AWS::WAFv2::WebACL JsonBody - AWS CloudFormation
SyntaxPropertiesExamples

AWS::WAFv2::WebACL JsonBody

Inspect the body of the web request as JSON. The body immediately follows the request headers.

This is used to indicate the web request component to inspect, in the FieldToMatch specification.

Use the specifications in this object to indicate which parts of the JSON body to inspect using the rule's inspection criteria. AWS WAF inspects only the parts of the JSON that result from the matches that you indicate.

Example JSON: "JsonBody": { "MatchPattern": { "All": {} }, "MatchScope": "ALL" }

For additional information about this request component option, see JSON body in the AWS WAF Developer Guide.

Syntax

To declare this entity in your AWS CloudFormation template, use the following syntax:

JSON

{
  "InvalidFallbackBehavior" : String,
  "MatchPattern" : JsonMatchPattern,
  "MatchScope" : String,
  "OversizeHandling" : String
}

Properties

InvalidFallbackBehavior

What AWS WAF should do if it fails to completely parse the JSON body. The options are the following:

  • EVALUATE_AS_STRING - Inspect the body as plain text. AWS WAF applies the text transformations and inspection criteria that you defined for the JSON inspection to the body text string.

  • MATCH - Treat the web request as matching the rule statement. AWS WAF applies the rule action to the request.

  • NO_MATCH - Treat the web request as not matching the rule statement.

If you don't provide this setting, AWS WAF parses and evaluates the content only up to the first parsing failure that it encounters.

Note

AWS WAF parsing doesn't fully validate the input JSON string, so parsing can succeed even for invalid JSON. When parsing succeeds, AWS WAF doesn't apply the fallback behavior. For more information, see JSON body in the AWS WAF Developer Guide.

Required: No

Type: String

Allowed values: MATCH | NO_MATCH | EVALUATE_AS_STRING

Update requires: No interruption

MatchPattern

The patterns to look for in the JSON body. AWS WAF inspects the results of these pattern matches against the rule inspection criteria.

Required: Yes

Type: JsonMatchPattern

Update requires: No interruption

MatchScope

The parts of the JSON to match against using the MatchPattern. If you specify ALL, AWS WAF matches against keys and values.

All does not require a match to be found in the keys and a match to be found in the values. It requires a match to be found in the keys or the values or both. To require a match in the keys and in the values, use a logical AND statement to combine two match rules, one that inspects the keys and another that inspects the values.

Required: Yes

Type: String

Allowed values: ALL | KEY | VALUE

Update requires: No interruption

OversizeHandling

What AWS WAF should do if the body is larger than AWS WAF can inspect.

AWS WAF does not support inspecting the entire contents of the web request body if the body exceeds the limit for the resource type. When a web request body is larger than the limit, the underlying host service only forwards the contents that are within the limit to AWS WAF for inspection.

  • For Application Load Balancer and AWS AppSync, the limit is fixed at 8 KB (8,192 bytes).

  • For CloudFront, API Gateway, Amazon Cognito, App Runner, and Verified Access, the default limit is 16 KB (16,384 bytes), and you can increase the limit for each resource type in the web ACL AssociationConfig, for additional processing fees.

The options for oversize handling are the following:

  • CONTINUE - Inspect the available body contents normally, according to the rule inspection criteria.

  • MATCH - Treat the web request as matching the rule statement. AWS WAF applies the rule action to the request.

  • NO_MATCH - Treat the web request as not matching the rule statement.

You can combine the MATCH or NO_MATCH settings for oversize handling with your rule and web ACL action settings, so that you block any request whose body is over the limit.

Default: CONTINUE

Required: No

Type: String

Allowed values: CONTINUE | MATCH | NO_MATCH

Update requires: No interruption

Examples

Set the JSON body specification

The following shows an example JSON body field to match specification.

YAML

FieldToMatch:
  JsonBody:
    MatchPattern:
      IncludedPaths:
      - "/dogs/0/name"
      - "/cats/0/name"
    MatchScope: ALL
    InvalidFallbackBehavior: EVALUATE_AS_STRING 
    OversizeHandling: MATCH

JSON

"FieldToMatch": {
  "JsonBody": {
    "MatchPattern": {
      "IncludedPaths": [
        "/dogs/0/name",
        "/cats/0/name"
      ]
    },
    "MatchScope": "ALL",
    "InvalidFallbackBehavior": "EVALUATE_AS_STRING",
    "OversizeHandling": "MATCH" 
  }
}