CWE-464 对数据结构哨兵域的增加

Addition of Data Structure Sentinel

结构: Simple

Abstraction: Base

状态: Incomplete

被利用可能性: High

基本描述

The accidental addition of a data-structure sentinel can cause serious programming logic problems.

扩展描述

Data-structure sentinels are often used to mark the structure of data. A common example of this is the null character at the end of strings or a special sentinel to mark the end of a linked list. It is dangerous to allow this type of control data to be easily accessible. Therefore, it is important to protect from the addition or modification of sentinels.

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	Modify Application Data	Generally this error will cause the data structure to not work properly by truncating the data.

可能的缓解方案

['Implementation', 'Architecture and Design']

策略:

Encapsulate the user from interacting with data sentinels. Validate user input to verify that sentinels are not present.

Implementation

策略:

Proper error checking can reduce the risk of inadvertently introducing sentinel values into data. For example, if a parsing function fails or encounters an error, it might return a value that is the same as the sentinel.

Architecture and Design

策略:

Use an abstraction library to abstract away risky APIs. This is not a complete solution.

Operation

策略:

Use OS-level preventative functionality. This is not a complete solution.

示例代码

例

The following example assigns some character values to a list of characters and prints them each individually, and then as a string. The third character value is intended to be an integer taken from user input and converted to an int.

bad C

char foo;
foo=malloc(sizeof(char)5);
foo[0]='a';
foo[1]='a';
foo[2]=atoi(getc(stdin));
foo[3]='c';
foo[4]='\0'
printf("%c %c %c %c %c \n",foo[0],foo[1],foo[2],foo[3],foo[4]);
printf("%s\n",foo);

The first print statement will print each character separated by a space. However, if a non-integer is read from stdin by getc, then atoi will not make a conversion and return 0. When foo is printed as a string, the 0 at character foo[2] will act as a NULL terminator and foo[3] will never be printed.

分类映射

映射的分类名	ImNode ID	Mapped Node Name
CLASP		Addition of data-structure sentinel
CERT C Secure Coding	STR03-C	Do not inadvertently truncate a null-terminated byte string
CERT C Secure Coding	STR06-C	Do not assume that strtok() leaves the parse string unchanged

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