| import struct |
|
|
| from cryptography.hazmat.backends import default_backend |
| from cryptography.hazmat.primitives import hashes |
| from cryptography.hazmat.primitives.asymmetric import dsa, utils |
|
|
| from dns.dnssecalgs.cryptography import CryptographyPrivateKey, CryptographyPublicKey |
| from dns.dnssectypes import Algorithm |
| from dns.rdtypes.ANY.DNSKEY import DNSKEY |
|
|
|
|
| class PublicDSA(CryptographyPublicKey): |
| key: dsa.DSAPublicKey |
| key_cls = dsa.DSAPublicKey |
| algorithm = Algorithm.DSA |
| chosen_hash = hashes.SHA1() |
|
|
| def verify(self, signature: bytes, data: bytes) -> None: |
| sig_r = signature[1:21] |
| sig_s = signature[21:] |
| sig = utils.encode_dss_signature( |
| int.from_bytes(sig_r, "big"), int.from_bytes(sig_s, "big") |
| ) |
| self.key.verify(sig, data, self.chosen_hash) |
|
|
| def encode_key_bytes(self) -> bytes: |
| """Encode a public key per RFC 2536, section 2.""" |
| pn = self.key.public_numbers() |
| dsa_t = (self.key.key_size // 8 - 64) // 8 |
| if dsa_t > 8: |
| raise ValueError("unsupported DSA key size") |
| octets = 64 + dsa_t * 8 |
| res = struct.pack("!B", dsa_t) |
| res += pn.parameter_numbers.q.to_bytes(20, "big") |
| res += pn.parameter_numbers.p.to_bytes(octets, "big") |
| res += pn.parameter_numbers.g.to_bytes(octets, "big") |
| res += pn.y.to_bytes(octets, "big") |
| return res |
|
|
| @classmethod |
| def from_dnskey(cls, key: DNSKEY) -> "PublicDSA": |
| cls._ensure_algorithm_key_combination(key) |
| keyptr = key.key |
| (t,) = struct.unpack("!B", keyptr[0:1]) |
| keyptr = keyptr[1:] |
| octets = 64 + t * 8 |
| dsa_q = keyptr[0:20] |
| keyptr = keyptr[20:] |
| dsa_p = keyptr[0:octets] |
| keyptr = keyptr[octets:] |
| dsa_g = keyptr[0:octets] |
| keyptr = keyptr[octets:] |
| dsa_y = keyptr[0:octets] |
| return cls( |
| key=dsa.DSAPublicNumbers( |
| int.from_bytes(dsa_y, "big"), |
| dsa.DSAParameterNumbers( |
| int.from_bytes(dsa_p, "big"), |
| int.from_bytes(dsa_q, "big"), |
| int.from_bytes(dsa_g, "big"), |
| ), |
| ).public_key(default_backend()), |
| ) |
|
|
|
|
| class PrivateDSA(CryptographyPrivateKey): |
| key: dsa.DSAPrivateKey |
| key_cls = dsa.DSAPrivateKey |
| public_cls = PublicDSA |
|
|
| def sign( |
| self, |
| data: bytes, |
| verify: bool = False, |
| deterministic: bool = True, |
| ) -> bytes: |
| """Sign using a private key per RFC 2536, section 3.""" |
| public_dsa_key = self.key.public_key() |
| if public_dsa_key.key_size > 1024: |
| raise ValueError("DSA key size overflow") |
| der_signature = self.key.sign(data, self.public_cls.chosen_hash) |
| dsa_r, dsa_s = utils.decode_dss_signature(der_signature) |
| dsa_t = (public_dsa_key.key_size // 8 - 64) // 8 |
| octets = 20 |
| signature = ( |
| struct.pack("!B", dsa_t) |
| + int.to_bytes(dsa_r, length=octets, byteorder="big") |
| + int.to_bytes(dsa_s, length=octets, byteorder="big") |
| ) |
| if verify: |
| self.public_key().verify(signature, data) |
| return signature |
|
|
| @classmethod |
| def generate(cls, key_size: int) -> "PrivateDSA": |
| return cls( |
| key=dsa.generate_private_key(key_size=key_size), |
| ) |
|
|
|
|
| class PublicDSANSEC3SHA1(PublicDSA): |
| algorithm = Algorithm.DSANSEC3SHA1 |
|
|
|
|
| class PrivateDSANSEC3SHA1(PrivateDSA): |
| public_cls = PublicDSANSEC3SHA1 |
|
|
