#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <limits.h>
#include <errno.h>
#include <mntent.h>
#include <paths.h>
#include <fcntl.h>
#include <string.h>

#include <sys/types.h>
#include <sys/mount.h>
#include <sys/stat.h>

#define ERROR(x...)	fprintf(stderr, x)

static void
help(){
    printf("\n");
    printf("Usage: lufsmnt mount-point [options]\n");
    printf("This is a suid wrapper called by lufsd.\n");

}

static int
fullpath(char *path, char *full){
    
    full[0] = 0;
    
    if(strlen(path) >= PATH_MAX - 1)
	return -1;

    if(!realpath(path, full))
	return -1;
    else 
	return 0;
}

static int
mount_ok(char *mp){
    struct stat st;
    
    if(chdir(mp)){
	ERROR("cannot chdir %s\n", mp);
	return -1;
    }
	
    if(stat(".", &st)){
	ERROR("cannot stat %s\n", mp);
	return -1;
    }
	
    if(!S_ISDIR(st.st_mode)){
	ERROR("%s is not a directory\n", mp);
	return -1;
    }

    if((getuid()) && ((getuid() != st.st_uid) || ((st.st_mode & S_IRWXU) != S_IRWXU))){
	ERROR("you don't have proper permissions to mount on %s\n", mp);
	return -1;
    }

    return 0;
}

void
hide_pass(char *opts){
    char *c;

    if((c = strstr(opts, "password="))){
	for(c = c + 9; (*c != 0) && (*c != ','); c++)
	    *c = '*';
    }
}

void
get_fs(char *opts, char *buf, int buflen){
    char *begin, *end;

    buf[0] = 0;
    buf[buflen - 1] = 0;

    if((begin = strstr(opts, "fs="))){
	begin += 3;
	
	if(!(end = strchr(begin, ','))){
	    end = begin + strlen(begin);
	}
	
	if( end - begin >= buflen)
	    end = begin + buflen - 1;

	strncpy(buf, begin, end - begin);
    }
}

int
main(int argc, char **argv){
    char *mountpoint, *opts;
    static char fpath[PATH_MAX];
    static char mfs[PATH_MAX];
    static char mopts[PATH_MAX];
    struct mntent ment;
    int fd;
    FILE *mtab;
    
    if(argc != 3){
	help();
	exit(1);
    }

    if(geteuid()){
	ERROR("%s needs to be installed suid root in order to be used by unprivileged users\n", argv[0]);
	exit(1);
    }
    
    mountpoint = argv[1];
    opts = argv[2];

    fullpath(mountpoint, fpath);
    
    if(mount_ok(fpath)){
	exit(1);
    }
        
    if (mount("none", fpath, "lufs", MS_NOSUID | MS_NODEV, opts) < 0){
	ERROR("mount failed: %s\n", strerror(errno));
	switch(errno){
	case ENODEV:
	    ERROR("you don't have kernel lufs support (check whether the lufs module is available/loaded)\n");
	    break;
	}
	return errno;
    }

    sprintf(mopts, "owner=%d,", getuid());
    hide_pass(opts);
    if(strlen(mopts) + strlen(opts) < PATH_MAX)
	strcat(mopts, opts);
    get_fs(opts, mfs, PATH_MAX);

    ment.mnt_fsname = mfs;
    ment.mnt_dir = fpath;
    ment.mnt_type = "lufs";
    ment.mnt_opts = mopts;
    ment.mnt_freq = 0;
    ment.mnt_passno = 0;

    if((fd = open(_PATH_MOUNTED"~", O_RDWR|O_CREAT|O_EXCL, 0600)) < 0){
	ERROR("can't get "_PATH_MOUNTED"~ lock file\n");
	return 1;
    }
    close(fd);
    
    if((mtab = setmntent(_PATH_MOUNTED, "a+")) == NULL){
	ERROR("can't open "_PATH_MOUNTED"\n");
	return 1;
    }
    
    if(addmntent(mtab, &ment)){
	ERROR("can't write mount entry\n");
	return 1;
    }
    
    if(fchmod(fileno(mtab), 0644) < 0){
	ERROR("can't set [erms on "_PATH_MOUNTED"\n");
	return 1;
    }
    
    endmntent(mtab);
    
    if(unlink(_PATH_MOUNTED"~") < 0){
	ERROR("can't remove "_PATH_MOUNTED"~\n");
	return 1;
    }
    
    return 0;
}