Support webauthn (#17957)

Migrate from U2F to Webauthn

Co-authored-by: Andrew Thornton <art27@cantab.net>
Co-authored-by: 6543 <6543@obermui.de>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

vendor/github.com/duo-labs/webauthn/protocol/base64.go

@@ -0,0 +1,41 @@
+package protocol
+
+import (
+	"bytes"
+	"encoding/base64"
+	"reflect"
+)
+
+// URLEncodedBase64 represents a byte slice holding URL-encoded base64 data.
+// When fields of this type are unmarshaled from JSON, the data is base64
+// decoded into a byte slice.
+type URLEncodedBase64 []byte
+
+// UnmarshalJSON base64 decodes a URL-encoded value, storing the result in the
+// provided byte slice.
+func (dest *URLEncodedBase64) UnmarshalJSON(data []byte) error {
+	if bytes.Equal(data, []byte("null")) {
+		return nil
+	}
+
+	// Trim the leading spaces
+	data = bytes.Trim(data, "\"")
+	out := make([]byte, base64.RawURLEncoding.DecodedLen(len(data)))
+	n, err := base64.RawURLEncoding.Decode(out, data)
+	if err != nil {
+		return err
+	}
+
+	v := reflect.ValueOf(dest).Elem()
+	v.SetBytes(out[:n])
+	return nil
+}
+
+// MarshalJSON base64 encodes a non URL-encoded value, storing the result in the
+// provided byte slice.
+func (data URLEncodedBase64) MarshalJSON() ([]byte, error) {
+	if data == nil {
+		return []byte("null"), nil
+	}
+	return []byte(`"` + base64.RawURLEncoding.EncodeToString(data) + `"`), nil
+}