/* $Id: mount.vboxsf.c 69500 2017-10-28 15:14:05Z vboxsync $ */
/** @file
 * VirtualBox Guest Additions for Linux - mount(8) helper.
 *
 * Parses options provided by mount (or user directly)
 * Packs them into struct vbsfmount and passes to mount(2)
 * Optionally adds entries to mtab
 */

/*
 * Copyright (C) 2006-2017 Oracle Corporation
 *
 * This file is part of VirtualBox Open Source Edition (OSE), as
 * available from http://www.virtualbox.org. This file is free software;
 * you can redistribute it and/or modify it under the terms of the GNU
 * General Public License (GPL) as published by the Free Software
 * Foundation, in version 2 as it comes in the "COPYING" file of the
 * VirtualBox OSE distribution. VirtualBox OSE is distributed in the
 * hope that it will be useful, but WITHOUT ANY WARRANTY of any kind.
 */


#ifndef _GNU_SOURCE
# define _GNU_SOURCE
#endif

/* #define DEBUG */
#include <errno.h>
#include <fcntl.h>
#include <ctype.h>
#include <getopt.h>
#include <mntent.h>
#include <pwd.h>
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/mount.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>
#include <mntent.h>
#include <limits.h>
#include <iconv.h>

#include "vbsfmount.h"

#include <iprt/assert.h>


#define PANIC_ATTR __attribute ((noreturn, __format__ (__printf__, 1, 2)))

static void PANIC_ATTR
panic(const char *fmt, ...)
{
    va_list ap;

    va_start(ap, fmt);
    vfprintf(stderr, fmt, ap);
    va_end(ap);
    exit(EXIT_FAILURE);
}

static void PANIC_ATTR
panic_err(const char *fmt, ...)
{
    va_list ap;
    int errno_code = errno;

    va_start(ap, fmt);
    vfprintf(stderr, fmt, ap);
    va_end(ap);
    fprintf(stderr, ": %s\n", strerror(errno_code));
    exit(EXIT_FAILURE);
}

static int
safe_atoi(const char *s, size_t size, int base)
{
    char *endptr;
    long long int val = strtoll(s, &endptr, base);

    if (val < INT_MIN || val > INT_MAX || endptr < s + size)
    {
        errno = ERANGE;
        panic_err("could not convert %.*s to integer, result = %d",
                   (int)size, s, (int) val);
    }
    return (int)val;
}

static void
process_mount_opts(const char *s, struct vbsf_mount_opts *opts)
{
    const char *next = s;
    size_t len;
    typedef enum handler_opt
    {
        HORW,
        HORO,
        HOUID,
        HOGID,
        HOTTL,
        HODMODE,
        HOFMODE,
        HOUMASK,
        HODMASK,
        HOFMASK,
        HOIOCHARSET,
        HOCONVERTCP,
        HONOEXEC,
        HOEXEC,
        HONODEV,
        HODEV,
        HONOSUID,
        HOSUID,
        HOREMOUNT,
        HONOAUTO,
        HONIGNORE
    } handler_opt;
    struct
    {
        const char *name;
        handler_opt opt;
        int has_arg;
        const char *desc;
    } handlers[] =
    {
        {"rw",        HORW,        0, "mount read write (default)"},
        {"ro",        HORO,        0, "mount read only"},
        {"uid",       HOUID,       1, "default file owner user id"},
        {"gid",       HOGID,       1, "default file owner group id"},
        {"ttl",       HOTTL,       1, "time to live for dentry"},
        {"iocharset", HOIOCHARSET, 1, "i/o charset (default utf8)"},
        {"convertcp", HOCONVERTCP, 1, "convert share name from given charset to utf8"},
        {"dmode",     HODMODE,     1, "mode of all directories"},
        {"fmode",     HOFMODE,     1, "mode of all regular files"},
        {"umask",     HOUMASK,     1, "umask of directories and regular files"},
        {"dmask",     HODMASK,     1, "umask of directories"},
        {"fmask",     HOFMASK,     1, "umask of regular files"},
        {"noexec",    HONOEXEC,    0, 0 }, /* don't document these options directly here */
        {"exec",      HOEXEC,      0, 0 }, /* as they are well known and described in the */
        {"nodev",     HONODEV,     0, 0 }, /* usual manpages */
        {"dev",       HODEV,       0, 0 },
        {"nosuid",    HONOSUID,    0, 0 },
        {"suid",      HOSUID,      0, 0 },
        {"remount",   HOREMOUNT,   0, 0 },
        {"noauto",    HONOAUTO,    0, 0 },
        {"_netdev",   HONIGNORE,   0, 0 },
        {NULL, 0, 0, NULL}
    }, *handler;

    while (next)
    {
        const char *val;
        size_t key_len, val_len;

        s = next;
        next = strchr(s, ',');
        if (!next)
        {
            len = strlen(s);
        }
        else
        {
            len = next - s;
            next += 1;
            if (!*next)
                next = 0;
        }

        val = NULL;
        val_len = 0;
        for (key_len = 0; key_len < len; ++key_len)
        {
            if (s[key_len] == '=')
            {
                if (key_len + 1 < len)
                {
                    val = s + key_len + 1;
                    val_len = len - key_len - 1;
                }
                break;
            }
        }

        for (handler = handlers; handler->name; ++handler)
        {
            size_t j;
            for (j = 0; j < key_len && handler->name[j] == s[j]; ++j)
                ;

            if (j == key_len && !handler->name[j])
            {
                if (handler->has_arg)
                {
                    if (!(val && *val))
                    {
                        panic("%.*s requires an argument (i.e. %.*s=<arg>)\n",
                               (int)len, s, (int)len, s);
                    }
                }

                switch(handler->opt)
                {
                case HORW:
                    opts->ronly = 0;
                    break;
                case HORO:
                    opts->ronly = 1;
                    break;
                case HONOEXEC:
                    opts->noexec = 1;
                    break;
                case HOEXEC:
                    opts->noexec = 0;
                    break;
                case HONODEV:
                    opts->nodev = 1;
                    break;
                case HODEV:
                    opts->nodev = 0;
                    break;
                case HONOSUID:
                    opts->nosuid = 1;
                    break;
                case HOSUID:
                    opts->nosuid = 0;
                    break;
                case HOREMOUNT:
                    opts->remount = 1;
                    break;
                case HOUID:
                    /** @todo convert string to id. */
                    opts->uid = safe_atoi(val, val_len, 10);
                    break;
                case HOGID:
                    /** @todo convert string to id. */
                    opts->gid = safe_atoi(val, val_len, 10);
                    break;
                case HOTTL:
                    opts->ttl = safe_atoi(val, val_len, 10);
                    break;
                case HODMODE:
                    opts->dmode = safe_atoi(val, val_len, 8);
                    break;
                case HOFMODE:
                    opts->fmode = safe_atoi(val, val_len, 8);
                    break;
                case HOUMASK:
                    opts->dmask = opts->fmask = safe_atoi(val, val_len, 8);
                    break;
                case HODMASK:
                    opts->dmask = safe_atoi(val, val_len, 8);
                    break;
                case HOFMASK:
                    opts->fmask = safe_atoi(val, val_len, 8);
                    break;
                case HOIOCHARSET:
                    if (val_len + 1 > sizeof(opts->nls_name))
                    {
                        panic("iocharset name too long\n");
                    }
                    memcpy(opts->nls_name, val, val_len);
                    opts->nls_name[val_len] = 0;
                    break;
                case HOCONVERTCP:
                    opts->convertcp = malloc(val_len + 1);
                    if (!opts->convertcp)
                    {
                        panic_err("could not allocate memory");
                    }
                    memcpy(opts->convertcp, val, val_len);
                    opts->convertcp[val_len] = 0;
                    break;
                case HONOAUTO:
                case HONIGNORE:
                    break;
                }
                break;
            }
            continue;
        }

        if (   !handler->name
            && !opts->sloppy)
        {
            fprintf(stderr, "unknown mount option `%.*s'\n", (int)len, s);
            fprintf(stderr, "valid options:\n");

            for (handler = handlers; handler->name; ++handler)
            {
                if (handler->desc)
                    fprintf(stderr, "  %-10s%s %s\n", handler->name,
                         handler->has_arg ? "=<arg>" : "", handler->desc);
            }
            exit(EXIT_FAILURE);
        }
    }
}

static void
convertcp(char *in_codeset, char *host_name, struct vbsf_mount_info_new *info)
{
    char *i = host_name;
    char *o = info->name;
    size_t ib = strlen(host_name);
    size_t ob = sizeof(info->name) - 1;
    iconv_t cd;

    cd = iconv_open("UTF-8", in_codeset);
    if (cd == (iconv_t) -1)
    {
        panic_err("could not convert share name, iconv_open `%s' failed",
                   in_codeset);
    }

    while (ib)
    {
        size_t c = iconv(cd, &i, &ib, &o, &ob);
        if (c == (size_t) -1)
        {
            panic_err("could not convert share name(%s) at %d",
                      host_name, (int)(strlen (host_name) - ib));
        }
    }
    *o = 0;
}


/**
  * Print out a usage message and exit.
  *
  * @returns 1
  * @param   argv0      The name of the application
  */
static int usage(char *argv0)
{
    printf("Usage: %s [OPTIONS] NAME MOUNTPOINT\n"
           "Mount the VirtualBox shared folder NAME from the host system to MOUNTPOINT.\n"
           "\n"
           "  -w                    mount the shared folder writable (the default)\n"
           "  -r                    mount the shared folder read-only\n"
           "  -n                    do not create an mtab entry\n"
           "  -s                    sloppy parsing, ignore unrecognized mount options\n"
           "  -o OPTION[,OPTION...] use the mount options specified\n"
           "\n", argv0);
    printf("Available mount options are:\n"
           "     rw                 mount writable (the default)\n"
           "     ro                 mount read only\n"
           "     uid=UID            set the default file owner user id to UID\n"
           "     gid=GID            set the default file owner group id to GID\n"
           "     ttl=TTL            set the \"time to live\" to TID for the dentry\n");
    printf("     dmode=MODE         override the mode of all directories to (octal) MODE\n"
           "     fmode=MODE         override the mode of all regular files to (octal) MODE\n"
           "     umask=UMASK        set the umask to (octal) UMASK\n");
    printf("     dmask=UMASK        set the umask applied to directories only\n"
           "     fmask=UMASK        set the umask applied to regular files only\n"
           "     iocharset CHARSET  use the character set CHARSET for I/O operations\n"
           "                        (default set is utf8)\n"
           "     convertcp CHARSET  convert the folder name from CHARSET to utf8\n"
           "\n");
    printf("Less common used options:\n"
           "     noexec,exec,nodev,dev,nosuid,suid\n");
    return EXIT_FAILURE;
}

int
main(int argc, char **argv)
{
    int c;
    int err;
    int nomtab = 0;
    unsigned long flags = MS_NODEV;
    char *host_name;
    char *mount_point;
    struct vbsf_mount_info_new mntinf;
    struct vbsf_mount_opts opts =
    {
        0,     /* uid */
        0,     /* gid */
        0,     /* ttl */
       ~0U,    /* dmode */
       ~0U,    /* fmode*/
        0,     /* dmask */
        0,     /* fmask */
        0,     /* ronly */
        0,     /* sloppy */
        0,     /* noexec */
        0,     /* nodev */
        0,     /* nosuid */
        0,     /* remount */
        "\0",  /* nls_name */
        NULL,  /* convertcp */
    };
    AssertCompile(sizeof(uid_t) == sizeof(int));
    AssertCompile(sizeof(gid_t) == sizeof(int));

    mntinf.nullchar = '\0';
    mntinf.signature[0] = VBSF_MOUNT_SIGNATURE_BYTE_0;
    mntinf.signature[1] = VBSF_MOUNT_SIGNATURE_BYTE_1;
    mntinf.signature[2] = VBSF_MOUNT_SIGNATURE_BYTE_2;
    mntinf.length       = sizeof(mntinf);

    if (getuid())
        panic("Only root can mount shared folders from the host.\n");

    if (!argv[0])
        argv[0] = "mount.vboxsf";

    while ((c = getopt(argc, argv, "rwsno:h")) != -1)
    {
        switch (c)
        {
            default:
                fprintf(stderr, "unknown option `%c:%#x'\n", c, c);
                RT_FALL_THRU();
            case '?':
            case 'h':
                return usage(argv[0]);

            case 'r':
                opts.ronly = 1;
                break;

            case 'w':
                opts.ronly = 0;
                break;

            case 's':
                opts.sloppy = 1;
                break;

            case 'o':
                process_mount_opts(optarg, &opts);
                break;

            case 'n':
                nomtab = 1;
                break;
        }
    }

    if (argc - optind < 2)
        return usage(argv[0]);

    host_name = argv[optind];
    mount_point = argv[optind + 1];

    if (opts.convertcp)
        convertcp(opts.convertcp, host_name, &mntinf);
    else
    {
        if (strlen(host_name) > MAX_HOST_NAME - 1)
            panic("host name is too big\n");

        strcpy(mntinf.name, host_name);
    }

    if (strlen(opts.nls_name) > MAX_NLS_NAME - 1)
        panic("%s: the character set name for I/O is too long.\n", argv[0]);

    strcpy(mntinf.nls_name, opts.nls_name);

    if (opts.ronly)
        flags |= MS_RDONLY;
    if (opts.noexec)
        flags |= MS_NOEXEC;
    if (opts.nodev)
        flags |= MS_NODEV;
    if (opts.remount)
        flags |= MS_REMOUNT;

    mntinf.uid   = opts.uid;
    mntinf.gid   = opts.gid;
    mntinf.ttl   = opts.ttl;
    mntinf.dmode = opts.dmode;
    mntinf.fmode = opts.fmode;
    mntinf.dmask = opts.dmask;
    mntinf.fmask = opts.fmask;

    /*
     * Note: When adding and/or modifying parameters of the vboxsf mounting
     *       options you also would have to adjust VBoxServiceAutoMount.cpp
     *       to keep this code here slick without having VbglR3.
     */
    err = mount(host_name, mount_point, "vboxsf", flags, &mntinf);
    if (err == -1 && errno == EPROTO)
    {
        /* Sometimes the mount utility messes up the share name.  Try to
         * un-mangle it again. */
        char szCWD[4096];
        size_t cchCWD;
        if (!getcwd(szCWD, sizeof(szCWD)))
            panic_err("%s: failed to get the current working directory", argv[0]);
        cchCWD = strlen(szCWD);
        if (!strncmp(host_name, szCWD, cchCWD))
        {
            while (host_name[cchCWD] == '/')
                ++cchCWD;
            /* We checked before that we have enough space */
            strcpy(mntinf.name, host_name + cchCWD);
        }
        err = mount(host_name, mount_point, "vboxsf", flags, &mntinf);
    }
    if (err)
        panic_err("%s: mounting failed with the error", argv[0]);

    if (!nomtab)
    {
        err = vbsfmount_complete(host_name, mount_point, flags, &opts);
        switch (err)
        {
            case 0: /* Success. */
                break;

            case 1:
                panic_err("%s: Could not update mount table (failed to create memstream).", argv[0]);
                break;

            case 2:
                panic_err("%s: Could not open mount table for update.", argv[0]);
                break;

            case 3:
                /* panic_err("%s: Could not add an entry to the mount table.", argv[0]); */
                break;

            default:
                panic_err("%s: Unknown error while completing mount operation: %d", argv[0], err);
                break;
        }
    }

    exit(EXIT_SUCCESS);
}