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.PublicKey import RSA from Crypto.Util import Counter from Crypto.Util.number import bytes_to_long, long_to_bytes from . import PACKET_ENCRYPT_READ, PACKET_ENCRYPT_CREATE from .helpers import IntegrityError, zero_pad from .oaep import OAEP class Keychain(object): FILE_ID = 'DARC KEYCHAIN' CREATE = '\1' READ = '\2' def __init__(self, path=None): self._key_cache = {} self.read_key = os.urandom(32) self.create_key = os.urandom(32) self.counter = Counter.new(64, prefix='\0' * 8) self.aes_id = self.rsa_read = self.rsa_create = None self.path = path if path: self.open(path) def get_chunkify_seed(self): return bytes_to_long(self.aes_id[:4]) & 0x7fffffff def open(self, path): print 'Opening keychain "%s"' % path with open(path, 'rb') as fd: if fd.read(len(self.FILE_ID)) != self.FILE_ID: raise ValueError('Not a keychain') cdata = fd.read() self.password = '' data = self.decrypt_keychain(cdata, '') while not data: self.password = getpass('Keychain password: ') if not self.password: raise Exception('Keychain decryption failed') data = self.decrypt_keychain(cdata, self.password) if not data: print 'Incorrect password' chain = msgpack.unpackb(data) assert chain['version'] == 1 self.aes_id = chain['aes_id'] self.rsa_read = RSA.importKey(chain['rsa_read']) self.rsa_create = RSA.importKey(chain['rsa_create']) self.read_encrypted = OAEP(256, hash=SHA256).encode(self.read_key, os.urandom(32)) self.read_encrypted = zero_pad(self.rsa_read.encrypt(self.read_encrypted, '')[0], 256) self.create_encrypted = OAEP(256, hash=SHA256).encode(self.create_key, os.urandom(32)) self.create_encrypted = zero_pad(self.rsa_create.encrypt(self.create_encrypted, '')[0], 256) def encrypt_keychain(self, data, password): salt = os.urandom(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_keychain(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): chain = { 'version': 1, 'aes_id': self.aes_id, 'rsa_read': self.rsa_read.exportKey('PEM'), 'rsa_create': self.rsa_create.exportKey('PEM'), } data = self.encrypt_keychain(msgpack.packb(chain), password) with open(path, 'wb') as fd: fd.write(self.FILE_ID) fd.write(data) print 'Key chain "%s" saved' % path def restrict(self, path): if os.path.exists(path): print '%s already exists' % path return 1 self.rsa_read = self.rsa_read.publickey() self.save(path, self.password) return 0 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 generate(path): if os.path.exists(path): print '%s already exists' % path return 1 password, password2 = 1, 2 while password != password2: password = getpass('Keychain password: ') password2 = getpass('Keychain password again: ') if password != password2: print 'Passwords do not match' chain = Keychain() print 'Generating keychain' chain.aes_id = os.urandom(32) chain.rsa_read = RSA.generate(2048) chain.rsa_create = RSA.generate(2048) chain.save(path, password) return 0 def id_hash(self, data): """Return HMAC hash using the "id" AES key """ return HMAC.new(self.aes_id, data, SHA256).digest() def encrypt(self, magic, data): """Helper function used by `encrypt_read` and `encrypt_create` """ data = zlib.compress(data) nonce = long_to_bytes(self.counter.next_value(), 8) if magic & PACKET_ENCRYPT_READ: data = ''.join((nonce, self.read_encrypted, AES.new(self.read_key, AES.MODE_CTR, '', counter=self.counter).encrypt(data))) elif magic & PACKET_ENCRYPT_CREATE: data = ''.join((nonce, self.create_encrypted, AES.new(self.create_key, AES.MODE_CTR, '', counter=self.counter).encrypt(data))) hash = self.id_hash(data) return ''.join((chr(magic), hash, data)), hash def _decrypt_key(self, data, rsa_key): """Helper function used by `decrypt` """ try: return self._key_cache[data] except KeyError: self._key_cache[data] = OAEP(256, hash=SHA256).decode(rsa_key.decrypt(data)) return self._key_cache[data] def decrypt(self, data): """Decrypt `data` previously encrypted by `encrypt_create` or `encrypt_read` """ magic = ord(data[0]) hash = data[1:33] if self.id_hash(data[33:]) != hash: raise IntegrityError('Encryption integrity error') nonce = bytes_to_long(data[33:41]) counter = Counter.new(64, prefix='\0' * 8, initial_value=nonce) if magic & PACKET_ENCRYPT_READ: key = self._decrypt_key(data[41:297], self.rsa_read) elif magic & PACKET_ENCRYPT_CREATE: key = self._decrypt_key(data[41:297], self.rsa_create) else: raise Exception('Unknown pack magic %d found' % magic) data = AES.new(key, AES.MODE_CTR, counter=counter).decrypt(data[297:]) return magic, zlib.decompress(data), hash