Created
April 11, 2015 12:55
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hmac pickle
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#!/usr/bin/env python | |
"""Check the digests of pickles passed through a stream. | |
""" | |
#end_pymotw_header | |
import hashlib | |
import hmac | |
try: | |
import cPickle as pickle | |
except: | |
import pickle | |
import pprint | |
from StringIO import StringIO | |
def make_digest(message): | |
"Return a digest for the message." | |
hash = hmac.new('secret-shared-key-goes-here', | |
message, | |
hashlib.sha1) | |
return hash.hexdigest() | |
class SimpleObject(object): | |
"""A very simple class to demonstrate checking digests before | |
unpickling. | |
""" | |
def __init__(self, name): | |
self.name = name | |
def __str__(self): | |
return self.name | |
# Simulate a writable socket or pipe with StringIO | |
out_s = StringIO() | |
# Write a valid object to the stream: | |
# digest\nlength\npickle | |
o = SimpleObject('digest matches') | |
pickled_data = pickle.dumps(o) | |
digest = make_digest(pickled_data) | |
header = '%s %s' % (digest, len(pickled_data)) | |
print 'WRITING:', header | |
out_s.write(header + '\n') | |
out_s.write(pickled_data) | |
# Write an invalid object to the stream | |
o = SimpleObject('digest does not match') | |
pickled_data = pickle.dumps(o) | |
digest = make_digest('not the pickled data at all') | |
header = '%s %s' % (digest, len(pickled_data)) | |
print '\nWRITING:', header | |
out_s.write(header + '\n') | |
out_s.write(pickled_data) | |
out_s.flush() | |
# Simulate a readable socket or pipe with StringIO | |
in_s = StringIO(out_s.getvalue()) | |
# Read the data | |
while True: | |
first_line = in_s.readline() | |
if not first_line: | |
break | |
incoming_digest, incoming_length = first_line.split(' ') | |
incoming_length = int(incoming_length) | |
print '\nREAD:', incoming_digest, incoming_length | |
incoming_pickled_data = in_s.read(incoming_length) | |
actual_digest = make_digest(incoming_pickled_data) | |
print 'ACTUAL:', actual_digest | |
if incoming_digest != actual_digest: | |
print 'WARNING: Data corruption' | |
else: | |
obj = pickle.loads(incoming_pickled_data) | |
print 'OK:', obj | |
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