Merge pull request #88 from michalpokusa/https-implementation

HTTPS implementation

Author: dhalbert

README.rst

@@ -32,6 +32,7 @@ HTTP Server for CircuitPython.
 - Supports URL parameters and wildcard URLs.
 - Supports HTTP Basic and Bearer Authentication on both server and route per level.
 - Supports Websockets and Server-Sent Events.
+- Limited support for HTTPS (only on selected microcontrollers with enough memory e.g. ESP32-S3).
 
 
 Dependencies

adafruit_httpserver/server.py

@@ -12,6 +12,7 @@
 except ImportError:
     pass
 
+from ssl import SSLContext, create_default_context
 from errno import EAGAIN, ECONNRESET, ETIMEDOUT
 from sys import implementation
 from time import monotonic, sleep
@@ -33,12 +34,18 @@
 from .route import Route
 from .status import BAD_REQUEST_400, UNAUTHORIZED_401, FORBIDDEN_403, NOT_FOUND_404
 
+if implementation.name != "circuitpython":
+    from ssl import Purpose, CERT_NONE, SSLError  # pylint: disable=ungrouped-imports
+
 
 NO_REQUEST = "no_request"
 CONNECTION_TIMED_OUT = "connection_timed_out"
 REQUEST_HANDLED_NO_RESPONSE = "request_handled_no_response"
 REQUEST_HANDLED_RESPONSE_SENT = "request_handled_response_sent"
 
+# CircuitPython does not have these error codes
+MBEDTLS_ERR_SSL_FATAL_ALERT_MESSAGE = -30592
+
 
 class Server:  # pylint: disable=too-many-instance-attributes
     """A basic socket-based HTTP server."""
@@ -52,25 +59,81 @@ class Server:  # pylint: disable=too-many-instance-attributes
     root_path: str
     """Root directory to serve files from. ``None`` if serving files is disabled."""
 
+    @staticmethod
+    def _validate_https_cert_provided(
+        certfile: Union[str, None], keyfile: Union[str, None]
+    ) -> None:
+        if certfile is None or keyfile is None:
+            raise ValueError("Both certfile and keyfile must be specified for HTTPS")
+
+    @staticmethod
+    def _create_circuitpython_ssl_context(certfile: str, keyfile: str) -> SSLContext:
+        ssl_context = create_default_context()
+
+        ssl_context.load_verify_locations(cadata="")
+        ssl_context.load_cert_chain(certfile, keyfile)
+
+        return ssl_context
+
+    @staticmethod
+    def _create_cpython_ssl_context(certfile: str, keyfile: str) -> SSLContext:
+        ssl_context = create_default_context(purpose=Purpose.CLIENT_AUTH)
+
+        ssl_context.load_cert_chain(certfile, keyfile)
+
+        ssl_context.verify_mode = CERT_NONE
+        ssl_context.check_hostname = False
+
+        return ssl_context
+
+    @classmethod
+    def _create_ssl_context(cls, certfile: str, keyfile: str) -> SSLContext:
+        return (
+            cls._create_circuitpython_ssl_context(certfile, keyfile)
+            if implementation.name == "circuitpython"
+            else cls._create_cpython_ssl_context(certfile, keyfile)
+        )
+
     def __init__(
-        self, socket_source: _ISocketPool, root_path: str = None, *, debug: bool = False
+        self,
+        socket_source: _ISocketPool,
+        root_path: str = None,
+        *,
+        https: bool = False,
+        certfile: str = None,
+        keyfile: str = None,
+        debug: bool = False,
     ) -> None:
         """Create a server, and get it ready to run.
 
         :param socket: An object that is a source of sockets. This could be a `socketpool`
           in CircuitPython or the `socket` module in CPython.
         :param str root_path: Root directory to serve files from
         :param bool debug: Enables debug messages useful during development
+        :param bool https: If True, the server will use HTTPS
+        :param str certfile: Path to the certificate file, required if ``https`` is True
+        :param str keyfile: Path to the private key file, required if ``https`` is True
         """
-        self._auths = []
         self._buffer = bytearray(1024)
         self._timeout = 1
+
+        self._auths = []
         self._routes: "List[Route]" = []
+        self.headers = Headers()
+
         self._socket_source = socket_source
         self._sock = None
-        self.headers = Headers()
+
         self.host, self.port = None, None
         self.root_path = root_path
+        self.https = https
+
+        if https:
+            self._validate_https_cert_provided(certfile, keyfile)
+            self._ssl_context = self._create_ssl_context(certfile, keyfile)
+        else:
+            self._ssl_context = None
+
         if root_path in ["", "/"] and debug:
             _debug_warning_exposed_files(root_path)
         self.stopped = True
@@ -197,6 +260,7 @@ def serve_forever(
     @staticmethod
     def _create_server_socket(
         socket_source: _ISocketPool,
+        ssl_context: "SSLContext | None",
         host: str,
         port: int,
     ) -> _ISocket:
@@ -206,6 +270,9 @@ def _create_server_socket(
         if implementation.version >= (9,) or implementation.name != "circuitpython":
             sock.setsockopt(socket_source.SOL_SOCKET, socket_source.SO_REUSEADDR, 1)
 
+        if ssl_context is not None:
+            sock = ssl_context.wrap_socket(sock, server_side=True)
+
         sock.bind((host, port))
         sock.listen(10)
         sock.setblocking(False)  # Non-blocking socket
@@ -225,7 +292,9 @@ def start(self, host: str = "0.0.0.0", port: int = 5000) -> None:
         self.host, self.port = host, port
 
         self.stopped = False
-        self._sock = self._create_server_socket(self._socket_source, host, port)
+        self._sock = self._create_server_socket(
+            self._socket_source, self._ssl_context, host, port
+        )
 
         if self.debug:
             _debug_started_server(self)
@@ -386,7 +455,9 @@ def _set_default_server_headers(self, response: Response) -> None:
                 name, value
             )
 
-    def poll(self) -> str:
+    def poll(  # pylint: disable=too-many-branches,too-many-return-statements
+        self,
+    ) -> str:
         """
         Call this method inside your main loop to get the server to check for new incoming client
         requests. When a request comes in, it will be handled by the handler function.
@@ -399,11 +470,12 @@ def poll(self) -> str:
 
         conn = None
         try:
+            if self.debug:
+                _debug_start_time = monotonic()
+
             conn, client_address = self._sock.accept()
             conn.settimeout(self._timeout)
 
-            _debug_start_time = monotonic()
-
             # Receive the whole request
             if (request := self._receive_request(conn, client_address)) is None:
                 conn.close()
@@ -424,9 +496,8 @@ def poll(self) -> str:
             # Send the response
             response._send()  # pylint: disable=protected-access
 
-            _debug_end_time = monotonic()
-
             if self.debug:
+                _debug_end_time = monotonic()
                 _debug_response_sent(response, _debug_end_time - _debug_start_time)
 
             return REQUEST_HANDLED_RESPONSE_SENT
@@ -439,6 +510,15 @@ def poll(self) -> str:
                 # Connection reset by peer, try again later.
                 if error.errno == ECONNRESET:
                     return NO_REQUEST
+                # Handshake failed, try again later.
+                if error.errno == MBEDTLS_ERR_SSL_FATAL_ALERT_MESSAGE:
+                    return NO_REQUEST
+
+            # CPython specific SSL related errors
+            if implementation.name != "circuitpython" and isinstance(error, SSLError):
+                # Ignore unknown SSL certificate errors
+                if getattr(error, "reason", None) == "SSLV3_ALERT_CERTIFICATE_UNKNOWN":
+                    return NO_REQUEST
 
             if self.debug:
                 _debug_exception_in_handler(error)
@@ -547,9 +627,10 @@ def _debug_warning_exposed_files(root_path: str):
 
 def _debug_started_server(server: "Server"):
     """Prints a message when the server starts."""
+    scheme = "https" if server.https else "http"
     host, port = server.host, server.port
 
-    print(f"Started development server on http://{host}:{port}")
+    print(f"Started development server on {scheme}://{host}:{port}")
 
 
 def _debug_response_sent(response: "Response", time_elapsed: float):

docs/examples.rst

@@ -196,7 +196,7 @@ It is important to use correct ``enctype``, depending on the type of data you wa
 - ``application/x-www-form-urlencoded`` - For sending simple text data without any special characters including spaces.
     If you use it, values will be automatically parsed as strings, but special characters will be URL encoded
     e.g. ``"Hello World! ^-$%"`` will be saved as ``"Hello+World%21+%5E-%24%25"``
-- ``multipart/form-data`` - For sending textwith special characters and files
+- ``multipart/form-data`` - For sending text with special characters and files
     When used, non-file values will be automatically parsed as strings and non plain text files will be saved as ``bytes``.
     e.g. ``"Hello World! ^-$%"`` will be saved as ``'Hello World! ^-$%'``, and e.g. a PNG file will be saved as ``b'\x89PNG\r\n\x1a\n\x00\...``.
 - ``text/plain`` - For sending text data with special characters.
@@ -322,8 +322,10 @@ This can be overcomed by periodically polling the server, but it is not an elega
 Response is initialized on ``return``, events can be sent using ``.send_event()`` method. Due to the nature of SSE, it is necessary to store the
 response object somewhere, so that it can be accessed later.
 
-**Because of the limited number of concurrently open sockets, it is not possible to process more than one SSE response at the same time.
-This might change in the future, but for now, it is recommended to use SSE only with one client at a time.**
+
+.. warning::
+    Because of the limited number of concurrently open sockets, it is **not possible to process more than one SSE response at the same time**.
+    This might change in the future, but for now, it is recommended to use SSE **only with one client at a time**.
 
 .. literalinclude:: ../examples/httpserver_sse.py
     :caption: examples/httpserver_sse.py
@@ -344,8 +346,9 @@ This is anologous to calling ``.poll()`` on the ``Server`` object.
 The following example uses ``asyncio``, which has to be installed separately. It is not necessary to use ``asyncio`` to use Websockets,
 but it is recommended as it makes it easier to handle multiple tasks. It can be used in any of the examples, but here it is particularly useful.
 
-**Because of the limited number of concurrently open sockets, it is not possible to process more than one Websocket response at the same time.
-This might change in the future, but for now, it is recommended to use Websocket only with one client at a time.**
+.. warning::
+    Because of the limited number of concurrently open sockets, it is **not possible to process more than one Websocket response at the same time**.
+    This might change in the future, but for now, it is recommended to use Websocket **only with one client at a time**.
 
 .. literalinclude:: ../examples/httpserver_websocket.py
     :caption: examples/httpserver_websocket.py
@@ -369,6 +372,35 @@ video to multiple clients while simultaneously handling other requests.
     :emphasize-lines: 31-77,92
     :linenos:
 
+HTTPS
+-----
+
+.. warning::
+    HTTPS on CircuitPython **works only on boards with enough memory e.g. ESP32-S3**.
+
+When you want to expose your server to the internet or an untrusted network, it is recommended to use HTTPS.
+Together with authentication, it provides a relatively secure way to communicate with the server.
+
+.. note::
+    Using HTTPS slows down the server, because of additional work with encryption and decryption.
+
+Enabling HTTPS is straightforward and comes down to passing the path to the certificate and key files to the ``Server`` constructor
+and setting ``https=True``.
+
+.. literalinclude:: ../examples/httpserver_https.py
+    :caption: examples/httpserver_https.py
+    :emphasize-lines: 15-17
+    :linenos:
+
+
+To create your own certificate, you can use the following command:
+
+.. code-block:: bash
+
+  sudo openssl req -x509 -nodes -days 365 -newkey rsa:2048 -keyout key.pem -out cert.pem
+
+You might have to change permissions of the files, so that the server can read them.
+
 Multiple servers
 ----------------
 
@@ -378,7 +410,7 @@ Using ``.serve_forever()`` for this is not possible because of it's blocking beh
 
 Each server **must have a different port number**.
 
-In order to distinguish between responses from different servers a 'X-Server' header is added to each response.
+To distinguish between responses from different servers a 'X-Server' header is added to each response.
 **This is an optional step**, both servers will work without it.
 
 In combination with separate authentication and diffrent ``root_path`` this allows creating moderately complex setups.
@@ -421,5 +453,5 @@ This is the default format of the logs::
 If you need more information about the server or request, or you want it in a different format you can modify
 functions at the bottom of ``adafruit_httpserver/server.py`` that start with ``_debug_...``.
 
-NOTE:
-*This is an advanced usage that might change in the future. It is not recommended to modify other parts of the code.*
+.. note::
+    This is an advanced usage that might change in the future. It is not recommended to modify other parts of the code.

examples/httpserver_https.py

@@ -0,0 +1,30 @@
+# SPDX-FileCopyrightText: 2024 Michał Pokusa
+#
+# SPDX-License-Identifier: Unlicense
+
+import socketpool
+import wifi
+
+from adafruit_httpserver import Server, Request, Response
+
+
+pool = socketpool.SocketPool(wifi.radio)
+server = Server(
+    pool,
+    root_path="/static",
+    https=True,
+    certfile="cert.pem",
+    keyfile="key.pem",
+    debug=True,
+)
+
+
+@server.route("/")
+def base(request: Request):
+    """
+    Serve a default static plain text message.
+    """
+    return Response(request, "Hello from the CircuitPython HTTPS Server!")
+
+
+server.serve_forever(str(wifi.radio.ipv4_address), 443)