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package state
import (
"context"
"crypto"
"crypto/ed25519"
"fmt"
"sync"
"time"
"git.sigsum.org/sigsum-go/pkg/types"
"git.sigsum.org/sigsum-log-go/pkg/db"
"github.com/golang/glog"
)
// StateManagerSingle implements a single-instance StateManager
type StateManagerSingle struct {
client db.Client
signer crypto.Signer
namespace types.Hash
interval time.Duration
deadline time.Duration
// Lock-protected access to pointers. A write lock is only obtained once
// per interval when doing pointer rotation. All endpoints are readers.
sync.RWMutex
signedTreeHead *types.SignedTreeHead
cosignedTreeHead *types.CosignedTreeHead
// Syncronized and deduplicated witness cosignatures for signedTreeHead
events chan *event
cosignatures map[types.Hash]*types.Signature
}
func NewStateManagerSingle(client db.Client, signer crypto.Signer, interval, deadline time.Duration) (*StateManagerSingle, error) {
sm := &StateManagerSingle{
client: client,
signer: signer,
namespace: *types.HashFn(signer.Public().(ed25519.PublicKey)),
interval: interval,
deadline: deadline,
}
sth, err := sm.latestSTH(context.Background())
sm.setCosignedTreeHead()
sm.setToCosignTreeHead(sth)
return sm, err
}
func (sm *StateManagerSingle) Run(ctx context.Context) {
rotation := func() {
nextSTH, err := sm.latestSTH(ctx)
if err != nil {
glog.Warningf("cannot rotate without tree head: %v", err)
return
}
sm.rotate(nextSTH)
}
sm.events = make(chan *event, 4096)
defer close(sm.events)
ticker := time.NewTicker(sm.interval)
defer ticker.Stop()
rotation()
for {
select {
case <-ticker.C:
rotation()
case ev := <-sm.events:
sm.handleEvent(ev)
case <-ctx.Done():
return
}
}
}
func (sm *StateManagerSingle) ToCosignTreeHead(_ context.Context) (*types.SignedTreeHead, error) {
sm.RLock()
defer sm.RUnlock()
return sm.signedTreeHead, nil
}
func (sm *StateManagerSingle) CosignedTreeHead(_ context.Context) (*types.CosignedTreeHead, error) {
sm.RLock()
defer sm.RUnlock()
if sm.cosignedTreeHead == nil {
return nil, fmt.Errorf("no cosignatures available")
}
return sm.cosignedTreeHead, nil
}
func (sm *StateManagerSingle) AddCosignature(ctx context.Context, pub *types.PublicKey, sig *types.Signature) error {
sm.RLock()
defer sm.RUnlock()
msg := sm.signedTreeHead.TreeHead.ToBinary(&sm.namespace)
if !ed25519.Verify(ed25519.PublicKey(pub[:]), msg, sig[:]) {
return fmt.Errorf("invalid cosignature")
}
select {
case sm.events <- &event{types.HashFn(pub[:]), sig}:
return nil
case <-ctx.Done():
return fmt.Errorf("request timeout")
}
}
func (sm *StateManagerSingle) rotate(nextSTH *types.SignedTreeHead) {
sm.Lock()
defer sm.Unlock()
glog.V(3).Infof("rotating tree heads")
sm.handleEvents()
sm.setCosignedTreeHead()
sm.setToCosignTreeHead(nextSTH)
}
func (sm *StateManagerSingle) handleEvents() {
glog.V(3).Infof("handling any outstanding events")
for i, n := 0, len(sm.events); i < n; i++ {
sm.handleEvent(<-sm.events)
}
}
func (sm *StateManagerSingle) handleEvent(ev *event) {
glog.V(3).Infof("handling event from witness %x", ev.keyHash[:])
sm.cosignatures[*ev.keyHash] = ev.cosignature
}
func (sm *StateManagerSingle) setCosignedTreeHead() {
n := len(sm.cosignatures)
if n == 0 {
sm.cosignedTreeHead = nil
return
}
var cth types.CosignedTreeHead
cth.SignedTreeHead = *sm.signedTreeHead
cth.Cosignature = make([]types.Signature, 0, n)
cth.KeyHash = make([]types.Hash, 0, n)
for keyHash, cosignature := range sm.cosignatures {
cth.KeyHash = append(cth.KeyHash, keyHash)
cth.Cosignature = append(cth.Cosignature, *cosignature)
}
sm.cosignedTreeHead = &cth
}
func (sm *StateManagerSingle) setToCosignTreeHead(nextSTH *types.SignedTreeHead) {
sm.cosignatures = make(map[types.Hash]*types.Signature)
sm.signedTreeHead = nextSTH
}
func (sm *StateManagerSingle) latestSTH(ctx context.Context) (*types.SignedTreeHead, error) {
ictx, cancel := context.WithTimeout(ctx, sm.deadline)
defer cancel()
th, err := sm.client.GetTreeHead(ictx)
if err != nil {
return nil, fmt.Errorf("failed fetching tree head: %v", err)
}
sth, err := th.Sign(sm.signer, &sm.namespace)
if err != nil {
return nil, fmt.Errorf("failed signing tree head: %v", err)
}
return sth, nil
}
|
