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// -*- Mode: Go; indent-tabs-mode: t -*-
//go:build !nosecboot
/*
* Copyright (C) 2021 Canonical Ltd
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 3 as
* published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
*/
package secboot
import (
"bytes"
"crypto/rand"
"errors"
"fmt"
"io"
"os"
"path/filepath"
"strings"
"github.com/canonical/go-tpm2"
"github.com/canonical/go-tpm2/mu"
sb "github.com/snapcore/secboot"
sb_efi "github.com/snapcore/secboot/efi"
sb_tpm2 "github.com/snapcore/secboot/tpm2"
"golang.org/x/xerrors"
"github.com/snapcore/snapd/asserts"
"github.com/snapcore/snapd/bootloader"
"github.com/snapcore/snapd/bootloader/efi"
"github.com/snapcore/snapd/gadget/device"
"github.com/snapcore/snapd/logger"
"github.com/snapcore/snapd/osutil"
"github.com/snapcore/snapd/randutil"
"github.com/snapcore/snapd/snap/snapfile"
)
const (
keyringPrefix = "ubuntu-fde"
)
var (
sbConnectToDefaultTPM = sb_tpm2.ConnectToDefaultTPM
sbMeasureSnapSystemEpochToTPM = sb_tpm2.MeasureSnapSystemEpochToTPM
sbMeasureSnapModelToTPM = sb_tpm2.MeasureSnapModelToTPM
sbBlockPCRProtectionPolicies = sb_tpm2.BlockPCRProtectionPolicies
sbefiAddPCRProfile = sb_efi.AddPCRProfile
sbefiAddSystemdStubProfile = sb_efi.AddSystemdStubProfile
sbAddSnapModelProfile = sb_tpm2.AddSnapModelProfile
sbUpdateKeyPCRProtectionPolicyMultiple = sb_tpm2.UpdateKeyPCRProtectionPolicyMultiple
sbSealedKeyObjectRevokeOldPCRProtectionPolicies = (*sb_tpm2.SealedKeyObject).RevokeOldPCRProtectionPolicies
sbNewFileKeyDataReader = sb.NewFileKeyDataReader
sbReadKeyData = sb.ReadKeyData
sbReadSealedKeyObjectFromFile = sb_tpm2.ReadSealedKeyObjectFromFile
sbNewTPMProtectedKey = sb_tpm2.NewTPMProtectedKey
sbNewTPMPassphraseProtectedKey = sb_tpm2.NewTPMPassphraseProtectedKey
sbNewKeyDataFromSealedKeyObjectFile = sb_tpm2.NewKeyDataFromSealedKeyObjectFile
randutilRandomKernelUUID = randutil.RandomKernelUUID
isTPMEnabled = (*sb_tpm2.Connection).IsEnabled
lockoutAuthSet = (*sb_tpm2.Connection).LockoutAuthSet
sbTPMEnsureProvisioned = (*sb_tpm2.Connection).EnsureProvisioned
sbTPMEnsureProvisionedWithCustomSRK = (*sb_tpm2.Connection).EnsureProvisionedWithCustomSRK
tpmReleaseResources = tpmReleaseResourcesImpl
tpmGetCapabilityHandles = (*sb_tpm2.Connection).GetCapabilityHandles
sbTPMDictionaryAttackLockReset = (*sb_tpm2.Connection).DictionaryAttackLockReset
sbUpdateKeyDataPCRProtectionPolicy = sb_tpm2.UpdateKeyDataPCRProtectionPolicy
// check whether the interfaces match
_ (sb.SnapModel) = ModelForSealing(nil)
)
func CheckTPMKeySealingSupported(mode TPMProvisionMode) error {
logger.Noticef("checking if secure boot is enabled...")
if err := checkSecureBootEnabled(); err != nil {
logger.Noticef("secure boot not enabled: %v", err)
return err
}
logger.Noticef("secure boot is enabled")
logger.Noticef("checking if TPM device is available...")
tpm, err := sbConnectToDefaultTPM()
if err != nil {
err = fmt.Errorf("cannot connect to TPM device: %v", err)
logger.Noticef("%v", err)
return err
}
defer tpm.Close()
if !isTPMEnabled(tpm) {
logger.Noticef("TPM device detected but not enabled")
return fmt.Errorf("TPM device is not enabled")
}
if mode == TPMProvisionFull {
if lockoutAuthSet(tpm) {
logger.Noticef("TPM in lockout mode")
return sb_tpm2.ErrTPMLockout
}
}
logger.Noticef("TPM device detected and enabled")
return nil
}
func checkSecureBootEnabled() error {
// 8be4df61-93ca-11d2-aa0d-00e098032b8c is the EFI Global Variable vendor GUID
b, _, err := efi.ReadVarBytes("SecureBoot-8be4df61-93ca-11d2-aa0d-00e098032b8c")
if err != nil {
if err == efi.ErrNoEFISystem {
return err
}
return fmt.Errorf("cannot read secure boot variable: %v", err)
}
if len(b) < 1 {
return errors.New("secure boot variable does not exist")
}
if b[0] != 1 {
return errors.New("secure boot is disabled")
}
return nil
}
// initramfsPCR is the TPM PCR that we reserve for the EFI image and use
// for measurement from the initramfs.
const initramfsPCR = 12
func insecureConnectToTPM() (*sb_tpm2.Connection, error) {
return sbConnectToDefaultTPM()
}
func measureWhenPossible(whatHow func(tpm *sb_tpm2.Connection) error) error {
// the model is ready, we're good to try measuring it now
tpm, err := insecureConnectToTPM()
if err != nil {
if xerrors.Is(err, sb_tpm2.ErrNoTPM2Device) {
return nil
}
return fmt.Errorf("cannot open TPM connection: %v", err)
}
defer tpm.Close()
if !isTPMEnabled(tpm) {
return nil
}
return whatHow(tpm)
}
// MeasureSnapSystemEpochWhenPossible measures the snap system epoch only if the
// TPM device is available. If there's no TPM device success is returned.
func MeasureSnapSystemEpochWhenPossible() error {
measure := func(tpm *sb_tpm2.Connection) error {
return sbMeasureSnapSystemEpochToTPM(tpm, initramfsPCR)
}
if err := measureWhenPossible(measure); err != nil {
return fmt.Errorf("cannot measure snap system epoch: %v", err)
}
return nil
}
// MeasureSnapModelWhenPossible measures the snap model only if the TPM device is
// available. If there's no TPM device success is returned.
func MeasureSnapModelWhenPossible(findModel func() (*asserts.Model, error)) error {
measure := func(tpm *sb_tpm2.Connection) error {
model, err := findModel()
if err != nil {
return err
}
return sbMeasureSnapModelToTPM(tpm, initramfsPCR, model)
}
if err := measureWhenPossible(measure); err != nil {
return fmt.Errorf("cannot measure snap model: %v", err)
}
return nil
}
func lockTPMSealedKeys() error {
tpm, tpmErr := sbConnectToDefaultTPM()
if tpmErr != nil {
if xerrors.Is(tpmErr, sb_tpm2.ErrNoTPM2Device) {
logger.Noticef("cannot open TPM connection: %v", tpmErr)
return nil
}
return fmt.Errorf("cannot lock TPM: %v", tpmErr)
}
defer tpm.Close()
// Lock access to the sealed keys. This should be called whenever there
// is a TPM device detected, regardless of whether secure boot is enabled
// or there is an encrypted volume to unlock. Note that snap-bootstrap can
// be called several times during initialization, and if there are multiple
// volumes to unlock we should lock access to the sealed keys only after
// the last encrypted volume is unlocked, in which case lockKeysOnFinish
// should be set to true.
//
// We should only touch the PCR that we've currently reserved for the kernel
// EFI image. Touching others will break the ability to perform any kind of
// attestation using the TPM because it will make the log inconsistent.
return sbBlockPCRProtectionPolicies(tpm, []int{initramfsPCR})
}
func activateVolOpts(allowRecoveryKey bool, allowPassphrase bool, legacyPaths ...string) *sb.ActivateVolumeOptions {
passphraseTry := 0
if allowPassphrase {
passphraseTry = 1
}
options := sb.ActivateVolumeOptions{
PassphraseTries: passphraseTry,
// disable recovery key by default
RecoveryKeyTries: 0,
KeyringPrefix: keyringPrefix,
LegacyDevicePaths: legacyPaths,
}
if allowRecoveryKey {
// enable recovery key only when explicitly allowed
options.RecoveryKeyTries = 3
}
return &options
}
func newAuthRequestor() sb.AuthRequestor {
return NewSystemdAuthRequestor()
}
func readKeyTokenImpl(devicePath, slotName string) (*sb.KeyData, error) {
kdReader, err := sb.NewLUKS2KeyDataReader(devicePath, slotName)
if err != nil {
return nil, err
}
return sb.ReadKeyData(kdReader)
}
var readKeyToken = readKeyTokenImpl
// TODO:FDEM: we do not really need an interface here, a struct would be
// enough.
type keyLoader interface {
// LoadedKeyData keeps track of keys in KeyData format.
LoadedKeyData(kd *sb.KeyData)
// LoadedSealedKeyObject keeps track of sealed key object for
// legacy TPM This is useful for resealing. For unlocking, a
// matching KeyData will also be emitted.
LoadedSealedKeyObject(sko *sb_tpm2.SealedKeyObject)
// LoadedFDEHookKeyV1 keeps track of sealed key object for
// legacy FDE hooks. In this case no KeyData is emitted.
LoadedFDEHookKeyV1(sk []byte)
}
type defaultKeyLoader struct {
KeyData *sb.KeyData
SealedKeyObject *sb_tpm2.SealedKeyObject
FDEHookKeyV1 []byte
}
func (dkl *defaultKeyLoader) LoadedKeyData(kd *sb.KeyData) {
dkl.KeyData = kd
}
func (dkl *defaultKeyLoader) LoadedSealedKeyObject(sko *sb_tpm2.SealedKeyObject) {
dkl.SealedKeyObject = sko
}
func (dkl *defaultKeyLoader) LoadedFDEHookKeyV1(sk []byte) {
dkl.FDEHookKeyV1 = sk
}
func hasOldSealedKeyPrefix(keyfile string) (bool, error) {
f, err := os.Open(keyfile)
if err != nil {
return false, err
}
defer f.Close()
var rawPrefix = []byte("USK$")
buf := make([]byte, len(rawPrefix))
l, err := io.ReadFull(f, buf)
if err != nil && err != io.ErrUnexpectedEOF {
return false, err
}
return l == len(rawPrefix) && bytes.HasPrefix(buf, rawPrefix), nil
}
// readKeyFileImpl attempts to read a key file. It will call the
// different key loader methods depending on the key format found. In
// case of a legacy sealed key object format, it will decide whether
// it is for TPM or FDE hooks base on hintExpectFDEHook. For all cases
// but the v1 FDE hook sealed objects, a KeyData will be provided. In
// the case of TPM sealed object, the key object itself will be
// provided. This is uselful for resealing, as the associated KeyData
// provided in that case will be enough for unlocking.
// TODO:FDEM: consider moving this to secboot
func readKeyFileImpl(keyfile string, kl keyLoader, hintExpectFDEHook bool) error {
oldSealedKey, err := hasOldSealedKeyPrefix(keyfile)
if err != nil {
return err
}
switch {
case oldSealedKey && hintExpectFDEHook:
// FDE hook key v1
//
// It has the same magic header as sealed key object,
// but there is no version information. Thus we need
// to use a hint that we are using FDE hooks.
sealedKey, err := os.ReadFile(keyfile)
if err != nil {
return fmt.Errorf("cannot read FDE hook v1 key: %v", err)
}
kl.LoadedFDEHookKeyV1(sealedKey)
return nil
case oldSealedKey && !hintExpectFDEHook:
// TPM sealed object
sealedObject, err := sbReadSealedKeyObjectFromFile(keyfile)
if err != nil {
return fmt.Errorf("cannot read key object: %v", err)
}
keyData, err := sbNewKeyDataFromSealedKeyObjectFile(keyfile)
if err != nil {
return fmt.Errorf("cannot read key object as key data: %v", err)
}
kl.LoadedKeyData(keyData)
kl.LoadedSealedKeyObject(sealedObject)
return nil
default:
reader, err := sbNewFileKeyDataReader(keyfile)
if err != nil {
return fmt.Errorf("cannot open key data: %v", err)
}
keyData, err := sbReadKeyData(reader)
if err != nil {
return err
}
kl.LoadedKeyData(keyData)
return nil
}
}
var readKeyFile = readKeyFileImpl
func (key KeyDataLocation) readTokenAndGetWriter() (*sb.KeyData, sb.KeyDataWriter, error) {
kd, err := readKeyToken(key.DevicePath, key.SlotName)
if err != nil {
return nil, nil, err
}
writer, err := newLUKS2KeyDataWriter(key.DevicePath, key.SlotName)
if err != nil {
return nil, nil, err
}
return kd, writer, nil
}
// readKeyDataAndGetWriter reads key data or sealed key object from a token or a
// file. The key data could be placed either way since the
// installation decides where to store it. When resealing, we do not
// know about this decision that might have been done with another
// version of snapd. So it has to try from both the token and file. It
// will read in priority from the token. It may return either a
// KeyData or a SealedKeyObject depending on the format if read from a
// file. It will return only a KeyData if found in a token. If a
// KeyData is returned, then a KeyDataWriter is also returned.
// TODO:FDEM: consider moving this to secboot_sb.go
func readKeyDataAndGetWriter(key KeyDataLocation) (*sb.KeyData, *sb_tpm2.SealedKeyObject, sb.KeyDataWriter, error) {
// We try with the token first. If we find it, we will ignore
// the file.
kd, writer, tokenErr := key.readTokenAndGetWriter()
if tokenErr == nil {
return kd, nil, writer, nil
}
// We did not find key data in the token. Let's try with the
// file.
loadedKey := &defaultKeyLoader{}
const hintExpectFDEHook = false
fileErr := readKeyFile(key.KeyFile, loadedKey, hintExpectFDEHook)
if fileErr == nil {
if loadedKey.SealedKeyObject == nil {
return loadedKey.KeyData, nil, sb.NewFileKeyDataWriter(key.KeyFile), nil
} else {
// loadedKey.SealedKeyObject is not nil, then
// the KeyData is just a work-around for
// unlocking. Let's ignore it here.
// There is no KeyDataWriter.
return nil, loadedKey.SealedKeyObject, nil, nil
}
}
return nil, nil, nil, fmt.Errorf(`trying to load key data from %s:%s returned "%v", and from %s returned "%v"`, key.DevicePath, key.SlotName, tokenErr, key.KeyFile, fileErr)
}
// ProvisionTPM provisions the default TPM and saves the lockout authorization
// key to the specified file.
func ProvisionTPM(mode TPMProvisionMode, lockoutAuthFile string) error {
tpm, err := sbConnectToDefaultTPM()
if err != nil {
return fmt.Errorf("cannot connect to TPM: %v", err)
}
defer tpm.Close()
if !isTPMEnabled(tpm) {
return fmt.Errorf("TPM device is not enabled")
}
if err := tpmProvision(tpm, mode, lockoutAuthFile); err != nil {
return err
}
return nil
}
// ProvisionForCVM provisions the default TPM using a custom SRK
// template that is created by the encrypt tool prior to first boot of
// Azure CVM instances. It takes UbuntuSeedDir (ESP) and expects
// "tpm2-srk.tmpl" there which is deleted after successful provision.
//
// Key differences with ProvisionTPM()
// - lack of TPM or if TPM is disabled is ignored.
// - it is fatal if TPM Provisioning requires a Lockout file
// - Custom SRK file is required in InitramfsUbuntuSeedDir
func ProvisionForCVM(initramfsUbuntuSeedDir string) error {
tpm, err := insecureConnectToTPM()
if err != nil {
if xerrors.Is(err, sb_tpm2.ErrNoTPM2Device) {
return nil
}
return fmt.Errorf("cannot open TPM connection: %v", err)
}
defer tpm.Close()
if !isTPMEnabled(tpm) {
return nil
}
srkTmplPath := filepath.Join(initramfsUbuntuSeedDir, "tpm2-srk.tmpl")
f, err := os.Open(srkTmplPath)
if err != nil {
if os.IsNotExist(err) {
return nil
}
return fmt.Errorf("cannot open SRK template file: %v", err)
}
defer f.Close()
var srkTmpl *tpm2.Public
if _, err := mu.UnmarshalFromReader(f, mu.Sized(&srkTmpl)); err != nil {
return fmt.Errorf("cannot read SRK template: %v", err)
}
err = sbTPMEnsureProvisionedWithCustomSRK(tpm, sb_tpm2.ProvisionModeWithoutLockout, nil, srkTmpl)
if err != nil && err != sb_tpm2.ErrTPMProvisioningRequiresLockout {
return fmt.Errorf("cannot prepare TPM: %v", err)
}
if err := os.Remove(srkTmplPath); err != nil {
return fmt.Errorf("cannot remove SRK template file: %v", err)
}
return nil
}
func kdfOptions(volumesAuth *device.VolumesAuthOptions) (sb.KDFOptions, error) {
switch volumesAuth.KDFType {
case "":
return nil, nil
case "argon2id":
return &sb.Argon2Options{
Mode: sb.Argon2id,
TargetDuration: volumesAuth.KDFTime,
}, nil
case "argon2i":
return &sb.Argon2Options{
Mode: sb.Argon2i,
TargetDuration: volumesAuth.KDFTime,
}, nil
case "pbkdf2":
return &sb.PBKDF2Options{
TargetDuration: volumesAuth.KDFTime,
}, nil
default:
return nil, fmt.Errorf("internal error: unknown kdfType passed %q", volumesAuth.KDFType)
}
}
func newTPMProtectedKey(tpm *sb_tpm2.Connection, creationParams *sb_tpm2.ProtectKeyParams, volumesAuth *device.VolumesAuthOptions) (protectedKey *sb.KeyData, primaryKey sb.PrimaryKey, unlockKey sb.DiskUnlockKey, err error) {
if volumesAuth != nil {
switch volumesAuth.Mode {
case device.AuthModePassphrase:
kdfOptions, kdferr := kdfOptions(volumesAuth)
if kdferr != nil {
return nil, nil, nil, kdferr
}
passphraseParams := &sb_tpm2.PassphraseProtectKeyParams{
ProtectKeyParams: *creationParams,
KDFOptions: kdfOptions,
}
protectedKey, primaryKey, unlockKey, err = sbNewTPMPassphraseProtectedKey(tpm, passphraseParams, volumesAuth.Passphrase)
case device.AuthModePIN:
// TODO: Implement PIN authentication mode.
return nil, nil, nil, fmt.Errorf("%q authentication mode is not implemented", device.AuthModePIN)
default:
return nil, nil, nil, fmt.Errorf("internal error: invalid authentication mode %q", volumesAuth.Mode)
}
} else {
protectedKey, primaryKey, unlockKey, err = sbNewTPMProtectedKey(tpm, creationParams)
}
return protectedKey, primaryKey, unlockKey, err
}
// SealKeys seals the encryption keys according to the specified parameters. The
// TPM must have already been provisioned. If sealed key already exists at the
// PCR handle, SealKeys will fail and return an error.
func SealKeys(keys []SealKeyRequest, params *SealKeysParams) ([]byte, error) {
numModels := len(params.ModelParams)
if numModels < 1 {
return nil, fmt.Errorf("at least one set of model-specific parameters is required")
}
tpm, err := sbConnectToDefaultTPM()
if err != nil {
return nil, fmt.Errorf("cannot connect to TPM: %v", err)
}
defer tpm.Close()
if !isTPMEnabled(tpm) {
return nil, fmt.Errorf("TPM device is not enabled")
}
pcrProfile, err := buildPCRProtectionProfile(params.ModelParams, params.AllowInsufficientDmaProtection)
if err != nil {
return nil, err
}
pcrHandle := params.PCRPolicyCounterHandle
logger.Noticef("sealing with PCR handle %#x", pcrHandle)
var primaryKey sb.PrimaryKey
if params.PrimaryKey != nil {
primaryKey = params.PrimaryKey
}
for _, key := range keys {
creationParams := &sb_tpm2.ProtectKeyParams{
PCRProfile: pcrProfile,
Role: params.KeyRole,
PCRPolicyCounterHandle: tpm2.Handle(pcrHandle),
PrimaryKey: primaryKey,
}
protectedKey, primaryKeyOut, unlockKey, err := newTPMProtectedKey(tpm, creationParams, params.VolumesAuth)
if primaryKey == nil {
primaryKey = primaryKeyOut
}
if err != nil {
return nil, err
}
if err := key.BootstrappedContainer.AddKey(key.SlotName, unlockKey); err != nil {
return nil, err
}
keyWriter, err := key.getWriter()
if err != nil {
return nil, err
}
if err := protectedKey.WriteAtomic(keyWriter); err != nil {
return nil, err
}
if key.SlotName == "default" {
// "default" key will only be TPM on data disk. "save" disk will be handled
// with the protector key.
key.BootstrappedContainer.RegisterKeyAsUsed(primaryKeyOut, unlockKey)
}
}
if primaryKey != nil && params.TPMPolicyAuthKeyFile != "" {
if err := osutil.AtomicWriteFile(params.TPMPolicyAuthKeyFile, primaryKey, 0600, 0); err != nil {
return nil, fmt.Errorf("cannot write the policy auth key file: %v", err)
}
}
return primaryKey, nil
}
// MaybeSealedKeyData interface wraps a sb_tpm2.SealedKeyData
// This is mainly used to be able to mock sb_tpm2.SealedKeyData
type MaybeSealedKeyData interface {
// Unwrap returns the sealed key data contained in this wrapper
Unwrap() *sb_tpm2.SealedKeyData
}
func sbTPMRevokeOldPCRProtectionPoliciesImpl(key MaybeSealedKeyData, tpm *sb_tpm2.Connection, primaryKey []byte) error {
return key.Unwrap().RevokeOldPCRProtectionPolicies(tpm, primaryKey)
}
var sbTPMRevokeOldPCRProtectionPolicies = sbTPMRevokeOldPCRProtectionPoliciesImpl
// UpdatedKeys is a collection of updated sealed key that can be used to
// revoke older keys.
// Sealed keys *may* use different policy counter, though in practice they
// all share the same counter. This is why we need a collection.
type UpdatedKeys []MaybeSealedKeyData
type actualSealedKeyData struct {
data *sb_tpm2.SealedKeyData
}
func (a *actualSealedKeyData) Unwrap() *sb_tpm2.SealedKeyData {
return a.data
}
// RevokeOldKeys goes through all of the updated keys and
// make sure to increase all the policy counters used by those
// keys to the value those keys use.
func (uk *UpdatedKeys) RevokeOldKeys(primaryKey []byte) error {
tpm, err := sbConnectToDefaultTPM()
if err != nil {
return fmt.Errorf("cannot connect to TPM: %v", err)
}
defer tpm.Close()
if !isTPMEnabled(tpm) {
return fmt.Errorf("TPM device is not enabled")
}
for _, key := range *uk {
if err := sbTPMRevokeOldPCRProtectionPolicies(key, tpm, primaryKey); err != nil {
return err
}
}
return nil
}
func sbNewSealedKeyDataImpl(k *sb.KeyData) (MaybeSealedKeyData, error) {
kd, err := sb_tpm2.NewSealedKeyData(k)
return &actualSealedKeyData{kd}, err
}
var sbNewSealedKeyData = sbNewSealedKeyDataImpl
type resealKeysWithTPMParams struct {
// The snap model parameters
PCRProfile SerializedPCRProfile
// The locations to the key data
Keys []KeyDataLocation
// The primary key
PrimaryKey []byte
}
// resealKeysWithTPMImpl updates the PCR protection policy for the sealed encryption keys
// according to the specified parameters.
// If newPCRPolicyVersion is true, the keys will use a new policy version
// so that the policy counter can be incremented. The function will
// then also return the updated keys in order to increase the counter.
func resealKeysWithTPMImpl(params *resealKeysWithTPMParams, newPCRPolicyVersion bool) (UpdatedKeys, error) {
numSealedKeyObjects := len(params.Keys)
if numSealedKeyObjects < 1 {
return nil, fmt.Errorf("at least one key file is required")
}
tpm, err := sbConnectToDefaultTPM()
if err != nil {
return nil, fmt.Errorf("cannot connect to TPM: %v", err)
}
defer tpm.Close()
if !isTPMEnabled(tpm) {
return nil, fmt.Errorf("TPM device is not enabled")
}
var pcrProfile sb_tpm2.PCRProtectionProfile
if _, err := mu.UnmarshalFromBytes(params.PCRProfile, &pcrProfile); err != nil {
return nil, err
}
keyDatas := make([]*sb.KeyData, 0, numSealedKeyObjects)
sealedKeyObjects := make([]*sb_tpm2.SealedKeyObject, 0, numSealedKeyObjects)
writers := make([]sb.KeyDataWriter, 0, numSealedKeyObjects)
for _, key := range params.Keys {
keyData, keyObject, writer, err := readKeyDataAndGetWriter(key)
if err != nil {
return nil, err
}
if keyObject == nil {
if writer == nil {
return nil, fmt.Errorf("internal error: new keydata has no writer")
}
writers = append(writers, writer)
keyDatas = append(keyDatas, keyData)
} else {
sealedKeyObjects = append(sealedKeyObjects, keyObject)
}
}
hasOldSealedKeyObjects := len(sealedKeyObjects) != 0
hasKeyDatas := len(keyDatas) != 0
if hasOldSealedKeyObjects && hasKeyDatas {
return nil, fmt.Errorf("key files are different formats")
}
var updatedKeys UpdatedKeys
if hasOldSealedKeyObjects {
if err := sbUpdateKeyPCRProtectionPolicyMultiple(tpm, sealedKeyObjects, params.PrimaryKey, &pcrProfile); err != nil {
return nil, fmt.Errorf("cannot update legacy PCR protection policy: %w", err)
}
// write key files
for i, sko := range sealedKeyObjects {
w := sb_tpm2.NewFileSealedKeyObjectWriter(params.Keys[i].KeyFile)
if err := sko.WriteAtomic(w); err != nil {
return nil, fmt.Errorf("cannot write key data file %s: %w", params.Keys[i].KeyFile, err)
}
}
// revoke old policies via the primary key object
if err := sbSealedKeyObjectRevokeOldPCRProtectionPolicies(sealedKeyObjects[0], tpm, params.PrimaryKey); err != nil {
return nil, fmt.Errorf("cannot revoke old PCR protection policies: %w", err)
}
} else {
policyVersion := sb_tpm2.NoNewPCRPolicyVersion
if newPCRPolicyVersion {
policyVersion = sb_tpm2.NewPCRPolicyVersion
}
if err := sbUpdateKeyDataPCRProtectionPolicy(tpm, params.PrimaryKey, &pcrProfile, policyVersion, keyDatas...); err != nil {
return nil, fmt.Errorf("cannot update PCR protection policy: %w", err)
}
for i, key := range params.Keys {
if err := keyDatas[i].WriteAtomic(writers[i]); err != nil {
return nil, fmt.Errorf("cannot write key data in keyfile %s:%s: %w", key.DevicePath, key.SlotName, err)
}
}
if newPCRPolicyVersion {
for i, keyData := range keyDatas {
skd, err := sbNewSealedKeyData(keyData)
if err != nil {
key := params.Keys[i]
return nil, fmt.Errorf("cannot get sealed key data for keyfile %s:%s: %w", key.DevicePath, key.SlotName, err)
}
updatedKeys = append(updatedKeys, skd)
}
}
}
return updatedKeys, nil
}
var resealKeysWithTPM = resealKeysWithTPMImpl
func buildPCRProtectionProfile(modelParams []*SealKeyModelParams, allowInsufficientDmaProtection bool) (*sb_tpm2.PCRProtectionProfile, error) {
numModels := len(modelParams)
modelPCRProfiles := make([]*sb_tpm2.PCRProtectionProfile, 0, numModels)
for _, mp := range modelParams {
var updateDB []*sb_efi.SignatureDBUpdate
if len(mp.EFISignatureDbxUpdate) > 0 {
updateDB = append(updateDB, &sb_efi.SignatureDBUpdate{
Name: sb_efi.Dbx,
Data: mp.EFISignatureDbxUpdate,
})
}
modelProfile := sb_tpm2.NewPCRProtectionProfile()
loadSequences, err := buildLoadSequences(mp.EFILoadChains)
if err != nil {
return nil, fmt.Errorf("cannot build EFI image load sequences: %v", err)
}
var options []sb_efi.PCRProfileOption
options = append(options,
sb_efi.WithSecureBootPolicyProfile(),
sb_efi.WithBootManagerCodeProfile(),
sb_efi.WithSignatureDBUpdates(updateDB...),
)
if allowInsufficientDmaProtection {
options = append(options, sb_efi.WithAllowInsufficientDmaProtection())
}
if err := sbefiAddPCRProfile(
tpm2.HashAlgorithmSHA256,
modelProfile.RootBranch(),
loadSequences,
options...,
); err != nil {
return nil, fmt.Errorf("cannot add EFI secure boot and boot manager policy profiles: %v", err)
}
// Add systemd EFI stub profile
if len(mp.KernelCmdlines) != 0 {
systemdStubParams := sb_efi.SystemdStubProfileParams{
PCRAlgorithm: tpm2.HashAlgorithmSHA256,
PCRIndex: initramfsPCR,
KernelCmdlines: mp.KernelCmdlines,
}
if err := sbefiAddSystemdStubProfile(modelProfile.RootBranch(), &systemdStubParams); err != nil {
return nil, fmt.Errorf("cannot add systemd EFI stub profile: %v", err)
}
}
// Add snap model profile
if mp.Model != nil {
snapModelParams := sb_tpm2.SnapModelProfileParams{
PCRAlgorithm: tpm2.HashAlgorithmSHA256,
PCRIndex: initramfsPCR,
Models: []sb.SnapModel{mp.Model},
}
if err := sbAddSnapModelProfile(modelProfile.RootBranch(), &snapModelParams); err != nil {
return nil, fmt.Errorf("cannot add snap model profile: %v", err)
}
}
modelPCRProfiles = append(modelPCRProfiles, modelProfile)
}
pcrProfile := sb_tpm2.NewPCRProtectionProfile().AddProfileOR(modelPCRProfiles...)
logger.Debugf("PCR protection profile:\n%s", pcrProfile.String())
return pcrProfile, nil
}
// BuildPCRProtectionProfile builds and serializes a PCR profile from
// a list of SealKeyModelParams.
func BuildPCRProtectionProfile(modelParams []*SealKeyModelParams, allowInsufficientDmaProtection bool) (SerializedPCRProfile, error) {
pcrProfile, err := buildPCRProtectionProfile(modelParams, allowInsufficientDmaProtection)
if err != nil {
return nil, err
}
return mu.MarshalToBytes(pcrProfile)
}
func tpmProvision(tpm *sb_tpm2.Connection, mode TPMProvisionMode, lockoutAuthFile string) error {
var currentLockoutAuth []byte
if mode == TPMPartialReprovision {
logger.Debugf("using existing lockout authorization")
d, err := os.ReadFile(lockoutAuthFile)
if err != nil {
return fmt.Errorf("cannot read existing lockout auth: %v", err)
}
currentLockoutAuth = d
}
// Create and save the lockout authorization file
lockoutAuth := make([]byte, 16)
// crypto rand is protected against short reads
_, err := rand.Read(lockoutAuth)
if err != nil {
return fmt.Errorf("cannot create lockout authorization: %v", err)
}
if err := osutil.AtomicWriteFile(lockoutAuthFile, lockoutAuth, 0600, 0); err != nil {
return fmt.Errorf("cannot write the lockout authorization file: %v", err)
}
// TODO:UC20: ideally we should ask the firmware to clear the TPM and then reboot
// if the device has previously been provisioned, see
// https://godoc.org/github.com/snapcore/secboot#RequestTPMClearUsingPPI
if currentLockoutAuth != nil {
// use the current lockout authorization data to authorize
// provisioning
tpm.LockoutHandleContext().SetAuthValue(currentLockoutAuth)
}
if err := sbTPMEnsureProvisioned(tpm, sb_tpm2.ProvisionModeFull, lockoutAuth); err != nil {
logger.Noticef("TPM provisioning error: %v", err)
return fmt.Errorf("cannot provision TPM: %v", err)
}
return nil
}
// buildLoadSequences builds EFI load image event trees from this package LoadChains
func buildLoadSequences(chains []*LoadChain) (loadseqs *sb_efi.ImageLoadSequences, err error) {
// this will build load event trees for the current
// device configuration, e.g. something like:
//
// shim -> recovery grub -> recovery kernel 1
// |-> recovery kernel 2
// |-> recovery kernel ...
// |-> normal grub -> run kernel good
// |-> run kernel try
loadseqs = sb_efi.NewImageLoadSequences()
for _, chain := range chains {
// root of load events has source Firmware
loadseq, err := chain.loadEvent()
if err != nil {
return nil, err
}
loadseqs.Append(loadseq)
}
return loadseqs, nil
}
// loadEvent builds the corresponding load event and its tree
func (lc *LoadChain) loadEvent() (sb_efi.ImageLoadActivity, error) {
var next []sb_efi.ImageLoadActivity
for _, nextChain := range lc.Next {
// everything that is not the root has source shim
ev, err := nextChain.loadEvent()
if err != nil {
return nil, err
}
next = append(next, ev)
}
image, err := efiImageFromBootFile(lc.BootFile)
if err != nil {
return nil, err
}
return sb_efi.NewImageLoadActivity(image).Loads(next...), nil
}
func efiImageFromBootFile(b *bootloader.BootFile) (sb_efi.Image, error) {
if b.Snap == "" {
if !osutil.FileExists(b.Path) {
return nil, fmt.Errorf("file %s does not exist", b.Path)
}
return sb_efi.FileImage(b.Path), nil
}
snapf, err := snapfile.Open(b.Snap)
if err != nil {
return nil, err
}
return sb_efi.NewSnapFileImage(
snapf,
b.Path,
), nil
}
func tpmReleaseResourcesImpl(tpm *sb_tpm2.Connection, handle tpm2.Handle) error {
rc, err := tpm.CreateResourceContextFromTPM(handle)
if err != nil {
if tpm2.IsResourceUnavailableError(err, handle) {
// there's nothing to release, the handle isn't used
return nil
}
return fmt.Errorf("cannot create resource context: %v", err)
}
if err := tpm.NVUndefineSpace(tpm.OwnerHandleContext(), rc, tpm.HmacSession()); err != nil {
return fmt.Errorf("cannot undefine space: %v", err)
}
return nil
}
// releasePCRResourceHandles releases any TPM resources associated with given
// PCR handles.
// TODO:FDEM:FIX: were are not releasing PCR handles, but NV index handles. So
// the name is confusing
func releasePCRResourceHandles(handles ...uint32) error {
tpm, err := sbConnectToDefaultTPM()
if err != nil {
err = fmt.Errorf("cannot connect to TPM device: %v", err)
return err
}
defer tpm.Close()
var errs []string
for _, handle := range handles {
logger.Debugf("releasing PCR handle %#x", handle)
if err := tpmReleaseResources(tpm, tpm2.Handle(handle)); err != nil {
errs = append(errs, fmt.Sprintf("handle %#x: %v", handle, err))
}
}
if errCnt := len(errs); errCnt != 0 {
return fmt.Errorf("cannot release TPM resources for %v handles:\n%v", errCnt, strings.Join(errs, "\n"))
}
return nil
}
func resetLockoutCounter(lockoutAuthFile string) error {
tpm, err := sbConnectToDefaultTPM()
if err != nil {
return fmt.Errorf("cannot connect to TPM: %v", err)
}
defer tpm.Close()
lockoutAuth, err := os.ReadFile(lockoutAuthFile)
if err != nil {
return fmt.Errorf("cannot read existing lockout auth: %v", err)
}
tpm.LockoutHandleContext().SetAuthValue(lockoutAuth)
if err := sbTPMDictionaryAttackLockReset(tpm, tpm.LockoutHandleContext(), tpm.HmacSession()); err != nil {
return err
}
return nil
}
type mockableSealedKeyData interface {
PCRPolicyCounterHandle() tpm2.Handle
}
type mockableSealedKeyObject interface {
PCRPolicyCounterHandle() tpm2.Handle
}
type mockableKeyData interface {
PlatformName() string
GetTPMSealedKeyData() (mockableSealedKeyData, error)
}
type realSealedKeyData struct {
*sb_tpm2.SealedKeyData
}
type realSealedKeyObject struct {
*sb_tpm2.SealedKeyObject
}
type realKeyData struct {
*sb.KeyData
}
func (keyData *realKeyData) GetTPMSealedKeyData() (mockableSealedKeyData, error) {
skd, err := sb_tpm2.NewSealedKeyData(keyData.KeyData)
if err != nil {
return nil, err
}
return &realSealedKeyData{skd}, nil
}
func mockableReadKeyDataImpl(r sb.KeyDataReader) (mockableKeyData, error) {
keyData, err := sb.ReadKeyData(r)
if err != nil {
return nil, err
}
return &realKeyData{keyData}, nil
}
var mockableReadKeyData = mockableReadKeyDataImpl
type mockableKeyLoader struct {
KeyData mockableKeyData
SealedKeyObject mockableSealedKeyObject
FDEHookKeyV1 []byte
}
func (dkl *mockableKeyLoader) LoadedKeyData(kd *sb.KeyData) {
dkl.KeyData = &realKeyData{kd}
}
func (dkl *mockableKeyLoader) LoadedSealedKeyObject(sko *sb_tpm2.SealedKeyObject) {
dkl.SealedKeyObject = &realSealedKeyObject{sko}
}
func (dkl *mockableKeyLoader) LoadedFDEHookKeyV1(sk []byte) {
dkl.FDEHookKeyV1 = sk
}
func mockableReadKeyFileImpl(keyFile string, keyLoader *mockableKeyLoader, hintExpectFDEHook bool) error {
return readKeyFile(keyFile, keyLoader, hintExpectFDEHook)
}
var mockableReadKeyFile = mockableReadKeyFileImpl
// GetPCRHandle returns the handle used by a key. The key will be
// searched on the token of the keySlot from the node. If that keySlot
// has no KeyData, then the key will be loaded at path keyFile.
func GetPCRHandle(node, keySlot, keyFile string, hintExpectFDEHook bool) (uint32, error) {
slots, err := sbListLUKS2ContainerUnlockKeyNames(node)
if err != nil {
return 0, fmt.Errorf("cannot list slots in partition save partition: %v", err)
}
var readKeyDataErr error
for _, slot := range slots {
if slot == keySlot {
reader, err := sbNewLUKS2KeyDataReader(node, slot)
if err != nil {
// We save the error and try the file instead.
readKeyDataErr = err
break
}
keyData, err := mockableReadKeyData(reader)
if err != nil {
return 0, fmt.Errorf("cannot read key data for slot '%s': %w", keySlot, err)
}
if keyData.PlatformName() != platformTpm2 {
return 0, nil
}
sealedKeyData, err := keyData.GetTPMSealedKeyData()
if err != nil {
return 0, fmt.Errorf("cannot read sealed key data for slot '%s': %w", keySlot, err)
}
return uint32(sealedKeyData.PCRPolicyCounterHandle()), nil
}
}
loadedKey := &mockableKeyLoader{}
err = mockableReadKeyFile(keyFile, loadedKey, hintExpectFDEHook)
if err != nil {
if os.IsNotExist(err) {
if readKeyDataErr != nil {
// TODO:FDEM:FIX: secboot should tell us if
// Data was nil, in that case we
// should be silent, otherwise we
// should return the error.
logger.Noticef("WARNING: cannot read key data for slot %s: %v", keySlot, readKeyDataErr)
return 0, nil
}
return 0, nil
}
return 0, fmt.Errorf("cannot read key file %s: %w", keyFile, err)
}
if loadedKey.SealedKeyObject != nil {
return uint32(loadedKey.SealedKeyObject.PCRPolicyCounterHandle()), nil
}
if loadedKey.KeyData != nil {
if loadedKey.KeyData.PlatformName() != platformTpm2 {
return 0, nil
}
sealedKeyData, err := loadedKey.KeyData.GetTPMSealedKeyData()
if err != nil {
return 0, fmt.Errorf("cannot read sealed key data from %s: %w", keyFile, err)
}
return uint32(sealedKeyData.PCRPolicyCounterHandle()), nil
}
return 0, nil
}
// RemoveOldCounterHandles releases TPM2 handles used by some keys.
// The keys for which handles are released are:
// - in the keyslots of the given device, with names matching possibleOldKeys.
// - in key files at paths given by possibleKeyFiles.
//
// All TPM2 handles found in any key found will be removed. If keyslots
// or key files are not found, they are just ignored.
// hintExpectFDEHook helps reading old key object files. If not TPM2
// key is found, nothing happens.
func RemoveOldCounterHandles(device string, possibleOldKeys map[string]bool, possibleKeyFiles []string, hintExpectFDEHook bool) error {
slots, err := sbListLUKS2ContainerUnlockKeyNames(device)
if err != nil {
return fmt.Errorf("cannot list slots in partition save partition: %v", err)
}
oldHandles := make(map[uint32]bool)
for _, slot := range slots {
if possibleOldKeys[slot] {
reader, err := sbNewLUKS2KeyDataReader(device, slot)
if err != nil {
// TODO:FDEM:FIX: secboot should tell us if
// Data was nil, in that case we
// should be silent, otherwise we
// should return the error.
continue
}
keyData, err := mockableReadKeyData(reader)
if err != nil {
return fmt.Errorf("cannot read key data for slot '%s': %w", slot, err)
}
if keyData.PlatformName() != platformTpm2 {
continue
}
sealedKeyData, err := keyData.GetTPMSealedKeyData()
if err != nil {
return fmt.Errorf("cannot read sealed key data for slot '%s': %w", slot, err)
}
oldHandles[uint32(sealedKeyData.PCRPolicyCounterHandle())] = true
}
}
for _, keyFile := range possibleKeyFiles {
loadedKey := &mockableKeyLoader{}
err := mockableReadKeyFile(keyFile, loadedKey, hintExpectFDEHook)
if err != nil {
if os.IsNotExist(err) {
continue
}
return fmt.Errorf("cannot read key file %s: %w", keyFile, err)
}
if loadedKey.SealedKeyObject != nil {
handle := uint32(loadedKey.SealedKeyObject.PCRPolicyCounterHandle())
oldHandles[handle] = true
// We used multiple handles before. But we
// lost track of the handle for the run key as
// we reformatted it already. Let's add the
// matching run handle.
if handle == AltFallbackObjectPCRPolicyCounterHandle {
oldHandles[AltRunObjectPCRPolicyCounterHandle] = true
} else if handle == FallbackObjectPCRPolicyCounterHandle {
oldHandles[RunObjectPCRPolicyCounterHandle] = true
} else {
logger.Noticef("WARNING: we are deleting an unexpected handle. That should never have happened.")
}
} else if loadedKey.KeyData != nil {
if loadedKey.KeyData.PlatformName() != platformTpm2 {
continue
}
sealedKeyData, err := loadedKey.KeyData.GetTPMSealedKeyData()
if err != nil {
return fmt.Errorf("cannot read sealed key data from %s: %w", keyFile, err)
}
oldHandles[uint32(sealedKeyData.PCRPolicyCounterHandle())] = true
}
}
var oldHandlesList []uint32
for handle := range oldHandles {
switch {
case handle == RunObjectPCRPolicyCounterHandle:
fallthrough
case handle == FallbackObjectPCRPolicyCounterHandle:
fallthrough
case handle == AltRunObjectPCRPolicyCounterHandle:
fallthrough
case handle == AltFallbackObjectPCRPolicyCounterHandle:
fallthrough
case handle >= PCRPolicyCounterHandleStart && handle < PCRPolicyCounterHandleStart+PCRPolicyCounterHandleRange:
oldHandlesList = append(oldHandlesList, handle)
}
}
if len(oldHandlesList) == 0 {
return nil
}
return releasePCRResourceHandles(oldHandlesList...)
}
// FindFreeHandle finds and unused handle on the TPM.
// The handle will be arbitrary in range 0x01880005-0x0188000F.
func FindFreeHandle() (uint32, error) {
tpm, err := sbConnectToDefaultTPM()
if err != nil {
return 0, fmt.Errorf("cannot connect to TPM: %w", err)
}
defer tpm.Close()
handles, err := tpmGetCapabilityHandles(tpm, tpm2.Handle(PCRPolicyCounterHandleStart), PCRPolicyCounterHandleRange)
if err != nil {
return 0, fmt.Errorf("cannot get free handles: %w", err)
}
takenHandles := make(map[uint32]bool)
for _, handle := range handles {
logger.Debugf("TPM handle %v is in use", uint32(handle))
takenHandles[uint32(handle)] = true
}
for _, tentative := range randutil.Perm(int(PCRPolicyCounterHandleRange)) {
handle := PCRPolicyCounterHandleStart + uint32(tentative)
if !takenHandles[PCRPolicyCounterHandleStart+uint32(tentative)] {
logger.Debugf("TPM handle %v is free, taking it", uint32(handle))
return handle, nil
}
}
return 0, fmt.Errorf("no free handle on TPM")
}
// AddContainerRecoveryKey adds a new TPM protected key to specified device.
//
// Note: The unlock and primary keys are implicitly obtained from the kernel
// keyring so this will not work if the disk was unlocked with a recovery key
// during boot.
func AddContainerTPMProtectedKey(devicePath, slotName string, params *ProtectKeyParams) (err error) {
var pcrProfile sb_tpm2.PCRProtectionProfile
if _, err := mu.UnmarshalFromBytes(params.PCRProfile, &pcrProfile); err != nil {
return fmt.Errorf("cannot unmarshal PCR profile: %v", err)
}
// this will fail if the disk was unlocked with a recovery key during boot.
primaryKey, err := sbGetPrimaryKeyFromKernel(defaultKeyringPrefix, devicePath, false)
if err != nil {
return fmt.Errorf("cannot get primary key from kernel keyring for unlocked disk %s: %v", devicePath, err)
}
unlockKey, err := sbGetDiskUnlockKeyFromKernel(defaultKeyringPrefix, devicePath, false)
if err != nil {
return fmt.Errorf("cannot get unlock key from kernel keyring for unlocked disk %s: %v", devicePath, err)
}
tpm, err := sbConnectToDefaultTPM()
if err != nil {
return fmt.Errorf("cannot connect to TPM: %v", err)
}
defer tpm.Close()
if !isTPMEnabled(tpm) {
return errors.New("TPM device is not enabled")
}
creationParams := &sb_tpm2.ProtectKeyParams{
PCRProfile: &pcrProfile,
Role: params.KeyRole,
PCRPolicyCounterHandle: tpm2.Handle(params.PCRPolicyCounterHandle),
PrimaryKey: primaryKey,
}
protectedKey, _, newKey, err := newTPMProtectedKey(tpm, creationParams, params.VolumesAuth)
if err != nil {
return fmt.Errorf("cannot seal key: %v", err)
}
if err := sbAddLUKS2ContainerUnlockKey(devicePath, slotName, unlockKey, newKey); err != nil {
return fmt.Errorf("cannot add key: %v", err)
}
defer func() {
if err != nil {
if deleteErr := sbDeleteLUKS2ContainerKey(devicePath, slotName); deleteErr != nil {
logger.Noticef("cannot remove added key %s:%s during cleanup", devicePath, slotName)
}
}
}()
keyData := keyData{kd: protectedKey}
return keyData.WriteTokenAtomic(devicePath, slotName)
}
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