Code: read_Header(struct archive_read *a, struct _7z_header_info *h,
    int check_header_id)
{
	struct _7zip *zip = (struct _7zip *)a->format->data;
	const unsigned char *p;
	struct _7z_folder *folders;
	struct _7z_stream_info *si = &(zip->si);
	struct _7zip_entry *entries;
	uint32_t folderIndex, indexInFolder;
	unsigned i;
	int eindex, empty_streams, sindex;

	if (check_header_id) {
		/*
		 * Read Header.
		 */
		if ((p = header_bytes(a, 1)) == NULL)
			return (-1);
		if (*p != kHeader)
			return (-1);
	}

	/*
	 * Read ArchiveProperties.
	 */
	if ((p = header_bytes(a, 1)) == NULL)
		return (-1);
	if (*p == kArchiveProperties) {
		for (;;) {
			uint64_t size;
			if ((p = header_bytes(a, 1)) == NULL)
				return (-1);
			if (*p == 0)
				break;
			if (parse_7zip_uint64(a, &size) < 0)
				return (-1);
		}
		if ((p = header_bytes(a, 1)) == NULL)
			return (-1);
	}

	/*
	 * Read MainStreamsInfo.
	 */
	if (*p == kMainStreamsInfo) {
		if (read_StreamsInfo(a, &(zip->si)) < 0)
			return (-1);
		if ((p = header_bytes(a, 1)) == NULL)
			return (-1);
	}
	if (*p == kEnd)
		return (0);

	/*
	 * Read FilesInfo.
	 */
	if (*p != kFilesInfo)
		return (-1);

	if (parse_7zip_uint64(a, &(zip->numFiles)) < 0)
		return (-1);
	if (UMAX_ENTRY < zip->numFiles)
		return (-1);

	zip->entries = calloc((size_t)zip->numFiles, sizeof(*zip->entries));
	if (zip->entries == NULL)
		return (-1);
	entries = zip->entries;

	empty_streams = 0;
	for (;;) {
		int type;
		uint64_t size;
		size_t ll;

		if ((p = header_bytes(a, 1)) == NULL)
			return (-1);
		type = *p;
		if (type == kEnd)
			break;

		if (parse_7zip_uint64(a, &size) < 0)
			return (-1);
		if (zip->header_bytes_remaining < size)
			return (-1);
		ll = (size_t)size;
 
 		switch (type) {
 		case kEmptyStream:
 			h->emptyStreamBools = calloc((size_t)zip->numFiles,
 			    sizeof(*h->emptyStreamBools));
 			if (h->emptyStreamBools == NULL)
				return (-1);
			if (read_Bools(
			    a, h->emptyStreamBools, (size_t)zip->numFiles) < 0)
				return (-1);
			empty_streams = 0;
			for (i = 0; i < zip->numFiles; i++) {
				if (h->emptyStreamBools[i])
					empty_streams++;
			}
			break;
		case kEmptyFile:
			if (empty_streams <= 0) {
				/* Unexcepted sequence. Skip this. */
				if (header_bytes(a, ll) == NULL)
 					return (-1);
 				break;
 			}
 			h->emptyFileBools = calloc(empty_streams,
 			    sizeof(*h->emptyFileBools));
 			if (h->emptyFileBools == NULL)
				return (-1);
			if (read_Bools(a, h->emptyFileBools, empty_streams) < 0)
				return (-1);
			break;
		case kAnti:
			if (empty_streams <= 0) {
				/* Unexcepted sequence. Skip this. */
				if (header_bytes(a, ll) == NULL)
 					return (-1);
 				break;
 			}
 			h->antiBools = calloc(empty_streams,
 			    sizeof(*h->antiBools));
 			if (h->antiBools == NULL)
				return (-1);
			if (read_Bools(a, h->antiBools, empty_streams) < 0)
				return (-1);
			break;
		case kCTime:
		case kATime:
		case kMTime:
			if (read_Times(a, h, type) < 0)
				return (-1);
			break;
		case kName:
		{
			unsigned char *np;
			size_t nl, nb;

			/* Skip one byte. */
			if ((p = header_bytes(a, 1)) == NULL)
				return (-1);
			ll--;

 			if ((ll & 1) || ll < zip->numFiles * 4)
 				return (-1);
 
 			zip->entry_names = malloc(ll);
 			if (zip->entry_names == NULL)
 				return (-1);
			np = zip->entry_names;
			nb = ll;
			/*
			 * Copy whole file names.
			 * NOTE: This loop prevents from expanding
			 * the uncompressed buffer in order not to
			 * use extra memory resource.
			 */
			while (nb) {
				size_t b;
				if (nb > UBUFF_SIZE)
					b = UBUFF_SIZE;
				else
					b = nb;
				if ((p = header_bytes(a, b)) == NULL)
					return (-1);
				memcpy(np, p, b);
				np += b;
				nb -= b;
			}
			np = zip->entry_names;
			nl = ll;

			for (i = 0; i < zip->numFiles; i++) {
				entries[i].utf16name = np;
#if defined(_WIN32) && !defined(__CYGWIN__) && defined(_DEBUG)
				entries[i].wname = (wchar_t *)np;
#endif

				/* Find a terminator. */
				while (nl >= 2 && (np[0] || np[1])) {
					np += 2;
					nl -= 2;
				}
				if (nl < 2)
					return (-1);/* Terminator not found */
				entries[i].name_len = np - entries[i].utf16name;
				np += 2;
				nl -= 2;
			}
			break;
		}
		case kAttributes:
		{
			int allAreDefined;

 			if ((p = header_bytes(a, 2)) == NULL)
 				return (-1);
 			allAreDefined = *p;
 			h->attrBools = calloc((size_t)zip->numFiles,
 			    sizeof(*h->attrBools));
 			if (h->attrBools == NULL)
				return (-1);
			if (allAreDefined)
				memset(h->attrBools, 1, (size_t)zip->numFiles);
			else {
				if (read_Bools(a, h->attrBools,
				      (size_t)zip->numFiles) < 0)
					return (-1);
			}
			for (i = 0; i < zip->numFiles; i++) {
				if (h->attrBools[i]) {
					if ((p = header_bytes(a, 4)) == NULL)
						return (-1);
					entries[i].attr = archive_le32dec(p);
				}
			}
			break;
		}
		case kDummy:
			if (ll == 0)
				break;
		default:
			if (header_bytes(a, ll) == NULL)
				return (-1);
			break;
		}
	}

	/*
	 * Set up entry's attributes.
	 */
	folders = si->ci.folders;
	eindex = sindex = 0;
	folderIndex = indexInFolder = 0;
	for (i = 0; i < zip->numFiles; i++) {
		if (h->emptyStreamBools == NULL || h->emptyStreamBools[i] == 0)
			entries[i].flg |= HAS_STREAM;
		/* The high 16 bits of attributes is a posix file mode. */
		entries[i].mode = entries[i].attr >> 16;
		if (entries[i].flg & HAS_STREAM) {
			if ((size_t)sindex >= si->ss.unpack_streams)
				return (-1);
			if (entries[i].mode == 0)
				entries[i].mode = AE_IFREG | 0666;
			if (si->ss.digestsDefined[sindex])
				entries[i].flg |= CRC32_IS_SET;
			entries[i].ssIndex = sindex;
			sindex++;
		} else {
			int dir;
			if (h->emptyFileBools == NULL)
				dir = 1;
			else {
				if (h->emptyFileBools[eindex])
					dir = 0;
				else
					dir = 1;
				eindex++;
			}
			if (entries[i].mode == 0) {
				if (dir)
					entries[i].mode = AE_IFDIR | 0777;
				else
					entries[i].mode = AE_IFREG | 0666;
			} else if (dir &&
			    (entries[i].mode & AE_IFMT) != AE_IFDIR) {
				entries[i].mode &= ~AE_IFMT;
				entries[i].mode |= AE_IFDIR;
			}
			if ((entries[i].mode & AE_IFMT) == AE_IFDIR &&
			    entries[i].name_len >= 2 &&
			    (entries[i].utf16name[entries[i].name_len-2] != '/' ||
			     entries[i].utf16name[entries[i].name_len-1] != 0)) {
				entries[i].utf16name[entries[i].name_len] = '/';
				entries[i].utf16name[entries[i].name_len+1] = 0;
				entries[i].name_len += 2;
			}
			entries[i].ssIndex = -1;
		}
		if (entries[i].attr & 0x01)
			entries[i].mode &= ~0222;/* Read only. */

		if ((entries[i].flg & HAS_STREAM) == 0 && indexInFolder == 0) {
			/*
			 * The entry is an empty file or a directory file,
			 * those both have no contents.
			 */
			entries[i].folderIndex = -1;
			continue;
		}
		if (indexInFolder == 0) {
			for (;;) {
				if (folderIndex >= si->ci.numFolders)
					return (-1);
				if (folders[folderIndex].numUnpackStreams)
					break;
				folderIndex++;
			}
		}
		entries[i].folderIndex = folderIndex;
		if ((entries[i].flg & HAS_STREAM) == 0)
			continue;
		indexInFolder++;
		if (indexInFolder >= folders[folderIndex].numUnpackStreams) {
			folderIndex++;
			indexInFolder = 0;
		}
	}

	return (0);
}

Vulnerability Type: DoS 
CWE ID: CWE-125
Summary: The read_Header function in archive_read_support_format_7zip.c in libarchive 3.2.1 allows remote attackers to cause a denial of service (out-of-bounds read) via multiple EmptyStream attributes in a header in a 7zip archive.
Commit Message: Issue 761:  Heap overflow reading corrupted 7Zip files

The sample file that demonstrated this had multiple 'EmptyStream'
attributes.  The first one ended up being used to calculate
certain statistics, then was overwritten by the second which
was incompatible with those statistics.

The fix here is to reject any header with multiple EmptyStream
attributes.  While here, also reject headers with multiple
EmptyFile, AntiFile, Name, or Attributes markers.