Buffer Access Using Size of Source Buffer

Opis

The product uses the size of a source buffer when reading from or writing to a destination buffer, which may cause it to access memory that is outside of the bounds of the buffer.

When the size of the destination is smaller than the size of the source, a buffer overflow could occur.

Skutki

• Availability

  Modify Memory; DoS: Crash, Exit, or Restart; DoS: Resource Consumption (CPU)

  Buffer overflows generally lead to crashes. Other attacks leading to lack of availability are possible, including putting the program into an infinite loop.

• Integrity, Confidentiality, Availability

  Read Memory; Modify Memory; Execute Unauthorized Code or Commands

  Buffer overflows often can be used to execute arbitrary code, which is usually outside the scope of a program's implicit security policy.

• Access Control

  Bypass Protection Mechanism

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

Zapobieganie

• Architecture and Design

  Use an abstraction library to abstract away risky APIs. Examples include the Safe C String Library (SafeStr) by Viega, and the Strsafe.h library from Microsoft. This is not a complete solution, since many buffer overflows are not related to strings.

• Operation, Build and Compilation · Environment Hardening

  Use automatic buffer overflow detection mechanisms that are offered by certain compilers or compiler extensions. Examples include: the Microsoft Visual Studio /GS flag, Fedora/Red Hat FORTIFY_SOURCE GCC flag, StackGuard, and ProPolice, which provide various mechanisms including canary-based detection and range/index checking.

  D3-SFCV (Stack Frame Canary Validation) from D3FEND [REF-1334] discusses canary-based detection in detail.

  Skuteczność: Defense in Depth

• Implementation

  Programmers should adhere to the following rules when allocating and managing their applications memory: Double check that your buffer is as large as you specify. When using functions that accept a number of bytes to copy, such as strncpy(), be aware that if the destination buffer size is equal to the source buffer size, it may not NULL-terminate the string. Check buffer boundaries if calling this function in a loop and make sure there is no danger of writing past the allocated space. Truncate all input strings to a reasonable length before passing them to the copy and concatenation functions.

• Operation, Build and Compilation · Environment Hardening

  Run or compile the software using features or extensions that randomly arrange the positions of a program's executable and libraries in memory. Because this makes the addresses unpredictable, it can prevent an attacker from reliably jumping to exploitable code.

  Examples include Address Space Layout Randomization (ASLR) [REF-58] [REF-60] and Position-Independent Executables (PIE) [REF-64]. Imported modules may be similarly realigned if their default memory addresses conflict with other modules, in a process known as "rebasing" (for Windows) and "prelinking" (for Linux) [REF-1332] using randomly generated addresses. ASLR for libraries cannot be used in conjunction with prelink since it would require relocating the libraries at run-time, defeating the whole purpose of prelinking.

  For more information on these techniques see D3-SAOR (Segment Address Offset Randomization) from D3FEND [REF-1335].

  Skuteczność: Defense in Depth

• Operation · Environment Hardening

  Use a CPU and operating system that offers Data Execution Protection (using hardware NX or XD bits) or the equivalent techniques that simulate this feature in software, such as PaX [REF-60] [REF-61]. These techniques ensure that any instruction executed is exclusively at a memory address that is part of the code segment.

  For more information on these techniques see D3-PSEP (Process Segment Execution Prevention) from D3FEND [REF-1336].

  Skuteczność: Defense in Depth

• Build and Compilation, Operation

  Most mitigating technologies at the compiler or OS level to date address only a subset of buffer overflow problems and rarely provide complete protection against even that subset. It is good practice to implement strategies to increase the workload of an attacker, such as leaving the attacker to guess an unknown value that changes every program execution.

Słabość nadrzędna

• CWE-805 Buffer Access with Incorrect Length Value

Kiedy powstaje

• Implementation

Dotyczy

Memory-Unsafe, C, C++

Źródła

1. Using the Strsafe.h Functions — Microsoft
2. Safe C String Library v1.0.3 — Matt Messier, John Viega
3. Address Space Layout Randomization in Windows Vista — Michael Howard
4. Limiting buffer overflows with ExecShield — Arjan van de Ven
5. PaX
6. Understanding DEP as a mitigation technology part 1 — Microsoft
7. Position Independent Executables (PIE) — Grant Murphy, Red Hat, 2012
8. Prelink and address space randomization — John Richard Moser, 2006
9. Jump Over ASLR: Attacking Branch Predictors to Bypass ASLR — Dmitry Evtyushkin, Dmitry Ponomarev, Nael Abu-Ghazaleh, 2016
10. Stack Frame Canary Validation (D3-SFCV) — D3FEND, 2023
11. Segment Address Offset Randomization (D3-SAOR) — D3FEND, 2023
12. Process Segment Execution Prevention (D3-PSEP) — D3FEND, 2023
13. Bypassing Browser Memory Protections: Setting back browser security by 10 years — Alexander Sotirov and Mark Dowd, Memory information leaks, 2008
14. AddressSanitizer