Skip to content

App Service site allows insecure TLS versions#

Security · App Service · Rule · 2020_06 · Critical

App Service should not accept weak or deprecated transport protocols for client-server communication.

Description#

The minimum version of TLS that Azure App Service accepts is configurable. Older TLS versions are no longer considered secure by industry standards, such as PCI DSS.

App Service lets you disable outdated protocols and enforce TLS 1.2. By default, a minimum of TLS 1.2 is enforced.

Recommendation#

Consider configuring the minimum supported TLS version to be 1.2. Also consider using Azure Policy to audit or enforce this configuration.

Examples#

Configure with Bicep#

To deploy App Services that pass this rule:

  • Set the properties.siteConfig.minTlsVersion property to 1.2 or 1.3.

For example:

Azure Bicep snippet
resource web 'Microsoft.Web/sites@2024-04-01' = {
  name: name
  location: location
  identity: {
    type: 'SystemAssigned'
  }
  kind: 'web'
  properties: {
    serverFarmId: plan.id
    httpsOnly: true
    clientAffinityEnabled: false
    siteConfig: {
      alwaysOn: true
      minTlsVersion: '1.2'
      ftpsState: 'Disabled'
      remoteDebuggingEnabled: false
      http20Enabled: true
      netFrameworkVersion: 'v8.0'
      healthCheckPath: '/healthz'
      metadata: [
        {
          name: 'CURRENT_STACK'
          value: 'dotnet'
        }
      ]
    }
  }
}

Configure with Azure Verified Modules

A pre-validated module supported by Microsoft is available from the Azure Bicep public registry. To reference the module, please use the following syntax:

br/public:avm/res/web/site:<version>

To use the latest version:

br/public:avm/res/web/site:0.9.0

Configure with Azure template#

To deploy App Services that pass this rule:

  • Set the properties.siteConfig.minTlsVersion property to 1.2 or 1.3.

For example:

Azure Template snippet
{
  "type": "Microsoft.Web/sites",
  "apiVersion": "2023-01-01",
  "name": "[parameters('name')]",
  "location": "[parameters('location')]",
  "identity": {
    "type": "SystemAssigned"
  },
  "kind": "web",
  "properties": {
    "serverFarmId": "[resourceId('Microsoft.Web/serverfarms', parameters('planName'))]",
    "httpsOnly": true,
    "siteConfig": {
      "alwaysOn": true,
      "minTlsVersion": "1.2",
      "ftpsState": "Disabled",
      "remoteDebuggingEnabled": false,
      "http20Enabled": true,
      "netFrameworkVersion": "v8.0",
      "healthCheckPath": "/healthz",
      "metadata": [
        {
          "name": "CURRENT_STACK",
          "value": "dotnet"
        }
      ]
    }
  },
  "dependsOn": [
    "[resourceId('Microsoft.Web/serverfarms', parameters('planName'))]"
  ]
}

Configure with Azure Policy#

To address this issue at runtime use the following policies:

Comments