Trash:Talk:Internet Browser: Difference between revisions

Line 9:

I don't think this is exploitable in any way. To me, seems more like NULL pointer dereferencing. Here's my full theory, may be wrong tho:

* the Javascript engine doesn't allocate memory for strings that are too long, but still keeps track of their length. (try generating a 2^31 characters long string, alert()'ing it shows an empty alert, however its length returns the expected value)

* such strings point to NULL instead of pointing to a memory buffer with characters. Their size is checked before trying to read them.

* such strings point to NULL instead of pointing to a memory buffer with characters. Their size is checked before trying to read them to display them in an alert.

* now, if you generate a 2^32 string, the length of the string is 0x100000000 characters. This value gets cut off to zero because it doesn't fit in a 32bit integer. Therefore the length property of the string is zero.

* when trying to alert() this string, the security check described above does infact "0 < maxlength", so the string is considered short enough to be displayed. However, since it was made from strings being already too large, its pointer is NULL.

@@ Line 9: / Line 9: @@
 I don't think this is exploitable in any way. To me, seems more like NULL pointer dereferencing. Here's my full theory, may be wrong tho:
 * the Javascript engine doesn't allocate memory for strings that are too long, but still keeps track of their length. (try generating a 2^31 characters long string, alert()'ing it shows an empty alert, however its length returns the expected value)
-* such strings point to NULL instead of pointing to a memory buffer with characters. Their size is checked before trying to read them.
+* such strings point to NULL instead of pointing to a memory buffer with characters. Their size is checked before trying to read them to display them in an alert.
 * now, if you generate a 2^32 string, the length of the string is 0x100000000 characters. This value gets cut off to zero because it doesn't fit in a 32bit integer. Therefore the length property of the string is zero.
 * when trying to alert() this string, the security check described above does infact "0 < maxlength", so the string is considered short enough to be displayed. However, since it was made from strings being already too large, its pointer is NULL.