from __future__ import with_statement from getpass import getpass import hashlib import os import msgpack import zlib from pbkdf2 import pbkdf2 from Crypto.Cipher import AES from Crypto.Hash import SHA256, HMAC from Crypto.Util import Counter from Crypto.Util.number import bytes_to_long, long_to_bytes from Crypto.Random import get_random_bytes from .helpers import IntegrityError, get_keys_dir class Key(object): FILE_ID = 'DARC KEY' def __init__(self, store=None): if store: self.open(self.find_key_file(store)) def find_key_file(self, store): id = store.meta['id'] keys_dir = get_keys_dir() for name in os.listdir(keys_dir): filename = os.path.join(keys_dir, name) with open(filename, 'rb') as fd: line = fd.readline().strip() if line and line.startswith(self.FILE_ID) and line[9:] == id: return filename raise Exception('Key file for store with ID %s not found' % id) def open(self, filename): with open(filename, 'rb') as fd: lines = fd.readlines() if not lines[0].startswith(self.FILE_ID) != self.FILE_ID: raise ValueError('Not a DARC key file') self.store_id = lines[0][len(self.FILE_ID):].strip().decode('hex') cdata = (''.join(lines[1:])).decode('base64') self.password = '' data = self.decrypt_key_file(cdata, '') while not data: self.password = getpass('Key password: ') if not self.password: raise Exception('Key decryption failed') data = self.decrypt_key_file(cdata, self.password) if not data: print 'Incorrect password' key = msgpack.unpackb(data) if key['version'] != 1: raise IntegrityError('Invalid key file header') self.store_id = key['store_id'] self.enc_key = key['enc_key'] self.enc_hmac_key = key['enc_hmac_key'] self.id_key = key['id_key'] self.chunk_seed = key['chunk_seed'] self.counter = Counter.new(128, initial_value=bytes_to_long(os.urandom(16)), allow_wraparound=True) def encrypt_key_file(self, data, password): salt = get_random_bytes(32) iterations = 2000 key = pbkdf2(password, salt, 32, iterations, hashlib.sha256) hash = HMAC.new(key, data, SHA256).digest() cdata = AES.new(key, AES.MODE_CTR, counter=Counter.new(128)).encrypt(data) d = { 'version': 1, 'salt': salt, 'iterations': iterations, 'algorithm': 'SHA256', 'hash': hash, 'data': cdata, } return msgpack.packb(d) def decrypt_key_file(self, data, password): d = msgpack.unpackb(data) assert d['version'] == 1 assert d['algorithm'] == 'SHA256' key = pbkdf2(password, d['salt'], 32, d['iterations'], hashlib.sha256) data = AES.new(key, AES.MODE_CTR, counter=Counter.new(128)).decrypt(d['data']) if HMAC.new(key, data, SHA256).digest() != d['hash']: return None return data def save(self, path, password): key = { 'version': 1, 'store_id': self.store_id, 'enc_key': self.enc_key, 'enc_hmac_key': self.enc_hmac_key, 'id_key': self.enc_key, 'chunk_seed': self.chunk_seed, } data = self.encrypt_key_file(msgpack.packb(key), password) with open(path, 'wb') as fd: fd.write('%s %s\n' % (self.FILE_ID, self.store_id.encode('hex'))) fd.write(data.encode('base64')) print 'Key file "%s" created' % path def chpass(self): password, password2 = 1, 2 while password != password2: password = getpass('New password: ') password2 = getpass('New password again: ') if password != password2: print 'Passwords do not match' self.save(self.path, password) return 0 @staticmethod def create(store, filename, password=None): i = 1 path = filename while os.path.exists(path): i += 1 path = filename + '.%d' % i if password is not None: password2 = password else: password, password2 = 1, 2 while password != password2: password = getpass('Keychain password: ') password2 = getpass('Keychain password again: ') if password != password2: print 'Passwords do not match' key = Key() key.store_id = store.meta['id'].decode('hex') # Chunk AES256 encryption key key.enc_key = get_random_bytes(32) # Chunk encryption HMAC key key.enc_hmac_key = get_random_bytes(32) # Chunk id HMAC key key.id_key = get_random_bytes(32) # Chunkifier seed key.chunk_seed = bytes_to_long(get_random_bytes(4)) & 0x7fffffff key.save(path, password) return 0 def id_hash(self, data): """Return HMAC hash using the "id" HMAC key """ return HMAC.new(self.id_key, data, SHA256).digest() def encrypt(self, data): data = zlib.compress(data) nonce = long_to_bytes(self.counter.next_value(), 16) data = ''.join((nonce, AES.new(self.enc_key, AES.MODE_CTR, '', counter=self.counter).encrypt(data))) hash = HMAC.new(self.enc_hmac_key, data, SHA256).digest() return ''.join(('\0', hash, data)) def decrypt(self, id, data): if data[0] != '\0': raise IntegrityError('Invalid encryption envelope') hash = data[1:33] if HMAC.new(self.enc_hmac_key, data[33:], SHA256).digest() != hash: raise IntegrityError('Encryption envelope checksum mismatch') nonce = bytes_to_long(data[33:49]) counter = Counter.new(128, initial_value=nonce, allow_wraparound=True) data = zlib.decompress(AES.new(self.enc_key, AES.MODE_CTR, counter=counter).decrypt(data[49:])) if HMAC.new(self.id_key, data, SHA256).digest() != id: raise IntegrityError('Chunk id verification failed') return data