How to Sign a PowerShell Script

How to Sign a PowerShell Script

Signing a PowerShell script allows you to verify the authenticity and integrity of the script, ensuring that it has not been tampered with or modified in any way.

This is especially important for scripts that perform sensitive operations or handle sensitive data, as it helps to prevent malicious or unauthorized modifications to the script.

The private key is used to sign the script, while the public key is used to verify the signature.

To sign a script, you first need to create a digital certificate, which you can do using the New-SelfSignedCertificate cmdlet, like this:

New-SelfSignedCertificate -CertStoreLocation Cert:\CurrentUser\My -Subject "PowerShell Script Signing"

This cmdlet creates a new self-signed digital certificate and stores it in the current user's certificate store, with the specified subject. You can then use this digital certificate to sign your script.

To sign a script, you can use the Set-AuthenticodeSignature cmdlet, which adds a digital signature to the specified script file.

For example, to sign a script named myscript.ps1, you can use the Set-AuthenticodeSignature cmdlet like this:

Set-AuthenticodeSignature -FilePath .\myscript.ps1 -Certificate $cert

In this example, the Set-AuthenticodeSignature cmdlet adds a digital signature to the myscript.ps1 script using the $cert variable, which contains the digital certificate.

Once the script is signed, you can verify the signature using the Get-AuthenticodeSignature cmdlet, like this:

Get-AuthenticodeSignature -FilePath .\myscript.ps1

This cmdlet retrieves the signature information for the specified script file, including the signature status, signer, and timestamp. If the signature is valid, the Status property of the output object will be Valid.

You can also use the Set-ExecutionPolicy cmdlet to require that all scripts be signed in order to be run.

For example, to require that all scripts be signed and only allow signed scripts to be run, you can use the Set-ExecutionPolicy cmdlet like this:

Set-ExecutionPolicy -ExecutionPolicy AllSigned

In this example, the Set-ExecutionPolicy cmdlet sets the execution policy to AllSigned, which requires that all scripts be signed in order to be run.

Conclusion

Signing a PowerShell script is a valuable security measure that helps to ensure the authenticity and integrity of the script.

By using a digital certificate and the Set-AuthenticodeSignature cmdlet, you can easily sign your scripts and verify their signatures.

This can help to prevent malicious or unauthorized modifications to your scripts, and improve the security of your PowerShell environment.