CWE-122 堆缓冲区溢出

Heap-based Buffer Overflow

结构: Simple

Abstraction: Variant

状态: Draft

被利用可能性: High

基本描述

A heap overflow condition is a buffer overflow, where the buffer that can be overwritten is allocated in the heap portion of memory, generally meaning that the buffer was allocated using a routine such as malloc().

相关缺陷

  • cwe_Nature: ChildOf cwe_CWE_ID: 788 cwe_View_ID: 1000 cwe_Ordinal: Primary

  • cwe_Nature: ChildOf cwe_CWE_ID: 788 cwe_View_ID: 699 cwe_Ordinal: Primary

  • cwe_Nature: ChildOf cwe_CWE_ID: 787 cwe_View_ID: 1000

  • cwe_Nature: ChildOf cwe_CWE_ID: 787 cwe_View_ID: 699

适用平台

Language: [{'cwe_Name': 'C', 'cwe_Prevalence': 'Undetermined'}, {'cwe_Name': 'C++', 'cwe_Prevalence': 'Undetermined'}]

常见的影响

范围 影响 注释
Availability ['DoS: Crash, Exit, or Restart', 'DoS: Resource Consumption (CPU)', 'DoS: Resource Consumption (Memory)'] 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', 'Access Control'] ['Execute Unauthorized Code or Commands', 'Bypass Protection Mechanism', 'Modify Memory'] Buffer overflows often can be used to execute arbitrary code, which is usually outside the scope of a program's implicit security policy. Besides important user data, heap-based overflows can be used to overwrite function pointers that may be living in memory, pointing it to the attacker's code. Even in applications that do not explicitly use function pointers, the run-time will usually leave many in memory. For example, object methods in C++ are generally implemented using function pointers. Even in C programs, there is often a global offset table used by the underlying runtime.
['Integrity', 'Confidentiality', 'Availability', 'Access Control', 'Other'] ['Execute Unauthorized Code or Commands', 'Bypass Protection Mechanism', 'Other'] When the consequence is arbitrary code execution, this can often be used to subvert any other security service.

可能的缓解方案

策略:

Pre-design: Use a language or compiler that performs automatic bounds checking.

Architecture and Design

策略:

Use an abstraction library to abstract away risky APIs. Not a complete solution.

Build and Compilation

策略:

Pre-design through Build: Canary style bounds checking, library changes which ensure the validity of chunk data, and other such fixes are possible, but should not be relied upon.

Implementation

策略:

Implement and perform bounds checking on input.

Implementation

策略: Libraries or Frameworks

Do not use dangerous functions such as gets. Look for their safe equivalent, which checks for the boundary.

Operation

策略:

Use OS-level preventative functionality. This is not a complete solution, but it provides some defense in depth.

示例代码

例

While buffer overflow examples can be rather complex, it is possible to have very simple, yet still exploitable, heap-based buffer overflows:

bad C

#define BUFSIZE 256
int main(int argc, char argv) {
char buf;
buf = (char )malloc(sizeof(char)*BUFSIZE);
strcpy(buf, argv[1]);
}

The buffer is allocated heap memory with a fixed size, but there is no guarantee the string in argv[1] will not exceed this size and cause an overflow.

例

This example applies an encoding procedure to an input string and stores it into a buffer.

bad C

char * copy_input(char user_supplied_string){
int i, dst_index;
char dst_buf = (char)malloc(4sizeof(char) * MAX_SIZE);
if ( MAX_SIZE <= strlen(user_supplied_string) ){
die("user string too long, die evil hacker!");
}
dst_index = 0;
for ( i = 0; i < strlen(user_supplied_string); i++ ){
if( '&' == user_supplied_string[i] ){
dst_buf[dst_index++] = '&';
dst_buf[dst_index++] = 'a';
dst_buf[dst_index++] = 'm';
dst_buf[dst_index++] = 'p';
dst_buf[dst_index++] = ';';
}
else if ('<' == user_supplied_string[i] ){

/ encode to &lt; /
}
else dst_buf[dst_index++] = user_supplied_string[i];
}
return dst_buf;
}

The programmer attempts to encode the ampersand character in the user-controlled string, however the length of the string is validated before the encoding procedure is applied. Furthermore, the programmer assumes encoding expansion will only expand a given character by a factor of 4, while the encoding of the ampersand expands by 5. As a result, when the encoding procedure expands the string it is possible to overflow the destination buffer if the attacker provides a string of many ampersands.

分析过的案例

标识 说明 链接
CVE-2007-4268 Chain: integer signedness error (CWE-195) passes signed comparison, leading to heap overflow (CWE-122) https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2007-4268
CVE-2009-2523 Chain: product does not handle when an input string is not NULL terminated (CWE-170), leading to buffer over-read (CWE-125) or heap-based buffer overflow (CWE-122). https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2009-2523

Notes

分类映射

映射的分类名 ImNode ID Fit Mapped Node Name
CLASP Heap overflow
Software Fault Patterns SFP8 Faulty Buffer Access
CERT C Secure Coding STR31-C CWE More Specific Guarantee that storage for strings has sufficient space for character data and the null terminator

相关攻击模式

  • CAPEC-92

引用