Golang data.RootFromSigned函数代码示例

// We cannot validate a new root if the old root is corrupt, because there might
// have been a root key rotation.
func TestValidateOldRootCorruptRootRole(t *testing.T) {
	gun := "docker.com/notary"
	repo, cs, err := testutils.EmptyRepo(gun)
	require.NoError(t, err)
	store := storage.NewMemStorage()

	r, tg, sn, ts, err := testutils.Sign(repo)
	require.NoError(t, err)
	root, targets, snapshot, timestamp, err := getUpdates(r, tg, sn, ts)
	require.NoError(t, err)

	// so a valid root, but missing the root role
	signedRoot, err := data.RootFromSigned(r)
	require.NoError(t, err)
	delete(signedRoot.Signed.Roles, data.CanonicalRootRole)
	badRootJSON, err := json.Marshal(signedRoot)
	require.NoError(t, err)
	badRoot := storage.MetaUpdate{
		Version: root.Version,
		Role:    root.Role,
		Data:    badRootJSON,
	}
	store.UpdateCurrent(gun, badRoot)
	updates := []storage.MetaUpdate{root, targets, snapshot, timestamp}

	serverCrypto := testutils.CopyKeys(t, cs, data.CanonicalTimestampRole)
	_, err = validateUpdate(serverCrypto, gun, updates, store)
	require.Error(t, err)
	require.IsType(t, data.ErrInvalidMetadata{}, err)
}

func TestValidateRootWithPinnedCert(t *testing.T) {
	var testSignedRoot data.Signed
	var signedRootBytes bytes.Buffer

	// Temporary directory where test files will be created
	tempBaseDir, err := ioutil.TempDir("", "notary-test-")
	defer os.RemoveAll(tempBaseDir)
	require.NoError(t, err, "failed to create a temporary directory: %s", err)

	// Execute our template
	templ, _ := template.New("SignedRSARootTemplate").Parse(signedRSARootTemplate)
	templ.Execute(&signedRootBytes, SignedRSARootTemplate{RootPem: validPEMEncodedRSARoot})

	// Unmarshal our signedroot
	json.Unmarshal(signedRootBytes.Bytes(), &testSignedRoot)
	typedSignedRoot, err := data.RootFromSigned(&testSignedRoot)
	require.NoError(t, err)

	// This call to trustpinning.ValidateRoot should succeed with the correct Cert ID (same as root public key ID)
	validatedSignedRoot, err := trustpinning.ValidateRoot(nil, &testSignedRoot, "docker.com/notary", trustpinning.TrustPinConfig{Certs: map[string][]string{"docker.com/notary": {rootPubKeyID}}, DisableTOFU: true})
	require.NoError(t, err)
	generateRootKeyIDs(typedSignedRoot)
	require.Equal(t, validatedSignedRoot, typedSignedRoot)

	// This call to trustpinning.ValidateRoot should also succeed with the correct Cert ID (same as root public key ID), even though we passed an extra bad one
	validatedSignedRoot, err = trustpinning.ValidateRoot(nil, &testSignedRoot, "docker.com/notary", trustpinning.TrustPinConfig{Certs: map[string][]string{"docker.com/notary": {rootPubKeyID, "invalidID"}}, DisableTOFU: true})
	require.NoError(t, err)
	require.Equal(t, validatedSignedRoot, typedSignedRoot)
}

func (r *NotaryRepository) bootstrapClient() (*tufclient.Client, error) {
	var rootJSON []byte
	remote, err := getRemoteStore(r.baseURL, r.gun, r.roundTrip)
	if err == nil {
		// if remote store successfully set up, try and get root from remote
		rootJSON, err = remote.GetMeta("root", maxSize)
	}

	// if remote store couldn't be setup, or we failed to get a root from it
	// load the root from cache (offline operation)
	if err != nil {
		if err, ok := err.(store.ErrMetaNotFound); ok {
			// if the error was MetaNotFound then we successfully contacted
			// the store and it doesn't know about the repo.
			return nil, err
		}
		result, cacheErr := r.fileStore.GetMeta("root", maxSize)
		if cacheErr != nil {
			// if cache didn't return a root, we cannot proceed - just return
			// the original error.
			return nil, err
		}
		rootJSON = result
		logrus.Debugf(
			"Using local cache instead of remote due to failure: %s", err.Error())
	}
	// can't just unmarshal into SignedRoot because validate root
	// needs the root.Signed field to still be []byte for signature
	// validation
	root := &data.Signed{}
	err = json.Unmarshal(rootJSON, root)
	if err != nil {
		return nil, err
	}

	err = r.CertManager.ValidateRoot(root, r.gun)
	if err != nil {
		return nil, err
	}

	kdb := keys.NewDB()
	r.tufRepo = tuf.NewRepo(kdb, r.CryptoService)

	signedRoot, err := data.RootFromSigned(root)
	if err != nil {
		return nil, err
	}
	err = r.tufRepo.SetRoot(signedRoot)
	if err != nil {
		return nil, err
	}

	return tufclient.NewClient(
		r.tufRepo,
		remote,
		kdb,
		r.fileStore,
	), nil
}

// RotateKey rotates the key for a role - this can invalidate that role's metadata
// if it is not signed by that key.  Particularly if the key being rotated is the
// root key, because it is not signed by the new key, only the old key.
func (m *MetadataSwizzler) RotateKey(role string, key data.PublicKey) error {
	roleSpecifier := data.CanonicalRootRole
	if data.IsDelegation(role) {
		roleSpecifier = path.Dir(role)
	}

	b, err := m.MetadataCache.GetSized(roleSpecifier, store.NoSizeLimit)
	if err != nil {
		return err
	}

	signedThing := &data.Signed{}
	if err := json.Unmarshal(b, signedThing); err != nil {
		return err
	}

	// get keys before the keys are rotated
	pubKeys, err := getPubKeys(m.CryptoService, signedThing, roleSpecifier)
	if err != nil {
		return err
	}

	if roleSpecifier == data.CanonicalRootRole {
		signedRoot, err := data.RootFromSigned(signedThing)
		if err != nil {
			return err
		}
		signedRoot.Signed.Roles[role].KeyIDs = []string{key.ID()}
		signedRoot.Signed.Keys[key.ID()] = key
		if signedThing, err = signedRoot.ToSigned(); err != nil {
			return err
		}
	} else {
		signedTargets, err := data.TargetsFromSigned(signedThing, roleSpecifier)
		if err != nil {
			return err
		}
		for _, roleObject := range signedTargets.Signed.Delegations.Roles {
			if roleObject.Name == role {
				roleObject.KeyIDs = []string{key.ID()}
				break
			}
		}
		signedTargets.Signed.Delegations.Keys[key.ID()] = key
		if signedThing, err = signedTargets.ToSigned(); err != nil {
			return err
		}
	}

	metaBytes, err := serializeMetadata(m.CryptoService, signedThing, roleSpecifier, pubKeys...)
	if err != nil {
		return err
	}
	return m.MetadataCache.Set(roleSpecifier, metaBytes)
}

// SetThreshold sets a threshold for a metadata role - can invalidate metadata for which
// the threshold is increased, if there aren't enough signatures or can be invalid because
// the threshold is 0
func (m *MetadataSwizzler) SetThreshold(role string, newThreshold int) error {
	roleSpecifier := data.CanonicalRootRole
	if data.IsDelegation(role) {
		roleSpecifier = path.Dir(role)
	}

	b, err := m.MetadataCache.GetSized(roleSpecifier, store.NoSizeLimit)
	if err != nil {
		return err
	}

	signedThing := &data.Signed{}
	if err := json.Unmarshal(b, signedThing); err != nil {
		return err
	}

	if roleSpecifier == data.CanonicalRootRole {
		signedRoot, err := data.RootFromSigned(signedThing)
		if err != nil {
			return err
		}
		signedRoot.Signed.Roles[role].Threshold = newThreshold
		if signedThing, err = signedRoot.ToSigned(); err != nil {
			return err
		}
	} else {
		signedTargets, err := data.TargetsFromSigned(signedThing, roleSpecifier)
		if err != nil {
			return err
		}
		for _, roleObject := range signedTargets.Signed.Delegations.Roles {
			if roleObject.Name == role {
				roleObject.Threshold = newThreshold
				break
			}
		}
		if signedThing, err = signedTargets.ToSigned(); err != nil {
			return err
		}
	}

	var metaBytes []byte
	pubKeys, err := getPubKeys(m.CryptoService, signedThing, roleSpecifier)
	if err == nil {
		metaBytes, err = serializeMetadata(m.CryptoService, signedThing, roleSpecifier, pubKeys...)
	}

	if err != nil {
		return err
	}
	return m.MetadataCache.Set(roleSpecifier, metaBytes)
}

func (c Client) verifyRoot(role string, s *data.Signed, minVersion int) error {
	// this will confirm that the root has been signed by the old root role
	// with the root keys we bootstrapped with.
	// Still need to determine if there has been a root key update and
	// confirm signature with new root key
	logrus.Debug("verifying root with existing keys")
	rootRole, err := c.local.GetBaseRole(role)
	if err != nil {
		logrus.Debug("no previous root role loaded")
		return err
	}
	// Verify using the rootRole loaded from the known root.json
	if err = signed.Verify(s, rootRole, minVersion); err != nil {
		logrus.Debug("root did not verify with existing keys")
		return err
	}

	logrus.Debug("updating known root roles and keys")
	root, err := data.RootFromSigned(s)
	if err != nil {
		logrus.Error(err.Error())
		return err
	}
	// replace the existing root.json with the new one (just in memory, we
	// have another validation step before we fully accept the new root)
	err = c.local.SetRoot(root)
	if err != nil {
		logrus.Error(err.Error())
		return err
	}
	// Verify the new root again having loaded the rootRole out of this new
	// file (verifies self-referential integrity)
	// TODO(endophage): be more intelligent and only re-verify if we detect
	//                  there has been a change in root keys
	logrus.Debug("verifying root with updated keys")
	rootRole, err = c.local.GetBaseRole(role)
	if err != nil {
		logrus.Debug("root role with new keys not loaded")
		return err
	}
	err = signed.Verify(s, rootRole, minVersion)
	if err != nil {
		logrus.Debug("root did not verify with new keys")
		return err
	}
	logrus.Debug("successfully verified root")
	return nil
}

// validateRoot MUST only be used during bootstrapping. It will only validate
// signatures of the root based on known keys, not expiry or other metadata.
// This is so that an out of date root can be loaded to be used in a rotation
// should the TUF update process detect a problem.
func (r *NotaryRepository) validateRoot(rootJSON []byte) (*data.SignedRoot, error) {
	// can't just unmarshal into SignedRoot because validate root
	// needs the root.Signed field to still be []byte for signature
	// validation
	root := &data.Signed{}
	err := json.Unmarshal(rootJSON, root)
	if err != nil {
		return nil, err
	}

	err = r.CertManager.ValidateRoot(root, r.gun)
	if err != nil {
		return nil, err
	}

	return data.RootFromSigned(root)
}

func TestValidateRootRotation(t *testing.T) {
	repo, crypto, err := testutils.EmptyRepo("docker.com/notary")
	assert.NoError(t, err)
	store := storage.NewMemStorage()

	r, tg, sn, ts, err := testutils.Sign(repo)
	assert.NoError(t, err)
	root, targets, snapshot, timestamp, err := getUpdates(r, tg, sn, ts)
	assert.NoError(t, err)

	store.UpdateCurrent("testGUN", root)

	oldRootRole := repo.Root.Signed.Roles["root"]
	oldRootKey := repo.Root.Signed.Keys[oldRootRole.KeyIDs[0]]

	rootKey, err := crypto.Create("root", data.ED25519Key)
	assert.NoError(t, err)
	rootRole, err := data.NewRole("root", 1, []string{rootKey.ID()}, nil)
	assert.NoError(t, err)

	delete(repo.Root.Signed.Keys, oldRootRole.KeyIDs[0])

	repo.Root.Signed.Roles["root"] = &rootRole.RootRole
	repo.Root.Signed.Keys[rootKey.ID()] = rootKey

	r, err = repo.SignRoot(data.DefaultExpires(data.CanonicalRootRole))
	assert.NoError(t, err)
	err = signed.Sign(crypto, r, rootKey, oldRootKey)
	assert.NoError(t, err)

	rt, err := data.RootFromSigned(r)
	assert.NoError(t, err)
	repo.SetRoot(rt)

	sn, err = repo.SignSnapshot(data.DefaultExpires(data.CanonicalSnapshotRole))
	assert.NoError(t, err)
	root, targets, snapshot, timestamp, err = getUpdates(r, tg, sn, ts)
	assert.NoError(t, err)

	updates := []storage.MetaUpdate{root, targets, snapshot, timestamp}

	copyTimestampKey(t, repo, store, "testGUN")
	_, err = validateUpdate(crypto, "testGUN", updates, store)
	assert.NoError(t, err)
}

func TestValidateRootFailuresWithPinnedCert(t *testing.T) {
	var testSignedRoot data.Signed
	var signedRootBytes bytes.Buffer

	// Temporary directory where test files will be created
	tempBaseDir, err := ioutil.TempDir("", "notary-test-")
	defer os.RemoveAll(tempBaseDir)
	require.NoError(t, err, "failed to create a temporary directory: %s", err)

	// Execute our template
	templ, _ := template.New("SignedRSARootTemplate").Parse(signedRSARootTemplate)
	templ.Execute(&signedRootBytes, SignedRSARootTemplate{RootPem: validPEMEncodedRSARoot})

	// Unmarshal our signedroot
	json.Unmarshal(signedRootBytes.Bytes(), &testSignedRoot)
	typedSignedRoot, err := data.RootFromSigned(&testSignedRoot)
	require.NoError(t, err)

	// This call to trustpinning.ValidateRoot should fail due to an incorrect cert ID
	_, err = trustpinning.ValidateRoot(nil, &testSignedRoot, "docker.com/notary", trustpinning.TrustPinConfig{Certs: map[string][]string{"docker.com/notary": {"ABSOLUTELY NOT A CERT ID"}}, DisableTOFU: true})
	require.Error(t, err)

	// This call to trustpinning.ValidateRoot should fail due to an empty cert ID
	_, err = trustpinning.ValidateRoot(nil, &testSignedRoot, "docker.com/notary", trustpinning.TrustPinConfig{Certs: map[string][]string{"docker.com/notary": {""}}, DisableTOFU: true})
	require.Error(t, err)

	// This call to trustpinning.ValidateRoot should fail due to an invalid GUN (even though the cert ID is correct), and TOFUS is set to false
	_, err = trustpinning.ValidateRoot(nil, &testSignedRoot, "docker.com/notary", trustpinning.TrustPinConfig{Certs: map[string][]string{"not_a_gun": {rootPubKeyID}}, DisableTOFU: true})
	require.Error(t, err)

	// This call to trustpinning.ValidateRoot should fail due to an invalid cert ID, even though it's a valid key ID for targets
	_, err = trustpinning.ValidateRoot(nil, &testSignedRoot, "docker.com/notary", trustpinning.TrustPinConfig{Certs: map[string][]string{"docker.com/notary": {targetsPubKeyID}}, DisableTOFU: true})
	require.Error(t, err)

	// This call to trustpinning.ValidateRoot should succeed because we fall through to TOFUS because we have no matching GUNs under Certs
	validatedRoot, err := trustpinning.ValidateRoot(nil, &testSignedRoot, "docker.com/notary", trustpinning.TrustPinConfig{Certs: map[string][]string{"not_a_gun": {rootPubKeyID}}, DisableTOFU: false})
	require.NoError(t, err)
	generateRootKeyIDs(typedSignedRoot)
	require.Equal(t, typedSignedRoot, validatedRoot)
}

func (c Client) verifyRoot(role string, s *data.Signed, minVersion int) error {
	// this will confirm that the root has been signed by the old root role
	// as c.keysDB contains the root keys we bootstrapped with.
	// Still need to determine if there has been a root key update and
	// confirm signature with new root key
	logrus.Debug("verifying root with existing keys")
	err := signed.Verify(s, role, minVersion, c.keysDB)
	if err != nil {
		logrus.Debug("root did not verify with existing keys")
		return err
	}

	// This will cause keyDB to get updated, overwriting any keyIDs associated
	// with the roles in root.json
	logrus.Debug("updating known root roles and keys")
	root, err := data.RootFromSigned(s)
	if err != nil {
		logrus.Error(err.Error())
		return err
	}
	err = c.local.SetRoot(root)
	if err != nil {
		logrus.Error(err.Error())
		return err
	}
	// verify again now that the old keys have been replaced with the new keys.
	// TODO(endophage): be more intelligent and only re-verify if we detect
	//                  there has been a change in root keys
	logrus.Debug("verifying root with updated keys")
	err = signed.Verify(s, role, minVersion, c.keysDB)
	if err != nil {
		logrus.Debug("root did not verify with new keys")
		return err
	}
	logrus.Debug("successfully verified root")
	return nil
}

/*
ValidateRoot receives a new root, validates its correctness and attempts to
do root key rotation if needed.

First we list the current trusted certificates we have for a particular GUN. If
that list is non-empty means that we've already seen this repository before, and
have a list of trusted certificates for it. In this case, we use this list of
certificates to attempt to validate this root file.

If the previous validation succeeds, we check the integrity of the root by
making sure that it is validated by itself. This means that we will attempt to
validate the root data with the certificates that are included in the root keys
themselves.

However, if we do not have any current trusted certificates for this GUN, we
check if there are any pinned certificates specified in the trust_pinning section
of the notary client config.  If this section specifies a Certs section with this
GUN, we attempt to validate that the certificates present in the downloaded root
file match the pinned ID.

If the Certs section is empty for this GUN, we check if the trust_pinning
section specifies a CA section specified in the config for this GUN.  If so, we check
that the specified CA is valid and has signed a certificate included in the downloaded
root file.  The specified CA can be a prefix for this GUN.

If both the Certs and CA configs do not match this GUN, we fall back to the TOFU
section in the config: if true, we trust certificates specified in the root for
this GUN. If later we see a different certificate for that certificate, we return
an ErrValidationFailed error.

Note that since we only allow trust data to be downloaded over an HTTPS channel
we are using the current public PKI to validate the first download of the certificate
adding an extra layer of security over the normal (SSH style) trust model.
We shall call this: TOFUS.

Validation failure at any step will result in an ErrValidationFailed error.
*/
func ValidateRoot(certStore trustmanager.X509Store, root *data.Signed, gun string, trustPinning TrustPinConfig) error {
	logrus.Debugf("entered ValidateRoot with dns: %s", gun)
	signedRoot, err := data.RootFromSigned(root)
	if err != nil {
		return err
	}

	rootRole, err := signedRoot.BuildBaseRole(data.CanonicalRootRole)
	if err != nil {
		return err
	}

	// Retrieve all the leaf and intermediate certificates in root for which the CN matches the GUN
	allLeafCerts, allIntCerts := parseAllCerts(signedRoot)
	certsFromRoot, err := validRootLeafCerts(allLeafCerts, gun)
	if err != nil {
		logrus.Debugf("error retrieving valid leaf certificates for: %s, %v", gun, err)
		return &ErrValidationFail{Reason: "unable to retrieve valid leaf certificates"}
	}

	// Retrieve all the trusted certificates that match this gun
	trustedCerts, err := certStore.GetCertificatesByCN(gun)
	if err != nil {
		// If the error that we get back is different than ErrNoCertificatesFound
		// we couldn't check if there are any certificates with this CN already
		// trusted. Let's take the conservative approach and return a failed validation
		if _, ok := err.(*trustmanager.ErrNoCertificatesFound); !ok {
			logrus.Debugf("error retrieving trusted certificates for: %s, %v", gun, err)
			return &ErrValidationFail{Reason: "unable to retrieve trusted certificates"}
		}
	}
	// If we have certificates that match this specific GUN, let's make sure to
	// use them first to validate that this new root is valid.
	if len(trustedCerts) != 0 {
		logrus.Debugf("found %d valid root certificates for %s: %s", len(trustedCerts), gun,
			prettyFormatCertIDs(trustedCerts))
		err = signed.VerifySignatures(
			root, data.BaseRole{Keys: trustmanager.CertsToKeys(trustedCerts, allIntCerts), Threshold: 1})
		if err != nil {
			logrus.Debugf("failed to verify TUF data for: %s, %v", gun, err)
			return &ErrValidationFail{Reason: "failed to validate data with current trusted certificates"}
		}
	} else {
		logrus.Debugf("found no currently valid root certificates for %s, using trust_pinning config to bootstrap trust", gun)
		trustPinCheckFunc, err := NewTrustPinChecker(trustPinning, gun)
		if err != nil {
			return &ErrValidationFail{Reason: err.Error()}
		}

		validPinnedCerts := []*x509.Certificate{}
		for _, cert := range certsFromRoot {
			certID, err := trustmanager.FingerprintCert(cert)
			if err != nil {
				continue
			}
			if ok := trustPinCheckFunc(cert, allIntCerts[certID]); !ok {
				continue
			}
			validPinnedCerts = append(validPinnedCerts, cert)
		}
		if len(validPinnedCerts) == 0 {
			return &ErrValidationFail{Reason: "unable to match any certificates to trust_pinning config"}
		}
//.........这里部分代码省略.........

// checkRoot returns true if no rotation, or a valid
// rotation has taken place, and the threshold number of signatures
// are valid.
func checkRoot(oldRoot, newRoot *data.SignedRoot) error {
	rootRole := data.RoleName(data.CanonicalRootRole)
	targetsRole := data.RoleName(data.CanonicalTargetsRole)
	snapshotRole := data.RoleName(data.CanonicalSnapshotRole)
	timestampRole := data.RoleName(data.CanonicalTimestampRole)

	var oldRootRole *data.RootRole
	newRootRole, ok := newRoot.Signed.Roles[rootRole]
	if !ok {
		return errors.New("new root is missing role entry for root role")
	}

	oldThreshold := 1
	rotation := false
	oldKeys := map[string]data.PublicKey{}
	newKeys := map[string]data.PublicKey{}
	if oldRoot != nil {
		// check for matching root key IDs
		oldRootRole = oldRoot.Signed.Roles[rootRole]
		oldThreshold = oldRootRole.Threshold

		for _, kid := range oldRootRole.KeyIDs {
			k, ok := oldRoot.Signed.Keys[kid]
			if !ok {
				// if the key itself wasn't contained in the root
				// we're skipping it because it could never have
				// been used to validate this root.
				continue
			}
			oldKeys[kid] = data.NewPublicKey(k.Algorithm(), k.Public())
		}

		// super simple check for possible rotation
		rotation = len(oldKeys) != len(newRootRole.KeyIDs)
	}
	// if old and new had the same number of keys, iterate
	// to see if there's a difference.
	for _, kid := range newRootRole.KeyIDs {
		k, ok := newRoot.Signed.Keys[kid]
		if !ok {
			// if the key itself wasn't contained in the root
			// we're skipping it because it could never have
			// been used to validate this root.
			continue
		}
		newKeys[kid] = data.NewPublicKey(k.Algorithm(), k.Public())

		if oldRoot != nil {
			if _, ok := oldKeys[kid]; !ok {
				// if there is any difference in keys, a key rotation may have
				// occurred.
				rotation = true
			}
		}
	}
	newSigned, err := newRoot.ToSigned()
	if err != nil {
		return err
	}
	if rotation {
		err = signed.VerifyRoot(newSigned, oldThreshold, oldKeys)
		if err != nil {
			return fmt.Errorf("rotation detected and new root was not signed with at least %d old keys", oldThreshold)
		}
	}
	err = signed.VerifyRoot(newSigned, newRootRole.Threshold, newKeys)
	if err != nil {
		return err
	}
	root, err := data.RootFromSigned(newSigned)
	if err != nil {
		return err
	}
	// at a minimum, check the 4 required roles are present
	for _, r := range []string{rootRole, targetsRole, snapshotRole, timestampRole} {
		role, ok := root.Signed.Roles[r]
		if !ok {
			return fmt.Errorf("missing required %s role from root", r)
		}
		if role.Threshold < 1 {
			return fmt.Errorf("%s role has invalid threshold", r)
		}
		if len(role.KeyIDs) < role.Threshold {
			return fmt.Errorf("%s role has insufficient number of keys", r)
		}
	}
	return nil
}

// downloadRoot is responsible for downloading the root.json
func (c *Client) downloadRoot() error {
	role := data.RoleName("root")
	size := maxSize
	var expectedSha256 []byte
	if c.local.Snapshot != nil {
		size = c.local.Snapshot.Signed.Meta[role].Length
		expectedSha256 = c.local.Snapshot.Signed.Meta[role].Hashes["sha256"]
	}

	// if we're bootstrapping we may not have a cached root, an
	// error will result in the "previous root version" being
	// interpreted as 0.
	var download bool
	var err error
	var cachedRoot []byte
	old := &data.Signed{}
	version := 0

	if expectedSha256 != nil {
		// can only trust cache if we have an expected sha256 to trust
		cachedRoot, err = c.cache.GetMeta(role, size)
	}

	if cachedRoot == nil || err != nil {
		logrus.Debug("didn't find a cached root, must download")
		download = true
	} else {
		hash := sha256.Sum256(cachedRoot)
		if !bytes.Equal(hash[:], expectedSha256) {
			logrus.Debug("cached root's hash didn't match expected, must download")
			download = true
		}
		err := json.Unmarshal(cachedRoot, old)
		if err == nil {
			root, err := data.RootFromSigned(old)
			if err == nil {
				version = root.Signed.Version
			} else {
				logrus.Debug("couldn't parse Signed part of cached root, must download")
				download = true
			}
		} else {
			logrus.Debug("couldn't parse cached root, must download")
			download = true
		}
	}
	var s *data.Signed
	var raw []byte
	if download {
		raw, s, err = c.downloadSigned(role, size, expectedSha256)
		if err != nil {
			return err
		}
	} else {
		logrus.Debug("using cached root")
		s = old
	}
	if err := c.verifyRoot(role, s, version); err != nil {
		return err
	}
	if download {
		logrus.Debug("caching downloaded root")
		// Now that we have accepted new root, write it to cache
		if err = c.cache.SetMeta(role, raw); err != nil {
			logrus.Errorf("Failed to write root to local cache: %s", err.Error())
		}
	}
	return nil
}

func TestValidateRootRotation(t *testing.T) {
	_, repo, crypto := testutils.EmptyRepo()
	store := storage.NewMemStorage()

	r, tg, sn, ts, err := testutils.Sign(repo)
	assert.NoError(t, err)
	root, targets, snapshot, timestamp, err := testutils.Serialize(r, tg, sn, ts)
	assert.NoError(t, err)

	store.UpdateCurrent(
		"testGUN",
		storage.MetaUpdate{
			Role:    "root",
			Version: 1,
			Data:    root,
		},
	)

	oldRootRole := repo.Root.Signed.Roles["root"]
	oldRootKey := repo.Root.Signed.Keys[oldRootRole.KeyIDs[0]]

	rootKey, err := crypto.Create("root", data.ED25519Key)
	assert.NoError(t, err)
	rootRole, err := data.NewRole("root", 1, []string{rootKey.ID()}, nil, nil)
	assert.NoError(t, err)

	delete(repo.Root.Signed.Keys, oldRootRole.KeyIDs[0])

	repo.Root.Signed.Roles["root"] = &rootRole.RootRole
	repo.Root.Signed.Keys[rootKey.ID()] = rootKey

	r, err = repo.SignRoot(data.DefaultExpires(data.CanonicalRootRole))
	assert.NoError(t, err)
	err = signed.Sign(crypto, r, rootKey, oldRootKey)
	assert.NoError(t, err)

	rt, err := data.RootFromSigned(r)
	assert.NoError(t, err)
	repo.SetRoot(rt)

	sn, err = repo.SignSnapshot(data.DefaultExpires(data.CanonicalSnapshotRole))
	assert.NoError(t, err)
	root, targets, snapshot, timestamp, err = testutils.Serialize(r, tg, sn, ts)
	assert.NoError(t, err)

	updates := []storage.MetaUpdate{
		{
			Role:    "root",
			Version: 1,
			Data:    root,
		},
		{
			Role:    "targets",
			Version: 1,
			Data:    targets,
		},
		{
			Role:    "snapshot",
			Version: 1,
			Data:    snapshot,
		},
		{
			Role:    "timestamp",
			Version: 1,
			Data:    timestamp,
		},
	}

	err = validateUpdate("testGUN", updates, store)
	assert.NoError(t, err)
}

/*
ValidateRoot receives a new root, validates its correctness and attempts to
do root key rotation if needed.

First we check if we have any trusted certificates for a particular GUN in
a previous root, if we have one. If the previous root is not nil and we find
certificates for this GUN, we've already seen this repository before, and
have a list of trusted certificates for it. In this case, we use this list of
certificates to attempt to validate this root file.

If the previous validation succeeds, we check the integrity of the root by
making sure that it is validated by itself. This means that we will attempt to
validate the root data with the certificates that are included in the root keys
themselves.

However, if we do not have any current trusted certificates for this GUN, we
check if there are any pinned certificates specified in the trust_pinning section
of the notary client config.  If this section specifies a Certs section with this
GUN, we attempt to validate that the certificates present in the downloaded root
file match the pinned ID.

If the Certs section is empty for this GUN, we check if the trust_pinning
section specifies a CA section specified in the config for this GUN.  If so, we check
that the specified CA is valid and has signed a certificate included in the downloaded
root file.  The specified CA can be a prefix for this GUN.

If both the Certs and CA configs do not match this GUN, we fall back to the TOFU
section in the config: if true, we trust certificates specified in the root for
this GUN. If later we see a different certificate for that certificate, we return
an ErrValidationFailed error.

Note that since we only allow trust data to be downloaded over an HTTPS channel
we are using the current public PKI to validate the first download of the certificate
adding an extra layer of security over the normal (SSH style) trust model.
We shall call this: TOFUS.

Validation failure at any step will result in an ErrValidationFailed error.
*/
func ValidateRoot(prevRoot *data.SignedRoot, root *data.Signed, gun string, trustPinning TrustPinConfig) (*data.SignedRoot, error) {
	logrus.Debugf("entered ValidateRoot with dns: %s", gun)
	signedRoot, err := data.RootFromSigned(root)
	if err != nil {
		return nil, err
	}

	rootRole, err := signedRoot.BuildBaseRole(data.CanonicalRootRole)
	if err != nil {
		return nil, err
	}

	// Retrieve all the leaf and intermediate certificates in root for which the CN matches the GUN
	allLeafCerts, allIntCerts := parseAllCerts(signedRoot)
	certsFromRoot, err := validRootLeafCerts(allLeafCerts, gun, true)
	validIntCerts := validRootIntCerts(allIntCerts)

	if err != nil {
		logrus.Debugf("error retrieving valid leaf certificates for: %s, %v", gun, err)
		return nil, &ErrValidationFail{Reason: "unable to retrieve valid leaf certificates"}
	}

	logrus.Debugf("found %d leaf certs, of which %d are valid leaf certs for %s", len(allLeafCerts), len(certsFromRoot), gun)

	// If we have a previous root, let's try to use it to validate that this new root is valid.
	havePrevRoot := prevRoot != nil
	if havePrevRoot {
		// Retrieve all the trusted certificates from our previous root
		// Note that we do not validate expiries here since our originally trusted root might have expired certs
		allTrustedLeafCerts, allTrustedIntCerts := parseAllCerts(prevRoot)
		trustedLeafCerts, err := validRootLeafCerts(allTrustedLeafCerts, gun, false)
		if err != nil {
			return nil, &ErrValidationFail{Reason: "could not retrieve trusted certs from previous root role data"}
		}

		// Use the certificates we found in the previous root for the GUN to verify its signatures
		// This could potentially be an empty set, in which case we will fail to verify
		logrus.Debugf("found %d valid root leaf certificates for %s: %s", len(trustedLeafCerts), gun,
			prettyFormatCertIDs(trustedLeafCerts))

		// Extract the previous root's threshold for signature verification
		prevRootRoleData, ok := prevRoot.Signed.Roles[data.CanonicalRootRole]
		if !ok {
			return nil, &ErrValidationFail{Reason: "could not retrieve previous root role data"}
		}
		err = signed.VerifySignatures(
			root, data.BaseRole{Keys: utils.CertsToKeys(trustedLeafCerts, allTrustedIntCerts), Threshold: prevRootRoleData.Threshold})
		if err != nil {
			logrus.Debugf("failed to verify TUF data for: %s, %v", gun, err)
			return nil, &ErrRootRotationFail{Reason: "failed to validate data with current trusted certificates"}
		}
		// Clear the IsValid marks we could have received from VerifySignatures
		for i := range root.Signatures {
			root.Signatures[i].IsValid = false
		}
	}

	// Regardless of having a previous root or not, confirm that the new root validates against the trust pinning
	logrus.Debugf("checking root against trust_pinning config for %s", gun)
	trustPinCheckFunc, err := NewTrustPinChecker(trustPinning, gun, !havePrevRoot)
	if err != nil {
		return nil, &ErrValidationFail{Reason: err.Error()}
//.........这里部分代码省略.........