Prevent keystrokes from leaking through to the console when using evdev.
This uses the same method Weston and X use. Sadly, to be fully effective when
launching remotely, this needs root permissions.
--- a/README-raspberrypi.txt Sat Oct 12 16:29:34 2013 -0300
+++ b/README-raspberrypi.txt Sun Oct 13 17:15:43 2013 -0300
@@ -148,5 +148,8 @@
Notes
================================================================================
-* Input events from the keyboard leak through to the console
+* When launching apps remotely (via SSH), SDL can prevent local keystrokes from
+ leaking into the console only if it has root privileges. Launching apps locally
+ does not suffer from this issue.
+
--- a/src/input/evdev/SDL_evdev.c Sat Oct 12 16:29:34 2013 -0300
+++ b/src/input/evdev/SDL_evdev.c Sun Oct 13 17:15:43 2013 -0300
@@ -45,6 +45,18 @@
#include <linux/keyboard.h>
#endif
+
+/* We need this to prevent keystrokes from appear in the console */
+#ifndef KDSKBMUTE
+#define KDSKBMUTE 0x4B51
+#endif
+#ifndef KDSKBMODE
+#define KDSKBMODE 0x4B45
+#endif
+#ifndef K_OFF
+#define K_OFF 0x04
+#endif
+
#include "SDL.h"
#include "SDL_assert.h"
#include "SDL_endian.h"
@@ -370,6 +382,72 @@
return -1;
}
+/* Prevent keystrokes from reaching the tty */
+static int SDL_EVDEV_mute_keyboard(int tty, int *kb_mode)
+{
+ char arg;
+
+ *kb_mode = 0; /* FIXME: Is this a sane default in case KDGKBMODE fails? */
+ if (!IS_CONSOLE(tty)) {
+ return SDL_SetError("Tried to mute an invalid tty");
+ }
+ ioctl(tty, KDGKBMODE, kb_mode); /* It's not fatal if this fails */
+ if (ioctl(tty, KDSKBMUTE, 1) && ioctl(tty, KDSKBMODE, K_OFF)) {
+ return SDL_SetError("EVDEV: Failed muting keyboard");
+ }
+
+ return 0;
+}
+
+/* Restore the keyboard mode for given tty */
+static void SDL_EVDEV_unmute_keyboard(int tty, int kb_mode)
+{
+ if (ioctl(tty, KDSKBMUTE, 0) && ioctl(tty, KDSKBMODE, kb_mode)) {
+ SDL_Log("EVDEV: Failed restoring keyboard mode");
+ }
+}
+
+/* Read /sys/class/tty/tty0/active and open the tty */
+static int SDL_EVDEV_get_active_tty()
+{
+ int fd, len;
+ char ttyname[NAME_MAX + 1];
+ char ttypath[PATH_MAX+1] = "/dev/";
+ char arg;
+
+ fd = open("/sys/class/tty/tty0/active", O_RDONLY);
+ if (fd < 0) {
+ return SDL_SetError("Could not determine which tty is active");
+ }
+
+ len = read(fd, ttyname, NAME_MAX);
+ close(fd);
+
+ if (len <= 0) {
+ return SDL_SetError("Could not read which tty is active");
+ }
+
+ if (ttyname[len-1] == '\n') {
+ ttyname[len-1] = '\0';
+ }
+ else {
+ ttyname[len] = '\0';
+ }
+
+ SDL_strlcat(ttypath, ttyname, PATH_MAX);
+ fd = open(ttypath, O_RDWR | O_NOCTTY);
+ if (fd < 0) {
+ return SDL_SetError("Could not open tty: %s", ttypath);
+ }
+
+ if (!IS_CONSOLE(fd)) {
+ close(fd);
+ return SDL_SetError("Invalid tty obtained: %s", ttypath);
+ }
+
+ return fd;
+}
+
int
SDL_EVDEV_Init(void)
{
@@ -403,6 +481,19 @@
/* We need a physical terminal (not PTS) to be able to translate key code to symbols via the kernel tables */
_this->console_fd = SDL_EVDEV_get_console_fd();
+
+ /* Mute the keyboard so keystrokes only generate evdev events and do not leak through to the console */
+ _this->tty = STDIN_FILENO;
+ if (SDL_EVDEV_mute_keyboard(_this->tty, &_this->kb_mode) < 0) {
+ /* stdin is not a tty, probably we were launched remotely, so we try to disable the active tty */
+ _this->tty = SDL_EVDEV_get_active_tty();
+ if (_this->tty >= 0) {
+ if (SDL_EVDEV_mute_keyboard(_this->tty, &_this->kb_mode) < 0) {
+ close(_this->tty);
+ _this->tty = -1;
+ }
+ }
+ }
}
_this->ref_count += 1;
@@ -429,6 +520,12 @@
if (_this->console_fd >= 0) {
close(_this->console_fd);
}
+
+ if (_this->tty >= 0) {
+ SDL_EVDEV_unmute_keyboard(_this->tty, _this->kb_mode);
+ close(_this->tty);
+ }
+
/* Remove existing devices */
while(_this->first != NULL) {
SDL_EVDEV_device_removed(_this->first->path);
--- a/src/input/evdev/SDL_evdev.h Sat Oct 12 16:29:34 2013 -0300
+++ b/src/input/evdev/SDL_evdev.h Sun Oct 13 17:15:43 2013 -0300
@@ -43,6 +43,8 @@
int numdevices;
int ref_count;
int console_fd;
+ int kb_mode;
+ int tty;
} SDL_EVDEV_PrivateData;
extern int SDL_EVDEV_Init(void);