diff options
| -rw-r--r-- | docs/hazmat/primitives/asymmetric/serialization.rst | 17 | ||||
| -rw-r--r-- | src/cryptography/hazmat/primitives/serialization.py | 93 | ||||
| -rw-r--r-- | tests/hazmat/primitives/test_serialization.py | 29 |
3 files changed, 103 insertions, 36 deletions
diff --git a/docs/hazmat/primitives/asymmetric/serialization.rst b/docs/hazmat/primitives/asymmetric/serialization.rst index c184cdf2..1456b0dc 100644 --- a/docs/hazmat/primitives/asymmetric/serialization.rst +++ b/docs/hazmat/primitives/asymmetric/serialization.rst @@ -119,9 +119,6 @@ OpenSSH Public Key The format used by OpenSSH to store public keys, as specified in :rfc:`4253`. -Currently, only RSA and DSA public keys are supported. Any other type of key -will result in an exception being thrown. - An example RSA key in OpenSSH format (line breaks added for formatting purposes):: @@ -134,7 +131,8 @@ purposes):: 2MzHvnbv testkey@localhost DSA keys look almost identical but begin with ``ssh-dss`` rather than -``ssh-rsa``. +``ssh-rsa``. ECDSA keys have a slightly different format, they begin with +``ecdsa-sha2-{curve}``. .. function:: load_ssh_public_key(data, backend) @@ -143,12 +141,17 @@ DSA keys look almost identical but begin with ``ssh-dss`` rather than Deserialize a public key from OpenSSH (:rfc:`4253`) encoded data to an instance of the public key type for the specified backend. + .. note:: + + Currently Ed25519 keys are not supported. + :param bytes data: The OpenSSH encoded key data. :param backend: A backend providing - :class:`~cryptography.hazmat.backends.interfaces.RSABackend` or - :class:`~cryptography.hazmat.backends.interfaces.DSABackend` depending - on key type. + :class:`~cryptography.hazmat.backends.interfaces.RSABackend`, + :class:`~cryptography.hazmat.backends.interfaces.DSABackend`, or + :class:`~cryptography.hazmat.backends.interfaces.EllipticCurveBackend` + depending on the key's type. :returns: A new instance of a public key type. diff --git a/src/cryptography/hazmat/primitives/serialization.py b/src/cryptography/hazmat/primitives/serialization.py index 083f17e5..b95ac1cd 100644 --- a/src/cryptography/hazmat/primitives/serialization.py +++ b/src/cryptography/hazmat/primitives/serialization.py @@ -7,11 +7,10 @@ from __future__ import absolute_import, division, print_function import base64 import struct +import six + from cryptography.exceptions import UnsupportedAlgorithm -from cryptography.hazmat.primitives.asymmetric.dsa import ( - DSAParameterNumbers, DSAPublicNumbers -) -from cryptography.hazmat.primitives.asymmetric.rsa import RSAPublicNumbers +from cryptography.hazmat.primitives.asymmetric import dsa, ec, rsa def load_pem_private_key(data, password, backend): @@ -30,6 +29,18 @@ def load_ssh_public_key(data, backend): 'Key is not in the proper format or contains extra data.') key_type = key_parts[0] + + if key_type == b'ssh-rsa': + loader = _load_ssh_rsa_public_key + elif key_type == b'ssh-dss': + loader = _load_ssh_dss_public_key + elif key_type in [ + b'ecdsa-sha2-nistp256', b'ecdsa-sha2-nistp384', b'ecdsa-sha2-nistp521', + ]: + loader = _load_ssh_ecdsa_public_key + else: + raise UnsupportedAlgorithm('Key type is not supported.') + key_body = key_parts[1] try: @@ -37,53 +48,79 @@ def load_ssh_public_key(data, backend): except TypeError: raise ValueError('Key is not in the proper format.') - if key_type == b'ssh-rsa': - return _load_ssh_rsa_public_key(decoded_data, backend) - elif key_type == b'ssh-dss': - return _load_ssh_dss_public_key(decoded_data, backend) - else: - raise UnsupportedAlgorithm( - 'Only RSA and DSA keys are currently supported.' + inner_key_type, rest = _read_next_string(decoded_data) + + if inner_key_type != key_type: + raise ValueError( + 'Key header and key body contain different key type values.' ) + return loader(key_type, rest, backend) -def _load_ssh_rsa_public_key(decoded_data, backend): - key_type, rest = _read_next_string(decoded_data) - e, rest = _read_next_mpint(rest) - n, rest = _read_next_mpint(rest) - if key_type != b'ssh-rsa': - raise ValueError( - 'Key header and key body contain different key type values.') +def _load_ssh_rsa_public_key(key_type, decoded_data, backend): + e, rest = _read_next_mpint(decoded_data) + n, rest = _read_next_mpint(rest) if rest: raise ValueError('Key body contains extra bytes.') - return RSAPublicNumbers(e, n).public_key(backend) + return rsa.RSAPublicNumbers(e, n).public_key(backend) -def _load_ssh_dss_public_key(decoded_data, backend): - key_type, rest = _read_next_string(decoded_data) - p, rest = _read_next_mpint(rest) +def _load_ssh_dss_public_key(key_type, decoded_data, backend): + p, rest = _read_next_mpint(decoded_data) q, rest = _read_next_mpint(rest) g, rest = _read_next_mpint(rest) y, rest = _read_next_mpint(rest) - if key_type != b'ssh-dss': + if rest: + raise ValueError('Key body contains extra bytes.') + + parameter_numbers = dsa.DSAParameterNumbers(p, q, g) + public_numbers = dsa.DSAPublicNumbers(y, parameter_numbers) + + return public_numbers.public_key(backend) + + +def _load_ssh_ecdsa_public_key(expected_key_type, decoded_data, backend): + curve_name, rest = _read_next_string(decoded_data) + data, rest = _read_next_string(rest) + + if expected_key_type != b"ecdsa-sha2-" + curve_name: raise ValueError( - 'Key header and key body contain different key type values.') + 'Key header and key body contain different key type values.' + ) if rest: raise ValueError('Key body contains extra bytes.') - parameter_numbers = DSAParameterNumbers(p, q, g) - public_numbers = DSAPublicNumbers(y, parameter_numbers) + if curve_name == b"nistp256": + curve = ec.SECP256R1() + elif curve_name == b"nistp384": + curve = ec.SECP384R1() + elif curve_name == b"nistp521": + curve = ec.SECP521R1() - return public_numbers.public_key(backend) + if len(data) != 1 + 2 * (curve.key_size // 8): + raise ValueError("Malformed key bytes") + + if six.indexbytes(data, 0) != 4: + raise NotImplementedError( + "Compressed elliptic curve points are not supported" + ) + + x = _int_from_bytes(data[1:1 + curve.key_size // 8], byteorder='big') + y = _int_from_bytes(data[1 + curve.key_size // 8:], byteorder='big') + return ec.EllipticCurvePublicNumbers(x, y, curve).public_key(backend) def _read_next_string(data): - """Retrieves the next RFC 4251 string value from the data.""" + """ + Retrieves the next RFC 4251 string value from the data. + + While the RFC calls these strings, in Python they are bytes objects. + """ str_len, = struct.unpack('>I', data[:4]) return data[4:4 + str_len], data[4 + str_len:] diff --git a/tests/hazmat/primitives/test_serialization.py b/tests/hazmat/primitives/test_serialization.py index f3166d7b..acdbbd73 100644 --- a/tests/hazmat/primitives/test_serialization.py +++ b/tests/hazmat/primitives/test_serialization.py @@ -576,7 +576,7 @@ class TestPEMSerialization(object): @pytest.mark.requires_backend_interface(interface=RSABackend) class TestRSASSHSerialization(object): def test_load_ssh_public_key_unsupported(self, backend): - ssh_key = b'ecdsa-sha2-nistp256 AAAAE2VjZHNhLXNoYTItbmlzdHAyNTY=' + ssh_key = b'ecdsa-sha2-junk AAAAE2VjZHNhLXNoYTItbmlzdHAyNTY=' with pytest.raises(UnsupportedAlgorithm): load_ssh_public_key(ssh_key, backend) @@ -784,3 +784,30 @@ class TestDSSSSHSerialization(object): ) assert numbers == expected + + +@pytest.mark.requires_backend_interface(interface=EllipticCurveBackend) +class TestECDSASSHSerialization(object): + def test_load_ssh_public_key_ecdsa_nist_p256(self, backend): + _skip_curve_unsupported(backend, ec.SECP256R1()) + + ssh_key = ( + b"ecdsa-sha2-nistp256 AAAAE2VjZHNhLXNoYTItbmlzdHAyNTYAAAAIbmlzdHAy" + b"NTYAAABBBGG2MfkHXp0UkxUyllDzWNBAImsvt5t7pFtTXegZK2WbGxml8zMrgWi5" + b"teIg1TO03/FD9hbpBFgBeix3NrCFPls= root@cloud-server-01" + ) + key = load_ssh_public_key(ssh_key, backend) + assert isinstance(key, interfaces.EllipticCurvePublicKey) + + expected_x = int( + "44196257377740326295529888716212621920056478823906609851236662550" + "785814128027", 10 + ) + expected_y = int( + "12257763433170736656417248739355923610241609728032203358057767672" + "925775019611", 10 + ) + + assert key.public_numbers() == ec.EllipticCurvePublicNumbers( + expected_x, expected_y, ec.SECP256R1() + ) |