安全漏洞：这段代码有什么错误？

Question

我在自己阅读 this book 时，只是为了好玩，遇到了以下问题：

This code has a security vulnerability ; Can you find and fix it? :

  bool isValidAddition(unsigned short x, unsigned short y) 
 {
     if(x + y < x)
         return false;
     else 
         return true;
 }

有人可以帮助我识别漏洞吗？

Answer 1

根据 C Standard 我们知道以下几点是正确的：

sizeof(short) <= sizeof(int) <= sizeof(long)

sizeof(short) >= 2 bytes , sizeof(int) >= 2 bytes, sizeof(long) >= 4 bytes

There is an implicit integer promotion of operand data types used in arithmetic expressions which is done by the compiler

所以在上面的代码片段中执行以下操作：

改变

if(x + y < x)

到

if((unsigned short)(x + y) < x)

如果 int 是 4（或 >2）字节，这将起作用

希望这对您有所帮助:)

安全漏洞：这段代码有什么错误？

Security Vulnerability : What is the error in this piece of code?

c

security

integer-overflow