1 files changed, 179 insertions, 0 deletions
diff --git a/libmproxy/protocol/base.py b/libmproxy/protocol/base.py
new file mode 100644
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+++ b/libmproxy/protocol/base.py
@@ -0,0 +1,179 @@
+"""
+mitmproxy protocol architecture
+
+In mitmproxy, protocols are implemented as a set of layers, which are composed on top each other.
+For example, the following scenarios depict possible settings (lowest layer first):
+
+Transparent HTTP proxy, no SSL:
+    TransparentProxy
+    Http1Layer
+    HttpLayer
+
+Regular proxy, CONNECT request with WebSockets over SSL:
+    HttpProxy
+    Http1Layer
+    HttpLayer
+    SslLayer
+    WebsocketLayer (or TcpLayer)
+
+Automated protocol detection by peeking into the buffer:
+    TransparentProxy
+    TLSLayer
+    Http2Layer
+    HttpLayer
+
+Communication between layers is done as follows:
+    - lower layers provide context information to higher layers
+    - higher layers can call functions provided by lower layers,
+      which are propagated until they reach a suitable layer.
+
+Further goals:
+  - Connections should always be peekable to make automatic protocol detection work.
+  - Upstream connections should be established as late as possible;
+    inline scripts shall have a chance to handle everything locally.
+"""
+from __future__ import (absolute_import, print_function, division)
+from netlib import tcp
+from ..models import ServerConnection
+from ..exceptions import ProtocolException
+
+
+class _LayerCodeCompletion(object):
+    """
+    Dummy class that provides type hinting in PyCharm, which simplifies development a lot.
+    """
+
+    def __init__(self, *args, **kwargs):  # pragma: nocover
+        super(_LayerCodeCompletion, self).__init__(*args, **kwargs)
+        if True:
+            return
+        self.config = None
+        """@type: libmproxy.proxy.ProxyConfig"""
+        self.client_conn = None
+        """@type: libmproxy.models.ClientConnection"""
+        self.server_conn = None
+        """@type: libmproxy.models.ServerConnection"""
+        self.channel = None
+        """@type: libmproxy.controller.Channel"""
+
+
+class Layer(_LayerCodeCompletion):
+    def __init__(self, ctx, *args, **kwargs):
+        """
+        Args:
+            ctx: The (read-only) higher layer.
+        """
+        self.ctx = ctx
+        """@type: libmproxy.protocol.Layer"""
+        super(Layer, self).__init__(*args, **kwargs)
+
+    def __call__(self):
+        """
+        Logic of the layer.
+        Raises:
+            ProtocolException in case of protocol exceptions.
+        """
+        raise NotImplementedError()
+
+    def __getattr__(self, name):
+        """
+        Attributes not present on the current layer may exist on a higher layer.
+        """
+        return getattr(self.ctx, name)
+
+    def log(self, msg, level, subs=()):
+        full_msg = [
+            "{}: {}".format(repr(self.client_conn.address), msg)
+        ]
+        for i in subs:
+            full_msg.append("  -> " + i)
+        full_msg = "\n".join(full_msg)
+        self.channel.tell("log", Log(full_msg, level))
+
+    @property
+    def layers(self):
+        return [self] + self.ctx.layers
+
+    def __repr__(self):
+        return type(self).__name__
+
+
+class ServerConnectionMixin(object):
+    """
+    Mixin that provides a layer with the capabilities to manage a server connection.
+    """
+
+    def __init__(self, server_address=None):
+        super(ServerConnectionMixin, self).__init__()
+        self.server_conn = ServerConnection(server_address)
+        self._check_self_connect()
+
+    def reconnect(self):
+        address = self.server_conn.address
+        self._disconnect()
+        self.server_conn.address = address
+        self.connect()
+
+    def _check_self_connect(self):
+        """
+        We try to protect the proxy from _accidentally_ connecting to itself,
+        e.g. because of a failed transparent lookup or an invalid configuration.
+        """
+        address = self.server_conn.address
+        if address:
+            self_connect = (
+                address.port == self.config.port and
+                address.host in ("localhost", "127.0.0.1", "::1")
+            )
+            if self_connect:
+                raise ProtocolException(
+                    "Invalid server address: {}\r\n"
+                    "The proxy shall not connect to itself.".format(repr(address))
+                )
+
+    def set_server(self, address, server_tls=None, sni=None, depth=1):
+        if depth == 1:
+            if self.server_conn:
+                self._disconnect()
+            self.log("Set new server address: " + repr(address), "debug")
+            self.server_conn.address = address
+            self._check_self_connect()
+            if server_tls:
+                raise ProtocolException(
+                    "Cannot upgrade to TLS, no TLS layer on the protocol stack."
+                )
+        else:
+            self.ctx.set_server(address, server_tls, sni, depth - 1)
+
+    def _disconnect(self):
+        """
+        Deletes (and closes) an existing server connection.
+        """
+        self.log("serverdisconnect", "debug", [repr(self.server_conn.address)])
+        self.server_conn.finish()
+        self.server_conn.close()
+        self.channel.tell("serverdisconnect", self.server_conn)
+        self.server_conn = ServerConnection(None)
+
+    def connect(self):
+        if not self.server_conn.address:
+            raise ProtocolException("Cannot connect to server, no server address given.")
+        self.log("serverconnect", "debug", [repr(self.server_conn.address)])
+        self.channel.ask("serverconnect", self.server_conn)
+        try:
+            self.server_conn.connect()
+        except tcp.NetLibError as e:
+            raise ProtocolException(
+                "Server connection to %s failed: %s" % (repr(self.server_conn.address), e), e)
+
+
+class Log(object):
+    def __init__(self, msg, level="info"):
+        self.msg = msg
+        self.level = level
+
+
+class Kill(Exception):
+    """
+    Kill a connection.
+    """