Replace custom blob gRPC API with ByteStream

client/third_party/google/auth/crypt.py

+# 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.
+
+"""Cryptography helpers for verifying and signing messages.
+
+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.
+
+The simplest way to verify signatures is using :func:`verify_signature`::
+
+    cert = open('certs.pem').read()
+    valid = crypt.verify_signature(message, signature, cert)
+
+If you're going to verify many messages with the same certificate, you can use
+:class:`RSAVerifier`::
+
+    cert = open('certs.pem').read()
+    verifier = crypt.RSAVerifier.from_string(cert)
+    valid = verifier.verify(message, signature)
+
+
+To sign messages use :class:`RSASigner` with a private key::
+
+    private_key = open('private_key.pem').read()
+    signer = crypt.RSASigner(private_key)
+    signature = signer.sign(message)
+
+"""
+import abc
+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
+
+_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)
+
+
+@six.add_metaclass(abc.ABCMeta)
+class Verifier(object):
+    """Abstract base class for crytographic signature verifiers."""
+
+    @abc.abstractmethod
+    def verify(self, message, signature):
+        """Verifies a message against a cryptographic signature.
+
+        Args:
+            message (Union[str, bytes]): The message to verify.
+            signature (Union[str, bytes]): The cryptography signature to check.
+
+        Returns:
+            bool: True if message was signed by the private key associated
+            with the public key that this object was constructed with.
+        """
+        # pylint: disable=missing-raises-doc,redundant-returns-doc
+        # (pylint doesn't recognize that this is abstract)
+        raise NotImplementedError('Verify must be implemented')
+
+
+class RSAVerifier(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(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)
+
+
+def verify_signature(message, signature, certs):
+    """Verify an RSA cryptographic signature.
+
+    Checks that the provided ``signature`` was generated from ``bytes`` using
+    the private key associated with the ``cert``.
+
+    Args:
+        message (Union[str, bytes]): The plaintext message.
+        signature (Union[str, bytes]): The cryptographic signature to check.
+        certs (Union[Sequence, str, bytes]): The certificate or certificates
+            to use to check the signature.
+
+    Returns:
+        bool: True if the signature is valid, otherwise False.
+    """
+    if isinstance(certs, (six.text_type, six.binary_type)):
+        certs = [certs]
+
+    for cert in certs:
+        verifier = RSAVerifier.from_string(cert)
+        if verifier.verify(message, signature):
+            return True
+    return False
+
+
+@six.add_metaclass(abc.ABCMeta)
+class Signer(object):
+    """Abstract base class for cryptographic signers."""
+
+    @abc.abstractproperty
+    def key_id(self):
+        """Optional[str]: The key ID used to identify this private key."""
+        raise NotImplementedError('Key id must be implemented')
+
+    @abc.abstractmethod
+    def sign(self, message):
+        """Signs a message.
+
+        Args:
+            message (Union[str, bytes]): The message to be signed.
+
+        Returns:
+            bytes: The signature of the message.
+        """
+        # pylint: disable=missing-raises-doc,redundant-returns-doc
+        # (pylint doesn't recognize that this is abstract)
+        raise NotImplementedError('Sign must be implemented')
+
+
+class RSASigner(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(Signer)
+    def key_id(self):
+        return self._key_id
+
+    @_helpers.copy_docstring(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)