Fix buffer overflow in inflateGetHeader()

This is the initial fix combined with a fix for a NULL deref introduced
in the initial fix.

ok millert, help from tj

commit eff308af425b67093bab25f80f1ae950166bece1
Author: Mark Adler <fork@madler.net>
Date:   Sat Jul 30 15:51:11 2022 -0700

    Fix a bug when getting a gzip header extra field with inflate().

    If the extra field was larger than the space the user provided with
    inflateGetHeader(), and if multiple calls of inflate() delivered
    the extra header data, then there could be a buffer overflow of the
    provided space. This commit assures that provided space is not
    exceeded.

https://github.com/madler/zlib/commit/eff308af425b67093bab25f80f1ae950166bece1

commit 1eb7682f845ac9e9bf9ae35bbfb3bad5dacbd91d (HEAD -> develop, origin/develop)
Author: Mark Adler <fork@madler.net>
Date:   Mon Aug 8 10:50:09 2022 -0700

    Fix extra field processing bug that dereferences NULL state->head.

    The recent commit to fix a gzip header extra field processing bug
    introduced the new bug fixed here.

https://github.com/madler/zlib/commit/1eb7682f845ac9e9bf9ae35bbfb3bad5dacbd91d

diff --git a/lib/libz/inflate.c b/lib/libz/inflate.c
index 63e81d0..e941ef6 100644 (file)
--- a/lib/libz/inflate.c
+++ b/lib/libz/inflate.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: inflate.c,v 1.12 2022/05/08 14:04:22 tb Exp $ */
+/*     $OpenBSD: inflate.c,v 1.13 2022/08/09 07:37:35 tb Exp $ */
 /* inflate.c -- zlib decompression
  * Copyright (C) 1995-2022 Mark Adler
  * For conditions of distribution and use, see copyright notice in zlib.h
@@ -785,8 +785,9 @@ int flush;
                 if (copy > have) copy = have;
                 if (copy) {
                     if (state->head != Z_NULL &&
-                        state->head->extra != Z_NULL) {
-                        len = state->head->extra_len - state->length;
+                        state->head->extra != Z_NULL &&
+                        (len = state->head->extra_len - state->length) <
+                           state->head->extra_max) {
                         zmemcpy(state->head->extra + len, next,
                                 len + copy > state->head->extra_max ?
                                 state->head->extra_max - len : copy);