파일접근에대한 시스템 콜을 후킹하려합니다.

CC = gcc
CFLAGS = -O -Wall -g
 
OBJS = test.o myopen.o
 
SRCS =  test.c
 
LIBHOOK = ./libmy.so.1
HEADERS =
 
test:   $(OBJS) $(LIBHOOK)
            $(CC)   $(CFLAGS) -o test   $(OBJS) -L. $(LIBHOOK)
 
$(OBJS):    $(HERADERS) Makefile
 
all:    test
 
$(LIBHOOK): myopen.c
    $(CC) -fPIC -rdynamic -g -c -Wall myopen.c
    $(CC) -shared -Wl,-soname,libmy.so.1 -o $(LIBHOOK) myopen.o -lc -ldl
    export LD_PRELOAD=$(LIBHOOK)
 
 
clean:
    rm -f $(OBJS) test $(LIBHOOK)

#define _GNU_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <dlfcn.h>
#include <unistd.h>
 
#include <stdarg.h>
#include <time.h>
 
 char timeBuf[1024]; // TODO: Global~~~ --;
 
char *timeStr()
{
    time_t now;
    char *fmt =  "%Y-%m-%d %H:%M:%S";
    int len;
 
 
    time(&now);
 
    len = strftime(timeBuf,sizeof timeBuf, fmt, localtime(&now));
 
    return timeBuf;
}
 
int open(const char *path, int oflag, ...  )
{
    va_list argptr;
    static int (*orig_open)(const char *path, int oflag, ...) = NULL;
    char *error;
    int result;
 
    if(!orig_open){
        orig_open = dlsym(RTLD_NEXT, "open");
        if((error=dlerror()) != NULL){
            //fputs("error",stderr);
            write(2, "error \n", 7);
            exit(EXIT_FAILURE);
        }
    }
    fprintf(stderr, ">>%s   uid = %d getcwd= %s open '%s' file\n", timeStr(), getuid(), get_current_dir_name(), path);
 
    va_start(argptr, oflag);
    result = (*orig_open)(path, oflag, argptr);
    va_end(argptr);
 
    return result;
}

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
 
int main()
{
    int fd;
    char buf[1024];
    int ret;
 
   fd = open("test.c", O_RDONLY, 0666);
   if ( fd < 0 ) {
        perror("open");
        exit(0);
    }
    while(1) {
        ret = read(fd, buf, 1024);
        if ( ret < 0 ) {
            perror("read");
            break;
        }
        else if (ret == 0 ) {
            //perror("EOF !");
            break;
        }
        else {
        //  write(1, buf, ret); // TODO : return value. check.
        }
 
    }
 
   close(fd);
    return 0;
}