From 72ae997d3db0d5262c1cbdee2efca8801daa69b8 Mon Sep 17 00:00:00 2001
From: ergo720 <csteven129@gmail.com>
Date: Sat, 31 Mar 2018 22:12:36 +0200
Subject: [PATCH] Calculate last missing checksum field in the eeprom

---
 src/Common/EmuEEPROM.cpp   | 46 ++++++++++++++++++++++++++++++--------
 src/Common/EmuEEPROM.h     |  2 ++
 src/CxbxKrnl/EmuKrnlEx.cpp |  4 ++++
 3 files changed, 43 insertions(+), 9 deletions(-)

diff --git a/src/Common/EmuEEPROM.cpp b/src/Common/EmuEEPROM.cpp
index 97a9e7371..810f2fc07 100644
--- a/src/Common/EmuEEPROM.cpp
+++ b/src/Common/EmuEEPROM.cpp
@@ -46,12 +46,18 @@ namespace xboxkrnl
 
 #include "Cxbx.h" // For DbgPrintf
 #include "EmuEEPROM.h" // For EEPROMInfo, EEPROMInfos
+#include "..\CxbxKrnl\Emu.h" // For EmuWarning
+#include "..\..\src\devices\LED.h" // For SetLEDSequence
+#include "..\CxbxKrnl\CxbxKrnl.h"
 
 xboxkrnl::XBOX_EEPROM *EEPROM = nullptr; // Set using CxbxRestoreEEPROM()
 
 // Default value (NA), overwritten with the actual content in the eeprom by CxbxRestoreEEPROM
 xboxkrnl::ULONG XboxFactoryGameRegion = XC_GAME_REGION_NA;
 
+// Default eeprom key (all zeros). Used to calculate the checksum of the eeprom header and to encrypt it if desired
+UCHAR EepromKey[20] = { 0 };
+
 const EEPROMInfo* EmuFindEEPROMInfo(xboxkrnl::XC_VALUE_INDEX index)
 {
 	for (int i = 0; EEPROMInfos[i].index != XC_END_MARKER; i++)
@@ -130,7 +136,9 @@ xboxkrnl::XBOX_EEPROM *CxbxRestoreEEPROM(char *szFilePath_EEPROM_bin)
 		}
 	}
 
-	// TODO : Make sure EEPROM.bin is at least 256 bytes in size - FileSeek(hFileEEPROM, EEPROM_SIZE, soFromBeginning);
+	// Make sure EEPROM.bin is at least 256 bytes in size
+	SetFilePointer(hFileEEPROM, 256, nullptr, FILE_BEGIN);
+	SetEndOfFile(hFileEEPROM);
 
 	HANDLE hFileMappingEEPROM = CreateFileMapping(
 		hFileEEPROM,
@@ -145,6 +153,15 @@ xboxkrnl::XBOX_EEPROM *CxbxRestoreEEPROM(char *szFilePath_EEPROM_bin)
 		return nullptr;
 	}
 
+	LARGE_INTEGER  len_li;
+	GetFileSizeEx(hFileEEPROM, &len_li);
+	unsigned int FileSize = len_li.u.LowPart;
+	if (FileSize != 256)
+	{
+		CxbxKrnlCleanup("CxbxRestoreEEPROM : EEPROM.bin file is not 256 bytes large!\n");
+		return nullptr;
+	}
+
 	// Map EEPROM.bin contents into memory :
 	pEEPROM = (xboxkrnl::XBOX_EEPROM *)MapViewOfFile(
 		hFileMappingEEPROM,
@@ -161,8 +178,6 @@ xboxkrnl::XBOX_EEPROM *CxbxRestoreEEPROM(char *szFilePath_EEPROM_bin)
     // so that users do not need to delete their EEPROM.bin from older versions
     gen_section_CRCs(pEEPROM);
 
-	// TODO : Verify checksums
-
 	// Check for (and fix) invalid fields that were set by previous versions of Cxbx-Reloaded
 	// Without this, all users would have to delete their EEPROM.bin
 	// The issue was that the AV_FLAG_XXhz was set in the wrong field, we fix it by
@@ -174,12 +189,6 @@ xboxkrnl::XBOX_EEPROM *CxbxRestoreEEPROM(char *szFilePath_EEPROM_bin)
 		pEEPROM->FactorySettings.AVRegion = AV_STANDARD_NTSC_M | AV_FLAGS_60Hz;
 	}
 
-	// Initialize XboxFactoryGameRegion from the value stored in the eeprom
-	/*const EEPROMInfo* info = EmuFindEEPROMInfo(xboxkrnl::XC_ENCRYPTED_SECTION);
-	if (info != nullptr) {
-		XboxFactoryGameRegion = (*((xboxkrnl::XBOX_ENCRYPTED_SETTINGS*)((PBYTE)pEEPROM + info->value_offset))).GameRegion;
-	}*/
-
 	if (NeedsInitialization)
 	{
 		memset(pEEPROM, 0, EEPROM_SIZE);
@@ -207,5 +216,24 @@ xboxkrnl::XBOX_EEPROM *CxbxRestoreEEPROM(char *szFilePath_EEPROM_bin)
 		DbgPrintf("INIT: Loaded EEPROM.bin\n");
 	}
 
+	// Update the existing Checksum if it is all zeros. Without this, all users would have to delete their EEPROM.bin
+	UCHAR Checksum[20] = { 0 };
+	if (!memcmp(Checksum, pEEPROM->EncryptedSettings.Checksum, 20))
+	{
+		xboxkrnl::XcHMAC(EepromKey, 16, pEEPROM->EncryptedSettings.Confounder, 8, pEEPROM->EncryptedSettings.HDKey, 20,
+			pEEPROM->EncryptedSettings.Checksum);
+	}
+	else
+	{
+		// Verify the checksum of the eeprom header
+		xboxkrnl::XcHMAC(EepromKey, 16, pEEPROM->EncryptedSettings.Confounder, 8, pEEPROM->EncryptedSettings.HDKey, 20, Checksum);
+		if (memcmp(Checksum, pEEPROM->EncryptedSettings.Checksum, 20))
+		{
+			// The checksums do not match. Log this error and flash the LED (red, off, red, off)
+			EmuWarning("Stored and calculated checksums don't match: eeprom corrupted");
+			SetLEDSequence(0xA0);
+		}
+	}
+
 	return pEEPROM;
 }
diff --git a/src/Common/EmuEEPROM.h b/src/Common/EmuEEPROM.h
index 2dc9a49c6..6cfc42342 100644
--- a/src/Common/EmuEEPROM.h
+++ b/src/Common/EmuEEPROM.h
@@ -102,6 +102,8 @@ extern xboxkrnl::ULONG XboxFactoryGameRegion;
 
 void gen_section_CRCs(xboxkrnl::XBOX_EEPROM*);
 
+extern UCHAR EepromKey[20];
+
 #if defined(__cplusplus)
 }
 #endif
diff --git a/src/CxbxKrnl/EmuKrnlEx.cpp b/src/CxbxKrnl/EmuKrnlEx.cpp
index 21eeebb21..1a14cc6ce 100644
--- a/src/CxbxKrnl/EmuKrnlEx.cpp
+++ b/src/CxbxKrnl/EmuKrnlEx.cpp
@@ -600,6 +600,10 @@ XBSYSAPI EXPORTNUM(29) xboxkrnl::NTSTATUS NTAPI xboxkrnl::ExSaveNonVolatileSetti
 	void * value_addr = nullptr;
 	DWORD result_length;
 
+	// Don't allow writing to the eeprom encrypted area
+	if (ValueIndex == XC_ENCRYPTED_SECTION)
+		RETURN(STATUS_OBJECT_NAME_NOT_FOUND);
+
 	// handle eeprom write
 	if (g_bIsDebug || ValueIndex <= XC_MAX_OS || ValueIndex > XC_MAX_FACTORY)
 	{