feat(grpc): add decrypted mii data to 3DS response

README.md

@@ -98,4 +98,5 @@ All configuration options are handled via environment variables
 | `PN_FRIENDS_CONFIG_ACCOUNT_GRPC_PORT`          | Port for your account server gRPC service                                                                              | Yes                                 |
 | `PN_FRIENDS_CONFIG_ACCOUNT_GRPC_API_KEY`       | API key for your account server gRPC service                                                                           | No (Assumed to be an open gRPC API) |
 | `PN_FRIENDS_CONFIG_HEALTH_CHECK_PORT`          | Port for the basic UDP health check server                                                                             | No                                  |
-| `PN_FRIENDS_CONFIG_ENABLE_BELLA`               | Enables a debug user named "Bella" which is always assigned as your friend                                             | No                                  | No                                  
+| `PN_FRIENDS_CONFIG_ENABLE_BELLA`               | Enables a debug user named "Bella" which is always assigned as your friend                                             | No                                  |
+| `PN_FRIENDS_CONFIG_MII_DECRYPT_KEY`            | AES key used to decrypt 3DS Mii data (as a hex string)                                                                 | Yes                                 |

globals/config.go

@@ -14,6 +14,7 @@ type config struct {
 	AccountGRPCAPIKey        string `envconf:"optional"`
 	HealthCheckPort          uint16 `envconf:"optional"`
 	EnableBella              bool   `envconf:"optional"`
+	MiiDecryptKey            string
 }
 
 var Config *config = &config{}

grpc/get_user_data.go

@@ -8,6 +8,7 @@ import (
 	database_3ds "github.com/PretendoNetwork/friends/database/3ds"
 	database_wiiu "github.com/PretendoNetwork/friends/database/wiiu"
 	"github.com/PretendoNetwork/friends/globals"
+	"github.com/PretendoNetwork/friends/utility"
 	pb "github.com/PretendoNetwork/grpc/go/friends/v2"
 	"github.com/PretendoNetwork/nex-go/v2/types"
 	"google.golang.org/grpc/codes"
@@ -106,7 +107,11 @@ func (s *gRPCFriendsV2Server) GetUserData3DS(ctx context.Context, in *pb.GetUser
 		ProfanityFlag:    bool(miiData.Mii.ProfanityFlag),
 		CharacterSet:     uint32(miiData.Mii.CharacterSet),
 		MiiDataEncrypted: miiData.Mii.MiiData,
-		// TODO: Implement MiiData
+	}
+
+	mii_data, err := utility.DecryptMiiData(miiData.Mii.MiiData)
+	if err == nil {
+		mii.MiiData = mii_data
 	}
 	friendMii := &pb.FriendMii{
 		Pid:        uint32(miiData.PID),

grpc/get_user_friends_data.go

@@ -12,6 +12,7 @@ import (
 	database_3ds "github.com/PretendoNetwork/friends/database/3ds"
 	database_wiiu "github.com/PretendoNetwork/friends/database/wiiu"
 	"github.com/PretendoNetwork/friends/globals"
+	"github.com/PretendoNetwork/friends/utility"
 	pb "github.com/PretendoNetwork/grpc/go/friends/v2"
 	"github.com/PretendoNetwork/nex-go/v2/types"
 	friends_3ds_types "github.com/PretendoNetwork/nex-protocols-go/v2/friends-3ds/types"
@@ -241,10 +242,15 @@ func (s *gRPCFriendsV2Server) GetUserFriendsData3DS(ctx context.Context, in *pb.
 
 		miiData := miiList[miiIndex]
 		mii := &pb.Mii{
-			Name:          string(miiData.Mii.Name),
-			ProfanityFlag: bool(miiData.Mii.ProfanityFlag),
-			CharacterSet:  uint32(miiData.Mii.CharacterSet),
-			MiiData:       miiData.Mii.MiiData,
+			Name:             string(miiData.Mii.Name),
+			ProfanityFlag:    bool(miiData.Mii.ProfanityFlag),
+			CharacterSet:     uint32(miiData.Mii.CharacterSet),
+			MiiDataEncrypted: miiData.Mii.MiiData,
+		}
+
+		mii_data, err := utility.DecryptMiiData(miiData.Mii.MiiData)
+		if err == nil {
+			mii.MiiData = mii_data
 		}
 
 		friendMii := &pb.FriendMii{

utility/decrypt_mii.go

@@ -0,0 +1,57 @@
+package utility
+
+import (
+	"crypto/aes"
+	"crypto/cipher"
+	"encoding/hex"
+	"fmt"
+
+	"github.com/PretendoNetwork/friends/globals"
+	"github.com/PretendoNetwork/nex-go/v2/types"
+)
+
+func ccmDecrypt(key, nonce, ciphertext []byte) ([]byte, error) {
+	block, err := aes.NewCipher(key)
+	if err != nil {
+		return nil, err
+	}
+
+	L := 15 - len(nonce)
+
+	counter := make([]byte, aes.BlockSize)
+	counter[0] = byte(L - 1)
+	copy(counter[1:1+len(nonce)], nonce)
+	stream := cipher.NewCTR(block, counter)
+
+	padded := make([]byte, aes.BlockSize+len(ciphertext))
+	copy(padded[aes.BlockSize:], ciphertext)
+
+	out := make([]byte, len(padded))
+	stream.XORKeyStream(out, padded)
+
+	return out[aes.BlockSize:], nil
+}
+
+func DecryptMiiData(mii_data types.Buffer) ([]byte, error) {
+	if len(mii_data) < 96 {
+		return nil, fmt.Errorf("Mii data length is incorrect: %d", len(mii_data))
+	}
+	nonce := mii_data[:8]
+	ciphertext := mii_data[8 : 8+0x58]
+
+	key, err := hex.DecodeString(globals.Config.MiiDecryptKey)
+	if err != nil {
+		return nil, err
+	}
+	content, err := ccmDecrypt(key, append(append([]byte{}, nonce...), 0, 0, 0, 0), ciphertext)
+	if err != nil {
+		return nil, err
+	}
+
+	result := make([]byte, 0, len(content)+len(nonce))
+	result = append(result, content[:12]...)
+	result = append(result, nonce...)
+	result = append(result, content[12:]...)
+
+	return result, nil
+}