full-disclosure - Java integer overflows (was: a really long topic)

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Date: Wed Mar 29 08:19:10 2006
From: vanderaj at greebo.net (Andrew van der Stock)
Subject: Java integer overflows (was: a really long topic)

I'm not talking arbitrary code execution, I'm talking about odd code  
paths, bizarre outcomes, and DoS.

For example (found via 19 Sins, Viega, Howard and LeBlanc):
http://seclists.org/lists/bugtraq/2004/Nov/0097.html

I know Michael reads webappsec, he may have more examples.

In my own code testing, I look for silly behaviors if a user can  
insert a large or negative number. You'd be surprised how often it  
occurs. There is no excuse not to include basic range checks when  
performing data validation.

thanks,
Andrew

On 29/03/2006, at 2:30 PM, michaelslists@...il.com wrote:

> No you dont.
>
> Arrays are all bounds checked; ..., that is, the following code will
> throw an exception:
>
> ================================
> class Foo {
>   static {
>     int[] m = new int[2];
>     System.out.println(m[34]);
>   }
> }
> ================================
>
>
> What do you mean by "overflow"? Do you mean this?
>
> ================================
> class Foo {
>   static {
>     int m = Integer.MAX_VALUE;
>     int k = Integer.MAX_VALUE + Integer.MAX_VALUE;
>     System.out.println(m);
>     System.out.println(k);
>     System.exit(0);
>   }
> }
> ================================
>
> if so, I don't see how that is an issue.
>
> -- Michael
>
>
>
> On 3/29/06, Andrew van der Stock <vanderaj@...ebo.net> wrote:
>> This is not quite true.
>>
>> Java does not prevent integer overflows (it will not throw an
>> exception). So you still have to be careful about array indexes.
>>
>> Andrew

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