Split crypt into a package to allow alternative implementations (#189)
diff --git a/google/auth/crypt/__init__.py b/google/auth/crypt/__init__.py
new file mode 100644
index 0000000..fa59662
--- /dev/null
+++ b/google/auth/crypt/__init__.py
@@ -0,0 +1,79 @@
+# 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.
+
+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 six
+
+from google.auth.crypt import base
+from google.auth.crypt import rsa
+
+
+__all__ = [
+ 'RSASigner',
+ 'RSAVerifier',
+ 'Signer',
+ 'Verifier',
+]
+
+# Aliases to maintain the v1.0.0 interface, as the crypt module was split
+# into submodules.
+Signer = base.Signer
+Verifier = base.Verifier
+RSASigner = rsa.RSASigner
+RSAVerifier = rsa.RSAVerifier
+
+
+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 = rsa.RSAVerifier.from_string(cert)
+ if verifier.verify(message, signature):
+ return True
+ return False
diff --git a/google/auth/crypt/_python_rsa.py b/google/auth/crypt/_python_rsa.py
new file mode 100644
index 0000000..1f6384d
--- /dev/null
+++ b/google/auth/crypt/_python_rsa.py
@@ -0,0 +1,221 @@
+# 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)
diff --git a/google/auth/crypt/base.py b/google/auth/crypt/base.py
new file mode 100644
index 0000000..05c5a2b
--- /dev/null
+++ b/google/auth/crypt/base.py
@@ -0,0 +1,64 @@
+# 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.
+
+"""Base classes for cryptographic signers and verifiers."""
+
+import abc
+
+import six
+
+
+@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')
+
+
+@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')
diff --git a/google/auth/crypt/rsa.py b/google/auth/crypt/rsa.py
new file mode 100644
index 0000000..d0bf2a0
--- /dev/null
+++ b/google/auth/crypt/rsa.py
@@ -0,0 +1,20 @@
+# Copyright 2017 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.
+
+"""RSA cryptography signer and verifier."""
+
+from google.auth.crypt import _python_rsa
+
+RSASigner = _python_rsa.RSASigner
+RSAVerifier = _python_rsa.RSAVerifier