fix #2329

mitmproxy/proxy/root_context.py

@@ -70,8 +70,16 @@ class RootContext:
                 top_layer.server_tls,
                 top_layer.server_conn.address[0]
             )
-        if isinstance(top_layer, protocol.ServerConnectionMixin) or isinstance(top_layer, protocol.UpstreamConnectLayer):
+        if isinstance(top_layer, protocol.ServerConnectionMixin):
             return protocol.TlsLayer(top_layer, client_tls, client_tls)
+        if isinstance(top_layer, protocol.UpstreamConnectLayer):
+            # if the user manually sets a scheme for connect requests, we use this to decide if we
+            # want TLS or not.
+            if top_layer.connect_request.scheme:
+                tls = top_layer.connect_request.scheme == "https"
+            else:
+                tls = client_tls
+            return protocol.TlsLayer(top_layer, client_tls, tls)
 
         # 3. In Http Proxy mode and Upstream Proxy mode, the next layer is fixed.
         if isinstance(top_layer, protocol.TlsLayer):

test/mitmproxy/proxy/test_server.py

@@ -1009,6 +1009,40 @@ class TestUpstreamProxySSL(
         assert len(self.chain[0].tmaster.state.flows) == 0
         assert len(self.chain[1].tmaster.state.flows) == 1
 
+    def test_connect_https_to_http(self):
+        """
+        https://github.com/mitmproxy/mitmproxy/issues/2329
+
+        Client <- HTTPS -> Proxy <- HTTP -> Proxy <- HTTPS -> Server
+        """
+        self.proxy.tmaster.addons.add(RewriteToHttp())
+        self.chain[1].tmaster.addons.add(RewriteToHttps())
+        p = self.pathoc()
+        with p.connect():
+            resp = p.request("get:'/p/418'")
+
+        assert self.proxy.tmaster.state.flows[0].client_conn.tls_established
+        assert not self.proxy.tmaster.state.flows[0].server_conn.tls_established
+        assert not self.chain[1].tmaster.state.flows[0].client_conn.tls_established
+        assert self.chain[1].tmaster.state.flows[0].server_conn.tls_established
+        assert resp.status_code == 418
+
+
+class RewriteToHttp:
+    def http_connect(self, f):
+        f.request.scheme = "http"
+
+    def request(self, f):
+        f.request.scheme = "http"
+
+
+class RewriteToHttps:
+    def http_connect(self, f):
+        f.request.scheme = "https"
+
+    def request(self, f):
+        f.request.scheme = "https"
+
 
 class UpstreamProxyChanger:
     def __init__(self, addr):