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Code Issues Releases Wiki Activity

Verify hash before decompressing with PlaintextKey

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This commit is contained in:
Jonas Borgström 2013-07-05 16:57:36 +02:00
parent 0c1d6e8179
commit a887fa2065
1 changed files with 25 additions and 19 deletions
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44
darc/key.py
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@ -12,10 +12,6 @@
PREFIX = b'\0' * 8
KEYFILE = b'\0'
PASSPHRASE = b'\1'
PLAINTEXT = b'\2'
class HMAC(hmac.HMAC):
@ -33,11 +29,11 @@ def key_creator(repository, args):
def key_factory(repository, manifest_data):
if manifest_data[:1] == KEYFILE:
if manifest_data[0] == KeyfileKey.TYPE:
return KeyfileKey.detect(repository, manifest_data)
elif manifest_data[:1] == PASSPHRASE:
elif manifest_data[0] == PassphraseKey.TYPE:
return PassphraseKey.detect(repository, manifest_data)
elif manifest_data[:1] == PLAINTEXT:
elif manifest_data[0] == PlaintextKey.TYPE:
return PlaintextKey.detect(repository, manifest_data)
else:
raise Exception('Unkown Key type %d' % ord(manifest_data[0]))
@ -45,6 +41,9 @@ def key_factory(repository, manifest_data):
class KeyBase(object):
def __init__(self):
self.TYPE_STR = bytes([self.TYPE])
def id_hash(self, data):
"""Return HMAC hash using the "id" HMAC key
"""
@ -57,7 +56,7 @@ def decrypt(self, id, data):
class PlaintextKey(KeyBase):
TYPE = PLAINTEXT
TYPE = 0x02
chunk_seed = 0
@ -74,12 +73,19 @@ def id_hash(self, data):
return sha256(data).digest()
def encrypt(self, data):
return b''.join([self.TYPE, zlib.compress(data)])
cdata = zlib.compress(data)
hash = sha256(cdata).digest()
return b''.join([self.TYPE_STR, hash, cdata])
def decrypt(self, id, data):
if data[:1] != self.TYPE:
if data[0] != self.TYPE:
raise IntegrityError('Invalid encryption envelope')
data = zlib.decompress(memoryview(data)[1:])
# This is just a hash and not a hmac but it will at least
# stop unintentionally corrupted data from hitting zlib.decompress()
hash = memoryview(data)[1:33]
if memoryview(sha256(memoryview(data)[33:]).digest()) != hash:
raise IntegrityError('Payload checksum mismatch')
data = zlib.decompress(memoryview(data)[33:])
if id and sha256(data).digest() != id:
raise IntegrityError('Chunk id verification failed')
return data
@ -96,14 +102,14 @@ def encrypt(self, data):
data = zlib.compress(data)
self.enc_cipher.reset()
data = b''.join((self.enc_cipher.iv[8:], self.enc_cipher.encrypt(data)))
hash = HMAC(self.enc_hmac_key, data, sha256).digest()
return b''.join((self.TYPE, hash, data))
hmac = HMAC(self.enc_hmac_key, data, sha256).digest()
return b''.join((self.TYPE_STR, hmac, data))
def decrypt(self, id, data):
if data[:1] != self.TYPE:
if data[0] != self.TYPE:
raise IntegrityError('Invalid encryption envelope')
hash = memoryview(data)[1:33]
if memoryview(HMAC(self.enc_hmac_key, memoryview(data)[33:], sha256).digest()) != hash:
hmac = memoryview(data)[1:33]
if memoryview(HMAC(self.enc_hmac_key, memoryview(data)[33:], sha256).digest()) != hmac:
raise IntegrityError('Encryption envelope checksum mismatch')
self.dec_cipher.reset(iv=PREFIX + data[33:41])
data = zlib.decompress(self.dec_cipher.decrypt(data[41:])) # should use memoryview
@ -112,7 +118,7 @@ def decrypt(self, id, data):
return data
def extract_iv(self, payload):
if payload[:1] != self.TYPE:
if payload[0] != self.TYPE:
raise IntegrityError('Invalid encryption envelope')
nonce = bytes_to_long(payload[33:41])
return nonce
@ -132,7 +138,7 @@ def init_ciphers(self, enc_iv=b''):
class PassphraseKey(AESKeyBase):
TYPE = PASSPHRASE
TYPE = 0x01
iterations = 100000
@classmethod
@ -179,7 +185,7 @@ def init(self, repository, passphrase):
class KeyfileKey(AESKeyBase):
FILE_ID = 'DARC KEY'
TYPE = KEYFILE
TYPE = 0x00
@classmethod
def detect(cls, repository, manifest_data):