First commit!

.gitignore

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+# Byte-compiled / optimized / DLL files
+__pycache__/
+*.py[cod]
+*$py.class
+data/
+
+# C extensions
+*.so
+
+# Distribution / packaging
+.Python
+build/
+develop-eggs/
+dist/
+downloads/
+eggs/
+.eggs/
+lib/
+lib64/
+parts/
+sdist/
+var/
+wheels/
+pip-wheel-metadata/
+share/python-wheels/
+*.egg-info/
+.installed.cfg
+*.egg
+MANIFEST
+
+# PyInstaller
+#  Usually these files are written by a python script from a template
+#  before PyInstaller builds the exe, so as to inject date/other infos into it.
+*.manifest
+*.spec
+
+# Installer logs
+pip-log.txt
+pip-delete-this-directory.txt
+
+# Unit test / coverage reports
+htmlcov/
+.tox/
+.nox/
+.coverage
+.coverage.*
+.cache
+nosetests.xml
+coverage.xml
+*.cover
+*.py,cover
+.hypothesis/
+.pytest_cache/
+
+# Translations
+*.mo
+*.pot
+
+# Django stuff:
+*.log
+local_settings.py
+db.sqlite3
+db.sqlite3-journal
+
+# Flask stuff:
+instance/
+.webassets-cache
+
+# Scrapy stuff:
+.scrapy
+
+# Sphinx documentation
+docs/_build/
+
+# PyBuilder
+target/
+
+# Jupyter Notebook
+.ipynb_checkpoints
+
+# IPython
+profile_default/
+ipython_config.py
+
+# pyenv
+.python-version
+
+# pipenv
+#   According to pypa/pipenv#598, it is recommended to include Pipfile.lock in version control.
+#   However, in case of collaboration, if having platform-specific dependencies or dependencies
+#   having no cross-platform support, pipenv may install dependencies that don't work, or not
+#   install all needed dependencies.
+#Pipfile.lock
+
+# PEP 582; used by e.g. github.com/David-OConnor/pyflow
+__pypackages__/
+
+# Celery stuff
+celerybeat-schedule
+celerybeat.pid
+
+# SageMath parsed files
+*.sage.py
+
+# Environments
+.env
+.venv
+env/
+venv/
+ENV/
+env.bak/
+venv.bak/
+
+# Spyder project settings
+.spyderproject
+.spyproject
+
+# Rope project settings
+.ropeproject
+
+# mkdocs documentation
+/site
+
+# mypy
+.mypy_cache/
+.dmypy.json
+dmypy.json
+
+# Pyre type checker
+.pyre/
+/.idea/
+/tmp.ps1
+/tmp.xml

LICENSE

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+MIT License
+
+Copyright (c) 2020 thewhiteninja
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

README.md

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+# DeobShell
+
+[![GitHub license](https://img.shields.io/badge/license-MIT-blue.svg)](LICENSE.MIT)
+[![Language: Python](https://img.shields.io/badge/Language-Python-brightgreen.svg?tyle=flat-square)](#)
+[![Cross-platform](https://img.shields.io/badge/Platform-All-0078d7.svg)](#)
+[![v1.0](https://img.shields.io/badge/Version-1.0-ff5733.svg)](#)
+
+<br />
+
+DeobShell is PoC to deobfuscate Powershell using Abstract Syntax Tree (AST) manipulation in Python.
+The AST is extracted using a Powershell script by calling `System.Management.Automation.Language.Parser` and
+writing relevant nodes to an XML file.
+
+AST manipulation and optimization is based on a set of rules (ex: concat constant string, apply format operator ...).
+
+From the deobfuscated AST, a ps1 script is rebuilt using Python.
+See the diagram below.
+
+*It's a PoC ... only a subset of Powershell is supported*
+
+## How
+
+<p align="center">
+  <img alt="diagram" src="assets/diagram.png" width="600">
+</p>
+
+### Example of rules
+
+- Format
+
+#### In
+```xml
+<BinaryExpressionAst Operator="Format" StaticType="System.Object">
+    <StringConstantExpressionAst StringConstantType="DoubleQuoted" StaticType="string">{0}{1}</StringConstantExpressionAst>
+        <ArrayLiteralAst StaticType="System.Object[]">
+          <Elements>
+            <StringConstantExpressionAst StringConstantType="SingleQuoted" StaticType="string">c</StringConstantExpressionAst>
+            <StringConstantExpressionAst StringConstantType="SingleQuoted" StaticType="string">AcA</StringConstantExpressionAst>
+          </Elements>
+  </ArrayLiteralAst>
+</BinaryExpressionAst>
+```
+#### Out
+```xml
+<StringConstantExpressionAst StringConstantType="SingleQuoted" StaticType="string">cAcA</StringConstantExpressionAst>
+```
+
+### Examples of script
+
+- a CTF chall
+
+#### In
+
+```powershell
+$mRSp73  =  [ChaR[] ]" ))43]raHc[]gNIRtS[,)38]raHc[+98]raHc[+611]raHc[((eCAlper.)421]raHc[]gNIRtS[,'5IP'(eCAlper.)'$',)09]raHc[+99]raHc[+701]raHc[((eCAlper.)93]raHc[]gNIRtS[,'vzW'(eCAlper.)'
+
+
+2halB.tcejboZck tuptuO-etirW
+
+7halB.tcejboZck +'+' 6halB.tcejboZck + halB.tc'+'ejboZck '+'= 2galFFT'+'C:'+'vneZck
+
+SYt!eciNSYt = 1galFFTC:vneZck
+
+SYt...aedi dab yre'+'v'+' ,yre'+'v a yllacipyt svzWtaht ,ton fI .ti gninnur erofeb siht detacsufbo-ed uoy epoh ISYt eulaV- 2halB emaN- '+'ytreporPetoN epy'+'TrebmeM- rebmeM-ddA 5IP tcejboZck
+
+SYt'+'.uoy tresed dna dnuora nur annog reveNSYt eulaV- 9hal'+'B emaN- ytreporPetoN epyTrebmeM- rebmeM-ddA 5'+'IP tcejboZck
+
+SYt.nwod uo'+'y tel annog '+'re'+'veN .'+'pu uoy evig annog reveNSYt eulaV- 8halB emaN- ytreporPetoN epyTrebm'+'eM- rebmeM-d'+'dA 5IP tcejboZck
+
+SYt}f1j9kdSYt eulaV- 7halB emaN- y'+'treporPetoN ep'+'yTrebmeM- rebmeM-ddA 5IP tcejboZck
+
+SYtg4lf_3ht_t0nSYt eulaV- 4halB emaN- yt'+'reporPetoN epyTrebmeM- rebmeM-ddA 5IP tcejboZck
+
+SYt1#f!J{SYt eulaV- 6halB emaN- ytreporPetoN epyTrebmeM- rebmeM-'+'ddA 5IP tcejboZck
+
+SYtgalF,ehT,toN,oslASYt eulaV- 5halB emaN- ytreporPetoN epyTrebmeM- rebmeM-ddA 5IP tcejboZck
+
+SY'+'t}fdjfkslfdSYt eulaV- 3halB emaN- ytrepor'+'PetoN e'+'pyTrebmeM- rebmeM-ddA 5IP tcejboZ'+'ck
+
+SYtgalfSYt eulaV- halB em'+'aN- ytreporPetoN e'+'pyTrebmeM- rebmeM-ddA 5IP tcej'+'boZck
+
+tc'+'ejbO'+'SP tcejbO-weN = tc'+'ejboZck'( ()''nioJ-'x'+]3,1[)eCNERefErpESoBreV$]GniRTS[( (. " ;[aRRAy]::REVerse($MrSp73);. ( 'IeX') ( -JoiN$MrSp73)
+```
+
+#### Out
+
+```powershell
+$object = New-Object PSObject;
+$object | Add-Member  NoteProperty  Blah  "flag";
+$object | Add-Member  NoteProperty  Blah3  "dflskfjdf}";
+$object | Add-Member  NoteProperty  Blah5  "Also,Not,The,Flag";
+$object | Add-Member  NoteProperty  Blah6  "{J!f`#1";
+$object | Add-Member  NoteProperty  Blah4  "n0t_th3_fl4g";
+$object | Add-Member  NoteProperty  Blah7  "dk9j1f}";
+$object | Add-Member  NoteProperty  Blah8  "Never gonna give you up. Never gonna let you down.";
+$object | Add-Member  NoteProperty  Blah9  "Never gonna run around and desert you.";
+$object | Add-Member  NoteProperty  Blah2  "I hope you de-obfuscated this before running it. If not, that''s typically a very, very bad idea...";
+$env:CTFFlag1 = "Nice!";
+$env:CTFFlag2 = $object.Blah + $object.Blah6 + $object.Blah7;
+Write-Output $object.Blah2;
+```
+
+### References 
+
+- https://github.com/R3MRUM/PSDecode
+- https://robwillis.info/2020/08/invoke-decoder-a-powershell-script-to-decode-deobfuscate-malware-samples/
+- https://www.varonis.com/blog/adventures-malware-free-hacking-part-ii/
+- https://gist.github.com/notdodo/3d5ac56cd837c3f79d2c687f3e75cac1

main.py

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+# coding=utf-8
+import os
+import pathlib
+import sys
+
+from modules.ast import create_ast_file, read_ast_file
+from modules.logger import set_log_level, LogLevel
+from modules.optimize import Optimizer
+from modules.rebuilder import Rebuilder
+from modules.utils import welcome
+
+OPTIONS = {}
+
+
+def usage():
+    print("Usage: " + os.path.basename(sys.argv[0]) + ' [options]')
+    print()
+    print("Command:")
+    print("      deob            : Optimize PowerShell AST")
+    print()
+    print("Options:")
+    print("      -h, --help      : Show help")
+    print()
+    sys.exit(0)
+
+
+def parse_args():
+    global OPTIONS
+    i = 1
+    while i < len(sys.argv):
+        if sys.argv[i] in ["-h", "--help"]:
+            usage()
+        elif sys.argv[i] in ["-a", "--ast"]:
+            OPTIONS["input"] = sys.argv[i + 1]
+            i += 1
+        else:
+            OPTIONS["command"] = sys.argv[i]
+        i += 1
+
+
+def deob(ps1_file):
+    p = pathlib.Path(ps1_file)
+
+    if create_ast_file(p):
+
+        if ast := read_ast_file(p.with_suffix(".xml")):
+
+            o = Optimizer()
+            o.optimize(ast)
+
+            with open(p.with_suffix(".deob.xml"), "wb") as output:
+                ast.write(output)
+
+            r = Rebuilder(p.with_suffix(".deob.ps1"))
+            r.rebuild(ast.getroot())
+
+
+def main():
+    if OPTIONS.setdefault("command", None) == "deob":
+        deob(OPTIONS['input'])
+    else:
+        usage()
+
+
+if __name__ == '__main__':
+    welcome()
+    set_log_level(LogLevel.DEBUG)
+    parse_args()
+    main()

modules/__init__.py

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+# coding=utf-8

modules/ast.py

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+# coding=utf-8
+import os
+import subprocess
+# noinspection PyPep8Naming
+import xml.etree.ElementTree as ET
+
+from modules.logger import log_info, log_debug, log_err
+
+
+def read_ast_file(filename):
+    log_info(f"Reading input AST: {filename}")
+    try:
+        ast = ET.parse(filename)
+        return ast
+    except IOError as e:
+        log_err(e.args[1])
+        return None
+    except Exception as e:
+        log_err(str(e))
+        return None
+
+
+def create_ast_file(ps1_file):
+    log_info(f"Creating AST for: {ps1_file}")
+
+    cmd = ["PowerShell", "-ExecutionPolicy", "Unrestricted", "-File",
+           os.path.abspath(os.path.join("tools", "Get-AST.ps1")),
+           "-ps1", os.path.abspath(ps1_file)]
+
+    result = subprocess.run(cmd, stdout=subprocess.PIPE, stderr=subprocess.PIPE, universal_newlines=True)
+
+    for line in result.stdout.splitlines():
+        log_debug(line)
+
+    return result.returncode == 0