Add EnsureWorloadIdentity function

This commit adds a new function to ensure a GCP identity can
be obtained from the default application credentials. Without
this, devugging signing can be hard as it is the first link
in the impersonation chain.

Signed-off-by: Adolfo García Veytia (Puerco) <adolfo.garcia@uservers.net>

internal/promoter/image/sign.go

@@ -19,11 +19,11 @@ package imagepromoter
 import (
 	"context"
 	"fmt"
-	"os"
 
 	credentials "cloud.google.com/go/iam/credentials/apiv1"
 	"github.com/pkg/errors"
 	"github.com/sirupsen/logrus"
+	"golang.org/x/oauth2/google"
 	credentialspb "google.golang.org/genproto/googleapis/iam/credentials/v1"
 
 	reg "sigs.k8s.io/promo-tools/v3/legacy/dockerregistry"
@@ -35,6 +35,10 @@ const (
 	TestSigningAccount = ""
 )
 
+type tiResponse struct {
+	Email string `json:"email"`
+}
+
 // ValidateStagingSignatures checks if edges (images) have a signature
 // applied during its staging run. If they do it verifies them and
 // returns an error if they are not valid.
@@ -79,10 +83,10 @@ func (di *DefaultPromoterImplementation) ValidateStagingSignatures(
 func (di *DefaultPromoterImplementation) SignImages(
 	opts *options.Options, sc *reg.SyncContext, edges map[reg.PromotionEdge]interface{},
 ) error {
-	signer := sign.New(sign.Default())
-	if err := os.Setenv("COSIGN_EXPERIMENTAL", "YES"); err != nil {
-		return errors.Wrap(err, "setting experimental env")
+	if err := di.EnsureWorkloadIdentity(); err != nil {
+		return errors.Wrap(err, "verifying the workload can has identity credentials")
 	}
+	signer := sign.New(sign.Default())
 	for edge := range edges {
 		imageRef := fmt.Sprintf(
 			"%s/%s@%s",
@@ -131,3 +135,42 @@ func (di *DefaultPromoterImplementation) GetIdentityToken(
 
 	return resp.Token, nil
 }
+
+// EnsureWorkloadIdentity gets a token from the default application
+// credentials and makes sure thers is an identity logged in. This
+// function exists to ensure there is an identity starting the signing
+// impersonation chain.
+func (di *DefaultPromoterImplementation) EnsureWorkloadIdentity() error {
+	ctx := context.Background()
+	cred, err := google.FindDefaultCredentials(ctx)
+	if err != nil {
+		return errors.Wrap(err, "looking for default application credentials")
+	}
+
+	tk, err := cred.TokenSource.Token()
+	if err != nil {
+		return errors.Wrap(err, "getting token from default credentials")
+	}
+	return errors.New("Type: " + tk.TokenType)
+
+	/*
+		res, err := http.NewAgent().Get(
+			fmt.Sprintf(
+				"https://www.googleapis.com/oauth2/v3/tokeninfo?access_token=%s",
+				[]byte(tk.AccessToken)),
+		)
+		if err != nil {
+			return errors.Wrapf(err, "getting token info %s", string(cred.JSON))
+		}
+		tinfo := tiResponse{}
+		if err := json.Unmarshal(res, &tinfo); err != nil {
+			return errors.Wrapf(err, "unmarshalling token info %s", string(res))
+		}
+
+		if tinfo.Email == "" {
+			return errors.New("No identity found in current application credentials")
+		}
+		logrus.Infof("Current worload identity resolves to %s", tinfo.Email)
+		return nil
+	*/
+}

internal/promoter/image/sign_test.go

@@ -37,3 +37,9 @@ func TestGetIdentityToken(t *testing.T) {
 	require.NoError(t, err)
 	require.NotEmpty(t, tok)
 }
+
+func TestEnsureWorkloadIdentity(t *testing.T) {
+	di := DefaultPromoterImplementation{}
+
+	require.NoError(t, di.EnsureWorkloadIdentity())
+}