1 files changed, 93 insertions, 0 deletions
diff --git a/libmproxy/proxy/root_context.py b/libmproxy/proxy/root_context.py
new file mode 100644
index 00000000..35909612
--- /dev/null
+++ b/libmproxy/proxy/root_context.py
@@ -0,0 +1,93 @@
+from __future__ import (absolute_import, print_function, division)
+
+from netlib.http.http1 import HTTP1Protocol
+from netlib.http.http2 import HTTP2Protocol
+
+from ..protocol import (
+    RawTCPLayer, TlsLayer, Http1Layer, Http2Layer, is_tls_record_magic, ServerConnectionMixin
+)
+from .modes import HttpProxy, HttpUpstreamProxy, ReverseProxy
+
+
+class RootContext(object):
+    """
+    The outmost context provided to the root layer.
+    As a consequence, every layer has .client_conn, .channel, .next_layer() and .config.
+    """
+
+    def __init__(self, client_conn, config, channel):
+        self.client_conn = client_conn  # Client Connection
+        self.channel = channel  # provides .ask() method to communicate with FlowMaster
+        self.config = config  # Proxy Configuration
+
+    def next_layer(self, top_layer):
+        """
+        This function determines the next layer in the protocol stack.
+
+        Arguments:
+            top_layer: the current top layer.
+
+        Returns:
+            The next layer
+        """
+
+        # 1. Check for --ignore.
+        if self.config.check_ignore(top_layer.server_conn.address):
+            return RawTCPLayer(top_layer, logging=False)
+
+        d = top_layer.client_conn.rfile.peek(3)
+        client_tls = is_tls_record_magic(d)
+
+        # 2. Always insert a TLS layer, even if there's neither client nor server tls.
+        # An inline script may upgrade from http to https,
+        # in which case we need some form of TLS layer.
+        if isinstance(top_layer, ReverseProxy):
+            return TlsLayer(top_layer, client_tls, top_layer.server_tls)
+        if isinstance(top_layer, ServerConnectionMixin):
+            return TlsLayer(top_layer, client_tls, client_tls)
+
+        # 3. In Http Proxy mode and Upstream Proxy mode, the next layer is fixed.
+        if isinstance(top_layer, TlsLayer):
+            if isinstance(top_layer.ctx, HttpProxy):
+                return Http1Layer(top_layer, "regular")
+            if isinstance(top_layer.ctx, HttpUpstreamProxy):
+                return Http1Layer(top_layer, "upstream")
+
+        # 4. Check for other TLS cases (e.g. after CONNECT).
+        if client_tls:
+            return TlsLayer(top_layer, True, True)
+
+        # 4. Check for --tcp
+        if self.config.check_tcp(top_layer.server_conn.address):
+            return RawTCPLayer(top_layer)
+
+        # 5. Check for TLS ALPN (HTTP1/HTTP2)
+        if isinstance(top_layer, TlsLayer):
+            alpn = top_layer.client_conn.get_alpn_proto_negotiated()
+            if alpn == HTTP2Protocol.ALPN_PROTO_H2:
+                return Http2Layer(top_layer, 'transparent')
+            if alpn == HTTP1Protocol.ALPN_PROTO_HTTP1:
+                return Http1Layer(top_layer, 'transparent')
+
+        # 6. Assume HTTP1 by default
+        return Http1Layer(top_layer, 'transparent')
+
+        # In a future version, we want to implement TCP passthrough as the last fallback,
+        # but we don't have the UI part ready for that.
+        #
+        # d = top_layer.client_conn.rfile.peek(3)
+        # is_ascii = (
+        #     len(d) == 3 and
+        #     # better be safe here and don't expect uppercase...
+        #     all(x in string.ascii_letters for x in d)
+        # )
+        # # TODO: This could block if there are not enough bytes available?
+        # d = top_layer.client_conn.rfile.peek(len(HTTP2Protocol.CLIENT_CONNECTION_PREFACE))
+        # is_http2_magic = (d == HTTP2Protocol.CLIENT_CONNECTION_PREFACE)
+
+    @property
+    def layers(self):
+        return []
+
+    def __repr__(self):
+        return "RootContext"