From 1966a9c18521a15d79f64fe893040e3fdb5a3790 Mon Sep 17 00:00:00 2001
From: Tim Kientzle <kientzle@acm.org>
Date: Sun, 24 Apr 2016 17:13:45 -0700
Subject: [PATCH] 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/archive_read_support_format_zip.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/libarchive/archive_read_support_format_zip.c b/libarchive/archive_read_support_format_zip.c
index 1aed84a..fa3db11 100644
--- a/libarchive/archive_read_support_format_zip.c
+++ b/libarchive/archive_read_support_format_zip.c
@@ -560,6 +560,11 @@ 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
@@ -580,6 +585,12 @@ 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) {
@@ -619,6 +630,8 @@ 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;
-- 
2.7.4