New signal: SIGUSR1.

This signal is now sent from the main program to the saver to reset possible
idle timers in the savers, without intending to restart the saver.

This is part of the effort to make the auth child protocol more flexible and to
properly run auth on top of the saver as a window.

README.md

@@ -408,6 +408,12 @@ location: `/usr/local/libexec/xsecurelock/helpers`).
 *   Output: it may draw on or create windows below `$XSCREENSAVER_WINDOW`.
 *   Exit condition: the saver child will receive SIGTERM when the user wishes to
     unlock the screen. It should exit promptly.
+*   Reset condition: the saver child will receive SIGUSR1 when the auth dialog
+    is closed. It then shall make sure to blank the screen after a timeout.
+    One way to implent this in shell script based implementations is to simply
+    ignore SIGUSR1 first, start the actual saver in a child processes, and to
+    finally exec `saver_blank`. Not implementing this will cause the entire
+    saver to reset on this condition.
 
 # Security Design
 

auth_child.c

@@ -16,9 +16,10 @@ limitations under the License.
 
 #include "auth_child.h"
 
-#include <stdlib.h>  // for NULL, EXIT_FAILURE
-#include <string.h>  // for strlen
-#include <unistd.h>  // for close, _exit, dup2, execl, fork, pipe
+#include <stdlib.h>      // for NULL, EXIT_FAILURE
+#include <string.h>      // for strlen
+#include <sys/signal.h>  // for SIGTERM
+#include <unistd.h>      // for close, _exit, dup2, execl, fork, pipe
 
 #include "env_settings.h"      // for GetIntSetting
 #include "logging.h"           // for LogErrno, Log
@@ -31,11 +32,11 @@ static pid_t auth_child_pid = 0;
 //! If auth_child_pid != 0, the FD which connects to stdin of the auth child.
 static int auth_child_fd = 0;
 
-void KillAuthChildSigHandler(void) {
+void KillAuthChildSigHandler(int signo) {
   // This is a signal handler, so we're not going to make this too complicated.
   // Just kill it.
   if (auth_child_pid != 0) {
-    KillPgrp(auth_child_pid);
+    KillPgrp(auth_child_pid, signo);
   }
 }
 
@@ -101,7 +102,7 @@ int WatchAuthChild(Window w, const char *executable, int force_auth,
     pid_t pgrpid = auth_child_pid;
     if (WaitPgrp("auth", &auth_child_pid, 0, 0, &status)) {
       // Try taking its process group with it. Should normally not do anything.
-      KillPgrp(pgrpid);
+      KillPgrp(pgrpid, SIGTERM);
 
       // Clean up.
       close(auth_child_fd);

auth_child.h

@@ -23,7 +23,7 @@ limitations under the License.
  *
  * This can be used from a signal handler.
  */
-void KillAuthChildSigHandler(void);
+void KillAuthChildSigHandler(int signo);
 
 /*! \brief Checks whether an auth child should be running.
  *

helpers/saver_blank

@@ -18,6 +18,12 @@
 : ${XSECURELOCK_BLANK_TIMEOUT:=600}     # Seconds; -1 disables blanking.
 : ${XSECURELOCK_BLANK_DPMS_STATE:=off}  # Values: standby, suspend, off, on.
 
+# In case of SIGUSR1, we want to restart the timer, but NOT kill the screen
+# saver. How are we gonna do this? By having the other script ignore SIGUSR1
+# (don't restart screen saver) before spawning its subprocesses, but having
+# this script restart itself on SIGUSR1.
+trap 'exec "$0"' USR1
+
 if [ "$XSECURELOCK_BLANK_TIMEOUT" -ge 0 ]; then
   # Wait 60 seconds before actually turning the screen off. Till then we have a
   # black background managed by xsecurelock's main process anyway.

helpers/saver_mplayer.in

@@ -16,6 +16,10 @@
 
 : ${XSECURELOCK_LIST_VIDEOS_COMMAND:=find ~/Videos -type f}
 
+# On SIGUSR1, we simply keep going, as this signal should only restart
+# the sleep timer.
+trap '' USR1
+
 sh -c "$XSECURELOCK_LIST_VIDEOS_COMMAND" | shuf | head -n 256 |\
 @path_to_mplayer@ \
   -noconsolecontrols \

helpers/saver_mpv.in

@@ -16,6 +16,10 @@
 
 : ${XSECURELOCK_LIST_VIDEOS_COMMAND:=find ~/Videos -type f}
 
+# On SIGUSR1, we simply keep going, as this signal should only restart
+# the sleep timer.
+trap '' USR1
+
 sh -c "$XSECURELOCK_LIST_VIDEOS_COMMAND" | shuf | head -n 256 |\
 @path_to_mpv@ \
   --no-input-terminal \

helpers/saver_multiplex.c

@@ -30,9 +30,13 @@ limitations under the License.
 #include "../xscreensaver_api.h"  // for ReadWindowID
 #include "monitors.h"             // for IsMonitorChangeEvent, Monitor, Sele...
 
+static void HandleSIGUSR1(int signo) {
+  KillAllSaverChildrenSigHandler(signo);  // Dirty, but quick.
+}
+
 static void HandleSIGTERM(int signo) {
-  KillAllSaverChildrenSigHandler();  // Dirty, but quick.
-  raise(signo);                      // Destroys windows we created anyway.
+  KillAllSaverChildrenSigHandler(signo);  // Dirty, but quick.
+  raise(signo);                           // Destroys windows we created anyway.
 }
 
 static void HandleSIGCHLD(int unused_signo) {
@@ -126,6 +130,10 @@ int main(int argc, char** argv) {
   if (sigaction(SIGCHLD, &sa, NULL) != 0) {
     LogErrno("sigaction(SIGCHLD)");
   }
+  sa.sa_handler = HandleSIGUSR1;  // To kill children.
+  if (sigaction(SIGUSR1, &sa, NULL) != 0) {
+    LogErrno("sigaction(SIGUSR1)");
+  }
   sa.sa_flags = SA_RESETHAND;     // It re-raises to suicide.
   sa.sa_handler = HandleSIGTERM;  // To kill children.
   if (sigaction(SIGTERM, &sa, NULL) != 0) {

helpers/saver_xscreensaver.in

@@ -16,6 +16,10 @@
 
 : ${XSECURELOCK_XSCREENSAVER_PATH:=@path_to_xscreensaver@}
 
+# On SIGUSR1, we simply keep going, as this signal should only restart
+# the sleep timer.
+trap '' USR1
+
 TAB='	'
 
 # Note: the following logic is somewhat derived from parse_screenhack in

helpers/until_nonidle.c

@@ -64,7 +64,7 @@ pid_t childpid = 0;
 
 static void HandleSIGTERM(int signo) {
   if (childpid != 0) {
-    KillPgrp(childpid);  // Dirty, but quick.
+    KillPgrp(childpid, signo);  // Dirty, but quick.
   }
   raise(signo);
 }
@@ -223,11 +223,11 @@ int main(int argc, char **argv) {
         still_idle && (active_ms <= dim_time_ms + wait_time_ms);
 
     if (!should_be_running) {
-      KillPgrp(childpid);
+      KillPgrp(childpid, SIGTERM);
     }
     int status;
     WaitPgrp("idle", &childpid, !should_be_running, !should_be_running,
-                 &status);
+             &status);
   }
 
   // This is the point where we can exit.

main.c

@@ -140,8 +140,8 @@ int debug_window_info = 0;
 pid_t notify_command_pid = 0;
 
 static void HandleSIGTERM(int signo) {
-  KillAllSaverChildrenSigHandler();  // Dirty, but quick.
-  KillAuthChildSigHandler();         // More dirty.
+  KillAllSaverChildrenSigHandler(signo);  // Dirty, but quick.
+  KillAuthChildSigHandler(signo);         // More dirty.
   explicit_bzero(&priv, sizeof(priv));
   raise(signo);
 }
@@ -200,11 +200,9 @@ int WatchChildren(Display *dpy, Window auth_win, Window saver_win,
 
     // If we wanted auth, but it's not running, auth just terminated. Unmap the
     // auth window and poke the screensaver so that it can reset any timeouts.
-    // TODO(divVerent): Implement a nicer way to poke if supported (say,
-    // SIGUSR1).
     if (!auth_running) {
       XUnmapWindow(dpy, auth_win);
-      WatchSaverChild(dpy, saver_win, 0, saver_executable, 0);
+      KillAllSaverChildrenSigHandler(SIGUSR1);
     }
   }
 

saver_child.c

@@ -16,9 +16,10 @@ limitations under the License.
 
 #include "saver_child.h"
 
-#include <signal.h>  // for sigemptyset, sigprocmask, SIG_SETMASK
-#include <stdlib.h>  // for NULL, EXIT_FAILURE
-#include <unistd.h>  // for pid_t, _exit, execl, fork, setsid, sleep
+#include <signal.h>      // for sigemptyset, sigprocmask, SIG_SETMASK
+#include <stdlib.h>      // for NULL, EXIT_FAILURE
+#include <sys/signal.h>  // for SIGTERM
+#include <unistd.h>      // for pid_t, _exit, execl, fork, setsid, sleep
 
 #include "logging.h"           // for LogErrno, Log
 #include "wait_pgrp.h"         // for KillPgrp, WaitPgrp
@@ -27,13 +28,13 @@ limitations under the License.
 //! The PIDs of currently running saver children, or 0 if not running.
 static pid_t saver_child_pid[MAX_SAVERS] = {0};
 
-void KillAllSaverChildrenSigHandler(void) {
+void KillAllSaverChildrenSigHandler(int signo) {
   // This is a signal handler, so we're not going to make this too
   // complicated. Just kill 'em all.
   int i;
   for (i = 0; i < MAX_SAVERS; ++i) {
     if (saver_child_pid[i] != 0) {
-      KillPgrp(saver_child_pid[i]);
+      KillPgrp(saver_child_pid[i], signo);
     }
   }
 }
@@ -47,7 +48,7 @@ void WatchSaverChild(Display* dpy, Window w, int index, const char* executable,
 
   if (saver_child_pid[index] != 0) {
     if (!should_be_running) {
-      KillPgrp(saver_child_pid[index]);
+      KillPgrp(saver_child_pid[index], SIGTERM);
     }
 
     int status;
@@ -57,7 +58,7 @@ void WatchSaverChild(Display* dpy, Window w, int index, const char* executable,
       if (should_be_running) {
         // Try taking its process group with it. Should normally not do
         // anything.
-        KillPgrp(pgrpid);
+        KillPgrp(pgrpid, SIGTERM);
       }
 
       // Now is the time to remove anything the child may have displayed.

saver_child.h

@@ -26,7 +26,7 @@ limitations under the License.
  *
  * This can be used from a signal handler.
  */
-void KillAllSaverChildrenSigHandler(void);
+void KillAllSaverChildrenSigHandler(int signo);
 
 /*! \brief Starts or stops the screen saver child process.
  *

wait_pgrp.c

@@ -25,12 +25,12 @@ limitations under the License.
 
 #include "logging.h"  // for Log, LogErrno
 
-int KillPgrp(pid_t pid) {
-  int ret = kill(-pid, SIGTERM);
+int KillPgrp(pid_t pid, int signo) {
+  int ret = kill(-pid, signo);
   if (ret < 0 && errno == ESRCH) {
     // Might mean the process is not a process group leader - but might also
     // mean that the process is already dead. Try killing just the process then.
-    ret = kill(pid, SIGTERM);
+    ret = kill(pid, signo);
   }
   return ret;
 }
@@ -39,8 +39,9 @@ int WaitPgrp(const char *name, pid_t *pid, int do_block, int already_killed,
              int *exit_status) {
   sigset_t oldset, set;
   sigemptyset(&set);
-  // We're blocking the signal we may have a forwarding handler for as their
+  // We're blocking the signals we may have forwarding handlers for as their
   // handling reads the pid variable we are changing here.
+  sigaddset(&set, SIGUSR1);
   sigaddset(&set, SIGTERM);
   // If we want to wait for a process to die, we must also block SIGCHLD
   // so we can reliably wait for another child in case waitpid returned 0.

wait_pgrp.h

@@ -23,7 +23,7 @@ limitations under the License.
 #define WAIT_ALREADY_DEAD INT_MIN
 #define WAIT_NONPOSITIVE_SIGNAL (INT_MIN + 1)
 
-int KillPgrp(pid_t pid);
+int KillPgrp(pid_t pid, int signo);
 int WaitPgrp(const char *name, pid_t *pid, int do_block, int already_killed,
              int *exit_status);