LXR busybox/archival/libunarchive/get_header

   1/* vi: set sw=4 ts=4: */
   2/* Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
   3 *
   4 *  FIXME:
   5 *    In privileged mode if uname and gname map to a uid and gid then use the
   6 *    mapped value instead of the uid/gid values in tar header
   7 *
   8 *  References:
   9 *    GNU tar and star man pages,
  10 *    Opengroup's ustar interchange format,
  11 *      http://www.opengroup.org/onlinepubs/007904975/utilities/pax.html
  12 */
  13
  14#include "libbb.h"
  15#include "unarchive.h"
  16
  17/* NB: _DESTROYS_ str[len] character! */
  18static unsigned long long getOctal(char *str, int len)
  19{
  20        unsigned long long v;
  21        /* NB: leading spaces are allowed. Using strtoull to handle that.
  22         * The downside is that we accept e.g. "-123" too :)
  23         */
  24        str[len] = '\0';
  25        v = strtoull(str, &str, 8);
  26        if (*str && (!ENABLE_FEATURE_TAR_OLDGNU_COMPATIBILITY || *str != ' '))
  27                bb_error_msg_and_die("corrupted octal value in tar header");
  28        return v;
  29}
  30#define GET_OCTAL(a) getOctal((a), sizeof(a))
  31
  32void BUG_tar_header_size(void);
  33char FAST_FUNC get_header_tar(archive_handle_t *archive_handle)
  34{
  35        file_header_t *file_header = archive_handle->file_header;
  36        struct {
  37                /* ustar header, Posix 1003.1 */
  38                char name[100];     /*   0-99 */
  39                char mode[8];       /* 100-107 */
  40                char uid[8];        /* 108-115 */
  41                char gid[8];        /* 116-123 */
  42                char size[12];      /* 124-135 */
  43                char mtime[12];     /* 136-147 */
  44                char chksum[8];     /* 148-155 */
  45                char typeflag;      /* 156-156 */
  46                char linkname[100]; /* 157-256 */
  47                /* POSIX:   "ustar" NUL "00" */
  48                /* GNU tar: "ustar  " NUL */
  49                /* Normally it's defined as magic[6] followed by
  50                 * version[2], but we put them together to simplify code
  51                 */
  52                char magic[8];      /* 257-264 */
  53                char uname[32];     /* 265-296 */
  54                char gname[32];     /* 297-328 */
  55                char devmajor[8];   /* 329-336 */
  56                char devminor[8];   /* 337-344 */
  57                char prefix[155];   /* 345-499 */
  58                char padding[12];   /* 500-512 */
  59        } tar;
  60        char *cp;
  61        int i, sum_u, sum;
  62#if ENABLE_FEATURE_TAR_OLDSUN_COMPATIBILITY
  63        int sum_s;
  64#endif
  65        int parse_names;
  66
  67        /* Our "private data" */
  68#define p_end (*(smallint *)(&archive_handle->ah_priv[0]))
  69#if ENABLE_FEATURE_TAR_GNU_EXTENSIONS
  70#define p_longname (*(char* *)(&archive_handle->ah_priv[1]))
  71#define p_linkname (*(char* *)(&archive_handle->ah_priv[2]))
  72#else
  73#define p_longname 0
  74#define p_linkname 0
  75#endif
  76//      if (!archive_handle->ah_priv_inited) {
  77//              archive_handle->ah_priv_inited = 1;
  78//              p_end = 0;
  79//              USE_FEATURE_TAR_GNU_EXTENSIONS(p_longname = NULL;)
  80//              USE_FEATURE_TAR_GNU_EXTENSIONS(p_linkname = NULL;)
  81//      }
  82
  83        if (sizeof(tar) != 512)
  84                BUG_tar_header_size();
  85
  86#if ENABLE_FEATURE_TAR_GNU_EXTENSIONS
  87 again:
  88#endif
  89        /* Align header */
  90        data_align(archive_handle, 512);
  91
  92 again_after_align:
  93
  94#if ENABLE_DESKTOP
  95        /* to prevent misdetection of bz2 sig */
  96        *(uint32_t*)(&tar) = 0;
  97        i = full_read(archive_handle->src_fd, &tar, 512);
  98        /* If GNU tar sees EOF in above read, it says:
  99         * "tar: A lone zero block at N", where N = kilobyte
 100         * where EOF was met (not EOF block, actual EOF!),
 101         * and exits with EXIT_SUCCESS.
 102         * We will mimic exit(EXIT_SUCCESS), although we will not mimic
 103         * the message and we don't check whether we indeed
 104         * saw zero block directly before this. */
 105        if (i == 0) {
 106                xfunc_error_retval = 0;
 107 short_read:
 108                bb_error_msg_and_die("short read");
 109        }
 110        if (i != 512) {
 111                USE_FEATURE_TAR_AUTODETECT(goto autodetect;)
 112                goto short_read;
 113        }
 114
 115#else
 116        i = 512;
 117        xread(archive_handle->src_fd, &tar, i);
 118#endif
 119        archive_handle->offset += i;
 120
 121        /* If there is no filename its an empty header */
 122        if (tar.name[0] == 0 && tar.prefix[0] == 0) {
 123                if (p_end) {
 124                        /* Second consecutive empty header - end of archive.
 125                         * Read until the end to empty the pipe from gz or bz2
 126                         */
 127                        while (full_read(archive_handle->src_fd, &tar, 512) == 512)
 128                                continue;
 129                        return EXIT_FAILURE;
 130                }
 131                p_end = 1;
 132                return EXIT_SUCCESS;
 133        }
 134        p_end = 0;
 135
 136        /* Check header has valid magic, "ustar" is for the proper tar,
 137         * five NULs are for the old tar format  */
 138        if (strncmp(tar.magic, "ustar", 5) != 0
 139         && (!ENABLE_FEATURE_TAR_OLDGNU_COMPATIBILITY
 140             || memcmp(tar.magic, "\0\0\0\0", 5) != 0)
 141        ) {
 142#if ENABLE_FEATURE_TAR_AUTODETECT
 143                char FAST_FUNC (*get_header_ptr)(archive_handle_t *);
 144
 145 USE_DESKTOP(autodetect:)
 146                /* tar gz/bz autodetect: check for gz/bz2 magic.
 147                 * If we see the magic, and it is the very first block,
 148                 * we can switch to get_header_tar_gz/bz2/lzma().
 149                 * Needs seekable fd. I wish recv(MSG_PEEK) works
 150                 * on any fd... */
 151#if ENABLE_FEATURE_SEAMLESS_GZ
 152                if (tar.name[0] == 0x1f && tar.name[1] == (char)0x8b) { /* gzip */
 153                        get_header_ptr = get_header_tar_gz;
 154                } else
 155#endif
 156#if ENABLE_FEATURE_SEAMLESS_BZ2
 157                if (tar.name[0] == 'B' && tar.name[1] == 'Z'
 158                 && tar.name[2] == 'h' && isdigit(tar.name[3])
 159                ) { /* bzip2 */
 160                        get_header_ptr = get_header_tar_bz2;
 161                } else
 162#endif
 163                        goto err;
 164                /* Two different causes for lseek() != 0:
 165                 * unseekable fd (would like to support that too, but...),
 166                 * or not first block (false positive, it's not .gz/.bz2!) */
 167                if (lseek(archive_handle->src_fd, -i, SEEK_CUR) != 0)
 168                        goto err;
 169                while (get_header_ptr(archive_handle) == EXIT_SUCCESS)
 170                        continue;
 171                return EXIT_FAILURE;
 172 err:
 173#endif /* FEATURE_TAR_AUTODETECT */
 174                bb_error_msg_and_die("invalid tar magic");
 175        }
 176
 177        /* Do checksum on headers.
 178         * POSIX says that checksum is done on unsigned bytes, but
 179         * Sun and HP-UX gets it wrong... more details in
 180         * GNU tar source. */
 181#if ENABLE_FEATURE_TAR_OLDSUN_COMPATIBILITY
 182        sum_s = ' ' * sizeof(tar.chksum);
 183#endif
 184        sum_u = ' ' * sizeof(tar.chksum);
 185        for (i = 0; i < 148; i++) {
 186                sum_u += ((unsigned char*)&tar)[i];
 187#if ENABLE_FEATURE_TAR_OLDSUN_COMPATIBILITY
 188                sum_s += ((signed char*)&tar)[i];
 189#endif
 190        }
 191        for (i = 156; i < 512; i++) {
 192                sum_u += ((unsigned char*)&tar)[i];
 193#if ENABLE_FEATURE_TAR_OLDSUN_COMPATIBILITY
 194                sum_s += ((signed char*)&tar)[i];
 195#endif
 196        }
 197#if ENABLE_FEATURE_TAR_OLDGNU_COMPATIBILITY
 198        sum = strtoul(tar.chksum, &cp, 8);
 199        if ((*cp && *cp != ' ')
 200         || (sum_u != sum USE_FEATURE_TAR_OLDSUN_COMPATIBILITY(&& sum_s != sum))
 201        ) {
 202                bb_error_msg_and_die("invalid tar header checksum");
 203        }
 204#else
 205        /* This field does not need special treatment (getOctal) */
 206        sum = xstrtoul(tar.chksum, 8);
 207        if (sum_u != sum USE_FEATURE_TAR_OLDSUN_COMPATIBILITY(&& sum_s != sum)) {
 208                bb_error_msg_and_die("invalid tar header checksum");
 209        }
 210#endif
 211
 212        /* 0 is reserved for high perf file, treat as normal file */
 213        if (!tar.typeflag) tar.typeflag = '0';
 214        parse_names = (tar.typeflag >= '0' && tar.typeflag <= '7');
 215
 216        /* getOctal trashes subsequent field, therefore we call it
 217         * on fields in reverse order */
 218        if (tar.devmajor[0]) {
 219                char t = tar.prefix[0];
 220                /* we trash prefix[0] here, but we DO need it later! */
 221                unsigned minor = GET_OCTAL(tar.devminor);
 222                unsigned major = GET_OCTAL(tar.devmajor);
 223                file_header->device = makedev(major, minor);
 224                tar.prefix[0] = t;
 225        }
 226        file_header->link_target = NULL;
 227        if (!p_linkname && parse_names && tar.linkname[0]) {
 228                file_header->link_target = xstrndup(tar.linkname, sizeof(tar.linkname));
 229                /* FIXME: what if we have non-link object with link_target? */
 230                /* Will link_target be free()ed? */
 231        }
 232#if ENABLE_FEATURE_TAR_UNAME_GNAME
 233        file_header->uname = tar.uname[0] ? xstrndup(tar.uname, sizeof(tar.uname)) : NULL;
 234        file_header->gname = tar.gname[0] ? xstrndup(tar.gname, sizeof(tar.gname)) : NULL;
 235#endif
 236        file_header->mtime = GET_OCTAL(tar.mtime);
 237        file_header->size = GET_OCTAL(tar.size);
 238        file_header->gid = GET_OCTAL(tar.gid);
 239        file_header->uid = GET_OCTAL(tar.uid);
 240        /* Set bits 0-11 of the files mode */
 241        file_header->mode = 07777 & GET_OCTAL(tar.mode);
 242
 243        file_header->name = NULL;
 244        if (!p_longname && parse_names) {
 245                /* we trash mode[0] here, it's ok */
 246                //tar.name[sizeof(tar.name)] = '\0'; - gcc 4.3.0 would complain
 247                tar.mode[0] = '\0';
 248                if (tar.prefix[0]) {
 249                        /* and padding[0] */
 250                        //tar.prefix[sizeof(tar.prefix)] = '\0'; - gcc 4.3.0 would complain
 251                        tar.padding[0] = '\0';
 252                        file_header->name = concat_path_file(tar.prefix, tar.name);
 253                } else
 254                        file_header->name = xstrdup(tar.name);
 255        }
 256
 257        /* Set bits 12-15 of the files mode */
 258        /* (typeflag was not trashed because chksum does not use getOctal) */
 259        switch (tar.typeflag) {
 260        /* busybox identifies hard links as being regular files with 0 size and a link name */
 261        case '1':
 262                file_header->mode |= S_IFREG;
 263                break;
 264        case '7':
 265        /* case 0: */
 266        case '0':
 267#if ENABLE_FEATURE_TAR_OLDGNU_COMPATIBILITY
 268                if (last_char_is(file_header->name, '/')) {
 269                        goto set_dir;
 270                }
 271#endif
 272                file_header->mode |= S_IFREG;
 273                break;
 274        case '2':
 275                file_header->mode |= S_IFLNK;
 276                /* have seen tarballs with size field containing
 277                 * the size of the link target's name */
 278 size0:
 279                file_header->size = 0;
 280                break;
 281        case '3':
 282                file_header->mode |= S_IFCHR;
 283                goto size0; /* paranoia */
 284        case '4':
 285                file_header->mode |= S_IFBLK;
 286                goto size0;
 287        case '5':
 288 USE_FEATURE_TAR_OLDGNU_COMPATIBILITY(set_dir:)
 289                file_header->mode |= S_IFDIR;
 290                goto size0;
 291        case '6':
 292                file_header->mode |= S_IFIFO;
 293                goto size0;
 294#if ENABLE_FEATURE_TAR_GNU_EXTENSIONS
 295        case 'L':
 296                /* free: paranoia: tar with several consecutive longnames */
 297                free(p_longname);
 298                /* For paranoia reasons we allocate extra NUL char */
 299                p_longname = xzalloc(file_header->size + 1);
 300                /* We read ASCIZ string, including NUL */
 301                xread(archive_handle->src_fd, p_longname, file_header->size);
 302                archive_handle->offset += file_header->size;
 303                /* return get_header_tar(archive_handle); */
 304                /* gcc 4.1.1 didn't optimize it into jump */
 305                /* so we will do it ourself, this also saves stack */
 306                goto again;
 307        case 'K':
 308                free(p_linkname);
 309                p_linkname = xzalloc(file_header->size + 1);
 310                xread(archive_handle->src_fd, p_linkname, file_header->size);
 311                archive_handle->offset += file_header->size;
 312                /* return get_header_tar(archive_handle); */
 313                goto again;
 314        case 'D':       /* GNU dump dir */
 315        case 'M':       /* Continuation of multi volume archive */
 316        case 'N':       /* Old GNU for names > 100 characters */
 317        case 'S':       /* Sparse file */
 318        case 'V':       /* Volume header */
 319#endif
 320        case 'g':       /* pax global header */
 321        case 'x': {     /* pax extended header */
 322                off_t sz;
 323                bb_error_msg("warning: skipping header '%c'", tar.typeflag);
 324                sz = (file_header->size + 511) & ~(off_t)511;
 325                archive_handle->offset += sz;
 326                sz >>= 9; /* sz /= 512 but w/o contortions for signed div */
 327                while (sz--)
 328                        xread(archive_handle->src_fd, &tar, 512);
 329                /* return get_header_tar(archive_handle); */
 330                goto again_after_align;
 331        }
 332        default:
 333                bb_error_msg_and_die("unknown typeflag: 0x%x", tar.typeflag);
 334        }
 335
 336#if ENABLE_FEATURE_TAR_GNU_EXTENSIONS
 337        if (p_longname) {
 338                file_header->name = p_longname;
 339                p_longname = NULL;
 340        }
 341        if (p_linkname) {
 342                file_header->link_target = p_linkname;
 343                p_linkname = NULL;
 344        }
 345#endif
 346        if (strncmp(file_header->name, "/../"+1, 3) == 0
 347         || strstr(file_header->name, "/../")
 348        ) {
 349                bb_error_msg_and_die("name with '..' encountered: '%s'",
 350                                file_header->name);
 351        }
 352
 353        /* Strip trailing '/' in directories */
 354        /* Must be done after mode is set as '/' is used to check if it's a directory */
 355        cp = last_char_is(file_header->name, '/');
 356
 357        if (archive_handle->filter(archive_handle) == EXIT_SUCCESS) {
 358                archive_handle->action_header(/*archive_handle->*/ file_header);
 359                /* Note that we kill the '/' only after action_header() */
 360                /* (like GNU tar 1.15.1: verbose mode outputs "dir/dir/") */
 361                if (cp) *cp = '\0';
 362                archive_handle->ah_flags |= ARCHIVE_EXTRACT_QUIET;
 363                archive_handle->action_data(archive_handle);
 364                llist_add_to(&(archive_handle->passed), file_header->name);
 365        } else {
 366                data_skip(archive_handle);
 367                free(file_header->name);
 368        }
 369        archive_handle->offset += file_header->size;
 370
 371        free(file_header->link_target);
 372        /* Do not free(file_header->name)! (why?) */
 373#if ENABLE_FEATURE_TAR_UNAME_GNAME
 374        free(file_header->uname);
 375        free(file_header->gname);
 376#endif
 377        return EXIT_SUCCESS;
 378}
 379