Rework TPM workflow

In order to expose more values especific to the tpm part

Signed-off-by: Itxaka <itxaka@kairos.io>

pkg/lib/lock.go

@@ -13,11 +13,8 @@ import (
 	"time"
 )
 
-func CreateLuks(dev, password, version string, cryptsetupArgs ...string) error {
-	if version == "" {
-		version = "luks2"
-	}
-	args := []string{"luksFormat", "--type", version, "--iter-time", "5", "-q", dev}
+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)
@@ -48,87 +45,132 @@ func getRandomString(length int) string {
 // 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, version string, tpm bool) (string, error) {
+func Luksify(label string) (string, error) {
 	var pass string
-	if version == "" {
-		version = "luks1"
-	}
-	if version != "luks1" && version != "luks2" {
-		return "", fmt.Errorf("version must be luks1 or luks2")
-	}
 
 	part, b, err := FindPartition(label)
 	if err != nil {
 		return "", err
 	}
 
-	if tpm {
-		// 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)
-	} else {
-		pass, err = GetPassword(b)
-		if err != nil {
-			return "", err
-		}
+	pass, err = GetPassword(b)
+	if err != nil {
+		return "", err
 	}
 
 	part = fmt.Sprintf("/dev/%s", part)
-	devMapper := fmt.Sprintf("/dev/mapper/%s", b.Name)
+	partUUID := uuid.NewV5(uuid.NamespaceURL, label)
+	extraArgs := []string{"--uuid", partUUID.String()}
+
+	if err := CreateLuks(part, pass, extraArgs...); err != nil {
+		return "", err
+	}
+
+	err = formatLuks(part, label, pass)
+	if err != nil {
+		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) error {
+	part, _, 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)
+
+	part = fmt.Sprintf("/dev/%s", part)
 	partUUID := uuid.NewV5(uuid.NamespaceURL, label)
 
 	extraArgs := []string{"--uuid", partUUID.String()}
 
-	if err := CreateLuks(part, pass, version, extraArgs...); err != nil {
-		return "", err
-	}
-	if tpm {
-		// 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
-		// leave --tpm2-pcrs= to an empty value so it doesnt bind to a single measure
-		args := []string{"--tpm2-public-key=/run/systemd/tpm2-pcr-public-key.pem", "--tpm2-public-key-pcrs=11", "--tpm2-pcrs=", "--tpm2-signature=/run/systemd/tpm2-pcr-signature.json", "--tpm2-device-key=/run/systemd/tpm2-srk-public-key.tpm2b_public", part}
-		cmd := exec.Command("systemd-cryptenroll", args...)
-		cmd.Env = append(cmd.Env, fmt.Sprintf("PASSWORD=%s", pass)) // cannot pass it via stdin
-		cmd.Stdout = os.Stdout
-		cmd.Stderr = os.Stderr
-		err := cmd.Run()
-		if err != nil {
-			return "", err
-		}
+	if err := CreateLuks(part, pass, extraArgs...); err != nil {
+		return err
 	}
 
-	if err := LuksUnlock(part, b.Name, pass); err != nil {
-		return "", fmt.Errorf("unlock err: %w", err)
+	if len(publicKeyPcrs) == 0 {
+		publicKeyPcrs = []string{"11"}
 	}
 
+	// 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",
+		part}
+	cmd := exec.Command("systemd-cryptenroll", args...)
+	cmd.Env = append(cmd.Env, fmt.Sprintf("PASSWORD=%s", pass)) // cannot pass it via stdin
+	cmd.Stdout = os.Stdout
+	cmd.Stderr = os.Stderr
+	err = cmd.Run()
+	if err != nil {
+		return err
+	}
+
+	err = formatLuks(part, label, pass)
+	if err != nil {
+		return err
+	}
+
+	// Delete password slot from luks device
+	out, err := SH(fmt.Sprintf("systemd-cryptenroll --wipe-slot=password %s", part))
+	if err != nil {
+		return fmt.Errorf("err: %w, out: %s", err, out)
+	}
+	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, label, pass string) error {
+	devMapper := fmt.Sprintf("/dev/mapper/%s", device)
+
+	if err := LuksUnlock(device, device, pass); err != nil {
+		return fmt.Errorf("unlock err: %w", err)
+	}
 	if err := Waitdevice(devMapper, 10); err != nil {
-		return "", fmt.Errorf("waitdevice err: %w", err)
+		return fmt.Errorf("waitdevice err: %w", err)
 	}
 
-	cmd := fmt.Sprintf("mkfs.ext4 -L %s %s", label, devMapper)
-	out, err := SH(cmd)
+	cmdFormat := fmt.Sprintf("mkfs.ext4 -L %s %s", label, devMapper)
+	out, err := SH(cmdFormat)
 	if err != nil {
-		return "", fmt.Errorf("mkfs err: %w, out: %s", err, out)
+		return fmt.Errorf("mkfs err: %w, out: %s", err, out)
 	}
 
-	out, err = SH(fmt.Sprintf("cryptsetup close %s", b.Name))
+	out, err = SH(fmt.Sprintf("cryptsetup close %s", device))
 	if err != nil {
-		return "", fmt.Errorf("lock err: %w, out: %s", err, out)
+		return fmt.Errorf("lock err: %w, out: %s", err, out)
 	}
-
-	if tpm {
-		// Delete password slot from luks device
-		out, err := SH(fmt.Sprintf("systemd-cryptenroll --wipe-slot=password %s", part))
-		if err != nil {
-			return "", fmt.Errorf("err: %w, out: %s", err, out)
-		}
-	}
-
-	return configpkg.PartitionToString(b), nil
+	return nil
 }
 
 func FindPartition(label string) (string, *block.Partition, error) {