Sign VBA Macro Certificate

2024-04-12 12:16 UTC gpt-4 Open in ChatGPT ↗

Signing an Excel VBA macro with a certificate, especially one from an external provider like Certum, can sometimes result in errors due to various factors such as compatibility issues, the digital certificate’s properties, or the way the certificate is installed and used. Given that you’ve received an error stating “There was a problem with the digital certificate. The VBA project could not be signed. The signature will be discarded,” here are a few steps and considerations to troubleshoot and potentially resolve the issue:

1. Check Certificate Type and Usage

Ensure the digital certificate is specifically intended for code signing. Code signing certificates are distinct from SSL or other types of certificates because they are designed to sign software, macros, and applications. The certificate should allow for the signing of VBA macros explicitly.

2. Install the Certificate Properly

Ensure the certificate has been correctly installed in the Windows Certificate Store, particularly in the “Personal” store. Sometimes, manually installing the certificate to the right store can resolve issues.

3. Use the Correct Certificate Chain

If your certificate is part of a chain (i.e., it requires intermediate certificates), ensure that the entire chain is correctly installed on your system. Missing intermediate certificates can lead to validation failures.

4. Ensure Compatibility

Although rare, compatibility issues might arise. Ensure that the version of Excel and the operating system are compatible with the requirements specified by Certum for using their certificates.

5. Check for Revocation or Expiration

Ensure that the certificate has not expired and has not been revoked. You can check the certificate’s status through its properties dialog in the Windows Certificate Store or using Certum’s tools, if available.

6. Adjust Security Settings in Excel

Excel’s macro security settings might be too stringent, preventing the signing process from completing successfully. Adjust these settings temporarily to see if it affects the ability to sign the VBA project.

7. Use a Dedicated Tool

Some users have reported success using dedicated third-party tools for code signing when facing issues with direct signing from within Excel. These tools can offer more detailed error messages and troubleshooting options.

8. Contact Certum Support

Since Certum has indicated that other clients have successfully used workarounds, reaching out to their support team could provide you with specific steps or tools they recommend. They might have encountered this issue before and could offer a tailored solution.

9. Experiment on Another Machine

If possible, try signing the macro on a different machine. This can help determine if the issue is specific to your computer’s configuration.

Technical Forums and Communities

Since this issue involves a workaround rather than a standard feature, searching for or asking in technical forums such as Stack Overflow or specialized Excel and VBA forums might yield useful advice from others who have encountered and solved similar issues.

Note

Given the specific nature of the issue and the reliance on workarounds, success might require a combination of the above steps or even specific guidance from Certum or others who have successfully signed VBA macros with external certificates.

It seems there was an issue accessing specific threads on Stack Overflow that might have contained solutions or discussions relevant to your problem with signing Excel VBA macros using a Certum certificate. This could be due to a variety of reasons, such as site restrictions or the specific URLs being temporarily unavailable.

In the meantime, here are some alternative steps you might consider trying, based on common practices and potential workarounds for similar issues:

Ensure Excel is Updated: Sometimes, issues with signing macros can be related to bugs or incompatibilities in specific versions of Excel. Make sure your version of Excel is fully updated.
Use signtool.exe: Some users have found success using the signtool.exe utility that comes with the Microsoft Windows SDK or Visual Studio for signing macros. This tool provides more flexibility in terms of the algorithms it supports for signing.
Check for Blocked Content: Ensure that the certificate or any of its components are not blocked by your system. You can check this by right-clicking on the certificate file, selecting Properties, and looking for an “Unblock” button or checkbox.
Re-import the Certificate: Even if the installation seems solid, re-importing the certificate to the Windows Certificate Store, ensuring it’s placed in the correct store (typically “Personal”), can sometimes resolve subtle issues.
Administrative Rights: Try running Excel as an administrator when attempting to sign the VBA macro. This can sometimes bypass issues related to permissions.
Consult with Certum: Given the specific error and that Certum has mentioned other clients finding workarounds, reaching out to Certum’s technical support for more detailed guidance might yield specific instructions or insights pertinent to their certificates.

If these general suggestions don’t resolve the issue, and without direct access to the specific Stack Overflow discussions that might have addressed this error, the next best step is to directly consult with Certum’s support or explore detailed documentation they provide regarding the use of their certificates for signing Excel VBA macros. Additionally, consider reaching out to Microsoft Support or exploring Microsoft’s developer forums for insights into any potential compatibility issues or updates that might affect the signing process.

Using signtool.exe to sign VBA macros isn’t a direct or standard method for embedding digital signatures into Excel VBA projects. The signtool.exe utility is primarily designed for signing executable files, DLLs, and Windows drivers as part of the software publishing process. It works by attaching a digital signature to a file, which verifies the file’s integrity and publisher.

VBA macros within Excel or other Office applications are embedded within the document files themselves (.xls, .xlsx, .xlsm, etc.), and the process for signing them is typically handled through the application’s interface or via specific methods that integrate with Office software’s security frameworks.

However, developers looking for alternative ways to sign their VBA macros due to issues with the standard process have explored various workarounds. These can include:

Extracting and Reinserting: Technically, one could extract the macro code, sign it using an external tool, and then reinsert it into the Excel file. However, this process is complex, error-prone, and not officially supported. It would also remove much of the automation and integrity checks provided by the Office suite’s built-in signing features.
Scripting and Automation Tools: Instead of directly using signtool.exe, developers might employ scripts or third-party tools designed to automate the process of signing macros within Excel. These tools might use a combination of Office application automation, certificate management, and custom signing processes to achieve the desired outcome.
Manual Process via Office UI: The recommended and most straightforward way to sign VBA macros is still through the Excel interface (Developer Tab → Visual Basic → Tools → Digital Signature). This method ensures compatibility and recognizes the complexities of Office file formats and the embedded nature of VBA code.

If you’re encountering specific problems signing VBA macros directly within Excel using certificates from providers like Certum, it could be worth reaching out to the certificate authority for guidance or consulting Microsoft’s documentation for any updates or changes to the macro signing process. Alternative methods, such as using signtool.exe, would likely involve a level of manual process and workaround that could complicate deployment and verification processes.

The process of extracting and reinserting VBA macro code for the purpose of signing it with an external tool like signtool.exe is highly unconventional, not officially supported by Microsoft, and involves several manual steps that can be complex and error-prone. It’s crucial to approach this with caution and be aware that this method can disrupt the integrity and functionality of your Excel file. Here is a high-level overview of the steps involved in such a process:

Preparing Your Environment

Backup Your Excel File: Before proceeding, ensure you have a backup of your Excel file (.xlsx or .xlsm) to prevent data loss.
Install Necessary Tools: Ensure you have the necessary tools installed, including a code editor (e.g., Notepad++, Visual Studio Code) and signtool.exe (part of the Microsoft Windows SDK or Visual Studio).

Extracting the VBA Macro Code

Open Your Excel File: Rename the Excel file extension from .xlsx or .xlsm to .zip.
Extract the ZIP File: Extract the contents of the ZIP file to a folder.
Locate the VBA Project: Navigate to the extracted folder and find the VBA project, typically located in a path similar to xl/vbaProject.bin for Excel files.
Extract VBA Code: You might need a specialized tool or script that can extract the VBA code from the vbaProject.bin file. This step is highly technical and may require additional research or tools specifically designed for reading and extracting from binary VBA project files.

Signing the Extracted Code

Prepare Your Code for Signing: Place the extracted VBA code into a format or file that can be recognized by signtool.exe or the external tool you are using for signing.
Sign the Code: Use signtool.exe to sign the code. The exact command will depend on the format of your extracted code and your digital certificate, but a generic command looks something like this:
```
signtool sign /f path\to\your\certificate.pfx /p password /fd SHA256 /td SHA256 /tr http://timestamp.digicert.com /v path\to\your\file
```
Verify the Signature: Ensure the signature is applied correctly to your code or file by using the signtool verify command.

Reinserting the VBA Macro Code

Reinsert the Signed Code: This is the most challenging and riskiest part of the process. You will need to replace the unsigned VBA code in the vbaProject.bin with your signed code. This step may require manual editing of the binary file or a specialized tool designed to insert code into binary VBA project files.
Repack the Excel File: Once the vbaProject.bin file is updated with the signed code, repackage the contents of the folder back into a ZIP file and rename the extension from .zip to .xlsx or .xlsm.
Test Your Excel File: Open your modified Excel file in Excel to test if the macro works as expected. Pay close attention to any security warnings or errors that may indicate the file’s integrity was compromised during the process.

Important Considerations

Automation and Integrity: This manual process removes much of the automation and integrity checks provided by the Office suite’s built-in signing features.
Compatibility and Stability: There is a significant risk of corrupting the Excel file or the embedded VBA macro, making the document unstable or unusable.
Security: Bypassing the built-in security features may introduce vulnerabilities or weaken the trust mechanism established by the digital signing process.

Given the complexity and risks associated with this method, it’s strongly recommended to pursue official and supported methods for signing VBA macros when possible. If you’re facing specific issues with the standard process, seeking assistance from Microsoft support or the certificate provider (Certum in your case) may yield safer and more reliable solutions.

To extract VBA code from the vbaProject.bin file found in Excel (.xlsm, .xlsx) or other Office documents, you can use the oletools Python package, which is specifically designed for analyzing OLE files (Object Linking and Embedding, the technology behind many Microsoft file formats including VBA macros). The olevba tool within oletools can parse VBA macro source code from Office documents, including the binary vbaProject.bin files.

Step 1: Install `oletools`

First, you need to install oletools. You can do this by running the following command in your terminal or command prompt:

pip install oletools

Python Script to Extract VBA Code

Here’s a simple Python script that uses olevba from oletools to extract the VBA code from a vbaProject.bin file. Please ensure you have installed oletools before running this script.

from oletools.olevba import VBA_Parser

def extract_vba_code(vba_file_path):
    """
    Extracts VBA code from a given vbaProject.bin file and prints the code to the console.

    :param vba_file_path: Path to the vbaProject.bin file.
    """
    # Parse the VBA project file
    vba_parser = VBA_Parser(vba_file_path)

    if vba_parser.detect_vba_macros():
        print("VBA Macros found. Extracting...")

        # Extract and print VBA code from all modules
        for (_, _, vba_code) in vba_parser.extract_macros():
            print(vba_code.decode('utf-8'))
    else:
        print("No VBA Macros found.")

    # Close the parser
    vba_parser.close()

# Replace 'path_to_your_vbaProject.bin' with the actual path to your vbaProject.bin file
extract_vba_code('path_to_your_vbaProject.bin')

How to Use the Script

Replace 'path_to_your_vbaProject.bin' with the actual path to your vbaProject.bin file.
Run the script. The extracted VBA code will be printed to the console.

Note

This script simply prints the extracted VBA code to the console. If you need to save the code to a file, you can modify the script to write the output to a file instead.
The script assumes the vbaProject.bin file is not corrupted and is accessible. If the file is part of an encrypted document, you’ll need to decrypt the document first before extracting the VBA code.
Using this script for malicious purposes is against the law. Ensure you have the right to access and modify the VBA code in the documents you’re working with.

signtool.exe is a part of the Microsoft Windows SDK and Visual Studio that’s used primarily for signing executable files, drivers, and other binary files that are recognized by the Windows operating system. It does not directly support signing script files or source code like VBA macros without them being part of a recognized binary format. Therefore, to prepare your extracted VBA code for signing with signtool.exe or a similar external tool, you would typically need to embed it into a container or file format that these tools can sign. One common approach is to wrap the code into a self-signed executable or DLL that can then be signed.

However, this approach is not straightforward for VBA macros and could significantly complicate deployment and usage within Excel. It’s also worth mentioning that this might not achieve the desired effect of signing the macro in a way that Excel recognizes and trusts, as Excel expects a signed digital certificate within the macro itself or the document, not in an external binary.

Steps to Prepare VBA Code for External Signing (Hypothetical Scenario)

If you still want to proceed for educational or experimental purposes, here’s a general outline of the steps you would theoretically take, focusing on creating a dummy binary that contains your VBA code, which can then be signed. This example is purely illustrative and not a recommended practice for Excel VBA macro signing.

1. Create a Dummy Container

Write Your VBA Code to a Text File: Save your extracted VBA macro code into a plain text file, e.g., MyMacro.vba.
Create a Simple Executable or Script Wrapper: Develop a simple application or script in a language like C# or PowerShell that does nothing but exist as a container. This step is necessary because signtool.exe is designed to work with executables (.exe) or dynamic link libraries (.dll).
- C# Example: Create a simple console application that does nothing significant but includes your VBA code as a resource or as a comment.
- PowerShell Example: Create a PowerShell script that merely outputs a message, and include your VBA code in the script as a comment.

2. Convert to a Signable Format

For C#, compile your application to produce an executable (.exe) or a DLL (.dll).
For PowerShell or similar scripts, you might need to package the script into an executable using tools like PS2EXE.

3. Sign Your Dummy Container

Now, use signtool.exe to sign the executable or DLL containing your VBA code. The command might look something like this:

signtool sign /f path\to\your\certificate.pfx /p yourpassword /fd SHA256 /td SHA256 /tr http://timestamp.digicert.com /v path\to\your\file.exe

Important Considerations

This Does Not Sign Your Macro for Excel: Excel will not recognize the macro as signed through this method. The signed status of the dummy container has no effect on the macro’s trustworthiness within Excel.
Security Risks: Embedding code in this manner, especially for execution, carries significant security risks and could be misused. Always ensure your practices comply with security policies and legal requirements.
Deployment Complexity: This approach complicates the deployment of your VBA macro, as it now involves managing and distributing external binaries unrelated to Excel’s native functionality.

For practical purposes, especially in a professional or enterprise environment, sticking to the traditional methods of signing macros directly through Excel or seeking an officially supported solution from Microsoft or your certificate authority (like Certum) is strongly advised.

If the goal is to have a signed VBA macro recognized by Excel without directly using Excel’s built-in methods for macro signing, but in a way that is recognized as trustworthy by Excel, there’s a significant challenge. Excel, and Office applications in general, have specific expectations for how macros are signed and recognized within the application. These mechanisms are deeply integrated into the application’s security model, which relies on digital signatures directly embedded within the file (for example, within the .xlsm or .docm file itself).

Given these constraints, if standard signing processes within Excel are not meeting your needs due to technical issues or specific requirements from external certificates (like those from Certum), and if conventional workarounds have not been successful, it’s essential to explore alternative, supported pathways that still align with Excel’s security models. Here are some alternative approaches:

1. Use Self-Signed Certificates for Internal Use

For internal use and testing, you can create a self-signed certificate using tools provided by Microsoft (like SelfCert.exe included with Office installations) to sign your macros. This won’t bypass Excel’s security model but offers a way to proceed with macro signing without needing an external CA. The limitation here is trust management outside your organization.

2. Engage with Microsoft and Certificate Authority Support

If there’s a specific issue with using Certum (or another CA’s) certificates with Excel:

Reach out to Microsoft Support: There may be known issues or updates related to Excel’s handling of certificates that Microsoft can address or provide workarounds for.
Consult with Certum Support: Since Certum has indicated that other clients have successfully used workarounds, they may offer specific guidance or tools for their certificates.

3. Explore Third-party Tools for Office File Manipulation

Some third-party tools and libraries aim to manipulate Office file formats, including embedding signatures into Office documents. Tools such as Aspose or LibreOffice have capabilities around Office file manipulation and might offer alternative ways to insert digital signatures. However, the effectiveness and recognition of such signatures within Excel might vary and should be thoroughly tested.

4. Automate Excel’s Signing Process

If the issue is with the manual process or integration into a broader build or deployment pipeline:

Macro-Enabled Templates: Create a macro-enabled template with the necessary macros already signed. This way, new documents based on the template inherit the signed state of the macros.
Automate via Scripting: Use scripting languages that can interact with Excel’s COM object model (like PowerShell or Python with pywin32) to automate the opening of files, signing of macros, and saving of files as part of a larger automated process.

5. Legal and Ethical Considerations

Bypassing or altering Excel’s security features, especially in ways not supported or documented by Microsoft, can introduce security risks, potentially violate terms of service, and might not be legally sound, depending on jurisdiction and context. Always ensure that your approach is compliant with all relevant laws, regulations, and organizational policies.

Conclusion

The safest and most reliable way to have Excel recognize and trust a signed VBA macro is to use the signing mechanisms that are integrated into Excel and supported by Microsoft. Exploring the reasons behind the need to bypass these mechanisms might uncover alternative solutions that are both effective and aligned with best practices for software security and integrity.

you said earlier: Reinserting the VBA Macro Code

Reinsert the Signed Code: This is the most challenging and riskiest part of the process. You will need to replace the unsigned VBA code in the vbaProject.bin with your signed code. This step may require manual editing of the binary file or a specialized tool designed to insert code into binary VBA project files.
Repack the Excel File: Once the vbaProject.bin file is updated with the signed code, repackage the contents of the folder back into a ZIP file and rename the extension from .zip to .xlsx or .xlsm.

how to proceed after signing the powershell container?

Reinserting VBA macro code back into an Excel file, especially after wrapping and signing it using an unconventional method like a PowerShell container, involves steps that are not directly supported or recommended due to the complexities and potential integrity and security issues with Excel files. However, understanding the hypothetical process can offer insight into how Office file formats work and the challenges involved in manual manipulation.

Step-by-Step Overview (Hypothetical Process)

Assuming you’ve wrapped your VBA code in a PowerShell script, signed it using signtool.exe, and now wish to somehow utilize this to have a “signed” VBA macro recognized by Excel, the direct reinsertion is not straightforward or recommended. Here’s why:

Excel’s Security Model: Excel’s security model for macros is designed to trust VBA code that is digitally signed within the Excel file itself (e.g., .xlsm). A PowerShell script, even when signed, doesn’t align with this model because Excel expects the signature to be part of the macro’s metadata within its own file structure.
Integrity Checks: Excel performs integrity checks on macro signatures. Simply inserting code from an external source could break these checks, leading Excel to either reject the macro or treat the document as potentially corrupted or unsafe.
Compatibility and Functionality Issues: Manipulating Office file formats (like .xlsx or .xlsm) manually or with unsanctioned tools can lead to compatibility and functionality issues, potentially rendering the file unusable in Excel.

Alternative Approach for Conceptual Understanding

If the goal is to learn about manipulating Office formats or for experimental purposes unrelated to production use, you could theoretically explore the following steps AFTER signing a PowerShell script or another container, understanding this does not achieve a “signed” state recognized by Excel:

Extract and Modify vbaProject.bin: Use a tool capable of editing or replacing the vbaProject.bin file within the Excel file structure (which is essentially a ZIP archive). Tools like oletools or binary editors can inspect or modify these files, but there’s no straightforward method to “reinsert” signed PowerShell code into vbaProject.bin in a way that Excel will recognize as a valid and trusted macro.
Repackage the Excel File: After any modifications (which, to reiterate, are unlikely to be recognized by Excel as a valid signing method for VBA code), you would repackage the modified contents into a ZIP file and rename the extension back to .xlsm.

Recommended Approach

Directly Sign Macros in Excel: Use Excel’s built-in functionality or certificates from trusted authorities designed to work with Excel’s security model. This ensures the macros are signed in a manner Excel recognizes and trusts.
Consult with Security and Compliance Experts: If working within an organization or for commercial software, consult with IT security and compliance experts to ensure that any approach to macro signing aligns with best practices, security policies, and legal requirements.

Final Note

The steps described in modifying Office file formats and attempting to bypass or simulate signing processes are hypothetical and not recommended for actual use. They serve to highlight the complexities involved and underscore the importance of using supported and secure methods for working with VBA macros and Excel files.