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Event Information

  • The CreateSizeConstraintSet event in AWS WAF refers to the creation of a size constraint set, which is a collection of size constraint rules used to protect web applications from attacks related to the size of HTTP requests or responses.
  • Size constraint rules within a size constraint set define the maximum or minimum size limits for specific parts of an HTTP request or response, such as headers, query strings, or body content.
  • This event indicates that a new size constraint set has been created, and it can be further configured with specific size constraint rules to enforce size limits and protect against potential attacks on web applications.

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Examples

  • Inadequate size constraint: If the size constraint set is not properly configured, it may allow requests that exceed the desired size limit to pass through, potentially leading to security vulnerabilities such as buffer overflow attacks or denial of service attacks.

  • False positives: If the size constraint set is too strict, it may flag legitimate requests as malicious, resulting in false positives. This can impact the availability of the application and cause inconvenience to legitimate users.

  • Incomplete coverage: If the size constraint set does not cover all the necessary areas of the application, it may leave certain parts vulnerable to attacks. For example, if only the request body size is constrained but not the query string or headers, an attacker may exploit this gap to bypass security measures.

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Remediation

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Using Console

  1. Identify the specific AWS WAF rule that needs to be remediated based on the examples provided.

    • Log in to the AWS Management Console and navigate to the AWS WAF service.
    • Select the appropriate web ACL that contains the rule that needs to be remediated.

  2. Modify the AWS WAF rule to address the identified issue.

    • Within the selected web ACL, locate the rule that needs to be remediated.
    • Click on the rule to access its configuration settings.
    • Adjust the rule’s parameters or conditions to align with the desired remediation action.
    • Save the changes made to the rule.

  3. Test and monitor the remediated AWS WAF rule.

    • Deploy the updated web ACL to the appropriate AWS resources (e.g., Amazon CloudFront distribution, Application Load Balancer).
    • Monitor the traffic and behavior of the protected resources to ensure that the remediated rule is functioning as expected.
    • Continuously monitor and analyze the AWS WAF logs and metrics to identify any potential issues or anomalies that may require further remediation.

Note: The specific steps may vary depending on the AWS WAF console interface and the nature of the rule being remediated. It is important to refer to the AWS documentation for detailed instructions and best practices.

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Using CLI

  1. To remediate a specific rule in AWS WAF using AWS CLI, you can use the update-rule command. For example, if you want to update the rule with the rule ID “12345678-1234-1234-1234-123456789012” in a WebACL named “MyWebACL”, you can use the following command:
aws wafv2 update-rule --name MyWebACL --scope REGIONAL --id 12345678-1234-1234-1234-123456789012 --action ALLOW --override-action NONE

This command updates the specified rule to allow the traffic and removes any overriding actions.

  1. To remediate a rate-based rule in AWS WAF using AWS CLI, you can use the update-rate-based-rule command. For example, if you want to update the rate-based rule with the rule ID “12345678-1234-1234-1234-123456789012” in a WebACL named “MyWebACL”, you can use the following command:
aws wafv2 update-rate-based-rule --name MyWebACL --scope REGIONAL --id 12345678-1234-1234-1234-123456789012 --rate-key IP --rate-limit 1000

This command updates the specified rate-based rule to limit the requests per IP to 1000.

  1. To remediate a managed rule group in AWS WAF using AWS CLI, you can use the update-managed-rule-set-version command. For example, if you want to update the managed rule group with the ARN “arn:aws:wafv2:us-west-2:123456789012:managed-rule-set/aws-managed/gbqj2j5k5k-owasp-top-10” to the latest available version, you can use the following command:
aws wafv2 update-managed-rule-set-version --name gbqj2j5k5k-owasp-top-10 --scope REGIONAL --vendor-name aws-managed --managed-rule-set-id gbqj2j5k5k-owasp-top-10

This command updates the specified managed rule group to the latest available version.

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Using Python

  1. Example 1: Blocking IP addresses with AWS WAF using Python:
    • Use the AWS SDK for Python (Boto3) to interact with AWS WAF.
    • Write a Python script to retrieve the IP addresses that need to be blocked.
    • Use the create_ip_set method to create an IP set in AWS WAF.
    • Use the update_ip_set method to add the IP addresses to the IP set.
    • Use the update_web_acl method to associate the IP set with the desired web ACL.
import boto3

# Create AWS WAF client
waf_client = boto3.client('waf')

# Retrieve IP addresses to block
ip_addresses = ['192.0.2.1', '203.0.113.2']

# Create IP set
response = waf_client.create_ip_set(
    Name='BlockedIPSet',
    ChangeToken='CHANGE_TOKEN'
)

# Add IP addresses to IP set
response = waf_client.update_ip_set(
    IPSetId='IP_SET_ID',
    ChangeToken='CHANGE_TOKEN',
    Updates=[
        {
            'Action': 'INSERT',
            'IPSetDescriptor': {
                'Type': 'IPV4',
                'Value': ip_address
            }
        }
        for ip_address in ip_addresses
    ]
)

# Associate IP set with web ACL
response = waf_client.update_web_acl(
    WebACLId='WEB_ACL_ID',
    ChangeToken='CHANGE_TOKEN',
    Updates=[
        {
            'Action': 'INSERT',
            'ActivatedRule': {
                'Priority': 1,
                'RuleId': 'BLOCK_RULE_ID',
                'Action': {
                    'Type': 'BLOCK'
                }
            }
        }
    ]
)
  1. Example 2: Enabling AWS WAF rate-based rules using Python:
    • Use the AWS SDK for Python (Boto3) to interact with AWS WAF.
    • Write a Python script to enable rate-based rules for a specific web ACL.
    • Use the create_rate_based_rule method to create a rate-based rule.
    • Use the update_web_acl method to associate the rate-based rule with the desired web ACL.
import boto3

# Create AWS WAF client
waf_client = boto3.client('waf')

# Create rate-based rule
response = waf_client.create_rate_based_rule(
    Name='RateBasedRule',
    MetricName='RateBasedRule',
    RateKey='IP',
    RateLimit=1000,
    ChangeToken='CHANGE_TOKEN'
)

# Associate rate-based rule with web ACL
response = waf_client.update_web_acl(
    WebACLId='WEB_ACL_ID',
    ChangeToken='CHANGE_TOKEN',
    Updates=[
        {
            'Action': 'INSERT',
            'ActivatedRule': {
                'Priority': 1,
                'RuleId': 'RATE_BASED_RULE_ID',
                'Action': {
                    'Type': 'COUNT'
                }
            }
        }
    ]
)
  1. Example 3: Creating AWS WAF rules to block SQL injection using Python:
    • Use the AWS SDK for Python (Boto3) to interact with AWS WAF.
    • Write a Python script to create AWS WAF rules to block SQL injection.
    • Use the create_rule method to create a rule for SQL injection.
    • Use the update_web_acl method to associate the rule with the desired web ACL.
import boto3

# Create AWS WAF client
waf_client = boto3.client('waf')

# Create rule for SQL injection
response = waf_client.create_rule(
    Name='SQLInjectionRule',
    MetricName='SQLInjectionRule',
    ChangeToken='CHANGE_TOKEN',
    Predicates=[
        {
            'DataId': 'SQL_INJECTION_DATA_ID',
            'Negated': False,
            'Type': 'SQLi'
        }
    ]
)

# Associate rule with web ACL
response = waf_client.update_web_acl(
    WebACLId='WEB_ACL_ID',
    ChangeToken='CHANGE_TOKEN',
    Updates=[
        {
            'Action': 'INSERT',
            'ActivatedRule': {
                'Priority': 1,
                'RuleId': 'SQL_INJECTION_RULE_ID',
                'Action': {
                    'Type': 'BLOCK'
                }
            }
        }
    ]
)