Code signing in PowerShell - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is code signing in PowerShell?

Code signing is the process of digitally signing scripts or executables to verify their origin and ensure they have not been altered. It helps users trust the code they run.

beginner

Which PowerShell cmdlet is used to sign a script?

The <code>Set-AuthenticodeSignature</code> cmdlet is used to digitally sign a PowerShell script with a certificate.

beginner

What is a code signing certificate?

A code signing certificate is a digital certificate issued by a trusted authority. It contains a public key and identifies the signer, allowing verification of the script's authenticity.

beginner

How can you check if a PowerShell script is signed and valid?

Use Get-AuthenticodeSignature <script.ps1>. It shows the signature status like Valid, UnknownError, or NotSigned.

beginner

Why is code signing important for script security?

Code signing ensures scripts come from a trusted source and have not been changed. It protects users from running harmful or tampered code.

Which cmdlet signs a PowerShell script?

A Sign-Script

B Get-AuthenticodeSignature

C New-Signature

D Set-AuthenticodeSignature

Set-AuthenticodeSignature is used to sign scripts. Get-AuthenticodeSignature checks signatures.

What does a code signing certificate provide?

A Encryption of script content

B Verification of script origin and integrity

C Execution permission for scripts

D Automatic script updates

A code signing certificate verifies who signed the script and that it was not changed.

How do you verify a script's signature in PowerShell?

A Get-AuthenticodeSignature

B Set-AuthenticodeSignature

C Check-Signature

D Verify-Script

Get-AuthenticodeSignature shows the signature status of a script.

What does a 'Valid' status mean when checking a script's signature?

A The script is unsigned

B The certificate is expired

C The signature is trusted and intact

D The script has errors

'Valid' means the signature matches and the certificate is trusted.

Why should you run only signed scripts?

A They come from trusted sources and are not altered

B They are guaranteed error-free

C They run faster

D They use less memory

Signed scripts help ensure safety by confirming the source and integrity.

Explain what code signing is and why it matters in PowerShell scripting.

Think about how you can prove a script is safe to run.

Describe the steps to sign a PowerShell script and verify its signature.

Consider the cmdlets used for signing and checking.

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