Code: zip_read_mac_metadata(struct archive_read *a, struct archive_entry *entry,
    struct zip_entry *rsrc)
{
	struct zip *zip = (struct zip *)a->format->data;
	unsigned char *metadata, *mp;
	int64_t offset = archive_filter_bytes(&a->archive, 0);
	size_t remaining_bytes, metadata_bytes;
	ssize_t hsize;
	int ret = ARCHIVE_OK, eof;
 
 	switch(rsrc->compression) {
 	case 0:  /* No compression. */
 #ifdef HAVE_ZLIB_H
 	case 8: /* Deflate compression. */
 #endif
		break;
	default: /* Unsupported compression. */
		/* Return a warning. */
		archive_set_error(&a->archive, ARCHIVE_ERRNO_FILE_FORMAT,
		    "Unsupported ZIP compression method (%s)",
		    compression_name(rsrc->compression));
		/* We can't decompress this entry, but we will
		 * be able to skip() it and try the next entry. */
		return (ARCHIVE_WARN);
	}

	if (rsrc->uncompressed_size > (4 * 1024 * 1024)) {
		archive_set_error(&a->archive, ARCHIVE_ERRNO_FILE_FORMAT,
		    "Mac metadata is too large: %jd > 4M bytes",
 		    (intmax_t)rsrc->uncompressed_size);
 		return (ARCHIVE_WARN);
 	}
 
 	metadata = malloc((size_t)rsrc->uncompressed_size);
 	if (metadata == NULL) {
		archive_set_error(&a->archive, ENOMEM,
		    "Can't allocate memory for Mac metadata");
		return (ARCHIVE_FATAL);
	}

	if (offset < rsrc->local_header_offset)
		__archive_read_consume(a, rsrc->local_header_offset - offset);
	else if (offset != rsrc->local_header_offset) {
		__archive_read_seek(a, rsrc->local_header_offset, SEEK_SET);
	}

	hsize = zip_get_local_file_header_size(a, 0);
	__archive_read_consume(a, hsize);

	remaining_bytes = (size_t)rsrc->compressed_size;
	metadata_bytes = (size_t)rsrc->uncompressed_size;
	mp = metadata;
	eof = 0;
	while (!eof && remaining_bytes) {
		const unsigned char *p;
		ssize_t bytes_avail;
		size_t bytes_used;

		p = __archive_read_ahead(a, 1, &bytes_avail);
		if (p == NULL) {
			archive_set_error(&a->archive,
			    ARCHIVE_ERRNO_FILE_FORMAT,
			    "Truncated ZIP file header");
			ret = ARCHIVE_WARN;
			goto exit_mac_metadata;
		}
		if ((size_t)bytes_avail > remaining_bytes)
 			bytes_avail = remaining_bytes;
 		switch(rsrc->compression) {
 		case 0:  /* No compression. */
 			memcpy(mp, p, bytes_avail);
 			bytes_used = (size_t)bytes_avail;
 			metadata_bytes -= bytes_used;
			mp += bytes_used;
			if (metadata_bytes == 0)
				eof = 1;
			break;
#ifdef HAVE_ZLIB_H
		case 8: /* Deflate compression. */
		{
			int r;

			ret = zip_deflate_init(a, zip);
			if (ret != ARCHIVE_OK)
				goto exit_mac_metadata;
			zip->stream.next_in =
			    (Bytef *)(uintptr_t)(const void *)p;
			zip->stream.avail_in = (uInt)bytes_avail;
			zip->stream.total_in = 0;
			zip->stream.next_out = mp;
			zip->stream.avail_out = (uInt)metadata_bytes;
			zip->stream.total_out = 0;

			r = inflate(&zip->stream, 0);
			switch (r) {
			case Z_OK:
				break;
			case Z_STREAM_END:
				eof = 1;
				break;
			case Z_MEM_ERROR:
				archive_set_error(&a->archive, ENOMEM,
				    "Out of memory for ZIP decompression");
				ret = ARCHIVE_FATAL;
				goto exit_mac_metadata;
			default:
				archive_set_error(&a->archive,
				    ARCHIVE_ERRNO_MISC,
				    "ZIP decompression failed (%d)", r);
				ret = ARCHIVE_FATAL;
				goto exit_mac_metadata;
			}
			bytes_used = zip->stream.total_in;
			metadata_bytes -= zip->stream.total_out;
			mp += zip->stream.total_out;
			break;
		}
#endif
		default:
			bytes_used = 0;
			break;
		}
		__archive_read_consume(a, bytes_used);
		remaining_bytes -= bytes_used;
	}
	archive_entry_copy_mac_metadata(entry, metadata,
	    (size_t)rsrc->uncompressed_size - metadata_bytes);

exit_mac_metadata:
	__archive_read_seek(a, offset, SEEK_SET);
	zip->decompress_init = 0;
	free(metadata);
	return (ret);
}

Vulnerability Type: Exec Code Overflow 
CWE ID: CWE-20
Summary: Heap-based buffer overflow in the zip_read_mac_metadata function in archive_read_support_format_zip.c in libarchive before 3.2.0 allows remote attackers to execute arbitrary code via crafted entry-size values in a ZIP archive.
Commit Message: Issue #656:  Fix CVE-2016-1541, VU#862384

When reading OS X metadata entries in Zip archives that were stored
without compression, libarchive would use the uncompressed entry size
to allocate a buffer but would use the compressed entry size to limit
the amount of data copied into that buffer.  Since the compressed
and uncompressed sizes are provided by data in the archive itself,
an attacker could manipulate these values to write data beyond
the end of the allocated buffer.

This fix provides three new checks to guard against such
manipulation and to make libarchive generally more robust when
handling this type of entry:
 1. If an OS X metadata entry is stored without compression,
    abort the entire archive if the compressed and uncompressed
    data sizes do not match.
 2. When sanity-checking the size of an OS X metadata entry,
    abort this entry if either the compressed or uncompressed
    size is larger than 4MB.
 3. When copying data into the allocated buffer, check the copy
    size against both the compressed entry size and uncompressed
    entry size.