ByteMatchStatement

A rule statement that defines a string match search for AWS WAF to apply to web requests. The byte match statement provides the bytes to search for, the location in requests that you want AWS WAF to search, and other settings. The bytes to search for are typically a string that corresponds with ASCII characters. In the AWS WAF console and the developer guide, this is called a string match statement.

FieldToMatch

The part of the web request that you want AWS WAF to inspect.

Type: FieldToMatch object

Required: Yes

PositionalConstraint

The area within the portion of the web request that you want AWS WAF to search for SearchString. Valid values include the following:

CONTAINS

The specified part of the web request must include the value of SearchString, but the location doesn't matter.

CONTAINS_WORD

The specified part of the web request must include the value of SearchString, and SearchString must contain only alphanumeric characters or underscore (A-Z, a-z, 0-9, or _). In addition, SearchString must be a word, which means that both of the following are true:

SearchString is at the beginning of the specified part of the web request or is preceded by a character other than an alphanumeric character or underscore (_). Examples include the value of a header and ;BadBot.
SearchString is at the end of the specified part of the web request or is followed by a character other than an alphanumeric character or underscore (_), for example, BadBot; and -BadBot;.

EXACTLY

The value of the specified part of the web request must exactly match the value of SearchString.

STARTS_WITH

The value of SearchString must appear at the beginning of the specified part of the web request.

ENDS_WITH

The value of SearchString must appear at the end of the specified part of the web request.

Type: String

Valid Values: EXACTLY | STARTS_WITH | ENDS_WITH | CONTAINS | CONTAINS_WORD

Required: Yes

SearchString

A string value that you want AWS WAF to search for. AWS 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 AWS WAF to search for. This indicates the type of operation specified in the request.
UriPath: The value that you want AWS 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 AWS WAF is able to calculate the fingerprint, it includes it in the logs. For information about the logging fields, see Log fields in the AWS WAF Developer Guide.
HeaderOrder: The list of header names to match for. AWS 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 AWS 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 AWS CLI or one of the AWS SDKs

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

Type: Base64-encoded binary data object

Required: Yes

TextTransformations

Text transformations eliminate some of the unusual formatting that attackers use in web requests in an effort to bypass detection. Text transformations are used in rule match statements, to transform the FieldToMatch request component before inspecting it, and they're used in rate-based rule statements, to transform request components before using them as custom aggregation keys. If you specify one or more transformations to apply, AWS WAF performs all transformations on the specified content, starting from the lowest priority setting, and then uses the transformed component contents.

Type: Array of TextTransformation objects

Array Members: Minimum number of 1 item.

Required: Yes

ByteMatchStatement

Contents

See Also