kcrypt/pkg/lib/lock.go

package lib

import (
	"bytes"
	"fmt"
	"math/rand"
	"os"
	"os/exec"
	"strings"
	"syscall"
	"time"

	"github.com/gofrs/uuid"
	"github.com/jaypipes/ghw"
	"github.com/jaypipes/ghw/pkg/block"
	configpkg "github.com/kairos-io/kcrypt/pkg/config"
	"github.com/rs/zerolog"
)

func CreateLuks(dev, password string, cryptsetupArgs ...string) error {
	args := []string{"luksFormat", "--type", "luks2", "--iter-time", "5", "-q", dev}
	args = append(args, cryptsetupArgs...)
	cmd := exec.Command("cryptsetup", args...)
	cmd.Stdin = strings.NewReader(password)
	cmd.Stdout = os.Stdout
	cmd.Stderr = os.Stderr
	err := cmd.Run()
	if err != nil {
		return err
	}

	return nil
}

var seededRand = rand.New(rand.NewSource(time.Now().UnixNano()))

func getRandomString(length int) string {
	const charset = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"
	b := make([]byte, length)
	for i := range b {
		b[i] = charset[seededRand.Intn(len(charset))]
	}
	return string(b)
}

// Luksify Take a part label, and recreates it with LUKS. IT OVERWRITES DATA!
// On success, it returns a machine parseable string with the partition information
// (label:name:uuid) so that it can be stored by the caller for later use.
// This is because the label of the encrypted partition is not accessible unless
// the partition is decrypted first and the uuid changed after encryption so
// any stored information needs to be updated (by the caller).
func Luksify(label string, logger zerolog.Logger, argsCreate ...string) (string, error) {
	var pass string

	// Make sure ghw will see all partitions correctly.
	// older versions don't have --type=all. Try the simpler version then.
	out, err := SH("udevadm trigger --type=all || udevadm trigger")
	if err != nil {
		return "", fmt.Errorf("udevadm trigger failed: %w, out: %s", err, out)
	}
	syscall.Sync()

	part, b, err := FindPartition(label)
	if err != nil {
		logger.Err(err).Msg("find partition")
		return "", err
	}

	pass, err = GetPassword(b)
	if err != nil {
		logger.Err(err).Msg("get password")
		return "", err
	}

	mapper := fmt.Sprintf("/dev/mapper/%s", b.Name)
	device := fmt.Sprintf("/dev/%s", part)

	extraArgs := []string{"--uuid", uuid.NewV5(uuid.NamespaceURL, label).String()}
	extraArgs = append(extraArgs, "--label", label)
	extraArgs = append(extraArgs, argsCreate...)

	if err := CreateLuks(device, pass, extraArgs...); err != nil {
		logger.Err(err).Msg("create luks")
		return "", err
	}

	err = formatLuks(device, b.Name, mapper, label, pass, logger)
	if err != nil {
		logger.Err(err).Msg("format luks")
		return "", err
	}

	return configpkg.PartitionToString(b), nil
}

// LuksifyMeasurements takes a label and a list if public-keys and pcrs to bind and uses the measurements
// in the current node to encrypt the partition with those and bind those to the given pcrs
// this expects systemd 255 as it needs the SRK public key that systemd extracts
// Sets a random password, enrolls the policy, unlocks and formats the partition, closes it and tfinally removes the random password from it
// Note that there is a diff between the publicKeyPcrs and normal Pcrs
// The former links to a policy type that allows anything signed by that policy to unlcok the partitions so its
// really useful for binding to PCR11 which is the UKI measurements in order to be able to upgrade the system and still be able
// to unlock the partitions.
// The later binds to a SINGLE measurement, so if that changes, it will not unlock anything.
// This is useful for things like PCR7 which measures the secureboot state and certificates if you dont expect those to change during
// the whole lifetime of a machine
// It can also be used to bind to things like the firmware code or efi drivers that we dont expect to change
// default for publicKeyPcrs is 11
// default for pcrs is nothing, so it doesn't bind as we want to expand things like DBX and be able to blacklist certs and such
func LuksifyMeasurements(label string, publicKeyPcrs []string, pcrs []string, logger zerolog.Logger, argsCreate ...string) error {
	// Make sure ghw will see all partitions correctly.
	// older versions don't have --type=all. Try the simpler version then.
	out, err := SH("udevadm trigger --type=all || udevadm trigger")
	if err != nil {
		return fmt.Errorf("udevadm trigger failed: %w, out: %s", err, out)
	}
	syscall.Sync()

	part, b, err := FindPartition(label)
	if err != nil {
		return err
	}

	// On TPM locking we generate a random password that will only be used here then discarded.
	// only unlocking method will be PCR values
	pass := getRandomString(32)
	mapper := fmt.Sprintf("/dev/mapper/%s", b.Name)
	device := fmt.Sprintf("/dev/%s", part)

	extraArgs := []string{"--uuid", uuid.NewV5(uuid.NamespaceURL, label).String()}
	extraArgs = append(extraArgs, argsCreate...)

	if err := CreateLuks(device, pass, extraArgs...); err != nil {
		return err
	}

	if len(publicKeyPcrs) == 0 {
		publicKeyPcrs = []string{"11"}
	}

	syscall.Sync()

	// Enroll PCR policy as a keyslot
	// We pass the current signature of the booted system to confirm that we would be able to unlock with the current booted system
	// That checks the policy against the signatures and fails if a UKI with those signatures wont be able to unlock the device
	// Files are generated by systemd automatically and are extracted from the UKI binary directly
	// public pem cert -> .pcrpkey section fo the elf file
	// signatures -> .pcrsig section of the elf file
	args := []string{
		"--tpm2-public-key=/run/systemd/tpm2-pcr-public-key.pem",
		fmt.Sprintf("--tpm2-public-key-pcrs=%s", strings.Join(publicKeyPcrs, "+")),
		fmt.Sprintf("--tpm2-pcrs=%s", strings.Join(pcrs, "+")),
		"--tpm2-signature=/run/systemd/tpm2-pcr-signature.json",
		"--tpm2-device-key=/run/systemd/tpm2-srk-public-key.tpm2b_public",
		device}
	logger.Debug().Str("args", strings.Join(args, " ")).Msg("running command")
	cmd := exec.Command("systemd-cryptenroll", args...)
	cmd.Env = append(cmd.Env, fmt.Sprintf("PASSWORD=%s", pass), "SYSTEMD_LOG_LEVEL=debug") // cannot pass it via stdin
	// Store the output into a buffer to log it in case we need it
	// debug output goes to stderr for some reason?
	stdOut := bytes.Buffer{}
	cmd.Stdout = &stdOut
	cmd.Stderr = &stdOut
	err = cmd.Run()
	if err != nil {
		logger.Debug().Str("output", stdOut.String()).Msg("debug from cryptenroll")
		logger.Err(err).Msg("Enrolling measurements")
		return err
	}

	logger.Debug().Str("output", stdOut.String()).Msg("debug from cryptenroll")

	err = formatLuks(device, b.Name, mapper, label, pass, logger)
	if err != nil {
		logger.Err(err).Msg("format luks")
		return err
	}

	// Delete password slot from luks device
	out, err = SH(fmt.Sprintf("systemd-cryptenroll --wipe-slot=password %s", device))
	if err != nil {
		logger.Err(err).Str("out", out).Msg("Removing password")
		return err
	}
	return nil
}

// format luks will unlock the device, wait for it and then format it
// device is the actual /dev/X luks device
// label is the label we will set to the formatted partition
// password is the pass to unlock the device to be able to format the underlying mapper
func formatLuks(device, name, mapper, label, pass string, logger zerolog.Logger) error {
	l := logger.With().Str("device", device).Str("name", name).Str("mapper", mapper).Logger()
	l.Debug().Msg("unlock")
	if err := LuksUnlock(device, name, pass); err != nil {
		return fmt.Errorf("unlock err: %w", err)
	}

	l.Debug().Msg("wait device")
	if err := Waitdevice(mapper, 10); err != nil {
		return fmt.Errorf("waitdevice err: %w", err)
	}

	l.Debug().Msg("format")
	cmdFormat := fmt.Sprintf("mkfs.ext4 -L %s %s", label, mapper)
	out, err := SH(cmdFormat)
	if err != nil {
		return fmt.Errorf("mkfs err: %w, out: %s", err, out)
	}

	// Refresh needs the password as its doing actions on the device directly
	l.Debug().Msg("discards")
	cmd := exec.Command("cryptsetup", "refresh", "--persistent", "--allow-discards", mapper)
	cmd.Stdin = strings.NewReader(pass)
	output, err := cmd.CombinedOutput()

	if err != nil {
		return fmt.Errorf("refresh err: %w, out: %s", err, string(output))
	}

	l.Debug().Msg("close")
	out, err = SH(fmt.Sprintf("cryptsetup close %s", mapper))
	if err != nil {
		return fmt.Errorf("lock err: %w, out: %s", err, out)
	}

	return nil
}

func FindPartition(label string) (string, *block.Partition, error) {
	b, err := ghw.Block()
	if err == nil {
		for _, disk := range b.Disks {
			for _, p := range disk.Partitions {
				if p.FilesystemLabel == label {
					return p.Name, p, nil
				}

			}
		}
	} else {
		return "", nil, err
	}

	return "", nil, fmt.Errorf("not found label %s", label)
}