treewide: implement serializer interface for socket API

For the socket API, the cmcd and testtool used CBOR
serialization for the payloads (regardless of the
serialization of metadata and attestation reports).

This commit introduces the socketApiSerializer configuration
for the testtool and adds automatic serialization detection
for socket API requests in the cmcd. This makes it possible
to interact with the cmcd socket API without requiring
CBOR support.

Signed-off-by: Simon Ott <[email protected]>

api/api.go

@@ -26,7 +26,6 @@ import (
 	"fmt"
 	"net"
 
-	"github.com/fxamacker/cbor/v2"
 	log "github.com/sirupsen/logrus"
 )
 
@@ -203,7 +202,7 @@ func SignerOptsToHash(opts crypto.SignerOpts) (HashFunction, error) {
 //
 //	Len uint32 -> Length of the payload to be sent
 //	Type uint32 -> Type of the payload
-//	payload []byte -> CBOR-encoded payload
+//	payload []byte -> encoded payload
 func Receive(conn net.Conn) ([]byte, uint32, error) {
 
 	// If unix domain sockets are used, set the write buffer size
@@ -260,24 +259,14 @@ func Receive(conn net.Conn) ([]byte, uint32, error) {
 
 	log.Tracef("Received payload length %v", payloadLen)
 
-	if msgType == TypeError {
-		resp := new(SocketError)
-		err = cbor.Unmarshal(payload.Bytes(), resp)
-		if err != nil {
-			return nil, 0, fmt.Errorf("failed to unmarshal error response")
-		} else {
-			return nil, 0, fmt.Errorf("server responded with error: %v", resp.Msg)
-		}
-	}
-
 	return payload.Bytes(), msgType, nil
 }
 
 // Send sends data to a socket with the following format
 //
 //	Len uint32 -> Length of the payload to be sent
 //	Type uint32 -> Type of the payload
-//	payload []byte -> CBOR-encoded payload
+//	payload []byte -> encoded payload
 func Send(conn net.Conn, payload []byte, t uint32) error {
 
 	if len(payload) > MaxMsgLen {
@@ -320,17 +309,3 @@ func Send(conn net.Conn, payload []byte, t uint32) error {
 
 	return nil
 }
-
-func SendError(conn net.Conn, format string, args ...interface{}) error {
-	msg := fmt.Sprintf(format, args...)
-	log.Warn(msg)
-	resp := &SocketError{
-		Msg: msg,
-	}
-	payload, err := cbor.Marshal(resp)
-	if err != nil {
-		return fmt.Errorf("failed to marshal error response: %v", err)
-	}
-
-	return Send(conn, payload, TypeError)
-}