Reduce security

Nintendo makes the unfortunate decision of sending the plaintext token to the client in a few requests.

Instead of storing a SHA-256 hash of the MD5 we expect from the Wii, we now store both the computed MD5 and plaintext generated token during registration.

The author of this commit apologizes.

database.sql

@@ -25,6 +25,21 @@ Follow and practice proper security practices before handling user data.
 /*!40101 SET @OLD_SQL_MODE=@@SQL_MODE, SQL_MODE='NO_AUTO_VALUE_ON_ZERO' */;
 /*!40111 SET @OLD_SQL_NOTES=@@SQL_NOTES, SQL_NOTES=0 */;
 
+--
+-- Table structure for table `shop_titles`
+--
+
+DROP TABLE IF EXISTS `shop_titles`;
+/*!40101 SET @saved_cs_client     = @@character_set_client */;
+/*!40101 SET character_set_client = utf8 */;
+CREATE TABLE `shop_titles` (
+                               `title_id` varchar(16) NOT NULL,
+                               `version` int(11) NOT NULL,
+                               `description` mediumtext DEFAULT 'yada yada',
+                               PRIMARY KEY (`title_id`)
+) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;
+/*!40101 SET character_set_client = @saved_cs_client */;
+
 --
 -- Table structure for table `owned_titles`
 --
@@ -43,21 +58,6 @@ CREATE TABLE `owned_titles` (
 ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;
 /*!40101 SET character_set_client = @saved_cs_client */;
 
---
--- Table structure for table `shop_titles`
---
-
-DROP TABLE IF EXISTS `shop_titles`;
-/*!40101 SET @saved_cs_client     = @@character_set_client */;
-/*!40101 SET character_set_client = utf8 */;
-CREATE TABLE `shop_titles` (
-                               `title_id` varchar(16) NOT NULL,
-                               `version` int(11) NOT NULL,
-                               `description` mediumtext DEFAULT 'yada yada',
-                               PRIMARY KEY (`title_id`)
-) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;
-/*!40101 SET character_set_client = @saved_cs_client */;
-
 --
 -- Table structure for table `userbase`
 --
@@ -67,7 +67,8 @@ DROP TABLE IF EXISTS `userbase`;
 /*!40101 SET character_set_client = utf8 */;
 CREATE TABLE `userbase` (
                             `DeviceId` varchar(10) NOT NULL,
-                            `DeviceToken` varchar(64) NOT NULL COMMENT 'This token should be considered a secret, so after generation only the sha256sum of the md5 the Wii sends is inserted.',
+                            `DeviceTokenUnhashed` varchar(21) NOT NULL COMMENT 'Sadly, sometimes we must return the device token in plaintext.',
+                            `DeviceToken` varchar(32) NOT NULL COMMENT 'The MD5 of the device token is sent for most requests. We store it to avoid wasting compute time.',
                             `AccountId` varchar(9) NOT NULL,
                             `Region` varchar(3) NOT NULL,
                             `Country` varchar(2) NOT NULL,

ias.go

@@ -19,7 +19,6 @@ package main
 
 import (
 	"crypto/md5"
-	"crypto/sha256"
 	"database/sql"
 	"errors"
 	"fmt"
@@ -34,7 +33,7 @@ var registerUser *sql.Stmt
 
 func iasInitialize() {
 	var err error
-	registerUser, err = db.Prepare(`INSERT INTO userbase (DeviceId, DeviceToken, AccountId, Region, Country, Language, SerialNo, DeviceCode)  VALUES (?, ?, ?, ?, ?, ?, ?, ?)`)
+	registerUser, err = db.Prepare(`INSERT INTO userbase (DeviceId, DeviceTokenUnhashed, DeviceToken, AccountId, Region, Country, Language, SerialNo, DeviceCode)  VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?)`)
 	if err != nil {
 		log.Fatalf("ias initialize: error preparing statement: %v\n", err)
 	}
@@ -120,19 +119,13 @@ func register(e *Envelope) {
 	// Generate a random 9-digit number, padding zeros as necessary.
 	accountId := fmt.Sprintf("%9d", rand.Intn(999999999))
 
-	// This is where it gets hairy.
 	// Generate a device token, 21 characters...
 	deviceToken := RandString(21)
-	// ...and then its md5, because the Wii sends this...
+	// ...and then its md5, because the Wii sends this for most requests.
 	md5DeviceToken := fmt.Sprintf("%x", md5.Sum([]byte(deviceToken)))
-	// ...and then the sha256 of that md5.
-	// We'll store this in our database, as storing the md5 itself is effectively the token.
-	// It would not be good for security to directly store the token either.
-	// This is the hash of the md5 represented as a string, not individual byte values.
-	doublyHashedDeviceToken := fmt.Sprintf("%x", sha256.Sum256([]byte(md5DeviceToken)))
 
 	// Insert all of our obtained values to the database..
-	_, err = registerUser.Exec(e.DeviceId(), doublyHashedDeviceToken, accountId, e.Region(), e.Country(), e.Language(), serialNo, deviceCode)
+	_, err = registerUser.Exec(e.DeviceId(), deviceToken, md5DeviceToken, accountId, e.Region(), e.Country(), e.Language(), serialNo, deviceCode)
 	if err != nil {
 		// It's okay if this isn't a MySQL error, as perhaps other issues have come in.
 		if driverErr, ok := err.(*mysql.MySQLError); ok {

route.go

@@ -1,7 +1,6 @@
 package main
 
 import (
-	"crypto/sha256"
 	"database/sql"
 	"fmt"
 	"io/ioutil"
@@ -172,11 +171,8 @@ func checkAuthentication(e *Envelope) (bool, error) {
 		return false, nil
 	}
 
-	// The Wii sends us a MD5 of its given token. We store a SHA-256 hash of that.
-	hashedDeviceToken := fmt.Sprintf("%x", sha256.Sum256([]byte(hash)))
-
 	// Check using various input given.
-	row := routeVerify.QueryRow(hashedDeviceToken, accountId, e.DeviceId())
+	row := routeVerify.QueryRow(hash, accountId, e.DeviceId())
 
 	var throwaway string
 	err = row.Scan(&throwaway)