searchString

A string value that you want WAF to search for. WAF searches only in the part of web requests that you designate for inspection in FieldToMatch. The maximum length of the value is 200 bytes.

Valid values depend on the component that you specify for inspection in FieldToMatch:

• Method: The HTTP method that you want WAF to search for. This indicates the type of operation specified in the request.

• UriPath: The value that you want WAF to search for in the URI path, for example, /images/daily-ad.jpg.

• JA3Fingerprint: Available for use with Amazon CloudFront distributions and Application Load Balancers. Match against the request's JA3 fingerprint. The JA3 fingerprint is a 32-character hash derived from the TLS Client Hello of an incoming request. This fingerprint serves as a unique identifier for the client's TLS configuration. You can use this choice only with a string match ByteMatchStatement with the PositionalConstraint set to EXACTLY. You can obtain the JA3 fingerprint for client requests from the web ACL logs. If WAF is able to calculate the fingerprint, it includes it in the logs. For information about the logging fields, see Log fields in the WAF Developer Guide.

• HeaderOrder: The list of header names to match for. WAF creates a string that contains the ordered list of header names, from the headers in the web request, and then matches against that string.

If SearchString includes alphabetic characters A-Z and a-z, note that the value is case sensitive.

If you're using the WAF API

Specify a base64-encoded version of the value. The maximum length of the value before you base64-encode it is 200 bytes.

For example, suppose the value of Type is HEADER and the value of Data is User-Agent. If you want to search the User-Agent header for the value BadBot, you base64-encode BadBot using MIME base64-encoding and include the resulting value, QmFkQm90, in the value of SearchString.

If you're using the CLI or one of the Amazon Web Services SDKs

The value that you want WAF to search for. The SDK automatically base64 encodes the value.