Re: Java integer overflows (was: a really long topic)

[Eoin <eoinkeary () gmail com>]

Hello,
Even though java throws an exception if a catch is not present the
thread is killed.
The code that threw the exception is never resumed.

Also using a finally block can ensure things stop gracefully.
Developers (I used to be one) also catch exceptions and bury them by
not doing anything with them.

-ek


On 29/03/06, Andrew van der Stock <vanderaj () greebo net> wrote:
> 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 () gmail 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 () greebo 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


--
Eoin Keary cissp

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