Write-what-where Condition

Opis

Any condition where the attacker has the ability to write an arbitrary value to an arbitrary location, often as the result of a buffer overflow.

Skutki

• Integrity, Confidentiality, Availability, Access Control

  Modify Memory; Execute Unauthorized Code or Commands; Gain Privileges or Assume Identity; DoS: Crash, Exit, or Restart; Bypass Protection Mechanism

  Clearly, write-what-where conditions can be used to write data to areas of memory outside the scope of a policy. Also, they almost invariably can be used to execute arbitrary code, which is usually outside the scope of a program's implicit security policy. If the attacker can overwrite a pointer's worth of memory (usually 32 or 64 bits), they can redirect a function pointer to their own malicious code. Even when the attacker can only modify a single byte arbitrary code execution can be possible. Sometimes this is because the same problem can be exploited repeatedly to the same effect. Other times it is because the attacker can overwrite security-critical application-specific data -- such as a flag indicating whether the user is an administrator.

• Integrity, Availability

  DoS: Crash, Exit, or Restart; Modify Memory

  Many memory accesses can lead to program termination, such as when writing to addresses that are invalid for the current process.

• Access Control, Other

  Bypass Protection Mechanism; Other

  When the consequence is arbitrary code execution, this can often be used to subvert any other security service.

Zapobieganie

• Architecture and Design · Language Selection

  Use a language that provides appropriate memory abstractions.

• Operation

  Use OS-level preventative functionality integrated after the fact. Not a complete solution.

Przykłady podatności

• CVE-2019-19911 Chain: Python library does not limit the resources used to process images that specify a very large number of bands (CWE-1284), leading to excessive memory consumption (CWE-789) or an integer overflow (CWE-190).
• CVE-2022-0545 Chain: 3D renderer has an integer overflow (CWE-190) leading to write-what-where condition (CWE-123) using a crafted image.

Słabość nadrzędna

• CWE-787 Out-of-bounds Write
• CWE-119 Improper Restriction of Operations within the Bounds of a Memory Buffer

Kiedy powstaje

• Implementation

Dotyczy

Memory-Unsafe, C, C++

Źródła

1. 24 Deadly Sins of Software Security — Michael Howard, David LeBlanc, John Viega, "Sin 5: Buffer Overruns." Page 89, McGraw-Hill, 2010
2. The CLASP Application Security Process — Secure Software, Inc., 2005
3. AddressSanitizer