libbb/get_tar_headers.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 #include <stdlib.h>
  17 #include <string.h>
  18 #include <unistd.h>
  19 #include "libbb.h"
  20
  21 file_headers_t *get_tar_headers(FILE *tar_stream)
  22 {
  23         typedef struct raw_tar_header {
  24         char name[100];               /*   0-99 */
  25         char mode[8];                 /* 100-107 */
  26         char uid[8];                  /* 108-115 */
  27         char gid[8];                  /* 116-123 */
  28         char size[12];                /* 124-135 */
  29         char mtime[12];               /* 136-147 */
  30         char chksum[8];               /* 148-155 */
  31         char typeflag;                /* 156-156 */
  32         char linkname[100];           /* 157-256 */
  33         char magic[6];                /* 257-262 */
  34         char version[2];              /* 263-264 */
  35         char uname[32];               /* 265-296 */
  36         char gname[32];               /* 297-328 */
  37         char devmajor[8];             /* 329-336 */
  38         char devminor[8];             /* 337-344 */
  39         char prefix[155];             /* 345-499 */
  40         char padding[12];             /* 500-512 */
  41         } raw_tar_header_t;
  42
  43         raw_tar_header_t raw_tar_header;
  44         unsigned char *temp = (unsigned char *) &raw_tar_header;
  45         file_headers_t *tar_headers_list = (file_headers_t *) calloc(1, sizeof(file_headers_t));
  46         file_headers_t *tar_entry;
  47         long i;
  48         long next_header_offset = 0;
  49         long current_offset = 0;
  50
  51         while (fread((char *) &raw_tar_header, 1, 512, tar_stream) == 512) {
  52                 long sum = 0;
  53                 current_offset += 512;
  54
  55                 /* Check header has valid magic, unfortunately some tar files
  56                  * have empty (0'ed) tar entries at the end, which will
  57                  * cause this to fail, so fail silently for now
  58                  */
  59                 if (strncmp(raw_tar_header.magic, "ustar", 5) != 0) {
  60 //                      error_msg("invalid magic, [%s]\n", raw_tar_header.magic);
  61                         break;
  62                 }
  63
  64                 /* Do checksum on headers */
  65         for (i =  0; i < 148 ; i++) {
  66                         sum += temp[i];
  67                 }
  68         sum += ' ' * 8;
  69                 for (i =  156; i < 512 ; i++) {
  70                         sum += temp[i];
  71                 }
  72         if (sum != strtol(raw_tar_header.chksum, NULL, 8)) {
  73                         error_msg("Invalid tar header checksum");
  74                         break;
  75                 }
  76
  77                 /* convert to type'ed variables */
  78                 tar_entry = xcalloc(1, sizeof(file_headers_t));
  79                 tar_entry->name = xstrdup(raw_tar_header.name);
  80
  81                 tar_entry->offset = (off_t) current_offset;
  82                 parse_mode(raw_tar_header.mode, &tar_entry->mode);
  83                 tar_entry->uid   = strtol(raw_tar_header.uid, NULL, 8);
  84                 tar_entry->gid   = strtol(raw_tar_header.gid, NULL, 8);
  85                 tar_entry->size  = strtol(raw_tar_header.size, NULL, 8);
  86                 tar_entry->mtime = strtol(raw_tar_header.mtime, NULL, 8);
  87                 tar_entry->link_name  = xstrdup(raw_tar_header.linkname);
  88 //              tar_entry->devmajor  = strtol(rawHeader->devmajor, NULL, 8);
  89 //              tar_entry->devminor  = strtol(rawHeader->devminor, NULL, 8);
  90
  91                 tar_headers_list = append_archive_list(tar_headers_list, tar_entry);
  92
  93                 /* start of next header is at */
  94                 next_header_offset = current_offset + tar_entry->size;
  95
  96                 if (tar_entry->size % 512 != 0) {
  97                         next_header_offset += (512 - tar_entry->size % 512);
  98                 }
  99                 /*
 100                  * Seek to start of next block, cant use fseek as unzip() does support it
 101                  */
 102                 while (current_offset < next_header_offset) {
 103                         if (fgetc(tar_stream) == EOF) {
 104                                 break;
 105                         }
 106                         current_offset++;
 107                 }
 108         }
 109         return(tar_headers_list);
 110 }
 111