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Denial of service
Suppose a python web server that implements (1) receives a file via HTTP, (2) process
the file, and (3) sends back a reply via HTTP. In order to allow multiple concurrent
users to use the server, the server use a dedicated thread for each HTTP request.
Also, in order to reduce the size of data communicated via network, the server uses a
last generation (I’m kidding) compression technology. A file consists of a list of
substitution rules and a payload. Every line of the file that starts with #is considered a
rule. For instance, the following file
# H = and
# AR = are
# brh = brotherhood
All human beings AR born free H equal in dignity H rights. They
AR endowed with reason H conscience H should act towards one
another in a spirit of brh.

can be decompressed to
All human beings are born free and equal in dignity and rights. They
are endowed with reason and conscience and should act towards one
another in a spirit of brotherhood.

File printer.py implements the function decompress.
This system has a vulnerability. An attacker can send a really small input and force the
server to allocate a large amount of memory. Even worst, in some cases this amount
of memory is unbounded. (Discuss with your colleagues additional problems related to
the usage of one thread per request).
To fix this problem, you must complete the stub in filter.py, which returns True only
for inputs that do not lead to unbound allocation of memory. Your filter will be used in
the server to discard malicious requests.

To test your solution execute ./test.py or py.test test.py.
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Page Count                      : 1
Title                           : Microsoft Word - Document3
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Creator                         : Word
Create Date                     : 2018:11:19 16:17:02Z
Modify Date                     : 2018:11:19 16:17:02Z
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