path: root/cryptech_muxd

#!/usr/bin/env python
#
# Copyright (c) 2016-2017, NORDUnet A/S All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions are
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# - Redistributions in binary form must reproduce the above copyright
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# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
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# TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
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# HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
# TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
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# SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

"""
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 binascii
import logging.handlers

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

from cryptech.libhal import HAL_OK, RPC_FUNC_GET_VERSION, RPC_FUNC_LOGOUT, RPC_FUNC_LOGOUT_ALL


logger = logging.getLogger("cryptech_muxd")


SLIP_END     = b"\300"          # Indicates end of SLIP packet
SLIP_ESC     = b"\333"          # Indicates byte stuffing
SLIP_ESC_END = b"\334"          # ESC ESC_END means END data byte
SLIP_ESC_ESC = b"\335"          # ESC ESC_ESC means ESC data byte

Control_U    = b"\025"          # Console: clear line
Control_M    = b"\015"          # 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:]


logout_msg     = struct.pack(">LL", RPC_FUNC_LOGOUT,     0)
logout_all_msg = struct.pack(">LL", RPC_FUNC_LOGOUT_ALL, 0)


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

    # In theory, we want zero (non-blocking mode) for both the read
    # and write timeouts here so that PySerial will let Tornado handle
    # all the select()/poll()/epoll()/kqueue() fun, delivering maximum
    # throughput to all.  In practice, this has always worked for the
    # author, but another developer reports that on some (not all)
    # platforms this fails consistently with Tornado reporting write
    # timeout errors, presumably as the result of receiving an IOError
    # or OSError exception from PySerial.  For reasons we don't really
    # understand, setting a PySerial write timeout on the order of
    # 50-100 ms "solves" this problem.  Again in theory, this will
    # result in lower throughput if PySerial spends too much time
    # blocking on a single serial device when Tornado could be doing
    # something useful elsewhere, but such is life.

    def __init__(self, device):
        self.serial = serial.Serial(device, 921600, timeout = 0, write_timeout = 0.1)
        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)

    if tornado.version > "5":
        # .. versionchanged:: 5.0
        # Interface redesigned to take a buffer and return a number
        # of bytes instead of a freshly-allocated object.
        def read_from_fd(self, buf):
            buf[:] = self.serial.read(len(buf))
            return len(buf) or None
    else:
        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 = 0o600):
        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 = 0, queue = None):
        "Send a query to the HSM."
        logger.debug("RPC send: %s", ":".join(binascii.hexlify(c) for c in query))
        if queue is not None:
            self.queues[handle] = queue
        with (yield self.rpc_input_lock.acquire()):
            yield self.write(query)
        logger.debug("RPC sent")

    @tornado.gen.coroutine
    def rpc_output_loop(self):
        "Handle reply stream HSM -> network."
        while True:
            try:
                logger.debug("RPC UART read")
                reply = yield self.read_until(SLIP_END)
            except tornado.iostream.StreamClosedError:
                logger.info("RPC UART closed")
                for q in self.queues.values():
                    q.put_nowait(None)
                return
            logger.debug("RPC recv: %s", ":".join(binascii.hexlify(c) for c in reply))
            if reply == SLIP_END:
                continue
            try:
                handle = client_handle_get(slip_decode(reply))
            except:
                logger.debug("RPC skipping bad packet")
                continue
            if handle not in self.queues:
                logger.debug("RPC ignoring response: handle 0x%x", handle)
                continue
            logger.debug("RPC queue put: handle 0x%x, qsize %s", handle, self.queues[handle].qsize())
            self.queues[handle].put_nowait(reply)

    def logout_all(self):
        "Execute an RPC LOGOUT_ALL operation."
        return self.rpc_input(slip_encode(logout_all_msg))


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."
        handle = self.next_client_handle()
        queue  = tornado.queues.Queue()
        logger.info("RPC connected %r, handle 0x%x", stream, handle)
        while True:
            try:
                logger.debug("RPC socket read, handle 0x%x", handle)
                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)
                logger.debug("RPC queue wait, handle 0x%x", handle)
                reply = yield queue.get()
                if reply is None:
                    raise QueuedStreamClosedError()
                logger.debug("RPC socket write, handle 0x%x", handle)
                yield stream.write(SLIP_END + reply)
            except tornado.iostream.StreamClosedError:
                logger.info("RPC closing %r, handle 0x%x", stream, handle)
                stream.close()
                query = slip_encode(client_handle_set(logout_msg, handle))
                yield self.serial.rpc_input(query, handle)
                return

    client_handle = int(time.time()) << 4

    @classmethod
    def next_client_handle(cls):
        cls.client_handle += 1
        cls.client_handle &= 0xFFFFFFFF
        return cls.client_handle


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

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

    @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:
                futures = []
                if self.console_log is not None:
                    futures.append(self.console_log.write(buffer))
                if self.attached_cty is not None:
                    futures.append(self.attached_cty.write(buffer))
                if futures:
                    yield futures
            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 disconnected 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.items():

            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 = struct.pack(">LL",  RPC_FUNC_GET_VERSION, 0)
        RPC_reply = struct.pack(">LLL", RPC_FUNC_GET_VERSION, 0, HAL_OK)

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

        yield self.write(probe_string)
        yield tornado.gen.sleep(0.5)
        response = yield self.read_bytes(self.read_chunk_size, partial = True)

        logger.debug("Probing %s: %r %s", self.serial_device, response, ":".join(binascii.hexlify(c) for c in response))

        is_cty = any(prompt in response for prompt in (b"Username:", b"Password:", b"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("-l", "--log-file",
                        help = "log to file instead of stderr")

    parser.add_argument("-L", "--console-log",
                        type = argparse.FileType("a"),
                        help = "log console output to file")

    parser.add_argument("-p", "--probe",
                        nargs = "*",
                        metavar = "DEVICE",
                        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("--rpc-socket-mode",
                        help    = "permission bits for RPC socket inode",
                        default = 0o600, type = lambda s: int(s, 8))

    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"))

    parser.add_argument("--cty-socket-mode",
                        help    = "permission bits for CTY socket inode",
                        default = 0o600, type = lambda s: int(s, 8))

    args = parser.parse_args()

    if args.log_file is not None:
        logging.getLogger().handlers[:] = [logging.handlers.WatchedFileHandler(args.log_file)]

    logging.getLogger().handlers[0].setFormatter(
        logging.Formatter("%(asctime)-15s %(name)s[%(process)d]:%(levelname)s: %(message)s",
                          "%Y-%m-%d %H:%M:%S"))

    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)

    if args.console_log is not None:
        console_log = tornado.iostream.PipeIOStream(args.console_log.fileno())
    else:
        console_log = None

    futures = []

    if args.rpc_device is None:
        logger.warn("No RPC device found")
    else:
        rpc_stream = RPCIOStream(device = args.rpc_device)
        rpc_server = RPCServer(rpc_stream, args.rpc_socket, args.rpc_socket_mode)
        futures.append(rpc_stream.rpc_output_loop())
        futures.append(rpc_stream.logout_all())

    if args.cty_device is None:
        logger.warn("No CTY device found")
    else:
        cty_stream = CTYIOStream(device = args.cty_device, console_log = console_log)
        cty_server = CTYServer(cty_stream, args.cty_socket, args.cty_socket_mode)
        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?

    if futures:
        yield futures

if __name__ == "__main__":
    try:
        tornado.ioloop.IOLoop.current().run_sync(main)
    except (SystemExit, KeyboardInterrupt):
        pass
    except:
        logger.exception("Unhandled exception")
    else:
        logger.debug("Main loop exited")