Shellcode in C program
c, shellcode
Solution
int (*ret)() = (int(*)())code;
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It defines `ret` as a pointer to a function which has no parameter `()` and returns `int`. So, Those `()` indicates the definition of parameters of a function.
It's for casting `code` to a pointer to a function which has no parameter `()` and returns `int`.
Casts `code` as a function and assigns it to `ret`. After that you can call `ret();`.
unsigned char code[] = "\x31\xc0\x50\x68\x6e\x2f\...
It is a sequence of machine instructions represented by hex values. It will be injected to the code as a function.
Problem
In Demystifying the Execve Shellcode is explained a way to write an execve shellcode: ``` #include<stdio.h> #include<string.h> unsigned char code[] = "\x31\xc0\x50\x68\x6e\x2f\x73\x68\x68\x2f\x2f\x62\x69\x89\xe3\x50\x89\xe2\x53\x89\xe1\xb0\x0b\xcd\x80"; main() { printf("Shellcode Length: %d\n", strlen(code)); int (*ret)() = (int(*)())code; ret(); } ``` What does the line `int (*ret)() = (int(*)())code;` do?