Attestation & Identity & Global Unlock & Enrolment
This changes the node startup sequence significantly. Now the following three startup procedures replace the old setup/join mechanic:
* If no enrolment config is present, automatically bootstrap a new cluster and become master for it.
* If an enrolment config with an enrolment token is present, register with the NodeManagementService.
* If an enrolment config without an enrolment token is present, attempt a normal cluster unlock.
It also completely revamps the GRPC management services:
* NodeManagementService is a master-only service that deals with other nodes and has a cluster-wide identity
* NodeService is only available in unlocked state and keyed with the node identity
* ClusterManagement is now a master-only service that's been spun out of the main NMS since they have very different authentication models and also deals with EnrolmentConfigs
The TPM support library has also been extended by:
* Lots of integrity attestation and verification functions
* Built-in AK management
* Some advanced policy-based authentication stuff
Also contains various enhancements to the network service to make everything work in a proper multi-node environment.
Lots of old code has been thrown out.
Test Plan: Passed a full manual test of all three startup modes (bootstrap, enrolment and normal unlock) including automated EnrolmentConfig generation and consumption in a dual-node configuration on swtpm / OVMF.
Bug: T499
X-Origin-Diff: phab/D291
GitOrigin-RevId: d53755c828218b1df83a1d7ad252c7b3231abca8
diff --git a/core/internal/api/nodemanagement.go b/core/internal/api/nodemanagement.go
new file mode 100644
index 0000000..4268a0f
--- /dev/null
+++ b/core/internal/api/nodemanagement.go
@@ -0,0 +1,279 @@
+// Copyright 2020 The Monogon Project Authors.
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package api
+
+import (
+ "bytes"
+ "context"
+ "crypto/ed25519"
+ "crypto/rand"
+ "crypto/sha256"
+ "crypto/subtle"
+ "crypto/x509"
+ "encoding/base64"
+ "errors"
+ "fmt"
+ "io"
+
+ "git.monogon.dev/source/nexantic.git/core/generated/api"
+ "git.monogon.dev/source/nexantic.git/core/pkg/tpm"
+ "github.com/gogo/protobuf/proto"
+ "go.etcd.io/etcd/clientv3"
+ "go.uber.org/zap"
+ "google.golang.org/grpc/codes"
+ "google.golang.org/grpc/status"
+)
+
+const nodesPrefix = "nodes/"
+const enrolmentsPrefix = "enrolments/"
+
+func nodeId(idCert []byte) (string, error) {
+ // Currently we only identify nodes by ID key
+ cert, err := x509.ParseCertificate(idCert)
+ if err != nil {
+ return "", err
+ }
+ pubKey, ok := cert.PublicKey.(ed25519.PublicKey)
+ if !ok {
+ return "", errors.New("invalid node identity certificate")
+ }
+
+ return "smalltown-" + base64.RawStdEncoding.EncodeToString([]byte(pubKey)), nil
+}
+
+func (s *Server) registerNewNode(node *api.Node) error {
+ nodeRaw, err := proto.Marshal(node)
+ if err != nil {
+ return err
+ }
+
+ nodeID, err := nodeId(node.IdCert)
+ if err != nil {
+ return err
+ }
+
+ key := nodesPrefix + nodeID
+
+ // Overwriting nodes is a BadIdea(TM), so make this a Compare-and-Swap
+ res, err := s.getStore().Txn(context.Background()).If(
+ clientv3.Compare(clientv3.CreateRevision(key), "=", 0),
+ ).Then(
+ clientv3.OpPut(key, string(nodeRaw)),
+ ).Commit()
+ if err != nil {
+ return fmt.Errorf("failed to store new node: %w", err)
+ }
+ if !res.Succeeded {
+ s.Logger.Warn("double-registration of node attempted", zap.String("node", nodeID))
+ }
+ return nil
+}
+
+func (s *Server) TPM2BootstrapNode(newNodeInfo *api.NewNodeInfo) (*api.Node, error) {
+ akPublic, err := tpm.GetAKPublic()
+ if err != nil {
+ return nil, err
+ }
+ ekPubkey, ekCert, err := tpm.GetEKPublic()
+ if err != nil {
+ return nil, err
+ }
+ return &api.Node{
+ Address: newNodeInfo.Ip,
+ Integrity: &api.Node_Tpm2{Tpm2: &api.NodeTPM2{
+ AkPub: akPublic,
+ EkCert: ekCert,
+ EkPubkey: ekPubkey,
+ }},
+ GlobalUnlockKey: newNodeInfo.GlobalUnlockKey,
+ IdCert: newNodeInfo.IdCert,
+ State: api.Node_MASTER,
+ }, nil
+}
+
+func (s *Server) TPM2Unlock(unlockServer api.NodeManagementService_TPM2UnlockServer) error {
+ nonce := make([]byte, 32)
+ if _, err := io.ReadFull(rand.Reader, nonce); err != nil {
+ return status.Error(codes.Unavailable, "failed to get randonmess")
+ }
+ if err := unlockServer.Send(&api.TPM2UnlockFlowResponse{
+ Stage: &api.TPM2UnlockFlowResponse_UnlockInit{
+ UnlockInit: &api.TPM2UnlockInit{
+ Nonce: nonce,
+ },
+ },
+ }); err != nil {
+ return err
+ }
+ unlockReqContainer, err := unlockServer.Recv()
+ if err != nil {
+ return err
+ }
+ unlockReqVariant, ok := unlockReqContainer.Stage.(*api.TPM2UnlockFlowRequeset_UnlockRequest)
+ if !ok {
+ return status.Errorf(codes.InvalidArgument, "protocol violation")
+ }
+ unlockRequest := unlockReqVariant.UnlockRequest
+
+ store := s.getStore()
+ // This is safe, etcd does not do relative paths
+ path := nodesPrefix + unlockRequest.NodeId
+ nodeRes, err := store.Get(unlockServer.Context(), path)
+ if err != nil {
+ return status.Error(codes.Unavailable, "consensus request failed")
+ }
+ if nodeRes.Count == 0 {
+ return status.Error(codes.NotFound, "this node does not exist")
+ } else if nodeRes.Count > 1 {
+ panic("invariant violation: more than one node with the same id")
+ }
+ nodeRaw := nodeRes.Kvs[0].Value
+ var node api.Node
+ if err := proto.Unmarshal(nodeRaw, &node); err != nil {
+ s.Logger.Error("Failed to decode node", zap.Error(err))
+ return status.Error(codes.Internal, "invalid node")
+ }
+
+ nodeTPM2, ok := node.Integrity.(*api.Node_Tpm2)
+ if !ok {
+ return status.Error(codes.InvalidArgument, "node not integrity-protected with TPM2")
+ }
+
+ validQuote, err := tpm.VerifyAttestPlatform(nonce, nodeTPM2.Tpm2.AkPub, unlockRequest.Quote, unlockRequest.QuoteSignature)
+ if err != nil {
+ return status.Error(codes.PermissionDenied, "invalid quote")
+ }
+
+ pcrHash := sha256.New()
+ for _, pcr := range unlockRequest.Pcrs {
+ pcrHash.Write(pcr)
+ }
+ expectedPCRHash := pcrHash.Sum(nil)
+
+ if !bytes.Equal(validQuote.AttestedQuoteInfo.PCRDigest, expectedPCRHash) {
+ return status.Error(codes.InvalidArgument, "the quote's PCR hash does not match the supplied PCRs")
+ }
+
+ // TODO: Plug in policy engine to decide if the unlock should actually happen
+
+ return unlockServer.Send(&api.TPM2UnlockFlowResponse{Stage: &api.TPM2UnlockFlowResponse_UnlockResponse{
+ UnlockResponse: &api.TPM2UnlockResponse{
+ GlobalUnlockKey: node.GlobalUnlockKey,
+ },
+ }})
+}
+
+func (s *Server) NewTPM2NodeRegister(registerServer api.NodeManagementService_NewTPM2NodeRegisterServer) error {
+ registerReqContainer, err := registerServer.Recv()
+ if err != nil {
+ return err
+ }
+ registerReqVariant, ok := registerReqContainer.Stage.(*api.TPM2FlowRequest_Register)
+ if !ok {
+ return status.Error(codes.InvalidArgument, "protocol violation")
+ }
+ registerReq := registerReqVariant.Register
+
+ challengeNonce := make([]byte, 32)
+ if _, err := io.ReadFull(rand.Reader, challengeNonce); err != nil {
+ return status.Error(codes.Unavailable, "failed to get randonmess")
+ }
+ challenge, challengeBlob, err := tpm.MakeAKChallenge(registerReq.EkPubkey, registerReq.AkPublic, challengeNonce)
+ if err != nil {
+ return status.Errorf(codes.InvalidArgument, "failed to challenge AK: %v", err)
+ }
+ nonce := make([]byte, 32)
+ if _, err := io.ReadFull(rand.Reader, nonce); err != nil {
+ return status.Error(codes.Unavailable, "failed to get randonmess")
+ }
+ if err := registerServer.Send(&api.TPM2FlowResponse{Stage: &api.TPM2FlowResponse_AttestRequest{AttestRequest: &api.TPM2AttestRequest{
+ AkChallenge: challenge,
+ AkChallengeSecret: challengeBlob,
+ QuoteNonce: nonce,
+ }}}); err != nil {
+ return err
+ }
+ attestationResContainer, err := registerServer.Recv()
+ if err != nil {
+ return err
+ }
+ attestResVariant, ok := attestationResContainer.Stage.(*api.TPM2FlowRequest_AttestResponse)
+ if !ok {
+ return status.Error(codes.InvalidArgument, "protocol violation")
+ }
+ attestRes := attestResVariant.AttestResponse
+
+ if subtle.ConstantTimeCompare(attestRes.AkChallengeSolution, challengeNonce) != 1 {
+ return status.Error(codes.InvalidArgument, "invalid challenge response")
+ }
+
+ validQuote, err := tpm.VerifyAttestPlatform(nonce, registerReq.AkPublic, attestRes.Quote, attestRes.QuoteSignature)
+ if err != nil {
+ return status.Error(codes.PermissionDenied, "invalid quote")
+ }
+
+ pcrHash := sha256.New()
+ for _, pcr := range attestRes.Pcrs {
+ pcrHash.Write(pcr)
+ }
+ expectedPCRHash := pcrHash.Sum(nil)
+
+ if !bytes.Equal(validQuote.AttestedQuoteInfo.PCRDigest, expectedPCRHash) {
+ return status.Error(codes.InvalidArgument, "the quote's PCR hash does not match the supplied PCRs")
+ }
+
+ newNodeInfoContainer, err := registerServer.Recv()
+ newNodeInfoVariant, ok := newNodeInfoContainer.Stage.(*api.TPM2FlowRequest_NewNodeInfo)
+ newNodeInfo := newNodeInfoVariant.NewNodeInfo
+
+ store := s.getStore()
+ res, err := store.Get(registerServer.Context(), "enrolments/"+base64.RawURLEncoding.EncodeToString(newNodeInfo.EnrolmentConfig.EnrolmentSecret))
+ if err != nil {
+ return status.Error(codes.Unavailable, "Consensus unavailable")
+ }
+ if res.Count == 0 {
+ return status.Error(codes.PermissionDenied, "Invalid enrolment secret")
+ } else if res.Count > 1 {
+ panic("more than one value for the same key, bailing")
+ }
+ rawVal := res.Kvs[0].Value
+ var config api.EnrolmentConfig
+ if err := proto.Unmarshal(rawVal, &config); err != nil {
+ return err
+ }
+
+ // TODO: Plug in policy engine here
+
+ node := api.Node{
+ Address: newNodeInfo.Ip,
+ Integrity: &api.Node_Tpm2{Tpm2: &api.NodeTPM2{
+ AkPub: registerReq.AkPublic,
+ EkCert: registerReq.EkCert,
+ EkPubkey: registerReq.EkPubkey,
+ }},
+ GlobalUnlockKey: newNodeInfo.GlobalUnlockKey,
+ IdCert: newNodeInfo.IdCert,
+ State: api.Node_UNININITALIZED,
+ }
+
+ if err := s.registerNewNode(&node); err != nil {
+ s.Logger.Error("failed to register a node", zap.Error(err))
+ return status.Error(codes.Internal, "failed to register node")
+ }
+
+ return nil
+}