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# 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.
from cryptography.hazmat.backends import default_backend
from cryptography.hazmat.primitives.asymmetric import padding
from cryptography.hazmat.primitives.asymmetric import utils
from cryptography.hazmat.primitives import hashes
from cryptography.hazmat.primitives import serialization
from openstack import exceptions
from openstack.image.iterable_chunked_file import IterableChunkedFile
HASH_METHODS = {
'SHA-224': hashes.SHA224(),
'SHA-256': hashes.SHA256(),
'SHA-384': hashes.SHA384(),
'SHA-512': hashes.SHA512(),
}
class ImageSigner:
"""Image file signature generator.
Generates signatures for files using a specified private key file.
"""
def __init__(self, hash_method='SHA-256', padding_method='RSA-PSS'):
padding_types = {
'RSA-PSS': padding.PSS(
mgf=padding.MGF1(HASH_METHODS[hash_method]),
salt_length=padding.PSS.MAX_LENGTH,
)
}
# informational attributes
self.hash_method = hash_method
self.padding_method = padding_method
# runtime objects
self.private_key = None
self.hash = HASH_METHODS[hash_method]
self.hasher = hashes.Hash(self.hash, default_backend())
self.padding = padding_types[padding_method]
def load_private_key(self, file_path, password=None):
with open(file_path, 'rb') as key_file:
self.private_key = serialization.load_pem_private_key(
key_file.read(), password=password, backend=default_backend()
)
def generate_signature(self, file_obj):
if not self.private_key:
raise exceptions.SDKException("private_key not set")
file_obj.seek(0)
chunked_file = IterableChunkedFile(file_obj)
for chunk in chunked_file:
self.hasher.update(chunk)
file_obj.seek(0)
digest = self.hasher.finalize()
signature = self.private_key.sign(
digest, self.padding, utils.Prehashed(self.hash)
)
return signature
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