Issue #25738: Don’t send message body for 205 Reset Content

Patch by Susumu Koshiba.

2 files changed, 64 insertions, 10 deletions

diff --git a/Lib/http/server.py b/Lib/http/server.py
index 3bd1f7a..00620d1 100644
--- a/Lib/http/server.py
+++ b/Lib/http/server.py
@@ -450,20 +450,30 @@ class BaseHTTPRequestHandler(socketserver.StreamRequestHandler):
         if explain is None:
             explain = longmsg
         self.log_error("code %d, message %s", code, message)
-        # using _quote_html to prevent Cross Site Scripting attacks (see bug #1100201)
-        content = (self.error_message_format %
-                   {'code': code, 'message': _quote_html(message), 'explain': _quote_html(explain)})
-        body = content.encode('UTF-8', 'replace')
         self.send_response(code, message)
-        self.send_header("Content-Type", self.error_content_type)
         self.send_header('Connection', 'close')
-        self.send_header('Content-Length', int(len(body)))
+
+        # Message body is omitted for cases described in:
+        #  - RFC7230: 3.3. 1xx, 204(No Content), 304(Not Modified)
+        #  - RFC7231: 6.3.6. 205(Reset Content)
+        body = None
+        if (code >= 200 and
+            code not in (HTTPStatus.NO_CONTENT,
+                         HTTPStatus.RESET_CONTENT,
+                         HTTPStatus.NOT_MODIFIED)):
+            # HTML encode to prevent Cross Site Scripting attacks
+            # (see bug #1100201)
+            content = (self.error_message_format % {
+                'code': code,
+                'message': _quote_html(message),
+                'explain': _quote_html(explain)
+            })
+            body = content.encode('UTF-8', 'replace')
+            self.send_header("Content-Type", self.error_content_type)
+            self.send_header('Content-Length', int(len(body)))
         self.end_headers()
 
-        if (self.command != 'HEAD' and
-                code >= 200 and
-                code not in (
-                    HTTPStatus.NO_CONTENT, HTTPStatus.NOT_MODIFIED)):
+        if self.command != 'HEAD' and body:
             self.wfile.write(body)
 
     def send_response(self, code, message=None):
diff --git a/Lib/test/test_httpservers.py b/Lib/test/test_httpservers.py
index 1fffdb1..72e6e08 100644
--- a/Lib/test/test_httpservers.py
+++ b/Lib/test/test_httpservers.py
@@ -115,6 +115,12 @@ class BaseHTTPServerTestCase(BaseTestCase):
             body = self.headers['x-special-incoming'].encode('utf-8')
             self.wfile.write(body)
 
+        def do_SEND_ERROR(self):
+            self.send_error(int(self.path[1:]))
+
+        def do_HEAD(self):
+            self.send_error(int(self.path[1:]))
+
     def setUp(self):
         BaseTestCase.setUp(self)
         self.con = http.client.HTTPConnection(self.HOST, self.PORT)
@@ -236,6 +242,44 @@ class BaseHTTPServerTestCase(BaseTestCase):
         data = res.read()
         self.assertEqual(int(res.getheader('Content-Length')), len(data))
 
+    def test_send_error(self):
+        allow_transfer_encoding_codes = (HTTPStatus.NOT_MODIFIED,
+                                         HTTPStatus.RESET_CONTENT)
+        for code in (HTTPStatus.NO_CONTENT, HTTPStatus.NOT_MODIFIED,
+                     HTTPStatus.PROCESSING, HTTPStatus.RESET_CONTENT,
+                     HTTPStatus.SWITCHING_PROTOCOLS):
+            self.con.request('SEND_ERROR', '/{}'.format(code))
+            res = self.con.getresponse()
+            self.assertEqual(code, res.status)
+            self.assertEqual(None, res.getheader('Content-Length'))
+            self.assertEqual(None, res.getheader('Content-Type'))
+            if code not in allow_transfer_encoding_codes:
+                self.assertEqual(None, res.getheader('Transfer-Encoding'))
+
+            data = res.read()
+            self.assertEqual(b'', data)
+
+    def test_head_via_send_error(self):
+        allow_transfer_encoding_codes = (HTTPStatus.NOT_MODIFIED,
+                                         HTTPStatus.RESET_CONTENT)
+        for code in (HTTPStatus.OK, HTTPStatus.NO_CONTENT,
+                     HTTPStatus.NOT_MODIFIED, HTTPStatus.RESET_CONTENT,
+                     HTTPStatus.SWITCHING_PROTOCOLS):
+            self.con.request('HEAD', '/{}'.format(code))
+            res = self.con.getresponse()
+            self.assertEqual(code, res.status)
+            if code == HTTPStatus.OK:
+                self.assertTrue(int(res.getheader('Content-Length')) > 0)
+                self.assertIn('text/html', res.getheader('Content-Type'))
+            else:
+                self.assertEqual(None, res.getheader('Content-Length'))
+                self.assertEqual(None, res.getheader('Content-Type'))
+            if code not in allow_transfer_encoding_codes:
+                self.assertEqual(None, res.getheader('Transfer-Encoding'))
+
+            data = res.read()
+            self.assertEqual(b'', data)
+
 
 class RequestHandlerLoggingTestCase(BaseTestCase):
     class request_handler(BaseHTTPRequestHandler):