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