Source code for google.auth.crypt._python_rsa

# Copyright 2016 Google LLC
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# See the License for the specific language governing permissions and
# limitations under the License.

"""Pure-Python RSA cryptography implementation.

Uses the ``rsa``, ``pyasn1`` and ``pyasn1_modules`` packages
to parse PEM files storing PKCS#1 or PKCS#8 keys as well as
certificates. There is no support for p12 files.

from __future__ import absolute_import

import io

from pyasn1.codec.der import decoder  # type: ignore
from pyasn1_modules import pem  # type: ignore
from pyasn1_modules.rfc2459 import Certificate  # type: ignore
from pyasn1_modules.rfc5208 import PrivateKeyInfo  # type: ignore
import rsa  # type: ignore

from google.auth import _helpers
from google.auth import exceptions
from google.auth.crypt import base

_POW2 = (128, 64, 32, 16, 8, 4, 2, 1)
_PKCS8_MARKER = ("-----BEGIN PRIVATE KEY-----", "-----END PRIVATE KEY-----")
_PKCS8_SPEC = PrivateKeyInfo()

def _bit_list_to_bytes(bit_list):
    """Converts an iterable of 1s and 0s to bytes.

    Combines the list 8 at a time, treating each group of 8 bits
    as a single byte.

        bit_list (Sequence): Sequence of 1s and 0s.

        bytes: The decoded bytes.
    num_bits = len(bit_list)
    byte_vals = bytearray()
    for start in range(0, num_bits, 8):
        curr_bits = bit_list[start : start + 8]
        char_val = sum(val * digit for val, digit in zip(_POW2, curr_bits))
    return bytes(byte_vals)

[docs] class RSAVerifier(base.Verifier): """Verifies RSA cryptographic signatures using public keys. Args: public_key (rsa.key.PublicKey): The public key used to verify signatures. """ def __init__(self, public_key): self._pubkey = public_key
[docs] @_helpers.copy_docstring(base.Verifier) def verify(self, message, signature): message = _helpers.to_bytes(message) try: return rsa.pkcs1.verify(message, signature, self._pubkey) except (ValueError, rsa.pkcs1.VerificationError): return False
[docs] @classmethod def from_string(cls, public_key): """Construct an Verifier instance from a public key or public certificate string. Args: public_key (Union[str, bytes]): The public key in PEM format or the x509 public key certificate. Returns: google.auth.crypt._python_rsa.RSAVerifier: The constructed verifier. Raises: ValueError: If the public_key can't be parsed. """ public_key = _helpers.to_bytes(public_key) is_x509_cert = _CERTIFICATE_MARKER in public_key # If this is a certificate, extract the public key info. if is_x509_cert: der = rsa.pem.load_pem(public_key, "CERTIFICATE") asn1_cert, remaining = decoder.decode(der, asn1Spec=Certificate()) if remaining != b"": raise exceptions.InvalidValue("Unused bytes", remaining) cert_info = asn1_cert["tbsCertificate"]["subjectPublicKeyInfo"] key_bytes = _bit_list_to_bytes(cert_info["subjectPublicKey"]) pubkey = rsa.PublicKey.load_pkcs1(key_bytes, "DER") else: pubkey = rsa.PublicKey.load_pkcs1(public_key, "PEM") return cls(pubkey)
[docs] class RSASigner(base.Signer, base.FromServiceAccountMixin): """Signs messages with an RSA private key. Args: private_key (rsa.key.PrivateKey): The private key to sign with. key_id (str): Optional key ID used to identify this private key. This can be useful to associate the private key with its associated public key or certificate. """ def __init__(self, private_key, key_id=None): self._key = private_key self._key_id = key_id @property # type: ignore @_helpers.copy_docstring(base.Signer) def key_id(self): return self._key_id
[docs] @_helpers.copy_docstring(base.Signer) def sign(self, message): message = _helpers.to_bytes(message) return rsa.pkcs1.sign(message, self._key, "SHA-256")
[docs] @classmethod def from_string(cls, key, key_id=None): """Construct an Signer instance from a private key in PEM format. Args: key (str): Private key in PEM format. key_id (str): An optional key id used to identify the private key. Returns: google.auth.crypt.Signer: The constructed signer. Raises: ValueError: If the key cannot be parsed as PKCS#1 or PKCS#8 in PEM format. """ key = _helpers.from_bytes(key) # PEM expects str in Python 3 marker_id, key_bytes = pem.readPemBlocksFromFile( io.StringIO(key), _PKCS1_MARKER, _PKCS8_MARKER ) # Key is in pkcs1 format. if marker_id == 0: private_key = rsa.key.PrivateKey.load_pkcs1(key_bytes, format="DER") # Key is in pkcs8. elif marker_id == 1: key_info, remaining = decoder.decode(key_bytes, asn1Spec=_PKCS8_SPEC) if remaining != b"": raise exceptions.InvalidValue("Unused bytes", remaining) private_key_info = key_info.getComponentByName("privateKey") private_key = rsa.key.PrivateKey.load_pkcs1( private_key_info.asOctets(), format="DER" ) else: raise exceptions.MalformedError("No key could be detected.") return cls(private_key, key_id=key_id)