CWE-481 错误将比较符号写成赋值符号
Assigning instead of Comparing
结构: Simple
Abstraction: Variant
状态: Draft
被利用可能性: Low
基本描述
The code uses an operator for assignment when the intention was to perform a comparison.
扩展描述
In many languages the compare statement is very close in appearance to the assignment statement and are often confused. This bug is generally the result of a typo and usually causes obvious problems with program execution. If the comparison is in an if statement, the if statement will usually evaluate the value of the right-hand side of the predicate.
相关缺陷
-
cwe_Nature: ChildOf cwe_CWE_ID: 480 cwe_View_ID: 1000 cwe_Ordinal: Primary
-
cwe_Nature: ChildOf cwe_CWE_ID: 480 cwe_View_ID: 699 cwe_Ordinal: Primary
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cwe_Nature: CanPrecede cwe_CWE_ID: 697 cwe_View_ID: 1000
适用平台
Language: [{'cwe_Name': 'C', 'cwe_Prevalence': 'Undetermined'}, {'cwe_Name': 'C++', 'cwe_Prevalence': 'Undetermined'}, {'cwe_Name': 'Java', 'cwe_Prevalence': 'Undetermined'}, {'cwe_Name': 'C#', 'cwe_Prevalence': 'Undetermined'}]
常见的影响
| 范围 | 影响 | 注释 |
|---|---|---|
| Other | Alter Execution Logic |
可能的缓解方案
Testing
策略:
Many IDEs and static analysis products will detect this problem.
Implementation
策略:
Place constants on the left. If one attempts to assign a constant with a variable, the compiler will of course produce an error.
示例代码
例
The following C/C++ and C# examples attempt to validate an int input parameter against the integer value 100.
bad C
return(1);
}
printf("Value is not validn");
return(0);
}
bad C#
return true;
}
Console.WriteLine("Value is not valid.");
return false;
}
However, the expression to be evaluated in the if statement uses the assignment operator "=" rather than the comparison operator "==". The result of using the assignment operator instead of the comparison operator causes the int variable to be reassigned locally and the expression in the if statement will always evaluate to the value on the right hand side of the expression. This will result in the input value not being properly validated, which can cause unexpected results.
例
In this example, we show how assigning instead of comparing can impact code when values are being passed by reference instead of by value. Consider a scenario in which a string is being processed from user input. Assume the string has already been formatted such that different user inputs are concatenated with the colon character. When the processString function is called, the test for the colon character will result in an insertion of the colon character instead, adding new input separators. Since the string was passed by reference, the data sentinels will be inserted in the original string (CWE-464), and further processing of the inputs will be altered, possibly malformed..
bad C
for(i=0; i
}
else if (str[i] = ':') {
}
}
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