Cis Azure Compute 2.2.7

Ensure 'HTTPS Only' is set to 'On'

Description

Azure App Service allows deployment slots to run under both HTTP and HTTPS by default. Deployment slots 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 deployment slot.

Audit Procedure

Using Azure Portal

1. Go to App Services.
2. Click the name of an app.
3. Under Deployment, click Deployment slots.
4. Click the name of a deployment slot.
5. Under Settings, click Configuration.
6. In the General settings tab, under Platform settings, ensure that HTTPS Only is set to On.
7. Repeat steps 1-6 for each app and deployment slot.

Using Azure CLI

Run the following command to list apps:

az webapp list

For each app, run the following command to list deployment slots:

az webapp deployment slot list --resource-group <resource-group-name> --name <app-name>

For each deployment slot, ensure that httpsOnly is set to true.

Using Azure PowerShell

Run the following command to list apps:

Get-AzWebApp

Run the following command to list deployment slots for an app:

Get-AzWebAppSlot -ResourceGroupName <resource-group-name> -Name <app-name>

Run the following command to get the deployment slot with a given name:

$slot = Get-AzWebAppSlot -ResourceGroupName <resource-group-name> -Name <app-name> -Slot <deployment-slot-name>

Run the following command to get the HTTPS setting for the deployment slot:

$slot.httpsOnly

Ensure that the command returns True. Repeat for each app and deployment slot.

Expected Result

The httpsOnly property should return True, indicating that HTTPS-only traffic is enforced.

Remediation

Using Azure Portal

1. Go to App Services.
2. Click the name of an app.
3. Under Deployment, click Deployment slots.
4. Click the name of a deployment slot.
5. Under Settings, click Configuration.
6. In the General settings tab, under Platform settings, next to HTTPS Only, select the radio button next to On.
7. Click Save.
8. Click Continue.
9. Repeat steps 1-8 for each app and deployment slot requiring remediation.

Using Azure CLI

For each deployment slot requiring remediation, run the following command to enable HTTPS Only:

az resource update --resource-group <resource-group-name> --name <app-name>/slots/<deployment-slot-name> --resource-type "Microsoft.Web/sites" --set properties.httpsOnly=true

Using Azure PowerShell

For each deployment slot requiring remediation, run the following command to enable HTTPS Only:

Set-AzWebAppSlot -ResourceGroupName <resource-group-name> -Name <app-name> -Slot <deployment-slot-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-azwebappslot
6. https://learn.microsoft.com/en-us/powershell/module/az.websites/set-azwebappslot
7. https://learn.microsoft.com/en-us/cli/azure/resource

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