Merge pull request #1950 from Jamstah/easy-verify-options

Verify signatures from a list of public keys

cmd/skopeo/signing.go

@@ -6,6 +6,7 @@ import (
 	"fmt"
 	"io"
 	"os"
+	"strings"
 
 	"github.com/containers/image/v5/pkg/cli"
 	"github.com/containers/image/v5/signature"
@@ -41,12 +42,12 @@ func (opts *standaloneSignOptions) run(args []string, stdout io.Writer) error {
 
 	manifest, err := os.ReadFile(manifestPath)
 	if err != nil {
-		return fmt.Errorf("Error reading %s: %v", manifestPath, err)
+		return fmt.Errorf("Error reading %s: %w", manifestPath, err)
 	}
 
 	mech, err := signature.NewGPGSigningMechanism()
 	if err != nil {
-		return fmt.Errorf("Error initializing GPG: %v", err)
+		return fmt.Errorf("Error initializing GPG: %w", err)
 	}
 	defer mech.Close()
 
@@ -57,25 +58,31 @@ func (opts *standaloneSignOptions) run(args []string, stdout io.Writer) error {
 
 	signature, err := signature.SignDockerManifestWithOptions(manifest, dockerReference, mech, fingerprint, &signature.SignOptions{Passphrase: passphrase})
 	if err != nil {
-		return fmt.Errorf("Error creating signature: %v", err)
+		return fmt.Errorf("Error creating signature: %w", err)
 	}
 
 	if err := os.WriteFile(opts.output, signature, 0644); err != nil {
-		return fmt.Errorf("Error writing signature to %s: %v", opts.output, err)
+		return fmt.Errorf("Error writing signature to %s: %w", opts.output, err)
 	}
 	return nil
 }
 
 type standaloneVerifyOptions struct {
+	publicKeyFile string
 }
 
 func standaloneVerifyCmd() *cobra.Command {
 	opts := standaloneVerifyOptions{}
 	cmd := &cobra.Command{
-		Use:   "standalone-verify MANIFEST DOCKER-REFERENCE KEY-FINGERPRINT SIGNATURE",
+		Use:   "standalone-verify MANIFEST DOCKER-REFERENCE KEY-FINGERPRINTS SIGNATURE",
 		Short: "Verify a signature using local files",
-		RunE:  commandAction(opts.run),
+		Long: `Verify a signature using local files
+
+KEY-FINGERPRINTS can be a comma separated list of fingerprints, or "any" if you trust all the keys in the public key file.`,
+		RunE: commandAction(opts.run),
 	}
+	flags := cmd.Flags()
+	flags.StringVar(&opts.publicKeyFile, "public-key-file", "", `File containing public keys. If not specified, will use local GPG keys.`)
 	adjustUsage(cmd)
 	return cmd
 }
@@ -86,29 +93,47 @@ func (opts *standaloneVerifyOptions) run(args []string, stdout io.Writer) error
 	}
 	manifestPath := args[0]
 	expectedDockerReference := args[1]
-	expectedFingerprint := args[2]
+	expectedFingerprints := strings.Split(args[2], ",")
 	signaturePath := args[3]
 
+	if opts.publicKeyFile == "" && len(expectedFingerprints) == 1 && expectedFingerprints[0] == "any" {
+		return fmt.Errorf("Cannot use any fingerprint without a public key file")
+	}
 	unverifiedManifest, err := os.ReadFile(manifestPath)
 	if err != nil {
-		return fmt.Errorf("Error reading manifest from %s: %v", manifestPath, err)
+		return fmt.Errorf("Error reading manifest from %s: %w", manifestPath, err)
 	}
 	unverifiedSignature, err := os.ReadFile(signaturePath)
 	if err != nil {
-		return fmt.Errorf("Error reading signature from %s: %v", signaturePath, err)
+		return fmt.Errorf("Error reading signature from %s: %w", signaturePath, err)
 	}
 
-	mech, err := signature.NewGPGSigningMechanism()
+	var mech signature.SigningMechanism
+	var publicKeyfingerprints []string
+	if opts.publicKeyFile != "" {
+		publicKeys, err := os.ReadFile(opts.publicKeyFile)
+		if err != nil {
+			return fmt.Errorf("Error reading public keys from %s: %w", opts.publicKeyFile, err)
+		}
+		mech, publicKeyfingerprints, err = signature.NewEphemeralGPGSigningMechanism(publicKeys)
+	} else {
+		mech, err = signature.NewGPGSigningMechanism()
+	}
 	if err != nil {
-		return fmt.Errorf("Error initializing GPG: %v", err)
+		return fmt.Errorf("Error initializing GPG: %w", err)
 	}
 	defer mech.Close()
-	sig, err := signature.VerifyDockerManifestSignature(unverifiedSignature, unverifiedManifest, expectedDockerReference, mech, expectedFingerprint)
-	if err != nil {
-		return fmt.Errorf("Error verifying signature: %v", err)
+
+	if len(expectedFingerprints) == 1 && expectedFingerprints[0] == "any" {
+		expectedFingerprints = publicKeyfingerprints
 	}
 
-	fmt.Fprintf(stdout, "Signature verified, digest %s\n", sig.DockerManifestDigest)
+	sig, verificationFingerprint, err := signature.VerifyImageManifestSignatureUsingKeyIdentityList(unverifiedSignature, unverifiedManifest, expectedDockerReference, mech, expectedFingerprints)
+	if err != nil {
+		return fmt.Errorf("Error verifying signature: %w", err)
+	}
+
+	fmt.Fprintf(stdout, "Signature verified using fingerprint %s, digest %s\n", verificationFingerprint, sig.DockerManifestDigest)
 	return nil
 }
 
@@ -141,7 +166,7 @@ func (opts *untrustedSignatureDumpOptions) run(args []string, stdout io.Writer)
 
 	untrustedSignature, err := os.ReadFile(untrustedSignaturePath)
 	if err != nil {
-		return fmt.Errorf("Error reading untrusted signature from %s: %v", untrustedSignaturePath, err)
+		return fmt.Errorf("Error reading untrusted signature from %s: %w", untrustedSignaturePath, err)
 	}
 
 	untrustedInfo, err := signature.GetUntrustedSignatureInformationWithoutVerifying(untrustedSignature)

cmd/skopeo/signing_test.go

@@ -127,11 +127,36 @@ func TestStandaloneVerify(t *testing.T) {
 		dockerReference, fixturesTestKeyFingerprint, "fixtures/corrupt.signature")
 	assertTestFailed(t, out, err, "Error verifying signature")
 
+	// Error using any without a public key file
+	out, err = runSkopeo("standalone-verify", manifestPath,
+		dockerReference, "any", signaturePath)
+	assertTestFailed(t, out, err, "Cannot use any fingerprint without a public key file")
+
 	// Success
 	out, err = runSkopeo("standalone-verify", manifestPath,
 		dockerReference, fixturesTestKeyFingerprint, signaturePath)
 	assert.NoError(t, err)
-	assert.Equal(t, "Signature verified, digest "+fixturesTestImageManifestDigest.String()+"\n", out)
+	assert.Equal(t, "Signature verified using fingerprint "+fixturesTestKeyFingerprint+", digest "+fixturesTestImageManifestDigest.String()+"\n", out)
+
+	// Using multiple fingerprints
+	out, err = runSkopeo("standalone-verify", manifestPath,
+		dockerReference, "0123456789ABCDEF0123456789ABCDEF01234567,"+fixturesTestKeyFingerprint+",DEADBEEFDEADBEEFDEADBEEFDEADBEEFDEADBEEF", signaturePath)
+	assert.NoError(t, err)
+	assert.Equal(t, "Signature verified using fingerprint "+fixturesTestKeyFingerprint+", digest "+fixturesTestImageManifestDigest.String()+"\n", out)
+
+	// Using a public key file
+	t.Setenv("GNUPGHOME", "")
+	out, err = runSkopeo("standalone-verify", "--public-key-file", "fixtures/pubring.gpg", manifestPath,
+		dockerReference, fixturesTestKeyFingerprint, signaturePath)
+	assert.NoError(t, err)
+	assert.Equal(t, "Signature verified using fingerprint "+fixturesTestKeyFingerprint+", digest "+fixturesTestImageManifestDigest.String()+"\n", out)
+
+	// Using a public key file matching any public key
+	t.Setenv("GNUPGHOME", "")
+	out, err = runSkopeo("standalone-verify", "--public-key-file", "fixtures/pubring.gpg", manifestPath,
+		dockerReference, "any", signaturePath)
+	assert.NoError(t, err)
+	assert.Equal(t, "Signature verified using fingerprint "+fixturesTestKeyFingerprint+", digest "+fixturesTestImageManifestDigest.String()+"\n", out)
 }
 
 func TestUntrustedSignatureDump(t *testing.T) {

docs/skopeo-standalone-verify.1.md

@@ -4,7 +4,7 @@
 skopeo\-standalone\-verify - Verify an image signature.
 
 ## SYNOPSIS
-**skopeo standalone-verify** _manifest_ _docker-reference_ _key-fingerprint_ _signature_
+**skopeo standalone-verify** _manifest_ _docker-reference_ _key-fingerprints_ _signature_
 
 ## DESCRIPTION
 
@@ -16,7 +16,7 @@ as per containers-policy.json(5).
 
   _docker-reference_ A docker reference expected to identify the image in the signature
 
-  _key-fingerprint_ Expected identity of the signing key
+  _key-fingerprints_ Identities of trusted signing keys (comma separated), or "any" to trust any known key when using a public key file
 
   _signature_ Path to signature file
 
@@ -28,6 +28,10 @@ as per containers-policy.json(5).
 
 Print usage statement
 
+**--public-key-file** _public key file_
+
+File containing the public keys to use when verifying signatures. If this is not specified, keys from the GPG homedir are used.
+
 ## EXAMPLES
 
 ```console

integration/signing_test.go

@@ -73,7 +73,7 @@ func (s *signingSuite) TestSignVerifySmoke() {
 	assertSkopeoSucceeds(t, "^$", "standalone-sign", "-o", sigOutput.Name(),
 		manifestPath, dockerReference, s.fingerprint)
 
-	expected := fmt.Sprintf("^Signature verified, digest %s\n$", TestImageManifestDigest)
+	expected := fmt.Sprintf("^Signature verified using fingerprint %s, digest %s\n$", s.fingerprint, TestImageManifestDigest)
 	assertSkopeoSucceeds(t, expected, "standalone-verify", manifestPath,
 		dockerReference, s.fingerprint, sigOutput.Name())
 }

systemtest/050-signing.bats

@@ -242,7 +242,7 @@ END_TESTS
                $fingerprint \
                $TESTDIR/busybox.signature
     # manifest digest
-    digest=$(echo "$output" | awk '{print $4;}')
+    digest=$(echo "$output" | awk '{print $NF;}')
     run_skopeo manifest-digest $TESTDIR/busybox/manifest.json
     expect_output $digest
 }