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.
libarchive · Apr 25, 2016 · d0331e8 · d0331e8
1 parent 1185535
commit d0331e8
Showing 1 changed file with 13 additions and 0 deletions.
diff --git a/libarchive/archive_read_support_format_zip.c b/libarchive/archive_read_support_format_zip.c
@@ -2778,6 +2778,11 @@ zip_read_mac_metadata(struct archive_read *a, struct archive_entry *entry,
 
 	switch(rsrc->compression) {
 	case 0:  /* No compression. */
+		if (rsrc->uncompressed_size != rsrc->compressed_size) {
+			archive_set_error(&a->archive, ARCHIVE_ERRNO_FILE_FORMAT,
+			    "Malformed OS X metadata entry: inconsistent size");
+			return (ARCHIVE_FATAL);
+		}
 #ifdef HAVE_ZLIB_H
 	case 8: /* Deflate compression. */
 #endif
@@ -2798,6 +2803,12 @@ zip_read_mac_metadata(struct archive_read *a, struct archive_entry *entry,
 		    (intmax_t)rsrc->uncompressed_size);
 		return (ARCHIVE_WARN);
 	}
+	if (rsrc->compressed_size > (4 * 1024 * 1024)) {
+		archive_set_error(&a->archive, ARCHIVE_ERRNO_FILE_FORMAT,
+		    "Mac metadata is too large: %jd > 4M bytes",
+		    (intmax_t)rsrc->compressed_size);
+		return (ARCHIVE_WARN);
+	}
 
 	metadata = malloc((size_t)rsrc->uncompressed_size);
 	if (metadata == NULL) {
@@ -2836,6 +2847,8 @@ zip_read_mac_metadata(struct archive_read *a, struct archive_entry *entry,
 			bytes_avail = remaining_bytes;
 		switch(rsrc->compression) {
 		case 0:  /* No compression. */
+			if ((size_t)bytes_avail > metadata_bytes)
+				bytes_avail = metadata_bytes;
 			memcpy(mp, p, bytes_avail);
 			bytes_used = (size_t)bytes_avail;
 			metadata_bytes -= bytes_used;