#!/usr/bin/env python
#
# Copyright (c) 2016, NORDUnet A/S All rights reserved.
#
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# TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
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"""
Utility to upload a new firmware image or FPGA bitstream.
"""

import os
import sys
import time
import struct
import serial
import getpass
import os.path
import tarfile
import argparse
import platform

from binascii import crc32

FIRMWARE_CHUNK_SIZE = 4096
FPGA_CHUNK_SIZE = 4096


def parse_args():
    """
    Parse the command line arguments
    """

    share_directory = "/usr/share" if platform.system() == "Linux" else "/usr/local/share"

    default_tarball = os.path.join(share_directory, "cryptech-alpha-firmware.tar.gz")

    if not os.path.exists(default_tarball):
        default_tarball = None

    parser = argparse.ArgumentParser(description = __doc__,
                                     formatter_class = argparse.ArgumentDefaultsHelpFormatter,
                                     )

    parser.add_argument("-d", "--device",
                        default = os.getenv("CRYPTECH_CTY_CLIENT_SERIAL_DEVICE", "/dev/ttyUSB0"),
                        help = "Name of management port USB serial device",
                        )

    parser.add_argument("--firmware-tarball",
                        type = argparse.FileType("rb"),
                        default = default_tarball,
                        help = "Location of firmware tarball",
                        )

    parser.add_argument("--username",
                        choices = ("so", "wheel", "ct"),
                        default = "so",
                        help = "Username to use when logging into the HSM",
                        )

    actions = parser.add_mutually_exclusive_group(required = True)
    actions.add_argument("--fpga",
                         action = "store_true",
                         help = "Upload FPGA bitstream",
                         )
    actions.add_argument("--firmware", "--hsm",
                         action = "store_true",
                         help = "Upload HSM firmware image",
                         )
    actions.add_argument("--bootloader",
                         action = "store_true",
                         help = "Upload bootloader image (dangerous!)",
                         )

    parser.add_argument("--simon-says-whack-my-bootloader",
                        action = "store_true",
                        help = "Confirm that you really want to risk bricking the HSM",
                        )

    parser.add_argument("-i", "--explicit-image",
                        type = argparse.FileType("rb"),
                        help = "Explicit source image file for upload, overrides firmware tarball")

    return parser.parse_args()


def _write(dst, data):
    dst.write(data)
    if len(data) == 4:
        print("Wrote 0x{!s}".format(data.encode("hex")))
    else:
        print("Wrote {!r}".format(data))


def _read(dst):
    res = ""
    x = dst.read(1)
    while not x:
        x = dst.read(1)
    while x:
        res += x
        x = dst.read(1)
    print ("Read {!r}".format(res))
    return res

wheel_pin = 'YouReallyNeedToChangeThisPINRightNowWeAreNotKidding'

def _execute(dst, cmd):
    global wheel_pin
    pin = None
    if args.username == 'wheel':
        pin = wheel_pin
    if args.username == 'ct':
        pin = 'ct'
    _write(dst, "\r")
    prompt = _read(dst)
    if prompt.endswith("Username: "):
        _write(dst, args.username + "\r")
        prompt = _read(dst)
        if prompt.endswith("Password: "):
            if not pin:
                pin = getpass.getpass("{} PIN: ".format(args.username))
            _write(dst, pin + "\r")
            prompt = _read(dst)
    if not prompt.endswith(("> ", "# ")):
        print("Device does not seem to be ready for a file transfer (got {!r})".format(prompt))
        return prompt
    _write(dst, cmd + "\r")
    response = _read(dst)
    return response

def send_file(src, size, args, dst):
    if args.fpga:
        chunk_size = FPGA_CHUNK_SIZE
        response = _execute(dst, "fpga bitstream upload")
    elif args.firmware:
        chunk_size = FIRMWARE_CHUNK_SIZE
        response = _execute(dst, "firmware upload")
        if "Rebooting" in response:
            response = _execute(dst, "firmware upload")
    elif args.bootloader:
        chunk_size = FIRMWARE_CHUNK_SIZE
        response = _execute(dst, "bootloader upload")
    if "Access denied" in response:
        print "Access denied"
        return False
    if not "OK" in response:
        print("Device did not accept the upload command (got {!r})".format(response))
        return False

    crc = 0
    counter = 0
    # 1. Write size of file (4 bytes)
    _write(dst, struct.pack("<I", size))
    response = _read(dst)
    if not response.startswith("Send "):
        print response
        return False

    # 2. Write file contents while calculating CRC-32
    while True:
        data = src.read(chunk_size)
        if not data:
            break
        dst.write(data)
        print("Wrote {!s} bytes (chunk {!s}/{!s})".format(len(data), counter, int(size / chunk_size)))
        # read ACK (a counter of number of 4k chunks received)
        while True:
            ack_bytes = dst.read(4)
            if len(ack_bytes) == 4:
                break
            print("ERROR: Did not receive an ACK, got {!r}".format(ack_bytes))
            dst.write("\r")  # eventually get back to the CLI prompt
        ack = struct.unpack("<I", ack_bytes)[0]
        if ack != counter + 1:
            print("ERROR: Did not receive the expected counter as ACK (got {!r}/{!r}, not {!r})".format(ack, ack_bytes, counter))
            flush = dst.read(100)
            print("FLUSH data: {!r}".format(flush))
            return False
        counter += 1

        crc = crc32(data, crc) & 0xffffffff

    _read(dst)

    # 3. Write CRC-32 (4 bytes)
    _write(dst, struct.pack("<I", crc))
    response = _read(dst)
    print response

    src.close()

    if args.fpga:
        # tell the fpga to read its new configuration
        _execute(dst, "fpga reset")

    if args.fpga or args.bootloader:
        # log out of the CLI
        # firmware upgrade reboots, doesn't need an exit
        _execute(dst, "exit")

    return True


dire_bootloader_warning = '''
                            WARNING

Updating the bootloader risks bricking your HSM!  If something goes
badly wrong here, or you upload a bad bootloader image, you will not
be able to recover without an ST-LINK programmer.

In most cases a normal "--firmware" upgrade should be all that is
necessary to bring your HSM up to date, there is seldom any real need
to update the bootloader.

Do not proceed with this unless you REALLY know what you are doing.

If you got here by accident, ^C now, without answering the PIN prompt.
'''


def main():
    global args
    args = parse_args()

    if args.bootloader and not args.simon_says_whack_my_bootloader:
        sys.exit("You didn't say \"Simon says\"")

    if args.bootloader:
        print dire_bootloader_warning

    if args.explicit_image is None and args.firmware_tarball is None:
        sys.exit("No source file specified for upload and firmware tarball not found")

    if args.explicit_image:
        src = args.explicit_image       # file-like object, thanks to argparse
        size = os.fstat(src.fileno()).st_size
        if size == 0:                   # Flashing from stdin won't work, sorry
            sys.exit("Can't flash from a pipe or zero-length file")
        print "Uploading from explicitly-specified file {}".format(args.explicit_image.name)

    else:
        tar = tarfile.open(fileobj = args.firmware_tarball)
        print "Firmware tarball {} content:".format(args.firmware_tarball.name)
        tar.list(True)
        if args.fpga:
            name = "alpha_fmc.bit"
        elif args.firmware:
            name = "hsm.bin"
        elif args.bootloader:
            name = "bootloader.bin"
        else:
            # Somebody updated other part of this script without updating this part :(
            sys.exit("Don't know which component to select from firmware tarball, sorry")
        try:
            size = tar.getmember(name).size
        except KeyError:
            sys.exit("Expected component {} missing from firmware tarball {}".format(name, args.firmware_tarball.name))
        src = tar.extractfile(name)
        print "Uploading {} from {}".format(name, args.firmware_tarball.name)

    print "Initializing serial port and synchronizing with HSM, this may take a few seconds"
    dst  = serial.Serial(args.device, 921600, timeout = 2)
    send_file(src, size, args, dst)
    dst.close()


if __name__ == "__main__":
    try:
        main()
    except KeyboardInterrupt:
        pass