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directories: make the IV for the writecaps in directory entries be computed from the secure hash of the writecap itself

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This makes encoding of directory entries deterministic, and it is also a tad faster on Macbook Pro than getting a random IV with os.urandom(16).
This commit is contained in:
Zooko O'Whielacronx 2009-07-04 19:48:15 -07:00
parent fcedca966e
commit 786ed012b3
2 changed files with 5 additions and 1 deletions
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2
src/allmydata/dirnode.py
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@ -195,7 +195,7 @@ class NewDirectoryNode:
def _encrypt_rwcap(self, rwcap):
assert isinstance(rwcap, str)
IV = os.urandom(16)
IV = hashutil.mutable_rwcap_iv_hash(self._node.get_writekey())
key = hashutil.mutable_rwcap_key_hash(IV, self._node.get_writekey())
cryptor = AES(key)
crypttext = cryptor.process(rwcap)

4
src/allmydata/util/hashutil.py
View File

@ -82,6 +82,7 @@ MUTABLE_STORAGEINDEX_TAG = "allmydata_mutable_readkey_to_storage_index_v1"
# dirnodes
DIRNODE_CHILD_WRITECAP_TAG = "allmydata_mutable_writekey_and_salt_to_dirnode_child_capkey_v1"
DIRNODE_CHILD_IV_TAG = "allmydata_mutable_writekey_to_iv_v1"
def storage_index_hash(key):
# storage index is truncated to 128 bits (16 bytes). We're only hashing a
@ -122,6 +123,7 @@ def plaintext_segment_hasher():
return tagged_hasher(PLAINTEXT_SEGMENT_TAG)
KEYLEN = 16
IVLEN = 16
def convergence_hash(k, n, segsize, data, convergence):
h = convergence_hasher(k, n, segsize, convergence)
@ -170,6 +172,8 @@ def hmac(tag, data):
def mutable_rwcap_key_hash(iv, writekey):
return tagged_pair_hash(DIRNODE_CHILD_WRITECAP_TAG, iv, writekey, KEYLEN)
def mutable_rwcap_iv_hash(writekey):
return tagged_hash(DIRNODE_CHILD_IV_TAG, writekey, IVLEN)
def ssk_writekey_hash(privkey):
return tagged_hash(MUTABLE_WRITEKEY_TAG, privkey, KEYLEN)