emerg-shutdown: fix the hang-on-shutdown bug, add autodetection of new keyboards, shutdown key configuration, and instant shutdown option

etc/security-misc/emerg-shutdown/30_security_misc.conf

@@ -0,0 +1,19 @@
+## Copyright (C) 2025 - 2025 ENCRYPTED SUPPORT LLC <adrelanos@whonix.org>
+## See the file COPYING for copying conditions.
+
+## Please use "/etc/security-misc/emerg-shutdown/50_user.conf" for your custom
+## configuration, which will override the defaults found here.
+## When Kicksecure is updated, this file may be overwritten.
+
+## Set the key combo for forcing immediate shutdown. See the "Keys and
+## buttons" section of "/usr/include/linux/input-event-codes.h" for possibly
+## supported values. Not all keys are supported.
+##
+## All specified keys must be depressed at the same time to trigger a
+## shutdown. Use a comma (",") to separate keys. If you want to alias certain
+## keys to each other from emerg-shutdown's standpoint, use a pipe
+## character("|").
+##
+## The default key sequence triggers a shutdown when Ctrl+Alt+Delete is
+## pressed, allowing the use of either the left or right Ctrl and Alt keys.
+EMERG_SHUTDOWN_KEYS="KEY_LEFTCTRL|KEY_RIGHTCTRL,KEY_LEFTALT|KEY_RIGHTALT,KEY_DELETE"

usr/lib/systemd/system/emerg-shutdown.service

@@ -6,9 +6,8 @@ Description=Emergency shutdown when boot media is removed
 Documentation=https://github.com/Kicksecure/security-misc
 
 [Service]
-Type=oneshot
+Type=exec
 ExecStart=/usr/libexec/security-misc/emerg-shutdown
-RemainAfterExit=true
 
 [Install]
 WantedBy=multi-user.target

usr/lib/udev/rules.d/95-emerg-shutdown.rules

@@ -0,0 +1,9 @@
+SUBSYSTEM!="input", GOTO="end"
+
+# new keyboard or mouse attached or removed, restart emerg-shutdown
+KERNEL=="event*", ACTION=="add", ENV{ID_INPUT_KEYBOARD}=="1", RUN+="/usr/bin/systemctl restart emerg-shutdown.service"
+KERNEL=="event*", ACTION=="add", ENV{ID_INPUT_KEYBOARD}=="1", GOTO="end"
+KERNEL=="event*", ACTION=="remove", ENV{ID_INPUT_KEYBOARD}=="1", RUN+="/usr/bin/systemctl restart emerg-shutdown.service"
+KERNEL=="event*", ACTION=="remove", ENV{ID_INPUT_KEYBOARD}=="1", GOTO="end"
+
+LABEL="end"

usr/libexec/security-misc/emerg-shutdown

@@ -3,25 +3,49 @@
 # Copyright (C) 2025 - 2025 ENCRYPTED SUPPORT LLC <adrelanos@whonix.org>
 # See the file COPYING for copying conditions.
 
-gcc \
+set -o errexit
-  -o \
+set -o nounset
-  /run/emerg-shutdown \
+set -o errtrace
-  -static \
+set -o pipefail
-  /usr/src/security-misc/emerg-shutdown.c \
-  || {
-    printf "%s\n" 'Could not compile force-shutdown executable!'
-    exit 1;
-  }
 
-readarray -t root_devices < <(/usr/libexec/helper-scripts/get-backing-devices-for-mountpoint '/');
+## Make sure globs sort in a predictable, reproducible fashion
+export LC_ALL=C
 
-## memlockd daemonizes itself, so no need to background it
+## Read emergency shutdown key configuration
-memlockd -c /usr/share/security-misc/security-misc-memlockd.cfg
+for config_file in /etc/security-misc/emerg-shutdown/*.conf; do
+  source "${config_file}"
+done
+if [ -z "${EMERG_SHUTDOWN_KEYS}" ]; then
+  ## Default to Ctrl+Alt+Delete if nothing else is set
+  EMERG_SHUTDOWN_KEYS="KEY_LEFTCTRL|KEY_RIGHTCTRL,KEY_LEFTALT|KEY_RIGHTALT,KEY_DELETE"
+fi
 
+## Find the devices that make up the root device
+readarray -t root_devices < <(/usr/libexec/helper-scripts/get-backing-devices-for-mountpoint '/') || true;
+if [ "${#root_devices[@]}" = '0' ] \
+  || [ "${root_devices[0]}" == '' ]; then
+  ## /dev/sda1 might be the right one...
+  root_devices[0]='/dev/sda1'
+fi
+
+## Build the actual emerg-shutdown executable
+if [ ! -f '/run/emerg-shutdown' ]; then
+  gcc \
+    -o \
+    /run/emerg-shutdown \
+    -static \
+    /usr/src/security-misc/emerg-shutdown.c \
+    || {
+      printf "%s\n" 'Could not compile force-shutdown executable!'
+      exit 1;
+    }
+
+fi
+
+## memlockd daemonizes itself, so no need to background it.
+memlockd -c /usr/share/security-misc/security-misc-memlockd.cfg || true
+
+## Launch emerg-shutdown
 OLDIFS="$IFS"
 IFS=','
-/run/emerg-shutdown "--devices=${root_devices[*]}" '--keys=KEY_LEFTCTRL|KEY_RIGHTCTRL,KEY_LEFTALT|KEY_RIGHTALT,KEY_DELETE' &
+/run/emerg-shutdown "--devices=${root_devices[*]}" "--keys=${EMERG_SHUTDOWN_KEYS}"
-IFS="$OLDIFS"
-sleep 1
-disown
-exit 0

usr/src/security-misc/emerg-shutdown.c

@@ -94,6 +94,8 @@
 #include <stdbool.h>
 #include <poll.h>
 #include <linux/input.h>
+#include <linux/vt.h>
+#include <sys/ioctl.h>
 #include <sys/syscall.h>
 
 #define fd_stdin 0
@@ -104,6 +106,8 @@
 #define input_path_size 20
 #define key_flags_len 12
 
+int console_fd = 0;
+
 /* Adapted from kloak/src/keycodes.c */
 struct name_value {
     const char *name;
@@ -283,6 +287,8 @@ void print(int fd, char *str) {
 void print_usage() {
   print(fd_stderr, "Usage:\n");
   print(fd_stderr, "  emerg-shutdown --devices=DEVICE1[,DEVICE2...] --keys=KEY_1[,KEY_2|KEY_3...]\n");
+  print(fd_stderr, "Or:\n");
+  print(fd_stderr, "  emerg-shutdown --instant-shutdown\n");
   print(fd_stderr, "Example:\n");
   print(fd_stderr, "  emerg-shutdown --devices=/dev/sda3 --keys=KEY_POWER\n");
 }
@@ -363,7 +369,74 @@ void load_list(const char *arg, size_t *result_list_len_ref, char ***result_list
 }
 
 int kill_system() {
-  return syscall(SYS_reboot, LINUX_REBOOT_MAGIC1, LINUX_REBOOT_MAGIC2, LINUX_REBOOT_CMD_POWER_OFF, NULL);
+  /*
+   * It isn't safe to simply call the reboot syscall here - there is a
+   * graphics driver bug in the i915 driver on Bookworm that will throw a
+   * kernel warning during shutdown. Kicksecure sets panic_on_oops and
+   * panic_on_warn to 1 during bootup, which means this bug will cause a
+   * kernel panic and thus hang the system rather than shutting down.
+   *
+   * To mitigate this, we do two things:
+   *
+   * - We disable the panic_on_oops and panic_on_warn kernel settings before
+   *   calling the reboot syscall. This way if a warn or oops does occur, at
+   *   least it isn't as likely to block shutdown.
+   * - We switch virtual terminals before initiating the shutdown. This should
+   *   hopefully keep whatever is going wrong from going wrong in the first
+   *   place.
+   *
+   * This is probably a good idea for any system, because switching TTYs is a
+   * rather basic operation that is likely to work, while forcibly shutting
+   * down while X11 or Wayland still has control of the display is probably
+   * not as well tested (if it's been tested at all).
+   *
+   * Above all else though, we want to at least *try* to shutdown. Even if all
+   * our attempts to switch VTs fail and /proc isn't available for us to tweak
+   * kernel settings, we still need to try. Therefore we absolutely do not
+   * crash or block, except when waiting for a VT to become activated. (If VT
+   * activation blocks forever, the kernel is probably horribly broken and
+   * would probably panic imminently anyway.)
+   */
+
+  const char *panic_on_oops_path = "/proc/sys/kernel/panic_on_oops";
+  const char *panic_on_warn_path = "/proc/sys/kernel/panic_on_warn";
+
+  int ret = 0;
+  int tgt_vt = 0;
+  int sysctl_fd = 0;
+
+  /* Turn off panic_on_oops. */
+  sysctl_fd = open(panic_on_oops_path, O_WRONLY);
+  if (sysctl_fd != -1) {
+    write(sysctl_fd, "0", 1);
+    close(sysctl_fd);
+  }
+
+  /* Turn off panic_on_warn. */
+  sysctl_fd = open(panic_on_warn_path, O_WRONLY);
+  if (sysctl_fd != -1) {
+    write(sysctl_fd, "0", 1);
+    close(sysctl_fd);
+  }
+
+  /* Determine which VT to switch to. Anything that isn't open yet will do. */
+  ret = ioctl(console_fd, VT_OPENQRY, &tgt_vt);
+  if (ret == -1) {
+    goto trykill;
+  }
+
+  /* Try to switch to it. */
+  ret = ioctl(console_fd, VT_ACTIVATE, tgt_vt);
+  if (ret == -1) {
+    goto trykill;
+  }
+
+  /* Wait for it to become active. */
+  ioctl(console_fd, VT_WAITACTIVE, tgt_vt);
+
+trykill:
+  return syscall(SYS_reboot, LINUX_REBOOT_MAGIC1, LINUX_REBOOT_MAGIC2,
+    LINUX_REBOOT_CMD_POWER_OFF, NULL);
 }
 
 int main(int argc, char **argv) {
@@ -405,6 +478,9 @@ int main(int argc, char **argv) {
   }
 
   for (arg_idx = 1; arg_idx < argc; arg_idx++) {
+    if (strncmp(argv[arg_idx], "--instant-shutdown", strlen("--instant-shutdown")) == 0) {
+      kill_system();
+    }
     if (strncmp(argv[arg_idx], "--devices=", strlen("--devices=")) == 0) {
       if (target_dev_name_raw_list != NULL) {
         print(fd_stderr, "--devices cannot be passed more than once!\n");
@@ -422,6 +498,12 @@ int main(int argc, char **argv) {
     }
   }
 
+  console_fd = open("/dev/console", O_RDWR);
+  if (console_fd == -1) {
+    print(fd_stderr, "Could not open /dev/console!\n");
+    exit(1);
+  }
+
   target_dev_list = safe_calloc(target_dev_list_len, sizeof(char *));
   panic_key_list = safe_calloc(panic_key_list_len, sizeof(int *));
   panic_key_active_list = safe_calloc(panic_key_list_len, sizeof(bool));