From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Frediano Ziglio <fziglio@redhat.com>
Date: Thu, 26 Jan 2017 15:53:18 +0000
Subject: [PATCH] reds: Check link header magic without waiting for the whole
 header

This allows the connection to early fail in case initial bytes
are not correct.
This allows for instance VNC client to graceful fail connecting
to a spice-server. This happens easily as the two protocols
share the same range of ports.

This resolves rhbz#1416692.

Signed-off-by: Frediano Ziglio <fziglio@redhat.com>
Acked-by: Christophe Fergeau <cfergeau@redhat.com>
---
 server/reds.c | 28 ++++++++++++++++++++--------
 1 file changed, 20 insertions(+), 8 deletions(-)

diff --git a/server/reds.c b/server/reds.c
index c639aa3..57a93c9 100644
--- a/server/reds.c
+++ b/server/reds.c
@@ -2192,12 +2192,6 @@ static void reds_handle_read_header_done(void *opaque)
     header->minor_version = GUINT32_FROM_LE(header->minor_version);
     header->size = GUINT32_FROM_LE(header->size);
 
-    if (header->magic != SPICE_MAGIC) {
-        reds_send_link_error(link, SPICE_LINK_ERR_INVALID_MAGIC);
-        reds_link_free(link);
-        return;
-    }
-
     if (header->major_version != SPICE_VERSION_MAJOR) {
         if (header->major_version > 0) {
             reds_send_link_error(link, SPICE_LINK_ERR_VERSION_MISMATCH);
@@ -2227,13 +2221,31 @@ static void reds_handle_read_header_done(void *opaque)
                            link);
 }
 
+static void reds_handle_read_magic_done(void *opaque)
+{
+    RedLinkInfo *link = (RedLinkInfo *)opaque;
+    const SpiceLinkHeader *header = &link->link_header;
+
+    if (header->magic != SPICE_MAGIC) {
+        reds_send_link_error(link, SPICE_LINK_ERR_INVALID_MAGIC);
+        reds_link_free(link);
+        return;
+    }
+
+    reds_stream_async_read(link->stream,
+                           ((uint8_t *)&link->link_header) + sizeof(header->magic),
+                           sizeof(SpiceLinkHeader) - sizeof(header->magic),
+                           reds_handle_read_header_done,
+                           link);
+}
+
 static void reds_handle_new_link(RedLinkInfo *link)
 {
     reds_stream_set_async_error_handler(link->stream, reds_handle_link_error);
     reds_stream_async_read(link->stream,
                            (uint8_t *)&link->link_header,
-                           sizeof(SpiceLinkHeader),
-                           reds_handle_read_header_done,
+                           sizeof(link->link_header.magic),
+                           reds_handle_read_magic_done,
                            link);
 }