Type Mismatch: Negative to Unsigned

C/C++

Abstract

该函数声明为返回无符号值，但在某些情况下它会尝试返回负值。

Explanation

依赖在带符号和不带符号的数字之间进行隐式转换是很危险的，因为转换的结果可能是一个超出预料的值，并且会违反程序员在程序中所作的其他假设。

示例 1：在此示例中，变量 amount 在返回时可能包含负值。由于函数已声明为返回不带符号的整数，因此 amount 将隐式转换为无符号的值。


unsigned int readdata () {
	int amount = 0;
    ...
	if (result == ERROR)
		amount = -1;
	...
	return amount;
}

如果满足Example 1 中的错误条件，则 readdata() 的返回值在使用 32 位整型的系统上将为 4,294,967,295。

在带符号和不带符号的值之间进行转换会引发各种错误，但从安全性角度来说，最常见的是引发 integer overflow 和 buffer overflow 漏洞。

References

[1] Standards Mapping - Common Weakness Enumeration CWE ID 195

[2] Standards Mapping - DISA Control Correlation Identifier Version 2 CCI-002824

[3] Standards Mapping - Motor Industry Software Reliability Association (MISRA) C Guidelines 2012 Rule 10.3

[4] Standards Mapping - Motor Industry Software Reliability Association (MISRA) C Guidelines 2023 Rule 7.5, Rule 7.6, Rule 10.3, Rule 21.18

[5] Standards Mapping - Motor Industry Software Reliability Association (MISRA) C++ Guidelines 2008 Rule 5-0-3

[6] Standards Mapping - Motor Industry Software Reliability Association (MISRA) C++ Guidelines 2023 Rule 7.0.5, Rule 7.0.6

[7] Standards Mapping - NIST Special Publication 800-53 Revision 4 SI-16 Memory Protection (P1)

[8] Standards Mapping - NIST Special Publication 800-53 Revision 5 SI-16 Memory Protection

[9] Standards Mapping - Payment Card Industry Data Security Standard Version 3.0 Requirement 6.5.6

[10] Standards Mapping - Payment Card Industry Data Security Standard Version 3.1 Requirement 6.5.6

[11] Standards Mapping - Payment Card Industry Data Security Standard Version 3.2 Requirement 6.5.6

[12] Standards Mapping - Payment Card Industry Data Security Standard Version 3.2.1 Requirement 6.5.6

[13] Standards Mapping - Payment Card Industry Data Security Standard Version 4.0 Requirement 6.2.4

[14] Standards Mapping - Payment Card Industry Data Security Standard Version 4.0.1 Requirement 6.2.4

[15] Standards Mapping - Payment Card Industry Software Security Framework 1.0 Control Objective 4.2 - Critical Asset Protection

[16] Standards Mapping - Payment Card Industry Software Security Framework 1.1 Control Objective 4.2 - Critical Asset Protection

[17] Standards Mapping - Payment Card Industry Software Security Framework 1.2 Control Objective 4.2 - Critical Asset Protection

[18] Standards Mapping - Security Technical Implementation Guide Version 3.1 APP3550 CAT I

[19] Standards Mapping - Security Technical Implementation Guide Version 3.4 APP3550 CAT I

[20] Standards Mapping - Security Technical Implementation Guide Version 3.5 APP3550 CAT I

[21] Standards Mapping - Security Technical Implementation Guide Version 3.6 APP3550 CAT I

[22] Standards Mapping - Security Technical Implementation Guide Version 3.7 APP3550 CAT I

[23] Standards Mapping - Security Technical Implementation Guide Version 3.9 APP3550 CAT I

[24] Standards Mapping - Security Technical Implementation Guide Version 3.10 APP3550 CAT I

[25] Standards Mapping - Security Technical Implementation Guide Version 4.2 APSC-DV-002590 CAT I

[26] Standards Mapping - Security Technical Implementation Guide Version 4.3 APSC-DV-002590 CAT I

[27] Standards Mapping - Security Technical Implementation Guide Version 4.4 APSC-DV-002590 CAT I

[28] Standards Mapping - Security Technical Implementation Guide Version 4.5 APSC-DV-002590 CAT I

[29] Standards Mapping - Security Technical Implementation Guide Version 4.6 APSC-DV-002590 CAT I

[30] Standards Mapping - Security Technical Implementation Guide Version 4.7 APSC-DV-002590 CAT I

[31] Standards Mapping - Security Technical Implementation Guide Version 4.8 APSC-DV-002590 CAT I

[32] Standards Mapping - Security Technical Implementation Guide Version 4.9 APSC-DV-002590 CAT I

[33] Standards Mapping - Security Technical Implementation Guide Version 4.10 APSC-DV-002590 CAT I

[34] Standards Mapping - Security Technical Implementation Guide Version 4.11 APSC-DV-002590 CAT I

[35] Standards Mapping - Security Technical Implementation Guide Version 4.1 APSC-DV-002590 CAT I

[36] Standards Mapping - Security Technical Implementation Guide Version 5.1 APSC-DV-002590 CAT I

[37] Standards Mapping - Security Technical Implementation Guide Version 5.2 APSC-DV-002590 CAT I

[38] Standards Mapping - Security Technical Implementation Guide Version 5.3 APSC-DV-002590 CAT I

[39] Standards Mapping - Security Technical Implementation Guide Version 6.1 APSC-DV-002590 CAT I

desc.structural.cpp.type_mismatch_negative_to_unsigned