release/src/router/busybox/archival/libarchive/get_header_ar.c

   1 /* vi: set sw=4 ts=4: */
   2 /* Copyright 2001 Glenn McGrath.
   3  *
   4  * Licensed under GPLv2 or later, see file LICENSE in this source tree.
   5  */
   6
   7 #include "libbb.h"
   8 #include "bb_archive.h"
   9 #include "ar.h"
  10
  11 /* WARNING: Clobbers str[len], so fields must be read in reverse order! */
  12 static unsigned read_num(char *str, int base, int len)
  13 {
  14         int err;
  15
  16         /* ar fields are fixed length text strings (padded with spaces).
  17          * Ensure bb_strtou doesn't read past the field in case the full
  18          * width is used. */
  19         str[len] = 0;
  20
  21         /* This code works because
  22          * on misformatted numbers bb_strtou returns all-ones */
  23         err = bb_strtou(str, NULL, base);
  24         if (err == -1)
  25                 bb_error_msg_and_die("invalid ar header");
  26         return err;
  27 }
  28
  29 char FAST_FUNC get_header_ar(archive_handle_t *archive_handle)
  30 {
  31         file_header_t *typed = archive_handle->file_header;
  32         unsigned size;
  33         union {
  34                 char raw[60];
  35                 struct ar_header formatted;
  36         } ar;
  37 #if ENABLE_FEATURE_AR_LONG_FILENAMES
  38         static char *ar_long_names;
  39         static unsigned ar_long_name_size;
  40 #endif
  41
  42         /* dont use xread as we want to handle the error ourself */
  43         if (read(archive_handle->src_fd, ar.raw, 60) != 60) {
  44                 /* End Of File */
  45                 return EXIT_FAILURE;
  46         }
  47
  48         /* ar header starts on an even byte (2 byte aligned)
  49          * '\n' is used for padding
  50          */
  51         if (ar.raw[0] == '\n') {
  52                 /* fix up the header, we started reading 1 byte too early */
  53                 memmove(ar.raw, &ar.raw[1], 59);
  54                 ar.raw[59] = xread_char(archive_handle->src_fd);
  55                 archive_handle->offset++;
  56         }
  57         archive_handle->offset += 60;
  58
  59         if (ar.formatted.magic[0] != '`' || ar.formatted.magic[1] != '\n')
  60                 bb_error_msg_and_die("invalid ar header");
  61
  62         /*
  63          * Note that the fields MUST be read in reverse order as
  64          * read_num() clobbers the next byte after the field!
  65          * Order is: name, date, uid, gid, mode, size, magic.
  66          */
  67         typed->size = size = read_num(ar.formatted.size, 10,
  68                                       sizeof(ar.formatted.size));
  69
  70         /* special filenames have '/' as the first character */
  71         if (ar.formatted.name[0] == '/') {
  72                 if (ar.formatted.name[1] == ' ') {
  73                         /* This is the index of symbols in the file for compilers */
  74                         data_skip(archive_handle);
  75                         archive_handle->offset += size;
  76                         return get_header_ar(archive_handle); /* Return next header */
  77                 }
  78 #if ENABLE_FEATURE_AR_LONG_FILENAMES
  79                 if (ar.formatted.name[1] == '/') {
  80                         /* If the second char is a '/' then this entries data section
  81                          * stores long filename for multiple entries, they are stored
  82                          * in static variable long_names for use in future entries
  83                          */
  84                         ar_long_name_size = size;
  85                         free(ar_long_names);
  86                         ar_long_names = xmalloc(size);
  87                         xread(archive_handle->src_fd, ar_long_names, size);
  88                         archive_handle->offset += size;
  89                         /* Return next header */
  90                         return get_header_ar(archive_handle);
  91                 }
  92 #else
  93                 bb_error_msg_and_die("long filenames not supported");
  94 #endif
  95         }
  96         /* Only size is always present, the rest may be missing in
  97          * long filename pseudo file. Thus we decode the rest
  98          * after dealing with long filename pseudo file.
  99          */
 100         typed->mode = read_num(ar.formatted.mode, 8, sizeof(ar.formatted.mode));
 101         typed->gid = read_num(ar.formatted.gid, 10, sizeof(ar.formatted.gid));
 102         typed->uid = read_num(ar.formatted.uid, 10, sizeof(ar.formatted.uid));
 103         typed->mtime = read_num(ar.formatted.date, 10, sizeof(ar.formatted.date));
 104
 105 #if ENABLE_FEATURE_AR_LONG_FILENAMES
 106         if (ar.formatted.name[0] == '/') {
 107                 unsigned long_offset;
 108
 109                 /* The number after the '/' indicates the offset in the ar data section
 110                  * (saved in ar_long_names) that conatains the real filename */
 111                 long_offset = read_num(&ar.formatted.name[1], 10,
 112                                        sizeof(ar.formatted.name) - 1);
 113                 if (long_offset >= ar_long_name_size) {
 114                         bb_error_msg_and_die("can't resolve long filename");
 115                 }
 116                 typed->name = xstrdup(ar_long_names + long_offset);
 117         } else
 118 #endif
 119         {
 120                 /* short filenames */
 121                 typed->name = xstrndup(ar.formatted.name, 16);
 122         }
 123
 124         typed->name[strcspn(typed->name, " /")] = '\0';
 125
 126         if (archive_handle->filter(archive_handle) == EXIT_SUCCESS) {
 127                 archive_handle->action_header(typed);
 128 #if ENABLE_DPKG || ENABLE_DPKG_DEB
 129                 if (archive_handle->dpkg__sub_archive) {
 130                         while (archive_handle->dpkg__action_data_subarchive(archive_handle->dpkg__sub_archive) == EXIT_SUCCESS)
 131                                 continue;
 132                 } else
 133 #endif
 134                         archive_handle->action_data(archive_handle);
 135         } else {
 136                 data_skip(archive_handle);
 137         }
 138
 139         archive_handle->offset += typed->size;
 140         /* Set the file pointer to the correct spot, we may have been reading a compressed file */
 141         lseek(archive_handle->src_fd, archive_handle->offset, SEEK_SET);
 142
 143         return EXIT_SUCCESS;
 144 }