Bundle TUF timestamp with signature on signing (#1294)

* Bundle TUF timestamp with signature on signing

This updates the code to support adding the TUF timestamp
to the OCI signature.

Changes to pkg/oci add support for reading and saving the
timestamp by annotation key. Changes to the TUF client
add putting the timestamp in memory on client
initialization, so callers can access the timestamp.

Signed-off-by: Hayden Blauzvern <hblauzvern@google.com>

* Add TUF timestamp to OCI signature on sign

This adds the TUF timestamp to the Fulcio and Rekor
signers. Both are necessary since each relies on
TUF metadata. If both signers are used, the latter
one will overwrite the TUF timestamp.

I also added a basic mock Rekor client for tests.
A number of methods are not implemented yet.

Signed-off-by: Hayden Blauzvern <hblauzvern@google.com>

* Add license

Signed-off-by: Hayden Blauzvern <hblauzvern@google.com>

* Move timestamp to TUF package

Signed-off-by: Hayden Blauzvern <hblauzvern@google.com>

* Update TUF client to persist local store

Signed-off-by: Hayden Blauzvern <hblauzvern@google.com>

cmd/cosign/cli/sign/sign.go

@@ -205,7 +205,9 @@ func signDigest(ctx context.Context, digest name.Digest, payload []byte, ko KeyO
 
 	var s icos.Signer
 	s = ipayload.NewSigner(sv)
-	s = ifulcio.NewSigner(s, sv.Cert, sv.Chain)
+	if sv.Cert != nil {
+		s = ifulcio.NewSigner(s, sv.Cert, sv.Chain)
+	}
 	if ShouldUploadToTlog(ctx, digest, force, ko.RekorURL) {
 		rClient, err := rekor.NewClient(ko.RekorURL)
 		if err != nil {

internal/pkg/cosign/fulcio/signer.go

@@ -20,6 +20,7 @@ import (
 	"io"
 
 	"github.com/sigstore/cosign/internal/pkg/cosign"
+	"github.com/sigstore/cosign/pkg/cosign/tuf"
 	"github.com/sigstore/cosign/pkg/oci"
 	"github.com/sigstore/cosign/pkg/oci/mutate"
 )
@@ -41,8 +42,13 @@ func (fs *signerWrapper) Sign(ctx context.Context, payload io.Reader) (oci.Signa
 		return nil, nil, err
 	}
 
+	timestamp, err := tuf.GetTimestamp(ctx)
+	if err != nil {
+		return nil, nil, err
+	}
+
 	// TODO(dekkagaijin): move the fulcio SignerVerifier logic here
-	newSig, err := mutate.Signature(sig, mutate.WithCertChain(fs.cert, fs.chain))
+	newSig, err := mutate.Signature(sig, mutate.WithCertChain(fs.cert, fs.chain), mutate.WithTimestamp(timestamp))
 	if err != nil {
 		return nil, nil, err
 	}

internal/pkg/cosign/fulcio/signer_test.go

@@ -0,0 +1,140 @@
+// Copyright 2022 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 fulcio
+
+import (
+	"bytes"
+	"context"
+	"crypto"
+	"encoding/base64"
+	"strings"
+	"testing"
+
+	"github.com/sigstore/cosign/internal/pkg/cosign/payload"
+	"github.com/sigstore/cosign/pkg/cosign"
+	"github.com/sigstore/sigstore/pkg/signature"
+)
+
+var (
+	testCertBytes = []byte(`
+-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----
+`)
+	testChainBytes = []byte(`
+-----BEGIN CERTIFICATE-----
+MIIB+DCCAX6gAwIBAgITNVkDZoCiofPDsy7dfm6geLbuhzAKBggqhkjOPQQDAzAq
+MRUwEwYDVQQKEwxzaWdzdG9yZS5kZXYxETAPBgNVBAMTCHNpZ3N0b3JlMB4XDTIx
+MDMwNzAzMjAyOVoXDTMxMDIyMzAzMjAyOVowKjEVMBMGA1UEChMMc2lnc3RvcmUu
+ZGV2MREwDwYDVQQDEwhzaWdzdG9yZTB2MBAGByqGSM49AgEGBSuBBAAiA2IABLSy
+A7Ii5k+pNO8ZEWY0ylemWDowOkNa3kL+GZE5Z5GWehL9/A9bRNA3RbrsZ5i0Jcas
+taRL7Sp5fp/jD5dxqc/UdTVnlvS16an+2Yfswe/QuLolRUCrcOE2+2iA5+tzd6Nm
+MGQwDgYDVR0PAQH/BAQDAgEGMBIGA1UdEwEB/wQIMAYBAf8CAQEwHQYDVR0OBBYE
+FMjFHQBBmiQpMlEk6w2uSu1KBtPsMB8GA1UdIwQYMBaAFMjFHQBBmiQpMlEk6w2u
+Su1KBtPsMAoGCCqGSM49BAMDA2gAMGUCMH8liWJfMui6vXXBhjDgY4MwslmN/TJx
+Ve/83WrFomwmNf056y1X48F9c4m3a3ozXAIxAKjRay5/aj/jsKKGIkmQatjI8uup
+Hr/+CxFvaJWmpYqNkLDGRU+9orzh5hI2RrcuaQ==
+-----END CERTIFICATE-----
+`)
+)
+
+func mustGetNewSigner(t *testing.T) signature.Signer {
+	t.Helper()
+	priv, err := cosign.GeneratePrivateKey()
+	if err != nil {
+		t.Fatalf("cosign.GeneratePrivateKey() failed: %v", err)
+	}
+	s, err := signature.LoadECDSASignerVerifier(priv, crypto.SHA256)
+	if err != nil {
+		t.Fatalf("signature.LoadECDSASignerVerifier(key, crypto.SHA256) failed: %v", err)
+	}
+	return s
+}
+
+func TestSigner(t *testing.T) {
+	// Need real cert and chain
+	payloadSigner := payload.NewSigner(mustGetNewSigner(t))
+	testSigner := NewSigner(payloadSigner, testCertBytes, testChainBytes)
+
+	testPayload := "test payload"
+
+	ociSig, pub, err := testSigner.Sign(context.Background(), strings.NewReader(testPayload))
+	if err != nil {
+		t.Fatalf("Sign() returned error: %v", err)
+	}
+
+	// Verify that the OCI signature contains a cert, chain and timestamp.
+	cert, err := ociSig.Cert()
+	if err != nil {
+		t.Fatalf("ociSig.Cert() returned error: %v", err)
+	}
+	if cert == nil {
+		t.Fatal("ociSig.Cert() missing certificate, got nil")
+	}
+	chain, err := ociSig.Chain()
+	if err != nil {
+		t.Fatalf("ociSig.Chain() returned error: %v", err)
+	}
+	if len(chain) != 1 {
+		t.Fatalf("ociSig.Chain() expected to be of length 1, got %d", len(chain))
+	}
+	if chain[0] == nil {
+		t.Fatal("ociSig.Chain()[0] missing certificate, got nil")
+	}
+	timestamp, err := ociSig.Timestamp()
+	if err != nil {
+		t.Fatalf("ociSig.Timestamp() returned error: %v", err)
+	}
+	if timestamp == nil {
+		t.Fatal("ociSig.Timestamp() missing TUF timestamp, got nil")
+	}
+
+	// Verify that the wrapped signer was called.
+	verifier, err := signature.LoadVerifier(pub, crypto.SHA256)
+	if err != nil {
+		t.Fatalf("signature.LoadVerifier(pub) returned error: %v", err)
+	}
+	b64Sig, err := ociSig.Base64Signature()
+	if err != nil {
+		t.Fatalf("ociSig.Base64Signature() returned error: %v", err)
+	}
+	sig, err := base64.StdEncoding.DecodeString(b64Sig)
+	if err != nil {
+		t.Fatalf("base64.StdEncoding.DecodeString(b64Sig) returned error: %v", err)
+	}
+	gotPayload, err := ociSig.Payload()
+	if err != nil {
+		t.Fatalf("ociSig.Payload() returned error: %v", err)
+	}
+	if string(gotPayload) != testPayload {
+		t.Errorf("ociSig.Payload() returned %q, wanted %q", string(gotPayload), testPayload)
+	}
+	if err = verifier.VerifySignature(bytes.NewReader(sig), bytes.NewReader(gotPayload)); err != nil {
+		t.Errorf("VerifySignature() returned error: %v", err)
+	}
+}

internal/pkg/cosign/rekor/mock_rekor_client.go

@@ -0,0 +1,64 @@
+// Copyright 2022 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 rekor
+
+import (
+	"github.com/go-openapi/runtime"
+	"github.com/sigstore/rekor/pkg/generated/client/entries"
+	"github.com/sigstore/rekor/pkg/generated/models"
+)
+
+// Client that implements entries.ClientService for Rekor
+// To use:
+// var mClient client.Rekor
+// mClient.entries = &MockEntriesClient{}
+type MockEntriesClient struct {
+}
+
+func (m *MockEntriesClient) CreateLogEntry(params *entries.CreateLogEntryParams, opts ...entries.ClientOption) (*entries.CreateLogEntryCreated, error) {
+	return &entries.CreateLogEntryCreated{
+		ETag:     "",
+		Location: "",
+		Payload: map[string]models.LogEntryAnon{
+			"sdf": {
+				Attestation:    &models.LogEntryAnonAttestation{},
+				Body:           nil,
+				IntegratedTime: new(int64),
+				LogID:          new(string),
+				LogIndex:       new(int64),
+				Verification:   &models.LogEntryAnonVerification{},
+			},
+		},
+	}, nil
+}
+
+// TODO: Implement mock
+func (m *MockEntriesClient) GetLogEntryByIndex(params *entries.GetLogEntryByIndexParams, opts ...entries.ClientOption) (*entries.GetLogEntryByIndexOK, error) {
+	return nil, nil
+}
+
+// TODO: Implement mock
+func (m *MockEntriesClient) GetLogEntryByUUID(params *entries.GetLogEntryByUUIDParams, opts ...entries.ClientOption) (*entries.GetLogEntryByUUIDOK, error) {
+	return nil, nil
+}
+
+// TODO: Implement mock
+func (m *MockEntriesClient) SearchLogQuery(params *entries.SearchLogQueryParams, opts ...entries.ClientOption) (*entries.SearchLogQueryOK, error) {
+	return nil, nil
+}
+
+// TODO: Implement mock
+func (m *MockEntriesClient) SetTransport(transport runtime.ClientTransport) {
+}

internal/pkg/cosign/rekor/signer.go

@@ -25,6 +25,7 @@ import (
 	"github.com/sigstore/cosign/internal/pkg/cosign"
 	cosignv1 "github.com/sigstore/cosign/pkg/cosign"
 	cbundle "github.com/sigstore/cosign/pkg/cosign/bundle"
+	"github.com/sigstore/cosign/pkg/cosign/tuf"
 	"github.com/sigstore/cosign/pkg/oci"
 	"github.com/sigstore/cosign/pkg/oci/mutate"
 
@@ -96,7 +97,12 @@ func (rs *signerWrapper) Sign(ctx context.Context, payload io.Reader) (oci.Signa
 		return nil, nil, err
 	}
 
-	newSig, err := mutate.Signature(sig, mutate.WithBundle(bundle))
+	timestamp, err := tuf.GetTimestamp(ctx)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	newSig, err := mutate.Signature(sig, mutate.WithBundle(bundle), mutate.WithTimestamp(timestamp))
 	if err != nil {
 		return nil, nil, err
 	}

internal/pkg/cosign/rekor/signer_test.go

@@ -0,0 +1,93 @@
+// Copyright 2022 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 rekor
+
+import (
+	"bytes"
+	"context"
+	"crypto"
+	"encoding/base64"
+	"strings"
+	"testing"
+
+	"github.com/sigstore/cosign/internal/pkg/cosign/payload"
+	"github.com/sigstore/cosign/pkg/cosign"
+	"github.com/sigstore/rekor/pkg/generated/client"
+	"github.com/sigstore/sigstore/pkg/signature"
+)
+
+func mustGetNewSigner(t *testing.T) signature.Signer {
+	t.Helper()
+	priv, err := cosign.GeneratePrivateKey()
+	if err != nil {
+		t.Fatalf("cosign.GeneratePrivateKey() failed: %v", err)
+	}
+	s, err := signature.LoadECDSASignerVerifier(priv, crypto.SHA256)
+	if err != nil {
+		t.Fatalf("signature.LoadECDSASignerVerifier(key, crypto.SHA256) failed: %v", err)
+	}
+	return s
+}
+
+func TestSigner(t *testing.T) {
+	// Need real cert and chain
+	payloadSigner := payload.NewSigner(mustGetNewSigner(t))
+
+	// Mock out Rekor client
+	var mClient client.Rekor
+	mClient.Entries = &MockEntriesClient{}
+
+	testSigner := NewSigner(payloadSigner, &mClient)
+
+	testPayload := "test payload"
+
+	ociSig, pub, err := testSigner.Sign(context.Background(), strings.NewReader(testPayload))
+	if err != nil {
+		t.Fatalf("Sign() returned error: %v", err)
+	}
+
+	// Verify that the OCI signature contains a timestamp.
+	timestamp, err := ociSig.Timestamp()
+	if err != nil {
+		t.Fatalf("ociSig.Timestamp() returned error: %v", err)
+	}
+	if timestamp == nil {
+		t.Fatal("ociSig.Timestamp() missing TUF timestamp, got nil")
+	}
+
+	// Verify that the wrapped signer was called.
+	verifier, err := signature.LoadVerifier(pub, crypto.SHA256)
+	if err != nil {
+		t.Fatalf("signature.LoadVerifier(pub) returned error: %v", err)
+	}
+	b64Sig, err := ociSig.Base64Signature()
+	if err != nil {
+		t.Fatalf("ociSig.Base64Signature() returned error: %v", err)
+	}
+	sig, err := base64.StdEncoding.DecodeString(b64Sig)
+	if err != nil {
+		t.Fatalf("base64.StdEncoding.DecodeString(b64Sig) returned error: %v", err)
+	}
+	gotPayload, err := ociSig.Payload()
+	if err != nil {
+		t.Fatalf("ociSig.Payload() returned error: %v", err)
+	}
+	if string(gotPayload) != testPayload {
+		t.Errorf("ociSig.Payload() returned %q, wanted %q", string(gotPayload), testPayload)
+	}
+	if err = verifier.VerifySignature(bytes.NewReader(sig), bytes.NewReader(gotPayload)); err != nil {
+		t.Errorf("VerifySignature() returned error: %v", err)
+	}
+}