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# Copyright 2014 Google Inc. All rights reserved.
#
# 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.
"""ADB authentication using the ``rsa`` package.
.. rubric:: Contents
* :class:`_Accum`
* :meth:`_Accum.digest`
* :meth:`_Accum.update`
* :func:`_load_rsa_private_key`
* :class:`PythonRSASigner`
* :meth:`PythonRSASigner.FromRSAKeyPath`
* :meth:`PythonRSASigner.GetPublicKey`
* :meth:`PythonRSASigner.Sign`
"""
from pyasn1.codec.der import decoder
from pyasn1.type import univ
import rsa
from rsa import pkcs1
class _Accum(object):
"""A fake hashing algorithm.
The Python ``rsa`` lib hashes all messages it signs. ADB does it already, we just
need to slap a signature on top of already hashed message. Introduce a "fake"
hashing algo for this.
Attributes
----------
_buf : bytes
A buffer for storing data before it is signed
"""
def __init__(self):
self._buf = b''
def update(self, msg):
"""Update this hash object's state with the provided ``msg``.
Parameters
----------
msg : bytes
The message to be appended to ``self._buf``
"""
self._buf += msg
def digest(self):
"""Return the digest value as a string of binary data.
Returns
-------
self._buf : bytes
``self._buf``
"""
return self._buf
pkcs1.HASH_METHODS['SHA-1-PREHASHED'] = _Accum
pkcs1.HASH_ASN1['SHA-1-PREHASHED'] = pkcs1.HASH_ASN1['SHA-1']
def _load_rsa_private_key(pem):
"""PEM encoded PKCS#8 private key -> ``rsa.PrivateKey``.
ADB uses private RSA keys in pkcs#8 format. The ``rsa`` library doesn't
support them natively. Do some ASN unwrapping to extract naked RSA key
(in der-encoded form).
See:
* https://www.ietf.org/rfc/rfc2313.txt
* http://superuser.com/a/606266
Parameters
----------
pem : str
The private key to be loaded
Returns
-------
rsa.key.PrivateKey
The loaded private key
"""
try:
der = rsa.pem.load_pem(pem, 'PRIVATE KEY')
keyinfo, _ = decoder.decode(der)
if keyinfo[1][0] != univ.ObjectIdentifier('1.2.840.113549.1.1.1'):
raise ValueError('Not a DER-encoded OpenSSL private RSA key')
private_key_der = keyinfo[2].asOctets()
except IndexError:
raise ValueError('Not a DER-encoded OpenSSL private RSA key')
return rsa.PrivateKey.load_pkcs1(private_key_der, format='DER')
class PythonRSASigner(object):
"""Implements :class:`adb_protocol.AuthSigner` using http://stuvel.eu/rsa.
Parameters
----------
pub : str, None
The contents of the public key file
priv : str, None
The contents of the private key file
Attributes
----------
priv_key : rsa.key.PrivateKey
The loaded private key
pub_key : str, None
The contents of the public key file
"""
def __init__(self, pub=None, priv=None):
self.priv_key = _load_rsa_private_key(priv)
self.pub_key = pub
@classmethod
def FromRSAKeyPath(cls, rsa_key_path):
"""Create a :class:`PythonRSASigner` instance using the provided private key.
Parameters
----------
rsa_key_path : str
The path to the private key; the public key must be ``rsa_key_path + '.pub'``.
Returns
-------
PythonRSASigner
A :class:`PythonRSASigner` with private key ``rsa_key_path`` and public key ``rsa_key_path + '.pub'``
"""
with open(rsa_key_path + '.pub') as f:
pub = f.read()
with open(rsa_key_path) as f:
priv = f.read()
return cls(pub, priv)
def Sign(self, data):
"""Signs given data using a private key.
Parameters
----------
data : bytes
The data to be signed
Returns
-------
bytes
The signed ``data``
"""
return rsa.sign(data, self.priv_key, 'SHA-1-PREHASHED')
def GetPublicKey(self):
"""Returns the public key in PEM format without headers or newlines.
Returns
-------
self.pub_key : str, None
The contents of the public key file, or ``None`` if a public key was not provided.
"""
return self.pub_key
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