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authordrebs <drebs@leap.se>2013-05-17 09:53:37 -0300
committerdrebs <drebs@leap.se>2013-05-17 13:32:10 -0300
commit1a2a3c6d72e173425885caa2342138c4615a69a3 (patch)
tree6f3c8e7ce8b28f6f23097c7e8eab8f19c659dd98 /src/leap/soledad/backends/leap_backend.py
parent3d5d817510c556d1f79fb58996997ef4ea629f83 (diff)
Use leap.common.crypto and AES-256 CTR for symmetric encryption.
Diffstat (limited to 'src/leap/soledad/backends/leap_backend.py')
-rw-r--r--src/leap/soledad/backends/leap_backend.py65
1 files changed, 42 insertions, 23 deletions
diff --git a/src/leap/soledad/backends/leap_backend.py b/src/leap/soledad/backends/leap_backend.py
index 87f63432..8fa662e9 100644
--- a/src/leap/soledad/backends/leap_backend.py
+++ b/src/leap/soledad/backends/leap_backend.py
@@ -27,6 +27,7 @@ except ImportError:
import json # noqa
import hashlib
import hmac
+import binascii
from u1db import Document
@@ -35,6 +36,11 @@ from u1db.errors import BrokenSyncStream
from u1db.remote.http_target import HTTPSyncTarget
+from leap.common.crypto import (
+ EncryptionMethods,
+ encrypt_sym,
+ decrypt_sym,
+)
from leap.common.keymanager import KeyManager
from leap.common.check import leap_assert
from leap.soledad.auth import TokenBasedAuth
@@ -100,6 +106,8 @@ class MacMethods(object):
ENC_JSON_KEY = '_enc_json'
ENC_SCHEME_KEY = '_enc_scheme'
+ENC_METHOD_KEY = '_enc_method'
+ENC_IV_KEY = '_enc_iv'
MAC_KEY = '_mac'
MAC_METHOD_KEY = '_mac_method'
@@ -132,7 +140,7 @@ def mac_doc(crypto, doc_id, doc_rev, ciphertext, mac_method):
return hmac.new(
crypto.doc_mac_key(doc_id),
str(doc_id) + str(doc_rev) + ciphertext,
- hashlib.sha256).hexdigest()
+ hashlib.sha256).digest()
# raise if we do not know how to handle this MAC method
raise UnknownMacMethod('Unknown MAC method: %s.' % mac_method)
@@ -141,11 +149,14 @@ def encrypt_doc(crypto, doc):
"""
Encrypt C{doc}'s content.
- Return a valid JSON string representing the following:
+ Encrypt doc's contents using AES-256 CTR mode and return a valid JSON
+ string representing the following:
{
ENC_JSON_KEY: '<encrypted doc JSON string>',
ENC_SCHEME_KEY: 'symkey',
+ ENC_METHOD_KEY: EncryptionMethods.AES_256_CTR,
+ ENC_IV_KEY: '<the initial value used to encrypt>',
MAC_KEY: '<mac>'
MAC_METHOD_KEY: 'hmac'
}
@@ -160,19 +171,24 @@ def encrypt_doc(crypto, doc):
@rtype: str
"""
leap_assert(doc.is_tombstone() is False)
- # encrypt content
- ciphertext = crypto.encrypt_sym(
+ # encrypt content using AES-256 CTR mode
+ iv, ciphertext = encrypt_sym(
doc.get_json(),
- crypto.doc_passphrase(doc.doc_id))
- # verify it is indeed encrypted
- if not crypto.is_encrypted_sym(ciphertext):
- raise DocumentNotEncrypted('Failed encrypting document.')
- # update doc's content with encrypted version
+ crypto.doc_passphrase(doc.doc_id),
+ method=EncryptionMethods.AES_256_CTR)
+ # Return a representation for the encrypted content. In the following, we
+ # convert binary data to hexadecimal representation so the JSON
+ # serialization does not complain about what it tries to serialize.
+ hex_ciphertext = binascii.b2a_hex(ciphertext)
return json.dumps({
- ENC_JSON_KEY: ciphertext,
+ ENC_JSON_KEY: hex_ciphertext,
ENC_SCHEME_KEY: EncryptionSchemes.SYMKEY,
- MAC_KEY: mac_doc(
- crypto, doc.doc_id, doc.rev, ciphertext, MacMethods.HMAC),
+ ENC_METHOD_KEY: EncryptionMethods.AES_256_CTR,
+ ENC_IV_KEY: iv,
+ MAC_KEY: binascii.b2a_hex(mac_doc( # store the mac as hex.
+ crypto, doc.doc_id, doc.rev,
+ ciphertext,
+ MacMethods.HMAC)),
MAC_METHOD_KEY: MacMethods.HMAC,
})
@@ -188,13 +204,16 @@ def decrypt_doc(crypto, doc):
{
ENC_JSON_KEY: '<enc_blob>',
ENC_SCHEME_KEY: '<enc_scheme>',
+ ENC_METHOD_KEY: '<enc_method>',
+ ENC_IV_KEY: '<initial value used to encrypt>', # (optional)
MAC_KEY: '<mac>'
MAC_METHOD_KEY: 'hmac'
}
C{enc_blob} is the encryption of the JSON serialization of the document's
content. For now Soledad just deals with documents whose C{enc_scheme} is
- EncryptionSchemes.SYMKEY.
+ EncryptionSchemes.SYMKEY and C{enc_method} is
+ EncryptionMethods.AES_256_CTR.
@param crypto: A SoledadCryto instance to perform the encryption.
@type crypto: leap.soledad.crypto.SoledadCrypto
@@ -207,28 +226,28 @@ def decrypt_doc(crypto, doc):
leap_assert(doc.is_tombstone() is False)
leap_assert(ENC_JSON_KEY in doc.content)
leap_assert(ENC_SCHEME_KEY in doc.content)
+ leap_assert(ENC_METHOD_KEY in doc.content)
leap_assert(MAC_KEY in doc.content)
leap_assert(MAC_METHOD_KEY in doc.content)
# verify MAC
+ ciphertext = binascii.a2b_hex( # content is stored as hex.
+ doc.content[ENC_JSON_KEY])
mac = mac_doc(
crypto, doc.doc_id, doc.rev,
- doc.content[ENC_JSON_KEY],
+ ciphertext,
doc.content[MAC_METHOD_KEY])
- if doc.content[MAC_KEY] != mac:
+ if binascii.a2b_hex(doc.content[MAC_KEY]) != mac: # mac is stored as hex.
raise WrongMac('Could not authenticate document\'s contents.')
# decrypt doc's content
- ciphertext = doc.content[ENC_JSON_KEY]
enc_scheme = doc.content[ENC_SCHEME_KEY]
plainjson = None
if enc_scheme == EncryptionSchemes.SYMKEY:
- if not crypto.is_encrypted_sym(ciphertext):
- raise DocumentNotEncrypted(
- 'Unable to identify document encryption for incoming '
- 'document, although it is marked as being encrypted with a '
- 'symmetric key.')
- plainjson = crypto.decrypt_sym(
+ leap_assert(ENC_IV_KEY in doc.content)
+ plainjson = decrypt_sym(
ciphertext,
- crypto.doc_passphrase(doc.doc_id))
+ crypto.doc_passphrase(doc.doc_id),
+ method=doc.content[ENC_METHOD_KEY],
+ iv=doc.content[ENC_IV_KEY])
else:
raise UnknownEncryptionScheme(enc_scheme)
return plainjson