GPCM: Append the "Message Of The Day" to a "Login Challenge" message

common/strings.go

@@ -28,6 +28,15 @@ func RandomHexString(n int) string {
 	return string(b)
 }
 
+func UTF16ToByteArray(wideString []uint16) []byte {
+	byteArray := make([]byte, len(wideString)*2)
+	for i, b := range wideString {
+		byteArray[(i*2)+0] = byte(b >> 8)
+		byteArray[(i*2)+1] = byte(b >> 0)
+	}
+	return byteArray
+}
+
 func GetString(buf []byte) (string, error) {
 	nullTerminator := bytes.IndexByte(buf, 0)
 

gpcm/error.go

@@ -3,6 +3,7 @@ package gpcm
 import (
 	"fmt"
 	"strconv"
+	"unicode/utf16"
 	"wwfc/common"
 	"wwfc/logging"
 )
@@ -392,9 +393,11 @@ func (err GPError) GetMessageTranslate(gameName string, region byte, lang byte,
 			}
 
 			errMsg = fmt.Sprintf(errMsg, err.WWFCMessage.ErrorCode, ngid)
+			errMsgUTF16 := utf16.Encode([]rune(errMsg))
+			errMsgByteArray := common.UTF16ToByteArray(errMsgUTF16)
 
 			command.OtherValues["wwfc_err"] = strconv.Itoa(err.WWFCMessage.ErrorCode)
-			command.OtherValues["wwfc_errmsg"] = errMsg
+			command.OtherValues["wwfc_errmsg"] = common.Base64DwcEncoding.EncodeToString(errMsgByteArray)
 		}
 	}
 

gpcm/login.go

@@ -10,6 +10,7 @@ import (
 	"strconv"
 	"strings"
 	"time"
+	"unicode/utf16"
 	"wwfc/common"
 	"wwfc/database"
 	"wwfc/logging"
@@ -303,18 +304,28 @@ func (g *GameSpySession) login(command common.GameSpyCommand) {
 		replyUserId = 0
 	}
 
+	otherValues := map[string]string{
+		"sesskey":    strconv.FormatInt(int64(g.SessionKey), 10),
+		"proof":      proof,
+		"userid":     strconv.FormatUint(replyUserId, 10),
+		"profileid":  strconv.FormatUint(uint64(g.User.ProfileId), 10),
+		"uniquenick": g.User.UniqueNick,
+		"lt":         g.LoginTicket,
+		"id":         command.OtherValues["id"],
+	}
+
+	if g.GameName == "mariokartwii" {
+		if motd, err := GetMessageOfTheDay(); err == nil {
+			motdUTF16 := utf16.Encode([]rune(motd))
+			motdByteArray := common.UTF16ToByteArray(motdUTF16)
+			otherValues["wwfc_motd"] = common.Base64DwcEncoding.EncodeToString(motdByteArray)
+		}
+	}
+
 	payload := common.CreateGameSpyMessage(common.GameSpyCommand{
 		Command:      "lc",
 		CommandValue: "2",
-		OtherValues: map[string]string{
-			"sesskey":    strconv.FormatInt(int64(g.SessionKey), 10),
-			"proof":      proof,
-			"userid":     strconv.FormatUint(replyUserId, 10),
-			"profileid":  strconv.FormatUint(uint64(g.User.ProfileId), 10),
-			"uniquenick": g.User.UniqueNick,
-			"lt":         g.LoginTicket,
-			"id":         command.OtherValues["id"],
-		},
+		OtherValues:  otherValues,
 	})
 
 	g.Conn.Write([]byte(payload))

gpcm/motd.go

@@ -0,0 +1,20 @@
+package gpcm
+
+import (
+	"os"
+	"strings"
+)
+
+var motdFilepath = "./motd.txt"
+
+func GetMessageOfTheDay() (string, error) {
+	contents, err := os.ReadFile(motdFilepath)
+	if err != nil {
+		return "", err
+	}
+
+	strContents := string(contents)
+	strContents = strings.TrimSpace(strContents)
+
+	return strContents, nil
+}

motd.txt

@@ -0,0 +1,2 @@
+Welcome to
+WiiLink Wi-Fi Connection!