libinstaller/fs.c

   1 /* ----------------------------------------------------------------------- *
   2  *
   3  *   Copyright 1998-2011 H. Peter Anvin - All Rights Reserved
   4  *   Copyright 2009-2011 Intel Corporation; author H. Peter Anvin
   5  *   Copyright 2011 Paulo Alcantara <pcacjr@gmail.com>
   6  *
   7  *   This program is free software; you can redistribute it and/or modify
   8  *   it under the terms of the GNU General Public License as published by
   9  *   the Free Software Foundation, Inc., 53 Temple Place Ste 330,
  10  *   Boston MA 02111-1307, USA; either version 2 of the License, or
  11  *   (at your option) any later version; incorporated herein by reference.
  12  *
  13  * ----------------------------------------------------------------------- */
  14
  15 /*
  16  * fs.c - Generic sanity check for FAT/NTFS-based installers
  17  */
  18
  19 #define _XOPEN_SOURCE 500       /* Required on glibc 2.x */
  20 #define _BSD_SOURCE
  21 #include <stdio.h>
  22 #include <inttypes.h>
  23 #include <string.h>
  24 #include <stddef.h>
  25 #include <stdlib.h>
  26
  27 #include "syslinux.h"
  28 #include "syslxint.h"
  29 #include "syslxcom.h"
  30 #include "syslxfs.h"
  31
  32 void syslinux_make_bootsect(void *bs, int fs_type)
  33 {
  34     if (fs_type == VFAT) {
  35         struct fat_boot_sector *bootsect = bs;
  36         const struct fat_boot_sector *sbs =
  37             (const struct fat_boot_sector *)boot_sector;
  38
  39         memcpy(&bootsect->FAT_bsHead, &sbs->FAT_bsHead, FAT_bsHeadLen);
  40         memcpy(&bootsect->FAT_bsCode, &sbs->FAT_bsCode, FAT_bsCodeLen);
  41     } else if (fs_type == NTFS) {
  42         struct ntfs_boot_sector *bootsect = bs;
  43         const struct ntfs_boot_sector *sbs =
  44             (const struct ntfs_boot_sector *)boot_sector;
  45
  46         memcpy(&bootsect->NTFS_bsHead, &sbs->NTFS_bsHead, NTFS_bsHeadLen);
  47         memcpy(&bootsect->NTFS_bsCode, &sbs->NTFS_bsCode, NTFS_bsCodeLen);
  48     }
  49 }
  50
  51 static const char *check_fat_bootsect(const void *bs, int *fs_type)
  52 {
  53     int sectorsize;
  54     const struct fat_boot_sector *sectbuf = bs;
  55     long long sectors, fatsectors, dsectors;
  56     long long clusters;
  57     int rootdirents, clustersize;
  58
  59     sectorsize = get_16(&sectbuf->bsBytesPerSec);
  60
  61     clustersize = get_8(&sectbuf->bsSecPerClust);
  62     if (clustersize == 0 || (clustersize & (clustersize - 1)))
  63         return "impossible cluster size on an FAT volume";
  64
  65     sectors = get_16(&sectbuf->bsSectors);
  66     sectors = sectors ? sectors : get_32(&sectbuf->bsHugeSectors);
  67
  68     dsectors = sectors - get_16(&sectbuf->bsResSectors);
  69
  70     fatsectors = get_16(&sectbuf->bsFATsecs);
  71     fatsectors = fatsectors ? fatsectors : get_32(&sectbuf->bs32.FATSz32);
  72     fatsectors *= get_8(&sectbuf->bsFATs);
  73     dsectors -= fatsectors;
  74
  75     rootdirents = get_16(&sectbuf->bsRootDirEnts);
  76     dsectors -= (rootdirents + sectorsize / 32 - 1) / sectorsize;
  77
  78     if (dsectors < 0)
  79         return "negative number of data sectors on an FAT volume";
  80
  81     clusters = dsectors / clustersize;
  82
  83     fatsectors = get_16(&sectbuf->bsFATsecs);
  84     fatsectors = fatsectors ? fatsectors : get_32(&sectbuf->bs32.FATSz32);
  85     fatsectors *= get_8(&sectbuf->bsFATs);
  86
  87     if (!fatsectors)
  88         return "zero FAT sectors";
  89
  90     if (clusters < 0xFFF5) {
  91         /* FAT12 or FAT16 */
  92         if (!get_16(&sectbuf->bsFATsecs))
  93             return "zero FAT sectors (FAT12/16)";
  94
  95         if (get_8(&sectbuf->bs16.BootSignature) == 0x29) {
  96             if (!memcmp(&sectbuf->bs16.FileSysType, "FAT12   ", 8)) {
  97                 if (clusters >= 0xFF5)
  98                     return "more than 4084 clusters but claims FAT12";
  99             } else if (!memcmp(&sectbuf->bs16.FileSysType, "FAT16   ", 8)) {
 100                 if (clusters < 0xFF5)
 101                     return "less than 4084 clusters but claims FAT16";
 102             } else if (!memcmp(&sectbuf->bs16.FileSysType, "FAT32   ", 8)) {
 103                 return "less than 65525 clusters but claims FAT32";
 104             } else if (memcmp(&sectbuf->bs16.FileSysType, "FAT     ", 8)) {
 105                 static char fserr[] = "filesystem type \"????????\" not "
 106                     "supported";
 107                 memcpy(fserr + 17, &sectbuf->bs16.FileSysType, 8);
 108                 return fserr;
 109             }
 110         }
 111     } else if (clusters < 0x0FFFFFF5) {
 112         /*
 113          * FAT32...
 114          *
 115          * Moving the FileSysType and BootSignature was a lovely stroke
 116          * of M$ idiocy...
 117          */
 118         if (get_8(&sectbuf->bs32.BootSignature) != 0x29 ||
 119             memcmp(&sectbuf->bs32.FileSysType, "FAT32   ", 8))
 120             return "missing FAT32 signature";
 121     } else {
 122         return "impossibly large number of clusters on an FAT volume";
 123     }
 124
 125     if (fs_type)
 126         *fs_type = VFAT;
 127
 128     return NULL;
 129 }
 130
 131 static const char *check_ntfs_bootsect(const void *bs, int *fs_type)
 132 {
 133     const struct ntfs_boot_sector *sectbuf = bs;
 134
 135     if (memcmp(&sectbuf->bsOemName, "NTFS    ", 8) &&
 136         memcmp(&sectbuf->bsOemName, "MSWIN4.0", 8) &&
 137         memcmp(&sectbuf->bsOemName, "MSWIN4.1", 8))
 138         return "unknown OEM name but claims NTFS";
 139
 140     if (fs_type)
 141         *fs_type = NTFS;
 142
 143     return NULL;
 144 }
 145
 146 const char *syslinux_check_bootsect(const void *bs, int *fs_type)
 147 {
 148     uint8_t media_sig;
 149     int sectorsize;
 150     const struct fat_boot_sector *sectbuf = bs;
 151     const char *retval;
 152
 153     media_sig = get_8(&sectbuf->bsMedia);
 154     /* Must be 0xF0 or 0xF8-0xFF for FAT/NTFS volumes */
 155     if (media_sig != 0xF0 && media_sig < 0xF8)
 156         return "invalid media signature (not an FAT/NTFS volume?)";
 157
 158     sectorsize = get_16(&sectbuf->bsBytesPerSec);
 159     if (sectorsize == SECTOR_SIZE) ;    /* ok */
 160     else if (sectorsize >= 512 && sectorsize <= 4096 &&
 161              (sectorsize & (sectorsize - 1)) == 0)
 162         return "unsupported sectors size";
 163     else
 164         return "impossible sector size";
 165
 166     if (ntfs_check_zero_fields((struct ntfs_boot_sector *)bs))
 167         retval = check_ntfs_bootsect(bs, fs_type);
 168     else
 169         retval = check_fat_bootsect(bs, fs_type);
 170
 171     return retval;
 172 }