Cis Azure Compute 2.1.8

Ensure 'Minimum Inbound TLS Version' is set to '1.2' or higher

Description

The TLS (Transport Layer Security) protocol secures the transmission of data over the internet using standard encryption technology. App Service apps use TLS 1.2 for the Minimum Inbound TLS Version by default and allow for the use of TLS versions 1.0, 1.1, and 1.3. NIST strongly suggests the use of TLS 1.2 and recommends the adoption of TLS 1.3.

Rationale

TLS 1.0 and 1.1 are outdated and vulnerable to security risks. Since TLS 1.2 and TLS 1.3 provide enhanced security and improved performance, it is highly recommended to use TLS 1.2 or higher whenever possible.

Impact

Using the latest TLS version may affect compatibility with clients and backend services.

Audit Procedure

Using Azure Portal

1. Go to App Services.
2. Click the name of an app.
3. Under Settings, click Configuration.
4. In the General settings pane, under Platform settings, ensure that Minimum Inbound TLS Version is set to 1.2 or higher.
5. Repeat steps 1-4 for each app.

Using Azure CLI

Run the following command to list apps:

az webapp list

For each app, run the following command to get the TLS version setting:

az webapp config show --resource-group <resource-group-name> --name <app-name> --query minTlsVersion

Ensure that "1.2" or higher is returned.

Using Azure PowerShell

Run the following command to list apps:

Get-AzWebApp

Run the following command to get the app in a resource group with a given name:

$app = Get-AzWebApp -ResourceGroupName <resource-group-name> -Name <app-name>

Run the following command to get the TLS version setting:

$app.SiteConfig.MinTlsVersion

Ensure that the command returns 1.2 or higher. Repeat for each app.

Expected Result

The minimum TLS version should be 1.2 or higher.

Remediation

Using Azure Portal

1. Go to App Services.
2. Click the name of an app.
3. Under Settings, click Configuration.
4. In the General settings pane, under Platform settings, click the drop-down next to Minimum Inbound TLS Version and select 1.2 or higher.
5. Click Save.
6. Click Continue.
7. Repeat steps 1-6 for each app requiring remediation.

Using Azure CLI

For each app requiring remediation, run the following command to update the TLS version:

az webapp config set --resource-group <resource-group-name> --name <app-name> --min-tls-version <1.2|1.3>

Using Azure PowerShell

For each app requiring remediation, run the following command to update the TLS version:

Set-AzWebApp -ResourceGroupName <resource-group-name> -Name <app-name> -MinTlsVersion <1.2|1.3>

Default Value

By default, TLS version is set to 1.2.

References

1. https://learn.microsoft.com/en-us/azure/app-service/configure-ssl-bindings#how-can-i-change-the-minimum-tls-versions-for-the-app
2. https://learn.microsoft.com/en-us/security/benchmark/azure/mcsb-data-protection#dp-3-encrypt-sensitive-data-in-transit
3. https://learn.microsoft.com/en-us/security/benchmark/azure/mcsb-network-security#ns-8-detect-and-disable-insecure-services-and-protocols
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
7. https://csrc.nist.gov/news/2019/nist-publishes-sp-800-52-revision-2

Profile

Level 1 | Automated