Cis Azure Compute 2.3.5

Ensure 'HTTP version' is set to '2.0' (if in use)

Description

Periodically, newer versions are released for HTTP, either due to security flaws or to include additional functionalities. Using the latest HTTP version allows apps to take advantage of security fixes, if any, and/or new functionalities of the newer version.

Rationale

Newer versions may contain security enhancements and additional functionalities. Using the latest version is recommended in order to take advantage of enhancements and new capabilities. With each software installation, organizations need to determine if a given update meets their requirements. They must also verify the compatibility and support provided for any additional software against the update revision that is selected.

HTTP 2.0 has additional performance improvements for the head-of-line blocking problem of the old HTTP version, header compression, and request prioritization. HTTP 2.0 no longer supports HTTP 1.1's chunked transfer encoding mechanism, as it provides its own, more efficient mechanisms for data streaming.

Impact

Most modern browsers support the HTTP/2 protocol over TLS only, while non-encrypted traffic continues to use HTTP/1.1. To ensure that client browsers connect to your app with HTTP/2, either purchase an App Service Certificate for your app's custom domain or bind a third-party certificate.

NOTE: HTTP/2 cannot be used in tandem with mutual authentication or client certificates.

Audit Procedure

Using Azure Portal

1. Go to App Services or Function App.
2. Click the name of a function app.
3. Under Settings, click Configuration.
4. In the General settings pane, under Platform settings, ensure that HTTP version is set to 2.0.
5. Repeat steps 1-4 for each function app.

Using Azure CLI

Run the following command to list function apps:

az functionapp list

For each function app, run the following command to get the http20Enabled setting:

az functionapp config show --resource-group <resource-group-name> --name <function-app-name> --query http20Enabled

Ensure that true is returned.

Using Azure PowerShell

Run the following command to list function apps:

Get-AzFunctionApp

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

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

Run the following command to get the Http20Enabled setting:

$app.SiteConfig.Http20Enabled

Ensure that True is returned. Repeat for each function app.

Expected Result

The http20Enabled setting should return true.

Remediation

Using Azure Portal

1. Go to App Services or Function App.
2. Click the name of a function app.
3. Under Settings, click Configuration.
4. In the General settings pane, under Platform settings, set HTTP version to 2.0.
5. Click Save.
6. Click Continue.
7. Repeat steps 1-6 for each function app requiring remediation.

Using Azure CLI

For each function app requiring remediation, run the following command to enable http20Enabled:

az functionapp config set --resource-group <resource-group-name> --name <app-name> --http20-enabled true

Default Value

By default, HTTP version is set to 1.1.

References

1. https://learn.microsoft.com/en-us/azure/app-service/configure-common#general-settings
2. https://learn.microsoft.com/en-us/security/benchmark/azure/mcsb-posture-vulnerability-management#pv-3-define-and-establish-secure-configurations-for-compute-resources
3. https://learn.microsoft.com/en-us/security/benchmark/azure/mcsb-posture-vulnerability-management#pv-6-rapidly-and-automatically-remediate-vulnerabilities
4. https://learn.microsoft.com/en-us/cli/azure/functionapp
5. https://learn.microsoft.com/en-us/powershell/module/az.functions/get-azfunctionapp

Profile

Level 1 | Automated