msoffcrypto-tool

msoffcrypto-tool (formerly ms-offcrypto-tool) is a Python tool and library for decrypting encrypted MS Office files with password, intermediate key, or private key which generated its escrow key.

Early PoC version: https://github.com/nolze/ms-offcrypto-tool/tree/v0.1.0

Install

pip install msoffcrypto-tool

Examples

As CLI tool (with password)

msoffcrypto-tool -p Passw0rd encrypted.docx decrypted.docx

Test if the file is encrypted or not (exit code 0 or 1 is returned):

msoffcrypto-tool --test -v document.doc

As library

Password and more key types are supported with library functions.

import msoffcrypto

file = msoffcrypto.OfficeFile(open("encrypted.docx", "rb"))

# Use password
file.load_key(password="Passw0rd")

# Use private key
# file.load_key(private_key=open("priv.pem", "rb"))
# Use intermediate key (secretKey)
# file.load_key(secret_key=binascii.unhexlify("AE8C36E68B4BB9EA46E5544A5FDB6693875B2FDE1507CBC65C8BCF99E25C2562"))

file.decrypt(open("decrypted.docx", "wb"))

Supported encryption methods

MS-OFFCRYPTO specs

• ECMA-376 (Agile Encryption/Standard Encryption)
  • MS-DOCX (OOXML) (Word 2007-2016)
  • MS-XLSX (OOXML) (Excel 2007-2016)
  • MS-PPTX (OOXML) (PowerPoint 2007-2016)
• Office Binary Document RC4 CryptoAPI
  • MS-DOC (Word 2002, 2003, 2004)
  • MS-XLS (Excel 2002, 2003, 2004) (experimental)
  • MS-PPT (PowerPoint 2002, 2003, 2004)
• Office Binary Document RC4
  • MS-DOC (Word 97, 98, 2000)
  • MS-XLS (Excel 97, 98, 2000) (experimental)
  • MS-PPT (PowerPoint 97, 98, 2000)
• ECMA-376 (Extensible Encryption)
• XOR Obfuscation

Other

• Word 95 Encryption (Word 95 and prior)
• Excel 95 Encryption (Excel 95 and prior)
• PowerPoint 95 Encryption (PowerPoint 95 and prior)

PRs welcome!

Todo

• Add tests
• Support decryption with passwords
• Support older encryption schemes
• Add function-level tests
• Add API documents
• Publish to PyPI
• Add decryption tests for various file formats
• Merge to more comprehensive projects handling MS Office files (such as oletools?) if possible
• Support decrypting encrypted macros
• Support decrypting encrypted Excel worksheets
• Support decrypting editing protection
• Support encryption

References

• "Backdooring MS Office documents with secret master keys" http://secuinside.com/archive/2015/2015-1-9.pdf
• Technical Documents https://msdn.microsoft.com/en-us/library/cc313105.aspx
  • [MS-OFFCRYPTO] Agile Encryption https://msdn.microsoft.com/en-us/library/dd949735(v=office.12).aspx
• LibreOffice/core https://github.com/LibreOffice/core
• LibreOffice/mso-dumper https://github.com/LibreOffice/mso-dumper
• wvDecrypt http://www.skynet.ie/~caolan/Packages/wvDecrypt.html
• Microsoft Office password protection - Wikipedia https://en.wikipedia.org/wiki/Microsoft_Office_password_protection#History_of_Microsoft_Encryption_password

Alternatives

• herumi/msoffice https://github.com/herumi/msoffice
• DocRecrypt https://blogs.technet.microsoft.com/office_resource_kit/2013/01/23/now-you-can-reset-or-remove-a-password-from-a-word-excel-or-powerpoint-filewith-office-2013/

Use cases and mentions

• https://github.com/jbremer/sflock/commit/3f6a96abe1dbb4405e4fb7fd0d16863f634b09fb
• https://github.com/dtjohnson/xlsx-populate