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/projectdiscovery/dsl"
)

func main() {
	// Define the data to evaluate
	data := map[string]interface{}{
		"username": "johndoe",
		"email":    "[email protected]",
		"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

Helper function	Description	Example	Output
aes_gcm(key, plaintext interface{}) []byte	AES GCM encrypts a string with key	{{hex_encode(aes_gcm("AES256Key-32Characters1234567890", "exampleplaintext"))}}	ec183a153b8e8ae7925beed74728534b57a60920c0b009eaa7608a34e06325804c096d7eebccddea3e5ed6c4
base64(src interface{}) string	Base64 encodes a string	base64("Hello")	SGVsbG8=
base64_decode(src interface{}) []byte	Base64 decodes a string	base64_decode("SGVsbG8=")	Hello
base64_py(src interface{}) string	Encodes string to base64 like python (with new lines)	base64_py("Hello")	SGVsbG8=\n
bin_to_dec(binaryNumber number | string) float64	Transforms the input binary number into a decimal format	bin_to_dec("0b1010") bin_to_dec(1010)	10
compare_versions(versionToCheck string, constraints ...string) bool	Compares the first version argument with the provided constraints	compare_versions('v1.0.0', '>v0.0.1', '<v1.0.1')	true
concat(arguments ...interface{}) string	Concatenates the given number of arguments to form a string	concat("Hello", 123, "world)	Hello123world
contains(input, substring interface{}) bool	Verifies if a string contains a substring	contains("Hello", "lo")	true
contains_all(input interface{}, substrings ...string) bool	Verifies if any input contains all of the substrings	contains_all("Hello everyone", "lo", "every")	true
contains_any(input interface{}, substrings ...string) bool	Verifies if an input contains any of substrings	contains_any("Hello everyone", "abc", "llo")	true
date_time(dateTimeFormat string, optionalUnixTime interface{}) string	Returns the formatted date time using simplified or go style layout for the current or the given unix time	date_time("%Y-%M-%D %H:%m") date_time("%Y-%M-%D %H:%m", 1654870680) date_time("2006-01-02 15:04", unix_time())	2022-06-10 14:18
dec_to_hex(number number | string) string	Transforms the input number into hexadecimal format	dec_to_hex(7001)"	1b59
deflate(input string) string	Compresses the input using DEFLATE	deflate("Hello")	"\xf2\x48\xcd\xc9\xc9\x07\x04\x00\x00\xff\xff"
ends_with(str string, suffix ...string) bool	Checks if the string ends with any of the provided substrings	ends_with("Hello", "lo")	true
generate_java_gadget(gadget, cmd, encoding interface{}) string	Generates a Java Deserialization Gadget	generate_java_gadget("dns", "{{interactsh-url}}", "base64")	rO0ABXNyABFqYXZhLnV0aWwuSGFzaE1hcAUH2sHDFmDRAwACRgAKbG9hZEZhY3RvckkACXRocmVzaG9sZHhwP0AAAAAAAAx3CAAAABAAAAABc3IADGphdmEubmV0LlVSTJYlNzYa/ORyAwAHSQAIaGFzaENvZGVJAARwb3J0TAAJYXV0aG9yaXR5dAASTGphdmEvbGFuZy9TdHJpbmc7TAAEZmlsZXEAfgADTAAEaG9zdHEAfgADTAAIcHJvdG9jb2xxAH4AA0wAA3JlZnEAfgADeHD//////////3QAAHQAAHEAfgAFdAAFcHh0ACpjYWhnMmZiaW41NjRvMGJ0MHRzMDhycDdlZXBwYjkxNDUub2FzdC5mdW54
generate_jwt(json, algorithm, signature, unixMaxAge) []byte	Generates a JSON Web Token (JWT) using the claims provided in a JSON string, the signature, and the specified algorithm	generate_jwt("{\"name\":\"John Doe\",\"foo\":\"bar\"}", "HS256", "hello-world")	eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJmb28iOiJiYXIiLCJuYW1lIjoiSm9obiBEb2UifQ.EsrL8lIcYJR_Ns-JuhF3VCllCP7xwbpMCCfHin_WT6U
gzip(input string) string	Compresses the input using GZip	base64(gzip("Hello"))	+H4sIAAAAAAAA//JIzcnJBwQAAP//gonR9wUAAAA=
gzip_decode(input string) string	Decompresses the input using GZip	gzip_decode(hex_decode("1f8b08000000000000fff248cdc9c907040000ffff8289d1f705000000"))	Hello
hex_decode(input interface{}) []byte	Hex decodes the given input	hex_decode("6161")	aa
hex_encode(input interface{}) string	Hex encodes the given input	hex_encode("aa")	6161
hex_to_dec(hexNumber number | string) float64	Transforms the input hexadecimal number into decimal format	hex_to_dec("ff") hex_to_dec("0xff")	255
hmac(algorithm, data, secret) string	hmac function that accepts a hashing function type with data and secret	hmac("sha1", "test", "scrt")	8856b111056d946d5c6c92a21b43c233596623c6
html_escape(input interface{}) string	HTML escapes the given input	html_escape("<body>test</body>")	&lt;body&gt;test&lt;/body&gt;
html_unescape(input interface{}) string	HTML un-escapes the given input	html_unescape("&lt;body&gt;test&lt;/body&gt;")	<body>test</body>
index(slice, index) interface{}	Select item at index from slice or string (zero based)	index("test",0)	t
inflate(input string) string	Decompresses the input using DEFLATE	inflate(hex_decode("f348cdc9c90700"))	Hello
join(separator string, elements ...interface{}) string	Joins the given elements using the specified separator	join("_", 123, "hello", "world")	123_hello_world
jarm(hostport string) string	Calculate the jarm hash for the host:port combination	jarm("127.0.0.1:443")	29d29d00029d29d00041d41d000000ad9bf51cc3f5a1e29eecb81d0c7b06eb
json_minify(json) string	Minifies a JSON string by removing unnecessary whitespace	json_minify("{ \"name\": \"John Doe\", \"foo\": \"bar\" }")	{"foo":"bar","name":"John Doe"}
json_prettify(json) string	Prettifies a JSON string by adding indentation	json_prettify("{\"foo\":\"bar\",\"name\":\"John Doe\"}")	{\n \"foo\": \"bar\",\n \"name\": \"John Doe\"\n}
len(arg interface{}) int	Returns the length of the input	len("Hello")	5
line_ends_with(str string, suffix ...string) bool	Checks if any line of the string ends with any of the provided substrings	line_ends_with("Hello\nHi", "lo")	true
line_starts_with(str string, prefix ...string) bool	Checks if any line of the string starts with any of the provided substrings	line_starts_with("Hi\nHello", "He")	true
llm_prompt(str string) string	Query OpenAI LLM (default GPT 3.5) with the provided text prompt and result the result as string (requires api token as environment variable OPENAI_API_KEY)	llm_prompt("produce a generic json")	{'a':'b'}
md5(input interface{}) string	Calculates the MD5 (Message Digest) hash of the input	md5("Hello")	8b1a9953c4611296a827abf8c47804d7
mmh3(input interface{}) string	Calculates the MMH3 (MurmurHash3) hash of an input	mmh3("Hello")	316307400
oct_to_dec(octalNumber number | string) float64	Transforms the input octal number into a decimal format	oct_to_dec("0o1234567") oct_to_dec(1234567)	342391
print_debug(args ...interface{})	Prints the value of a given input or expression. Used for debugging.	print_debug(1+2, "Hello")	3 Hello
rand_base(length uint, optionalCharSet string) string	Generates a random sequence of given length string from an optional charset (defaults to letters and numbers)	rand_base(5, "abc")	caccb
rand_char(optionalCharSet string) string	Generates a random character from an optional character set (defaults to letters and numbers)	rand_char("abc")	a
rand_int(optionalMin, optionalMax uint) int	Generates a random integer between the given optional limits (defaults to 0 - MaxInt32)	rand_int(1, 10)	6
rand_ip(cidr ...string) string	Generates a random IP address	rand_ip("192.168.0.0/24")	192.168.0.171
rand_text_alpha(length uint, optionalBadChars string) string	Generates a random string of letters, of given length, excluding the optional cutset characters	rand_text_alpha(10, "abc")	WKozhjJWlJ
rand_text_alphanumeric(length uint, optionalBadChars string) string	Generates a random alphanumeric string, of given length without the optional cutset characters	rand_text_alphanumeric(10, "ab12")	NthI0IiY8r
rand_text_numeric(length uint, optionalBadNumbers string) string	Generates a random numeric string of given length without the optional set of undesired numbers	rand_text_numeric(10, 123)	0654087985
regex(pattern, input string) bool	Tests the given regular expression against the input string	regex("H([a-z]+)o", "Hello")	true
remove_bad_chars(input, cutset interface{}) string	Removes the desired characters from the input	remove_bad_chars("abcd", "bc")	ad
repeat(str string, count uint) string	Repeats the input string the given amount of times	repeat("../", 5)	../../../../../
replace(str, old, new string) string	Replaces a given substring in the given input	replace("Hello", "He", "Ha")	Hallo
replace_regex(source, regex, replacement string) string	Replaces substrings matching the given regular expression in the input	replace_regex("He123llo", "(\\d+)", "")	Hello
reverse(input string) string	Reverses the given input	reverse("abc")	cba
sha1(input interface{}) string	Calculates the SHA1 (Secure Hash 1) hash of the input	sha1("Hello")	f7ff9e8b7bb2e09b70935a5d785e0cc5d9d0abf0
sha256(input interface{}) string	Calculates the SHA256 (Secure Hash 256) hash of the input	sha256("Hello")	185f8db32271fe25f561a6fc938b2e264306ec304eda518007d1764826381969
starts_with(str string, prefix ...string) bool	Checks if the string starts with any of the provided substrings	starts_with("Hello", "He")	true
to_lower(input string) string	Transforms the input into lowercase characters	to_lower("HELLO")	hello
to_unix_time(input string, layout string) int	Parses a string date time using default or user given layouts, then returns its Unix timestamp	to_unix_time("2022-01-13T16:30:10+00:00") to_unix_time("2022-01-13 16:30:10") to_unix_time("13-01-2022 16:30:10". "02-01-2006 15:04:05")	1642091410
to_upper(input string) string	Transforms the input into uppercase characters	to_upper("hello")	HELLO
trim(input, cutset string) string	Returns a slice of the input with all leading and trailing Unicode code points contained in cutset removed	trim("aaaHelloddd", "ad")	Hello
trim_left(input, cutset string) string	Returns a slice of the input with all leading Unicode code points contained in cutset removed	trim_left("aaaHelloddd", "ad")	Helloddd
trim_prefix(input, prefix string) string	Returns the input without the provided leading prefix string	trim_prefix("aaHelloaa", "aa")	Helloaa
trim_right(input, cutset string) string	Returns a string, with all trailing Unicode code points contained in cutset removed	trim_right("aaaHelloddd", "ad")	aaaHello
trim_space(input string) string	Returns a string, with all leading and trailing white space removed, as defined by Unicode	trim_space(" Hello ")	"Hello"
trim_suffix(input, suffix string) string	Returns input without the provided trailing suffix string	trim_suffix("aaHelloaa", "aa")	aaHello
unix_time(optionalSeconds uint) float64	Returns the current Unix time (number of seconds elapsed since January 1, 1970 UTC) with the added optional seconds	unix_time(10)	1639568278
unpack(format string, sequence string/bytes) {}interface	Returns the result of python binary unpack for the first operand in the sequence (endianess+operand)	unpack('>I', '\xac\xd7\t\xd0')	-272646673
url_decode(input string) string	URL decodes the input string	url_decode("https:%2F%2Fprojectdiscovery.io%3Ftest=1")	https://projectdiscovery.io?test=1
url_encode(input string) string	URL encodes the input string	url_encode("https://projectdiscovery.io/test?a=1")	https%3A%2F%2Fprojectdiscovery.io%2Ftest%3Fa%3D1
wait_for(seconds uint)	Pauses the execution for the given amount of seconds	wait_for(10)	true
xor(sequences ...strings/bytes)	Perform xor on sequences of same length	xor('abc','def')	50705 in hex
zlib(input string) string	Compresses the input using Zlib	base64(zlib("Hello"))	eJzySM3JyQcEAAD//wWMAfU=
zlib_decode(input string) string	Decompresses the input using Zlib	zlib_decode(hex_decode("789cf248cdc9c907040000ffff058c01f5"))	Hello
padding(input string, padding string,length int) string	Adds padding char to input string until it reaches desired length	padding("A","b",3)	Abb

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.