src/writemod.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (c) 2004 Silicon Graphics, Inc.
 * All Rights Reserved.
 */

/*
 * tests out if access checking is done on write path
 * 1. opens with write perms
 * 2. fchmod to turn off write perms
 * 3. writes to file
 */

#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <string.h>
#include <fcntl.h>
#include <stdio.h>

int 
main(int argc, char* argv[])
{
    char *path;
    int fd;
    char *buf = "hi there\n";
    ssize_t x;
    int sts;

    if (argc != 2) {
	fprintf(stderr, "%s: requires path argument\n", argv[0]);
        return 1;
    }

    path = argv[1];

    printf("open for write \"%s\" with 777\n", path);
    fd = open(path, O_RDWR, 0777);
    if (fd == -1) {
	perror("open");
        return 1;
    }
    printf("remove perms on file\n");
    sts = fchmod(fd, 0);
    if (sts == -1) {
	perror("fchmod");
        return 1;
    }
    printf("write to the file\n");
    x = write(fd, buf, strlen(buf));
    if (x == -1) {
	perror("write");
        return 1;
    }
    return 0;
}