Only use libmagic for static resources if extension-based guessing fails.

matemat/webserver/httpd.py

@@ -4,6 +4,7 @@ from typing import Any, Callable, Dict, Tuple, Type, Union
 import logging
 import os
 import socket
+import mimetypes
 import magic
 from socketserver import TCPServer
 from http.server import HTTPServer, BaseHTTPRequestHandler
@@ -336,7 +337,11 @@ class HttpHandler(BaseHTTPRequestHandler):
                 except ValueError:
                     mimetype = 'application/octet-stream'
                     charset = 'binary'
-                headers['Content-Type'] = f'{mimetype}; charset={charset}'
+                # Only append the charset if it is not "binary"
+                if charset == 'binary':
+                    headers['Content-Type'] = mimetype
+                else:
+                    headers['Content-Type'] = f'{mimetype}; charset={charset}'
             # Send all headers set by the pagelet
             for name, value in headers.items():
                 self.send_header(name, value)
@@ -374,16 +379,21 @@ class HttpHandler(BaseHTTPRequestHandler):
                     data = f.read()
                 # File read successfully, send 'OK' header
                 self.send_response(200)
-                # Guess the MIME type and encoding using libmagic
+                # Guess the MIME type by file extension, or use libmagic as fallback
+                # Use libmagic to guess the charset
                 try:
+                    exttype: str = mimetypes.guess_type(filepath)[0]
                     filemagic: magic.FileMagic = magic.detect_from_filename(filepath)
-                    mimetype: str = filemagic.mime_type
+                    mimetype: str = exttype if exttype is not None else filemagic.mime_type
                     charset: str = filemagic.encoding
                 except ValueError:
                     mimetype = 'application/octet-stream'
                     charset = 'binary'
-                # Send content type and length header
+                # Send content type and length header.  Only set the charset if it's not "binary"
-                self.send_header('Content-Type', f'{mimetype}; charset={charset}')
+                if charset == 'binary':
+                    self.send_header('Content-Type', mimetype)
+                else:
+                    self.send_header('Content-Type', f'{mimetype}; charset={charset}')
                 self.send_header('Content-Length', str(len(data)))
                 self.send_header('Last-Modified', fileage.strftime('%a, %d %b %Y %H:%M:%S GMT'))
                 self.send_header('Cache-Control', 'max-age=1')

matemat/webserver/test/test_serve.py

@@ -78,6 +78,15 @@ class TestServe(AbstractHttpdTest):
         with open(forbidden, 'w') as f:
             f.write('This should not be readable')
         os.chmod(forbidden, 0)
+        # Create a CSS resource whose MIME type should be detected by file extension
+        with open(os.path.join(self.tempdir.name, 'teststyle.css'), 'w') as f:
+            f.write('.ninja { display: none; }\n')
+        # Create a file without extension (containing UTF-16 text with BOM); libmagic should take over
+        with open(os.path.join(self.tempdir.name, 'testdata'), 'wb') as f:
+            f.write(b'\xFE\xFFH\x00e\x00l\x00l\x00o\x00,\x00 \x00w\x00o\x00r\x00l\x00d\x00!\x00\n\x00')
+        # Create a file that will yield "text/plain; charset=binary"
+        with open(os.path.join(self.tempdir.name, 'testbin.txt'), 'wb') as f:
+            f.write(b'\x00\x00\x00\x00\x00\x00\x00\x00')
 
     def test_serve_pagelet_str(self):
         # Call the test pagelet that produces a 200 OK result
@@ -226,16 +235,40 @@ class TestServe(AbstractHttpdTest):
         # Make sure a 405 Method Not Allowed header is served
         self.assertEqual(405, packet.statuscode)
 
-    def test_serve_static_libmagic(self):
+    def test_serve_pagelet_libmagic(self):
         # The correct Content-Type header must be guessed, if a pagelet does not provide one
         self.client_sock.set_request(b'GET /just/testing/serve_pagelet_str HTTP/1.1\r\n\r\n')
         HttpHandler(self.client_sock, ('::1', 45678), self.server)
         packet = self.client_sock.get_response()
         self.assertEqual('text/plain; charset=us-ascii', packet.headers['Content-Type'])
 
-    def test_serve_static_libmagic_skipped(self):
+    def test_serve_pagelet_libmagic_skipped(self):
         # The Content-Type set by a pagelet should not be overwritten
         self.client_sock.set_request(b'GET /just/testing/serve_pagelet_bytes HTTP/1.1\r\n\r\n')
         HttpHandler(self.client_sock, ('::1', 45678), self.server)
         packet = self.client_sock.get_response()
         self.assertEqual('application/x-foo-bar', packet.headers['Content-Type'])
+
+    def test_serve_static_mime_extension(self):
+        # The correct Content-Type should be guessed by file extension primarily
+        self.client_sock.set_request(b'GET /teststyle.css HTTP/1.1\r\n\r\n')
+        HttpHandler(self.client_sock, ('::1', 45678), self.server)
+        packet = self.client_sock.get_response()
+        # libmagic would say text/plain instead
+        self.assertEqual('text/css; charset=us-ascii', packet.headers['Content-Type'])
+
+    def test_serve_static_mime_magic(self):
+        # The correct Content-Type should be guessed by file extension primarily
+        self.client_sock.set_request(b'GET /testdata HTTP/1.1\r\n\r\n')
+        HttpHandler(self.client_sock, ('::1', 45678), self.server)
+        packet = self.client_sock.get_response()
+        # Extension-based would fail, as there is no extension
+        self.assertEqual('text/plain; charset=utf-16be', packet.headers['Content-Type'])
+
+    def test_serve_static_mime_magic_binary(self):
+        # The correct Content-Type should be guessed by file extension primarily
+        self.client_sock.set_request(b'GET /testbin.txt HTTP/1.1\r\n\r\n')
+        HttpHandler(self.client_sock, ('::1', 45678), self.server)
+        packet = self.client_sock.get_response()
+        # No charset should be in the header.  Yes, this is a stupid example
+        self.assertEqual('text/plain', packet.headers['Content-Type'])