Add keyRing.GetVerifiedSignatureTimestamp()

Add a function to verify a detached signature and access
its creation time.

crypto/signature_test.go

@@ -1,10 +1,14 @@
 package crypto
 
 import (
+	"bytes"
 	"errors"
+	"io"
+	"io/ioutil"
 	"regexp"
 	"testing"
 
+	"github.com/ProtonMail/go-crypto/openpgp/packet"
 	"github.com/ProtonMail/gopenpgp/v2/constants"
 	"github.com/stretchr/testify/assert"
 )
@@ -73,3 +77,120 @@ func TestVerifyBinDetachedSig(t *testing.T) {
 		t.Fatal("Cannot verify binary signature:", verificationError)
 	}
 }
+
+func Test_KeyRing_GetVerifiedSignatureTimestampSuccess(t *testing.T) {
+	message := NewPlainMessageFromString("Hello world!")
+	var time int64 = 1600000000
+	pgp.latestServerTime = time
+	defer func() {
+		pgp.latestServerTime = testTime
+	}()
+	signature, err := keyRingTestPrivate.SignDetached(message)
+	if err != nil {
+		t.Errorf("Got an error while generating the signature: %v", err)
+	}
+	actualTime, err := keyRingTestPublic.GetVerifiedSignatureTimestamp(message, signature, 0)
+	if err != nil {
+		t.Errorf("Got an error while parsing the signature creation time: %v", err)
+	}
+	if time != actualTime {
+		t.Errorf("Expected creation time to be %d, got %d", time, actualTime)
+	}
+}
+
+func Test_KeyRing_GetVerifiedSignatureWithTwoKeysTimestampSuccess(t *testing.T) {
+	publicKey1Armored, err := ioutil.ReadFile("testdata/signature/publicKey1")
+	if err != nil {
+		t.Errorf("Couldn't read the public key file: %v", err)
+	}
+	publicKey1 := parseKey(t, string(publicKey1Armored))
+	publicKey2Armored, err := ioutil.ReadFile("testdata/signature/publicKey2")
+	if err != nil {
+		t.Errorf("Couldn't read the public key file: %v", err)
+	}
+	publicKey2 := parseKey(t, string(publicKey2Armored))
+	message := NewPlainMessageFromString("hello world")
+	signatureArmored, err := ioutil.ReadFile("testdata/signature/detachedSigSignedTwice")
+	if err != nil {
+		t.Errorf("Couldn't read the signature file: %v", err)
+	}
+	signature, err := NewPGPSignatureFromArmored(string(signatureArmored))
+	if err != nil {
+		t.Errorf("Got an error while parsing the signature: %v", err)
+	}
+	time1 := getTimestampOfIssuer(signature, publicKey1.GetKeyID())
+	time2 := getTimestampOfIssuer(signature, publicKey2.GetKeyID())
+	keyRing, err := NewKeyRing(publicKey1)
+	if err != nil {
+		t.Errorf("Got an error while building the key ring: %v", err)
+	}
+	err = keyRing.AddKey(publicKey2)
+	if err != nil {
+		t.Errorf("Got an error while adding key 2 to the key ring: %v", err)
+	}
+	actualTime, err := keyRing.GetVerifiedSignatureTimestamp(message, signature, 0)
+	if err != nil {
+		t.Errorf("Got an error while parsing the signature creation time: %v", err)
+	}
+	if time1 != actualTime {
+		t.Errorf("Expected creation time to be %d, got %d", time1, actualTime)
+	}
+	if time2 == actualTime {
+		t.Errorf("Expected creation time to be different from %d", time2)
+	}
+}
+
+func parseKey(t *testing.T, keyArmored string) *Key {
+	key, err := NewKeyFromArmored(keyArmored)
+	if err != nil {
+		t.Errorf("Couldn't parse key: %v", err)
+		return nil
+	}
+	return key
+}
+
+func getTimestampOfIssuer(signature *PGPSignature, keyID uint64) int64 {
+	packets := packet.NewReader(bytes.NewReader(signature.Data))
+	var err error
+	var p packet.Packet
+	for {
+		p, err = packets.Next()
+		if errors.Is(err, io.EOF) {
+			break
+		}
+		if err != nil {
+			continue
+		}
+		sigPacket, ok := p.(*packet.Signature)
+		if !ok {
+			continue
+		}
+		var outBuf bytes.Buffer
+		err = sigPacket.Serialize(&outBuf)
+		if err != nil {
+			continue
+		}
+		if *sigPacket.IssuerKeyId == keyID {
+			return sigPacket.CreationTime.Unix()
+		}
+	}
+	return -1
+}
+
+func Test_KeyRing_GetVerifiedSignatureTimestampError(t *testing.T) {
+	message := NewPlainMessageFromString("Hello world!")
+	var time int64 = 1600000000
+	pgp.latestServerTime = time
+	defer func() {
+		pgp.latestServerTime = testTime
+	}()
+	signature, err := keyRingTestPrivate.SignDetached(message)
+	if err != nil {
+		t.Errorf("Got an error while generating the signature: %v", err)
+	}
+	message_corrupted := NewPlainMessageFromString("Ciao world!")
+	_, err = keyRingTestPublic.GetVerifiedSignatureTimestamp(message_corrupted, signature, 0)
+	if err == nil {
+		t.Errorf("Expected an error while parsing the creation time of a wrong signature, got nil")
+	}
+}