Use of Pointer Subtraction to Determine Size

Opis

The product subtracts one pointer from another in order to determine size, but this calculation can be incorrect if the pointers do not exist in the same memory chunk.

Skutki

• Access Control, Integrity, Confidentiality, Availability

  Modify Memory; Read Memory; Execute Unauthorized Code or Commands; Gain Privileges or Assume Identity

  There is the potential for arbitrary code execution with privileges of the vulnerable program.

Zapobieganie

• Implementation

  Save an index variable. This is the recommended solution. Rather than subtract pointers from one another, use an index variable of the same size as the pointers in question. Use this variable to "walk" from one pointer to the other and calculate the difference. Always validate this number.

Słabość nadrzędna

• CWE-682 Incorrect Calculation

Kiedy powstaje

• Implementation

Dotyczy

C, C++

Źródła

1. The CLASP Application Security Process — Secure Software, Inc., 2005