Enable GPG Signing of Commits

api/v1alpha1/imageupdateautomation_types.go

@@ -106,6 +106,9 @@ type CommitSpec struct {
 	// AuthorEmail gives the email to provide when making a commit
 	// +required
 	AuthorEmail string `json:"authorEmail"`
+	// SigningKey provides the option to sign commits with a GPG key
+	// +optional
+	SigningKey *SigningKey `json:"signingKey,omitempty"`
 	// MessageTemplate provides a template for the commit message,
 	// into which will be interpolated the details of the change made.
 	// +optional
@@ -142,6 +145,16 @@ type ImageUpdateAutomationStatus struct {
 	meta.ReconcileRequestStatus `json:",inline"`
 }
 
+// SigningKey references a Kubernetes secret that contains a GPG keypair
+type SigningKey struct {
+	// SecretRef holds the name to a secret that contains a 'git.asc' key
+	// corresponding to the ASCII Armored file containing the GPG signing
+	// keypair as the value. It must be in the same namespace as the
+	// ImageUpdateAutomation.
+	// +required
+	SecretRef meta.LocalObjectReference `json:"secretRef,omitempty"`
+}
+
 const (
 	// GitNotAvailableReason is used for ConditionReady when the
 	// automation run cannot proceed because the git repository is

config/crd/bases/image.toolkit.fluxcd.io_imageupdateautomations.yaml

@@ -80,6 +80,23 @@ spec:
                       message, into which will be interpolated the details of the
                       change made.
                     type: string
+                  signingKey:
+                    description: SigningKey provides the option to sign commits with
+                      a GPG key
+                    properties:
+                      secretRef:
+                        description: SecretRef holds the name to a secret that contains
+                          a 'git.asc' key corresponding to the ASCII Armored file
+                          containing the GPG signing keypair as the value. It must
+                          be in the same namespace as the ImageUpdateAutomation.
+                        properties:
+                          name:
+                            description: Name of the referent
+                            type: string
+                        required:
+                        - name
+                        type: object
+                    type: object
                 required:
                 - authorEmail
                 - authorName

controllers/imageupdateautomation_controller.go

@@ -17,9 +17,11 @@ limitations under the License.
 package controllers
 
 import (
+	"bytes"
 	"context"
 	"errors"
 	"fmt"
+	"golang.org/x/crypto/openpgp"
 	"io/ioutil"
 	"math"
 	"os"
@@ -70,6 +72,8 @@ const defaultMessageTemplate = `Update from image update automation`
 const repoRefKey = ".spec.gitRepository"
 const imagePolicyKey = ".spec.update.imagePolicy"
 
+const signingSecretKey = "git.asc"
+
 // TemplateData is the type of the value given to the commit message
 // template.
 type TemplateData struct {
@@ -227,10 +231,15 @@ func (r *ImageUpdateAutomationReconciler) Reconcile(ctx context.Context, req ctr
 
 	var statusMessage string
 
+	var signingEntity *openpgp.Entity
+	if auto.Spec.Commit.SigningKey != nil {
+		signingEntity, err = r.getSigningEntity(ctx, auto)
+	}
+
 	// The status message depends on what happens next. Since there's
 	// more than one way to succeed, there's some if..else below, and
 	// early returns only on failure.
-	if rev, err := commitAll(ctx, repo, &auto.Spec.Commit, templateValues); err != nil {
+	if rev, err := commitAll(repo, &auto.Spec.Commit, templateValues, signingEntity); err != nil {
 		if err == errNoChanges {
 			r.event(ctx, auto, events.EventSeverityInfo, "no updates made")
 			log.V(debug).Info("no changes made in working directory; no commit")
@@ -439,7 +448,7 @@ func switchBranch(repo *gogit.Repository, pushBranch string) error {
 
 var errNoChanges error = errors.New("no changes made to working directory")
 
-func commitAll(ctx context.Context, repo *gogit.Repository, commit *imagev1.CommitSpec, values TemplateData) (string, error) {
+func commitAll(repo *gogit.Repository, commit *imagev1.CommitSpec, values TemplateData, ent *openpgp.Entity) (string, error) {
 	working, err := repo.Worktree()
 	if err != nil {
 		return "", err
@@ -473,13 +482,44 @@ func commitAll(ctx context.Context, repo *gogit.Repository, commit *imagev1.Comm
 			Email: commit.AuthorEmail,
 			When:  time.Now(),
 		},
+		SignKey: ent,
 	}); err != nil {
 		return "", err
 	}
 
 	return rev.String(), nil
 }
 
+// getSigningEntity retrieves an OpenPGP entity referenced by the
+// provided imagev1.ImageUpdateAutomation for git commit signing
+func (r *ImageUpdateAutomationReconciler) getSigningEntity(ctx context.Context, auto imagev1.ImageUpdateAutomation) (*openpgp.Entity, error) {
+	// get kubernetes secret
+	secretName := types.NamespacedName{
+		Namespace: auto.GetNamespace(),
+		Name:      auto.Spec.Commit.SigningKey.SecretRef.Name,
+	}
+	var secret corev1.Secret
+	if err := r.Get(ctx, secretName, &secret); err != nil {
+		return nil, fmt.Errorf("could not find signing key secret '%s': %w", secretName, err)
+	}
+
+	// get data from secret
+	data, ok := secret.Data[signingSecretKey]
+	if !ok {
+		return nil, fmt.Errorf("signing key secret '%s' does not contain a 'git.asc' key", secretName)
+	}
+
+	// read entity from secret value
+	entities, err := openpgp.ReadArmoredKeyRing(bytes.NewReader(data))
+	if err != nil {
+		return nil, fmt.Errorf("could not read signing key from secret '%s': %w", secretName, err)
+	}
+	if len(entities) > 1 {
+		return nil, fmt.Errorf("multiple entities read from secret '%s', could not determine which signing key to use", secretName)
+	}
+	return entities[0], nil
+}
+
 // push pushes the branch given to the origin using the git library
 // indicated by `impl`. It's passed both the path to the repo and a
 // gogit.Repository value, since the latter may as well be used if the

controllers/update_test.go

@@ -20,6 +20,8 @@ import (
 	"bytes"
 	"context"
 	"fmt"
+	"golang.org/x/crypto/openpgp"
+	"golang.org/x/crypto/openpgp/armor"
 	"io/ioutil"
 	"math/rand"
 	"net/url"
@@ -388,6 +390,165 @@ Images:
 		})
 	})
 
+	Context("commit signing", func() {
+
+		var (
+			localRepo *git.Repository
+			pgpEntity *openpgp.Entity
+		)
+
+		BeforeEach(func() {
+			Expect(initGitRepo(gitServer, "testdata/appconfig", branch, repositoryPath)).To(Succeed())
+			repoURL := gitServer.HTTPAddressWithCredentials() + repositoryPath
+			var err error
+			localRepo, err = git.Clone(memory.NewStorage(), memfs.New(), &git.CloneOptions{
+				URL:           repoURL,
+				RemoteName:    "origin",
+				ReferenceName: plumbing.NewBranchReferenceName(branch),
+			})
+			Expect(err).ToNot(HaveOccurred())
+
+			gitRepoKey := types.NamespacedName{
+				Name:      "image-auto-" + randStringRunes(5),
+				Namespace: namespace.Name,
+			}
+			gitRepo := &sourcev1.GitRepository{
+				ObjectMeta: metav1.ObjectMeta{
+					Name:      gitRepoKey.Name,
+					Namespace: namespace.Name,
+				},
+				Spec: sourcev1.GitRepositorySpec{
+					URL:      repoURL,
+					Interval: metav1.Duration{Duration: time.Minute},
+				},
+			}
+			Expect(k8sClient.Create(context.Background(), gitRepo)).To(Succeed())
+			policyKey := types.NamespacedName{
+				Name:      "policy-" + randStringRunes(5),
+				Namespace: namespace.Name,
+			}
+			// NB not testing the image reflector controller; this
+			// will make a "fully formed" ImagePolicy object.
+			policy := &imagev1_reflect.ImagePolicy{
+				ObjectMeta: metav1.ObjectMeta{
+					Name:      policyKey.Name,
+					Namespace: policyKey.Namespace,
+				},
+				Spec: imagev1_reflect.ImagePolicySpec{
+					ImageRepositoryRef: meta.LocalObjectReference{
+						Name: "not-expected-to-exist",
+					},
+					Policy: imagev1_reflect.ImagePolicyChoice{
+						SemVer: &imagev1_reflect.SemVerPolicy{
+							Range: "1.x",
+						},
+					},
+				},
+				Status: imagev1_reflect.ImagePolicyStatus{
+					LatestImage: "helloworld:v1.0.0",
+				},
+			}
+			Expect(k8sClient.Create(context.Background(), policy)).To(Succeed())
+			Expect(k8sClient.Status().Update(context.Background(), policy)).To(Succeed())
+
+			// Insert a setter reference into the deployment file,
+			// before creating the automation object itself.
+			commitInRepo(repoURL, branch, "Install setter marker", func(tmp string) {
+				replaceMarker(tmp, policyKey)
+			})
+
+			// pull the head commit we just pushed, so it's not
+			// considered a new commit when checking for a commit
+			// made by automation.
+			waitForNewHead(localRepo, branch)
+
+			// generate keypair for signing
+			pgpEntity, err = openpgp.NewEntity("", "", "", nil)
+			Expect(err).ToNot(HaveOccurred())
+
+			// configure OpenPGP armor encoder
+			b := bytes.NewBuffer(nil)
+			w, err := armor.Encode(b, openpgp.PrivateKeyType, nil)
+			Expect(err).ToNot(HaveOccurred())
+
+			// serialize private key
+			err = pgpEntity.SerializePrivate(w, nil)
+			Expect(err).ToNot(HaveOccurred())
+			err = w.Close()
+			Expect(err).ToNot(HaveOccurred())
+
+			// create the secret containing signing key
+			sec := &corev1.Secret{
+				Data: map[string][]byte{
+					"git.asc": b.Bytes(),
+				},
+			}
+			sec.Name = "signing-key-secret-" + randStringRunes(5)
+			sec.Namespace = namespace.Name
+			Expect(k8sClient.Create(context.Background(), sec)).To(Succeed())
+
+			// now create the automation object, and let it (one
+			// hopes!) make a commit itself.
+			updateKey := types.NamespacedName{
+				Namespace: namespace.Name,
+				Name:      "update-test",
+			}
+			updateBySetters := &imagev1.ImageUpdateAutomation{
+				ObjectMeta: metav1.ObjectMeta{
+					Name:      updateKey.Name,
+					Namespace: updateKey.Namespace,
+				},
+				Spec: imagev1.ImageUpdateAutomationSpec{
+					Interval: metav1.Duration{Duration: 2 * time.Hour}, // this is to ensure any subsequent run should be outside the scope of the testing
+					Checkout: imagev1.GitCheckoutSpec{
+						GitRepositoryRef: meta.LocalObjectReference{
+							Name: gitRepoKey.Name,
+						},
+						Branch: branch,
+					},
+					Update: &imagev1.UpdateStrategy{
+						Strategy: imagev1.UpdateStrategySetters,
+					},
+					Commit: imagev1.CommitSpec{
+						SigningKey: &imagev1.SigningKey{
+							SecretRef: meta.LocalObjectReference{Name: sec.Name},
+						},
+					},
+				},
+			}
+
+			Expect(k8sClient.Create(context.Background(), updateBySetters)).To(Succeed())
+			// wait for a new commit to be made by the controller
+			waitForNewHead(localRepo, branch)
+		})
+
+		AfterEach(func() {
+			Expect(k8sClient.Delete(context.Background(), namespace)).To(Succeed())
+		})
+
+		It("signs the commit with the generated GPG key", func() {
+			head, _ := localRepo.Head()
+			commit, err := localRepo.CommitObject(head.Hash())
+			Expect(err).ToNot(HaveOccurred())
+
+			// configure OpenPGP armor encoder
+			b := bytes.NewBuffer(nil)
+			w, err := armor.Encode(b, openpgp.PublicKeyType, nil)
+			Expect(err).ToNot(HaveOccurred())
+
+			// serialize public key
+			err = pgpEntity.Serialize(w)
+			Expect(err).ToNot(HaveOccurred())
+			err = w.Close()
+			Expect(err).ToNot(HaveOccurred())
+
+			// verify commit
+			ent, err := commit.Verify(b.String())
+			Expect(err).ToNot(HaveOccurred())
+			Expect(ent.PrimaryKey.Fingerprint).To(Equal(pgpEntity.PrimaryKey.Fingerprint))
+		})
+	})
+
 	endToEnd := func(impl, proto string) func() {
 		return func() {
 			var (