config: fix unmarshalling of secret URLs (#1663)

* config: fix unmarshalling of secret URLs

* Add comment describing why we need the special case

Signed-off-by: Simon Pasquier <spasquie@redhat.com>

config/config.go

@@ -29,13 +29,25 @@ import (
 	"gopkg.in/yaml.v2"
 )
 
+const secretToken = "<secret>"
+
+var secretTokenJSON string
+
+func init() {
+	b, err := json.Marshal(secretToken)
+	if err != nil {
+		panic(err)
+	}
+	secretTokenJSON = string(b)
+}
+
 // Secret is a string that must not be revealed on marshaling.
 type Secret string
 
 // MarshalYAML implements the yaml.Marshaler interface.
 func (s Secret) MarshalYAML() (interface{}, error) {
 	if s != "" {
-		return "<secret>", nil
+		return secretToken, nil
 	}
 	return nil, nil
 }
@@ -48,7 +60,7 @@ func (s *Secret) UnmarshalYAML(unmarshal func(interface{}) error) error {
 
 // MarshalJSON implements the json.Marshaler interface.
 func (s Secret) MarshalJSON() ([]byte, error) {
-	return json.Marshal("<secret>")
+	return json.Marshal(secretToken)
 }
 
 // URL is a custom type that represents an HTTP or HTTPS URL and allows validation at configuration load time.
@@ -112,23 +124,41 @@ type SecretURL URL
 // MarshalYAML implements the yaml.Marshaler interface for SecretURL.
 func (s SecretURL) MarshalYAML() (interface{}, error) {
 	if s.URL != nil {
-		return "<secret>", nil
+		return secretToken, nil
 	}
 	return nil, nil
 }
 
 // UnmarshalYAML implements the yaml.Unmarshaler interface for SecretURL.
 func (s *SecretURL) UnmarshalYAML(unmarshal func(interface{}) error) error {
+	var str string
+	if err := unmarshal(&str); err != nil {
+		return err
+	}
+	// In order to deserialize a previously serialized configuration (eg from
+	// the Alertmanager API with amtool), `<secret>` needs to be treated
+	// specially, as it isn't a valid URL.
+	if str == secretToken {
+		s.URL = &url.URL{}
+		return nil
+	}
 	return unmarshal((*URL)(s))
 }
 
 // MarshalJSON implements the json.Marshaler interface for SecretURL.
 func (s SecretURL) MarshalJSON() ([]byte, error) {
-	return json.Marshal("<secret>")
+	return json.Marshal(secretToken)
 }
 
 // UnmarshalJSON implements the json.Marshaler interface for SecretURL.
 func (s *SecretURL) UnmarshalJSON(data []byte) error {
+	// In order to deserialize a previously serialized configuration (eg from
+	// the Alertmanager API with amtool), `<secret>` needs to be treated
+	// specially, as it isn't a valid URL.
+	if string(data) == secretToken || string(data) == secretTokenJSON {
+		s.URL = &url.URL{}
+		return nil
+	}
 	return json.Unmarshal(data, (*URL)(s))
 }
 

config/config_test.go

@@ -346,12 +346,24 @@ func TestMarshalSecretURL(t *testing.T) {
 	// u003c -> "<"
 	// u003e -> ">"
 	require.Equal(t, "\"\\u003csecret\\u003e\"", string(c), "SecretURL not properly elided in JSON.")
+	// Check that the marshaled data can be unmarshaled again.
+	out := &SecretURL{}
+	err = json.Unmarshal(c, out)
+	if err != nil {
+		t.Fatal(err)
+	}
 
 	c, err = yaml.Marshal(u)
 	if err != nil {
 		t.Fatal(err)
 	}
 	require.Equal(t, "<secret>\n", string(c), "SecretURL not properly elided in YAML.")
+	// Check that the marshaled data can be unmarshaled again.
+	out = &SecretURL{}
+	err = yaml.Unmarshal(c, &out)
+	if err != nil {
+		t.Fatal(err)
+	}
 }
 
 func TestUnmarshalSecretURL(t *testing.T) {