Integrate signature discovery client into attestation agent.

.github/workflows/ci.yml

@@ -68,6 +68,10 @@ jobs:
         if: runner.os == 'Windows'
       - name: Build all modules
         run: go build -v ./... ./cmd/... ./launcher/...
+      - name: Run specific tests under root permission
+        run: |
+          GO_EXECUTABLE_PATH=$(which go)
+          sudo $GO_EXECUTABLE_PATH test -v -run "(TestFetchContainerImageSignatures|TestFetchImageSignaturesDockerPublic)" ./launcher
       - name: Test all modules
         run: go test -v ./... ./cmd/... ./launcher/...
 

launcher/agent/agent.go

@@ -15,6 +15,7 @@ import (
 
 	"github.com/google/go-tpm-tools/cel"
 	"github.com/google/go-tpm-tools/client"
+	"github.com/google/go-tpm-tools/launcher/internal/oci"
 	"github.com/google/go-tpm-tools/launcher/verifier"
 	pb "github.com/google/go-tpm-tools/proto/attest"
 )
@@ -23,6 +24,7 @@ var defaultCELHashAlgo = []crypto.Hash{crypto.SHA256, crypto.SHA1}
 
 type tpmKeyFetcher func(rw io.ReadWriter) (*client.Key, error)
 type principalIDTokenFetcher func(audience string) ([][]byte, error)
+type containerImageSignaturesFetcher func(ctx context.Context) []oci.Signature
 
 // AttestationAgent is an agent that interacts with GCE's Attestation Service
 // to Verify an attestation message. It is an interface instead of a concrete
@@ -33,24 +35,27 @@ type AttestationAgent interface {
 }
 
 type agent struct {
-	tpm              io.ReadWriteCloser
-	akFetcher        tpmKeyFetcher
-	client           verifier.Client
-	principalFetcher principalIDTokenFetcher
-	cosCel           cel.CEL
+	tpm               io.ReadWriteCloser
+	akFetcher         tpmKeyFetcher
+	client            verifier.Client
+	principalFetcher  principalIDTokenFetcher
+	signaturesFetcher containerImageSignaturesFetcher
+	cosCel            cel.CEL
 }
 
 // CreateAttestationAgent returns an agent capable of performing remote
 // attestation using the machine's (v)TPM to GCE's Attestation Service.
 // - tpm is a handle to the TPM on the instance
 // - akFetcher is a func to fetch an attestation key: see go-tpm-tools/client.
 // - principalFetcher is a func to fetch GCE principal tokens for a given audience.
-func CreateAttestationAgent(tpm io.ReadWriteCloser, akFetcher tpmKeyFetcher, verifierClient verifier.Client, principalFetcher principalIDTokenFetcher) AttestationAgent {
+// - signaturesFetcher is a func to fetch container image signatures associated with the running workload.
+func CreateAttestationAgent(tpm io.ReadWriteCloser, akFetcher tpmKeyFetcher, verifierClient verifier.Client, principalFetcher principalIDTokenFetcher, signaturesFetcher containerImageSignaturesFetcher) AttestationAgent {
 	return &agent{
-		tpm:              tpm,
-		client:           verifierClient,
-		akFetcher:        akFetcher,
-		principalFetcher: principalFetcher,
+		tpm:               tpm,
+		client:            verifierClient,
+		akFetcher:         akFetcher,
+		principalFetcher:  principalFetcher,
+		signaturesFetcher: signaturesFetcher,
 	}
 }
 
@@ -79,10 +84,13 @@ func (a *agent) Attest(ctx context.Context) ([]byte, error) {
 		return nil, err
 	}
 
+	signatures := a.signaturesFetcher(ctx)
+
 	resp, err := a.client.VerifyAttestation(ctx, verifier.VerifyAttestationRequest{
-		Challenge:      challenge,
-		GcpCredentials: principalTokens,
-		Attestation:    attestation,
+		Challenge:                challenge,
+		GcpCredentials:           principalTokens,
+		Attestation:              attestation,
+		ContainerImageSignatures: signatures,
 	})
 	if err != nil {
 		return nil, err

launcher/agent/agent_test.go

@@ -10,6 +10,7 @@ import (
 	"github.com/golang-jwt/jwt/v4"
 	"github.com/google/go-tpm-tools/client"
 	"github.com/google/go-tpm-tools/internal/test"
+	"github.com/google/go-tpm-tools/launcher/internal/oci"
 	"github.com/google/go-tpm-tools/launcher/verifier/fake"
 )
 
@@ -22,7 +23,7 @@ func TestAttest(t *testing.T) {
 		t.Errorf("Failed to generate signing key %v", err)
 	}
 	verifierClient := fake.NewClient(fakeSigner)
-	agent := CreateAttestationAgent(tpm, client.AttestationKeyECC, verifierClient, placeholderFetcher)
+	agent := CreateAttestationAgent(tpm, client.AttestationKeyECC, verifierClient, placeholderFetcher, signaturesPlaceholderFetcher)
 
 	tokenBytes, err := agent.Attest(context.Background())
 	if err != nil {
@@ -58,3 +59,7 @@ func TestAttest(t *testing.T) {
 func placeholderFetcher(_ string) ([][]byte, error) {
 	return [][]byte{}, nil
 }
+
+func signaturesPlaceholderFetcher(_ context.Context) []oci.Signature {
+	return []oci.Signature{}
+}

launcher/container_runner.go

@@ -15,6 +15,7 @@ import (
 	"path"
 	"strconv"
 	"strings"
+	"sync"
 	"time"
 
 	"cloud.google.com/go/compute/metadata"
@@ -29,6 +30,8 @@ import (
 	"github.com/google/go-tpm-tools/cel"
 	"github.com/google/go-tpm-tools/client"
 	"github.com/google/go-tpm-tools/launcher/agent"
+	internal "github.com/google/go-tpm-tools/launcher/internal/oci"
+	"github.com/google/go-tpm-tools/launcher/internal/signaturediscovery"
 	"github.com/google/go-tpm-tools/launcher/spec"
 	"github.com/google/go-tpm-tools/launcher/verifier"
 	"github.com/google/go-tpm-tools/launcher/verifier/rest"
@@ -79,6 +82,33 @@ const (
 	defaultRefreshJitter = 0.1
 )
 
+func fetchContainerImageSignatures(ctx context.Context, sdClient *signaturediscovery.Client, targetRepos []string, logger *log.Logger) []internal.Signature {
+	signatures := make([][]internal.Signature, len(targetRepos))
+
+	var wg sync.WaitGroup
+	for i, repo := range targetRepos {
+		wg.Add(1)
+		go func(targetRepo string, index int) {
+			defer wg.Done()
+			sigs, err := sdClient.FetchImageSignatures(ctx, targetRepo)
+			if err != nil {
+				logger.Printf("Failed to fetch signatures from the target repo [%s]: %v", targetRepo, err)
+			} else {
+				signatures[index] = sigs
+			}
+		}(repo, i)
+	}
+	wg.Wait()
+
+	var foundSigs []internal.Signature
+	for _, sigs := range signatures {
+		if len(sigs) != 0 {
+			foundSigs = append(foundSigs, sigs...)
+		}
+	}
+	return foundSigs
+}
+
 func fetchImpersonatedToken(ctx context.Context, serviceAccount string, audience string, opts ...option.ClientOption) ([]byte, error) {
 	config := impersonate.IDTokenConfig{
 		Audience:        audience,
@@ -236,14 +266,38 @@ func NewRunner(ctx context.Context, cdClient *containerd.Client, token oauth2.To
 		return nil, fmt.Errorf("failed to create REST verifier client: %v", err)
 	}
 
+	// Fetch container image signatures by using signaturediscovery client.
+	signaturesFetcher := func(ctx context.Context) []internal.Signature {
+		authToken, err := RetrieveAuthToken(mdsClient)
+		if err != nil {
+			logger.Printf("failed to retrieve auth token: %v, using empty auth for image pulling\n", err)
+		}
+		updatedSpec, err := spec.GetLaunchSpec(mdsClient)
+		if err != nil {
+			logger.Println(err)
+			// If can not get launchSpec, default to the old one.
+			updatedSpec = launchSpec
+		}
+		sdClient := getSignatureDiscoveryClient(cdClient, authToken, image.Target())
+		return fetchContainerImageSignatures(ctx, sdClient, updatedSpec.SignedImageRepos, logger)
+	}
+
 	return &ContainerRunner{
 		container,
 		launchSpec,
-		agent.CreateAttestationAgent(tpm, client.GceAttestationKeyECC, verifierClient, principalFetcher),
+		agent.CreateAttestationAgent(tpm, client.GceAttestationKeyECC, verifierClient, principalFetcher, signaturesFetcher),
 		logger,
 	}, nil
 }
 
+func getSignatureDiscoveryClient(cdClient *containerd.Client, token oauth2.Token, imageDesc v1.Descriptor) *signaturediscovery.Client {
+	var remoteOpt containerd.RemoteOpt
+	if token.Valid() {
+		remoteOpt = containerd.WithResolver(Resolver(token.AccessToken))
+	}
+	return signaturediscovery.New(cdClient, imageDesc, remoteOpt)
+}
+
 // getRESTClient returns a REST verifier.Client that points to the given address.
 // It defaults to the Attestation Verifier instance at
 // https://confidentialcomputing.googleapis.com.

launcher/container_runner_test.go

@@ -22,8 +22,11 @@ import (
 	"github.com/containerd/containerd/defaults"
 	"github.com/containerd/containerd/namespaces"
 	"github.com/golang-jwt/jwt/v4"
+	"github.com/google/go-cmp/cmp"
 	"github.com/google/go-tpm-tools/cel"
+	"github.com/google/go-tpm-tools/launcher/internal/signaturediscovery"
 	"github.com/google/go-tpm-tools/launcher/spec"
+	v1 "github.com/opencontainers/image-spec/specs-go/v1"
 	"golang.org/x/oauth2"
 	"google.golang.org/api/option"
 )
@@ -413,6 +416,71 @@ type idTokenResp struct {
 	Token string `json:"token"`
 }
 
+func TestFetchContainerImageSignatures(t *testing.T) {
+	ctx := namespaces.WithNamespace(context.Background(), "test")
+
+	testCases := []struct {
+		name           string
+		targetRepos    []string
+		wantLen        int
+		wantBase64Sigs []string
+	}{
+		{
+			name:        "fetchContainerImageSignatures success",
+			targetRepos: []string{"us-docker.pkg.dev/vegas-codelab-5/cosign-test/base", "us-docker.pkg.dev/vegas-codelab-5/cosign-test/base"},
+			wantLen:     2,
+			wantBase64Sigs: []string{
+				// Check signatures from the OCI image manifest at https://pantheon.corp.google.com/artifacts/docker/vegas-codelab-5/us/cosign-test/base/sha256:1febaa6ac3a5c095435d5276755fb8efcb7f029fefe85cd9bf3ec7de91685b9f;tab=manifest?project=vegas-codelab-5.
+				"MEUCIQDgoiwMiVl1SAI1iePhH6Oeqztms3IwNtN+w0P92HTqQgIgKjJNcHEy0Ep4g4MH1Vd0gAHvbwH9ahD+jlnMP/rXSGE=",
+				"MEUCIQDgoiwMiVl1SAI1iePhH6Oeqztms3IwNtN+w0P92HTqQgIgKjJNcHEy0Ep4g4MH1Vd0gAHvbwH9ahD+jlnMP/rXSGE=",
+			},
+		},
+		{
+			name:        "fetchContainerImageSignatures success with nil target repos",
+			targetRepos: nil,
+			wantLen:     0,
+		},
+		{
+			name:        "fetchContainerImageSignatures success with empty target repos",
+			targetRepos: []string{},
+			wantLen:     0,
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			signedImageDesc := v1.Descriptor{Digest: "sha256:905a0f3b3d6d0fb37bfa448b9e78f833b73f0b19fc97fed821a09cf49e255df1"}
+			sdClient := createTestSignatureDiscoveryClient(t, signedImageDesc)
+			gotSigs := fetchContainerImageSignatures(ctx, sdClient, tc.targetRepos, log.Default())
+			if len(gotSigs) != tc.wantLen {
+				t.Errorf("fetchContainerImageSignatures did not return expected signatures for test case %s, got signatures length %d, but want %d", tc.name, len(gotSigs), tc.wantLen)
+			}
+			var gotBase64Sigs []string
+			for _, gotSig := range gotSigs {
+				base64Sig, err := gotSig.Base64Encoded()
+				if err != nil {
+					t.Fatalf("fetchContainerImageSignatures did not return expected base64 signatures for test case %s: %v", tc.name, err)
+				}
+				gotBase64Sigs = append(gotBase64Sigs, base64Sig)
+			}
+			if !cmp.Equal(gotBase64Sigs, tc.wantBase64Sigs) {
+				t.Errorf("fetchContainerImageSignatures did not return expected signatures for test case %s, got signatures %v, but want %v", tc.name, gotBase64Sigs, tc.wantBase64Sigs)
+			}
+		})
+	}
+}
+
+func createTestSignatureDiscoveryClient(t *testing.T, originalImageDesc v1.Descriptor) *signaturediscovery.Client {
+	t.Helper()
+
+	containerdClient, err := containerd.New(defaults.DefaultAddress)
+	if err != nil {
+		t.Skipf("test needs containerd daemon: %v", err)
+	}
+	t.Cleanup(func() { containerdClient.Close() })
+	return signaturediscovery.New(containerdClient, originalImageDesc)
+}
+
 func TestFetchImpersonatedToken(t *testing.T) {
 	expectedEmail := "test2@google.com"
 

launcher/verifier/client.go

@@ -5,6 +5,7 @@ package verifier
 import (
 	"context"
 
+	"github.com/google/go-tpm-tools/launcher/internal/oci"
 	attestpb "github.com/google/go-tpm-tools/proto/attest"
 )
 
@@ -25,11 +26,12 @@ type Challenge struct {
 
 // VerifyAttestationRequest is passed in on VerifyAttestation. It contains the
 // Challenge from CreateChallenge, optional GcpCredentials linked to the
-// attestation, and the Attestation generated from the TPM.
+// attestation, the Attestation generated from the TPM, and optional container image signatures associated with the workload.
 type VerifyAttestationRequest struct {
-	Challenge      *Challenge
-	GcpCredentials [][]byte
-	Attestation    *attestpb.Attestation
+	Challenge                *Challenge
+	GcpCredentials           [][]byte
+	Attestation              *attestpb.Attestation
+	ContainerImageSignatures []oci.Signature
 }
 
 // VerifyAttestationResponse is the response from a successful

launcher/verifier/rest/rest_network_test.go

@@ -7,6 +7,7 @@ import (
 	"github.com/google/go-tpm-tools/client"
 	"github.com/google/go-tpm-tools/internal/test"
 	"github.com/google/go-tpm-tools/launcher/agent"
+	"github.com/google/go-tpm-tools/launcher/internal/oci"
 	"github.com/google/go-tpm-tools/launcher/verifier"
 	"golang.org/x/oauth2/google"
 	"google.golang.org/api/option"
@@ -36,17 +37,21 @@ func testClient(t *testing.T) verifier.Client {
 	return vClient
 }
 
-func testFetcher(_ string) ([][]byte, error) {
+func testPrincipalIDTokenFetcher(_ string) ([][]byte, error) {
 	return [][]byte{}, nil
 }
 
+func testContainerImageSignaturesFetcher(_ context.Context) []oci.Signature {
+	return []oci.Signature{}
+}
+
 func TestWithAgent(t *testing.T) {
 	vClient := testClient(t)
 
 	tpm := test.GetTPM(t)
 	defer client.CheckedClose(t, tpm)
 
-	agent := agent.CreateAttestationAgent(tpm, client.AttestationKeyECC, vClient, testFetcher)
+	agent := agent.CreateAttestationAgent(tpm, client.AttestationKeyECC, vClient, testPrincipalIDTokenFetcher, testContainerImageSignaturesFetcher)
 	token, err := agent.Attest(context.Background())
 	if err != nil {
 		t.Errorf("failed to attest to Attestation Service: %v", err)