archival/libunarchive/get_header_tar.c

   1 /*
   2  *  This program is free software; you can redistribute it and/or modify
   3  *  it under the terms of the GNU General Public License as published by
   4  *  the Free Software Foundation; either version 2 of the License, or
   5  *  (at your option) any later version.
   6  *
   7  *  This program is distributed in the hope that it will be useful,
   8  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
   9  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  10  *  GNU Library General Public License for more details.
  11  *
  12  *  You should have received a copy of the GNU General Public License
  13  *  along with this program; if not, write to the Free Software
  14  *  Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  15  */
  16
  17 #include <stdio.h>
  18 #include <stdlib.h>
  19 #include <string.h>
  20 #include "unarchive.h"
  21 #include "libbb.h"
  22
  23 file_header_t *get_header_tar(FILE *tar_stream)
  24 {
  25         union {
  26                 unsigned char raw[512];
  27                 struct {
  28                         char name[100];         /*   0-99 */
  29                         char mode[8];           /* 100-107 */
  30                         char uid[8];            /* 108-115 */
  31                         char gid[8];            /* 116-123 */
  32                         char size[12];          /* 124-135 */
  33                         char mtime[12];         /* 136-147 */
  34                         char chksum[8];         /* 148-155 */
  35                         char typeflag;          /* 156-156 */
  36                         char linkname[100];     /* 157-256 */
  37                         char magic[6];          /* 257-262 */
  38                         char version[2];        /* 263-264 */
  39                         char uname[32];         /* 265-296 */
  40                         char gname[32];         /* 297-328 */
  41                         char devmajor[8];       /* 329-336 */
  42                         char devminor[8];       /* 337-344 */
  43                         char prefix[155];       /* 345-499 */
  44                         char padding[12];       /* 500-512 */
  45                 } formated;
  46         } tar;
  47         file_header_t *tar_entry = NULL;
  48         long sum = 0;
  49         long i;
  50
  51         if (archive_offset % 512 != 0) {
  52                 seek_sub_file(tar_stream, 512 - (archive_offset % 512));
  53         }
  54
  55         if (fread(tar.raw, 1, 512, tar_stream) != 512) {
  56                 /* Unfortunatly its common for tar files to have all sorts of
  57                  * trailing garbage, fail silently */
  58 //              error_msg("Couldnt read header");
  59                 return(NULL);
  60         }
  61         archive_offset += 512;
  62
  63         /* Check header has valid magic, "ustar" is for the proper tar
  64          * 0's are for the old tar format
  65          */
  66         if (strncmp(tar.formated.magic, "ustar", 5) != 0) {
  67 #ifdef CONFIG_FEATURE_TAR_OLD_FORMAT
  68                 if (strncmp(tar.formated.magic, "\0\0\0\0\0", 5) != 0)
  69 #endif
  70                         return(NULL);
  71         }
  72
  73         /* If there is no filename its an empty header, skip it */
  74         if (tar.formated.name[0] == 0) {
  75                 return(NULL);
  76         }
  77
  78         /* Do checksum on headers */
  79         for (i =  0; i < 148 ; i++) {
  80                 sum += tar.raw[i];
  81         }
  82         sum += ' ' * 8;
  83         for (i =  156; i < 512 ; i++) {
  84                 sum += tar.raw[i];
  85         }
  86         if (sum != strtol(tar.formated.chksum, NULL, 8)) {
  87                 error_msg("Invalid tar header checksum");
  88                 return(NULL);
  89         }
  90
  91         /* convert to type'ed variables */
  92         tar_entry = xcalloc(1, sizeof(file_header_t));
  93         if (tar.formated.prefix[0] == 0) {
  94                 tar_entry->name = xstrdup(tar.formated.name);
  95         } else {
  96                 tar_entry->name = concat_path_file(tar.formated.prefix, tar.formated.name);
  97         }
  98
  99         tar_entry->mode = strtol(tar.formated.mode, NULL, 8);
 100 #ifdef CONFIG_FEATURE_TAR_OLD_FORMAT
 101         switch (tar.formated.typeflag) {
 102                 case 0:
 103                         tar_entry->mode |= S_IFREG;
 104                         break;
 105                 case 1:
 106                         error_msg("internal hard link not handled\n");
 107                         break;
 108                 case 2:
 109                         tar_entry->mode |= S_IFLNK;
 110                         break;
 111                 case 3:
 112                         tar_entry->mode |= S_IFCHR;
 113                         break;
 114                 case 4:
 115                         tar_entry->mode |= S_IFBLK;
 116                         break;
 117                 case 5:
 118                         tar_entry->mode |= S_IFDIR;
 119                         break;
 120                 case 6:
 121                         tar_entry->mode |= S_IFIFO;
 122                         break;
 123         }
 124 #endif
 125         tar_entry->uid   = strtol(tar.formated.uid, NULL, 8);
 126         tar_entry->gid   = strtol(tar.formated.gid, NULL, 8);
 127         tar_entry->size  = strtol(tar.formated.size, NULL, 8);
 128         tar_entry->mtime = strtol(tar.formated.mtime, NULL, 8);
 129         tar_entry->link_name  = strlen(tar.formated.linkname) ?
 130             xstrdup(tar.formated.linkname) : NULL;
 131         tar_entry->device = (strtol(tar.formated.devmajor, NULL, 8) << 8) +
 132                 strtol(tar.formated.devminor, NULL, 8);
 133
 134         return(tar_entry);
 135 }
 136