from cryptography.hazmat.backends import default_backend
from cryptography.hazmat.primitives import hashes
from cryptography.hazmat.primitives.asymmetric import ec, utils
from dns.dnssecalgs.cryptography import CryptographyPrivateKey, CryptographyPublicKey
from dns.dnssectypes import Algorithm
from dns.rdtypes.ANY.DNSKEY import DNSKEY
class PublicECDSA(CryptographyPublicKey):
key: ec.EllipticCurvePublicKey
key_cls = ec.EllipticCurvePublicKey
algorithm: Algorithm
chosen_hash: hashes.HashAlgorithm
curve: ec.EllipticCurve
octets: int
def verify(self, signature: bytes, data: bytes) -> None:
sig_r = signature[0 : self.octets]
sig_s = signature[self.octets :]
sig = utils.encode_dss_signature(
int.from_bytes(sig_r, "big"), int.from_bytes(sig_s, "big")
)
self.key.verify(sig, data, ec.ECDSA(self.chosen_hash))
def encode_key_bytes(self) -> bytes:
"""Encode a public key per RFC 6605, section 4."""
pn = self.key.public_numbers()
return pn.x.to_bytes(self.octets, "big") + pn.y.to_bytes(self.octets, "big")
@classmethod
def from_dnskey(cls, key: DNSKEY) -> "PublicECDSA":
cls._ensure_algorithm_key_combination(key)
ecdsa_x = key.key[0 : cls.octets]
ecdsa_y = key.key[cls.octets : cls.octets * 2]
return cls(
key=ec.EllipticCurvePublicNumbers(
curve=cls.curve,
x=int.from_bytes(ecdsa_x, "big"),
y=int.from_bytes(ecdsa_y, "big"),
).public_key(default_backend()),
)
class PrivateECDSA(CryptographyPrivateKey):
key: ec.EllipticCurvePrivateKey
key_cls = ec.EllipticCurvePrivateKey
public_cls = PublicECDSA
def sign(
self,
data: bytes,
verify: bool = False,
deterministic: bool = True,
) -> bytes:
"""Sign using a private key per RFC 6605, section 4."""
algorithm = ec.ECDSA(
self.public_cls.chosen_hash, deterministic_signing=deterministic
)
der_signature = self.key.sign(data, algorithm)
dsa_r, dsa_s = utils.decode_dss_signature(der_signature)
signature = int.to_bytes(
dsa_r, length=self.public_cls.octets, byteorder="big"
) + int.to_bytes(dsa_s, length=self.public_cls.octets, byteorder="big")
if verify:
self.public_key().verify(signature, data)
return signature
@classmethod
def generate(cls) -> "PrivateECDSA":
return cls(
key=ec.generate_private_key(
curve=cls.public_cls.curve, backend=default_backend()
),
)
class PublicECDSAP256SHA256(PublicECDSA):
algorithm = Algorithm.ECDSAP256SHA256
chosen_hash = hashes.SHA256()
curve = ec.SECP256R1()
octets = 32
class PrivateECDSAP256SHA256(PrivateECDSA):
public_cls = PublicECDSAP256SHA256
class PublicECDSAP384SHA384(PublicECDSA):
algorithm = Algorithm.ECDSAP384SHA384
chosen_hash = hashes.SHA384()
curve = ec.SECP384R1()
octets = 48
class PrivateECDSAP384SHA384(PrivateECDSA):
public_cls = PublicECDSAP384SHA384
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