Verskeie JS Tricks & Relevante Inligting

Reading time: 12 minutes

Javascript Fuzzing

Geldige JS Kommentaar Karakters

//This is a 1 line comment
/* This is a multiline comment*/
#!This is a 1 line comment, but "#!" must to be at the beggining of the line
-->This is a 1 line comment, but "-->" must to be at the beggining of the line


for (let j = 0; j < 128; j++) {
for (let k = 0; k < 128; k++) {
for (let l = 0; l < 128; l++) {
if (j == 34 || k ==34 || l ==34)
continue;
if (j == 0x0a || k ==0x0a || l ==0x0a)
continue;
if (j == 0x0d || k ==0x0d || l ==0x0d)
continue;
if (j == 0x3c || k ==0x3c || l ==0x3c)
continue;
if (
(j == 47 && k == 47)
||(k == 47 && l == 47)
)
continue;
try {
var cmd = String.fromCharCode(j) + String.fromCharCode(k) + String.fromCharCode(l) + 'a.orange.ctf"';
eval(cmd);
} catch(e) {
var err = e.toString().split('\n')[0].split(':')[0];
if (err === 'SyntaxError' || err === "ReferenceError")
continue
err = e.toString().split('\n')[0]
}
console.log(err,cmd);
}
}
}
//From: https://balsn.tw/ctf_writeup/20191012-hitconctfquals/#bounty-pl33z

// From: Heyes, Gareth. JavaScript for hackers: Learn to think like a hacker (p. 43). Kindle Edition.
log=[];
for(let i=0;i<=0xff;i++){
for(let j=0;j<=0xfff;j++){
try {
eval(`${String.fromCodePoint(i,j)}%$£234$`)
log.push([i,j])
}catch(e){}
}
}
console.log(log)//[35,33],[47,47]

Geldige JS Nuwe Lyn Karakters

//Javascript interpret as new line these chars:
String.fromCharCode(10) //0x0a
String.fromCharCode(13) //0x0d
String.fromCharCode(8232) //0xe2 0x80 0xa8
String.fromCharCode(8233) //0xe2 0x80 0xa8

for (let j = 0; j < 65536; j++) {
try {
var cmd = '"aaaaa";' + String.fromCharCode(j) + '-->a.orange.ctf"'
eval(cmd)
} catch (e) {
var err = e.toString().split("\n")[0].split(":")[0]
if (err === "SyntaxError" || err === "ReferenceError") continue
err = e.toString().split("\n")[0]
}
console.log(`[${err}]`, j, cmd)
}
//From: https://balsn.tw/ctf_writeup/20191012-hitconctfquals/#bounty-pl33z

Geldige JS Spasies in funksie-aanroep

// Heyes, Gareth. JavaScript for hackers: Learn to think like a hacker (pp. 40-41). Kindle Edition.

// Check chars that can be put in between in func name and the ()
function x(){}

log=[];
for(let i=0;i<=0x10ffff;i++){
try {
eval(`x${String.fromCodePoint(i)}()`)
log.push(i)
}catch(e){}
}

console.log(log)v//9,10,11,12,13,32,160,5760,8192,8193,8194,8195,8196,8197,8198,8199,8200,8201,8202,813 232,8233,8239,8287,12288,65279

Geldige karakters om Strings te genereer

// Heyes, Gareth. JavaScript for hackers: Learn to think like a hacker (pp. 41-42). Kindle Edition.

// Check which pairs of chars can make something be a valid string
log = []
for (let i = 0; i <= 0x10ffff; i++) {
try {
eval(`${String.fromCodePoint(i)}%$£234${String.fromCodePoint(i)}`)
log.push(i)
} catch (e) {}
}
console.log(log) //34,39,47,96
//single quote, quotes, backticks & // (regex)

Surrogaat Parels BF

Hierdie tegniek sal nie baie nuttig wees vir XSS nie, maar dit kan nuttig wees om WAF-beskermings te omseil. Hierdie python kode ontvang 2 bytes as invoer en soek 'n surrogaat paar wat die eerste byte as die laaste byte van die hoë surrogaat paar en die laaste byte as die laaste byte van die lae surrogaat paar het.

def unicode(findHex):
for i in range(0,0xFFFFF):
H = hex(int(((i - 0x10000) / 0x400) + 0xD800))
h = chr(int(H[-2:],16))
L = hex(int(((i - 0x10000) % 0x400 + 0xDC00)))
l = chr(int(L[-2:],16))
if(h == findHex[0]) and (l == findHex[1]):
print(H.replace("0x","\\u")+L.replace("0x","\\u"))

javascript{}: Protokol Fuzzing

// Heyes, Gareth. JavaScript for hackers: Learn to think like a hacker (p. 34). Kindle Edition.
log=[];
let anchor = document.createElement('a');
for(let i=0;i<=0x10ffff;i++){
anchor.href = `javascript${String.fromCodePoint(i)}:`;
if(anchor.protocol === 'javascript:') {
log.push(i);
}
}
console.log(log)//9,10,13,58
// Note that you could BF also other possitions of the use of multiple chars

// Test one option
let anchor = document.createElement('a');
anchor.href = `javascript${String.fromCodePoint(58)}:alert(1337)`;
anchor.append('Click me')
document.body.append(anchor)

// Another way to test
<a href="&#12;javascript:alert(1337)">Test</a>

URL Fuzzing

// Heyes, Gareth. JavaScript for hackers: Learn to think like a hacker (pp. 36-37). Kindle Edition.

// Before the protocol
a = document.createElement("a")
log = []
for (let i = 0; i <= 0x10ffff; i++) {
a.href = `${String.fromCodePoint(i)}https://hacktricks.xyz`
if (a.hostname === "hacktricks.xyz") {
log.push(i)
}
}
console.log(log) //0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32

// Between the slashes
a = document.createElement("a")
log = []
for (let i = 0; i <= 0x10ffff; i++) {
a.href = `/${String.fromCodePoint(i)}/hacktricks.xyz`
if (a.hostname === "hacktricks.xyz") {
log.push(i)
}
}
console.log(log) //9,10,13,47,92

HTML Fuzzing

// Heyes, Gareth. JavaScript for hackers: Learn to think like a hacker (p. 38). Kindle Edition.

// Fuzzing chars that can close an HTML comment

let log = []
let div = document.createElement("div")
for (let i = 0; i <= 0x10ffff; i++) {
div.innerHTML = `<!----${String.fromCodePoint(i)}><span></span>-->`
if (div.querySelector("span")) {
log.push(i)
}
}
console.log(log) //33,45,62

Analiseer attribuutte

Die hulpmiddel Hackability inspector van Portswigger help om die attribuutte van 'n javascript objek te analiseer. Kyk: https://portswigger-labs.net/hackability/inspector/?input=x.contentWindow&html=%3Ciframe%20src=//subdomain1.portswigger-labs.net%20id=x%3E

.map js lêers

• Trick om .map js lêers af te laai: https://medium.com/@bitthebyte/javascript-for-bug-bounty-hunters-part-2-f82164917e7
• Jy kan hierdie hulpmiddel gebruik om hierdie lêers te analiseer https://github.com/paazmaya/shuji

"--" Toewysing

Die afname operateur -- is ook 'n toewysing. Hierdie operateur neem 'n waarde en verminder dit dan met een. As daardie waarde nie 'n nommer is nie, sal dit op NaN gestel word. Dit kan gebruik word om die inhoud van veranderlikes uit die omgewing te verwyder.

Funksies Tricks

.call en .apply

Die .call metode van 'n funksie word gebruik om die funksie te hardloop.
Die eerste argument wat dit standaard verwag, is die waarde van this en as niks verskaf word nie, sal window daardie waarde wees (tenzij strikte modus gebruik word).

function test_call() {
console.log(this.value) //baz
}
new_this = { value: "hey!" }
test_call.call(new_this)

// To pass more arguments, just pass then inside .call()
function test_call() {
console.log(arguments[0]) //"arg1"
console.log(arguments[1]) //"arg2"
console.log(this) //[object Window]
}
test_call.call(null, "arg1", "arg2")

// If you use the "use strict" directive "this" will be null instead of window:
function test_call() {
"use strict"
console.log(this) //null
}
test_call.call(null)

//The apply function is pretty much exactly the same as the call function with one important difference, you can supply an array of arguments in the second argument:
function test_apply() {
console.log(arguments[0]) //"arg1"
console.log(arguments[1]) //"arg2"
console.log(this) //[object Window]
}
test_apply.apply(null, ["arg1", "arg2"])

Pylpunte funksies

Pylpunte funksies laat jou toe om funksies in 'n enkele lyn makliker te genereer (as jy hulle verstaan)

// Traditional
function (a){ return a + 1; }
// Arrow forms
a => a + 100;
a => {a + 100};

// Traditional
function (a, b){ return a + b + 1; }
// Arrow
(a, b) => a + b + 100;

// Tradictional no args
let a = 4;
let b = 2;
function (){ return a + b + 1; }

// Arrow
let a = 4;
let b = 2;
() => a + b + 1;

So, die meeste van die vorige funksies is eintlik nutteloos omdat ons hulle nêrens stoor om te stoor en aan te roep nie. Voorbeeld om die plusone funksie te skep:

// Traductional
function plusone(a) {
return a + 1
}

//Arrow
plusone = (a) => a + 100

Bind-funksie

Die bind-funksie laat jou toe om 'n kopie van 'n funksie te skep wat die this objek en die parameters wat gegee is, wysig.

//This will use the this object and print "Hello World"
var fn = function (param1, param2) {
console.info(this, param1, param2)
}
fn("Hello", "World")

//This will still use the this object and print "Hello World"
var copyFn = fn.bind()
copyFn("Hello", "World")

//This will use the "console" object as "this" object inside the function and print "fixingparam1 Hello"
var bindFn_change = fn.bind(console, "fixingparam1")
bindFn_change("Hello", "World")

//This will still use the this object and print "fixingparam1 Hello"
var bindFn_thisnull = fn.bind(null, "fixingparam1")
bindFn_change("Hello", "World")

//This will still use the this object and print "fixingparam1 Hello"
var bindFn_this = fn.bind(this, "fixingparam1")
bindFn_change("Hello", "World")

Funksie kode lek

As jy die objek van 'n funksie kan toegang kry, kan jy die kode van daardie funksie kry.

function afunc() {
return 1 + 1
}
console.log(afunc.toString()) //This will print the code of the function
console.log(String(afunc)) //This will print the code of the function
console.log(this.afunc.toString()) //This will print the code of the function
console.log(global.afunc.toString()) //This will print the code of the function

In gevalle waar die funksie geen naam het nie, kan jy steeds die funksie kode van binne af druk:

;(function () {
return arguments.callee.toString()
})()(function () {
return arguments[0]
})("arg0")

Sommige ewekansige maniere om die kode van 'n funksie (selfs kommentaar) uit 'n ander funksie te onttrek:

;(function () {
return (retFunc) => String(arguments[0])
})((a) => {
/* Hidden commment */
})()(function () {
return (retFunc) => Array(arguments[0].toString())
})((a) => {
/* Hidden commment */
})()(function () {
return String(this)
}).bind(() => {
/* Hidden commment */
})()((u) => String(u))((_) => {
/* Hidden commment */
})((u) => (_) => String(u))((_) => {
/* Hidden commment */
})()

Sandbox Escape - Herwinning van die window objek

Die Window objek maak dit moontlik om globaal gedefinieerde funksies soos alert of eval te bereik.

// Some ways to access window
window.eval("alert(1)")
frames
globalThis
parent
self
top //If inside a frame, this is top most window

// Access window from document
document.defaultView.alert(1)
// Access document from a node object
node = document.createElement('div')
node.ownerDocument.defaultView.alert(1)

// There is a path property on each error event whose last element is the window
<img src onerror=event.path.pop().alert(1337)>
// In other browsers the method is
<img src onerror=event.composedPath().pop().alert(1337)>
// In case of svg, the "event" object is called "evt"
<svg><image href=1 onerror=evt.composedPath().pop().alert(1337)>

// Abusing Error.prepareStackTrace to get Window back
Error.prepareStackTrace=function(error, callSites){
2   callSites.shift().getThis().alert(1337);
3 };
4 new Error().stack

// From an HTML event
// Events from HTML are executed in this context
with(document) {
with(element) {
//executed event
}
}
// Because of that with(document) it's possible to access properties of document like:
<img src onerror=defaultView.alert(1337)>
<img src onerror=s=createElement('script');s.append('alert(1337)');appendChild(s)>

Breekpunt op toegang tot waarde

// Stop when a property in sessionStorage or localStorage is set/get
// via getItem or setItem functions
sessionStorage.getItem = localStorage.getItem = function (prop) {
debugger
return sessionStorage[prop]
}

localStorage.setItem = function (prop, val) {
debugger
localStorage[prop] = val
}

// Stop when anyone sets or gets the property "ppmap" in any object
// For example sessionStorage.ppmap
// "123".ppmap
// Useful to find where weird properties are being set or accessed
// or to find where prototype pollutions are occurring

function debugAccess(obj, prop, debugGet = true) {
var origValue = obj[prop]

Object.defineProperty(obj, prop, {
get: function () {
if (debugGet) debugger
return origValue
},
set: function (val) {
debugger
origValue = val
},
})
}

debugAccess(Object.prototype, "ppmap")

Outomatiese Blaaier Toegang om payloads te toets

//Taken from https://github.com/svennergr/writeups/blob/master/inti/0621/README.md
const puppeteer = require("puppeteer")

const realPasswordLength = 3000
async function sleep(ms) {
return new Promise((resolve) => setTimeout(resolve, ms))
}

;(async () => {
const browser = await puppeteer.launch()
const page = await browser.newPage()
//Loop to iterate through different values
for (let i = 0; i < 10000; i += 100) {
console.log(`Run number ${i}`)
const input = `${"0".repeat(i)}${realPasswordLength}`
console.log(
`  https://challenge-0621.intigriti.io/passgen.php?passwordLength=${input}&allowNumbers=true&allowSymbols=true&timestamp=1624556811000`
)
//Go to the page
await page.goto(
`https://challenge-0621.intigriti.io/passgen.php?passwordLength=${input}&allowNumbers=true&allowSymbols=true&timestamp=1624556811000`
)
//Call function "generate()" inside the page
await page.evaluate("generate()")
//Get node inner text from an HTML element
const passwordContent = await page.$$eval(
".alert .page-content",
(node) => node[0].innerText
)
//Transform the content and print it in console
const plainPassword = passwordContent.replace("Your password is: ", "")
if (plainPassword.length != realPasswordLength) {
console.log(i, plainPassword.length, plainPassword)
}

await sleep(1000)
}
await browser.close()
})()