57 lines
1.9 KiB
Python
57 lines
1.9 KiB
Python
# -*- coding: utf-8 -*-
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#
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# Author: François Rossigneux <francois.rossigneux@inria.fr>
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#
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# Licensed under the Apache License, Version 2.0 (the "License"); you may
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# not use this file except in compliance with the License. You may obtain
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# a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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# License for the specific language governing permissions and limitations
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# under the License.
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"""Computes the signature of a metering message."""
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import hashlib
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import hmac
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def recursive_keypairs(d):
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"""Generator that produces sequence of keypairs for nested dictionaries."""
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for name, value in sorted(d.iteritems()):
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if isinstance(value, dict):
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for subname, subvalue in recursive_keypairs(value):
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yield ('%s:%s' % (name, subname), subvalue)
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else:
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yield name, value
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def compute_signature(message, secret):
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"""Returns the signature for a message dictionary."""
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digest_maker = hmac.new(secret, '', hashlib.sha256)
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for name, value in recursive_keypairs(message):
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if name == 'message_signature':
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continue
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digest_maker.update(name)
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digest_maker.update(unicode(value).encode('utf-8'))
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return digest_maker.hexdigest()
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def append_signature(message, secret):
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"""Sets the message signature key."""
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message['message_signature'] = compute_signature(message, secret)
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def verify_signature(message, secret):
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"""Checks the signature in the message against the value computed from the
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rest of the contents.
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"""
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old_sig = message.get('message_signature')
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new_sig = compute_signature(message, secret)
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return new_sig == old_sig
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