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shakna-israel/test.sh

Created June 28, 2020 18:14
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Predictable Limits on Python's JSON Parser
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test.sh
#!/bin/sh
# Python will hit it's recursion limit
# If you supply just 4 less than the recursion limit
# I assume this means there's a few objects on the call stack first
# Probably: __main__, print, json.loads, and input.
n="$(python3 -c 'import math; import sys; sys.stdout.write(str(math.floor(sys.getrecursionlimit() - 4)))')"
echo "N: $n"
# Obviously invalid, but unparseable without matching pair
# JSON's grammar is... Not good at being partially parsed.
left="$(yes [ | head -n "$n" | tr -d '\n')"
# Rather than exploding with the expected decodeError
# This will explode with a RecursionError
# Which naturally thrashes the memory cache.
echo "$left" | python3 -c 'import json; print(json.loads(input()))'
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