[英]Security Vulnerability : What is the error in this piece of code?
I was reading this book on my own , just for fun , and came across the following question : 我只是为了娱乐而独自阅读这本书 ,遇到了以下问题:
This code has a security vulnerability ;
此代码存在安全漏洞; Can you find and fix it?
您可以找到并修复它吗? :
:
bool isValidAddition(unsigned short x, unsigned short y)
{
if(x + y < x)
return false;
else
return true;
}
Can someone help me , recognize the vulnerability ? 有人可以帮助我,识别此漏洞吗?
We know that the following points are true as per the C Standard
: 我们知道,根据
C Standard
,以下几点是正确的:
- sizeof(short) <= sizeof(int) <= sizeof(long)
sizeof(short)<= sizeof(int)<= sizeof(long)
- sizeof(short) >= 2 bytes , sizeof(int) >= 2 bytes, sizeof(long) >= 4 bytes
sizeof(short)> = 2个字节,sizeof(int)> = 2个字节,sizeof(long)> = 4个字节
- There is an implicit integer promotion of operand data types used in arithmetic expressions which is done by the compiler
算术表达式中使用了操作数数据类型的隐式整数提升,这是由编译器完成的
So in the code snippet above do the following : 因此,在上面的代码段中,请执行以下操作:
Change 更改
if(x + y < x)
to 至
if((unsigned short)(x + y) < x)
This will worrk if int is 4 (or >2) bytes 如果int是4(或> 2)个字节,这将很麻烦
Hope this helps :) 希望这可以帮助 :)
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