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# Copyright (c) 2013-2023 by Ron Frederick <ronf@timeheart.net> and others.
#
# This program and the accompanying materials are made available under
# the terms of the Eclipse Public License v2.0 which accompanies this
# distribution and is available at:
#
# http://www.eclipse.org/legal/epl-2.0/
#
# This program may also be made available under the following secondary
# licenses when the conditions for such availability set forth in the
# Eclipse Public License v2.0 are satisfied:
#
# GNU General Public License, Version 2.0, or any later versions of
# that license
#
# SPDX-License-Identifier: EPL-2.0 OR GPL-2.0-or-later
#
# Contributors:
# Ron Frederick - initial implementation, API, and documentation
"""DSA public key encryption handler"""
from typing import Optional, Tuple, Union, cast
from .asn1 import ASN1DecodeError, ObjectIdentifier, der_encode, der_decode
from .crypto import DSAPrivateKey, DSAPublicKey
from .misc import all_ints
from .packet import MPInt, String, SSHPacket
from .public_key import SSHKey, SSHOpenSSHCertificateV01, KeyExportError
from .public_key import register_public_key_alg, register_certificate_alg
from .public_key import register_x509_certificate_alg
_PrivateKeyArgs = Tuple[int, int, int, int, int]
_PublicKeyArgs = Tuple[int, int, int, int]
class _DSAKey(SSHKey):
"""Handler for DSA public key encryption"""
_key: Union[DSAPrivateKey, DSAPublicKey]
algorithm = b'ssh-dss'
default_x509_hash = 'sha256'
pem_name = b'DSA'
pkcs8_oid = ObjectIdentifier('1.2.840.10040.4.1')
sig_algorithms = (algorithm,)
x509_algorithms = (b'x509v3-' + algorithm,)
all_sig_algorithms = set(sig_algorithms)
def __eq__(self, other: object) -> bool:
# This isn't protected access - both objects are _DSAKey instances
# pylint: disable=protected-access
return (isinstance(other, type(self)) and
self._key.p == other._key.p and
self._key.q == other._key.q and
self._key.g == other._key.g and
self._key.y == other._key.y and
self._key.x == other._key.x)
def __hash__(self) -> int:
return hash((self._key.p, self._key.q, self._key.g,
self._key.y, self._key.x))
@classmethod
def generate(cls, algorithm: bytes) -> '_DSAKey': # type: ignore
"""Generate a new DSA private key"""
# pylint: disable=arguments-differ,unused-argument
return cls(DSAPrivateKey.generate(key_size=1024))
@classmethod
def make_private(cls, key_params: object) -> SSHKey:
"""Construct a DSA private key"""
p, q, g, y, x = cast(_PrivateKeyArgs, key_params)
return cls(DSAPrivateKey.construct(p, q, g, y, x))
@classmethod
def make_public(cls, key_params: object) -> SSHKey:
"""Construct a DSA public key"""
p, q, g, y = cast(_PublicKeyArgs, key_params)
return cls(DSAPublicKey.construct(p, q, g, y))
@classmethod
def decode_pkcs1_private(cls, key_data: object) -> \
Optional[_PrivateKeyArgs]:
"""Decode a PKCS#1 format DSA private key"""
if (isinstance(key_data, tuple) and len(key_data) == 6 and
all_ints(key_data) and key_data[0] == 0):
return cast(_PrivateKeyArgs, key_data[1:])
else:
return None
@classmethod
def decode_pkcs1_public(cls, key_data: object) -> \
Optional[_PublicKeyArgs]:
"""Decode a PKCS#1 format DSA public key"""
if (isinstance(key_data, tuple) and len(key_data) == 4 and
all_ints(key_data)):
y, p, q, g = key_data
return p, q, g, y
else:
return None
@classmethod
def decode_pkcs8_private(cls, alg_params: object,
data: bytes) -> Optional[_PrivateKeyArgs]:
"""Decode a PKCS#8 format DSA private key"""
try:
x = der_decode(data)
except ASN1DecodeError:
return None
if (isinstance(alg_params, tuple) and len(alg_params) == 3 and
all_ints(alg_params) and isinstance(x, int)):
p, q, g = alg_params
y: int = pow(g, x, p)
return p, q, g, y, x
else:
return None
@classmethod
def decode_pkcs8_public(cls, alg_params: object,
data: bytes) -> Optional[_PublicKeyArgs]:
"""Decode a PKCS#8 format DSA public key"""
try:
y = der_decode(data)
except ASN1DecodeError:
return None
if (isinstance(alg_params, tuple) and len(alg_params) == 3 and
all_ints(alg_params) and isinstance(y, int)):
p, q, g = alg_params
return p, q, g, y
else:
return None
@classmethod
def decode_ssh_private(cls, packet: SSHPacket) -> _PrivateKeyArgs:
"""Decode an SSH format DSA private key"""
p = packet.get_mpint()
q = packet.get_mpint()
g = packet.get_mpint()
y = packet.get_mpint()
x = packet.get_mpint()
return p, q, g, y, x
@classmethod
def decode_ssh_public(cls, packet: SSHPacket) -> _PublicKeyArgs:
"""Decode an SSH format DSA public key"""
p = packet.get_mpint()
q = packet.get_mpint()
g = packet.get_mpint()
y = packet.get_mpint()
return p, q, g, y
def encode_pkcs1_private(self) -> object:
"""Encode a PKCS#1 format DSA private key"""
if not self._key.x:
raise KeyExportError('Key is not private')
return (0, self._key.p, self._key.q, self._key.g,
self._key.y, self._key.x)
def encode_pkcs1_public(self) -> object:
"""Encode a PKCS#1 format DSA public key"""
return (self._key.y, self._key.p, self._key.q, self._key.g)
def encode_pkcs8_private(self) -> Tuple[object, object]:
"""Encode a PKCS#8 format DSA private key"""
if not self._key.x:
raise KeyExportError('Key is not private')
return (self._key.p, self._key.q, self._key.g), der_encode(self._key.x)
def encode_pkcs8_public(self) -> Tuple[object, object]:
"""Encode a PKCS#8 format DSA public key"""
return (self._key.p, self._key.q, self._key.g), der_encode(self._key.y)
def encode_ssh_private(self) -> bytes:
"""Encode an SSH format DSA private key"""
if not self._key.x:
raise KeyExportError('Key is not private')
return b''.join((MPInt(self._key.p), MPInt(self._key.q),
MPInt(self._key.g), MPInt(self._key.y),
MPInt(self._key.x)))
def encode_ssh_public(self) -> bytes:
"""Encode an SSH format DSA public key"""
return b''.join((MPInt(self._key.p), MPInt(self._key.q),
MPInt(self._key.g), MPInt(self._key.y)))
def encode_agent_cert_private(self) -> bytes:
"""Encode DSA certificate private key data for agent"""
if not self._key.x:
raise KeyExportError('Key is not private')
return MPInt(self._key.x)
def sign_ssh(self, data: bytes, sig_algorithm: bytes) -> bytes:
"""Compute an SSH-encoded signature of the specified data"""
# pylint: disable=unused-argument
if not self._key.x:
raise ValueError('Private key needed for signing')
sig = der_decode(self._key.sign(data, 'sha1'))
r, s = cast(Tuple[int, int], sig)
return String(r.to_bytes(20, 'big') + s.to_bytes(20, 'big'))
def verify_ssh(self, data: bytes, sig_algorithm: bytes,
packet: SSHPacket) -> bool:
"""Verify an SSH-encoded signature of the specified data"""
# pylint: disable=unused-argument
sig = packet.get_string()
packet.check_end()
if len(sig) != 40:
return False
r = int.from_bytes(sig[:20], 'big')
s = int.from_bytes(sig[20:], 'big')
return self._key.verify(data, der_encode((r, s)), 'sha1')
register_public_key_alg(b'ssh-dss', _DSAKey, False)
register_certificate_alg(1, b'ssh-dss', b'ssh-dss-cert-v01@openssh.com',
_DSAKey, SSHOpenSSHCertificateV01, False)
for alg in _DSAKey.x509_algorithms:
register_x509_certificate_alg(alg, False)
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