Test cleartext signature support in gpgme and sequoia backends

image/signature/fixtures/invalid-cleartext.signature

@@ -0,0 +1,19 @@
+-----BEGIN PGP SIGNED MESSAGE-----
+Hash: SHA512
+
+This is not JSON
+-----BEGIN PGP SIGNATURE-----
+Comment: generated with `gpg --homedir . --output invalid-cleartext.signature -u 08CD26E446E2E95249B7A405E932F44B23E8DD43 --clear-sign <<< "This is not JSON"`
+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+=RDU4
+-----END PGP SIGNATURE-----

image/signature/mechanism_gpgme_test.go

@@ -48,3 +48,17 @@ func TestGPGMESigningMechanismSupportsSigning(t *testing.T) {
 	err = mech.SupportsSigning()
 	assert.NoError(t, err)
 }
+
+func TestGPGMESigningMechanismVerifyCleartext(t *testing.T) {
+	mech, err := newGPGSigningMechanismInDirectory(testGPGHomeDirectory)
+	require.NoError(t, err)
+	defer mech.Close()
+
+	// Successful verification of a cleartext signature
+	signature, err := os.ReadFile("./fixtures/invalid-cleartext.signature")
+	require.NoError(t, err)
+	content, signingFingerprint, err := mech.Verify(signature)
+	require.NoError(t, err)
+	assert.Equal(t, []byte("This is not JSON\n"), content)
+	assert.Equal(t, TestKeyFingerprint, signingFingerprint)
+}

image/signature/mechanism_sequoia_test.go

@@ -3,6 +3,7 @@
 package signature
 
 import (
+	"os"
 	"testing"
 
 	"github.com/stretchr/testify/assert"
@@ -34,3 +35,17 @@ func TestSequoiaSigningMechanismSign(t *testing.T) {
 	assert.Error(t, err)
 	assert.IsType(t, SigningNotSupportedError(""), err)
 }
+
+func TestSequoiaSigningMechanismVerifyCleartext(t *testing.T) {
+	mech, err := newGPGSigningMechanismInDirectory(testGPGHomeDirectory)
+	require.NoError(t, err)
+	defer mech.Close()
+
+	// Successful verification of a cleartext signature
+	signature, err := os.ReadFile("./fixtures/invalid-cleartext.signature")
+	require.NoError(t, err)
+	content, signingFingerprint, err := mech.Verify(signature)
+	require.NoError(t, err)
+	assert.Equal(t, []byte("This is not JSON\n"), content)
+	assert.Equal(t, TestKeyFingerprint, signingFingerprint)
+}