Set emergency login for core user with random password

This PR allow user to set the emergency login for core user with a
random generated password. It is helpful when user lost the ssh access
and use VMM to debug the issue which require password for `core` user.

Generated password is stored in `~/.crc/machine/crc/passwd` file which
user can consume in case of debugging. When user unset the
`enable-emergency-login` setting then password is locked for `core`
user.

```
$ crc config set enable-emergency-login true
$ crc config view
- enable-emergency-login                : true
[...]
$ crc start
[...]
INFO CRC VM is running
INFO Emergency login password for core user is stored to /home/prkumar/.crc/machines/crc/passwd
INFO Updating authorized keys...
[...]
```

cmd/crc/cmd/start.go

@@ -79,6 +79,8 @@ func runStart(ctx context.Context) (*types.StartResult, error) {
 		IngressHTTPPort:   config.Get(crcConfig.IngressHTTPPort).AsUInt(),
 		IngressHTTPSPort:  config.Get(crcConfig.IngressHTTPSPort).AsUInt(),
 		EnableSharedDirs:  config.Get(crcConfig.EnableSharedDirs).AsBool(),
+
+		EmergencyLogin: config.Get(crcConfig.EmergencyLogin).AsBool(),
 	}
 
 	client := newMachine()

pkg/crc/api/handlers.go

@@ -130,6 +130,7 @@ func getStartConfig(cfg crcConfig.Storage, args client.StartConfig) types.StartC
 		IngressHTTPSPort:  cfg.Get(crcConfig.IngressHTTPSPort).AsUInt(),
 		Preset:            crcConfig.GetPreset(cfg),
 		EnableSharedDirs:  cfg.Get(crcConfig.EnableSharedDirs).AsBool(),
+		EmergencyLogin:    cfg.Get(crcConfig.EmergencyLogin).AsBool(),
 	}
 }
 

pkg/crc/config/settings.go

@@ -34,6 +34,7 @@ const (
 	SharedDirPassword       = "shared-dir-password" // #nosec G101
 	IngressHTTPPort         = "ingress-http-port"
 	IngressHTTPSPort        = "ingress-https-port"
+	EmergencyLogin          = "enable-emergency-login"
 )
 
 func RegisterSettings(cfg *Config) {
@@ -88,6 +89,8 @@ func RegisterSettings(cfg *Config) {
 		"Disable update check (true/false, default: false)")
 	cfg.AddSetting(ExperimentalFeatures, false, ValidateBool, SuccessfullyApplied,
 		"Enable experimental features (true/false, default: false)")
+	cfg.AddSetting(EmergencyLogin, false, ValidateBool, SuccessfullyApplied,
+		"Enable emergency login for 'core' user. Password is randomly generated. (true/false, default: false)")
 
 	// Shared directories configs
 	if runtime.GOOS == "windows" {

pkg/crc/constants/constants.go

@@ -110,6 +110,7 @@ var (
 	MachineInstanceDir = filepath.Join(MachineBaseDir, "machines")
 	DaemonSocketPath   = filepath.Join(CrcBaseDir, "crc.sock")
 	KubeconfigFilePath = filepath.Join(MachineInstanceDir, DefaultName, "kubeconfig")
+	PasswdFilePath     = filepath.Join(MachineInstanceDir, DefaultName, "passwd")
 )
 
 func GetDefaultBundlePath(preset crcpreset.Preset) string {

pkg/crc/machine/start.go

@@ -6,6 +6,7 @@ import (
 	"crypto/x509"
 	"encoding/json"
 	"fmt"
+	"math/rand"
 	"os"
 	"path/filepath"
 	"strconv"
@@ -32,6 +33,7 @@ import (
 	"github.com/crc-org/crc/pkg/crc/telemetry"
 	crctls "github.com/crc-org/crc/pkg/crc/tls"
 	"github.com/crc-org/crc/pkg/libmachine/host"
+	crcos "github.com/crc-org/crc/pkg/os"
 	"github.com/crc-org/machine/libmachine/drivers"
 	libmachinestate "github.com/crc-org/machine/libmachine/state"
 	"github.com/docker/go-units"
@@ -417,6 +419,16 @@ func (client *client) Start(ctx context.Context, startConfig types.StartConfig)
 	}
 	logging.Info("CRC VM is running")
 
+	if startConfig.EmergencyLogin {
+		if err := enableEmergencyLogin(sshRunner); err != nil {
+			return nil, errors.Wrap(err, "Error enabling emergency login")
+		}
+	} else {
+		if err := disableEmergencyLogin(sshRunner); err != nil {
+			return nil, errors.Wrap(err, "Error deleting the password for core user")
+		}
+	}
+
 	// Post VM start immediately update SSH key and copy kubeconfig to instance
 	// dir and VM
 	if err := updateSSHKeyPair(sshRunner); err != nil {
@@ -784,6 +796,29 @@ func addNameServerToInstance(sshRunner *crcssh.Runner, ns string) error {
 	return nil
 }
 
+func enableEmergencyLogin(sshRunner *crcssh.Runner) error {
+	if crcos.FileExists(constants.PasswdFilePath) {
+		return nil
+	}
+	charset := "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"
+	b := make([]byte, 8)
+	for i := range b {
+		b[i] = charset[rand.Intn(len(charset))] //nolint
+	}
+	if err := os.WriteFile(constants.PasswdFilePath, b, 0600); err != nil {
+		return err
+	}
+	logging.Infof("Emergency login password for core user is stored to %s", constants.PasswdFilePath)
+	_, _, err := sshRunner.Run(fmt.Sprintf("sudo passwd core --unlock && echo %s | sudo passwd core --stdin", b))
+	return err
+}
+
+func disableEmergencyLogin(sshRunner *crcssh.Runner) error {
+	defer os.Remove(constants.PasswdFilePath)
+	_, _, err := sshRunner.RunPrivileged("disable core user password", "passwd", "--lock", "core")
+	return err
+}
+
 func updateSSHKeyPair(sshRunner *crcssh.Runner) error {
 	// Read generated public key
 	publicKey, err := os.ReadFile(constants.GetPublicKeyPath())

pkg/crc/machine/types/types.go

@@ -37,6 +37,9 @@ type StartConfig struct {
 	// Ports to access openshift routes
 	IngressHTTPPort  uint
 	IngressHTTPSPort uint
+
+	// Enable emergency login
+	EmergencyLogin bool
 }
 
 type ClusterConfig struct {