Don't try to remove host keys when ~/.ssh/known_hosts doesn't exist

`ssh-keygen -R` will exit with a non-0 status and the hostagent would
abort. If the file doesn't exist, then there isn't anything to do.

Signed-off-by: Jan Dubois <[email protected]>

Author: jandubois

pkg/hostagent/hostagent.go

@@ -159,12 +159,9 @@ func (a *HostAgent) Run(ctx context.Context) error {
 	}
 	stBooting := stBase
 	a.emitEvent(ctx, hostagentapi.Event{Status: stBooting})
-	sshFixCmd := exec.Command("ssh-keygen",
-		"-R", fmt.Sprintf("[127.0.0.1]:%d", sshLocalPort),
-		"-R", fmt.Sprintf("[localhost]:%d", sshLocalPort),
-	)
-	if out, err := sshFixCmd.CombinedOutput(); err != nil {
-		return errors.Wrapf(err, "failed to run %v: %q", sshFixCmd.Args, string(out))
+	if err := sshutil.RemoveKnownHostEntries(sshLocalPort); err != nil {
+		a.l.WithError(err).Error("couldn't remove existing localhost host keys")
+		return err
 	}
 
 	go func() {

pkg/sshutil/sshutil.go

@@ -1,7 +1,9 @@
 package sshutil
 
 import (
+	"fmt"
 	"os"
+	"os/exec"
 	"path/filepath"
 	"strings"
 
@@ -46,6 +48,25 @@ func DefaultPubKeys() []PubKey {
 	return res
 }
 
+func RemoveKnownHostEntries(sshLocalPort int) error {
+	homeDir, err := os.UserHomeDir()
+	if err != nil {
+		return err
+	}
+	// `ssh-keygen -R` will return a non-0 status when ~/.ssh/known_hosts doesn't exist
+	if _, err := os.Stat(filepath.Join(homeDir, ".ssh/known_hosts")); errors.Is(err, os.ErrNotExist) {
+		return nil
+	}
+	sshFixCmd := exec.Command("ssh-keygen",
+		"-R", fmt.Sprintf("[127.0.0.1]:%d", sshLocalPort),
+		"-R", fmt.Sprintf("[localhost]:%d", sshLocalPort),
+	)
+	if out, err := sshFixCmd.CombinedOutput(); err != nil {
+		return errors.Wrapf(err, "failed to run %v: %q", sshFixCmd.Args, string(out))
+	}
+	return nil
+}
+
 func SSHArgs(instDir string) ([]string, error) {
 	controlSock := filepath.Join(instDir, filenames.SSHSock)
 	if len(controlSock) >= osutil.UnixPathMax {