Prevent possible DoS during protocol handshake.

https://bugzilla.redhat.com/show_bug.cgi?id=1399566
https://access.redhat.com/security/cve/CVE-2016-9578
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2016-9578
https://security-tracker.debian.org/tracker/CVE-2016-9578

Patch copied from upstream source repository:

https://cgit.freedesktop.org/spice/spice/commit/?h=0.12&id=f66dc643635518e53dfbe5262f814a64eec54e4a

From 1c6517973095a67c8cb57f3550fc1298404ab556 Mon Sep 17 00:00:00 2001
From: Frediano Ziglio <fziglio@redhat.com>
Date: Tue, 13 Dec 2016 14:39:48 +0000
Subject: Prevent possible DoS attempts during protocol handshake

diff --git a/server/reds.c b/server/reds.c
index f40b65c..86a33d5 100644
--- a/server/reds.c
+++ b/server/reds.c
@@ -2202,7 +2202,8 @@ static void reds_handle_read_header_done(void *opaque)
 
     reds->peer_minor_version = header->minor_version;
 
-    if (header->size < sizeof(SpiceLinkMess)) {
+    /* the check for 4096 is to avoid clients to cause arbitrary big memory allocations */
+    if (header->size < sizeof(SpiceLinkMess) || header->size > 4096) {
         reds_send_link_error(link, SPICE_LINK_ERR_INVALID_DATA);
         spice_warning("bad size %u", header->size);
         reds_link_free(link);
-- 
cgit v0.10.2