Errors in Python Code

[vietwow]

Dear all,

I often use online tool http://utilitymill.com/utility/pyc_xray to decompile binary python code, it works well. So I want to view its code, I click "Edit & View Source", it give me the code :


#Mostly from the code here http://nedbatchelder.com/blog/200804/the_structure_of_pyc_files.html

import dis, marshal, struct, sys, time, types

def show_file(f):
magic = f.read(4)
moddate = f.read(4)
modtime = time.asctime(time.localtime(struct.unpack('L', moddate)[0]))
print "magic %s" % (magic.encode('hex'))
print "moddate %s (%s)" % (moddate.encode('hex'), modtime)
code = marshal.loads(f.read())
show_code(code)

def show_code(code, indent=''):
print "%scode" % indent
indent += ' '
print "%sargcount %d" % (indent, code.co_argcount)
print "%snlocals %d" % (indent, code.co_nlocals)
print "%sstacksize %d" % (indent, code.co_stacksize)
print "%sflags %04x" % (indent, code.co_flags)
show_hex("code", code.co_code, indent=indent)
dis.disassemble(code)
print "%sconsts" % indent
for const in code.co_consts:
if type(const) == types.CodeType:
show_code(const, indent+' ')
else:
print " %s%r" % (indent, const)
print "%snames %r" % (indent, code.co_names)
print "%svarnames %r" % (indent, code.co_varnames)
print "%sfreevars %r" % (indent, code.co_freevars)
print "%scellvars %r" % (indent, code.co_cellvars)
print "%sfilename %r" % (indent, code.co_filename)
print "%sname %r" % (indent, code.co_name)
print "%sfirstlineno %d" % (indent, code.co_firstlineno)
show_hex("lnotab", code.co_lnotab, indent=indent)

def show_hex(label, h, indent):
h = h.encode('hex')
if len(h) < 60:
print "%s%s %s" % (indent, label, h)
else:
print "%s%s" % (indent, label)
for i in range(0, len(h), 60):
print "%s %s" % (indent, h[i:i+60])

#Main utility code
from cStringIO import StringIO
f=StringIO(PYC)
show_file(f)

But when I run it on CentOS 5 :


[root@server ~]# ./dis.py
Traceback (most recent call last):
File "./dis.py", line 3, in <module>
import dis, marshal, struct, sys, time, types
File "/root/dis.py", line 49, in <module>
f=StringIO(PYC)
NameError: name 'PYC' is not defined


Can u help me to find out the reason ?

Thanx

[$USER]

I am currently trying to learn python, So I don't really understand much of the code. But I think it is trying to import itself. Maybe thats normal, but seems wierd to me. You are running dis.py and it is trying to import dis.py. I dunno. good luck though.

[vietwow]

I have tried change script's name, still error :


[root@server ~]# mv dis.py asm.py

[root@server ~]# ./asm.py crackme.pyc
Traceback (most recent call last):
File "./asm.py", line 3, in <module>
import dis, marshal, struct, sys, time, types
File "/usr/local/python/lib/python2.5/dis.py", line 49, in <module>

NameError: name 'PYC' is not defined

[MrStill]

I am rusty with python; but, I will venture a guess if you don't mind.

You have 'PYC' is being passed as a variable to a function without any prior mention of that variable. If you are writing/reading a file called 'PYC' then you may try passing PYC as a string or a string containing the value 'PYC'. As I said, I am not up to speed with python; however, most programming languages, even loosely typed similarly to Python, would want some initialization of a variable before passing to a function.

A good tip is to check docs provided by the people who maintain the language. Python seems to have good documentation on their website. Check the two links below to see if they provide better understanding.

http://docs.python.org/library/stringio.html
http://effbot.org/librarybook/cstringio.html

I hope this helps. I'm sorry if I am telling you stuff you already know

[unutbu]

Change


from cStringIO import StringIO
f=StringIO(PYC)

to


import sys
f=open(sys.argv[1],'r')

Then run the script like this:


./asm.py file.pyc