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Manual Chapter: Signature Options
Manual Chapter
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Keyword summary

The keywords, generally referred to as scopes, are used in signatures to search for specific fixed strings in different parts of the input. This table summarizes the keywords that you can use in signatures, including the reference keyword, which is not a scope.

Keyword Use
content Matches the full content.
uricontent Matches the URI, including the query string (unless using the objonly modifier).
headercontent Matches the HTTP header.
valuecontent Matches an alphanumeric user-input parameter (or an extra-normalized parameter, if using the norm modifier); used for parameter values, XML objects, JSON/GWT objects, XML/JSON parameters, and cookies. When a signature includes the valuecontent keyword, XML payloads are examined.
Note: The valuecontent parameter replaces the paramcontent parameter that was used in Application Security Manager™ versions prior to 10.0.
reference Provides an external link to documentation and other information for the rule.

Modifiers summary

The modifiers alter the meaning of keywords used in a signature. This table summarizes the modifiers.

Modifier Usage
depth Specifies that the preceding keyword is found not more than X bytes into the appropriate scope. This is an absolute modifier.
distance Specifies that the preceding keyword is found not less than X bytes after the prior keyword. This is a relative modifier.
gwtonly Applies the signature if the request contains Google Web Toolkit (GWT) content. Used with the valuecontent keyword.
httponly Matches on parameters when used with the valuecontent keyword.
jsononly Applies the signature if the request contains JSON content. Used with the valuecontent keyword.
nocase Makes the preceding keyword not case-sensitive.
norm Matches the preceding parameter to which additional normalizations have been applied.
objonly Limits the scope of the preceding uricontent keyword to the URI part only.
offset Specifies that the preceding keyword is found not less than X bytes into the appropriate scope. This is an absolute modifier.
plaintextonly Applies the signature if the request contains plain text content. Used with the valuecontent keyword.
within Specifies that the preceding keyword is found not more than X bytes after the prior keyword. This is a relative modifier.
xmlonly Applies the signature if the request contains XML content. Used with the valuecontent keyword.

Regular expression scopes

Scopes define the portion of a request or response that the regular expression keyword (pcre, re2, ipp) applies to. This table lists the rule flags to use for different scopes in an attack or bot signature.

Rule flag Scope
C Full content of the request or response body
U URI, including query string
O URL only (URI without query string)
H HTTP headers
V HTTP parameters in query string or POST data
N HTTP parameters with additional normalizations
Note:

In signatures, rules for responses can contain only rule options and modifiers that apply to the entire content of the response. In other words, for response rules, you can use the content and reference keywords, and any applicable modifiers for these keywords. You can also use the pcre, re2, or ipp rule options for responses, as long as you do not use a scope modifier for them.

Keyword and flag compatibility

These tables describe the compatibility between keyword rule options themselves, and between keywords and regular expression (regex) flags. You can refer to these tables when developing attack or bot signatures to understand which keywords and flags can be used together. "Valid" means that you can use the combination together in a signature. "Invalid" means you cannot use the two together.

Keywords/Keywords content uricontent headercontent paramcontent valuecontent
content Valid Valid Valid Invalid Invalid
uricontent Valid Valid Valid Invalid Invalid
headercontent Valid Valid Valid Invalid Invalid
paramcontent Invalid Invalid Invalid Valid Invalid
valuecontent Invalid Invalid Invalid Invalid Valid
Keywords/Flags None U O H P N V
content Valid Valid Valid Valid Invalid Invalid Invalid
uricontent Valid Valid Valid Valid Invalid Invalid Invalid
headercontent Valid Valid Valid Valid Invalid Invalid Invalid
paramcontent Invalid Invalid Invalid Invalid Valid Valid Invalid
valuecontent Invalid Invalid Invalid Invalid Invalid Invalid Valid
Flags/Flags None U O H P N V
None Valid Valid Valid Valid Invalid Invalid Invalid
U Valid Valid Valid Valid Invalid Invalid Invalid
O Valid Valid Valid Valid Invalid Invalid Invalid
H Valid Valid Valid Valid Invalid Invalid Invalid
N Invalid Invalid Invalid Invalid Valid Valid Invalid
V (See note) Invalid Invalid Invalid Invalid Invalid Invalid Valid
Note: You should use V (with httponly if necessary) instead of the deprecated P regex flag.

About normalization

For the URI and parameter scopes, the system always applies a normalization process before applying the rule options to the signature. For parameters, you can include the norm modifier with the valuecontent keyword to cause the system to perform additional normalizations to make the content more regular. The additional parameter normalizations also help mitigate common evasion techniques used in XSS, SQL-Injection, and Command Execution attacks. Therefore, it is a good idea to use additional normalizations, by default.

Composite rules

You can combine rule options together to form composite rules. By using keywords combined with modifiers, the rule options merge to form a single assertion. Rule options are combined using an implied AND operator; this makes it so that all conditions in the rule must be met in order to satisfy the rule as a whole.

Consider the following points when combining rule options:

  • You can combine different scopes within one rule as long as you do not use any relative modifiers. For example, this rule is invalid because it includes two scopes (content and uricontent), and within, a relative modifier:
       content:"ABC"; uricontent:"XYZ"; within:10;
  • You cannot combine the valuecontent, pcre P, or re2 P rule options with other scope keywords. The parameter rule options must be the only scope keywords in their respective rules. You can, however, combine the parameter keywords with additional valuecontent, pcre P, or re2 P keywords, including those with the norm modifier (or N, for pcre or re2).
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