utf-8",
+
+	// well, there are some types missing from the builtin list
+	".txt": "text/plain; charset=utf-8",
+}
+
+// detectWellKnownMimeType will return the mime-type for a well-known file ext name
+// The purpose of this function is to bypass the unstable behavior of Golang's mime.TypeByExtension
+// mime.TypeByExtension would use OS's mime-type config to overwrite the well-known types (see its document).
+// If the user's OS has incorrect mime-type config, it would make Gitea can not respond a correct Content-Type to browsers.
+// For example, if Gitea returns `text/plain` for a `.js` file, the browser couldn't run the JS due to security reasons.
+// detectWellKnownMimeType makes the Content-Type for well-known files stable.
+func detectWellKnownMimeType(ext string) string {
+	ext = strings.ToLower(ext)
+	return wellKnownMimeTypesLower[ext]
+}