mitmproxy/libmproxy/contrib/jsbeautifier/unpackers/evalbased.py

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#
# Unpacker for eval() based packers, a part of javascript beautifier
# by Einar Lielmanis <einar@jsbeautifier.org>
#
# written by Stefano Sanfilippo <a.little.coder@gmail.com>
#
# usage:
#
# if detect(some_string):
# unpacked = unpack(some_string)
#
"""Unpacker for eval() based packers: runs JS code and returns result.
Works only if a JS interpreter (e.g. Mozilla's Rhino) is installed and
properly set up on host."""
from subprocess import PIPE, Popen
PRIORITY = 3
def detect(source):
"""Detects if source is likely to be eval() packed."""
return source.strip().lower().startswith('eval(function(')
def unpack(source):
"""Runs source and return resulting code."""
return jseval('print %s;' % source[4:]) if detect(source) else source
# In case of failure, we'll just return the original, without crashing on user.
def jseval(script):
"""Run code in the JS interpreter and return output."""
try:
interpreter = Popen(['js'], stdin=PIPE, stdout=PIPE)
except OSError:
return script
result, errors = interpreter.communicate(script)
if interpreter.poll() or errors:
return script
return result