feat: Support publishing new log entries to Pub/Sub topics

Adds initial support publishing new log entries to Pub/Sub topics. Interested
parties can subscribe to the topic in order to receive notifications when new
entries are added.

Signed-off-by: James Alseth <james@jalseth.me>

.gitignore

@@ -27,3 +27,7 @@ signature
 rekor.pub
 *~
 *.test
+
+# DO NOT MERGE WITH THIS
+/protobuf-specs
+# DO NOT MERGE WITH THIS

Dockerfile

@@ -18,6 +18,11 @@ ENV APP_ROOT=/opt/app-root
 ENV GOPATH=$APP_ROOT
 
 WORKDIR $APP_ROOT/src/
+
+# TEMP DO NOT MERGE WITH THIS
+ADD ./protobuf-specs/ /opt/jalseth/protobuf-specs/
+# TEMP DO NOT MERGE WITH THIS
+
 ADD go.mod go.sum $APP_ROOT/src/
 RUN go mod download
 

Dockerfile.pubsub-emulator

@@ -0,0 +1,3 @@
+# gcloud sdk for pubsub emulator with netcat added for the startup health check
+FROM google/cloud-sdk:437.0.1@sha256:615af2b80c5781891f402a38f35a5f422664f3bfee00c8ab2b94be47ac9fce8f
+RUN apt-get install -y netcat

cmd/rekor-server/app/root.go

@@ -93,6 +93,10 @@ func init() {
 Memory and file-based signers should only be used for testing.`)
 	rootCmd.PersistentFlags().String("rekor_server.signer-passwd", "", "Password to decrypt signer private key")
 
+	rootCmd.PersistentFlags().String("rekor_server.new_entry_publisher", "", "URL for pub/sub queue to send messages to when new entries are added to the log. Ignored if not set.")
+	rootCmd.PersistentFlags().Bool("rekor_server.publish_new_entry_protobuf", false, "Whether to publish events for new log entries in Protobuf wire format. Requires new_entry_publisher to be configured.")
+	rootCmd.PersistentFlags().Bool("rekor_server.publish_new_entry_json", false, "Whether to publish events for new log entries in CloudEvents JSON format. Requires new_entry_publisher to be configured.")
+
 	rootCmd.PersistentFlags().Uint16("port", 3000, "Port to bind to")
 
 	rootCmd.PersistentFlags().Bool("enable_retrieve_api", true, "enables Redis-based index API endpoint")

cmd/rekor-server/app/serve.go

@@ -61,7 +61,6 @@ var serveCmd = &cobra.Command{
 	Short: "start http server with configured api",
 	Long:  `Starts a http server and serves the configured api`,
 	Run: func(cmd *cobra.Command, args []string) {
-
 		// Setup the logger to dev/prod
 		log.ConfigureLogger(viper.GetString("log_type"))
 
@@ -83,7 +82,6 @@ var serveCmd = &cobra.Command{
 				log.Logger.Error(err)
 			}
 		}()
-
 		//TODO: make this a config option for server to load via viper field
 		//TODO: add command line option to print versions supported in binary
 
@@ -101,7 +99,6 @@ var serveCmd = &cobra.Command{
 			hashedrekord.KIND: {hashedrekord_v001.APIVERSION},
 			dsse.KIND:         {dsse_v001.APIVERSION},
 		}
-
 		for k, v := range pluggableTypeMap {
 			log.Logger.Infof("Loading support for pluggable type '%v'", k)
 			log.Logger.Infof("Loading version '%v' for pluggable type '%v'", v, k)

docker-compose.test.yml

@@ -19,6 +19,8 @@ services:
     build:
       context: .
       target: "test"
+    environment:
+      PUBSUB_EMULATOR_HOST: gcp-pubsub-emulator:8085
     command: [
       "rekor-server",
       "-test.coverprofile=rekor-server.cov",
@@ -32,7 +34,30 @@ services:
       "--enable_attestation_storage",
       "--attestation_storage_bucket=file:///var/run/attestations",
       "--max_request_body_size=32792576",
+      "--rekor_server.new_entry_publisher=gcppubsub://projects/test-project/topics/new-entry",
+      "--rekor_server.publish_new_entry_json=true",
+      "--rekor_server.publish_new_entry_protobuf=true",
       ]
     ports:
       - "3000:3000"
       - "2112:2112"
+    depends_on:
+      - gcp-pubsub-emulator
+  gcp-pubsub-emulator:
+    image: gcp-pubsub-emulator
+    ports:
+      - "8085:8085"
+    command:
+      - gcloud
+      - beta
+      - emulators
+      - pubsub
+      - start
+      - --host-port=0.0.0.0:8085
+      - --project=test-project
+    healthcheck:
+      test: ["CMD", "nc", "-zv", "localhost", "8085"]
+      interval: 10s
+      timeout: 3s
+      retries: 3
+      start_period: 10s

docker-compose.yml

@@ -112,4 +112,3 @@ services:
       timeout: 3s
       retries: 3
       start_period: 5s
-

go.mod

@@ -2,6 +2,9 @@ module github.com/sigstore/rekor
 
 go 1.19
 
+// TEMPORARY: DO NOT MERGE WITH THIS
+replace github.com/sigstore/protobuf-specs => ../../jalseth/protobuf-specs
+
 require (
 	github.com/asaskevich/govalidator v0.0.0-20230301143203-a9d515a09cc2
 	github.com/blang/semver v3.5.1+incompatible
@@ -51,6 +54,7 @@ require (
 )
 
 require (
+	cloud.google.com/go/pubsub v1.31.0
 	github.com/AdamKorcz/go-fuzz-headers-1 v0.0.0-20230329111138-12e09aba5ebd
 	github.com/cyberphone/json-canonicalization v0.0.0-20220623050100-57a0ce2678a7
 	github.com/go-redis/redismock/v9 v9.0.3
@@ -180,7 +184,7 @@ require (
 	golang.org/x/term v0.9.0 // indirect
 	golang.org/x/text v0.10.0 // indirect
 	golang.org/x/xerrors v0.0.0-20220907171357-04be3eba64a2 // indirect
-	google.golang.org/api v0.128.0 // indirect
+	google.golang.org/api v0.128.0
 	google.golang.org/appengine v1.6.7 // indirect
 	gopkg.in/square/go-jose.v2 v2.6.0 // indirect
 	gopkg.in/yaml.v2 v2.4.0

go.sum

@@ -444,6 +444,7 @@ cloud.google.com/go/pubsub v1.26.0/go.mod h1:QgBH3U/jdJy/ftjPhTkyXNj543Tin1pRYcd
 cloud.google.com/go/pubsub v1.27.1/go.mod h1:hQN39ymbV9geqBnfQq6Xf63yNhUAhv9CZhzp5O6qsW0=
 cloud.google.com/go/pubsub v1.28.0/go.mod h1:vuXFpwaVoIPQMGXqRyUQigu/AX1S3IWugR9xznmcXX8=
 cloud.google.com/go/pubsub v1.30.0/go.mod h1:qWi1OPS0B+b5L+Sg6Gmc9zD1Y+HaM0MdUr7LsupY1P4=
+cloud.google.com/go/pubsub v1.31.0 h1:aXdyyJz90kA+bor9+6+xHAciMD5mj8v15WqFZ5E0sek=
 cloud.google.com/go/pubsub v1.31.0/go.mod h1:dYmJ3K97NCQ/e4OwZ20rD4Ym3Bu8Gu9m/aJdWQjdcks=
 cloud.google.com/go/pubsublite v1.5.0/go.mod h1:xapqNQ1CuLfGi23Yda/9l4bBCKz/wC3KIJ5gKcxveZg=
 cloud.google.com/go/pubsublite v1.6.0/go.mod h1:1eFCS0U11xlOuMFV/0iBqw3zP12kddMeCbj/F3FSj9k=
@@ -2122,8 +2123,6 @@ github.com/shopspring/decimal v1.2.0/go.mod h1:DKyhrW/HYNuLGql+MJL6WCR6knT2jwCFR
 github.com/shurcooL/httpfs v0.0.0-20190707220628-8d4bc4ba7749/go.mod h1:ZY1cvUeJuFPAdZ/B6v7RHavJWZn2YPVFQ1OSXhCGOkg=
 github.com/shurcooL/sanitized_anchor_name v1.0.0/go.mod h1:1NzhyTcUVG4SuEtjjoZeVRXNmyL/1OwPU0+IJeTBvfc=
 github.com/shurcooL/vfsgen v0.0.0-20200824052919-0d455de96546/go.mod h1:TrYk7fJVaAttu97ZZKrO9UbRa8izdowaMIZcxYMbVaw=
-github.com/sigstore/protobuf-specs v0.1.0 h1:X0l/E2C2c79t/rI/lmSu8WAoKWsQtMqDzAMiDdEMGr8=
-github.com/sigstore/protobuf-specs v0.1.0/go.mod h1:5shUCxf82hGnjUEFVWiktcxwzdtn6EfeeJssxZ5Q5HE=
 github.com/sigstore/sigstore v1.7.1 h1:fCATemikcBK0cG4+NcM940MfoIgmioY1vC6E66hXxks=
 github.com/sigstore/sigstore v1.7.1/go.mod h1:0PmMzfJP2Y9+lugD0wer4e7TihR5tM7NcIs3bQNk5xg=
 github.com/sigstore/sigstore/pkg/signature/kms/aws v1.7.1 h1:rDHrG/63b3nBq3G9plg7iYnWN6lBhOfq/XultlCZgII=

pkg/api/api.go

@@ -31,6 +31,7 @@ import (
 	"google.golang.org/grpc/credentials/insecure"
 
 	"github.com/sigstore/rekor/pkg/log"
+	"github.com/sigstore/rekor/pkg/pubsub"
 	"github.com/sigstore/rekor/pkg/sharding"
 	"github.com/sigstore/rekor/pkg/signer"
 	"github.com/sigstore/rekor/pkg/storage"
@@ -39,6 +40,8 @@ import (
 	"github.com/sigstore/sigstore/pkg/cryptoutils"
 	"github.com/sigstore/sigstore/pkg/signature"
 	"github.com/sigstore/sigstore/pkg/signature/options"
+
+	_ "github.com/sigstore/rekor/pkg/pubsub/gcp" // Load GCP pubsub implementation
 )
 
 func dial(ctx context.Context, rpcServer string) (*grpc.ClientConn, error) {
@@ -63,6 +66,9 @@ type API struct {
 	signer     signature.Signer
 	// stops checkpoint publishing
 	checkpointPublishCancel context.CancelFunc
+	// Publishes notifications when new entries are added to the log. May be
+	// nil if no publisher is configured.
+	newEntryPublisher pubsub.Publisher
 }
 
 func NewAPI(treeID uint) (*API, error) {
@@ -112,6 +118,18 @@ func NewAPI(treeID uint) (*API, error) {
 
 	pubkey := cryptoutils.PEMEncode(cryptoutils.PublicKeyPEMType, b)
 
+	var newEntryPublisher pubsub.Publisher
+	if p := viper.GetString("rekor_server.new_entry_publisher"); p != "" {
+		if !viper.GetBool("rekor_server.publish_new_entry_protobuf") && !viper.GetBool("rekor_server.publish_new_entry_json") {
+			return nil, fmt.Errorf("%q is configured but neither %q or %q are enabled", "new_entry_publisher", "publish_new_entry_protobuf", "publish_new_entry_json")
+		}
+		newEntryPublisher, err = pubsub.Get(ctx, p)
+		if err != nil {
+			return nil, fmt.Errorf("init event publisher: %w", err)
+		}
+		log.ContextLogger(ctx).Debugf("Initialized new entry event publisher: %s", p)
+	}
+
 	return &API{
 		// Transparency Log Stuff
 		logClient: logClient,
@@ -121,6 +139,8 @@ func NewAPI(treeID uint) (*API, error) {
 		pubkey:     string(pubkey),
 		pubkeyHash: hex.EncodeToString(pubkeyHashBytes[:]),
 		signer:     rekorSigner,
+		// Utility functionality not required for operation of the core service
+		newEntryPublisher: newEntryPublisher,
 	}, nil
 }
 
@@ -165,5 +185,8 @@ func ConfigureAPI(treeID uint) {
 }
 
 func StopAPI() {
+	if api.newEntryPublisher != nil {
+		api.newEntryPublisher.Close()
+	}
 	api.checkpointPublishCancel()
 }

pkg/api/entries.go

@@ -35,11 +35,16 @@ import (
 	"github.com/transparency-dev/merkle/rfc6962"
 	"google.golang.org/genproto/googleapis/rpc/code"
 	"google.golang.org/grpc/codes"
+	"google.golang.org/protobuf/encoding/prototext"
 
+	"github.com/sigstore/rekor/pkg/events"
+	"github.com/sigstore/rekor/pkg/events/newentry"
 	"github.com/sigstore/rekor/pkg/generated/models"
 	"github.com/sigstore/rekor/pkg/generated/restapi/operations/entries"
 	"github.com/sigstore/rekor/pkg/log"
+	"github.com/sigstore/rekor/pkg/pubsub"
 	"github.com/sigstore/rekor/pkg/sharding"
+	"github.com/sigstore/rekor/pkg/tle"
 	"github.com/sigstore/rekor/pkg/trillianclient"
 	"github.com/sigstore/rekor/pkg/types"
 	"github.com/sigstore/rekor/pkg/util"
@@ -290,7 +295,7 @@ func createLogEntry(params entries.CreateLogEntryParams) (models.LogEntry, middl
 		RootHash:   swag.String(hex.EncodeToString(root.RootHash)),
 		LogIndex:   swag.Int64(queuedLeaf.LeafIndex),
 		Hashes:     hashes,
-		Checkpoint: stringPointer(string(scBytes)),
+		Checkpoint: swag.String(string(scBytes)),
 	}
 
 	logEntryAnon.Verification = &models.LogEntryAnonVerification{
@@ -301,9 +306,64 @@ func createLogEntry(params entries.CreateLogEntryParams) (models.LogEntry, middl
 	logEntry := models.LogEntry{
 		entryID: logEntryAnon,
 	}
+
+	if api.newEntryPublisher != nil {
+		// Publishing notifications should not block the API response.
+		go func() {
+			var subjects []string
+			verifier, err := entry.Verifier()
+			if err != nil {
+				log.ContextLogger(ctx).Warnf("Could not get verifier for log entry %s: %w", entryID, err)
+			} else {
+				subjects = verifier.Subjects()
+			}
+			pbEntry, err := tle.GenerateTransparencyLogEntry(logEntryAnon)
+			if err != nil {
+				incPublishEvent(newentry.Name, "", false)
+				log.ContextLogger(ctx).Error(err)
+				return
+			}
+			event, err := newentry.New(entryID, pbEntry, subjects)
+			if err != nil {
+				incPublishEvent(newentry.Name, "", false)
+				log.ContextLogger(ctx).Error(err)
+				return
+			}
+			if viper.GetBool("rekor_server.publish_new_entry_protobuf") {
+				publishEvent(ctx, api.newEntryPublisher, event, events.ContentTypeProtobuf)
+			}
+			if viper.GetBool("rekor_server.publish_new_entry_json") {
+				publishEvent(ctx, api.newEntryPublisher, event, events.ContentTypeJSON)
+			}
+		}()
+	}
+
 	return logEntry, nil
 }
 
+func publishEvent(ctx context.Context, publisher pubsub.Publisher, event *events.Event, contentType events.EventContentType) {
+	err := publisher.Publish(context.Background(), event, contentType)
+	incPublishEvent(event.Type().Name(), contentType, err != nil)
+	if err != nil {
+		log.ContextLogger(ctx).Error(err)
+	} else {
+		log.ContextLogger(ctx).Debugf("Published new entry event (%s): %s", contentType, prototext.Format(event.Message()))
+	}
+}
+
+func incPublishEvent(event string, contentType events.EventContentType, success bool) {
+	status := "ERROR"
+	if success {
+		status = "SUCCESS"
+	}
+	labels := map[string]string{
+		"event":        event,
+		"status":       status,
+		"content_type": string(contentType),
+	}
+	metricPublishEvents.With(labels).Inc()
+}
+
 // CreateLogEntryHandler creates new entry into log
 func CreateLogEntryHandler(params entries.CreateLogEntryParams) middleware.Responder {
 	httpReq := params.HTTPRequest

pkg/api/metrics.go

@@ -29,6 +29,11 @@ var (
 		Help: "The total number of new log entries",
 	})
 
+	metricPublishEvents = promauto.NewCounterVec(prometheus.CounterOpts{
+		Name: "rekor_publish_events",
+		Help: "The status of publishing events to Pub/Sub",
+	}, []string{"event", "content_type", "status"})
+
 	MetricLatency = promauto.NewHistogramVec(prometheus.HistogramOpts{
 		Name: "rekor_api_latency",
 		Help: "Api Latency on calls",

pkg/events/doc.go

@@ -0,0 +1,19 @@
+// Copyright 2023 The Sigstore Authors.
+//
+// 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 events provides methods for working with CloudEvents.
+package events
+
+// The version of the CloudEvents specification the package adheres to.
+const CloudEventsSpecVersion = "1.0"