Handle duplicate content-length

gunicorn/http/message.py

@@ -131,6 +131,8 @@ class Message(object):
         content_length = None
         for (name, value) in self.headers:
             if name == "CONTENT-LENGTH":
+                if content_length is not None:
+                    raise InvalidHeader("CONTENT-LENGTH", req=self)
                 content_length = value
             elif name == "TRANSFER-ENCODING":
                 chunked = value.lower() == "chunked"

tests/requests/invalid/021.http

@@ -0,0 +1,5 @@
+GET /stuff/here?foo=bar HTTP/1.1\r\n
+Content-Length: 3\r\n
+Content-Length: 2\r\n
+\r\n
+xyz

tests/requests/invalid/021.py

@@ -0,0 +1,5 @@
+from gunicorn.config import Config
+from gunicorn.http.errors import InvalidHeader
+
+cfg = Config()
+request = InvalidHeader