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Xnamespace: filter extension access 

Whitelist several extension calls that are safe. Also allow namespaces
to be configured for unrestricted access.

TBD: doesn't actually reject yet

Signed-off-by: Enrico Weigelt, metux IT consult <info@metux.net>
This commit is contained in:
Enrico Weigelt, metux IT consult 2025-03-19 10:50:56 +01:00
parent 81faed9c8c
commit 14008eb698
7 changed files with 189 additions and 0 deletions
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3
Xext/namespace/config.c
View File

@ -7,6 +7,9 @@
struct Xnamespace ns_root = {
.allowMouseMotion = TRUE,
.allowShape = TRUE,
.allowXInput = TRUE,
.allowXKeyboard = TRUE,
.builtin = TRUE,
.name = NS_NAME_ROOT,
.refcnt = 1,

67
Xext/namespace/hook-ext-access.c Normal file
View File

@ -0,0 +1,67 @@
#define HOOK_NAME "ext-access"
#include <dix-config.h>
#include "dix/dix_priv.h"
#include "dix/extension_priv.h"
#include "dix/registry_priv.h"
#include "Xext/xacestr.h"
#include "namespace.h"
#include "hooks.h"
/* called on X_QueryExtension */
void hookExtAccess(CallbackListPtr *pcbl, void *unused, void *calldata)
{
XNS_HOOK_HEAD(XaceExtAccessRec);
/* root NS has super powers */
if (subj->ns->superPower)
goto pass;
switch (param->ext->index + EXTENSION_BASE) {
/* unrestricted access */
case EXTENSION_MAJOR_BIG_REQUESTS:
case EXTENSION_MAJOR_DAMAGE:
case EXTENSION_MAJOR_DOUBLE_BUFFER:
case EXTENSION_MAJOR_GENERIC_EVENT:
case EXTENSION_MAJOR_PRESENT:
case EXTENSION_MAJOR_SYNC:
case EXTENSION_MAJOR_XC_MISC:
case EXTENSION_MAJOR_XFIXES:
case EXTENSION_MAJOR_XKEYBOARD:
case EXTENSION_MAJOR_XRESOURCE:
goto pass;
/* really blacklisted */
case EXTENSION_MAJOR_MIT_SCREEN_SAVER:
case EXTENSION_MAJOR_RECORD:
case EXTENSION_MAJOR_SECURITY:
case EXTENSION_MAJOR_XTEST:
case EXTENSION_MAJOR_XVIDEO:
goto reject;
/* only allowed if namespace has flag set */
case EXTENSION_MAJOR_SHAPE:
if (subj->ns->allowShape)
goto pass;
goto reject;
/* only allowed if namespace has flag set */
case EXTENSION_MAJOR_XINPUT:
if (subj->ns->allowXInput)
goto pass;
goto reject;
}
XNS_HOOK_LOG("unhandled extension query: %s (%d)\n", param->ext->name, param->ext->index);
return;
reject:
param->status = BadAccess;
return;
pass:
param->status = Success;
return;
}

110
Xext/namespace/hook-ext-dispatch.c Normal file
View File

@ -0,0 +1,110 @@
#define HOOK_NAME "ext-dispatch"
#include <dix-config.h>
#include <stdio.h>
#include <X11/Xdefs.h> // syncproto.h is broken
#include <X11/Xmd.h>
#include <X11/extensions/syncproto.h>
#include <X11/extensions/XKB.h>
#include <X11/extensions/xfixeswire.h>
#include "dix/dix_priv.h"
#include "dix/extension_priv.h"
#include "dix/registry_priv.h"
#include "Xext/xacestr.h"
#include "namespace.h"
#include "hooks.h"
void hookExtDispatch(CallbackListPtr *pcbl, void *unused, void *calldata)
{
XNS_HOOK_HEAD(XaceExtAccessRec);
/* root NS has super powers */
if (subj->ns->superPower)
goto pass;
switch (client->majorOp) {
/* unrestricted access to these */
case EXTENSION_MAJOR_BIG_REQUESTS:
case EXTENSION_MAJOR_DAMAGE:
case EXTENSION_MAJOR_DOUBLE_BUFFER:
case EXTENSION_MAJOR_GENERIC_EVENT:
case EXTENSION_MAJOR_PRESENT:
case EXTENSION_MAJOR_XC_MISC:
case EXTENSION_MAJOR_XRESOURCE:
goto pass;
/* allow several operations */
case EXTENSION_MAJOR_XKEYBOARD:
if (subj->ns->allowXKeyboard)
goto pass;
switch (client->minorOp) {
case X_kbUseExtension:
case X_kbGetMap:
case X_kbSelectEvents: // fixme: might need special filtering
case X_kbGetState:
case X_kbGetNames:
case X_kbGetControls:
case X_kbPerClientFlags:
goto pass;
}
XNS_HOOK_LOG("BLOCKED unhandled XKEYBOARD call: %s\n", param->ext->name);
goto reject;
/* allow if namespace has flag set */
case EXTENSION_MAJOR_SHAPE:
if (subj->ns->allowShape)
goto pass;
break;
case EXTENSION_MAJOR_XINPUT:
if (subj->ns->allowXInput)
goto pass;
break;
case EXTENSION_MAJOR_XFIXES:
switch (client->minorOp) {
case X_XFixesQueryVersion:
case X_XFixesCreateRegion:
case X_XFixesSetCursorName:
case X_XFixesSelectSelectionInput:
goto pass;
}
XNS_HOOK_LOG("BLOCKED unhandled XFIXES call: %s\n", param->ext->name);
goto reject;
break;
case EXTENSION_MAJOR_SYNC:
switch (client->minorOp) {
case X_SyncCreateCounter:
case X_SyncDestroyCounter:
case X_SyncInitialize:
case X_SyncSetCounter:
goto pass;
}
XNS_HOOK_LOG("REJECT unhandled SYNC call: %s\n", param->ext->name);
goto reject;
break;
/* really blacklisted */
case EXTENSION_MAJOR_MIT_SCREEN_SAVER:
case EXTENSION_MAJOR_RECORD:
case EXTENSION_MAJOR_SECURITY:
case EXTENSION_MAJOR_XTEST:
goto reject;
break;
}
XNS_HOOK_LOG("unhandled extension call: %s\n", param->ext->name);
return;
reject:
XNS_HOOK_LOG("rejecting extension call: %s\n", param->ext->name);
param->status = BadAccess;
return;
pass:
param->status = Success;
return;
}

2
Xext/namespace/hooks.h
View File

@ -25,6 +25,8 @@
struct XnamespaceClientPriv *subj = XnsClientPriv(client);
void hookClientState(CallbackListPtr *pcbl, void *unused, void *calldata);
void hookExtAccess(CallbackListPtr *pcbl, void *unused, void *calldata);
void hookExtDispatch(CallbackListPtr *pcbl, void *unused, void *calldata);
void hookInitRootWindow(CallbackListPtr *pcbl, void *unused, void *calldata);
void hookReceive(CallbackListPtr *pcbl, void *unused, void *calldata);
void hookSelectionFilter(CallbackListPtr *pcbl, void *unused, void *calldata);

2
Xext/namespace/meson.build
View File

@ -3,6 +3,8 @@ libxserver_namespace = static_library(
[
'config.c',
'hook-clientstate.c',
'hook-ext-access.c',
'hook-ext-dispatch.c',
'hook-init-rootwindow.c',
'hook-receive.c',
'hook-selection.c',

2
Xext/namespace/namespace.c
View File

@ -34,6 +34,8 @@ NamespaceExtensionInit(void)
AddCallback(&PostInitRootWindowCallback, hookInitRootWindow, NULL) &&
AddCallback(&PropertyFilterCallback, hookWindowProperty, NULL) &&
AddCallback(&SelectionFilterCallback, hookSelectionFilter, NULL) &&
XaceRegisterCallback(XACE_EXT_DISPATCH, hookExtDispatch, NULL) &&
XaceRegisterCallback(XACE_EXT_ACCESS, hookExtAccess, NULL) &&
XaceRegisterCallback(XACE_RECEIVE_ACCESS, hookReceive, NULL)))
FatalError("NamespaceExtensionInit: allocation failure\n");

3
Xext/namespace/namespace.h
View File

@ -15,6 +15,9 @@ struct Xnamespace {
const char *name;
Bool builtin;
Bool allowMouseMotion;
Bool allowShape;
Bool allowXInput;
Bool allowXKeyboard;
Bool superPower;
const char *authProto;
char *authTokenData;