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https://github.com/tahoe-lafs/tahoe-lafs.git
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212 lines
7.6 KiB
Python
212 lines
7.6 KiB
Python
from pycryptopp.hash.sha256 import SHA256
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import os
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from allmydata.util.netstring import netstring
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try:
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import hashlib
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sha1 = hashlib.sha1
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except ImportError:
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# hashlib was added in Python 2.5
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import sha
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sha1 = sha.new
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# Be very very cautious when modifying this file. Almost any change will
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# cause a compatibility break, invalidating all outstanding URIs and making
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# any previously uploaded files become inaccessible. BE CONSERVATIVE AND TEST
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# AGAINST OLD DATA!
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# Various crypto values are this size: hash outputs (from SHA-256d),
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# randomly-generated secrets such as the lease secret, and symmetric encryption
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# keys. In the near future we will add DSA private keys, and salts of various
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# kinds.
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CRYPTO_VAL_SIZE=32
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class _SHA256d_Hasher:
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# use SHA-256d, as defined by Ferguson and Schneier: hash the output
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# again to prevent length-extension attacks
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def __init__(self, truncate_to=None):
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self.h = SHA256()
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self.truncate_to = truncate_to
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self._digest = None
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def update(self, data):
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assert isinstance(data, str) # no unicode
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self.h.update(data)
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def digest(self):
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if self._digest is None:
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h1 = self.h.digest()
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del self.h
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h2 = SHA256(h1).digest()
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if self.truncate_to:
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h2 = h2[:self.truncate_to]
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self._digest = h2
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return self._digest
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def tagged_hasher(tag, truncate_to=None):
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hasher = _SHA256d_Hasher(truncate_to)
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hasher.update(netstring(tag))
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return hasher
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def tagged_hash(tag, val, truncate_to=None):
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hasher = tagged_hasher(tag, truncate_to)
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hasher.update(val)
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return hasher.digest()
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def tagged_pair_hash(tag, val1, val2, truncate_to=None):
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s = _SHA256d_Hasher(truncate_to)
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s.update(netstring(tag))
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s.update(netstring(val1))
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s.update(netstring(val2))
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return s.digest()
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## specific hash tags that we use
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# immutable
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STORAGE_INDEX_TAG = "allmydata_immutable_key_to_storage_index_v1"
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BLOCK_TAG = "allmydata_encoded_subshare_v1"
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UEB_TAG = "allmydata_uri_extension_v1"
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PLAINTEXT_TAG = "allmydata_plaintext_v1"
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CIPHERTEXT_TAG = "allmydata_crypttext_v1"
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CIPHERTEXT_SEGMENT_TAG = "allmydata_crypttext_segment_v1"
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PLAINTEXT_SEGMENT_TAG = "allmydata_plaintext_segment_v1"
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CONVERGENT_ENCRYPTION_TAG = "allmydata_immutable_content_to_key_with_added_secret_v1+"
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CLIENT_RENEWAL_TAG = "allmydata_client_renewal_secret_v1"
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CLIENT_CANCEL_TAG = "allmydata_client_cancel_secret_v1"
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FILE_RENEWAL_TAG = "allmydata_file_renewal_secret_v1"
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FILE_CANCEL_TAG = "allmydata_file_cancel_secret_v1"
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BUCKET_RENEWAL_TAG = "allmydata_bucket_renewal_secret_v1"
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BUCKET_CANCEL_TAG = "allmydata_bucket_cancel_secret_v1"
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# mutable
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MUTABLE_WRITEKEY_TAG = "allmydata_mutable_privkey_to_writekey_v1"
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MUTABLE_WRITE_ENABLER_MASTER_TAG = "allmydata_mutable_writekey_to_write_enabler_master_v1"
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MUTABLE_WRITE_ENABLER_TAG = "allmydata_mutable_write_enabler_master_and_nodeid_to_write_enabler_v1"
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MUTABLE_PUBKEY_TAG = "allmydata_mutable_pubkey_to_fingerprint_v1"
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MUTABLE_READKEY_TAG = "allmydata_mutable_writekey_to_readkey_v1"
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MUTABLE_DATAKEY_TAG = "allmydata_mutable_readkey_to_datakey_v1"
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MUTABLE_STORAGEINDEX_TAG = "allmydata_mutable_readkey_to_storage_index_v1"
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# dirnodes
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DIRNODE_CHILD_WRITECAP_TAG = "allmydata_mutable_writekey_and_salt_to_dirnode_child_capkey_v1"
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DIRNODE_CHILD_SALT_TAG = "allmydata_dirnode_child_rwcap_to_salt_v1"
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def storage_index_hash(key):
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# storage index is truncated to 128 bits (16 bytes). We're only hashing a
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# 16-byte value to get it, so there's no point in using a larger value. We
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# use this same tagged hash to go from encryption key to storage index for
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# random-keyed immutable files and convergent-encryption immutabie
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# files. Mutable files use ssk_storage_index_hash().
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return tagged_hash(STORAGE_INDEX_TAG, key, 16)
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def block_hash(data):
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return tagged_hash(BLOCK_TAG, data)
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def block_hasher():
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return tagged_hasher(BLOCK_TAG)
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def uri_extension_hash(data):
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return tagged_hash(UEB_TAG, data)
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def uri_extension_hasher():
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return tagged_hasher(UEB_TAG)
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def plaintext_hash(data):
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return tagged_hash(PLAINTEXT_TAG, data)
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def plaintext_hasher():
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return tagged_hasher(PLAINTEXT_TAG)
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def crypttext_hash(data):
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return tagged_hash(CIPHERTEXT_TAG, data)
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def crypttext_hasher():
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return tagged_hasher(CIPHERTEXT_TAG)
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def crypttext_segment_hash(data):
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return tagged_hash(CIPHERTEXT_SEGMENT_TAG, data)
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def crypttext_segment_hasher():
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return tagged_hasher(CIPHERTEXT_SEGMENT_TAG)
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def plaintext_segment_hash(data):
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return tagged_hash(PLAINTEXT_SEGMENT_TAG, data)
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def plaintext_segment_hasher():
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return tagged_hasher(PLAINTEXT_SEGMENT_TAG)
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KEYLEN = 16
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IVLEN = 16
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def convergence_hash(k, n, segsize, data, convergence):
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h = convergence_hasher(k, n, segsize, convergence)
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h.update(data)
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return h.digest()
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def convergence_hasher(k, n, segsize, convergence):
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assert isinstance(convergence, str)
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param_tag = netstring("%d,%d,%d" % (k, n, segsize))
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tag = CONVERGENT_ENCRYPTION_TAG + netstring(convergence) + param_tag
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return tagged_hasher(tag, KEYLEN)
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def random_key():
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return os.urandom(KEYLEN)
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def my_renewal_secret_hash(my_secret):
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return tagged_hash(my_secret, CLIENT_RENEWAL_TAG)
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def my_cancel_secret_hash(my_secret):
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return tagged_hash(my_secret, CLIENT_CANCEL_TAG)
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def file_renewal_secret_hash(client_renewal_secret, storage_index):
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return tagged_pair_hash(FILE_RENEWAL_TAG,
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client_renewal_secret, storage_index)
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def file_cancel_secret_hash(client_cancel_secret, storage_index):
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return tagged_pair_hash(FILE_CANCEL_TAG,
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client_cancel_secret, storage_index)
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def bucket_renewal_secret_hash(file_renewal_secret, peerid):
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assert len(peerid) == 20, "%s: %r" % (len(peerid), peerid) # binary!
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return tagged_pair_hash(BUCKET_RENEWAL_TAG, file_renewal_secret, peerid)
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def bucket_cancel_secret_hash(file_cancel_secret, peerid):
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assert len(peerid) == 20, "%s: %r" % (len(peerid), peerid) # binary!
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return tagged_pair_hash(BUCKET_CANCEL_TAG, file_cancel_secret, peerid)
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def _xor(a, b):
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return "".join([chr(ord(c) ^ ord(b)) for c in a])
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def hmac(tag, data):
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ikey = _xor(tag, "\x36")
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okey = _xor(tag, "\x5c")
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h1 = SHA256(ikey + data).digest()
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h2 = SHA256(okey + h1).digest()
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return h2
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def mutable_rwcap_key_hash(iv, writekey):
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return tagged_pair_hash(DIRNODE_CHILD_WRITECAP_TAG, iv, writekey, KEYLEN)
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def mutable_rwcap_salt_hash(writekey):
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return tagged_hash(DIRNODE_CHILD_SALT_TAG, writekey, IVLEN)
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def ssk_writekey_hash(privkey):
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return tagged_hash(MUTABLE_WRITEKEY_TAG, privkey, KEYLEN)
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def ssk_write_enabler_master_hash(writekey):
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return tagged_hash(MUTABLE_WRITE_ENABLER_MASTER_TAG, writekey)
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def ssk_write_enabler_hash(writekey, peerid):
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assert len(peerid) == 20, "%s: %r" % (len(peerid), peerid) # binary!
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wem = ssk_write_enabler_master_hash(writekey)
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return tagged_pair_hash(MUTABLE_WRITE_ENABLER_TAG, wem, peerid)
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def ssk_pubkey_fingerprint_hash(pubkey):
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return tagged_hash(MUTABLE_PUBKEY_TAG, pubkey)
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def ssk_readkey_hash(writekey):
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return tagged_hash(MUTABLE_READKEY_TAG, writekey, KEYLEN)
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def ssk_readkey_data_hash(IV, readkey):
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return tagged_pair_hash(MUTABLE_DATAKEY_TAG, IV, readkey, KEYLEN)
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def ssk_storage_index_hash(readkey):
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return tagged_hash(MUTABLE_STORAGEINDEX_TAG, readkey, KEYLEN)
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def constant_time_compare(a, b):
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n = os.urandom(8)
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return bool(tagged_hash(n, a) == tagged_hash(n, b))
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BACKUPDB_DIRHASH_TAG = "allmydata_backupdb_dirhash_v1"
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def backupdb_dirhash(contents):
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return tagged_hash(BACKUPDB_DIRHASH_TAG, contents)
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