# Copyright 2016 Google Inc. # # 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 # # http://www.apache.org/licenses/LICENSE-2.0 # # Unless required by applicable law or agreed to in writing, software # distributed under the License is distributed on an "AS IS" BASIS, # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. # 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 import json from pyasn1.codec.der import decoder from pyasn1_modules import pem from pyasn1_modules.rfc2459 import Certificate from pyasn1_modules.rfc5208 import PrivateKeyInfo import rsa import six from google.auth import _helpers from google.auth.crypt import base _POW2 = (128, 64, 32, 16, 8, 4, 2, 1) _CERTIFICATE_MARKER = b'-----BEGIN CERTIFICATE-----' _PKCS1_MARKER = ('-----BEGIN RSA PRIVATE KEY-----', '-----END RSA PRIVATE KEY-----') _PKCS8_MARKER = ('-----BEGIN PRIVATE KEY-----', '-----END PRIVATE KEY-----') _PKCS8_SPEC = PrivateKeyInfo() _JSON_FILE_PRIVATE_KEY = 'private_key' _JSON_FILE_PRIVATE_KEY_ID = 'private_key_id' 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. Args: bit_list (Sequence): Sequence of 1s and 0s. Returns: bytes: The decoded bytes. """ num_bits = len(bit_list) byte_vals = bytearray() for start in six.moves.xrange(0, num_bits, 8): curr_bits = bit_list[start:start + 8] char_val = sum( val * digit for val, digit in six.moves.zip(_POW2, curr_bits)) byte_vals.append(char_val) return bytes(byte_vals) 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 @_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 @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: Verifier: 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 ValueError('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) class RSASigner(base.Signer): """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 @_helpers.copy_docstring(base.Signer) def key_id(self): return self._key_id @_helpers.copy_docstring(base.Signer) def sign(self, message): message = _helpers.to_bytes(message) return rsa.pkcs1.sign(message, self._key, 'SHA-256') @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( six.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 ValueError('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 ValueError('No key could be detected.') return cls(private_key, key_id=key_id) @classmethod def from_service_account_info(cls, info): """Creates a Signer instance instance from a dictionary containing service account info in Google format. Args: info (Mapping[str, str]): The service account info in Google format. Returns: google.auth.crypt.Signer: The constructed signer. Raises: ValueError: If the info is not in the expected format. """ if _JSON_FILE_PRIVATE_KEY not in info: raise ValueError( 'The private_key field was not found in the service account ' 'info.') return cls.from_string( info[_JSON_FILE_PRIVATE_KEY], info.get(_JSON_FILE_PRIVATE_KEY_ID)) @classmethod def from_service_account_file(cls, filename): """Creates a Signer instance from a service account .json file in Google format. Args: filename (str): The path to the service account .json file. Returns: google.auth.crypt.Signer: The constructed signer. """ with io.open(filename, 'r', encoding='utf-8') as json_file: data = json.load(json_file) return cls.from_service_account_info(data)