Code signing in PowerShell - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to sign a PowerShell script file using a certificate.

PowerShell

Set-AuthenticodeSignature -FilePath script.ps1 -Certificate [1]

Drag options to blanks, or click blank then click option'

AGet-ChildItem Cert:\CurrentUser\My -CodeSigningCert

BGet-Process

CGet-Service

DGet-Content script.ps1

Attempts:

3 left

💡 Hint

Common Mistakes

Using Get-Process or Get-Service instead of a certificate.

Passing file content instead of a certificate object.

The Set-AuthenticodeSignature cmdlet requires a code signing certificate, which you get using Get-ChildItem from the certificate store with the -CodeSigningCert flag.

2fill in blank

medium

Complete the code to verify the signature of a PowerShell script file.

PowerShell

Get-AuthenticodeSignature -FilePath [1]

Drag options to blanks, or click blank then click option'

Ascript.ps1

BC:\Windows\System32\notepad.exe

Cdocument.txt

Dscript.psm1

Attempts:

3 left

💡 Hint

Common Mistakes

Using a non-script file like a text or executable file.

Using a module file (.psm1) instead of a script file.

You verify the signature of the PowerShell script file by specifying its path, here 'script.ps1'.

3fill in blank

hard

Fix the error in the code to sign a script with the first code signing certificate found.

PowerShell

$cert = Get-ChildItem Cert:\CurrentUser\My -CodeSigningCert | [1]
Set-AuthenticodeSignature -FilePath script.ps1 -Certificate $cert

Drag options to blanks, or click blank then click option'

AWhere-Object { $_.Subject -eq 'Test' }

BGet-Process

CSelect-Object -First 1

DSort-Object -Property NotAfter

Attempts:

3 left

💡 Hint

Common Mistakes

Using Where-Object without a proper filter.

Using Get-Process which returns processes, not certificates.

To get the first certificate from the list, use Select-Object -First 1. This ensures $cert is a single certificate object.

4fill in blank

hard

Fill both blanks to create a hash table with the signature status and signer certificate subject.

PowerShell

$sig = Get-AuthenticodeSignature script.ps1
$result = @{ Status = $sig.[1]; Signer = $sig.[2].Subject }

Drag options to blanks, or click blank then click option'

AStatus

BSignerCertificate

CStatusMessage

DCertificate

Attempts:

3 left

💡 Hint

Common Mistakes

Using StatusMessage instead of Status for the signature status.

Using Certificate instead of SignerCertificate for the signer.

The signature status is in $sig.Status and the signer certificate is in $sig.SignerCertificate. We access the Subject property of the certificate.

5fill in blank

hard

Fill all three blanks to filter certificates valid for code signing and not expired.

PowerShell

$validCerts = Get-ChildItem Cert:\CurrentUser\My | Where-Object { $_.EnhancedKeyUsageList.[1] -contains 'Code Signing' -and $_.NotAfter [2] (Get-Date) } | Select-Object -First [3]

Drag options to blanks, or click blank then click option'

AFriendlyName

BContains

C-gt

D1

Attempts:

3 left

💡 Hint

Common Mistakes

Using Contains instead of FriendlyName to check usage.

Using wrong comparison operator for dates.

Selecting more than one certificate.

We use FriendlyName to access the EnhancedKeyUsageList friendly names array with -contains to check if 'Code Signing' is present, -gt to check NotAfter date is greater than today, and select the first certificate with Select-Object -First 1.

Practice

1. What is the main purpose of code signing a PowerShell script?

easy

A. To prove the script is from a trusted source and has not been altered

B. To make the script run faster

C. To encrypt the script content

D. To convert the script into an executable file

Solution

1. Step 1: Understand code signing purpose

   Code signing is used to verify the identity of the script author and ensure the script has not been changed.

2. Step 2: Compare options

   Only To prove the script is from a trusted source and has not been altered describes this purpose correctly. Other options describe unrelated actions like encryption or performance.

3. Final Answer:

   To prove the script is from a trusted source and has not been altered -> Option A

4. Quick Check:

   Code signing = prove trust and integrity [OK]

Hint: Code signing proves trust and no changes [OK]

Common Mistakes:

• Thinking code signing encrypts the script
• Believing code signing speeds up execution
• Confusing code signing with file conversion

2. Which PowerShell command is used to sign a script with a certificate?

easy

A. New-ScriptSignature

B. Sign-ScriptCertificate

C. Set-AuthenticodeSignature

D. Add-ScriptCertificate

Solution

1. Step 1: Identify the correct cmdlet for signing

   The official PowerShell cmdlet to sign scripts is Set-AuthenticodeSignature.

2. Step 2: Verify other options

   Other options are not valid PowerShell commands for signing scripts.

3. Final Answer:

   Set-AuthenticodeSignature -> Option C

4. Quick Check:

   Sign script cmdlet = Set-AuthenticodeSignature [OK]

Hint: Remember: Set-AuthenticodeSignature signs scripts [OK]

Common Mistakes:

• Using non-existent cmdlets like Sign-ScriptCertificate
• Confusing signing with creating certificates
• Misspelling the cmdlet name

3. What will be the output of this PowerShell command if the script is successfully signed?

Set-AuthenticodeSignature -FilePath 'script.ps1' -Certificate $cert

medium

A. The script file is deleted

B. An error message about missing parameters

C. No output is shown

D. A Signature object showing Status as Valid

Solution

1. Step 1: Understand Set-AuthenticodeSignature output

   This cmdlet returns a Signature object with a Status property indicating if signing succeeded.

2. Step 2: Interpret successful signing output

   If signing succeeds, Status will be 'Valid'. No deletion or silent output occurs.

3. Final Answer:

   A Signature object showing Status as Valid -> Option D

4. Quick Check:

   Successful signing = Status Valid output [OK]

Hint: Successful signing returns Status Valid object [OK]

Common Mistakes:

• Expecting no output after signing
• Thinking the script file is deleted
• Confusing error messages with success

4. You run this command but get an error: Set-AuthenticodeSignature : Cannot find the certificate. What is the likely cause?

medium

A. The script is already signed

B. The certificate variable is empty or invalid

C. PowerShell version is too old

D. The script file path is incorrect

Solution

1. Step 1: Analyze the error message

   The error says it cannot find the certificate, meaning the $cert variable is likely empty or invalid.

2. Step 2: Check other options

   Incorrect file path causes a different error. PowerShell version or existing signature do not cause this specific error.

3. Final Answer:

   The certificate variable is empty or invalid -> Option B

4. Quick Check:

   Certificate missing error = invalid $cert [OK]

Hint: Check certificate variable if 'Cannot find certificate' error [OK]

Common Mistakes:

• Assuming file path is the problem
• Thinking PowerShell version causes this error
• Believing script already signed causes this error

5. You want to sign multiple scripts in a folder using the same certificate. Which PowerShell snippet correctly signs all .ps1 files?

hard

A. Get-ChildItem -Path . -Filter '*.ps1' | ForEach-Object { Set-AuthenticodeSignature -FilePath $_.FullName -Certificate $cert }

B. Set-AuthenticodeSignature -FilePath '*.ps1' -Certificate $cert

C. ForEach ($file in '*.ps1') { Set-AuthenticodeSignature -FilePath $file -Certificate $cert }

D. Get-Content '*.ps1' | Set-AuthenticodeSignature -Certificate $cert

Solution

1. Step 1: Identify correct way to get all .ps1 files

   Get-ChildItem -Filter '*.ps1' lists all script files in the folder.

2. Step 2: Apply signing to each file

   Using ForEach-Object to call Set-AuthenticodeSignature on each file with the certificate is correct.

3. Step 3: Check other options

   Set-AuthenticodeSignature -FilePath '*.ps1' -Certificate $cert tries to sign a wildcard path directly (invalid). ForEach ($file in '*.ps1') { Set-AuthenticodeSignature -FilePath $file -Certificate $cert } treats '*.ps1' as a string list (wrong). Get-Content '*.ps1' | Set-AuthenticodeSignature -Certificate $cert pipes file content, not file paths (wrong).

4. Final Answer:

   Get-ChildItem -Path . -Filter '*.ps1' | ForEach-Object { Set-AuthenticodeSignature -FilePath $_.FullName -Certificate $cert } -> Option A

5. Quick Check:

   Use Get-ChildItem + ForEach-Object to sign all scripts [OK]

Hint: Use Get-ChildItem and ForEach-Object to sign multiple files [OK]

Common Mistakes:

• Trying to sign wildcard paths directly
• Using file content instead of file paths
• Treating '*.ps1' as a list of files