#!/usr/bin/env python3
import sys
import struct
import binascii
import ed25519
import pyblake2


def sign_data(seckey, data):
    signkey = ed25519.SigningKey(seckey)
    digest = pyblake2.blake2s(data).digest()
    return signkey.sign(digest)

def format_sigmask(sigmask):
    bits = [ str(b + 1) if sigmask & (1<<b) else '.' for b in range(8) ]
    return '0x%02x = [%s]' % (sigmask, ' '.join(bits))


# loader/firmware headers specification: https://github.com/trezor/trezor-core/blob/master/docs/bootloader.md


class BinImage:

    def __init__(self, data, magic, max_size):
        header = struct.unpack('<4sIIIBBBB427sB64s', data[:512])
        self.magic, \
        self.hdrlen, \
        self.expiry, \
        self.codelen, \
        self.vmajor, \
        self.vminor, \
        self.vpatch, \
        self.vbuild, \
        self.reserved, \
        self.sigmask, \
        self.sig = header
        assert self.magic == magic
        assert self.hdrlen == 512
        total_len = self.hdrlen + self.codelen
        assert total_len % 512 == 0
        assert total_len >= 4 * 1024
        assert total_len <= max_size
        assert self.reserved == 427 * b'\x00'
        self.code = data[self.hdrlen:]
        assert len(self.code) == self.codelen

    def print(self):
        if self.magic == b'TRZF':
            print('TREZOR Firmware Image')
            total_len = self.vhdrlen + self.hdrlen + self.codelen
        elif self.magic == b'TRZL':
            print('TREZOR Loader Image')
            total_len = self.hdrlen + self.codelen
        else:
            print('TREZOR Unknown Image')
        print('  * magic   :', self.magic.decode('ascii'))
        print('  * hdrlen  :', self.hdrlen)
        print('  * expiry  :', self.expiry)
        print('  * codelen :', self.codelen)
        print('  * version : %d.%d.%d.%d' % (self.vmajor, self.vminor, self.vpatch, self.vbuild))
        print('  * sigmask :', format_sigmask(self.sigmask))
        print('  * sig     :', binascii.hexlify(self.sig).decode('ascii'))
        print('  * total   : %d bytes' % total_len)
        print()

    def serialize_header(self, sig=True):
        header = struct.pack('<4sIIIBBBB427s', \
            self.magic, self.hdrlen, self.expiry, self.codelen, \
            self.vmajor, self.vminor, self.vpatch, self.vbuild, \
            self.reserved)
        if sig:
            header += struct.pack('<B64s', self.sigmask, self.sig)
        else:
            header += 65 * b'\x00'
        assert len(header) == self.hdrlen
        return header

    def sign(self, sigmask, seckey):
        header = self.serialize_header(sig=False)
        data = header + self.code
        assert len(data) == self.hdrlen + self.codelen
        self.sigmask = sigmask
        self.sig = sign_data(seckey, data)

    def write(self, filename):
        with open(filename, 'wb') as f:
            f.write(self.serialize_header())
            f.write(self.code)


class FirmwareImage(BinImage):

    def __init__(self, data, vhdrlen):
        super().__init__(data[vhdrlen:], magic=b'TRZF', max_size=7*128*1024)
        self.vhdrlen = vhdrlen
        self.vheader = data[:vhdrlen]

    def write(self, filename):
        with open(filename, 'wb') as f:
            f.write(self.vheader)
            f.write(self.serialize_header())
            f.write(self.code)

class LoaderImage(BinImage):

    def __init__(self, data):
        super().__init__(data, magic=b'TRZL', max_size=64*1024 + 7*128*1024)


class VendorHeader:

    def __init__(self, data):
        header = struct.unpack('<4sIIBBBB', data[:16])
        self.magic, \
        self.hdrlen, \
        self.expiry, \
        self.vmajor, \
        self.vminor, \
        self.vsig_m, \
        self.vsig_n = header
        assert self.magic == b'TRZV'
        assert self.vsig_m > 0 and self.vsig_m <= self.vsig_n
        assert self.vsig_n > 0 and self.vsig_n <= 8
        p = 16
        self.vpub = []
        for _ in range(self.vsig_n):
            self.vpub.append(data[p:p + 32])
            p += 32
        self.vstr_len = data[p]
        p += 1
        self.vstr = data[p:p + self.vstr_len]
        p += self.vstr_len
        vstr_pad = -p & 3
        p += vstr_pad
        self.vimg_len = len(data) - 65 - p
        self.vimg = data[p:p + self.vimg_len]
        p += self.vimg_len
        self.sigmask = data[p]
        p += 1
        self.sig = data[p:p+64]
        assert len(data) == 4 + 4 + 4 + 1 + 1 + 1 + 1 + \
                            32 * len(self.vpub) + \
                            1 + self.vstr_len + vstr_pad + \
                            self.vimg_len + \
                            1 + 64

    def print(self):
        print('TREZOR Vendor Header')
        print('  * magic   :', self.magic.decode('ascii'))
        print('  * hdrlen  :', self.hdrlen)
        print('  * expiry  :', self.expiry)
        print('  * version : %d.%d' % (self.vmajor, self.vminor))
        print('  * scheme  : %d out of %d' % (self.vsig_m, self.vsig_n))
        for i in range(self.vsig_n):
            print('  * vpub #%d :' % (i + 1), binascii.hexlify(self.vpub[i]).decode('ascii'))
        print('  * vstr    :', self.vstr.decode('ascii'))
        print('  * vimg    : (%d bytes)' % len(self.vimg))
        print('  * sigmask :', format_sigmask(self.sigmask))
        print('  * sig     :', binascii.hexlify(self.sig).decode('ascii'))

    def serialize_header(self, sig=True):
        header = struct.pack('<4sIIBBBB', \
            self.magic, self.hdrlen, self.expiry, \
            self.vmajor, self.vminor, \
            self.vsig_m, self.vsig_n)
        for i in range(self.vsig_n):
            header += self.vpub[i]
        header += struct.pack('<B', self.vstr_len) + self.vstr
        header += (-len(header) & 3) * b'\x00' # vstr_pad
        header += self.vimg
        if sig:
            header += struct.pack('<B64s', self.sigmask, self.sig)
        else:
            header += 65 * b'\x00'
        assert len(header) == self.hdrlen
        return header

    def sign(self, sigmask, seckey):
        header = self.serialize_header(sig=False)
        self.sigmask = sigmask
        self.sig = sign_data(seckey, header)

    def write(self, filename):
        with open(filename, 'wb') as f:
            f.write(self.serialize_header())


def binopen(filename):
    data = open(filename, 'rb').read()
    magic = data[:4]
    if magic == b'TRZL':
        return LoaderImage(data)
    if magic == b'TRZV':
        vheader = VendorHeader(data)
        if len(data) == vheader.hdrlen:
            return vheader
        subdata = data[vheader.hdrlen:]
        if subdata[:4] == b'TRZF':
            return FirmwareImage(data, vheader.hdrlen)
    if magic == b'TRZF':
        return FirmwareImage(data, 0)
    raise Exception('Unknown file format')

def main():
    if len(sys.argv) < 2:
        print('Usage: binctl file.bin [-s index seckey]')
        return 1
    fn = sys.argv[1]
    sign = len(sys.argv) > 2 and sys.argv[2] == '-s'
    b = binopen(fn)
    if sign:
        sigmask = 1 << (int(sys.argv[3]) - 1)
        seckey = binascii.unhexlify(sys.argv[4])
        b.sign(sigmask, seckey)
        print()
        b.write(fn)
    b.print()


if __name__ == '__main__':
    main()