diff options
Diffstat (limited to 'src')
| -rw-r--r-- | src/cryptography/hazmat/backends/openssl/backend.py | 37 |
1 files changed, 31 insertions, 6 deletions
diff --git a/src/cryptography/hazmat/backends/openssl/backend.py b/src/cryptography/hazmat/backends/openssl/backend.py index 8cec64d6..2db63a27 100644 --- a/src/cryptography/hazmat/backends/openssl/backend.py +++ b/src/cryptography/hazmat/backends/openssl/backend.py @@ -14,6 +14,7 @@ from contextlib import contextmanager import asn1crypto.core import six +from six.moves import range from cryptography import utils, x509 from cryptography.exceptions import UnsupportedAlgorithm, _Reasons @@ -2095,7 +2096,8 @@ class Backend(object): def x25519_load_private_bytes(self, data): # When we drop support for CRYPTOGRAPHY_OPENSSL_LESS_THAN_111 we can - # switch this to EVP_PKEY_new_raw_private_key + # switch this to EVP_PKEY_new_raw_private_key and drop the + # zeroed_bytearray garbage. # OpenSSL only has facilities for loading PKCS8 formatted private # keys using the algorithm identifiers specified in # https://tools.ietf.org/html/draft-ietf-curdle-pkix-09. @@ -2113,8 +2115,12 @@ class Backend(object): raise ValueError("An X25519 private key is 32 bytes long") pkcs8_prefix = b'0.\x02\x01\x000\x05\x06\x03+en\x04"\x04 ' - bio = self._bytes_to_bio(pkcs8_prefix + data) - evp_pkey = backend._lib.d2i_PrivateKey_bio(bio.bio, self._ffi.NULL) + with self._zeroed_bytearray(48) as ba: + ba[0:16] = pkcs8_prefix + ba[16:] = data + bio = self._bytes_to_bio(ba) + evp_pkey = backend._lib.d2i_PrivateKey_bio(bio.bio, self._ffi.NULL) + self.openssl_assert(evp_pkey != self._ffi.NULL) evp_pkey = self._ffi.gc(evp_pkey, self._lib.EVP_PKEY_free) self.openssl_assert( @@ -2205,6 +2211,26 @@ class Backend(object): ) @contextlib.contextmanager + def _zeroed_bytearray(self, length): + """ + This method creates a bytearray, which we copy data into (hopefully + also from a mutable buffer that can be dynamically erased!), and then + zero when we're done. + """ + ba = bytearray(length) + try: + yield ba + finally: + self._zero_data(ba, length) + + def _zero_data(self, data, length): + # We clear things this way because at the moment we're not + # sure of a better way that can guarantee it overwrites the + # memory of a bytearray and doesn't just replace the underlying char *. + for i in range(length): + data[i] = 0 + + @contextlib.contextmanager def _zeroed_null_terminated_buf(self, data): """ This method takes bytes, which can be a bytestring or a mutable @@ -2224,9 +2250,8 @@ class Backend(object): try: yield buf finally: - # TODO: this could be done with memset to avoid the Python - # bytestring alloc. - self._ffi.memmove(buf, b"\x00" * data_len, data_len) + # Cast to a uint8_t * so we can assign by integer + self._zero_data(self._ffi.cast("uint8_t *", buf), data_len) def load_key_and_certificates_from_pkcs12(self, data, password): if password is not None: |