Fix build after https://github.com/xenolf/lego/commit/0e26b

Fix up last-second changes

Fixes #640

caddy/https/client.go

@@ -34,7 +34,16 @@ var NewACMEClient = func(email string, allowPrompts bool) (*ACMEClient, error) {
 	}
 
 	// The client facilitates our communication with the CA server.
-	client, err := acme.NewClient(CAUrl, &leUser, rsaKeySizeToUse)
+	var kt acme.KeyType
+	if rsaKeySizeToUse == Rsa2048 {
+		kt = acme.RSA2048
+	} else if rsaKeySizeToUse == Rsa4096 {
+		kt = acme.RSA4096
+	} else {
+		// TODO(hkjn): Support more types? Current changes are quick fix for #640.
+		return nil, fmt.Errorf("https: unsupported keysize")
+	}
+	client, err := acme.NewClient(CAUrl, &leUser, kt)
 	if err != nil {
 		return nil, err
 	}

caddy/https/crypto_test.go

@@ -11,7 +11,9 @@ import (
 )
 
 func init() {
-	rsaKeySizeToUse = 128 // make tests faster; small key size OK for testing
+	rsaKeySizeToUse = 2048 // TODO(hkjn): Bring back support for small
+	// keys to speed up tests? Current changes
+	// are quick fix for #640.
 }
 
 func TestSaveAndLoadRSAPrivateKey(t *testing.T) {

caddy/https/user.go

@@ -2,6 +2,7 @@ package https
 
 import (
 	"bufio"
+	"crypto"
 	"crypto/rand"
 	"crypto/rsa"
 	"encoding/json"
@@ -34,7 +35,7 @@ func (u User) GetRegistration() *acme.RegistrationResource {
 }
 
 // GetPrivateKey gets u's private key.
-func (u User) GetPrivateKey() *rsa.PrivateKey {
+func (u User) GetPrivateKey() crypto.PrivateKey {
 	return u.key
 }