Install the Limit Payload Size integration
Install Limit Payload Size from Azion Marketplace and run it on a firewall to deny requests whose Content-Length exceeds a limit you set.
You install the Limit Payload Size integration from Azion Marketplace and run it on a Firewall, from Azion Console. The function evaluates request data and denies payloads that exceed a limit you set. It checks the payload size through the Content-Length header, not the body: the header is required, so reading it is safe, it protects against changes to the header’s value, and it performs better than reading the body.
Five objects have to exist before a request is checked: the installed function, a firewall carrying the Functions module, a function instance holding the limit, a Rules Engine rule with the Run Function behavior, and a workload deployment bound to the firewall. Each section below creates one of them.
Prerequisites
- An Azion account. To sign in, refer to How to access Azion Console.
- An application served by a workload, whose deployment you bind to the firewall in the last section.
- The Azion CLI installed and authorized, for the last section.
- Turning on a product or a module can generate usage costs. For more information, refer to Pricing.
Install the integration
The function is installed once per account. To install it:
Access Azion Console > Marketplace.
Enter Limit Payload Size in the Search on Marketplace field, then select the integration’s card. Browsing the cards and the categories reaches the same page.
The card shows Successfully installed! and Latest version installed!, and the function appears in the Function list of the Create Instance drawer.
Create the firewall
The firewall is where the function is instanced and where the rule that runs it lives. To create one:
Access Azion Console > Firewalls, then create a firewall.
In the General section, enter a Name. For example: limit-payload-firewall.
In the Modules section, turn on the Functions switch.
The firewall shows a Functions Instances tab while the Functions module stays on. To use an existing firewall instead, turn on its Functions module and save it. For every setting on this form, refer to Set a firewall’s main settings.
Create the function instance
The instance holds the maximum payload size that the function accepts. To create it:
In Firewalls, select your firewall, then select the Functions Instances tab.
A firewall that has no instance shows the same action as Function Instance. The Create Instance drawer opens.
In Name, enter a name. For example: limit-payload-size.
In Function, select the Limit Payload Size function. The list holds only the functions that run on a firewall.
In Arguments, the editor is prefilled with the integration’s default arguments in JSON. Set the limit, as the next section describes.
The instance is listed in the Functions Instances tab.
Arguments
The instance takes one argument:
max_content_length is the maximum payload size that the function accepts:
- The value accepts bytes, kilobytes, and megabytes.
- A value without a unit is read as bytes.
- Without an argument, the function bypasses the execution.
- A payload larger than the limit gets a
403error.
Create the rule
The instance checks nothing until a rule runs it. A Rules Engine for Firewall rule selects the requests that reach the instance, through a Run Function behavior. To create the rule:
In Firewalls, select your firewall, then select the Rules Engine tab.
In Name, enter a name. For example: Run Limit Payload Size.
In the Criteria section, select the domains that run the integration. For example: if Host matches yourdomain.com.
In the Behaviors section, select Run Function, then select the instance by the name you gave it.
The firewall runs the instance on every request to the domain in the criterion.
Bind the firewall to the workload
The binding is on the workload’s deployment, so create a deployment that names both the application and the firewall:
The command prints the id of the new deployment:
Requests to the workload’s domain reach the firewall, and the rule runs the Limit Payload Size instance on each one.