From 215f894965df5fb0bb45b107d84524e700d2073c Mon Sep 17 00:00:00 2001
From: Michal Srb <msrb@suse.com>
Date: Wed, 24 May 2017 15:54:40 +0300
Subject: dix: Disallow GenericEvent in SendEvent request.

The SendEvent request holds xEvent which is exactly 32 bytes long, no more,
no less. Both ProcSendEvent and SProcSendEvent verify that the received data
exactly match the request size. However nothing stops the client from passing
in event with xEvent::type = GenericEvent and any value of
xGenericEvent::length.

In the case of ProcSendEvent, the event will be eventually passed to
WriteEventsToClient which will see that it is Generic event and copy the
arbitrary length from the receive buffer (and possibly past it) and send it to
the other client. This allows clients to copy unitialized heap memory out of X
server or to crash it.

In case of SProcSendEvent, it will attempt to swap the incoming event by
calling a swapping function from the EventSwapVector array. The swapped event
is written to target buffer, which in this case is local xEvent variable. The
xEvent variable is 32 bytes long, but the swapping functions for GenericEvents
expect that the target buffer has size matching the size of the source
GenericEvent. This allows clients to cause stack buffer overflows.

Signed-off-by: Michal Srb <msrb@suse.com>
Reviewed-by: Peter Hutterer <peter.hutterer@who-t.net>
Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>

diff --git a/dix/events.c b/dix/events.c
index 3e3a01e..d3a33ea 100644
--- a/dix/events.c
+++ b/dix/events.c
@@ -5366,6 +5366,12 @@ ProcSendEvent(ClientPtr client)
         client->errorValue = stuff->event.u.u.type;
         return BadValue;
     }
+    /* Generic events can have variable size, but SendEvent request holds
+       exactly 32B of event data. */
+    if (stuff->event.u.u.type == GenericEvent) {
+        client->errorValue = stuff->event.u.u.type;
+        return BadValue;
+    }
     if (stuff->event.u.u.type == ClientMessage &&
         stuff->event.u.u.detail != 8 &&
         stuff->event.u.u.detail != 16 && stuff->event.u.u.detail != 32) {
diff --git a/dix/swapreq.c b/dix/swapreq.c
index 719e9b8..6785059 100644
--- a/dix/swapreq.c
+++ b/dix/swapreq.c
@@ -292,6 +292,13 @@ SProcSendEvent(ClientPtr client)
     swapl(&stuff->destination);
     swapl(&stuff->eventMask);
 
+    /* Generic events can have variable size, but SendEvent request holds
+       exactly 32B of event data. */
+    if (stuff->event.u.u.type == GenericEvent) {
+        client->errorValue = stuff->event.u.u.type;
+        return BadValue;
+    }
+
     /* Swap event */
     proc = EventSwapVector[stuff->event.u.u.type & 0177];
     if (!proc || proc == NotImplemented)        /* no swapping proc; invalid event type? */
-- 
cgit v0.10.2

From 8caed4df36b1f802b4992edcfd282cbeeec35d9d Mon Sep 17 00:00:00 2001
From: Michal Srb <msrb@suse.com>
Date: Wed, 24 May 2017 15:54:41 +0300
Subject: Xi: Verify all events in ProcXSendExtensionEvent.

The requirement is that events have type in range
EXTENSION_EVENT_BASE..lastEvent, but it was tested
only for first event of all.

Signed-off-by: Michal Srb <msrb@suse.com>
Reviewed-by: Peter Hutterer <peter.hutterer@who-t.net>
Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>

diff --git a/Xi/sendexev.c b/Xi/sendexev.c
index 1cf118a..5e63bfc 100644
--- a/Xi/sendexev.c
+++ b/Xi/sendexev.c
@@ -117,7 +117,7 @@ SProcXSendExtensionEvent(ClientPtr client)
 int
 ProcXSendExtensionEvent(ClientPtr client)
 {
-    int ret;
+    int ret, i;
     DeviceIntPtr dev;
     xEvent *first;
     XEventClass *list;
@@ -141,10 +141,12 @@ ProcXSendExtensionEvent(ClientPtr client)
     /* The client's event type must be one defined by an extension. */
 
     first = ((xEvent *) &stuff[1]);
-    if (!((EXTENSION_EVENT_BASE <= first->u.u.type) &&
-          (first->u.u.type < lastEvent))) {
-        client->errorValue = first->u.u.type;
-        return BadValue;
+    for (i = 0; i < stuff->num_events; i++) {
+        if (!((EXTENSION_EVENT_BASE <= first[i].u.u.type) &&
+            (first[i].u.u.type < lastEvent))) {
+            client->errorValue = first[i].u.u.type;
+            return BadValue;
+        }
     }
 
     list = (XEventClass *) (first + stuff->num_events);
-- 
cgit v0.10.2

From ba336b24052122b136486961c82deac76bbde455 Mon Sep 17 00:00:00 2001
From: Michal Srb <msrb@suse.com>
Date: Wed, 24 May 2017 15:54:42 +0300
Subject: Xi: Do not try to swap GenericEvent.

The SProcXSendExtensionEvent must not attempt to swap GenericEvent because
it is assuming that the event has fixed size and gives the swapping function
xEvent-sized buffer.

A GenericEvent would be later rejected by ProcXSendExtensionEvent anyway.

Signed-off-by: Michal Srb <msrb@suse.com>
Reviewed-by: Peter Hutterer <peter.hutterer@who-t.net>
Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>

diff --git a/Xi/sendexev.c b/Xi/sendexev.c
index 5e63bfc..5c2e0fc 100644
--- a/Xi/sendexev.c
+++ b/Xi/sendexev.c
@@ -95,9 +95,17 @@ SProcXSendExtensionEvent(ClientPtr client)
 
     eventP = (xEvent *) &stuff[1];
     for (i = 0; i < stuff->num_events; i++, eventP++) {
+        if (eventP->u.u.type == GenericEvent) {
+            client->errorValue = eventP->u.u.type;
+            return BadValue;
+        }
+
         proc = EventSwapVector[eventP->u.u.type & 0177];
-        if (proc == NotImplemented)     /* no swapping proc; invalid event type? */
+        /* no swapping proc; invalid event type? */
+        if (proc == NotImplemented) {
+            client->errorValue = eventP->u.u.type;
             return BadValue;
+        }
         (*proc) (eventP, &eventT);
         *eventP = eventT;
     }
-- 
cgit v0.10.2

