From cfc05e2e8fbbf36ae22544299257318f65162b27 Mon Sep 17 00:00:00 2001
From: Liam Hopkins <liamh@google.com>
Date: Wed, 14 Apr 2021 15:44:12 -0700
Subject: [PATCH] start sshd (#106)

---
 google_guest_agent/non_windows_accounts.go |  9 ++++
 google_guest_agent/oslogin.go              | 53 ++++++++++++----------
 2 files changed, 37 insertions(+), 25 deletions(-)

diff --git a/google_guest_agent/non_windows_accounts.go b/google_guest_agent/non_windows_accounts.go
index 04f87341..de21f72d 100644
--- a/google_guest_agent/non_windows_accounts.go
+++ b/google_guest_agent/non_windows_accounts.go
@@ -178,6 +178,15 @@ func (a *accountsMgr) set() error {
 	if err := writeGoogleUsersFile(); err != nil {
 		logger.Errorf("Error writing google_users file: %v.", err)
 	}
+
+	// Start SSHD if not started. We do this in agent instead of adding a
+	// Wants= directive, and here instead of instance setup, so that this
+	// can be disabled by the instance configs file.
+	for _, svc := range []string{"ssh", "sshd"} {
+		// Ignore output, it's just a best effort.
+		startService(svc, false)
+	}
+
 	return nil
 }
 
diff --git a/google_guest_agent/oslogin.go b/google_guest_agent/oslogin.go
index 18f09817..e6941ae9 100644
--- a/google_guest_agent/oslogin.go
+++ b/google_guest_agent/oslogin.go
@@ -103,12 +103,22 @@ func (o *osloginMgr) set() error {
 		logger.Errorf("Error updating group.conf: %v.", err)
 	}
 
-	for _, svc := range []string{"ssh", "sshd", "nscd", "unscd", "systemd-logind", "cron", "crond"} {
+	for _, svc := range []string{"nscd", "unscd", "systemd-logind", "cron", "crond"} {
 		if err := restartService(svc); err != nil {
 			logger.Errorf("Error restarting service: %v.", err)
 		}
 	}
 
+	// SSH should be explicitly started if not running.
+	for _, svc := range []string{"ssh", "sshd"} {
+		if err := startService(svc, true); err != nil {
+			logger.Errorf("Error restarting service: %v.", err)
+		} else {
+			// Stop on first matching, to avoid double restarting.
+			break
+		}
+	}
+
 	if enable {
 		if err := createOSLoginDirs(); err != nil {
 			logger.Errorf("Error creating OS Login directory: %v.", err)
@@ -340,35 +350,28 @@ func createOSLoginSudoersFile() error {
 	return sudoFile.Close()
 }
 
-// restartService tries to restart a service on linux-like systems. It attempts
-// to find and use the following mechanisms in order:
-// 1. The `systemctl` utility, if in a systemd environment.
-// 2. The `service` command, if present.
-// 3. A SysVinit script directly, if present.
-// Missing mechanisms and missing or disabled services are ignored.
+// restartService tries to restart a systemd service if it is already running.
 func restartService(servicename string) error {
-	init, err := os.Readlink("/sbin/init")
-	if err == nil && strings.Contains(init, "systemd") {
-		if systemctl, err := exec.LookPath("systemctl"); err == nil {
-			if err := runCmd(exec.Command(systemctl, "is-active", servicename+".service")); err == nil {
-				return runCmd(exec.Command(systemctl, "restart", servicename+".service"))
-			}
-			return nil
+	if systemctl, err := exec.LookPath("systemctl"); err == nil {
+		if err := runCmd(exec.Command(systemctl, "is-active", servicename+".service")); err == nil {
+			return runCmd(exec.Command(systemctl, "restart", servicename+".service"))
 		}
 	}
-	service, err := exec.LookPath("service")
-	if err == nil {
-		if err := runCmd(exec.Command(service, servicename, "status")); err == nil {
-			return runCmd(exec.Command(service, servicename, "restart"))
+
+	return nil
+}
+
+// startService tries to start a systemd service. If the service is already
+// running and restart is true, the service is restarted.
+func startService(servicename string, restart bool) error {
+	if systemctl, err := exec.LookPath("systemctl"); err == nil {
+		started := nil == runCmd(exec.Command(systemctl, "is-active", servicename+".service"))
+		if !started {
+			return runCmd(exec.Command(systemctl, "start", servicename+".service"))
 		}
-		return nil
-	}
-	initService := "/etc/init.d/" + servicename
-	if _, err := os.Stat(initService); err == nil {
-		if err := runCmd(exec.Command(initService, "status")); err == nil {
-			return runCmd(exec.Command(initService, "restart"))
+		if started && restart {
+			return runCmd(exec.Command(systemctl, "restart", servicename+".service"))
 		}
-		return nil
 	}
 
 	return nil