fix: nil pointer dereference on UserInfoAddress (#207)

* oidc: add test case to reproduce #203

Running the tests will always result in a nil pointer
dereference on UserInfoAddress.

Co-authored-by: Livio Spring <livio.a@gmail.com>

* fix: nil pointer dereference on UserInfoAddress

userinfo.UnmarshalJSON now only sets the Address field
if it was present in the json.
userinfo.GetAddress will always return a non-nil value
of UserInfoAddress to allow for safe chaining of Get functions.

Fixes #203

---------

Co-authored-by: Livio Spring <livio.a@gmail.com>

pkg/oidc/userinfo.go

@@ -167,6 +167,9 @@ func (u *userinfo) IsPhoneNumberVerified() bool {
 }
 
 func (u *userinfo) GetAddress() UserInfoAddress {
+	if u.Address == nil {
+		return &userInfoAddress{}
+	}
 	return u.Address
 }
 
@@ -389,7 +392,11 @@ func (u *userinfo) UnmarshalJSON(data []byte) error {
 	if err := json.Unmarshal(data, &a); err != nil {
 		return err
 	}
+
+	if a.Address != nil {
 		u.Address = a.Address
+	}
+
 	u.UpdatedAt = Time(time.Unix(a.UpdatedAt, 0).UTC())
 
 	if err := json.Unmarshal(data, &u.claims); err != nil {

pkg/oidc/userinfo_test.go

@@ -81,3 +81,39 @@ func TestUserInfoEmailVerifiedUnmarshal(t *testing.T) {
 		}, uie)
 	})
 }
+
+// issue 203 test case.
+func Test_userinfo_GetAddress_issue_203(t *testing.T) {
+	tests := []struct {
+		name string
+		data string
+	}{
+		{
+			name: "with address",
+			data: `{"address":{"street_address":"Test 789\nPostfach 2"},"email":"test","email_verified":true,"name":"Test","phone_number":"0791234567","phone_number_verified":true,"private_claim":"test","sub":"test"}`,
+		},
+		{
+			name: "without address",
+			data: `{"email":"test","email_verified":true,"name":"Test","phone_number":"0791234567","phone_number_verified":true,"private_claim":"test","sub":"test"}`,
+		},
+		{
+			name: "null address",
+			data: `{"address":null,"email":"test","email_verified":true,"name":"Test","phone_number":"0791234567","phone_number_verified":true,"private_claim":"test","sub":"test"}`,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			info := &userinfo{}
+			err := json.Unmarshal([]byte(tt.data), info)
+			assert.NoError(t, err)
+
+			info.GetAddress().GetCountry() //<- used to panic
+
+			// now shortly assure that a marshalling still produces the same as was parsed into the struct
+			marshal, err := json.Marshal(info)
+			assert.NoError(t, err)
+			assert.Equal(t, tt.data, string(marshal))
+		})
+	}
+}