fix: allow RFC3339 encoded time strings

Fixes #292

pkg/oidc/types.go

@@ -184,6 +184,30 @@ func NowTime() Time {
 	return FromTime(time.Now())
 }
 
+func (ts *Time) UnmarshalJSON(data []byte) error {
+	var v any
+	if err := json.Unmarshal(data, &v); err != nil {
+		return fmt.Errorf("oidc.Time: %w", err)
+	}
+	switch x := v.(type) {
+	case float64:
+		*ts = Time(x)
+	case string:
+		// Compatibility with Auth0:
+		// https://github.com/zitadel/oidc/issues/292
+		tt, err := time.Parse(time.RFC3339, x)
+		if err != nil {
+			return fmt.Errorf("oidc.Time: %w", err)
+		}
+		*ts = FromTime(tt)
+	case nil:
+		*ts = 0
+	default:
+		return fmt.Errorf("oidc.Time: unable to parse type %T with value %v", x, x)
+	}
+	return nil
+}
+
 type RequestObject struct {
 	Issuer   string   `json:"iss"`
 	Audience Audience `json:"aud"`

pkg/oidc/types_test.go

@@ -466,3 +466,57 @@ func TestNewEncoder(t *testing.T) {
 	schema.NewDecoder().Decode(&b, values)
 	assert.Equal(t, a, b)
 }
+
+func TestTime_UnmarshalJSON(t *testing.T) {
+	type dst struct {
+		UpdatedAt Time `json:"updated_at"`
+	}
+	tests := []struct {
+		name    string
+		json    string
+		want    dst
+		wantErr bool
+	}{
+		{
+			name: "RFC3339", // https://github.com/zitadel/oidc/issues/292
+			json: `{"updated_at": "2021-05-11T21:13:25.566Z"}`,
+			want: dst{UpdatedAt: 1620767605},
+		},
+		{
+			name: "int",
+			json: `{"updated_at":1620767605}`,
+			want: dst{UpdatedAt: 1620767605},
+		},
+		{
+			name:    "time parse error",
+			json:    `{"updated_at":"foo"}`,
+			wantErr: true,
+		},
+		{
+			name: "null",
+			json: `{"updated_at":null}`,
+		},
+		{
+			name:    "invalid type",
+			json:    `{"updated_at":["foo","bar"]}`,
+			wantErr: true,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			var got dst
+			err := json.Unmarshal([]byte(tt.json), &got)
+			if tt.wantErr {
+				assert.Error(t, err)
+			} else {
+				require.NoError(t, err)
+			}
+			assert.Equal(t, tt.want, got)
+		})
+	}
+	t.Run("syntax error", func(t *testing.T) {
+		var ts Time
+		err := ts.UnmarshalJSON([]byte{'~'})
+		assert.Error(t, err)
+	})
+}