Decrypt AES encrypted file, function causing failure

it's not clear if you only want a C ++ solution; if you are ok with a Python solution try the PyCrypto module. Here is what I use to zip the current directory, except for some ignoring templates and .zip's encryption. / bin (most of the code is copied from other sources on SO):

import sys
import os
import zipfile
import getpass
from contextlib import contextmanager
from hashlib import md5
from Crypto.Cipher import AES
from Crypto import Random

def derive_key_and_iv(password, salt, key_length, iv_length):
    d = d_i = ''
    while len(d) < key_length + iv_length:
        d_i = md5(d_i + password + salt).digest()
        d += d_i
    return d[:key_length], d[key_length:key_length+iv_length]

def encrypt(in_file, out_file, password, key_length=32):
    bs = AES.block_size
    salt = Random.new().read(bs - len('Salted__'))
    key, iv = derive_key_and_iv(password, salt, key_length, bs)
    cipher = AES.new(key, AES.MODE_CBC, iv)
    out_file.write('Salted__' + salt)
    finished = False
    while not finished:
        chunk = in_file.read(1024 * bs)
        if len(chunk) == 0 or len(chunk) % bs != 0:
            padding_length = (bs - len(chunk) % bs) or bs
            chunk += padding_length * chr(padding_length)
            finished = True
        out_file.write(cipher.encrypt(chunk))

def decrypt(in_file, out_file, password, key_length=32):
    bs = AES.block_size
    salt = in_file.read(bs)[len('Salted__'):]
    key, iv = derive_key_and_iv(password, salt, key_length, bs)
    cipher = AES.new(key, AES.MODE_CBC, iv)
    next_chunk = ''
    finished = False
    while not finished:
        chunk, next_chunk = next_chunk, cipher.decrypt(in_file.read(1024 * bs))
        if len(next_chunk) == 0:
            padding_length = ord(chunk[-1])
            chunk = chunk[:-padding_length]
            finished = True
        out_file.write(chunk)

def query_yes_no(question, default="yes", quiet=False):
    """Ask a yes/no question via raw_input() and return their answer.

    "question" is a string that is presented to the user.
    "default" is the presumed answer if the user just hits <Enter>.
        It must be "yes" (the default), "no" or None (meaning
        an answer is required of the user).

    The "answer" return value is True for "yes" or False for "no".
    """
    valid = {"yes": True, "y": True, "ye": True,
             "no": False, "n": False}
    if default is None:
        prompt = " [y/n] "
    elif default == "yes":
        prompt = " [Y/n] "
    elif default == "no":
        prompt = " [y/N] "
    else:
        raise ValueError("invalid default answer: '%s'" % default)
    while True:
        if not quiet:
          sys.stdout.write(question + prompt)
        if quiet and default is not None:
          choice=default
        else:
          choice = raw_input().lower()
        if default is not None and choice == '':
            return valid[default]
        elif choice in valid:
            return valid[choice]
        else:
            sys.stdout.write("Please respond with 'yes' or 'no' "
                             "(or 'y' or 'n')\n")

dircurr=os.path.abspath('.').replace('\\','/')
dirwithenc=dircurr+'/bin'
if os.path.isfile(dirwithenc+'/bak.enc'):
  if query_yes_no("\nDo you want to decrypt '"+dirwithenc+"/bak.enc'?",'no'):
    password=getpass.getpass('\nDecryption password: ')
    with open(dirwithenc+'/bak.enc', 'rb') as in_file, open(dircurr+'/bak.zip', 'wb') as out_file:
      decrypt(in_file,out_file,password)
    print("\nFile '"+dircurr+"/bak.enc' decrypted to '"+dircurr+"/bak.zip'")
    raw_input("""
***DONE***

Press Enter...""")
    exit(0)
  else:
    print("\nAnswered 'no'")
print("\nEncrypting files will overwrite any preexisting file '"+dirwithenc+"/bak.enc'")
password=getpass.getpass('\nSet an encryption password (will not be saved): ')
print('\nZipping files, excepting certain ignore patterns...')
zf = zipfile.ZipFile(dircurr+'/bak.zip', 'w')
for dirname, subdirs, files in os.walk(os.path.abspath('.')):
  #Do not archive system files beginning with period
  for filename in files:
    if filename[:1]=='.':
      files.remove(filename)
  #Do not archive the binaries directory, it should just be delivered as is
  if 'bin' in subdirs:
    subdirs.remove('bin')
  #Do not archive any previous archives, or you will just make a giant snowball
  if 'bak.zip' in files:
    files.remove('bak.zip')
  if 'bak.enc' in files:
    files.remove('bak.enc')
  zf.write(dirname)
  for filename in files:
    zf.write(os.path.join(dirname, filename))
#If there was a folder 'dat' under the binaries folder, then archive it too,
#so that you have everything you need to rebuild the project
print("Including files under 'bin/dat'")
if os.path.isdir(dircurr+'/bin/dat'):
  for dirname, subdirs, files in os.walk(dircurr+'/bin/dat'):
    if 'bin' in subdirs:
      subdirs.remove('bin')
    zf.write(dirname)
    for filename in files:
      zf.write(os.path.join(dirname, filename))
#If there were any files '*.ico' under the binaries folder, then archive them too,
#so that you have everything you need to rebuild the project
print("Including .ico files under 'bin'")
for dirname, subdirs, files in os.walk(dircurr+'/bin'):
  for filename in files:
    if filename[-4:]=='.ico':
      zf.write(os.path.join(dirname, filename))
zf.close()
print("\nZipped to '"+dircurr+"/bak.zip'")
print("\nEncrypting zipped file and removing unencrypted zipped file...")
with open(dircurr+'/bak.zip', 'rb') as in_file, open(dirwithenc+'/bak.enc', 'wb') as out_file:
  encrypt(in_file, out_file, password)
os.remove(dircurr+'/bak.zip')
print("\nEncrypted to '"+dirwithenc+"/bak.enc'")
raw_input("""
***DONE***

Press Enter...""")
exit(0)