From 41a336888965b1ef535084839644a061dc10eafe Mon Sep 17 00:00:00 2001
From: Starsam80 <samraskauskas@gmail.com>
Date: Wed, 29 Dec 2021 21:03:50 -0700
Subject: [PATCH] NANDImporter: Only read the AES key once

There is no need to constantly reset the key for every file entry.
---
 Source/Core/DiscIO/NANDImporter.cpp | 14 ++++++--------
 Source/Core/DiscIO/NANDImporter.h   |  2 ++
 2 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/Source/Core/DiscIO/NANDImporter.cpp b/Source/Core/DiscIO/NANDImporter.cpp
index 67be289b4c..4520930ca3 100644
--- a/Source/Core/DiscIO/NANDImporter.cpp
+++ b/Source/Core/DiscIO/NANDImporter.cpp
@@ -4,7 +4,6 @@
 #include "DiscIO/NANDImporter.h"
 
 #include <algorithm>
-#include <array>
 #include <cstring>
 
 #include "Common/Crypto/AES.h"
@@ -35,8 +34,8 @@ void NANDImporter::ImportNANDBin(const std::string& path_to_bin,
   if (!FindSuperblock())
     return;
 
-  ProcessEntry(0, "");
   ExportKeys();
+  ProcessEntry(0, "");
   ExtractCertificates();
 }
 
@@ -165,13 +164,8 @@ void NANDImporter::ProcessEntry(u16 entry_number, const std::string& parent_path
 
 std::vector<u8> NANDImporter::GetEntryData(const NANDFSTEntry& entry)
 {
-  constexpr size_t NAND_AES_KEY_OFFSET = 0x158;
   constexpr size_t NAND_FAT_BLOCK_SIZE = 0x4000;
 
-  std::array<u8, 16> key{};
-  std::copy(&m_nand_keys[NAND_AES_KEY_OFFSET], &m_nand_keys[NAND_AES_KEY_OFFSET + key.size()],
-            key.begin());
-
   u16 sub = entry.sub;
   size_t remaining_bytes = entry.size;
   std::vector<u8> data{};
@@ -181,7 +175,7 @@ std::vector<u8> NANDImporter::GetEntryData(const NANDFSTEntry& entry)
   {
     std::array<u8, 16> iv{};
     std::vector<u8> block = Common::AES::Decrypt(
-        key.data(), iv.data(), &m_nand[NAND_FAT_BLOCK_SIZE * sub], NAND_FAT_BLOCK_SIZE);
+        m_aes_key.data(), iv.data(), &m_nand[NAND_FAT_BLOCK_SIZE * sub], NAND_FAT_BLOCK_SIZE);
 
     size_t size = std::min(remaining_bytes, block.size());
     data.insert(data.end(), block.begin(), block.begin() + size);
@@ -264,6 +258,10 @@ bool NANDImporter::ExtractCertificates()
 
 void NANDImporter::ExportKeys()
 {
+  constexpr size_t NAND_AES_KEY_OFFSET = 0x158;
+
+  std::copy_n(&m_nand_keys[NAND_AES_KEY_OFFSET], m_aes_key.size(), m_aes_key.begin());
+
   const std::string file_path = m_nand_root + "/keys.bin";
   File::IOFile file(file_path, "wb");
   if (!file.WriteBytes(m_nand_keys.data(), NAND_KEYS_SIZE))
diff --git a/Source/Core/DiscIO/NANDImporter.h b/Source/Core/DiscIO/NANDImporter.h
index b0956e8d00..269a6c5483 100644
--- a/Source/Core/DiscIO/NANDImporter.h
+++ b/Source/Core/DiscIO/NANDImporter.h
@@ -3,6 +3,7 @@
 
 #pragma once
 
+#include <array>
 #include <functional>
 #include <memory>
 #include <string>
@@ -73,6 +74,7 @@ private:
   std::string m_nand_root;
   std::vector<u8> m_nand;
   std::vector<u8> m_nand_keys;
+  std::array<u8, 16> m_aes_key;
   std::unique_ptr<NANDSuperblock> m_superblock;
   std::function<void()> m_update_callback;
 };