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 PREFIX = '\0' * 8 class Key(object): FILE_ID = 'DARC KEY' def __init__(self, store=None, password=None): if store: self.open(self.find_key_file(store), password=password) def find_key_file(self, store): id = store.id.encode('hex') 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, prompt=None, password=None): prompt = prompt or 'Enter password for %s: ' % 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 = password or '' data = self.decrypt_key_file(cdata, self.password) while not data: self.password = getpass(prompt) 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(64, initial_value=1, prefix=PREFIX) self.path = filename def post_manifest_load(self, config): iv = bytes_to_long(config['aes_counter']) + 100 self.counter = Counter.new(64, initial_value=iv, prefix=PREFIX) def pre_manifest_write(self, manifest): manifest.config['aes_counter'] = long_to_bytes(self.counter.next_value(), 8) def encrypt_key_file(self, data, password): salt = get_random_bytes(32) iterations = 10000 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')) self.path = path def chpasswd(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('Key file password (Leave blank for no password): ') password2 = getpass('Key file password again: ') if password != password2: print 'Passwords do not match' key = Key() key.store_id = store.id # 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)) # Convert to signed int32 if key.chunk_seed & 0x80000000: key.chunk_seed = key.chunk_seed - 0xffffffff - 1 key.save(path, password) return Key(store, password=password) 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(), 8) 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[33:41]) counter = Counter.new(64, initial_value=nonce, prefix=PREFIX) data = zlib.decompress(AES.new(self.enc_key, AES.MODE_CTR, counter=counter).decrypt(data[41:])) if id and HMAC.new(self.id_key, data, SHA256).digest() != id: raise IntegrityError('Chunk id verification failed') return data