1663
Potential Mitigations
Phase: Requirements
Strategy = Language Selection
Use a language that does not allow this weakness to occur or provides constructs that make
this weakness easier to avoid. For example, many languages that perform their own memory
management, such as Java and Perl, are not subject to buffer overflows. Other languages, such
as Ada and C#, typically provide overflow protection, but the protection can be disabled by the
programmer. Be wary that a language's interface to native code may still be subject to overflows,
even if the language itself is theoretically safe.
Phase: Architecture and Design
Strategy = Libraries or Frameworks
Use a vetted library or framework that does not allow this weakness to occur or provides
constructs that make this weakness easier to avoid. Examples include the Safe C String Library
(SafeStr) by Messier and Viega [REF-57], and the Strsafe.h library from Microsoft [REF-56].
These libraries provide safer versions of overflow-prone string-handling functions.
Phase: Operation
Phase: Build and Compilation
Strategy = 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.
Effectiveness = Defense in Depth
This is not necessarily a complete solution, since these mechanisms only detect certain types of
overflows. In addition, the result is still a denial of service, since the typical response is to exit the
application.
Phase: Implementation
Consider adhering to the following rules when allocating and managing an application's memory:
Double check that the buffer is as large as specified. 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 accessing
the buffer in a loop and make sure there is no danger of writing past the allocated space. If
necessary, truncate all input strings to a reasonable length before passing them to the copy and
concatenation functions.
Phase: Operation
Phase: Build and Compilation
Strategy = 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].
CWE Version 4.14
CWE-787: Out-of-bounds Write
CWE-787: Out-of-bounds Write