path: root/cryptech_muxd

#!/usr/bin/env python
#
# Copyright (c) 2016-2017, NORDUnet A/S All rights reserved.
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"""
Implementation of Cryptech RPC protocol multiplexer in Python.

Unlike the original C implementation, this uses SLIP encapsulation
over a SOCK_STREAM channel, because support for SOCK_SEQPACKET is not
what we might wish.  We outsource all the heavy lifting for serial and
network I/O to the PySerial and Tornado libraries, respectively.
"""

import os
import sys
import time
import struct
import atexit
import weakref
import logging
import argparse

import serial
import serial.tools.list_ports_posix

import tornado.tcpserver
import tornado.iostream
import tornado.netutil
import tornado.ioloop
import tornado.queues
import tornado.locks
import tornado.gen


logger = logging.getLogger("cryptech_muxd")


SLIP_END     = chr(0300)        # Indicates end of SLIP packet
SLIP_ESC     = chr(0333)        # Indicates byte stuffing
SLIP_ESC_END = chr(0334)        # ESC ESC_END means END data byte
SLIP_ESC_ESC = chr(0335)        # ESC ESC_ESC means ESC data byte

Control_U    = chr(0025)        # Console: clear line
Control_M    = chr(0015)        # Console: end of line


def slip_encode(buffer):
    "Encode a buffer using SLIP encapsulation."
    return SLIP_END + buffer.replace(SLIP_ESC, SLIP_ESC + SLIP_ESC_ESC).replace(SLIP_END, SLIP_ESC + SLIP_ESC_END) + SLIP_END

def slip_decode(buffer):
    "Decode a SLIP-encapsulated buffer."
    return buffer.strip(SLIP_END).replace(SLIP_ESC + SLIP_ESC_END, SLIP_END).replace(SLIP_ESC + SLIP_ESC_ESC, SLIP_ESC)


def client_handle_get(msg):
    "Extract client_handle field from a Cryptech RPC message."
    return struct.unpack(">L", msg[4:8])[0]

def client_handle_set(msg, handle):
    "Replace client_handle field in a Cryptech RPC message."
    return msg[:4] + struct.pack(">L", handle) + msg[8:]


class SerialIOStream(tornado.iostream.BaseIOStream):
    """
    Implementation of a Tornado IOStream over a PySerial device.
    """

    def __init__(self, device):
        self.serial = serial.Serial(device, 921600, timeout = 0, write_timeout = 0)
        self.serial_device = device
        super(SerialIOStream, self).__init__()

    def fileno(self):
        return self.serial.fileno()

    def close_fd(self):
        self.serial.close()

    def write_to_fd(self, data):
        return self.serial.write(data)

    def read_from_fd(self):
        return self.serial.read(self.read_chunk_size) or None


class PFUnixServer(tornado.tcpserver.TCPServer):
    """
    Variant on tornado.tcpserver.TCPServer, listening on a PF_UNIX
    (aka PF_LOCAL) socket instead of a TCP socket.
    """

    def __init__(self, serial_stream, socket_filename, mode = 0600):
        super(PFUnixServer, self).__init__()
        self.serial = serial_stream
        self.socket_filename = socket_filename
        self.add_socket(tornado.netutil.bind_unix_socket(socket_filename, mode))
        atexit.register(self.atexit_unlink)

    def atexit_unlink(self):
        try:
            os.unlink(self.socket_filename)
        except:
            pass


class RPCIOStream(SerialIOStream):
    """
    Tornado IOStream for a serial RPC channel.
    """

    def __init__(self, device):
        super(RPCIOStream, self).__init__(device)
        self.queues = weakref.WeakValueDictionary()
        self.rpc_input_lock = tornado.locks.Lock()

    @tornado.gen.coroutine
    def rpc_input(self, query, handle, queue):
        "Send a query to the HSM."
        logger.debug("rpc send: %s", ":".join("{:02x}".format(ord(c)) for c in query))
        self.queues[handle] = queue
        with (yield self.rpc_input_lock.acquire()):
            yield self.write(query)

    @tornado.gen.coroutine
    def rpc_output_loop(self):
        "Handle reply stream HSM -> network."
        while True:
            try:
                reply = yield self.read_until(SLIP_END)
            except tornado.iostream.StreamClosedError:
                logger.info("rpc uart closed")
                for q in self.queues.itervalues():
                    q.put_nowait(None)
                return
            logger.debug("rpc recv: %s", ":".join("{:02x}".format(ord(c)) for c in reply))
            try:
                handle = client_handle_get(slip_decode(reply))
            except:
                continue
            self.queues[handle].put_nowait(reply)


class QueuedStreamClosedError(tornado.iostream.StreamClosedError):
    "Deferred StreamClosedError passed throught a Queue."


class RPCServer(PFUnixServer):
    """
    Serve multiplexed Cryptech RPC over a PF_UNIX socket.
    """

    @tornado.gen.coroutine
    def handle_stream(self, stream, address):
        "Handle one network connection."
        logger.info("rpc connected %r", stream)
        handle = stream.socket.fileno()
        queue  = tornado.queues.Queue()
        while True:
            try:
                query = yield stream.read_until(SLIP_END)
                if len(query) < 9:
                    continue
                query = slip_encode(client_handle_set(slip_decode(query), handle))
                yield self.serial.rpc_input(query, handle, queue)
                reply = yield queue.get()
                if reply is None:
                    raise QueuedStreamClosedError()
                yield stream.write(SLIP_END + reply)
            except tornado.iostream.StreamClosedError:
                logger.info("rpc closing %r", stream)
                stream.close()
                return

class CTYIOStream(SerialIOStream):
    """
    Tornado IOStream for a serial console channel.
    """

    def __init__(self, device):
        super(CTYIOStream, self).__init__(device)
        self.attached_cty = None

    @tornado.gen.coroutine
    def cty_output_loop(self):
        while True:
            try:
                buffer = yield self.read_bytes(self.read_chunk_size, partial = True)
            except tornado.iostream.StreamClosedError:
                logger.info("cty uart closed")
                if self.attached_cty is not None:
                    self.attached_cty.close()
                return
            try:
                if self.attached_cty is not None:
                    yield self.attached_cty.write(buffer)
            except tornado.iostream.StreamClosedError:
                pass


class CTYServer(PFUnixServer):
    """
    Serve Cryptech console over a PF_UNIX socket.
    """

    @tornado.gen.coroutine
    def handle_stream(self, stream, address):
        "Handle one network connection."

        if self.serial.attached_cty is not None:
            yield stream.write("[Console already in use, sorry]\n")
            stream.close()
            return

        logger.info("cty connected to %r", stream)

        try:
            self.serial.attached_cty = stream
            while self.serial.attached_cty is stream:
                yield self.serial.write((yield stream.read_bytes(1024, partial = True)))
        except tornado.iostream.StreamClosedError:
            stream.close()
        finally:
            logger.info("cty disconnecting from %r", stream)
            if self.serial.attached_cty is stream:
                self.serial.attached_cty = None


class ProbeIOStream(SerialIOStream):
    """
    Tornado IOStream for probing a serial port.  This is nasty.
    """

    def __init__(self, device):
        super(ProbeIOStream, self).__init__(device)

    @classmethod
    @tornado.gen.coroutine
    def run_probes(cls, args):

        if args.rpc_device is not None and args.cty_device is not None:
            return

        if args.probe:
            devs = set(args.probe)
        else:
            devs = set(str(port)
                       for port, desc, hwid in serial.tools.list_ports_posix.comports()
                       if "VID:PID=0403:6014" in hwid)

        devs.discard(args.rpc_device)
        devs.discard(args.cty_device)

        if not devs:
            return

        logging.debug("Probing candidate devices %s", " ".join(devs))

        results = yield dict((dev, ProbeIOStream(dev).run_probe()) for dev in devs)

        for dev, result in results.iteritems():

            if result == "cty" and args.cty_device is None:
                logger.info("Selecting %s as cty device", dev)
                args.cty_device = dev

            if result == "rpc" and args.rpc_device is None:
                logger.info("Selecting %s as rpc device", dev)
                args.rpc_device = dev

    @tornado.gen.coroutine
    def run_probe(self):

        RPC_query = chr(0) * 8  # client_handle = 0, function code = RPC_FUNC_GET_VERSION
        RPC_reply = chr(0) * 12 # opcode = RPC_FUNC_GET_VERSION, client_handle = 0, valret = HAL_OK

        probe_string = SLIP_END + Control_U + SLIP_END + RPC_query + SLIP_END + Control_U + Control_M

        yield self.write(probe_string)

        response = yield self.read_bytes(self.read_chunk_size, partial = True)

        logger.debug("Probing %s: %r %s", self.serial_device, response, ":".join("{:02x}".format(ord(c)) for c in response))

        is_cty = any(prompt in response for prompt in ("Username:", "Password:", "cryptech>"))

        try:
            is_rpc = response[response.index(SLIP_END + RPC_reply) + len(SLIP_END + RPC_reply) + 4] == SLIP_END
        except ValueError:
            is_rpc = False
        except IndexError:
            is_rpc = False

        assert not is_cty or not is_rpc

        result = None

        if is_cty:
            result = "cty"
            yield self.write(Control_U)

        if is_rpc:
            result = "rpc"
            yield self.write(SLIP_END)

        self.close()
        raise tornado.gen.Return(result)



@tornado.gen.coroutine
def main():
    parser = argparse.ArgumentParser(formatter_class = argparse.ArgumentDefaultsHelpFormatter)

    parser.add_argument("-v", "--verbose",
                        action = "count",
                        help = "blather about what we're doing")

    parser.add_argument("-p", "--probe",
                        nargs = "*",
                        help = "probe for device UARTs")

    parser.add_argument("--rpc-device",
                        help    = "RPC serial device name",
                        default = os.getenv("CRYPTECH_RPC_CLIENT_SERIAL_DEVICE"))

    parser.add_argument("--rpc-socket",
                        help    = "RPC PF_UNIX socket name",
                        default = os.getenv("CRYPTECH_RPC_CLIENT_SOCKET_NAME",
                                            "/tmp/.cryptech_muxd.rpc"))

    parser.add_argument("--cty-device",
                        help    = "CTY serial device name",
                        default = os.getenv("CRYPTECH_CTY_CLIENT_SERIAL_DEVICE"))

    parser.add_argument("--cty-socket",
                        help    = "CTY PF_UNIX socket name",
                        default = os.getenv("CRYPTECH_CTY_CLIENT_SOCKET_NAME",
                                            "/tmp/.cryptech_muxd.cty"))

    args = parser.parse_args()

    if args.verbose:
        logging.getLogger().setLevel(logging.DEBUG if args.verbose > 1 else logging.INFO)

    if args.probe is not None:
        yield ProbeIOStream.run_probes(args)

    futures = []

    rpc_stream = RPCIOStream(device = args.rpc_device)
    rpc_server = RPCServer(rpc_stream, args.rpc_socket)
    futures.append(rpc_stream.rpc_output_loop())

    cty_stream = CTYIOStream(device = args.cty_device)
    cty_server = CTYServer(cty_stream, args.cty_socket)
    futures.append(cty_stream.cty_output_loop())

    # Might want to use WaitIterator(dict(...)) here so we can
    # diagnose and restart output loops if they fail.  Worry about
    # that when we get to automatic device probing.

    yield futures

if __name__ == "__main__":
    try:
        tornado.ioloop.IOLoop.current().run_sync(main)
    except KeyboardInterrupt:
        pass