Compiler Removal of Code to Clear Buffers

Opis

Sensitive memory is cleared according to the source code, but compiler optimizations leave the memory untouched when it is not read from again, aka "dead store removal."

This compiler optimization error occurs when:

1. Secret data are stored in memory.

1. The secret data are scrubbed from memory by overwriting its contents.

1. The source code is compiled using an optimizing compiler, which identifies and removes the function that overwrites the contents as a dead store because the memory is not used subsequently.

Skutki

• Confidentiality, Access Control

  Read Memory; Bypass Protection Mechanism

  This weakness will allow data that has not been cleared from memory to be read. If this data contains sensitive password information, then an attacker can read the password and use the information to bypass protection mechanisms.

Zapobieganie

• Implementation

  Store the sensitive data in a "volatile" memory location if available.

• Build and Compilation

  If possible, configure your compiler so that it does not remove dead stores.

• Architecture and Design

  Where possible, encrypt sensitive data that are used by a software system.

Słabość nadrzędna

• CWE-733 Compiler Optimization Removal or Modification of Security-critical Code

Kiedy powstaje

• Implementation
• Build and Compilation

Dotyczy

C, C++, Compiled

Źródła

1. Seven Pernicious Kingdoms: A Taxonomy of Software Security Errors — Katrina Tsipenyuk, Brian Chess, Gary McGraw, NIST, 2005
2. Writing Secure Code — Michael Howard, David LeBlanc, Chapter 9, "A Compiler Optimization Caveat" Page 322, Microsoft Press, 2002
3. When scrubbing secrets in memory doesn't work — Michael Howard, BugTraq, 2002
4. Some Bad News and Some Good News — Michael Howard, Microsoft, 2002
5. GNU GCC: Optimizer Removes Code Necessary for Security — Joseph Wagner, Bugtraq, 2002