WebApp Sec mailing list archives

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


From: michaelslists () gmail com
Date: Wed, 29 Mar 2006 14:50:10 +1100

right,

but we're talking about unmanaged vs managed, and the earlier poster
(i think it might've been "pavel" [sorry if it wasn't]), said that
100% java is still vulnerable to buffer overflows. the fact is that it
isn't.

-- Michael

On 3/29/06, 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

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