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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,114 @@ | ||
| // Copyright 2019 Google Inc. All Rights Reserved. | ||
| // | ||
| // 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 tracker tracks log roots and verifies consistency proofs between them. | ||
| package tracker | ||
|
|
||
| import ( | ||
| "sync" | ||
|
|
||
| "github.com/golang/glog" | ||
| "github.com/golang/protobuf/proto" | ||
| "github.com/google/trillian/types" | ||
| "google.golang.org/grpc/codes" | ||
| "google.golang.org/grpc/status" | ||
|
|
||
| pb "github.com/google/keytransparency/core/api/v1/keytransparency_go_proto" | ||
| tpb "github.com/google/trillian" | ||
| ) | ||
|
|
||
| // UpdateTrustedPredicate returns a bool indicating whether the local reference | ||
| // for the latest SignedLogRoot should be updated. | ||
| type UpdateTrustedPredicate func(cntRoot, newRoot types.LogRootV1) bool | ||
|
|
||
| // LogRootVerifier verifies a Trillian Log Root. | ||
| type LogRootVerifier interface { | ||
| // VerifyRoot checks the signature of newRoot and the consistency proof if trusted.TreeSize != 0. | ||
| VerifyRoot(trusted *types.LogRootV1, newRoot *tpb.SignedLogRoot, proof [][]byte) (*types.LogRootV1, error) | ||
| } | ||
|
|
||
| // LogTracker tracks a series of consistent log roots. | ||
| type LogTracker struct { | ||
| trusted types.LogRootV1 | ||
| v LogRootVerifier | ||
| updateTrusted UpdateTrustedPredicate | ||
| mu sync.RWMutex | ||
| } | ||
|
|
||
| // New creates a log tracker from no trusted root. | ||
| func New(lv LogRootVerifier) *LogTracker { | ||
| return NewFromSaved(lv, types.LogRootV1{}) | ||
| } | ||
|
|
||
| // NewFromSaved creates a log tracker from a previously saved trusted root. | ||
| func NewFromSaved(lv LogRootVerifier, lr types.LogRootV1) *LogTracker { | ||
| return &LogTracker{v: lv, trusted: lr, updateTrusted: isNewer} | ||
| } | ||
|
|
||
| // LastVerifiedLogRoot retrieves the tree size of the latest log root. | ||
| func (l *LogTracker) LastVerifiedLogRoot() *pb.LogRootRequest { | ||
| l.mu.RLock() | ||
| defer l.mu.RUnlock() | ||
| return l.logRootRequest() | ||
| } | ||
|
|
||
| func (l *LogTracker) logRootRequest() *pb.LogRootRequest { | ||
| return &pb.LogRootRequest{ | ||
| TreeSize: int64(l.trusted.TreeSize), | ||
| RootHash: l.trusted.RootHash, | ||
| } | ||
| } | ||
|
|
||
| // VerifyLogRoot verifies root and updates the trusted root if it is newer. | ||
| // state must be equal to the most recent value from LastVerifiedLogRoot(). | ||
| // If two clients race to VerifyLogRoot at the same time, if one of them updates the root, the other will fail. | ||
| func (l *LogTracker) VerifyLogRoot(state *pb.LogRootRequest, root *pb.LogRoot) (*types.LogRootV1, error) { | ||
| l.mu.Lock() | ||
| defer l.mu.Unlock() | ||
| if want := l.logRootRequest(); !proto.Equal(state, want) { | ||
| glog.Warningf("logtracker: unexpected logRootRequest: %v, want %v", state, want) | ||
| return nil, status.Errorf(codes.InvalidArgument, "out of order VerifyLogRoot(%v, _), want %v", state, want) | ||
| } | ||
|
|
||
| logRoot, err := l.v.VerifyRoot(&l.trusted, | ||
| root.GetLogRoot(), | ||
| root.GetLogConsistency()) | ||
| if err != nil { | ||
| return nil, err | ||
| } | ||
| if l.updateTrusted(l.trusted, *logRoot) { | ||
| l.trusted = *logRoot | ||
| glog.Infof("Trusted root updated to TreeSize %v", l.trusted.TreeSize) | ||
| } | ||
| return logRoot, nil | ||
| } | ||
|
|
||
| // SetUpdatePredicate allows relying parties to have finer grained control over when the trusted root is updated. | ||
| // It is legal to set the predicate at any time, but it makes the most sense to do so before any other calls. | ||
| func (l *LogTracker) SetUpdatePredicate(f UpdateTrustedPredicate) { | ||
| l.updateTrusted = f | ||
| } | ||
|
|
||
| // isNewer returns true when newRoot is newer than cntRoot. | ||
| func isNewer(cntRoot, newRoot types.LogRootV1) bool { | ||
| if newRoot.TreeSize > cntRoot.TreeSize { | ||
| return true | ||
| } | ||
| if newRoot.TreeSize == cntRoot.TreeSize && | ||
| newRoot.TimestampNanos > cntRoot.TimestampNanos { | ||
| return true | ||
| } | ||
| // The new root is older or smaller than the one we currently have. | ||
| return false | ||
| } |
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