source: MondoRescue/branches/stable/mindi-busybox/archival/libunarchive/get_header_tar.c@ 1770

/* vi: set sw=4 ts=4: */
/* Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
 *
 *  FIXME:
 *    In privileged mode if uname and gname map to a uid and gid then use the
 *    mapped value instead of the uid/gid values in tar header
 *
 *  References:
 *    GNU tar and star man pages,
 *    Opengroup's ustar interchange format,
 *  http://www.opengroup.org/onlinepubs/007904975/utilities/pax.html
 */

#include "libbb.h"
#include "unarchive.h"

#if ENABLE_FEATURE_TAR_GNU_EXTENSIONS
static char *longname;
static char *linkname;
#else
enum {
    longname = 0,
    linkname = 0,
};
#endif

/* NB: _DESTROYS_ str[len] character! */
static unsigned long long getOctal(char *str, int len)
{
    unsigned long long v;
    /* Actually, tar header allows leading spaces also.
     * Oh well, we will be liberal and skip this...
     * The only downside probably is that we allow "-123" too :)
    if (*str < '0' || *str > '7')
        bb_error_msg_and_die("corrupted octal value in tar header");
    */
    str[len] = '\0';
    v = strtoull(str, &str, 8);
    if (*str && (!ENABLE_FEATURE_TAR_OLDGNU_COMPATIBILITY || *str != ' '))
        bb_error_msg_and_die("corrupted octal value in tar header");
    return v;
}
#define GET_OCTAL(a) getOctal((a), sizeof(a))

void BUG_tar_header_size(void);
char get_header_tar(archive_handle_t *archive_handle)
{
    static smallint end;

    file_header_t *file_header = archive_handle->file_header;
    struct {
        /* ustar header, Posix 1003.1 */
        char name[100];     /*   0-99 */
        char mode[8];       /* 100-107 */
        char uid[8];        /* 108-115 */
        char gid[8];        /* 116-123 */
        char size[12];      /* 124-135 */
        char mtime[12];     /* 136-147 */
        char chksum[8];     /* 148-155 */
        char typeflag;      /* 156-156 */
        char linkname[100]; /* 157-256 */
        char magic[6];      /* 257-262 */
        char version[2];    /* 263-264 */
        char uname[32];     /* 265-296 */
        char gname[32];     /* 297-328 */
        char devmajor[8];   /* 329-336 */
        char devminor[8];   /* 337-344 */
        char prefix[155];   /* 345-499 */
        char padding[12];   /* 500-512 */
    } tar;
    char *cp;
    int i, sum_u, sum;
#if ENABLE_FEATURE_TAR_OLDSUN_COMPATIBILITY
    int sum_s;
#endif
    int parse_names;

    if (sizeof(tar) != 512)
        BUG_tar_header_size();

#if ENABLE_FEATURE_TAR_GNU_EXTENSIONS
 again:
#endif
    /* Align header */
    data_align(archive_handle, 512);

 again_after_align:

    xread(archive_handle->src_fd, &tar, 512);
    archive_handle->offset += 512;

    /* If there is no filename its an empty header */
    if (tar.name[0] == 0) {
        if (end) {
            /* This is the second consecutive empty header! End of archive!
             * Read until the end to empty the pipe from gz or bz2
             */
            while (full_read(archive_handle->src_fd, &tar, 512) == 512)
                /* repeat */;
            return EXIT_FAILURE;
        }
        end = 1;
        return EXIT_SUCCESS;
    }
    end = 0;

    /* Check header has valid magic, "ustar" is for the proper tar
     * 0's are for the old tar format
     */
    if (strncmp(tar.magic, "ustar", 5) != 0) {
#if ENABLE_FEATURE_TAR_OLDGNU_COMPATIBILITY
        if (memcmp(tar.magic, "\0\0\0\0", 5) != 0)
#endif
            bb_error_msg_and_die("invalid tar magic");
    }

    /* Do checksum on headers.
     * POSIX says that checksum is done on unsigned bytes, but
     * Sun and HP-UX gets it wrong... more details in
     * GNU tar source. */
#if ENABLE_FEATURE_TAR_OLDSUN_COMPATIBILITY
    sum_s = ' ' * sizeof(tar.chksum);
#endif
    sum_u = ' ' * sizeof(tar.chksum);
    for (i = 0; i < 148; i++) {
        sum_u += ((unsigned char*)&tar)[i];
#if ENABLE_FEATURE_TAR_OLDSUN_COMPATIBILITY
        sum_s += ((signed char*)&tar)[i];
#endif
    }
    for (i = 156; i < 512; i++) {
        sum_u += ((unsigned char*)&tar)[i];
#if ENABLE_FEATURE_TAR_OLDSUN_COMPATIBILITY
        sum_s += ((signed char*)&tar)[i];
#endif
    }
#if ENABLE_FEATURE_TAR_OLDGNU_COMPATIBILITY
    sum = strtoul(tar.chksum, &cp, 8);
    if ((*cp && *cp != ' ')
     || (sum_u != sum USE_FEATURE_TAR_OLDSUN_COMPATIBILITY(&& sum_s != sum))
    ) {
        bb_error_msg_and_die("invalid tar header checksum");
    }
#else
    /* This field does not need special treatment (getOctal) */
    sum = xstrtoul(tar.chksum, 8);
    if (sum_u != sum USE_FEATURE_TAR_OLDSUN_COMPATIBILITY(&& sum_s != sum)) {
        bb_error_msg_and_die("invalid tar header checksum");
    }
#endif

    /* 0 is reserved for high perf file, treat as normal file */
    if (!tar.typeflag) tar.typeflag = '0';
    parse_names = (tar.typeflag >= '0' && tar.typeflag <= '7');

    /* getOctal trashes subsequent field, therefore we call it
     * on fields in reverse order */
    if (tar.devmajor[0]) {
        unsigned minor = GET_OCTAL(tar.devminor);
        unsigned major = GET_OCTAL(tar.devmajor);
        file_header->device = makedev(major, minor);
    }
    file_header->link_target = NULL;
    if (!linkname && parse_names && tar.linkname[0]) {
        /* we trash magic[0] here, it's ok */
        tar.linkname[sizeof(tar.linkname)] = '\0';
        file_header->link_target = xstrdup(tar.linkname);
        /* FIXME: what if we have non-link object with link_target? */
        /* Will link_target be free()ed? */
    }
    file_header->mtime = GET_OCTAL(tar.mtime);
    file_header->size = GET_OCTAL(tar.size);
    file_header->gid = GET_OCTAL(tar.gid);
    file_header->uid = GET_OCTAL(tar.uid);
    /* Set bits 0-11 of the files mode */
    file_header->mode = 07777 & GET_OCTAL(tar.mode);

    file_header->name = NULL;
    if (!longname && parse_names) {
        /* we trash mode[0] here, it's ok */
        tar.name[sizeof(tar.name)] = '\0';
        if (tar.prefix[0]) {
            /* and padding[0] */
            tar.prefix[sizeof(tar.prefix)] = '\0';
            file_header->name = concat_path_file(tar.prefix, tar.name);
        } else
            file_header->name = xstrdup(tar.name);
    }

    /* Set bits 12-15 of the files mode */
    /* (typeflag was not trashed because chksum does not use getOctal) */
    switch (tar.typeflag) {
    /* busybox identifies hard links as being regular files with 0 size and a link name */
    case '1':
        file_header->mode |= S_IFREG;
        break;
    case '7':
    /* case 0: */
    case '0':
#if ENABLE_FEATURE_TAR_OLDGNU_COMPATIBILITY
        if (last_char_is(file_header->name, '/')) {
            file_header->mode |= S_IFDIR;
        } else
#endif
        file_header->mode |= S_IFREG;
        break;
    case '2':
        file_header->mode |= S_IFLNK;
        break;
    case '3':
        file_header->mode |= S_IFCHR;
        break;
    case '4':
        file_header->mode |= S_IFBLK;
        break;
    case '5':
        file_header->mode |= S_IFDIR;
        break;
    case '6':
        file_header->mode |= S_IFIFO;
        break;
#if ENABLE_FEATURE_TAR_GNU_EXTENSIONS
    case 'L':
        /* free: paranoia: tar with several consecutive longnames */
        free(longname);
        /* For paranoia reasons we allocate extra NUL char */
        longname = xzalloc(file_header->size + 1);
        /* We read ASCIZ string, including NUL */
        xread(archive_handle->src_fd, longname, file_header->size);
        archive_handle->offset += file_header->size;
        /* return get_header_tar(archive_handle); */
        /* gcc 4.1.1 didn't optimize it into jump */
        /* so we will do it ourself, this also saves stack */
        goto again;
    case 'K':
        free(linkname);
        linkname = xzalloc(file_header->size + 1);
        xread(archive_handle->src_fd, linkname, file_header->size);
        archive_handle->offset += file_header->size;
        /* return get_header_tar(archive_handle); */
        goto again;
    case 'D':   /* GNU dump dir */
    case 'M':   /* Continuation of multi volume archive */
    case 'N':   /* Old GNU for names > 100 characters */
    case 'S':   /* Sparse file */
    case 'V':   /* Volume header */
#endif
    case 'g':   /* pax global header */
    case 'x': { /* pax extended header */
        off_t sz;
        bb_error_msg("warning: skipping header '%c'", tar.typeflag);
        sz = (file_header->size + 511) & ~(off_t)511;
        archive_handle->offset += sz;
        sz >>= 9; /* sz /= 512 but w/o contortions for signed div */
        while (sz--)
            xread(archive_handle->src_fd, &tar, 512);
        /* return get_header_tar(archive_handle); */
        goto again_after_align;
    }
    default:
        bb_error_msg_and_die("unknown typeflag: 0x%x", tar.typeflag);
    }

#if ENABLE_FEATURE_TAR_GNU_EXTENSIONS
    if (longname) {
        file_header->name = longname;
        longname = NULL;
    }
    if (linkname) {
        file_header->link_target = linkname;
        linkname = NULL;
    }
#endif
    if (!strncmp(file_header->name, "/../"+1, 3)
     || strstr(file_header->name, "/../")
    ) {
        bb_error_msg_and_die("name with '..' encountered: '%s'",
                file_header->name);
    }

    /* Strip trailing '/' in directories */
    /* Must be done after mode is set as '/' is used to check if it's a directory */
    cp = last_char_is(file_header->name, '/');

    if (archive_handle->filter(archive_handle) == EXIT_SUCCESS) {
        archive_handle->action_header(archive_handle->file_header);
        /* Note that we kill the '/' only after action_header() */
        /* (like GNU tar 1.15.1: verbose mode outputs "dir/dir/") */
        if (cp) *cp = '\0';
        archive_handle->flags |= ARCHIVE_EXTRACT_QUIET;
        archive_handle->action_data(archive_handle);
        llist_add_to(&(archive_handle->passed), file_header->name);
    } else {
        data_skip(archive_handle);
        free(file_header->name);
    }
    archive_handle->offset += file_header->size;

    free(file_header->link_target);
    /* Do not free(file_header->name)! */

    return EXIT_SUCCESS;
}