pam/gdm: Use debug assertions only during tests

We may want to enable some checks only during checks or debug builds to
be used in integration tests, so let's abstract things a bit more by
exposing some features at runtime only.

This allows to generate normal builds without debug checks but at the
same time, to avoid having to define special build tags when testing,
leaving the room for using special tags for building different binaries
for integration tests or local debugging.

pam/gdm/export_test.go

@@ -0,0 +1,6 @@
+package gdm
+
+func init() {
+	checkMembersFunc = checkMembersDebug
+	validateJSONFunc = validateJSONDebug
+}

pam/gdm/extension.go

@@ -35,15 +35,19 @@ var ErrProtoNotSupported = errors.New("protocol not supported")
 // ErrInvalidJSON is an error used when processed JSON is not valid.
 var ErrInvalidJSON = errors.New("invalid JSON")
 
-func validateJSON(jsonValue []byte) error {
-	// FIXME: Disable this check in GDM builds, this is only useful
-	// for testing as GDM does JSON sanity check by default.
+func validateJSONDebug(jsonValue []byte) error {
 	if !json.Valid(jsonValue) {
 		return ErrInvalidJSON
 	}
 	return nil
 }
 
+func validateJSONDisabled(jsonValue []byte) error {
+	return nil
+}
+
+var validateJSONFunc = validateJSONDisabled
+
 // IsPamExtensionSupported returns if the provided extension is supported
 func IsPamExtensionSupported(extension string) bool {
 	cExtension := C.CString(extension)
@@ -78,7 +82,7 @@ func allocateJSONProtoMessage() *jsonProtoMessage {
 }
 
 func newJSONProtoMessage(jsonValue []byte) (*jsonProtoMessage, error) {
-	if err := validateJSON(jsonValue); err != nil {
+	if err := validateJSONFunc(jsonValue); err != nil {
 		return nil, err
 	}
 	msg := allocateJSONProtoMessage()
@@ -126,7 +130,7 @@ func (msg *jsonProtoMessage) JSON() ([]byte, error) {
 	jsonLen := C.strlen(msg.json)
 	jsonValue := C.GoBytes(unsafe.Pointer(msg.json), C.int(jsonLen))
 
-	if err := validateJSON(jsonValue); err != nil {
+	if err := validateJSONFunc(jsonValue); err != nil {
 		return nil, err
 	}
 	return jsonValue, nil

pam/gdm/protocol.go

@@ -40,9 +40,7 @@ func NewDataFromJSON(bytes []byte) (*Data, error) {
 	return &gdmData, nil
 }
 
-// FIXME: Do not do this when building the module in release mode, this is
-// just relevant for testing purposes.
-func (d *Data) checkMembers(acceptedMembers []string) error {
+func checkMembersDebug(d *Data, acceptedMembers []string) error {
 	//nolint:govet //We only redirect the value to figure out its type.
 	val := reflect.ValueOf(*d)
 	typ := val.Type()
@@ -66,14 +64,20 @@ func (d *Data) checkMembers(acceptedMembers []string) error {
 	return nil
 }
 
+func checkMembersDisabled(d *Data, acceptedMembers []string) error {
+	return nil
+}
+
+var checkMembersFunc = checkMembersDisabled
+
 // Check allows to check the sanity of a data value.
 func (d *Data) Check() error {
 	switch d.Type {
 	case DataType_unknownType:
 		return fmt.Errorf("unexpected type %v", d.Type.String())
 
 	case DataType_hello:
-		if err := d.checkMembers([]string{"Hello"}); err != nil {
+		if err := checkMembersFunc(d, []string{"Hello"}); err != nil {
 			return err
 		}
 
@@ -90,12 +94,12 @@ func (d *Data) Check() error {
 		if d.Event.Data == nil {
 			return fmt.Errorf("missing event data")
 		}
-		if err := d.checkMembers([]string{"Event"}); err != nil {
+		if err := checkMembersFunc(d, []string{"Event"}); err != nil {
 			return err
 		}
 
 	case DataType_eventAck:
-		if err := d.checkMembers([]string{}); err != nil {
+		if err := checkMembersFunc(d, []string{}); err != nil {
 			return err
 		}
 
@@ -109,7 +113,7 @@ func (d *Data) Check() error {
 		if _, ok := RequestType_name[int32(d.Request.Type)]; !ok {
 			return fmt.Errorf("unexpected request type %v", d.Request.Type)
 		}
-		if err := d.checkMembers([]string{"Request"}); err != nil {
+		if err := checkMembersFunc(d, []string{"Request"}); err != nil {
 			return err
 		}
 
@@ -123,17 +127,17 @@ func (d *Data) Check() error {
 		if _, ok := RequestType_name[int32(d.Response.Type)]; !ok {
 			return fmt.Errorf("unexpected request type %v", d.Response.Type)
 		}
-		if err := d.checkMembers([]string{"Response"}); err != nil {
+		if err := checkMembersFunc(d, []string{"Response"}); err != nil {
 			return err
 		}
 
 	case DataType_poll:
-		if err := d.checkMembers([]string{}); err != nil {
+		if err := checkMembersFunc(d, []string{}); err != nil {
 			return err
 		}
 
 	case DataType_pollResponse:
-		if err := d.checkMembers([]string{"PollResponse"}); err != nil {
+		if err := checkMembersFunc(d, []string{"PollResponse"}); err != nil {
 			return err
 		}
 		for i, response := range d.PollResponse {