/* 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"

/*
 * GNU tar uses "base-256 encoding" for very large numbers (>8 billion).
 * Encoding is binary, with highest bit always set as a marker
 * and sign in next-highest bit:
 * 80 00 .. 00 - zero
 * bf ff .. ff - largest positive number
 * ff ff .. ff - minus 1
 * c0 00 .. 00 - smallest negative number
 *
 * We expect it only in size field, where negative numbers don't make sense.
 */
static off_t getBase256_len12(const char *str)
{
        off_t value;
        int len;

        /* if (*str & 0x40) error; - caller prevents this */

        if (sizeof(off_t) >= 12) {
                /* Probably 128-bit (16 byte) off_t. Can be optimized. */
                len = 12;
                value = *str++ & 0x3f;
                while (--len)
                        value = (value << 8) + (unsigned char) *str++;
                return value;
        }

#ifdef CHECK_FOR_OVERFLOW
        /* Can be optimized to eat 32-bit chunks */
        char c = *str++ & 0x3f;
        len = 12;
        while (1) {
                if (c)
                        bb_error_msg_and_die("overflow in base-256 encoded file size");
                if (--len == sizeof(off_t))
                        break;
                c = *str++;
        }
#else
        str += (12 - sizeof(off_t));
#endif

/* Now str points to sizeof(off_t) least significant bytes.
 *
 * Example of tar file with 8914993153 (0x213600001) byte file.
 * Field starts at offset 7c:
 * 00070  30 30 30 00 30 30 30 30  30 30 30 00 80 00 00 00  |000.0000000.....|
 * 00080  00 00 00 02 13 60 00 01  31 31 31 32 30 33 33 36  |.....`..11120336|
 *
 * str is at offset 80 or 84 now (64-bit or 32-bit off_t).
 * We (ab)use the fact that value happens to be aligned,
 * and fetch it in one go:
 */
        if (sizeof(off_t) == 8) {
                value = *(off_t*)str;
                value = SWAP_BE64(value);
        } else if (sizeof(off_t) == 4) {
                value = *(off_t*)str;
                value = SWAP_BE32(value);
        } else {
                value = 0;
                len = sizeof(off_t);
                while (--len)
                        value = (value << 8) + (unsigned char) *str++;
        }
        return value;
}

/* NB: _DESTROYS_ str[len] character! */
static unsigned long long getOctal(char *str, int len)
{
        unsigned long long v;
        /* NB: leading spaces are allowed. Using strtoull to handle that.
         * The downside is that we accept e.g. "-123" too :(
         */
        str[len] = '\0';
        v = strtoull(str, &str, 8);
        /* std: "Each numeric field is terminated by one or more
         * <space> or NUL characters". We must support ' '! */
        if (*str != '\0' && *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 FAST_FUNC get_header_tar(archive_handle_t *archive_handle)
{
        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 */
                /* POSIX:   "ustar" NUL "00" */
                /* GNU tar: "ustar  " NUL */
                /* Normally it's defined as magic[6] followed by
                 * version[2], but we put them together to simplify code
                 */
                char magic[8];      /* 257-264 */
                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;

        /* Our "private data" */
#if ENABLE_FEATURE_TAR_GNU_EXTENSIONS
# define p_longname (archive_handle->tar__longname)
# define p_linkname (archive_handle->tar__linkname)
#else
# define p_longname 0
# define p_linkname 0
#endif

        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:

#if ENABLE_DESKTOP || ENABLE_FEATURE_TAR_AUTODETECT
        /* to prevent misdetection of bz2 sig */
        *(uint32_t*)(&tar) = 0;
        i = full_read(archive_handle->src_fd, &tar, 512);
        /* If GNU tar sees EOF in above read, it says:
         * "tar: A lone zero block at N", where N = kilobyte
         * where EOF was met (not EOF block, actual EOF!),
         * and exits with EXIT_SUCCESS.
         * We will mimic exit(EXIT_SUCCESS), although we will not mimic
         * the message and we don't check whether we indeed
         * saw zero block directly before this. */
        if (i == 0) {
                xfunc_error_retval = 0;
 short_read:
                bb_error_msg_and_die("short read");
        }
        if (i != 512) {
                IF_FEATURE_TAR_AUTODETECT(goto autodetect;)
                goto short_read;
        }

#else
        i = 512;
        xread(archive_handle->src_fd, &tar, i);
#endif
        archive_handle->offset += i;

        /* If there is no filename its an empty header */
        if (tar.name[0] == 0 && tar.prefix[0] == 0) {
                if (archive_handle->tar__end) {
                        /* 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)
                                continue;
                        return EXIT_FAILURE;
                }
                archive_handle->tar__end = 1;
                return EXIT_SUCCESS;
        }
        archive_handle->tar__end = 0;

        /* Check header has valid magic, "ustar" is for the proper tar,
         * five NULs are for the old tar format  */
        if (strncmp(tar.magic, "ustar", 5) != 0
         && (!ENABLE_FEATURE_TAR_OLDGNU_COMPATIBILITY
             || memcmp(tar.magic, "\0\0\0\0", 5) != 0)
        ) {
#if ENABLE_FEATURE_TAR_AUTODETECT
                char FAST_FUNC (*get_header_ptr)(archive_handle_t *);

 autodetect:
                /* tar gz/bz autodetect: check for gz/bz2 magic.
                 * If we see the magic, and it is the very first block,
                 * we can switch to get_header_tar_gz/bz2/lzma().
                 * Needs seekable fd. I wish recv(MSG_PEEK) works
                 * on any fd... */
#if ENABLE_FEATURE_SEAMLESS_GZ
                if (tar.name[0] == 0x1f && tar.name[1] == (char)0x8b) { /* gzip */
                        get_header_ptr = get_header_tar_gz;
                } else
#endif
#if ENABLE_FEATURE_SEAMLESS_BZ2
                if (tar.name[0] == 'B' && tar.name[1] == 'Z'
                 && tar.name[2] == 'h' && isdigit(tar.name[3])
                ) { /* bzip2 */
                        get_header_ptr = get_header_tar_bz2;
                } else
#endif
                        goto err;
                /* Two different causes for lseek() != 0:
                 * unseekable fd (would like to support that too, but...),
                 * or not first block (false positive, it's not .gz/.bz2!) */
                if (lseek(archive_handle->src_fd, -i, SEEK_CUR) != 0)
                        goto err;
                while (get_header_ptr(archive_handle) == EXIT_SUCCESS)
                        continue;
                return EXIT_FAILURE;
 err:
#endif /* FEATURE_TAR_AUTODETECT */
                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
        }
        /* This field does not need special treatment (getOctal) */
        {
                char *endp; /* gcc likes temp var for &endp */
                sum = strtoul(tar.chksum, &endp, 8);
                if ((*endp != '\0' && *endp != ' ')
                 || (sum_u != sum IF_FEATURE_TAR_OLDSUN_COMPATIBILITY(&& sum_s != sum))
                ) {
                        bb_error_msg_and_die("invalid tar header checksum");
                }
        }
        /* don't use xstrtoul, tar.chksum may have leading spaces */
        sum = strtoul(tar.chksum, NULL, 8);
        if (sum_u != sum IF_FEATURE_TAR_OLDSUN_COMPATIBILITY(&& sum_s != sum)) {
                bb_error_msg_and_die("invalid tar header checksum");
        }

        /* 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]) {
                char t = tar.prefix[0];
                /* we trash prefix[0] here, but we DO need it later! */
                unsigned minor = GET_OCTAL(tar.devminor);
                unsigned major = GET_OCTAL(tar.devmajor);
                file_header->device = makedev(major, minor);
                tar.prefix[0] = t;
        }
        file_header->link_target = NULL;
        if (!p_linkname && parse_names && tar.linkname[0]) {
                file_header->link_target = xstrndup(tar.linkname, sizeof(tar.linkname));
                /* FIXME: what if we have non-link object with link_target? */
                /* Will link_target be free()ed? */
        }
#if ENABLE_FEATURE_TAR_UNAME_GNAME
        file_header->tar__uname = tar.uname[0] ? xstrndup(tar.uname, sizeof(tar.uname)) : NULL;
        file_header->tar__gname = tar.gname[0] ? xstrndup(tar.gname, sizeof(tar.gname)) : NULL;
#endif
        /* mtime: rudimentally handle GNU tar's "base256 encoding"
         * People report tarballs with NEGATIVE unix times encoded that way */
        file_header->mtime = (tar.mtime[0] & 0x80) /* base256? */
                        ? 0 /* bogus */
                        : GET_OCTAL(tar.mtime);
        /* size: handle GNU tar's "base256 encoding" */
        file_header->size = (tar.size[0] & 0xc0) == 0x80 /* positive base256? */
                        ? getBase256_len12(tar.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 (!p_longname && parse_names) {
                /* we trash mode[0] here, it's ok */
                //tar.name[sizeof(tar.name)] = '\0'; - gcc 4.3.0 would complain
                tar.mode[0] = '\0';
                if (tar.prefix[0]) {
                        /* and padding[0] */
                        //tar.prefix[sizeof(tar.prefix)] = '\0'; - gcc 4.3.0 would complain
                        tar.padding[0] = '\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, '/')) {
                        goto set_dir;
                }
#endif
                file_header->mode |= S_IFREG;
                break;
        case '2':
                file_header->mode |= S_IFLNK;
                /* have seen tarballs with size field containing
                 * the size of the link target's name */
 size0:
                file_header->size = 0;
                break;
        case '3':
                file_header->mode |= S_IFCHR;
                goto size0; /* paranoia */
        case '4':
                file_header->mode |= S_IFBLK;
                goto size0;
        case '5':
 IF_FEATURE_TAR_OLDGNU_COMPATIBILITY(set_dir:)
                file_header->mode |= S_IFDIR;
                goto size0;
        case '6':
                file_header->mode |= S_IFIFO;
                goto size0;
#if ENABLE_FEATURE_TAR_GNU_EXTENSIONS
        case 'L':
                /* free: paranoia: tar with several consecutive longnames */
                free(p_longname);
                /* For paranoia reasons we allocate extra NUL char */
                p_longname = xzalloc(file_header->size + 1);
                /* We read ASCIZ string, including NUL */
                xread(archive_handle->src_fd, p_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(p_linkname);
                p_linkname = xzalloc(file_header->size + 1);
                xread(archive_handle->src_fd, p_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 (p_longname) {
                file_header->name = p_longname;
                p_longname = NULL;
        }
        if (p_linkname) {
                file_header->link_target = p_linkname;
                p_linkname = NULL;
        }
#endif
        if (strncmp(file_header->name, "/../"+1, 3) == 0
         || 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->ah_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)! (why?) */
#if ENABLE_FEATURE_TAR_UNAME_GNAME
        free(file_header->tar__uname);
        free(file_header->tar__gname);
#endif
        return EXIT_SUCCESS;
}