multi: send authData in itests

In this commit, we adjust the itests to send authData from the server to
the client and fail the test if the client does not receive the correct
authData from the server.

Author: ellemouton

itest/client_harness.go

@@ -1,8 +1,10 @@
 package itest
 
 import (
+	"bytes"
 	"context"
 	"crypto/tls"
+	"fmt"
 	"net/http"
 
 	"github.com/btcsuite/btcd/btcec/v2"
@@ -45,11 +47,18 @@ func (c *clientHarness) start() error {
 	c.cancel = cancel
 
 	connData := mailbox.NewConnData(
-		c.localStatic, c.remoteStatic, c.passphraseEntropy, nil,
-		func(key *btcec.PublicKey) error {
+		c.localStatic, c.remoteStatic, c.passphraseEntropy,
+		nil, func(key *btcec.PublicKey) error {
 			c.remoteStatic = key
 			return nil
-		}, nil,
+		}, func(data []byte) error {
+			if !bytes.Equal(data, authData) {
+				return fmt.Errorf("incorrect auth data. "+
+					"Expected %x, got %x", authData, data)
+			}
+
+			return nil
+		},
 	)
 
 	transportConn, err := mailbox.NewClient(ctx, connData)

itest/server_harness.go

@@ -12,6 +12,8 @@ import (
 	"google.golang.org/grpc/credentials"
 )
 
+var authData = []byte{1, 2, 3, 4}
+
 type serverHarness struct {
 	serverHost string
 	mockServer *grpc.Server
@@ -64,7 +66,7 @@ func (s *serverHarness) stop() {
 
 func (s *serverHarness) start() error {
 	connData := mailbox.NewConnData(
-		s.localStatic, s.remoteStatic, s.passphraseEntropy, nil,
+		s.localStatic, s.remoteStatic, s.passphraseEntropy, authData,
 		func(key *btcec.PublicKey) error {
 			s.remoteStatic = key
 			return nil

mailbox/conndata.go

@@ -58,7 +58,7 @@ type ConnData struct {
 func NewConnData(localKey keychain.SingleKeyECDH, remoteKey *btcec.PublicKey,
 	passphraseEntropy []byte, authData []byte,
 	onRemoteStatic func(key *btcec.PublicKey) error,
-	onAuthData func(date []byte) error) *ConnData {
+	onAuthData func(data []byte) error) *ConnData {
 
 	return &ConnData{
 		localKey:          localKey,