Fix child processes termination at exit after LoginGraceTime expires

contrib/win32/win32compat/signal.c

@@ -310,11 +310,11 @@ wait_for_any_event(HANDLE* events, int num_events, DWORD milli_seconds)
 	return 0;
 }
 
-
 int
 sw_initialize()
 {
 	memset(&children, 0, sizeof(children));
+	atexit(terminate_all_child_processes);
 	sw_init_signal_handler_table();
 	if (sw_init_timer() != 0)
 		return -1;

contrib/win32/win32compat/signal_internal.h

@@ -26,6 +26,7 @@ int register_child(HANDLE child, DWORD pid);
 int sw_remove_child_at_index(DWORD index);
 int sw_child_to_zombie(DWORD index);
 void sw_cleanup_child_zombies();
+void terminate_all_child_processes();
 
 struct _timer_info {
 	HANDLE timer;

contrib/win32/win32compat/signal_sigchld.c

@@ -248,4 +248,22 @@ sw_cleanup_child_zombies()
 	int pid = 1;
 	while (pid > 0)
 		pid = waitpid(-1, NULL, WNOHANG);
-}
+}
+
+void
+terminate_all_child_processes()
+{
+	if (children.num_children > 0 && children.num_children <= MAX_CHILDREN) {
+		if (children.num_zombies >= 0 && children.num_children > children.num_zombies) {
+			DWORD live_children = children.num_children - children.num_zombies;
+			while (live_children--) {
+				DWORD pid = children.process_id[live_children];
+				HANDLE handle = children.handles[live_children];
+				TerminateProcess(handle, 0);
+				CloseHandle(handle);
+				debug4("Terminate child process %p pid %d", handle, pid);
+				++children.num_zombies;
+			}
+		}
+	}
+}

regress/pesterTests/SSHD.Tests.ps1

@@ -55,8 +55,8 @@ Describe "E2E scenarios for sshd" -Tags "CI" {
 
             # with a connection, there should be two additional session processes
             $sshdPidsCountWithConn | Should Be (2 + $sshdPidCountBefore)
-            # after LoginGraceTime expires, one of the session processes should exit
-            $sshdPidsCountAfter | Should Be (1 + $sshdPidCountBefore)
+            # after LoginGraceTime expires, all session processes should exit
+            $sshdPidsCountAfter | Should Be $sshdPidCountBefore
         }
 
         It "sshd pre-auth process is spawned under runtime generated virtual account" {

sshd-session.c

@@ -542,7 +542,10 @@ privsep_child_cmdline()
 static void
 grace_alarm_handler(int sig)
 {
-#ifndef WINDOWS
+#ifdef WINDOWS
+	/* We don't have to be signal-safe on Windows. Different native event mechanisms (APC). */
+	exit(EXIT_LOGIN_GRACE); /* Perform full C library cleanup and call atexit() registered functions. */
+#else
 	/*
 	 * Try to kill any processes that we have spawned, E.g. authorized
 	 * keys command helpers or privsep children.
@@ -560,8 +563,8 @@ grace_alarm_handler(int sig)
 		(void)sigaction(SIGTERM, &sa, NULL);
 		kill(0, SIGTERM);
 	}
+	_exit(EXIT_LOGIN_GRACE); /* We have to be signal-safe. */
 #endif /* WINDOWS */
-	_exit(EXIT_LOGIN_GRACE);
 }
 
 /* Destroy the host and server keys.  They will no longer be needed. */