Preload read() to exit() on EOF

exit-on-EOF.c

#define _GNU_SOURCE
#include <dlfcn.h>
#include <stdio.h>
#include <stdlib.h>

/* gcc -shared -fPIC exit-on-EOF.c -o exit-on-EOF.so -ldl */
/* LD_PRELOAD=./exit-on-EOF.so ./test */
/* AFL_PRELOAD=./exit-on-EOF.so afl-fuzz -i in -o out -n -- ./test */

typedef int (*orig_read_f_type)(int fd, void *buf, int count);

int read(int fd, void *buf, int count) {
    orig_read_f_type orig_read = (orig_read_f_type)dlsym(RTLD_NEXT, "read");
    for (int i = 0; i < count; ++i) {
        int n = orig_read(fd, buf++, 1);
        if (n == 0) {
            printf("EOF!\n");
            exit(-1337);
        }
    }
    return count;
}

test.c

#include <stdio.h>
#include <unistd.h>

int main(int argc, char const *argv[]) {
    char c;
    do {
        read(STDIN_FILENO, &c, 1);
        printf("%c", c);
    }
    while(1);
    return 0;
}