Common CTF functions for LD_PRELOAD

funcs.c

/*
 * cc -Wall -o funcs.so -shared funcs.c -DENABLE_ALL
 *
 * LD_PRELOAD=./funcs.so ./target
 * or from inside gdb:
 * set environment LD_PRELOAD=./funcs.so
 */

#include <unistd.h>

#if defined(ENABLE_PTRACE) || defined(ENABLE_ALL)
#define PTRACE_TRACEME 0

long
ptrace(int request, pid_t pid, void *addr, void *data) {
        if (request == PTRACE_TRACEME) {
                return 0;
        }

        /* Default to returning 0 for unrecognized requests. */
        return 0;
}
#endif /* ENABLE_PTRACE */

#if defined(ENABLE_RAND) || defined(ENABLE_ALL)
int
rand(void) {
        /* Chosen by fair dice roll. Guaranteed to be random. */
        return 4;
}
#endif /* ENABLE_RAND */