Cis Azure Compute 2.1.7

Ensure 'HTTPS Only' is set to 'On'

Description

Azure App Service allows apps to run under both HTTP and HTTPS by default. Apps can be accessed by anyone using non-secure HTTP links by default. Non-secure HTTP requests can be restricted and all HTTP requests redirected to the secure HTTPS port. It is recommended to enforce HTTPS-only traffic.

Rationale

Enabling HTTPS-only traffic will redirect all non-secure HTTP requests to HTTPS ports. HTTPS uses the TLS/SSL protocol to provide a secure connection which is both encrypted and authenticated. It is therefore important to support HTTPS for the security benefits.

Impact

When it is enabled, every incoming HTTP request is redirected to the HTTPS port. This means an extra level of security will be added to the HTTP requests made to the app.

Audit Procedure

Using Azure Portal

1. Login to Azure Portal using https://portal.azure.com
2. Go to App Services
3. For each App Service
4. Under Setting section, click on Configuration
5. Under the General Settings tab, ensure that HTTPS Only is set to On under Platform Settings

Using Azure CLI

To check HTTPS-only traffic value for an existing app, run the following command:

az webapp show --resource-group <RESOURCE_GROUP_NAME> --name <APP_NAME> --query httpsOnly

The output should return true if HTTPS-only traffic value is set to On.

Using Azure PowerShell

List all the web apps configured within the subscription:

Get-AzWebApp | Select-Object ResourceGroup, Name, HttpsOnly

For each web app review the HttpsOnly setting and make sure it is set to True.

Expected Result

The httpsOnly setting should return true.

Remediation

Using Azure Portal

1. Login to Azure Portal using https://portal.azure.com
2. Go to App Services
3. For each App Service
4. Under Setting section, click on Configuration
5. Under the General Settings tab, set HTTPS Only to On under Platform Settings

Using Azure CLI

To set HTTPS-only traffic value for an existing app, run the following command:

az webapp update --resource-group <RESOURCE_GROUP_NAME> --name <APP_NAME> --set httpsOnly=true

Using Azure PowerShell

Set-AzWebApp -ResourceGroupName <RESOURCE_GROUP_NAME> -Name <APP_NAME> -HttpsOnly $true

Default Value

HTTPS Only is disabled by default.

References

1. https://learn.microsoft.com/en-us/azure/app-service/overview-security#https-and-certificates
2. https://learn.microsoft.com/en-us/security/benchmark/azure/security-controls-v3-data-protection#dp-3-encrypt-sensitive-data-in-transit
3. https://techcommunity.microsoft.com/t5/azure-paas-blog/enable-https-setting-on-azure-app-service-using-azure-policy/ba-p/3286603
4. https://learn.microsoft.com/en-us/cli/azure/webapp
5. https://learn.microsoft.com/en-us/powershell/module/az.websites/get-azwebapp
6. https://learn.microsoft.com/en-us/powershell/module/az.websites/set-azwebapp

Profile

Level 1 | Automated