/prog/ - ssl vulnerability

Name: Anonymous 2014-04-13 22:36

>>43
There is no inserting a run time check in C. But a warning is issued if an index is used that cannot be bounded.


  int a[5];
  int i; // i is currently undefined
  scanf("%u", &i); // i can now be any value.
  a[i] = 3; // i's type does not contain a predicate implying 0 <= i < 5, so this will signal an error.

   int a[5];
   int i; // i is undefined
   scanf("%d", &i); // i is some value
   if(0 <= i && i < 5)
   {
       // within this block, i satisfies the predicate, 0 <= i && i < 5
      a[i] = 3; // length of a is 5, so i is safe.
   }

    printf("%d\n", a[i]); // i is not safe in this scope.

>>3