CWE-124 缓冲区下溢
Buffer Underwrite ('Buffer Underflow')
结构: Simple
Abstraction: Base
状态: Incomplete
被利用可能性: Medium
基本描述
The software writes to a buffer using an index or pointer that references a memory location prior to the beginning of the buffer.
扩展描述
This typically occurs when a pointer or its index is decremented to a position before the buffer, when pointer arithmetic results in a position before the beginning of the valid memory location, or when a negative index is used.
相关缺陷
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cwe_Nature: ChildOf cwe_CWE_ID: 786 cwe_View_ID: 1000 cwe_Ordinal: Primary
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cwe_Nature: ChildOf cwe_CWE_ID: 786 cwe_View_ID: 699 cwe_Ordinal: Primary
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cwe_Nature: ChildOf cwe_CWE_ID: 787 cwe_View_ID: 1000
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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 |
|---|---|---|
| ['Integrity', 'Availability'] | ['Modify Memory', 'DoS: Crash, Exit, or Restart'] | Out of bounds memory access will very likely result in the corruption of relevant memory, and perhaps instructions, possibly leading to a crash. |
| ['Integrity', 'Confidentiality', 'Availability', 'Access Control', 'Other'] | ['Execute Unauthorized Code or Commands', 'Modify Memory', 'Bypass Protection Mechanism', 'Other'] | If the corrupted memory can be effectively controlled, it may be possible to execute arbitrary code. If the corrupted memory is data rather than instructions, the system will continue to function with improper changes, possibly in violation of an implicit or explicit policy. The consequences would only be limited by how the affected data is used, such as an adjacent memory location that is used to specify whether the user has special privileges. |
| ['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. |
可能的缓解方案
策略:
Requirements specification: The choice could be made to use a language that is not susceptible to these issues.
Implementation
策略:
Sanity checks should be performed on all calculated values used as index or for pointer arithmetic.
示例代码
例
In the following C/C++ example, a utility function is used to trim trailing whitespace from a character string. The function copies the input string to a local character string and uses a while statement to remove the trailing whitespace by moving backward through the string and overwriting whitespace with a NUL character.
bad C
char message = malloc(sizeof(char)*(length+1));
// copy input string to a temporary string
char message[length+1];
int index;
for (index = 0; index message[index] = strMessage[index];
}
message[index] = ' ';
// trim trailing whitespace
int len = index-1;
while (isspace(message[len])) {
len--;
}
// return string without trailing whitespace
retMessage = message;
return retMessage;
}文章来源于互联网:scap中文网
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