import math
import struct
from cryptography.hazmat.backends import default_backend
from cryptography.hazmat.primitives import hashes
from cryptography.hazmat.primitives.asymmetric import padding, rsa
from dns.dnssecalgs.cryptography import CryptographyPrivateKey, CryptographyPublicKey
from dns.dnssectypes import Algorithm
from dns.rdtypes.ANY.DNSKEY import DNSKEY
class PublicRSA(CryptographyPublicKey):
key: rsa.RSAPublicKey
key_cls = rsa.RSAPublicKey
algorithm: Algorithm
chosen_hash: hashes.HashAlgorithm
def verify(self, signature: bytes, data: bytes) -> None:
self.key.verify(signature, data, padding.PKCS1v15(), self.chosen_hash)
def encode_key_bytes(self) -> bytes:
"""Encode a public key per RFC 3110, section 2."""
pn = self.key.public_numbers()
_exp_len = math.ceil(int.bit_length(pn.e) / 8)
exp = int.to_bytes(pn.e, length=_exp_len, byteorder="big")
if _exp_len > 255:
exp_header = b"\0" + struct.pack("!H", _exp_len)
else:
exp_header = struct.pack("!B", _exp_len)
if pn.n.bit_length() < 512 or pn.n.bit_length() > 4096:
raise ValueError("unsupported RSA key length")
return exp_header + exp + pn.n.to_bytes((pn.n.bit_length() + 7) // 8, "big")
@classmethod
def from_dnskey(cls, key: DNSKEY) -> "PublicRSA":
cls._ensure_algorithm_key_combination(key)
keyptr = key.key
(bytes_,) = struct.unpack("!B", keyptr[0:1])
keyptr = keyptr[1:]
if bytes_ == 0:
(bytes_,) = struct.unpack("!H", keyptr[0:2])
keyptr = keyptr[2:]
rsa_e = keyptr[0:bytes_]
rsa_n = keyptr[bytes_:]
return cls(
key=rsa.RSAPublicNumbers(
int.from_bytes(rsa_e, "big"), int.from_bytes(rsa_n, "big")
).public_key(default_backend())
)
class PrivateRSA(CryptographyPrivateKey):
key: rsa.RSAPrivateKey
key_cls = rsa.RSAPrivateKey
public_cls = PublicRSA
default_public_exponent = 65537
def sign(
self,
data: bytes,
verify: bool = False,
deterministic: bool = True,
) -> bytes:
"""Sign using a private key per RFC 3110, section 3."""
signature = self.key.sign(data, padding.PKCS1v15(), self.public_cls.chosen_hash)
if verify:
self.public_key().verify(signature, data)
return signature
@classmethod
def generate(cls, key_size: int) -> "PrivateRSA":
return cls(
key=rsa.generate_private_key(
public_exponent=cls.default_public_exponent,
key_size=key_size,
backend=default_backend(),
)
)
class PublicRSAMD5(PublicRSA):
algorithm = Algorithm.RSAMD5
chosen_hash = hashes.MD5()
class PrivateRSAMD5(PrivateRSA):
public_cls = PublicRSAMD5
class PublicRSASHA1(PublicRSA):
algorithm = Algorithm.RSASHA1
chosen_hash = hashes.SHA1()
class PrivateRSASHA1(PrivateRSA):
public_cls = PublicRSASHA1
class PublicRSASHA1NSEC3SHA1(PublicRSA):
algorithm = Algorithm.RSASHA1NSEC3SHA1
chosen_hash = hashes.SHA1()
class PrivateRSASHA1NSEC3SHA1(PrivateRSA):
public_cls = PublicRSASHA1NSEC3SHA1
class PublicRSASHA256(PublicRSA):
algorithm = Algorithm.RSASHA256
chosen_hash = hashes.SHA256()
class PrivateRSASHA256(PrivateRSA):
public_cls = PublicRSASHA256
class PublicRSASHA512(PublicRSA):
algorithm = Algorithm.RSASHA512
chosen_hash = hashes.SHA512()
class PrivateRSASHA512(PrivateRSA):
public_cls = PublicRSASHA512
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