LXR busybox/archival/libarchive/get_header

   1/* vi: set sw=4 ts=4: */
   2/*
   3 * Copyright 2001 Glenn McGrath.
   4 *
   5 * Licensed under GPLv2 or later, see file LICENSE in this source tree.
   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! */
  12static 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
  29char 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
  38        /* dont use xread as we want to handle the error ourself */
  39        if (read(archive_handle->src_fd, ar.raw, 60) != 60) {
  40                /* End Of File */
  41                return EXIT_FAILURE;
  42        }
  43
  44        /* ar header starts on an even byte (2 byte aligned)
  45         * '\n' is used for padding
  46         */
  47        if (ar.raw[0] == '\n') {
  48                /* fix up the header, we started reading 1 byte too early */
  49                memmove(ar.raw, &ar.raw[1], 59);
  50                ar.raw[59] = xread_char(archive_handle->src_fd);
  51                archive_handle->offset++;
  52        }
  53        archive_handle->offset += 60;
  54
  55        if (ar.formatted.magic[0] != '`' || ar.formatted.magic[1] != '\n')
  56                bb_error_msg_and_die("invalid ar header");
  57
  58        /*
  59         * Note that the fields MUST be read in reverse order as
  60         * read_num() clobbers the next byte after the field!
  61         * Order is: name, date, uid, gid, mode, size, magic.
  62         */
  63        typed->size = size = read_num(ar.formatted.size, 10,
  64                                      sizeof(ar.formatted.size));
  65
  66        /* special filenames have '/' as the first character */
  67        if (ar.formatted.name[0] == '/') {
  68                if (ar.formatted.name[1] == ' ') {
  69                        /* This is the index of symbols in the file for compilers */
  70                        data_skip(archive_handle);
  71                        archive_handle->offset += size;
  72                        return get_header_ar(archive_handle); /* Return next header */
  73                }
  74#if ENABLE_FEATURE_AR_LONG_FILENAMES
  75                if (ar.formatted.name[1] == '/') {
  76                        /* If the second char is a '/' then this entries data section
  77                         * stores long filename for multiple entries, they are stored
  78                         * in static variable long_names for use in future entries
  79                         */
  80                        archive_handle->ar__long_name_size = size;
  81                        free(archive_handle->ar__long_names);
  82                        archive_handle->ar__long_names = xzalloc(size + 1);
  83                        xread(archive_handle->src_fd, archive_handle->ar__long_names, size);
  84                        archive_handle->offset += size;
  85                        /* Return next header */
  86                        return get_header_ar(archive_handle);
  87                }
  88#else
  89                bb_error_msg_and_die("long filenames not supported");
  90#endif
  91        }
  92        /* Only size is always present, the rest may be missing in
  93         * long filename pseudo file. Thus we decode the rest
  94         * after dealing with long filename pseudo file.
  95         */
  96        typed->mode = read_num(ar.formatted.mode, 8, sizeof(ar.formatted.mode));
  97        typed->gid = read_num(ar.formatted.gid, 10, sizeof(ar.formatted.gid));
  98        typed->uid = read_num(ar.formatted.uid, 10, sizeof(ar.formatted.uid));
  99        typed->mtime = read_num(ar.formatted.date, 10, sizeof(ar.formatted.date));
 100
 101#if ENABLE_FEATURE_AR_LONG_FILENAMES
 102        if (ar.formatted.name[0] == '/') {
 103                unsigned long_offset;
 104
 105                /* The number after the '/' indicates the offset in the ar data section
 106                 * (saved in ar__long_names) that contains the real filename */
 107                long_offset = read_num(&ar.formatted.name[1], 10,
 108                                       sizeof(ar.formatted.name) - 1);
 109                if (long_offset >= archive_handle->ar__long_name_size) {
 110                        bb_error_msg_and_die("can't resolve long filename");
 111                }
 112                typed->name = xstrdup(archive_handle->ar__long_names + long_offset);
 113        } else
 114#endif
 115        {
 116                /* short filenames */
 117                typed->name = xstrndup(ar.formatted.name, 16);
 118        }
 119
 120        typed->name[strcspn(typed->name, " /")] = '\0';
 121
 122        if (archive_handle->filter(archive_handle) == EXIT_SUCCESS) {
 123                archive_handle->action_header(typed);
 124#if ENABLE_DPKG || ENABLE_DPKG_DEB
 125                if (archive_handle->dpkg__sub_archive) {
 126                        struct archive_handle_t *sa = archive_handle->dpkg__sub_archive;
 127                        while (archive_handle->dpkg__action_data_subarchive(sa) == EXIT_SUCCESS)
 128                                continue;
 129                        create_links_from_list(sa->link_placeholders);
 130                } else
 131#endif
 132                        archive_handle->action_data(archive_handle);
 133        } else {
 134                data_skip(archive_handle);
 135        }
 136
 137        archive_handle->offset += typed->size;
 138        /* Set the file pointer to the correct spot, we may have been reading a compressed file */
 139        lseek(archive_handle->src_fd, archive_handle->offset, SEEK_SET);
 140
 141        return EXIT_SUCCESS;
 142}
 143