devshell: Support -S/--root-ssh-smbios

mantle/cmd/kola/devshell.go

@@ -65,7 +65,7 @@ func displayStatusMsg(ontty bool, status, msg string, termMaxWidth int) {
 	fmt.Printf("\033[2K\r%s", s)
 }
 
-func runDevShellSSH(ctx context.Context, builder *platform.QemuBuilder, conf *conf.Conf, sshCommand string) error {
+func runDevShellSSH(ctx context.Context, builder *platform.QemuBuilder, conf *conf.Conf, sshCommand string, rootSMBIOS bool) error {
 	ontty := term.IsTerminal(0)
 	if sshCommand == "" {
 		if !ontty {
@@ -95,8 +95,17 @@ func runDevShellSSH(ctx context.Context, builder *platform.QemuBuilder, conf *co
 		return err
 	}
 
-	conf.CopyKeys(keys)
-	builder.SetConfig(conf)
+	if rootSMBIOS {
+		var authorizedKeys string
+		for _, key := range keys {
+			authorizedKeys += key.String()
+			authorizedKeys += "\n"
+		}
+		builder.InjectSSHAuthorizedKeysViaSMBIOS(authorizedKeys)
+	} else {
+		conf.CopyKeys(keys)
+		builder.SetConfig(conf)
+	}
 
 	// errChan communicates errors from go routines
 	errChan := make(chan error)
@@ -105,8 +114,10 @@ func runDevShellSSH(ctx context.Context, builder *platform.QemuBuilder, conf *co
 	// stateChan reports in-instance state such as shutdown, reboot, etc.
 	stateChan := make(chan guestState)
 
-	if err = watchJournal(builder, conf, stateChan, errChan); err != nil {
-		return err
+	if conf != nil {
+		if err = watchJournal(builder, conf, stateChan, errChan); err != nil {
+			return err
+		}
 	}
 
 	// SerialPipe is the pipe output from the serial console.
@@ -186,9 +197,25 @@ func runDevShellSSH(ctx context.Context, builder *platform.QemuBuilder, conf *co
 
 	// Start the SSH client
 	sc := newSshClient(ip, agent.Socket, sshCommand)
+	if rootSMBIOS {
+		sc.user = "root"
+	}
 	sc.ontty = ontty
 	go sc.controlStartStop()
 
+	if rootSMBIOS {
+		go func() {
+			err := util.Retry(6, 5*time.Second, func() error {
+				return sc.check()
+			})
+			if err != nil {
+				errChan <- fmt.Errorf("failed to await ssh: %w", err)
+			} else {
+				stateChan <- guestStateOpenSshStarted
+			}
+		}()
+	}
+
 	ready := false
 	statusMsg := "STARTUP"
 	lastMsg := ""
@@ -213,7 +240,7 @@ func runDevShellSSH(ctx context.Context, builder *platform.QemuBuilder, conf *co
 				return fmt.Errorf("instance failed in initramfs; try rerunning with --devshell-console")
 			}
 			if err != nil {
-				fmt.Fprintf(os.Stderr, "errchan: %v", err)
+				return err
 			}
 
 		// monitor the instance state
@@ -472,6 +499,7 @@ type sshClient struct {
 	port        string
 	agent       string
 	cmd         string
+	user        string
 	ontty       bool
 	controlChan chan sshControlMessage
 	errChan     chan error
@@ -492,13 +520,39 @@ func newSshClient(host, agent, cmd string) *sshClient {
 		host:        host,
 		port:        port,
 		agent:       agent,
+		user:        "core",
 		controlChan: make(chan sshControlMessage),
 		errChan:     make(chan error),
 		// this could be a []string, but ssh sends it over as a string anyway, so meh...
 		cmd: cmd,
 	}
 }
 
+// baseArgs returns the basic arguments for the SSH command
+func (sc *sshClient) baseArgs() []string {
+	return []string{
+		"ssh", "-t",
+		"-o", "User=" + sc.user,
+		"-o", "StrictHostKeyChecking=no",
+		"-o", "CheckHostIP=no",
+		"-o", "IdentityAgent=" + sc.agent,
+		"-o", "PreferredAuthentications=publickey",
+		"-p", sc.port, sc.host,
+	}
+}
+
+// check queries whether we can successfully execute a command on the remote system
+func (sc *sshClient) check() error {
+	sshArgs := sc.baseArgs()
+	// Relatively fast timeout to ensure we don't get stuck by firewalling, etc.
+	sshArgs = append(sshArgs, "-o", "ConnectTimeout=5", "--", "true")
+	sshCmd := exec.Command(sshArgs[0], sshArgs[1:]...)
+	sshCmd.SysProcAttr = &syscall.SysProcAttr{
+		Pdeathsig: syscall.SIGTERM,
+	}
+	return sshCmd.Run()
+}
+
 // start starts the SSH session and returns the error over the errChan.
 // While the pure-go SSH client would be nicer, the golang SSH client
 // doesn't handle some keyboard keys well (arrows, home, end, etc).
@@ -517,15 +571,7 @@ func (sc *sshClient) start() {
 		time.Sleep(1 * time.Second)
 	}()
 
-	sshArgs := []string{
-		"ssh", "-t",
-		"-o", "User=core",
-		"-o", "StrictHostKeyChecking=no",
-		"-o", "CheckHostIP=no",
-		"-o", "IdentityAgent=" + sc.agent,
-		"-o", "PreferredAuthentications=publickey",
-		"-p", sc.port, sc.host,
-	}
+	sshArgs := sc.baseArgs()
 	if sc.cmd != "" {
 		sshArgs = append(sshArgs, "--", sc.cmd)
 	}

mantle/cmd/kola/qemuexec.go

@@ -58,6 +58,8 @@ var (
 	bindro            []string
 	bindrw            []string
 
+	rootSMBIOS bool
+
 	directIgnition            bool
 	forceConfigInjection      bool
 	propagateInitramfsFailure bool
@@ -101,6 +103,7 @@ func init() {
 	cmdQemuExec.Flags().BoolVar(&propagateInitramfsFailure, "propagate-initramfs-failure", false, "Error out if the system fails in the initramfs")
 	cmdQemuExec.Flags().StringVarP(&consoleFile, "console-to-file", "", "", "Filepath in which to save serial console logs")
 	cmdQemuExec.Flags().IntVarP(&additionalNics, "additional-nics", "", 0, "Number of additional NICs to add")
+	cmdQemuExec.Flags().BoolVarP(&rootSMBIOS, "root-ssh-smbios", "S", false, "Inject root login via systemd credentials (SMBIOS), not Ignition")
 	cmdQemuExec.Flags().StringVarP(&sshCommand, "ssh-command", "x", "", "Command to execute instead of spawning a shell")
 	cmdQemuExec.Flags().StringVarP(&netboot, "netboot", "", "", "Filepath to BOOTP program (e.g. PXELINUX/GRUB binary or iPXE script")
 	cmdQemuExec.Flags().StringVarP(&netbootDir, "netboot-dir", "", "", "Directory to serve over TFTP (default: BOOTP parent dir). If specified, --netboot is relative to this dir.")
@@ -216,10 +219,12 @@ func runQemuExec(cmd *cobra.Command, args []string) error {
 		if kola.QEMUOptions.DiskImage == "" && kolaPlatform == "qemu" {
 			return fmt.Errorf("No disk image provided")
 		}
-		ignitionFragments = append(ignitionFragments, "autologin")
+		if !rootSMBIOS {
+			ignitionFragments = append(ignitionFragments, "autologin")
+		}
 		cpuCountHost = true
 		usernet = true
-		if kola.Options.CosaWorkdir != "" {
+		if !rootSMBIOS && kola.Options.CosaWorkdir != "" {
 			// Conservatively bind readonly to avoid anything in the guest (stray tests, whatever)
 			// from destroying stuff
 			bindro = append(bindro, fmt.Sprintf("%s,/var/mnt/workdir", kola.Options.CosaWorkdir))
@@ -387,7 +392,12 @@ func runQemuExec(cmd *cobra.Command, args []string) error {
 	}
 
 	if devshell && !devshellConsole {
-		return runDevShellSSH(ctx, builder, config, sshCommand)
+		if rootSMBIOS {
+			if config != nil {
+				return fmt.Errorf("cannot perform Ignition configuration when using plain SMBIOS")
+			}
+		}
+		return runDevShellSSH(ctx, builder, config, sshCommand, rootSMBIOS)
 	}
 	if config != nil {
 		if directIgnition {

mantle/platform/qemu.go

@@ -32,6 +32,7 @@ import (
 	"bufio"
 	"bytes"
 	"context"
+	"encoding/base64"
 	"fmt"
 	"io"
 	"math/rand"
@@ -477,6 +478,10 @@ type QemuBuilder struct {
 	ignitionSet      bool
 	ignitionRendered bool
 
+	// sshAuthorizedKeysForRootViaSMBIOS is a public SSH key that will be rendered as a credential (https://systemd.io/CREDENTIALS)
+	// if set.
+	sshAuthorizedKeysForRootViaSMBIOS string
+
 	UsermodeNetworking        bool
 	usermodeNetworkingAddr    string
 	RestrictNetworking        bool
@@ -575,6 +580,28 @@ func (builder *QemuBuilder) renderIgnition() error {
 	return nil
 }
 
+// encodedSystemdTmpfilesForSSH implements the bit from systemd.io/CREDENTIALS
+// to inject a public SSH key into authorized_keys for the target user.
+func encodedSystemdTmpfilesForSSH(user, pubKey string) (string, error) {
+	pubKeyEnc := base64.StdEncoding.EncodeToString([]byte(pubKey))
+
+	userHomeDir := "/root"
+	if user != "root" {
+		userHomeDir = filepath.Join("/home", user)
+	}
+
+	tmpFileCmd := fmt.Sprintf("d %[1]s/.ssh 0700 %[2]s %[2]s -\nf+~ %[1]s/.ssh/authorized_keys 600 %[2]s %[2]s - %[3]s", userHomeDir, user, pubKeyEnc)
+
+	tmpFileCmdEnc := base64.StdEncoding.EncodeToString([]byte(tmpFileCmd))
+	return tmpFileCmdEnc, nil
+}
+
+// InjectSSHAuthorizedKeysViaSMBIOS writes the `authorized_keys` file for the `root` user
+// injected via SMBIOS and systemd credentials.
+func (builder *QemuBuilder) InjectSSHAuthorizedKeysViaSMBIOS(authorizedKeys string) {
+	builder.sshAuthorizedKeysForRootViaSMBIOS = authorizedKeys
+}
+
 // AddFd appends a file descriptor that will be passed to qemu,
 // returning a "/dev/fdset/<num>" argument that one can use with e.g.
 // -drive file=/dev/fdset/<num>.
@@ -1071,6 +1098,8 @@ func (disk *Disk) prepare(builder *QemuBuilder) error {
 			// on our own.
 			if strings.HasSuffix(backingFile, "qcow2") {
 				format = "qcow2"
+			} else if strings.HasSuffix(backingFile, "raw") {
+				format = "raw"
 			}
 		}
 		if format != "" {
@@ -1775,6 +1804,16 @@ func (builder *QemuBuilder) Exec() (*QemuInstance, error) {
 		}
 	}
 
+	if builder.sshAuthorizedKeysForRootViaSMBIOS != "" {
+		// Right now we hardcode root for simplicity
+		tmpFilesCmd, err := encodedSystemdTmpfilesForSSH("root", builder.sshAuthorizedKeysForRootViaSMBIOS)
+		if err != nil {
+			return nil, err
+		}
+		oemString := fmt.Sprintf("type=11,value=io.systemd.credential.binary:tmpfiles.extra=%s", tmpFilesCmd)
+		argv = append(argv, "-smbios", oemString)
+	}
+
 	// Handle Software TPM
 	if builder.Swtpm && builder.supportsSwtpm() {
 		err = builder.ensureTempdir()