feat(protocol): ignore padding for base64 url encoding (#95)

This adds support to ignore the trailing padding of base64 URL encoded bytes.

Closes #93

protocol/attestation_test.go

@@ -91,7 +91,7 @@ var testAttestationOptions = []string{
  "user": {
  "name": "self",
  "displayName": "self",
- "id": "2iEAAAAAAAAAAA"
+ "id": "2iEAAAAAAAAAAA=="
  },
  "pubKeyCredParams": [
  {
@@ -116,7 +116,7 @@ var testAttestationOptions = []string{
  "user": {
  "name": "flort",
  "displayName": "flort",
- "id": "1DMAAAAAAAAAAA"
+ "id": "1DMAAAAAAAAAAA=="
  },
  "pubKeyCredParams": [
  {
@@ -142,7 +142,7 @@ var testAttestationOptions = []string{
  "user": {
  "name": "testuser1",
  "displayName": "testuser1",
- "id": "1zMAAAAAAAAAAA"
+ "id": "1zMAAAAAAAAAAA=="
  },
  "pubKeyCredParams": [
  {

protocol/base64.go

@@ -22,8 +22,13 @@ func (e *URLEncodedBase64) UnmarshalJSON(data []byte) error {
  return nil
  }
 
+ // TODO: Investigate this line. It is commented as trimming the leading spaces but appears to trim the leading and trailing double quotes instead.
  // Trim the leading spaces
  data = bytes.Trim(data, "\"")
+
+ // Trim the trailing equal characters.
+ data = bytes.TrimRight(data, "=")
+
  out := make([]byte, base64.RawURLEncoding.DecodedLen(len(data)))
  n, err := base64.RawURLEncoding.Decode(out, data)
  if err != nil {