AKP分析（基于取证）

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原创 2023-08-14 22:53:28 1.8k 阅读 AI 写同款· GEO 优化 ›

【胖虎的逆向之路】03——Android一代壳脱壳办法罗列&实操在上文中，我们讲解了关于Android整体加壳的原理和实际操作，现在我们来针对目前主流的脱壳工具以及流程进行讲解，由于作者能力有限，会尽力的详细描述整体壳脱壳提示：以下是本篇文章正文内容，下面案例可供参考本文总结了当下dex整体加壳的常用的一些脱壳方案，并进行复现，但是在这里仅作为实验加深自己的理解为主（目前也不会这么简单的就可以拿到源Dex）但是有兴趣的朋友可以像我一样去把整个流程走一遍，加深自己的理解~ 阅读详情

APP基础

格式：

*.IPA IOS系统的app文件格式

*.APK 安卓系统的app文件格式

APK静态分析

加固（壳）：

目的：

防止APK被逆向，防篡改，实现数据保护

种类：

APK加壳的中了非常多，我在取证过程中所见到的加壳种类有UPX和pyintaller的加壳方式

脱壳：

一般我们用雷电挂载APK时可以直接使用雷电自带的脱壳来脱壳之后反编译。但是有些恶意文件不能用雷电来挂载，这个时候我们就要手动查壳

查壳工具：

Detect It Easy3.7(之前老的版本可能查不到pyinstaller这个加壳方式)

PEiD:偶尔用，效果不是很好

当然可以用沙箱的方法看一下他是不是有壳

脱壳工具：

知道是什么壳加固了的话，就可以对症下药了

如果是UPX壳的话就用UPX tool来脱

或者360壳，使用取证工具来脱

如果是pyinstaller壳的话用脚本来脱，将脚本和恶意文件放到一个文件夹下面，用cmd跑，会得到一个文件夹，文件夹里的文件不带pyc后缀，要自己加上，然后这些文件也缺少文件头，还要自己补充

然后可以使用在线pyc反编译

pyc反编译 - 爱资料工具 (toolnb.com)

"""
PyInstaller Extractor v1.9 (Supports pyinstaller 3.3, 3.2, 3.1, 3.0, 2.1, 2.0)
Author : Extreme Coders
E-mail : extremecoders(at)hotmail(dot)com
Web    : https://0xec.blogspot.com
Date   : 29-November-2017
Url    : https://sourceforge.net/projects/pyinstallerextractor/

For any suggestions, leave a comment on
https://forum.tuts4you.com/topic/34455-pyinstaller-extractor/

This script extracts a pyinstaller generated executable file.
Pyinstaller installation is not needed. The script has it all.

For best results, it is recommended to run this script in the
same version of python as was used to create the executable.
This is just to prevent unmarshalling errors(if any) while
extracting the PYZ archive.

Usage : Just copy this script to the directory where your exe resides
        and run the script with the exe file name as a parameter

C:\path\to\exe\>python pyinstxtractor.py <filename>
$ /path/to/exe/python pyinstxtractor.py <filename>

Licensed under GNU General Public License (GPL) v3.
You are free to modify this source.

CHANGELOG
================================================

Version 1.1 (Jan 28, 2014)
-------------------------------------------------
- First Release
- Supports only pyinstaller 2.0

Version 1.2 (Sept 12, 2015)
-------------------------------------------------
- Added support for pyinstaller 2.1 and 3.0 dev
- Cleaned up code
- Script is now more verbose
- Executable extracted within a dedicated sub-directory

(Support for pyinstaller 3.0 dev is experimental)

Version 1.3 (Dec 12, 2015)
-------------------------------------------------
- Added support for pyinstaller 3.0 final
- Script is compatible with both python 2.x & 3.x (Thanks to Moritz Kroll @ Avira Operations GmbH & Co. KG)

Version 1.4 (Jan 19, 2016)
-------------------------------------------------
- Fixed a bug when writing pyc files >= version 3.3 (Thanks to Daniello Alto: https://github.com/Djamana)

Version 1.5 (March 1, 2016)
-------------------------------------------------
- Added support for pyinstaller 3.1 (Thanks to Berwyn Hoyt for reporting)

Version 1.6 (Sept 5, 2016)
-------------------------------------------------
- Added support for pyinstaller 3.2
- Extractor will use a random name while extracting unnamed files.
- For encrypted pyz archives it will dump the contents as is. Previously, the tool would fail.

Version 1.7 (March 13, 2017)
-------------------------------------------------
- Made the script compatible with python 2.6 (Thanks to Ross for reporting)

Version 1.8 (April 28, 2017)
-------------------------------------------------
- Support for sub-directories in .pyz files (Thanks to Moritz Kroll @ Avira Operations GmbH & Co. KG)

Version 1.9 (November 29, 2017)
-------------------------------------------------
- Added support for pyinstaller 3.3
- Display the scripts which are run at entry (Thanks to Michael Gillespie @ malwarehunterteam for the feature request)

"""

from __future__ import print_function
import os
import struct
import marshal
import zlib
import sys
import imp
import types
from uuid import uuid4 as uniquename


class CTOCEntry:
    def __init__(self, position, cmprsdDataSize, uncmprsdDataSize, cmprsFlag, typeCmprsData, name):
        self.position = position
        self.cmprsdDataSize = cmprsdDataSize
        self.uncmprsdDataSize = uncmprsdDataSize
        self.cmprsFlag = cmprsFlag
        self.typeCmprsData = typeCmprsData
        self.name = name


class PyInstArchive:
    PYINST20_COOKIE_SIZE = 24           # For pyinstaller 2.0
    PYINST21_COOKIE_SIZE = 24 + 64      # For pyinstaller 2.1+
    MAGIC = b'MEI\014\013\012\013\016'  # Magic number which identifies pyinstaller

    def __init__(self, path):
        self.filePath = path


    def open(self):
        try:
            self.fPtr = open(self.filePath, 'rb')
            self.fileSize = os.stat(self.filePath).st_size
        except:
            print('[*] Error: Could not open {0}'.format(self.filePath))
            return False
        return True


    def close(self):
        try:
            self.fPtr.close()
        except:
            pass


    def checkFile(self):
        print('[*] Processing {0}'.format(self.filePath))
        # Check if it is a 2.0 archive
        self.fPtr.seek(self.fileSize - self.PYINST20_COOKIE_SIZE, os.SEEK_SET)
        magicFromFile = self.fPtr.read(len(self.MAGIC))

        if magicFromFile == self.MAGIC:
            self.pyinstVer = 20     # pyinstaller 2.0
            print('[*] Pyinstaller version: 2.0')
            return True

        # Check for pyinstaller 2.1+ before bailing out
        self.fPtr.seek(self.fileSize - self.PYINST21_COOKIE_SIZE, os.SEEK_SET)
        magicFromFile = self.fPtr.read(len(self.MAGIC))

        if magicFromFile == self.MAGIC:
            print('[*] Pyinstaller version: 2.1+')
            self.pyinstVer = 21     # pyinstaller 2.1+
            return True

        print('[*] Error : Unsupported pyinstaller version or not a pyinstaller archive')
        return False


    def getCArchiveInfo(self):
        try:
            if self.pyinstVer == 20:
                self.fPtr.seek(self.fileSize - self.PYINST20_COOKIE_SIZE, os.SEEK_SET)

                # Read CArchive cookie
                (magic, lengthofPackage, toc, tocLen, self.pyver) = \
                struct.unpack('!8siiii', self.fPtr.read(self.PYINST20_COOKIE_SIZE))

            elif self.pyinstVer == 21:
                self.fPtr.seek(self.fileSize - self.PYINST21_COOKIE_SIZE, os.SEEK_SET)

                # Read CArchive cookie
                (magic, lengthofPackage, toc, tocLen, self.pyver, pylibname) = \
                struct.unpack('!8siiii64s', self.fPtr.read(self.PYINST21_COOKIE_SIZE))

        except:
            print('[*] Error : The file is not a pyinstaller archive')
            return False

        print('[*] Python version: {0}'.format(self.pyver))

        # Overlay is the data appended at the end of the PE
        self.overlaySize = lengthofPackage
        self.overlayPos = self.fileSize - self.overlaySize
        self.tableOfContentsPos = self.overlayPos + toc
        self.tableOfContentsSize = tocLen

        print('[*] Length of package: {0} bytes'.format(self.overlaySize))
        return True


    def parseTOC(self):
        # Go to the table of contents
        self.fPtr.seek(self.tableOfContentsPos, os.SEEK_SET)

        self.tocList = []
        parsedLen = 0

        # Parse table of contents
        while parsedLen < self.tableOfContentsSize:
            (entrySize, ) = struct.unpack('!i', self.fPtr.read(4))
            nameLen = struct.calcsize('!iiiiBc')

            (entryPos, cmprsdDataSize, uncmprsdDataSize, cmprsFlag, typeCmprsData, name) = \
            struct.unpack( \
                '!iiiBc{0}s'.format(entrySize - nameLen), \
                self.fPtr.read(entrySize - 4))

            name = name.decode('utf-8').rstrip('\0')
            if len(name) == 0:
                name = str(uniquename())
                print('[!] Warning: Found an unamed file in CArchive. Using random name {0}'.format(name))

            self.tocList.append( \
                                CTOCEntry(                      \
                                    self.overlayPos + entryPos, \
                                    cmprsdDataSize,             \
                                    uncmprsdDataSize,           \
                                    cmprsFlag,                  \
                                    typeCmprsData,              \
                                    name                        \
                                ))

            parsedLen += entrySize
        print('[*] Found {0} files in CArchive'.format(len(self.tocList)))



    def extractFiles(self):
        print('[*] Beginning extraction...please standby')
        extractionDir = os.path.join(os.getcwd(), os.path.basename(self.filePath) + '_extracted')

        if not os.path.exists(extractionDir):
            os.mkdir(extractionDir)

        os.chdir(extractionDir)

        for entry in self.tocList:
            basePath = os.path.dirname(entry.name)
            if basePath != '':
                # Check if path exists, create if not
                if not os.path.exists(basePath):
                    os.makedirs(basePath)

            self.fPtr.seek(entry.position, os.SEEK_SET)
            data = self.fPtr.read(entry.cmprsdDataSize)

            if entry.cmprsFlag == 1:
                data = zlib.decompress(data)
                # Malware may tamper with the uncompressed size
                # Comment out the assertion in such a case
                assert len(data) == entry.uncmprsdDataSize # Sanity Check

            with open(entry.name, 'wb') as f:
                f.write(data)

            if entry.typeCmprsData == b's':
                print('[+] Possible entry point: {0}'.format(entry.name))

            elif entry.typeCmprsData == b'z' or entry.typeCmprsData == b'Z':
                self._extractPyz(entry.name)


    def _extractPyz(self, name):
        dirName =  name + '_extracted'
        # Create a directory for the contents of the pyz
        if not os.path.exists(dirName):
            os.mkdir(dirName)

        with open(name, 'rb') as f:
            pyzMagic = f.read(4)
            assert pyzMagic == b'PYZ\0' # Sanity Check

            pycHeader = f.read(4) # Python magic value

            if imp.get_magic() != pycHeader:
                print('[!] Warning: The script is running in a different python version than the one used to build the executable')
                print('    Run this script in Python{0} to prevent extraction errors(if any) during unmarshalling'.format(self.pyver))

            (tocPosition, ) = struct.unpack('!i', f.read(4))
            f.seek(tocPosition, os.SEEK_SET)

            try:
                toc = marshal.load(f)
            except:
                print('[!] Unmarshalling FAILED. Cannot extract {0}. Extracting remaining files.'.format(name))
                return

            print('[*] Found {0} files in PYZ archive'.format(len(toc)))

            # From pyinstaller 3.1+ toc is a list of tuples
            if type(toc) == list:
                toc = dict(toc)

            for key in toc.keys():
                (ispkg, pos, length) = toc[key]
                f.seek(pos, os.SEEK_SET)

                fileName = key
                try:
                    # for Python > 3.3 some keys are bytes object some are str object
                    fileName = key.decode('utf-8')
                except:
                    pass

                # Make sure destination directory exists, ensuring we keep inside dirName
                destName = os.path.join(dirName, fileName.replace("..", "__"))
                destDirName = os.path.dirname(destName)
                if not os.path.exists(destDirName):
                    os.makedirs(destDirName)

                try:
                    data = f.read(length)
                    data = zlib.decompress(data)
                except:
                    print('[!] Error: Failed to decompress {0}, probably encrypted. Extracting as is.'.format(fileName))
                    open(destName + '.pyc.encrypted', 'wb').write(data)
                    continue

                with open(destName + '.pyc', 'wb') as pycFile:
                    pycFile.write(pycHeader)      # Write pyc magic
                    pycFile.write(b'\0' * 4)      # Write timestamp
                    if self.pyver >= 33:
                        pycFile.write(b'\0' * 4)  # Size parameter added in Python 3.3
                    pycFile.write(data)


def main():
    if len(sys.argv) < 2:
        print('[*] Usage: pyinstxtractor.py <filename>')

    else:
        arch = PyInstArchive(sys.argv[1])
        if arch.open():
            if arch.checkFile():
                if arch.getCArchiveInfo():
                    arch.parseTOC()
                    arch.extractFiles()
                    arch.close()
                    print('[*] Successfully extracted pyinstaller archive: {0}'.format(sys.argv[1]))
                    print('')
                    print('You can now use a python decompiler on the pyc files within the extracted directory')
                    return

            arch.close()


if __name__ == '__main__':
    main()