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log_client.go
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log_client.go
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// Copyright 2017 Google LLC. 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 client verifies responses from the Trillian log.
package client
import (
"bytes"
"context"
"fmt"
"sort"
"sync"
"time"
"github.com/google/trillian"
"github.com/google/trillian/client/backoff"
"github.com/google/trillian/types"
"google.golang.org/grpc/codes"
"google.golang.org/grpc/status"
)
// LogClient represents a client for a given Trillian log instance.
type LogClient struct {
*LogVerifier
LogID int64
MinMergeDelay time.Duration
client trillian.TrillianLogClient
root types.LogRootV1
rootLock sync.Mutex
updateLock sync.Mutex
}
// New returns a new LogClient.
func New(logID int64, client trillian.TrillianLogClient, verifier *LogVerifier, root types.LogRootV1) *LogClient {
return &LogClient{
LogVerifier: verifier,
LogID: logID,
client: client,
root: root,
}
}
// NewFromTree creates a new LogClient given a tree config.
func NewFromTree(client trillian.TrillianLogClient, config *trillian.Tree, root types.LogRootV1) (*LogClient, error) {
verifier, err := NewLogVerifierFromTree(config)
if err != nil {
return nil, err
}
return New(config.GetTreeId(), client, verifier, root), nil
}
// AddSequencedLeafAndWait adds a leaf at a specific index to the log.
// Blocks and continuously updates the trusted root until it has been included in a signed log root.
func (c *LogClient) AddSequencedLeafAndWait(ctx context.Context, data []byte, index int64) error {
if err := c.AddSequencedLeaf(ctx, data, index); err != nil {
return fmt.Errorf("QueueLeaf(): %v", err)
}
if err := c.WaitForInclusion(ctx, data); err != nil {
return fmt.Errorf("WaitForInclusion(): %v", err)
}
return nil
}
// AddLeaf adds leaf to the append only log.
// Blocks and continuously updates the trusted root until a successful inclusion proof
// can be retrieved.
func (c *LogClient) AddLeaf(ctx context.Context, data []byte) error {
if err := c.QueueLeaf(ctx, data); err != nil {
return fmt.Errorf("QueueLeaf(): %v", err)
}
if err := c.WaitForInclusion(ctx, data); err != nil {
return fmt.Errorf("WaitForInclusion(): %v", err)
}
return nil
}
// GetByIndex returns a single leaf at the requested index.
func (c *LogClient) GetByIndex(ctx context.Context, index int64) (*trillian.LogLeaf, error) {
resp, err := c.client.GetLeavesByIndex(ctx, &trillian.GetLeavesByIndexRequest{
LogId: c.LogID,
LeafIndex: []int64{index},
})
if err != nil {
return nil, err
}
if got, want := len(resp.Leaves), 1; got != want {
return nil, fmt.Errorf("len(leaves): %v, want %v", got, want)
}
return resp.Leaves[0], nil
}
// ListByIndex returns the requested leaves by index.
func (c *LogClient) ListByIndex(ctx context.Context, start, count int64) ([]*trillian.LogLeaf, error) {
resp, err := c.client.GetLeavesByRange(ctx,
&trillian.GetLeavesByRangeRequest{
LogId: c.LogID,
StartIndex: start,
Count: count,
})
if err != nil {
return nil, err
}
// Verify that we got back the requested leaves.
if len(resp.Leaves) < int(count) {
return nil, fmt.Errorf("len(Leaves)=%d, want %d", len(resp.Leaves), count)
}
for i, l := range resp.Leaves {
if want := start + int64(i); l.LeafIndex != want {
return nil, fmt.Errorf("Leaves[%d].LeafIndex=%d, want %d", i, l.LeafIndex, want)
}
}
return resp.Leaves, nil
}
// WaitForRootUpdate repeatedly fetches the latest root until there is an
// update, which it then applies, or until ctx times out.
func (c *LogClient) WaitForRootUpdate(ctx context.Context) (*types.LogRootV1, error) {
b := &backoff.Backoff{
Min: 100 * time.Millisecond,
Max: 10 * time.Second,
Factor: 2,
Jitter: true,
}
for {
newTrusted, err := c.UpdateRoot(ctx)
switch status.Code(err) {
case codes.OK:
if newTrusted != nil {
return newTrusted, nil
}
case codes.Unavailable, codes.NotFound, codes.FailedPrecondition:
// Retry.
default:
return nil, err
}
select {
case <-ctx.Done():
return nil, status.Errorf(codes.DeadlineExceeded, "%v", ctx.Err())
case <-time.After(b.Duration()):
}
}
}
// getAndVerifyLatestRoot fetches and verifies the latest root against a trusted root, seen in the past.
// Pass nil for trusted if this is the first time querying this log.
func (c *LogClient) getAndVerifyLatestRoot(ctx context.Context, trusted *types.LogRootV1) (*types.LogRootV1, error) {
resp, err := c.client.GetLatestSignedLogRoot(ctx,
&trillian.GetLatestSignedLogRootRequest{
LogId: c.LogID,
FirstTreeSize: int64(trusted.TreeSize),
})
if err != nil {
return nil, err
}
// TODO(gbelvin): Turn on root verification.
/*
logRoot, err := c.VerifyRoot(&types.LogRootV1{}, resp.GetSignedLogRoot(), nil)
if err != nil {
return nil, err
}
*/
// TODO(gbelvin): Remove this hack when all implementations store digital signatures.
var logRoot types.LogRootV1
if err := logRoot.UnmarshalBinary(resp.GetSignedLogRoot().LogRoot); err != nil {
return nil, err
}
if trusted.TreeSize > 0 &&
logRoot.TreeSize == trusted.TreeSize &&
bytes.Equal(logRoot.RootHash, trusted.RootHash) {
// Tree has not been updated.
return &logRoot, nil
}
// Verify root update if the tree / the latest signed log root isn't empty.
if logRoot.TreeSize > 0 {
if _, err := c.VerifyRoot(trusted, resp.GetSignedLogRoot(), resp.GetProof().GetHashes()); err != nil {
return nil, err
}
}
return &logRoot, nil
}
// GetRoot returns a copy of the latest trusted root.
func (c *LogClient) GetRoot() *types.LogRootV1 {
c.rootLock.Lock()
defer c.rootLock.Unlock()
// Copy the internal trusted root in order to prevent clients from modifying it.
ret := c.root
return &ret
}
// UpdateRoot retrieves the current SignedLogRoot, verifying it against roots this client has
// seen in the past, and updating the currently trusted root if the new root verifies, and is
// newer than the currently trusted root.
func (c *LogClient) UpdateRoot(ctx context.Context) (*types.LogRootV1, error) {
// Only one root update should be running at any point in time, because
// the update involves a consistency proof from the old value, and if the
// old value could change along the way (in another goroutine) then the
// result could be inconsistent.
//
// For example, if the current root is A and two root updates A->B and A->C
// happen in parallel, then we might end up with the transitions A->B->C:
// cur := A cur := A
// getRoot() => B getRoot() => C
// proof(A->B) ok proof(A->C) ok
// c.root = B
// c.root = C
// and the last step (B->C) has no proof and so could hide a forked tree.
c.updateLock.Lock()
defer c.updateLock.Unlock()
currentlyTrusted := c.GetRoot()
newTrusted, err := c.getAndVerifyLatestRoot(ctx, currentlyTrusted)
if err != nil {
return nil, err
}
// Lock "rootLock" for the "root" update.
c.rootLock.Lock()
defer c.rootLock.Unlock()
if newTrusted.TimestampNanos > currentlyTrusted.TimestampNanos &&
newTrusted.TreeSize >= currentlyTrusted.TreeSize {
// Take a copy of the new trusted root in order to prevent clients from modifying it.
c.root = *newTrusted
return newTrusted, nil
}
return nil, nil
}
// WaitForInclusion blocks until the requested data has been verified with an
// inclusion proof.
//
// It will continuously update the root to the latest one available until the
// data is found, or an error is returned.
//
// It is best to call this method with a context that will timeout to avoid
// waiting forever.
func (c *LogClient) WaitForInclusion(ctx context.Context, data []byte) error {
leaf := c.BuildLeaf(data)
// If a minimum merge delay has been configured, wait at least that long before
// starting to poll
if c.MinMergeDelay > 0 {
select {
case <-ctx.Done():
return status.Errorf(codes.DeadlineExceeded, "%v", ctx.Err())
case <-time.After(c.MinMergeDelay):
}
}
var root *types.LogRootV1
for {
root = c.GetRoot()
// It is illegal to ask for an inclusion proof with TreeSize = 0.
if root.TreeSize >= 1 {
ok, err := c.getAndVerifyInclusionProof(ctx, leaf.MerkleLeafHash, root)
if err != nil && status.Code(err) != codes.NotFound {
return err
} else if ok {
return nil
}
}
// If not found or tree is empty, wait for a root update before retrying again.
if _, err := c.WaitForRootUpdate(ctx); err != nil {
return err
}
// Retry
}
}
// VerifyInclusion ensures that the given leaf data has been included in the log.
func (c *LogClient) VerifyInclusion(ctx context.Context, data []byte) error {
leaf := c.BuildLeaf(data)
root := c.GetRoot()
ok, err := c.getAndVerifyInclusionProof(ctx, leaf.MerkleLeafHash, root)
if err != nil {
return err
}
if !ok {
return fmt.Errorf("no proof")
}
return nil
}
// GetAndVerifyInclusionAtIndex ensures that the given leaf data has been included in the log at a particular index.
func (c *LogClient) GetAndVerifyInclusionAtIndex(ctx context.Context, data []byte, index int64, sth *types.LogRootV1) error {
resp, err := c.client.GetInclusionProof(ctx,
&trillian.GetInclusionProofRequest{
LogId: c.LogID,
LeafIndex: index,
TreeSize: int64(sth.TreeSize),
})
if err != nil {
return err
}
// If this request hit a more out-of-date server instance than the GetSLR request,
// there may be an empty proof and an earlier SLR.
var proofRoot types.LogRootV1
if err := proofRoot.UnmarshalBinary(resp.GetSignedLogRoot().GetLogRoot()); err != nil {
return err
}
if proofRoot.TreeSize < sth.TreeSize {
return fmt.Errorf("response for InclusionProof has a smaller (%d) root than requested (%d)", proofRoot.TreeSize, sth.TreeSize)
}
return c.VerifyInclusionAtIndex(sth, data, index, resp.Proof.Hashes)
}
func (c *LogClient) getAndVerifyInclusionProof(ctx context.Context, leafHash []byte, sth *types.LogRootV1) (bool, error) {
resp, err := c.client.GetInclusionProofByHash(ctx,
&trillian.GetInclusionProofByHashRequest{
LogId: c.LogID,
LeafHash: leafHash,
TreeSize: int64(sth.TreeSize),
})
if err != nil {
return false, err
}
if len(resp.Proof) < 1 {
return false, nil
}
for _, proof := range resp.Proof {
if err := c.VerifyInclusionByHash(sth, leafHash, proof); err != nil {
return false, fmt.Errorf("VerifyInclusionByHash(): %v", err)
}
}
return true, nil
}
// AddSequencedLeaf adds a leaf at a particular index.
func (c *LogClient) AddSequencedLeaf(ctx context.Context, data []byte, index int64) error {
leaf := c.BuildLeaf(data)
leaf.LeafIndex = index
_, err := c.client.AddSequencedLeaf(ctx, &trillian.AddSequencedLeafRequest{
LogId: c.LogID,
Leaf: leaf,
})
return err
}
// AddSequencedLeaves adds any number of pre-sequenced leaves to the log.
// Indexes must be contiguous.
func (c *LogClient) AddSequencedLeaves(ctx context.Context, dataByIndex map[int64][]byte) error {
if len(dataByIndex) == 0 {
return nil
}
leaves := make([]*trillian.LogLeaf, 0, len(dataByIndex))
indexes := make([]int64, 0, len(dataByIndex))
for index := range dataByIndex {
indexes = append(indexes, index)
}
sort.Slice(indexes, func(a, b int) bool { return indexes[a] < indexes[b] })
for i, index := range indexes {
// Check index continuity.
if want := indexes[0] + int64(i); index != want {
return fmt.Errorf("missing index in contiugous index range. got: %v, want: %v", index, want)
}
leaf := c.BuildLeaf(dataByIndex[index])
leaf.LeafIndex = index
leaves = append(leaves, leaf)
}
_, err := c.client.AddSequencedLeaves(ctx, &trillian.AddSequencedLeavesRequest{
LogId: c.LogID,
Leaves: leaves,
})
return err
}
// QueueLeaf adds a leaf to a Trillian log without blocking.
// AlreadyExists is considered a success case by this function.
func (c *LogClient) QueueLeaf(ctx context.Context, data []byte) error {
leaf := c.BuildLeaf(data)
_, err := c.client.QueueLeaf(ctx, &trillian.QueueLeafRequest{
LogId: c.LogID,
Leaf: leaf,
})
return err
}