CWE-135 多字节字符串长度的计算不正确
Incorrect Calculation of Multi-Byte String Length
结构: Simple
Abstraction: Base
状态: Draft
被利用可能性: unkown
基本描述
The software does not correctly calculate the length of strings that can contain wide or multi-byte characters.
相关缺陷
- cwe_Nature: ChildOf cwe_CWE_ID: 682 cwe_View_ID: 1000 cwe_Ordinal: Primary
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 |
|---|---|---|
| ['Integrity', 'Confidentiality', 'Availability'] | Execute Unauthorized Code or Commands | This weakness may lead to a buffer overflow. Buffer overflows often can be used to execute arbitrary code, which is usually outside the scope of a program's implicit security policy. This can often be used to subvert any other security service. |
| ['Availability', 'Confidentiality'] | ['Read Memory', 'DoS: Crash, Exit, or Restart', 'DoS: Resource Consumption (CPU)', 'DoS: Resource Consumption (Memory)'] | Out of bounds memory access will very likely result in the corruption of relevant memory, and perhaps instructions, possibly leading to a crash. Other attacks leading to lack of availability are possible, including putting the program into an infinite loop. |
| Confidentiality | Read Memory | In the case of an out-of-bounds read, the attacker may have access to sensitive information. If the sensitive information contains system details, such as the current buffers position in memory, this knowledge can be used to craft further attacks, possibly with more severe consequences. |
可能的缓解方案
Implementation
策略: Input Validation
Always verify the length of the string unit character.
Implementation
策略: Libraries or Frameworks
Use length computing functions (e.g. strlen, wcslen, etc.) appropriately with their equivalent type (e.g.: byte, wchar_t, etc.)
示例代码
例
The following example would be exploitable if any of the commented incorrect malloc calls were used.
bad C
#include
#include
int main() {
wchar_t wideString[] = L"The spazzy orange tiger jumped "
"over the tawny jaguar.";
wchar_t newString;
printf("Strlen() output: %dnWcslen() output: %dn",
strlen(wideString), wcslen(wideString));
/
Wrong because the number of chars in a string isn't related to its length in bytes //newString = (wchar_t ) malloc(strlen(wideString));
/
/ Wrong because wide characters aren't 1 byte long! //
newString = (wchar_t ) malloc(wcslen(wideString));
/
/ Wrong because wcslen does not include the terminating null /
newString = (wchar_t ) malloc(wcslen(wideString) * sizeof(wchar_t));
/ correct! /
newString = (wchar_t ) malloc((wcslen(wideString) + 1) * sizeof(wchar_t));
/ ... */
}
The output from the printf() statement would be:
result
Wcslen() output: 53
分类映射
| 映射的分类名 | ImNode ID | Fit | Mapped Node Name |
|---|---|---|---|
| CLASP | Improper string length checking | ||
| The CERT Oracle Secure Coding Standard for Java (2011) | FIO10-J | Ensure the array is filled when using read() to fill an array | |
| Software Fault Patterns | SFP10 | Incorrect Buffer Length Computation |
引用
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