path: root/projects/hsm/cryptech_probe

#!/usr/bin/env python
#
# Copyright (c) 2016, 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
# met:
# - Redistributions of source code must retain the above copyright notice,
#   this list of conditions and the following disclaimer.
#
# - Redistributions in binary form must reproduce the above copyright
#   notice, this list of conditions and the following disclaimer in the
#   documentation and/or other materials provided with the distribution.
#
# - Neither the name of the NORDUnet nor the names of its contributors may
#   be used to endorse or promote products derived from this software
#   without specific prior written permission.
#
# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
# IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
# TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
# PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
# 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.

"""
Utility to probe USB serial port(s) trying to figure out which one(s)
we have plugged in today.  stdout is environment variable settings,
suitable for use in bash with "eval `cryptech_probe`"; all other output
goes to stderr.
"""

import sys
import time
import argparse
import serial.tools.list_ports_posix

class positive_integer(int):
    def __init__(self, value):
        if self <= 0:
            raise ValueError

parser = argparse.ArgumentParser(formatter_class = argparse.ArgumentDefaultsHelpFormatter)
parser.add_argument("-v", "--verbose",    action = "store_true",   help = "produce human-readable output")
parser.add_argument("-d", "--debug",      action = "store_true",   help = "blather about what we're doing")
parser.add_argument("--no-cleanup",       action = "store_true",   help = "don't send cleanup sequences after probing")
parser.add_argument("--read-buffer-size", type = positive_integer, help = "size of read buffer", default = 1024)
args = parser.parse_args()

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

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

# This is the query string we send to each USB port we find.  It's
# intended to be relatively harmless, at least for either of the HSM
# ports: the final Control-U should prevent the console from trying to
# interpret the RPC command, and the SLIP_END markers should cause
# the RPC server to treat the ASCII control characters as noise.
#
# Yes, this is a total kludge.  Useful identifiers for the USB ports
# are are on the wish list for a future revision of the hardware, but
# for the moment, we do what we can with what we have.

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

ports = [port for port, desc, hwid in serial.tools.list_ports_posix.comports()
         if "VID:PID=0403:6014" in hwid]

if not ports:
    sys.exit("Couldn't find any likely USB ports")

if args.debug:
    sys.stderr.write("Candidate USB ports: {}\n".format(", ".join(ports)))

env = {}

for port in ports:

    while True:
        try:
            tty = serial.Serial(port, 921600, timeout=0.1)
            break
        except serial.SerialException:
            time.sleep(0.2)

    for c in probe_string:
        tty.write(c)
        time.sleep(0.1)

    response = tty.read(args.read_buffer_size)
    if args.debug:
        sys.stderr.write("Received from {}: {!r} ({})\n".format(port, response, ":".join("{:02x}".format(ord(c)) for c in response)))

    # Check whether we got a known console prompt.

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

    # Check whether we got something that looks like the response to an RPC version query.
    # We skip over the version value itself, as it might change, but we check that it's
    # terminated properly.  This is fragile, and will need to handle SLIP decoding if
    # we ever bump one of the version fields up into the range where the SLIP control
    # characters live, but it will do for the moment.

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

    if is_cty and args.verbose:
        sys.stderr.write("{} looks like the Cryptech HSM console port\n".format(port))

    if is_hsm and args.verbose:
        sys.stderr.write("{} looks like the Cryptech HSM RPC port\n".format(port))

    if is_cty:
        env.update(CRYPTECH_CTY_CLIENT_SERIAL_DEVICE = port)

    if is_hsm:
        env.update(CRYPTECH_RPC_CLIENT_SERIAL_DEVICE = port)

    if (is_cty or is_hsm) and not args.no_cleanup:
        if is_cty:
            tty.write(Control_U)
        if is_hsm:
            tty.write(SLIP_END)
        while tty.read(args.read_buffer_size):
            pass

    tty.close()

if env:
    sys.stdout.write("export {}\n".format(
        " ".join("{}='{}'".format(var, env[var]) for var in sorted(env))))