Python cryptography.hazmat.primitives.asymmetric.utils.encode_dss_signature() Examples

def verify_digest(hash_hex, pubkey_hex, sigb64, hashfunc=hashlib.sha256):
    """
    Given a digest, public key (as hex), and a base64 signature,
    verify that the public key signed the digest.
    Return True if so
    Return False if not
    """
    if not isinstance(hash_hex, (str, unicode)):
        raise ValueError("hash hex is not a string")

    hash_hex = str(hash_hex)
    pubk_uncompressed_hex = keylib.key_formatting.decompress(pubkey_hex)
    sig_r, sig_s = decode_signature(sigb64)

    pubk = ec.EllipticCurvePublicNumbers.from_encoded_point(ec.SECP256K1(), pubk_uncompressed_hex.decode('hex')).public_key(default_backend())
    signature = encode_dss_signature(sig_r, sig_s)

    try:
        pubk.verify(signature, hash_hex.decode('hex'), ec.ECDSA(utils.Prehashed(hashes.SHA256())))
        return True
    except InvalidSignature:
        return False 

def verify(self, key, payload, signature):
        pkey = key.get_op_key('verify', self._curve)
        r = signature[:len(signature) // 2]
        s = signature[len(signature) // 2:]
        enc_signature = ec_utils.encode_dss_signature(
            int(hexlify(r), 16), int(hexlify(s), 16))
        pkey.verify(enc_signature, payload, ec.ECDSA(self.hashfn)) 

def _ecc_static_length_signature(key, algorithm, digest):
    """Calculates an elliptic curve signature with a static length using pre-calculated hash.

    :param key: Elliptic curve private key
    :type key: cryptography.hazmat.primitives.asymmetric.ec.EllipticCurvePrivateKey
    :param algorithm: Master algorithm to use
    :type algorithm: aws_encryption_sdk.identifiers.Algorithm
    :param bytes digest: Pre-calculated hash digest
    :returns: Signature with required length
    :rtype: bytes
    """
    pre_hashed_algorithm = ec.ECDSA(Prehashed(algorithm.signing_hash_type()))
    signature = b""
    while len(signature) != algorithm.signature_len:
        _LOGGER.debug(
            "Signature length %d is not desired length %d.  Recalculating.", len(signature), algorithm.signature_len
        )
        signature = key.sign(digest, pre_hashed_algorithm)
        if len(signature) != algorithm.signature_len:
            # Most of the time, a signature of the wrong length can be fixed
            # by negating s in the signature relative to the group order.
            _LOGGER.debug(
                "Signature length %d is not desired length %d.  Negating s.", len(signature), algorithm.signature_len
            )
            r, s = decode_dss_signature(signature)
            s = _ECC_CURVE_PARAMETERS[algorithm.signing_algorithm_info.name].order - s
            signature = encode_dss_signature(r, s)
    return signature 

def extract_signature(auth):
        # type: (str) -> Tuple[str, str]
        """Fix the JWT auth token.

        The JWA spec defines the signature to be a pair of 32octet encoded
        longs.
        The `ecdsa` library signs using a raw, 32octet pair of values (s, r).
        Cryptography, which uses OpenSSL, uses a DER sequence of (s, r).
        This function converts the raw ecdsa to DER.

        :param auth: A JWT authorization token.
        :type auth: str

        :return tuple containing the signature material and signature

        """
        payload, asig = auth.encode('utf8').rsplit(".", 1)
        sig = base64.urlsafe_b64decode(repad(asig))
        if len(sig) != 64:
            return payload, sig

        encoded = utils.encode_dss_signature(
            s=int(binascii.hexlify(sig[32:]), 16),
            r=int(binascii.hexlify(sig[:32]), 16)
        )
        return payload, encoded 

def verify(self, signature, msg):
        """
        Verify whether a given signature is correct for a message.

        :param signature: the given signature
        :param msg: the given message
        """
        length = len(signature) // 2
        r = signature[:length]
        # remove all "\x00" prefixes
        while r and r[0:1] == "\x00":
            r = r[1:]
        # prepend "\x00" when the most significant bit is set
        if ord(r[0:1]) & 128:
            r = "\x00" + r

        s = signature[length:]
        # remove all "\x00" prefixes
        while s and s[0:1] == "\x00":
            s = s[1:]
        # prepend "\x00" when the most significant bit is set
        if ord(s[0:1]) & 128:
            s = "\x00" + s
        # turn back into int
        r = int(hexlify(r), 16)
        s = int(hexlify(s), 16)
        # verify
        try:
            if NEW_CRYPTOGRAPHY_SIGN_VERSION:
                self.ec.verify(encode_dss_signature(r, s), msg, ec.ECDSA(hashes.SHA1()))
            else:
                self.ec.verifier(encode_dss_signature(r, s), ec.ECDSA(hashes.SHA1()))
            return True
        except InvalidSignature:
            return False 

def verify(self, message, signature):
        # First convert (r||s) raw signature to ASN1 encoded signature.
        sig_bytes = _helpers.to_bytes(signature)
        if len(sig_bytes) != 64:
            return False
        r = utils.int_from_bytes(sig_bytes[:32], byteorder="big")
        s = utils.int_from_bytes(sig_bytes[32:], byteorder="big")
        asn1_sig = encode_dss_signature(r, s)

        message = _helpers.to_bytes(message)
        try:
            self._pubkey.verify(asn1_sig, message, ec.ECDSA(hashes.SHA256()))
            return True
        except (ValueError, cryptography.exceptions.InvalidSignature):
            return False 

def __init__(self, pubkey_hex, sigb64):
        """
        Instantiate the verifier with a hex-encoded public key and a base64-encoded signature
        """
        sig_r, sig_s = decode_signature(sigb64)
        pubkey_hex_decompressed = keylib.key_formatting.decompress(pubkey_hex)
        pubk = ec.EllipticCurvePublicNumbers.from_encoded_point(ec.SECP256K1(), pubkey_hex_decompressed.decode('hex')).public_key(default_backend())
        signature = encode_dss_signature(sig_r, sig_s)
        self.verifier = pubk.verifier(signature, ec.ECDSA(hashes.SHA256())) 

def _encode_dss_signature(self, raw_signature, key_size_bits):
        want_raw_signature_len = bits_to_bytes_unit(key_size_bits) * 2
        if len(raw_signature) != want_raw_signature_len:
            raise InvalidSignature(
                "Expected %d byte SignatureValue, got %d"
                % (want_raw_signature_len, len(raw_signature))
            )
        int_len = len(raw_signature) // 2
        r = bytes_to_long(raw_signature[:int_len])
        s = bytes_to_long(raw_signature[int_len:])
        return utils.encode_dss_signature(r, s) 

def encryptPassword(self, login, passwd):
        """Encrypt credentials using the google publickey, with the
        RSA algorithm"""

        # structure of the binary key:
        #
        # *-------------------------------------------------------*
        # | modulus_length | modulus | exponent_length | exponent |
        # *-------------------------------------------------------*
        #
        # modulus_length and exponent_length are uint32
        binaryKey = b64decode(config.GOOGLE_PUBKEY)
        # modulus
        i = utils.readInt(binaryKey, 0)
        modulus = utils.toBigInt(binaryKey[4:][0:i])
        # exponent
        j = utils.readInt(binaryKey, i + 4)
        exponent = utils.toBigInt(binaryKey[i + 8:][0:j])

        # calculate SHA1 of the pub key
        digest = hashes.Hash(hashes.SHA1(), backend=default_backend())
        digest.update(binaryKey)
        h = b'\x00' + digest.finalize()[0:4]

        # generate a public key
        der_data = encode_dss_signature(modulus, exponent)
        publicKey = load_der_public_key(der_data, backend=default_backend())

        # encrypt email and password using pubkey
        to_be_encrypted = login.encode() + b'\x00' + passwd.encode()
        ciphertext = publicKey.encrypt(
            to_be_encrypted,
            padding.OAEP(
                mgf=padding.MGF1(algorithm=hashes.SHA1()),
                algorithm=hashes.SHA1(),
                label=None
            )
        )

        return urlsafe_b64encode(h + ciphertext) 

def _raw_to_der(self, raw_signature):
        """Convert signature from RAW encoding to DER encoding."""
        component_length = self._sig_component_length()
        if len(raw_signature) != int(2 * component_length):
            raise ValueError("Invalid signature")

        r_bytes = raw_signature[:component_length]
        s_bytes = raw_signature[component_length:]
        r = int_from_bytes(r_bytes, "big")
        s = int_from_bytes(s_bytes, "big")
        return encode_dss_signature(r, s) 

def _der_encoded_bytes(self) -> bytes:
        return utils.encode_dss_signature(int(self.r), int(self.s)) 

def get_signature_params(data):
  """
  <Purpose>
    Parse the signature parameters as multi-precision-integers.

  <Arguments>
    data:
           the RFC4880-encoded signature data buffer as described
           in the fourth paragraph of section 5.2.2

  <Exceptions>
    securesystemslib.gpg.exceptions.PacketParsingError:
           if the public key parameters are malformed

    securesystemslib.exceptions.UnsupportedLibraryError:
           if the cryptography module is not available

  <Side Effects>
    None.

  <Returns>
    The decoded signature buffer
  """
  if not CRYPTO: # pragma: no cover
    return securesystemslib.exceptions.UnsupportedLibraryError(NO_CRYPTO_MSG)

  ptr = 0
  r_length = securesystemslib.gpg.util.get_mpi_length(data[ptr:ptr+2])
  ptr += 2
  r = data[ptr:ptr + r_length]
  if len(r) != r_length: # pragma: no cover
    raise securesystemslib.gpg.exceptions.PacketParsingError(
        "r-value truncated in signature")
  ptr += r_length

  s_length = securesystemslib.gpg.util.get_mpi_length(data[ptr: ptr+2])
  ptr += 2
  s = data[ptr: ptr + s_length]
  if len(s) != s_length: # pragma: no cover
    raise securesystemslib.gpg.exceptions.PacketParsingError(
        "s-value truncated in signature")

  s = int(binascii.hexlify(s), 16)
  r = int(binascii.hexlify(r), 16)

  signature = dsautils.encode_dss_signature(r, s)

  return signature