How do I filter input to mitigate buffer overflow attacks using AWS WAF?

In this guide, we will create an AWS Web Application Firewall (WAF) to filter input and mitigate buffer overflow attacks. AWS WAF allows you to define rules to protect your web applications from common web exploits.

We will create a WAF WebACL with a rule that uses a ByteMatchSet to inspect incoming requests and block those that exceed a certain length, which is a common indicator of buffer overflow attacks.

import * as pulumi from "@pulumi/pulumi";
import * as aws from "@pulumi/aws";

// Create a ByteMatchSet to filter requests
const byteMatchSet = new aws.waf.ByteMatchSet("byteMatchSet", {
    name: "byteMatchSet",
    byteMatchTuples: [{
        fieldToMatch: {
            type: "BODY", // Inspect the body of the request
        },
        targetString: "A".repeat(1000), // Example target string to match
        textTransformation: "NONE",
        positionalConstraint: "CONTAINS",
    }],
});

// Create a WAF rule that uses the ByteMatchSet
const wafRule = new aws.waf.Rule("wafRule", {
    name: "wafRule",
    metricName: "wafRuleMetric",
    predicates: [{
        dataId: byteMatchSet.id,
        negated: false,
        type: "ByteMatch",
    }],
});

// Create a WAF WebACL and associate the rule with it
const webAcl = new aws.waf.WebAcl("webAcl", {
    name: "webAcl",
    metricName: "webAclMetric",
    defaultAction: {
        type: "ALLOW", // Allow requests by default
    },
    rules: [{
        action: {
            type: "BLOCK", // Block requests that match the rule
        },
        priority: 1,
        ruleId: wafRule.id,
    }],
});

// Export the WebACL ID
export const webAclId = webAcl.id;

Key Points:

We created a ByteMatchSet to define the pattern to match in the request body.
We created a WAF Rule to use the ByteMatchSet for filtering.
We created a WAF WebACL to apply the rule and block matching requests.

Summary:

We successfully created an AWS WAF WebACL with a rule that filters input to mitigate buffer overflow attacks. This setup inspects the request body and blocks requests that match a specific pattern, helping to protect your web application from potential exploits.

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