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package stfe
import (
"context"
"fmt"
"reflect"
"sync"
"github.com/golang/glog"
"github.com/google/certificate-transparency-go/schedule"
"github.com/google/trillian"
ttypes "github.com/google/trillian/types"
"github.com/system-transparency/stfe/types"
)
// SthSource provides access to the log's STHs.
type SthSource interface {
// Latest returns the most reccent signed_tree_head_v*.
Latest(context.Context) (*types.StItem, error)
// Stable returns the most recent signed_tree_head_v* that is stable for
// some period of time, e.g., 10 minutes.
Stable(context.Context) (*types.StItem, error)
// Cosigned returns the most recent cosigned_tree_head_v*.
Cosigned(context.Context) (*types.StItem, error)
// AddCosignature attempts to add a cosignature to the stable STH. The
// passed cosigned_tree_head_v* must have a single verified cosignature.
AddCosignature(context.Context, *types.StItem) error
// Run keeps the STH source updated until cancelled
Run(context.Context)
}
// ActiveSthSource implements the SthSource interface for an STFE instance that
// accepts new logging requests, i.e., the log is running in read+write mode.
type ActiveSthSource struct {
client trillian.TrillianLogClient
logParameters *LogParameters
currCosth *types.StItem // current cosigned_tree_head_v1 (already finalized)
nextCosth *types.StItem // next cosigned_tree_head_v1 (under preparation)
cosignatureFrom map[[types.NamespaceFingerprintSize]byte]bool // track who we got cosignatures from in nextCosth
mutex sync.RWMutex
}
// NewActiveSthSource returns an initialized ActiveSthSource
func NewActiveSthSource(cli trillian.TrillianLogClient, lp *LogParameters) (*ActiveSthSource, error) {
s := ActiveSthSource{
client: cli,
logParameters: lp,
}
ctx, _ := context.WithTimeout(context.Background(), lp.Deadline)
sth, err := s.Latest(ctx)
if err != nil {
return nil, fmt.Errorf("Latest: %v", err)
}
// TODO: load persisted cosigned STH?
s.currCosth = types.NewCosignedTreeHeadV1(sth.SignedTreeHeadV1, nil)
s.nextCosth = types.NewCosignedTreeHeadV1(sth.SignedTreeHeadV1, nil)
s.cosignatureFrom = make(map[[types.NamespaceFingerprintSize]byte]bool)
return &s, nil
}
func (s *ActiveSthSource) Run(ctx context.Context) {
schedule.Every(ctx, s.logParameters.Interval, func(ctx context.Context) {
// get the next stable sth
ictx, _ := context.WithTimeout(ctx, s.logParameters.Deadline)
sth, err := s.Latest(ictx)
if err != nil {
glog.Warningf("cannot rotate without new sth: Latest: %v", err)
return
}
// rotate
s.mutex.Lock()
defer s.mutex.Unlock()
if err := s.rotate(sth); err != nil {
glog.Warningf("rotate failed: %v", err)
}
// TODO: persist cosigned STH?
})
}
func (s *ActiveSthSource) Latest(ctx context.Context) (*types.StItem, error) {
trsp, err := s.client.GetLatestSignedLogRoot(ctx, &trillian.GetLatestSignedLogRootRequest{
LogId: s.logParameters.TreeId,
})
var lr ttypes.LogRootV1
if errInner := checkGetLatestSignedLogRoot(s.logParameters, trsp, err, &lr); errInner != nil {
return nil, fmt.Errorf("invalid signed log root response: %v", errInner)
}
return s.logParameters.SignTreeHeadV1(NewTreeHeadV1FromLogRoot(&lr))
}
func (s *ActiveSthSource) Stable(_ context.Context) (*types.StItem, error) {
s.mutex.RLock()
defer s.mutex.RUnlock()
if s.nextCosth == nil {
return nil, fmt.Errorf("no stable sth available")
}
return types.NewSignedTreeHeadV1(&s.nextCosth.CosignedTreeHeadV1.SignedTreeHead.TreeHead, &s.nextCosth.CosignedTreeHeadV1.SignedTreeHead.Signature), nil
}
func (s *ActiveSthSource) Cosigned(_ context.Context) (*types.StItem, error) {
s.mutex.RLock()
defer s.mutex.RUnlock()
if s.currCosth == nil {
return nil, fmt.Errorf("no cosigned sth available")
}
return s.currCosth, nil
}
func (s *ActiveSthSource) AddCosignature(_ context.Context, costh *types.StItem) error {
s.mutex.Lock()
defer s.mutex.Unlock()
if !reflect.DeepEqual(s.nextCosth.CosignedTreeHeadV1.SignedTreeHead, costh.CosignedTreeHeadV1.SignedTreeHead) {
return fmt.Errorf("cosignature covers a different tree head")
}
witness, err := costh.CosignedTreeHeadV1.Cosignatures[0].Namespace.Fingerprint()
if err != nil {
return fmt.Errorf("namespace without fingerprint: %v", err)
}
if _, ok := s.cosignatureFrom[*witness]; ok {
return nil // duplicate
}
s.cosignatureFrom[*witness] = true
s.nextCosth.CosignedTreeHeadV1.Cosignatures = append(s.nextCosth.CosignedTreeHeadV1.Cosignatures, costh.CosignedTreeHeadV1.Cosignatures[0])
return nil
}
// rotate rotates the log's cosigned and stable STH. The caller must aquire the
// source's read-write lock if there are concurrent reads and/or writes.
func (s *ActiveSthSource) rotate(fixedSth *types.StItem) error {
// rotate stable -> cosigned
if reflect.DeepEqual(&s.currCosth.CosignedTreeHeadV1.SignedTreeHead, &s.nextCosth.CosignedTreeHeadV1.SignedTreeHead) {
for _, sigv1 := range s.currCosth.CosignedTreeHeadV1.Cosignatures {
witness, err := sigv1.Namespace.Fingerprint()
if err != nil {
return fmt.Errorf("namespace without fingerprint: %v", err)
}
if _, ok := s.cosignatureFrom[*witness]; !ok {
s.cosignatureFrom[*witness] = true
s.nextCosth.CosignedTreeHeadV1.Cosignatures = append(s.nextCosth.CosignedTreeHeadV1.Cosignatures, sigv1)
}
}
}
s.currCosth.CosignedTreeHeadV1.SignedTreeHead = s.nextCosth.CosignedTreeHeadV1.SignedTreeHead
s.currCosth.CosignedTreeHeadV1.Cosignatures = make([]types.SignatureV1, len(s.nextCosth.CosignedTreeHeadV1.Cosignatures))
copy(s.currCosth.CosignedTreeHeadV1.Cosignatures, s.nextCosth.CosignedTreeHeadV1.Cosignatures)
// rotate new stable -> stable
if !reflect.DeepEqual(&s.nextCosth.CosignedTreeHeadV1.SignedTreeHead, fixedSth.SignedTreeHeadV1) {
s.nextCosth = types.NewCosignedTreeHeadV1(fixedSth.SignedTreeHeadV1, nil)
s.cosignatureFrom = make(map[[types.NamespaceFingerprintSize]byte]bool)
}
return nil
}
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