#!/usr/bin/env python
# -*- coding: utf-8 -*-

from __future__ import with_statement

# ignobleepub.pyw, version 3.6
# Copyright © 2009-2010 by i♥cabbages

# Released under the terms of the GNU General Public Licence, version 3
# <http://www.gnu.org/licenses/>

# Modified 2010–2012 by some_updates, DiapDealer and Apprentice Alf

# Windows users: Before running this program, you must first install Python 2.6
#   from <http://www.python.org/download/> and PyCrypto from
#   <http://www.voidspace.org.uk/python/modules.shtml#pycrypto> (make sure to
#   install the version for Python 2.6).  Save this script file as
#   ineptepub.pyw and double-click on it to run it.
#
# Mac OS X users: Save this script file as ineptepub.pyw.  You can run this
#   program from the command line (pythonw ineptepub.pyw) or by double-clicking
#   it when it has been associated with PythonLauncher.

# Revision history:
#   1 - Initial release
#   2 - Added OS X support by using OpenSSL when available
#   3 - screen out improper key lengths to prevent segfaults on Linux
#   3.1 - Allow Windows versions of libcrypto to be found
#   3.2 - add support for encoding to 'utf-8' when building up list of files to cecrypt from encryption.xml
#   3.3 - On Windows try PyCrypto first and OpenSSL next
#   3.4 - Modify interace to allow use with import
#   3.5 - Fix for potential problem with PyCrypto
#   3.6 - Revised to allow use in calibre plugins to eliminate need for duplicate code

"""
Decrypt Barnes & Noble encrypted ePub books.
"""

__license__ = 'GPL v3'
__version__ = "3.6"

import sys
import os
import traceback
import zlib
import zipfile
from zipfile import ZipFile, ZIP_STORED, ZIP_DEFLATED
from contextlib import closing
import xml.etree.ElementTree as etree

# Wrap a stream so that output gets flushed immediately
# and also make sure that any unicode strings get
# encoded using "replace" before writing them.
class SafeUnbuffered:
    def __init__(self, stream):
        self.stream = stream
        self.encoding = stream.encoding
        if self.encoding == None:
            self.encoding = "utf-8"
    def write(self, data):
        if isinstance(data,unicode):
            data = data.encode(self.encoding,"replace")
        self.stream.write(data)
        self.stream.flush()
    def __getattr__(self, attr):
        return getattr(self.stream, attr)

try:
    from calibre.constants import iswindows, isosx
except:
    iswindows = sys.platform.startswith('win')
    isosx = sys.platform.startswith('darwin')

def unicode_argv():
    if iswindows:
        # Uses shell32.GetCommandLineArgvW to get sys.argv as a list of Unicode
        # strings.

        # Versions 2.x of Python don't support Unicode in sys.argv on
        # Windows, with the underlying Windows API instead replacing multi-byte
        # characters with '?'.


        from ctypes import POINTER, byref, cdll, c_int, windll
        from ctypes.wintypes import LPCWSTR, LPWSTR

        GetCommandLineW = cdll.kernel32.GetCommandLineW
        GetCommandLineW.argtypes = []
        GetCommandLineW.restype = LPCWSTR

        CommandLineToArgvW = windll.shell32.CommandLineToArgvW
        CommandLineToArgvW.argtypes = [LPCWSTR, POINTER(c_int)]
        CommandLineToArgvW.restype = POINTER(LPWSTR)

        cmd = GetCommandLineW()
        argc = c_int(0)
        argv = CommandLineToArgvW(cmd, byref(argc))
        if argc.value > 0:
            # Remove Python executable and commands if present
            start = argc.value - len(sys.argv)
            return [argv[i] for i in
                    xrange(start, argc.value)]
        return [u"ineptepub.py"]
    else:
        argvencoding = sys.stdin.encoding
        if argvencoding == None:
            argvencoding = "utf-8"
        return [arg if (type(arg) == unicode) else unicode(arg,argvencoding) for arg in sys.argv]


class IGNOBLEError(Exception):
    pass

def _load_crypto_libcrypto():
    from ctypes import CDLL, POINTER, c_void_p, c_char_p, c_int, c_long, \
        Structure, c_ulong, create_string_buffer, cast
    from ctypes.util import find_library

    if iswindows:
        libcrypto = find_library('libeay32')
    else:
        libcrypto = find_library('crypto')

    if libcrypto is None:
        raise IGNOBLEError('libcrypto not found')
    libcrypto = CDLL(libcrypto)

    AES_MAXNR = 14

    c_char_pp = POINTER(c_char_p)
    c_int_p = POINTER(c_int)

    class AES_KEY(Structure):
        _fields_ = [('rd_key', c_long * (4 * (AES_MAXNR + 1))),
                    ('rounds', c_int)]
    AES_KEY_p = POINTER(AES_KEY)

    def F(restype, name, argtypes):
        func = getattr(libcrypto, name)
        func.restype = restype
        func.argtypes = argtypes
        return func

    AES_set_decrypt_key = F(c_int, 'AES_set_decrypt_key',
                            [c_char_p, c_int, AES_KEY_p])
    AES_cbc_encrypt = F(None, 'AES_cbc_encrypt',
                        [c_char_p, c_char_p, c_ulong, AES_KEY_p, c_char_p,
                         c_int])

    class AES(object):
        def __init__(self, userkey):
            self._blocksize = len(userkey)
            if (self._blocksize != 16) and (self._blocksize != 24) and (self._blocksize != 32) :
                raise IGNOBLEError('AES improper key used')
                return
            key = self._key = AES_KEY()
            rv = AES_set_decrypt_key(userkey, len(userkey) * 8, key)
            if rv < 0:
                raise IGNOBLEError('Failed to initialize AES key')

        def decrypt(self, data):
            out = create_string_buffer(len(data))
            iv = ("\x00" * self._blocksize)
            rv = AES_cbc_encrypt(data, out, len(data), self._key, iv, 0)
            if rv == 0:
                raise IGNOBLEError('AES decryption failed')
            return out.raw

    return AES

def _load_crypto_pycrypto():
    from Crypto.Cipher import AES as _AES

    class AES(object):
        def __init__(self, key):
            self._aes = _AES.new(key, _AES.MODE_CBC, '\x00'*16)

        def decrypt(self, data):
            return self._aes.decrypt(data)

    return AES

def _load_crypto():
    AES = None
    cryptolist = (_load_crypto_libcrypto, _load_crypto_pycrypto)
    if sys.platform.startswith('win'):
        cryptolist = (_load_crypto_pycrypto, _load_crypto_libcrypto)
    for loader in cryptolist:
        try:
            AES = loader()
            break
        except (ImportError, IGNOBLEError):
            pass
    return AES

AES = _load_crypto()

META_NAMES = ('mimetype', 'META-INF/rights.xml', 'META-INF/encryption.xml')
NSMAP = {'adept': 'http://ns.adobe.com/adept',
         'enc': 'http://www.w3.org/2001/04/xmlenc#'}

class ZipInfo(zipfile.ZipInfo):
    def __init__(self, *args, **kwargs):
        if 'compress_type' in kwargs:
            compress_type = kwargs.pop('compress_type')
        super(ZipInfo, self).__init__(*args, **kwargs)
        self.compress_type = compress_type

class Decryptor(object):
    def __init__(self, bookkey, encryption):
        enc = lambda tag: '{%s}%s' % (NSMAP['enc'], tag)
        self._aes = AES(bookkey)
        encryption = etree.fromstring(encryption)
        self._encrypted = encrypted = set()
        expr = './%s/%s/%s' % (enc('EncryptedData'), enc('CipherData'),
                               enc('CipherReference'))
        for elem in encryption.findall(expr):
            path = elem.get('URI', None)
            if path is not None:
                path = path.encode('utf-8')
                encrypted.add(path)

    def decompress(self, bytes):
        dc = zlib.decompressobj(-15)
        bytes = dc.decompress(bytes)
        ex = dc.decompress('Z') + dc.flush()
        if ex:
            bytes = bytes + ex
        return bytes

    def decrypt(self, path, data):
        if path in self._encrypted:
            data = self._aes.decrypt(data)[16:]
            data = data[:-ord(data[-1])]
            data = self.decompress(data)
        return data

# check file to make check whether it's probably an Adobe Adept encrypted ePub
def ignobleBook(inpath):
    with closing(ZipFile(open(inpath, 'rb'))) as inf:
        namelist = set(inf.namelist())
        if 'META-INF/rights.xml' not in namelist or \
           'META-INF/encryption.xml' not in namelist:
            return False
        try:
            rights = etree.fromstring(inf.read('META-INF/rights.xml'))
            adept = lambda tag: '{%s}%s' % (NSMAP['adept'], tag)
            expr = './/%s' % (adept('encryptedKey'),)
            bookkey = ''.join(rights.findtext(expr))
            if len(bookkey) == 64:
                return True
        except:
            # if we couldn't check, assume it is
            return True
    return False

# return error code and error message duple
def decryptBook(keyb64, inpath, outpath):
    if AES is None:
        # 1 means don't try again
        return (1, u"PyCrypto or OpenSSL must be installed.")
    key = keyb64.decode('base64')[:16]
    aes = AES(key)
    with closing(ZipFile(open(inpath, 'rb'))) as inf:
        namelist = set(inf.namelist())
        if 'META-INF/rights.xml' not in namelist or \
           'META-INF/encryption.xml' not in namelist:
            return (1, u"Not a secure Barnes & Noble ePub.")
        for name in META_NAMES:
            namelist.remove(name)
        try:
            rights = etree.fromstring(inf.read('META-INF/rights.xml'))
            adept = lambda tag: '{%s}%s' % (NSMAP['adept'], tag)
            expr = './/%s' % (adept('encryptedKey'),)
            bookkey = ''.join(rights.findtext(expr))
            if len(bookkey) != 64:
                return (1, u"Not a secure Barnes & Noble ePub.")
            bookkey = aes.decrypt(bookkey.decode('base64'))
            bookkey = bookkey[:-ord(bookkey[-1])]
            encryption = inf.read('META-INF/encryption.xml')
            decryptor = Decryptor(bookkey[-16:], encryption)
            kwds = dict(compression=ZIP_DEFLATED, allowZip64=False)
            with closing(ZipFile(open(outpath, 'wb'), 'w', **kwds)) as outf:
                zi = ZipInfo('mimetype', compress_type=ZIP_STORED)
                outf.writestr(zi, inf.read('mimetype'))
                for path in namelist:
                    data = inf.read(path)
                    outf.writestr(path, decryptor.decrypt(path, data))
        except Exception, e:
            return (2, u"{0}.".format(e.args[0]))
    return (0, u"Success")


def cli_main(argv=unicode_argv()):
    progname = os.path.basename(argv[0])
    if len(argv) != 4:
        print u"usage: {0} <keyfile.der> <inbook.epub> <outbook.epub>".format(progname)
        return 1
    keypath, inpath, outpath = argv[1:]
    userkey = open(keypath,'rb').read()
    result = decryptBook(userkey, inpath, outpath)
    print result[1]
    return result[0]

def gui_main():
    import Tkinter
    import Tkconstants
    import tkFileDialog
    import traceback

    class DecryptionDialog(Tkinter.Frame):
        def __init__(self, root):
            Tkinter.Frame.__init__(self, root, border=5)
            self.status = Tkinter.Label(self, text=u"Select files for decryption")
            self.status.pack(fill=Tkconstants.X, expand=1)
            body = Tkinter.Frame(self)
            body.pack(fill=Tkconstants.X, expand=1)
            sticky = Tkconstants.E + Tkconstants.W
            body.grid_columnconfigure(1, weight=2)
            Tkinter.Label(body, text=u"Key file").grid(row=0)
            self.keypath = Tkinter.Entry(body, width=30)
            self.keypath.grid(row=0, column=1, sticky=sticky)
            if os.path.exists(u"bnepubkey.b64"):
                self.keypath.insert(0, u"bnepubkey.b64")
            button = Tkinter.Button(body, text=u"...", command=self.get_keypath)
            button.grid(row=0, column=2)
            Tkinter.Label(body, text=u"Input file").grid(row=1)
            self.inpath = Tkinter.Entry(body, width=30)
            self.inpath.grid(row=1, column=1, sticky=sticky)
            button = Tkinter.Button(body, text=u"...", command=self.get_inpath)
            button.grid(row=1, column=2)
            Tkinter.Label(body, text=u"Output file").grid(row=2)
            self.outpath = Tkinter.Entry(body, width=30)
            self.outpath.grid(row=2, column=1, sticky=sticky)
            button = Tkinter.Button(body, text=u"...", command=self.get_outpath)
            button.grid(row=2, column=2)
            buttons = Tkinter.Frame(self)
            buttons.pack()
            botton = Tkinter.Button(
                buttons, text=u"Decrypt", width=10, command=self.decrypt)
            botton.pack(side=Tkconstants.LEFT)
            Tkinter.Frame(buttons, width=10).pack(side=Tkconstants.LEFT)
            button = Tkinter.Button(
                buttons, text=u"Quit", width=10, command=self.quit)
            button.pack(side=Tkconstants.RIGHT)

        def get_keypath(self):
            keypath = tkFileDialog.askopenfilename(
                parent=None, title=u"Select Barnes & Noble \'.b64\' key file",
                defaultextension=u".b64",
                filetypes=[('base64-encoded files', '.b64'),
                           ('All Files', '.*')])
            if keypath:
                keypath = os.path.normpath(keypath)
                self.keypath.delete(0, Tkconstants.END)
                self.keypath.insert(0, keypath)
            return

        def get_inpath(self):
            inpath = tkFileDialog.askopenfilename(
                parent=None, title=u"Select B&N-encrypted ePub file to decrypt",
                defaultextension=u".epub", filetypes=[('ePub files', '.epub')])
            if inpath:
                inpath = os.path.normpath(inpath)
                self.inpath.delete(0, Tkconstants.END)
                self.inpath.insert(0, inpath)
            return

        def get_outpath(self):
            outpath = tkFileDialog.asksaveasfilename(
                parent=None, title=u"Select unencrypted ePub file to produce",
                defaultextension=u".epub", filetypes=[('ePub files', '.epub')])
            if outpath:
                outpath = os.path.normpath(outpath)
                self.outpath.delete(0, Tkconstants.END)
                self.outpath.insert(0, outpath)
            return

        def decrypt(self):
            keypath = self.keypath.get()
            inpath = self.inpath.get()
            outpath = self.outpath.get()
            if not keypath or not os.path.exists(keypath):
                self.status['text'] = u"Specified key file does not exist"
                return
            if not inpath or not os.path.exists(inpath):
                self.status['text'] = u"Specified input file does not exist"
                return
            if not outpath:
                self.status['text'] = u"Output file not specified"
                return
            if inpath == outpath:
                self.status['text'] = u"Must have different input and output files"
                return
            userkey = open(keypath,'rb').read()
            self.status['text'] = u"Decrypting..."
            try:
                decrypt_status = decryptBook(userkey, inpath, outpath)
            except Exception, e:
                self.status['text'] = u"Error: {0}".format(e.args[0])
                return
            if decrypt_status[0] == 0:
                self.status['text'] = u"File successfully decrypted"
            else:
                self.status['text'] = decrypt_status[1]

    root = Tkinter.Tk()
    root.title(u"Barnes & Noble ePub Decrypter v.{0}".format(__version__))
    root.resizable(True, False)
    root.minsize(300, 0)
    DecryptionDialog(root).pack(fill=Tkconstants.X, expand=1)
    root.mainloop()
    return 0

if __name__ == '__main__':
    if len(sys.argv) > 1:
        sys.stdout=SafeUnbuffered(sys.stdout)
        sys.stderr=SafeUnbuffered(sys.stderr)
        sys.exit(cli_main())
    sys.exit(gui_main())