前回はpycを低レベルな命令に変換して読む方法を説明した．
あれはあれで読めはするが，アセンブリ言語と同様の読みづらさはある．
今回は直接pycをpythonのスクリプトまで変換する方法を紹介する．
変換するライブラリは複数あるが，ここでは uncompyleを使った．
結論として，精度はいい感じ．pycにソース保護を期待するのはやめましょう．

uncompyle

python byte-code decompiler．
uncompyle2とuncompyle6がある．
前者は2系サポート，後者は2・3系両方で使える．

環境

各種バージョン

以下のとおり．

$ uname -a
 Linux poppycompass 4.18.6-arch1-1-ARCH #1 SMP PREEMPT Wed Sep 5 11:54:09 UTC 2018 x86_64 GNU/Linux

$ python2
Python 2.7.15 (default, Jun 27 2018, 13:05:28)
[GCC 8.1.1 20180531] on linux2

Arch Linuxの64ビット版．
つまりただのLinux，pythonは2系．

環境作成

$ virtualenv2 ENV
$ . ENV/bin/activate
$ pip install uncompyle

サンプル

単純なやつ

適当に組んだ．

# sample.py
import string

def add(a, b):
    return a+b

a = "abc"
b = "def"
c = "ghi"

d = a + b + c

sum = 0
for i in range(100):
    sum += 0

add(1,2)

pycを生成して，戻してみる．

$ python2 -m compileall sample.py # pyc生成
Compiling sample.py ...

$ ENV/bin/uncompyle6 ./sample.pyc # uncompyleで変換
# uncompyle6 version 3.2.3
# Python bytecode 2.7 (62211)
# Decompiled from: Python 2.7.15 (default, Jun 27 2018, 13:05:28)
# [GCC 8.1.1 20180531]
# Embedded file name: sample.py
# Compiled at: 2018-09-26 06:49:02
import string

def add(a, b):
    return a + b


a = 'abc'
b = 'def'
c = 'ghi'
d = a + b + c
sum = 0
for i in range(100):
    sum += 0

add(1, 2)
# okay decompiling ./sample.pyc

見た感じ，完璧に戻されている．

まともなやつ

簡単なやつだけじゃつまらないから，Oxyry Python Obfuscatorから取ってきたNQueensで試してみる．
オリジナルコードは以下．

__all__ = []

class NQueens:
    """Generate all valid solutions for the n queens puzzle"""
    
    def __init__(self, size):
        # Store the puzzle (problem) size and the number of valid solutions
        self.__size = size
        self.__solutions = 0
        self.__solve()

    def __solve(self):
        """Solve the n queens puzzle and print the number of solutions"""
        positions = [-1] * self.__size
        self.__put_queen(positions, 0)
        print("Found", self.__solutions, "solutions.")

    def __put_queen(self, positions, target_row):
        """
        Try to place a queen on target_row by checking all N possible cases.
        If a valid place is found the function calls itself trying to place a queen
        on the next row until all N queens are placed on the NxN board.
        """
        # Base (stop) case - all N rows are occupied
        if target_row == self.__size:
            self.__show_full_board(positions)
            self.__solutions += 1
        else:
            # For all N columns positions try to place a queen
            for column in range(self.__size):
                # Reject all invalid positions
                if self.__check_place(positions, target_row, column):
                    positions[target_row] = column
                    self.__put_queen(positions, target_row + 1)


    def __check_place(self, positions, ocuppied_rows, column):
        """
        Check if a given position is under attack from any of
        the previously placed queens (check column and diagonal positions)
        """
        for i in range(ocuppied_rows):
            if positions[i] == column or \
                positions[i] - i == column - ocuppied_rows or \
                positions[i] + i == column + ocuppied_rows:

                return False
        return True

    def __show_full_board(self, positions):
        """Show the full NxN board"""
        for row in range(self.__size):
            line = ""
            for column in range(self.__size):
                if positions[row] == column:
                    line += "Q "
                else:
                    line += ". "
            print(line)
        print("\n")

    def __show_short_board(self, positions):
        """
        Show the queens positions on the board in compressed form,
        each number represent the occupied column position in the corresponding row.
        """
        line = ""
        for i in range(self.__size):
            line += str(positions[i]) + " "
        print(line)

def main():
    """Initialize and solve the n queens puzzle"""
    NQueens(8)

if __name__ == "__main__":
    # execute only if run as a script
    main()

戻した結果

__all__ = []

class NQueens:
    """Generate all valid solutions for the n queens puzzle"""

    def __init__(self, size):
        self.__size = size
        self.__solutions = 0
        self.__solve()

    def __solve(self):
        """Solve the n queens puzzle and print the number of solutions"""
        positions = [
         -1] * self.__size
        self.__put_queen(positions, 0)
        print ('Found', self.__solutions, 'solutions.')

    def __put_queen(self, positions, target_row):
        """
        Try to place a queen on target_row by checking all N possible cases.
        If a valid place is found the function calls itself trying to place a queen
        on the next row until all N queens are placed on the NxN board.
        """
        if target_row == self.__size:
            self.__show_full_board(positions)
            self.__solutions += 1
        else:
            for column in range(self.__size):
                if self.__check_place(positions, target_row, column):
                    positions[target_row] = column
                    self.__put_queen(positions, target_row + 1)

    def __check_place(self, positions, ocuppied_rows, column):
        """
        Check if a given position is under attack from any of
        the previously placed queens (check column and diagonal positions)
        """
        for i in range(ocuppied_rows):
            if positions[i] == column or positions[i] - i == column - ocuppied_rows or positions[i] + i == column + ocuppied_rows:
                return False

        return True

    def __show_full_board(self, positions):
        """Show the full NxN board"""
        for row in range(self.__size):
            line = ''
            for column in range(self.__size):
                if positions[row] == column:
                    line += 'Q '
                else:
                    line += '. '

            print line

        print '\n'

    def __show_short_board(self, positions):
        """
        Show the queens positions on the board in compressed form,
        each number represent the occupied column position in the corresponding row.
        """
        line = ''
        for i in range(self.__size):
            line += str(positions[i]) + ' '

        print line


def main():
    """Initialize and solve the n queens puzzle"""
        for i in range(self.__size):
            line += str(positions[i]) + ' '

        print line


def main():
    NQueens(8)


if __name__ == '__main__':
    main()

やはり，記述はほぼ完璧に戻されている．
面白いのは，"""で付けたコメントアウトは復元でき，#で付けたものは復元できなかったこと．
可読性のためにつける\も消える．そりゃそんな情報残すわけ無いか．

難読化すると・・・？

さっきのやつをOxyry Python Obfuscatorで難読化した結果も試してみる．

""#line:4
__all__ =[]#line:6
class O0000OO0000OOO0OO :#line:8
    ""#line:9
    def __init__ (O00OO0O0O0O00OO00 ,O00OO0OO00OOO00OO ):#line:11
        O00OO0O0O0O00OO00 .__OO00OO0OO00OOO00O =O00OO0OO00OOO00OO #line:13
        O00OO0O0O0O00OO00 .__O00OOO00O0O000000 =0 #line:14
        O00OO0O0O0O00OO00 .__O0OO00000O0O0O0O0 ()#line:15
    def __O0OO00000O0O0O0O0 (OOOOO0O00OO0O0O0O ):#line:17
        ""#line:18
        O0OO0000OO0OO0000 =[-1 ]*OOOOO0O00OO0O0O0O .__OO00OO0OO00OOO00O #line:19
        OOOOO0O00OO0O0O0O .__OO0OOOO0000O0O00O (O0OO0000OO0OO0000 ,0 )#line:20
        print ("Found",OOOOO0O00OO0O0O0O .__O00OOO00O0O000000 ,"solutions.")#line:21
    def __OO0OOOO0000O0O00O (O0OO00O0000O000O0 ,O0OOOOO0OOOOO000O ,OO0OOOO00OO00OOO0 ):#line:23
        ""#line:28
        if OO0OOOO00OO00OOO0 ==O0OO00O0000O000O0 .__OO00OO0OO00OOO00O :#line:30
            O0OO00O0000O000O0 .__OOO0OO0O0000O00OO (O0OOOOO0OOOOO000O )#line:31
            O0OO00O0000O000O0 .__O00OOO00O0O000000 +=1 #line:32
        else :#line:33
            for OO000O0OOOOO0O0OO in range (O0OO00O0000O000O0 .__OO00OO0OO00OOO00O ):#line:35
                if O0OO00O0000O000O0 .__O00O0O00000O0O00O (O0OOOOO0OOOOO000O ,OO0OOOO00OO00OOO0 ,OO000O0OOOOO0O0OO ):#line:37
                    O0OOOOO0OOOOO000O [OO0OOOO00OO00OOO0 ]=OO000O0OOOOO0O0OO #line:38
                    O0OO00O0000O000O0 .__OO0OOOO0000O0O00O (O0OOOOO0OOOOO000O ,OO0OOOO00OO00OOO0 +1 )#line:39
    def __O00O0O00000O0O00O (OO0OOO0OOO0O0OO0O ,O00000O0O00OOOOOO ,O00O0O000000OOOOO ,OOOO00OOO000OO0OO ):#line:42
        ""#line:46
        for OOO000O0OO0O00000 in range (O00O0O000000OOOOO ):#line:47
            if O00000O0O00OOOOOO [OOO000O0OO0O00000 ]==OOOO00OOO000OO0OO or O00000O0O00OOOOOO [OOO000O0OO0O00000 ]-OOO000O0OO0O00000 ==OOOO00OOO000OO0OO -O00O0O000000OOOOO or O00000O0O00OOOOOO [OOO000O0OO0O00000 ]+OOO000O0OO0O00000 ==OOOO00OOO000OO0OO +O00O0O000000OOOOO :#line:50
                return False #line:52
        return True #line:53
    def __OOO0OO0O0000O00OO (OOOO0OOO0OOO0OO00 ,OO0OO0O00OOO00OO0 ):#line:55
        ""#line:56
        for O0OOO0O0O0OO00O0O in range (OOOO0OOO0OOO0OO00 .__OO00OO0OO00OOO00O ):#line:57
            OOO00OO0OOOOOOOOO =""#line:58
            for OO00O0O0OOO0O0000 in range (OOOO0OOO0OOO0OO00 .__OO00OO0OO00OOO00O ):#line:59
                if OO0OO0O00OOO00OO0 [O0OOO0O0O0OO00O0O ]==OO00O0O0OOO0O0000 :#line:60
                    OOO00OO0OOOOOOOOO +="Q "#line:61
                else :#line:62
                    OOO00OO0OOOOOOOOO +=". "#line:63
            print (OOO00OO0OOOOOOOOO )#line:64
        print ("\n")#line:65
    def __OO0O00O0O0OOO0OOO (OO0OO000O00O0OO00 ,O00O00O00OO0O0OOO ):#line:67
        ""#line:71
        OOO000OOO00OO0OOO =""#line:72
        for O00OOO000OO0O00OO in range (OO0OO000O00O0OO00 .__OO00OO0OO00OOO00O ):#line:73
            OOO000OOO00OO0OOO +=str (O00O00O00OO0O0OOO [O00OOO000OO0O00OO ])+" "#line:74
        print (OOO000OOO00OO0OOO )#line:75
def OOO0O0OO0OOO000OO ():#line:77
    ""#line:78
    O0000OO0000OOO0OO (8 )#line:79
if __name__ =="__main__":#line:81
    OOO0O0OO0OOO000OO ()#line:83

戻す

__all__ = []

class O0000OO0000OOO0OO:
    """"""

    def __init__(O00OO0O0O0O00OO00, O00OO0OO00OOO00OO):
        O00OO0O0O0O00OO00.__OO00OO0OO00OOO00O = O00OO0OO00OOO00OO
        O00OO0O0O0O00OO00.__O00OOO00O0O000000 = 0
        O00OO0O0O0O00OO00.__O0OO00000O0O0O0O0()

    def __O0OO00000O0O0O0O0(OOOOO0O00OO0O0O0O):
        """"""
        O0OO0000OO0OO0000 = [
         -1] * OOOOO0O00OO0O0O0O.__OO00OO0OO00OOO00O
        OOOOO0O00OO0O0O0O.__OO0OOOO0000O0O00O(O0OO0000OO0OO0000, 0)
        print ('Found', OOOOO0O00OO0O0O0O.__O00OOO00O0O000000, 'solutions.')

    def __OO0OOOO0000O0O00O(O0OO00O0000O000O0, O0OOOOO0OOOOO000O, OO0OOOO00OO00OOO0):
        """"""
        if OO0OOOO00OO00OOO0 == O0OO00O0000O000O0.__OO00OO0OO00OOO00O:
            O0OO00O0000O000O0.__OOO0OO0O0000O00OO(O0OOOOO0OOOOO000O)
            O0OO00O0000O000O0.__O00OOO00O0O000000 += 1
        else:
            for OO000O0OOOOO0O0OO in range(O0OO00O0000O000O0.__OO00OO0OO00OOO00O):
                if O0OO00O0000O000O0.__O00O0O00000O0O00O(O0OOOOO0OOOOO000O, OO0OOOO00OO00OOO0, OO000O0OOOOO0O0OO):
                    O0OOOOO0OOOOO000O[OO0OOOO00OO00OOO0] = OO000O0OOOOO0O0OO
                    O0OO00O0000O000O0.__OO0OOOO0000O0O00O(O0OOOOO0OOOOO000O, OO0OOOO00OO00OOO0 + 1)

    def __O00O0O00000O0O00O(OO0OOO0OOO0O0OO0O, O00000O0O00OOOOOO, O00O0O000000OOOOO, OOOO00OOO000OO0OO):
        """"""
        for OOO000O0OO0O00000 in range(O00O0O000000OOOOO):
            if O00000O0O00OOOOOO[OOO000O0OO0O00000] == OOOO00OOO000OO0OO or O00000O0O00OOOOOO[OOO000O0OO0O00000] - OOO000O0OO0O00000 ==
OOOO00OOO000OO0OO - O00O0O000000OOOOO or O00000O0O00OOOOOO[OOO000O0OO0O00000] + OOO000O0OO0O00000 == OOOO00OOO000OO0OO + O00O0O000000OOO
OO:
                return False

        return True

    def __OOO0OO0O0000O00OO(OOOO0OOO0OOO0OO00, OO0OO0O00OOO00OO0):
        """"""
        for O0OOO0O0O0OO00O0O in range(OOOO0OOO0OOO0OO00.__OO00OO0OO00OOO00O):
            OOO00OO0OOOOOOOOO = ''
            for OO00O0O0OOO0O0000 in range(OOOO0OOO0OOO0OO00.__OO00OO0OO00OOO00O):
                if OO0OO0O00OOO00OO0[O0OOO0O0O0OO00O0O] == OO00O0O0OOO0O0000:
                    OOO00OO0OOOOOOOOO += 'Q '
                else:
                    OOO00OO0OOOOOOOOO += '. '

            print OOO00OO0OOOOOOOOO

        print '\n'

    def __OO0O00O0O0OOO0OOO(OO0OO000O00O0OO00, O00O00O00OO0O0OOO):
        """"""
        OOO000OOO00OO0OOO = ''
        for O00OOO000OO0O00OO in range(OO0OO000O00O0OO00.__OO00OO0OO00OOO00O):
            OOO000OOO00OO0OOO += str(O00O00O00OO0O0OOO[O00OOO000OO0O00OO]) + ' '

        print OOO000OOO00OO0OOO


def OOO0O0OO0OOO000OO():
    """"""


def OOO0O0OO0OOO000OO():
    """"""
    O0000OO0000OOO0OO(8)


if __name__ == '__main__':
    OOO0O0OO0OOO000OO()

まあ，やっぱりしっかりと戻された．