Add support for the crypto refresh in v2 (#265)

This commit adds support for the OpenPGP crypto-refresh.
- Updates go-crypto dependency to v1.1.0-alpha.1
- Adapts the session key logic to handle PKESK/SKESK v6 packets without an algorithm attached
- Updates the min go version to 1.17 as requires by  go-crypto v1.1.0-alpha.1
- Update the cricl dependency to 1.3.7 matching go-crypto
Not supported:
- crypto-refresh intended recipients
- v6 key generation

crypto/key_clear.go

@@ -8,8 +8,12 @@ import (
 
 	"github.com/ProtonMail/go-crypto/openpgp/ecdh"
 	"github.com/ProtonMail/go-crypto/openpgp/ecdsa"
+	"github.com/ProtonMail/go-crypto/openpgp/ed25519"
+	"github.com/ProtonMail/go-crypto/openpgp/ed448"
 	"github.com/ProtonMail/go-crypto/openpgp/eddsa"
 	"github.com/ProtonMail/go-crypto/openpgp/elgamal"
+	"github.com/ProtonMail/go-crypto/openpgp/x25519"
+	"github.com/ProtonMail/go-crypto/openpgp/x448"
 )
 
 func (sk *SessionKey) Clear() (ok bool) {
@@ -61,6 +65,14 @@ func clearPrivateKey(privateKey interface{}) error {
 		return clearEdDSAPrivateKey(priv)
 	case *ecdh.PrivateKey:
 		return clearECDHPrivateKey(priv)
+	case *x25519.PrivateKey:
+		return clearX25519PrivateKey(priv)
+	case *ed25519.PrivateKey:
+		return clearEd25519PrivateKey(priv)
+	case *x448.PrivateKey:
+		return clearX448PrivateKey(priv)
+	case *ed448.PrivateKey:
+		return clearEd448PrivateKey(priv)
 	default:
 		return errors.New("gopenpgp: unknown private key")
 	}
@@ -126,3 +138,27 @@ func clearECDHPrivateKey(priv *ecdh.PrivateKey) error {
 
 	return nil
 }
+
+func clearX25519PrivateKey(priv *x25519.PrivateKey) error {
+	clearMem(priv.Secret)
+
+	return nil
+}
+
+func clearEd25519PrivateKey(priv *ed25519.PrivateKey) error {
+	clearMem(priv.Key[:ed25519.SeedSize])
+
+	return nil
+}
+
+func clearX448PrivateKey(priv *x448.PrivateKey) error {
+	clearMem(priv.Secret)
+
+	return nil
+}
+
+func clearEd448PrivateKey(priv *ed448.PrivateKey) error {
+	clearMem(priv.Key[:ed448.SeedSize])
+
+	return nil
+}