fix #553

2 files changed, 33 insertions, 2 deletions

diff --git a/libmproxy/protocol/http.py b/libmproxy/protocol/http.py
index c763db4c..05657ea6 100644
--- a/libmproxy/protocol/http.py
+++ b/libmproxy/protocol/http.py
@@ -328,9 +328,22 @@ class HTTPRequest(HTTPMessage):
         )
 
     @classmethod
-    def from_stream(cls, rfile, include_body=True, body_size_limit=None):
+    def from_stream(cls, rfile, include_body=True, body_size_limit=None, wfile=None):
         """
         Parse an HTTP request from a file stream
+
+        Args:
+            rfile (file): Input file to read from
+            include_body (bool): Read response body as well
+            body_size_limit (bool): Maximum body size
+            wfile (file): If specified, HTTP Expect headers are handled automatically.
+                          by writing a HTTP 100 CONTINUE response to the stream.
+
+        Returns:
+            HTTPRequest: The HTTP request
+
+        Raises:
+            HttpError: If the input is invalid.
         """
         httpversion, host, port, scheme, method, path, headers, content, timestamp_start, timestamp_end = (
             None, None, None, None, None, None, None, None, None, None)
@@ -385,6 +398,15 @@ class HTTPRequest(HTTPMessage):
         if headers is None:
             raise http.HttpError(400, "Invalid headers")
 
+        expect_header = headers.get_first("expect")
+        if expect_header and expect_header.lower() == "100-continue" and httpversion >= (1, 1):
+            wfile.write(
+                'HTTP/1.1 100 Continue\r\n'
+                '\r\n'
+            )
+            wfile.flush()
+            del headers['expect']
+
         if include_body:
             content = http.read_http_body(rfile, headers, body_size_limit,
                                           method, None, True)
@@ -1062,7 +1084,8 @@ class HTTPHandler(ProtocolHandler):
             try:
                 req = HTTPRequest.from_stream(
                     self.c.client_conn.rfile,
-                    body_size_limit=self.c.config.body_size_limit
+                    body_size_limit=self.c.config.body_size_limit,
+                    wfile=self.c.client_conn.wfile
                 )
             except tcp.NetLibError:
                 # don't throw an error for disconnects that happen
diff --git a/test/test_protocol_http.py b/test/test_protocol_http.py
index 23c3f469..c6fad508 100644
--- a/test/test_protocol_http.py
+++ b/test/test_protocol_http.py
@@ -55,6 +55,14 @@ class TestHTTPRequest:
         r.update_host_header()
         assert "Host" in r.headers
 
+    def test_expect_header(self):
+        s = StringIO("GET / HTTP/1.1\r\nContent-Length: 3\r\nExpect: 100-continue\r\n\r\nfoobar")
+        w = StringIO()
+        r = HTTPRequest.from_stream(s, wfile=w)
+        assert w.getvalue() == "HTTP/1.1 100 Continue\r\n\r\n"
+        assert r.content == "foo"
+        assert s.read(3) == "bar"
+
     def test_authority_form_in(self):
         s = StringIO("CONNECT oops-no-port.com HTTP/1.1")
         tutils.raises("Bad HTTP request line", HTTPRequest.from_stream, s)