How to write a shellcode

ShellCode 's writing is to change the function or variable in memory of the indirect address to a function or variable in memory of the direct address, directly call!

Take the MessageBox function as an example to explain the following

New shellcode.cpp:

Write the following code:

Operation Result:

Convert the VC code into assembly instructions:

Memory Data graph:

After the actual address of the function is found, the code is modified as follows:

Convert the above assembly instructions into binary data:

Memory Data graph:

copy binary data between 0x0040103c~0x00401049

As follows:

6A 6A xx 6A 6A xx B8 1E FD 0B D0 FF

Final shellcode code:

Operation Result:

How to write a shellcode