Shared library injection with the Witchcraft Compiler Collection

hook.c

#define _GNU_SOURCE
#include <dlfcn.h>

int puts(const char* s)
{
	int (*oputs)(const char*) = dlsym(RTLD_NEXT, "puts");
	oputs("HOOKED!");
	return oputs(s);
}

termlog

[~/rootkits/wcc-kit]$ gcc test.c -o test        
[~/rootkits/wcc-kit]$ gcc -fPIC -c hook.c -o hook.o # could also use WCC to make an object file from a .so
[~/rootkits/wcc-kit]$ ./test
Am I hooked?
[~/rootkits/wcc-kit]$ wcc -c ./test -o test.o
[~/rootkits/wcc-kit]$ gcc test.o hook.o -ldl -o test-hooked
[~/rootkits/wcc-kit]$ ./test-hooked 
HOOKED!
Am I hooked?

test.c

#include <stdio.h>


int main()
{
	puts("Am I hooked?");
}