Windows Code Signing

Code signing is required on Windows to allow your application to be listed in the Microsoft Store and to prevent a SmartScreen warning that your application is not trusted and can not be started, when downloaded from the browser.

It is not required to execute your application on Windows, as long as your end user is okay with ignoring the SmartScreen warning or your user does not download via the browser. This guide covers signing via OV (Organization Validated) certificates and Azure Key Vault. If you use any other signing mechanism not documented here, such as EV (Extended Validation) certificates, check out your certificate issuer documentation and refer to the custom sign command section.

OV Certificates

Danger

This guide only applies to OV code signing certificates acquired before June 1st 2023! For code signing with EV certificates and OV certificates received after that date please consult the documentation of your certificate issuer instead.

Note

If you sign the app with an EV Certificate, it’ll receive an immediate reputation with Microsoft SmartScreen and won’t show any warnings to users.

If you opt for an OV Certificate, which is generally cheaper and available to individuals, Microsoft SmartScreen will still show a warning to users when they download the app. It might take some time until your certificate builds enough reputation. You may opt for submitting your app to Microsoft for manual review. Although not guaranteed, if the app does not contain any malicious code, Microsoft may grant additional reputation and potentially remove the warning for that specific uploaded file.

See the comparison to learn more about OV vs EV certificates.

Prerequisites

• Windows - you can likely use other platforms, but this tutorial uses Powershell native features.
• A working Tauri application
• Code signing certificate - you can acquire one of these on services listed in Microsoft’s docs. There are likely additional authorities for non-EV certificates than included in that list, please compare them yourself and choose one at your own risk.
  • Please make sure to get a code signing certificate, SSL certificates do not work!

Getting Started

There are a few things we have to do to get Windows prepared for code signing. This includes converting our certificate to a specific format, installing this certificate, and decoding the required information from the certificate.

1. Convert your .cer to .pfx

   • You will need the following:

     • certificate file (mine is cert.cer)
     • private key file (mine is private-key.key)

   • Open up a command prompt and change to your current directory using cd Documents/Certs

   • Convert your .cer to a .pfx using openssl pkcs12 -export -in cert.cer -inkey private-key.key -out certificate.pfx

   • You should be prompted to enter an export password DON’T FORGET IT!

2. Import your .pfx file into the keystore.

   • We now need to import our .pfx file.

   • Assign your export password to a variable using $WINDOWS_PFX_PASSWORD = 'MYPASSWORD'

   • Now Import the certificate using Import-PfxCertificate -FilePath certificate.pfx -CertStoreLocation Cert:\CurrentUser\My -Password (ConvertTo-SecureString -String $WINDOWS_PFX_PASSWORD -Force -AsPlainText)

3. Prepare Variables

   • Start ➡️ certmgr.msc to open Personal Certificate Management, then open Personal/Certificates.

   • Find the certificate we just imported and double-click on it, then click on the Details tab.

   • The Signature hash algorithm will be our digestAlgorithm. (Hint: this is likely sha256)

   • Scroll down to Thumbprint. There should be a value like A1B1A2B2A3B3A4B4A5B5A6B6A7B7A8B8A9B9A0B0. This is our certificateThumbprint.

   • We also need a timestamp URL; this is a time server used to verify the time of the certificate signing. I’m using http://timestamp.comodoca.com, but whoever you got your certificate from likely has one as well.

Prepare tauri.conf.json file

1. Now that we have our certificateThumbprint, digestAlgorithm, & timestampUrl we will open up the tauri.conf.json.

2. In the tauri.conf.json you will look for the tauri -> bundle -> windows section. There are three variables for the information we have captured. Fill it out like below.

"windows": {
        "certificateThumbprint": "A1B1A2B2A3B3A4B4A5B5A6B6A7B7A8B8A9B9A0B0",
        "digestAlgorithm": "sha256",
        "timestampUrl": "http://timestamp.comodoca.com"
}

3. Save and run tauri build

4. In the console output, you should see the following output.

info: signing app
info: running signtool "C:\\Program Files (x86)\\Windows Kits\\10\\bin\\10.0.19041.0\\x64\\signtool.exe"
info: "Done Adding Additional Store\r\nSuccessfully signed: APPLICATION FILE PATH HERE

Which shows you have successfully signed the .exe.

And that’s it! You have successfully set up your Tauri application for Windows signing.

Sign your application with GitHub Actions.

We can also create a workflow to sign the application with GitHub actions.

GitHub Secrets

We need to add a few GitHub secrets for the proper configuration of the GitHub Action. These can be named however you would like.

• You can view the encrypted secrets guide on how to add GitHub secrets.

The secrets we used are as follows

GitHub Secrets	Value for Variable
WINDOWS_CERTIFICATE	Base64 encoded version of your .pfx certificate, can be done using this command certutil -encode certificate.pfx base64cert.txt
WINDOWS_CERTIFICATE_PASSWORD	Certificate export password used on creation of certificate .pfx

Workflow Modifications

1. We need to add a step in the workflow to import the certificate into the Windows environment. This workflow accomplishes the following

   1. Assign GitHub secrets to environment variables
   2. Create a new certificate directory
   3. Import WINDOWS_CERTIFICATE into tempCert.txt
   4. Use certutil to decode the tempCert.txt from base64 into a .pfx file.
   5. Remove tempCert.txt
   6. Import the .pfx file into the Cert store of Windows & convert the WINDOWS_CERTIFICATE_PASSWORD to a secure string to be used in the import command.

2. We will be using the tauri-action publish template.

name: 'publish'
on:
  push:
    branches:
      - release

jobs:
  publish-tauri:
    strategy:
      fail-fast: false
      matrix:
        platform: [macos-latest, ubuntu-latest, windows-latest]

    runs-on: ${{ matrix.platform }}
    steps:
      - uses: actions/checkout@v2
      - name: setup node
        uses: actions/setup-node@v1
        with:
          node-version: 12
      - name: install Rust stable
        uses: actions-rs/toolchain@v1
        with:
          toolchain: stable
      - name: install webkit2gtk (ubuntu only)
        if: matrix.platform == 'ubuntu-latest'
        run: |
          sudo apt-get update
          sudo apt-get install -y webkit2gtk-4.0
      - name: install app dependencies and build it
        run: yarn && yarn build
      - uses: tauri-apps/tauri-action@v0
        env:
          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
        with:
          tagName: app-v__VERSION__ # the action automatically replaces \_\_VERSION\_\_ with the app version
          releaseName: 'App v__VERSION__'
          releaseBody: 'See the assets to download this version and install.'
          releaseDraft: true
          prerelease: false

3. Right above -name: install app dependencies and build it you will want to add the following step

- name: import windows certificate
  if: matrix.platform == 'windows-latest'
  env:
    WINDOWS_CERTIFICATE: ${{ secrets.WINDOWS_CERTIFICATE }}
    WINDOWS_CERTIFICATE_PASSWORD: ${{ secrets.WINDOWS_CERTIFICATE_PASSWORD }}
  run: |
    New-Item -ItemType directory -Path certificate
    Set-Content -Path certificate/tempCert.txt -Value $env:WINDOWS_CERTIFICATE
    certutil -decode certificate/tempCert.txt certificate/certificate.pfx
    Remove-Item -path certificate -include tempCert.txt
    Import-PfxCertificate -FilePath certificate/certificate.pfx -CertStoreLocation Cert:\CurrentUser\My -Password (ConvertTo-SecureString -String $env:WINDOWS_CERTIFICATE_PASSWORD -Force -AsPlainText)

4. Save and push to your repo.

5. Your workflow can now import your windows certificate and import it into the GitHub runner, allowing for automated code signing!

Azure Key Vault

You can sign the Windows executables by providing an Azure Key Vault certificate and credentials.

Note

This guide uses relic due to its support to secret-based authentication, though you can configure alternative tools if you prefer. To download relic, check its releases page or run go install github.com/sassoftware/relic/v8@latest.

1. Key Vault

In the Azure Portal navigate to the Key vaults service to create a new key vault by clicking the “Create” button. Remember the “Key vault name” as you will need that information to configure the certificate URL.

2. Certificate

After creating a key vault, select it and go to the “Objects > Certificates” page to create a new certificate and click the “Generate/Import” button. Remember the “Certificate name” as you will need that information to configure the certificate URL.

3. Tauri Configuration

relic uses a configuration file to determine which signing key it should use. For Azure Key Vault you also need the certificate URL. Create a relic.conf file in the src-tauri folder and configure relic to use your certificate:

src-tauri/relic.conf

tokens:
  azure:
    type: azure

keys:
  azure:
    token: azure
    id: https://\<KEY_VAULT_NAME\>.vault.azure.net/certificates/\<CERTIFICATE_NAME\>

Note that you must replace <KEY_VAULT_NAME> and <CERTIFICATE_NAME> with the appropriate names from the previous steps.

To configure Tauri to use your Azure Key Vault configuration for signing change the bundle > windows > signCommand config value:

tauri.conf.json

{
  "bundle": {
    "windows": {
      "signCommand": "relic sign --file %1 --key azure --config relic.conf"
    }
  }
}

4. Credentials

relic must authenticate with Azure in order to load the certificate. In the Azure portal landing page, go to the “Microsoft Entra ID” service and head to the “Manage > App registrations” page. Click “New registration” to create a new app. After creating the app, you are redirected to the application details page where you can see the “Application (client) ID” and “Directory (tenant) ID” values. Set these IDs to the AZURE_VAULT_ID and AZURE_TENANT_ID environment variables respectively.

In the “Manage > Certificates & secrets” page click the “New client secret” button and set the text in the “Value” column as the AZURE_CLIENT_SECRET environment variable.

After setting up all the credentials, head back to your key vault’s page and navigate to the “Access control (IAM)” page. You must assign the “Key Vault Certificate User” and “Key Vault Crypto User” roles to your newly created application.

After setting up all these variables, running tauri build will produce signed Windows installers!

Custom Sign Command

In the Azure Key Vault documentation above we used a powerful Tauri Windows signing configuration to force the Tauri CLI to use a special shell command to sign Windows installer executables. The bundle > windows > signCommand configuration option can be used to use any codesign tool that can sign Windows executables.

Tip

When cross compiling Windows installers from Linux and macOS machines, you must use a custom sign command as the default implementation only works on Windows machines.