Handle GBA VC save in virtual NAND drives

source/nand/agbsave.c

@@ -0,0 +1,48 @@
+#include "agbsave.h"
+#include "sha.h"
+#include "aes.h"
+
+u32 GetAgbSaveSize(u32 nand_src) {
+    AgbSave* agbsave = (AgbSave*) NAND_BUFFER;
+    if (ReadNandSectors((u8*) agbsave, SECTOR_AGBSAVE, 1, 0x07, nand_src) != 0)
+        return 0;
+    return agbsave->save_size; // it's recommended to also check the CMAC
+}
+
+u32 CheckAgbSaveCmac(u32 nand_src) {
+    u8 magic[] = { AGBSAVE_MAGIC };
+    
+    AgbSave* agbsave = (AgbSave*) NAND_BUFFER;
+    if ((ReadNandSectors((u8*) agbsave, SECTOR_AGBSAVE, 1, 0x07, nand_src) != 0) ||
+        (memcmp(agbsave->magic, magic, sizeof(magic)) != 0) ||
+        (ReadNandBytes(agbsave->savegame, (SECTOR_AGBSAVE+1) * 0x200, agbsave->save_size, 0x07, nand_src) != 0))
+        return 1;
+    
+    u8 cmac[16] __attribute__((aligned(32)));
+    u8 shasum[32];
+    sha_quick(shasum, ((u8*) agbsave) + 0x30, (0x200 - 0x30) + agbsave->save_size, SHA256_MODE);
+    use_aeskey(0x24);
+    aes_cmac(shasum, cmac, 2);
+    
+    return (memcmp(cmac, agbsave->cmac, 16) == 0) ? 0 : 1;
+}
+
+u32 FixAgbSaveCmac(u32 nand_dst) {
+    AgbSave* agbsave = (AgbSave*) NAND_BUFFER;
+    if ((ReadNandSectors((u8*) agbsave, SECTOR_AGBSAVE, 1, 0x07, nand_dst) != 0) ||
+        (ReadNandBytes(agbsave->savegame, (SECTOR_AGBSAVE+1) * 0x200, agbsave->save_size, 0x07, nand_dst) != 0))
+        return 1;
+        
+    u8 cmac[16] __attribute__((aligned(32)));
+    u8 shasum[32];
+    sha_quick(shasum, ((u8*) agbsave) + 0x30, (0x200 - 0x30) + agbsave->save_size, SHA256_MODE);
+    use_aeskey(0x24);
+    aes_cmac(shasum, cmac, 2);
+    memcpy(agbsave->cmac, cmac, 16);
+    
+    // set CFG_BOOTENV = 0x7 so the save is taken over
+    // https://www.3dbrew.org/wiki/CONFIG_Registers#CFG_BOOTENV
+    *(u32*) 0x10010000 = 0x7;
+    
+    return (WriteNandSectors((u8*) agbsave, SECTOR_AGBSAVE, 1, 0x07, nand_dst) != 0) ? 0 : 1;
+}

source/nand/agbsave.h

@@ -0,0 +1,29 @@
+#pragma once
+
+#include "common.h"
+#include "nand.h"
+
+#define AGBSAVE_MAGIC   '.', 'S', 'A', 'V'
+
+// see: http://3dbrew.org/wiki/3DS_Virtual_Console#NAND_Savegame
+typedef struct {
+	u8  magic[4]; // ".SAV"
+    u8  reserved0[0xC]; // always 0xFF
+    u8  cmac[0x10];
+    u8  reserved1[0x10]; // always 0xFF
+    u32 unknown0; // always 0x01
+    u32 times_saved;
+    u64 title_id;
+    u8  sd_cid[0x10];
+    u32 save_start; // always 0x200
+    u32 save_size;
+    u8  reserved2[0x8]; // always 0xFF
+    u32 unknown1; // has to do with ARM7?
+    u32 unknown2; // has to do with ARM7?
+    u8  reserved3[0x198]; // always 0xFF
+    u8  savegame[(SIZE_AGBSAVE-1)*0x200];
+} __attribute__((packed)) AgbSave;
+
+u32 GetAgbSaveSize(u32 nand_src);
+u32 CheckAgbSaveCmac(u32 nand_src);
+u32 FixAgbSaveCmac(u32 nand_dst);

source/nand/nand.c

@@ -11,12 +11,16 @@
 #define NAND_MIN_SECTORS ((GetUnitPlatform() == PLATFORM_N3DS) ? NAND_MIN_SECTORS_N3DS : NAND_MIN_SECTORS_O3DS)
 
 static u8 slot0x05KeyY[0x10] = { 0x00 }; // need to load this from FIRM0 / external file
-static u8 slot0x05KeyY_sha256[0x20] = { // hash for slot0x05KeyY (16 byte)
+static const u8 slot0x05KeyY_sha256[0x20] = { // hash for slot0x05KeyY (16 byte)
     0x98, 0x24, 0x27, 0x14, 0x22, 0xB0, 0x6B, 0xF2, 0x10, 0x96, 0x9C, 0x36, 0x42, 0x53, 0x7C, 0x86,
     0x62, 0x22, 0x5C, 0xFD, 0x6F, 0xAE, 0x9B, 0x0A, 0x85, 0xA5, 0xCE, 0x21, 0xAA, 0xB6, 0xC8, 0x4D
 };
+static const u8 slot0x24KeyY_sha256[0x20] = { // hash for slot0x24KeyY (16 byte) 
+    0x5F, 0x04, 0x01, 0x22, 0x95, 0xB2, 0x23, 0x70, 0x12, 0x40, 0x53, 0x30, 0xC0, 0xA7, 0xBF, 0x7C, 
+    0xD4, 0x40, 0x92, 0x25, 0xD1, 0x9D, 0xA2, 0xDE, 0xCD, 0xC7, 0x12, 0x97, 0x08, 0x46, 0x54, 0xB7
+};
     
-static u8 nand_magic_n3ds[0x60] = { // NCSD NAND header N3DS magic
+static const u8 nand_magic_n3ds[0x60] = { // NCSD NAND header N3DS magic
     0x4E, 0x43, 0x53, 0x44, 0x00, 0x00, 0x28, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
     0x01, 0x04, 0x03, 0x03, 0x01, 0x00, 0x00, 0x00, 0x01, 0x02, 0x02, 0x02, 0x03, 0x00, 0x00, 0x00,
     0x00, 0x00, 0x00, 0x00, 0x00, 0x88, 0x05, 0x00, 0x00, 0x88, 0x05, 0x00, 0x80, 0x01, 0x00, 0x00,
@@ -25,7 +29,7 @@ static u8 nand_magic_n3ds[0x60] = { // NCSD NAND header N3DS magic
     0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
 };
 
-static u8 nand_magic_o3ds[0x60] = { // NCSD NAND header O3DS magic
+static const u8 nand_magic_o3ds[0x60] = { // NCSD NAND header O3DS magic
     0x4E, 0x43, 0x53, 0x44, 0x00, 0x00, 0x20, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
     0x01, 0x04, 0x03, 0x03, 0x01, 0x00, 0x00, 0x00, 0x01, 0x02, 0x02, 0x02, 0x02, 0x00, 0x00, 0x00,
     0x00, 0x00, 0x00, 0x00, 0x00, 0x88, 0x05, 0x00, 0x00, 0x88, 0x05, 0x00, 0x80, 0x01, 0x00, 0x00,
@@ -34,7 +38,7 @@ static u8 nand_magic_o3ds[0x60] = { // NCSD NAND header O3DS magic
     0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
 };
 
-static u8 twl_mbr[0x42] = { // encrypted version inside the NCSD NAND header (@0x1BE)
+static const u8 twl_mbr[0x42] = { // encrypted version inside the NCSD NAND header (@0x1BE)
     0x00, 0x04, 0x18, 0x00, 0x06, 0x01, 0xA0, 0x3F, 0x97, 0x00, 0x00, 0x00, 0xA9, 0x7D, 0x04, 0x00,
     0x00, 0x04, 0x8E, 0x40, 0x06, 0x01, 0xA0, 0xC3, 0x8D, 0x80, 0x04, 0x00, 0xB3, 0x05, 0x01, 0x00,
     0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
@@ -48,13 +52,50 @@ static u8 OtpSha256[32] = { 0 };
 
 static u32 emunand_base_sector = 0x000000;
 
+
+u32 LoadKeyYFromP9(u8* key, const u8* keyhash, u32 offset, u32 keyslot)
+{
+    static u32 offsetA9l = 0x066A00; // fixed offset, this only has to work for FIRM90 / FIRM81
+    u8 ctr0x15[16] __attribute__((aligned(32)));
+    u8 keyY0x15[16] __attribute__((aligned(32)));
+    u8 keyY[16] __attribute__((aligned(32)));
+    u8 header[0x200];
+    
+    // check arm9loaderhax
+    if (!CheckA9lh() || (offset < (offsetA9l + 0x0800))) return 1;
+    
+    // section 2 (arm9loader) header of FIRM
+    // this is @0x066A00 in FIRM90 & FIRM81
+    ReadNandBytes(header, (SECTOR_FIRM0 * 0x200) + offsetA9l, 0x200, 0x06, NAND_SYSNAND);
+    memcpy(keyY0x15, header + 0x10, 0x10); // 0x15 keyY
+    memcpy(ctr0x15, header + 0x20, 0x10); // 0x15 counter
+    
+    // read and decrypt the encrypted keyY
+    ReadNandBytes(keyY, (SECTOR_FIRM0 * 0x200) + offset, 0x10, 0x06, NAND_SYSNAND);
+    setup_aeskeyY(0x15, keyY0x15);
+    use_aeskey(0x15);
+    ctr_decrypt_byte(keyY, keyY, 0x10, offset - (offsetA9l + 0x800), AES_CNT_CTRNAND_MODE, ctr0x15);
+    if (key) memcpy(key, keyY, 0x10);
+    
+    // check the key
+    u8 shasum[0x32];
+    sha_quick(shasum, keyY, 16, SHA256_MODE);
+    if (memcmp(shasum, keyhash, 32) == 0) {
+        setup_aeskeyY(keyslot, keyY);
+        use_aeskey(keyslot);
+        return 0;
+    }
+    
+    return 1;
+}
+
 bool InitNandCrypto(void)
 {   
     // part #0: KeyX / KeyY for secret sector 0x96
     // on a9lh this MUST be run before accessing the SHA register in any other way
     if (CheckA9lh()) { // for a9lh
         // store the current SHA256 from register
-        memcpy(OtpSha256, (void*)REG_SHAHASH, 32);
+        memcpy(OtpSha256, (void*) REG_SHAHASH, 32);
     } else {
         const char* base[] = { INPUT_PATHS };
         char path[64];
@@ -105,55 +146,21 @@ bool InitNandCrypto(void)
         use_aeskey(0x03);
     }
     
-    // part #3: CTRNAND N3DS KEY
+    // part #3: CTRNAND N3DS KEY / AGBSAVE CMAC KEY
     // thanks AuroraWright and Gelex for advice on this
     // see: https://github.com/AuroraWright/Luma3DS/blob/master/source/crypto.c#L347
-    if (CheckA9lh()) { // only for a9lh
+    
-        u8 ctr[16] __attribute__((aligned(32)));
+    // keyY 0x05 is encrypted @0x0EB014 in the FIRM90
-        u8 keyY[16] __attribute__((aligned(32)));
+    // keyY 0x05 is encrypted @0x0EB24C in the FIRM81
-        u8 header[0x200];
+    if ((LoadKeyYFromP9(slot0x05KeyY, slot0x05KeyY_sha256, 0x0EB014, 0x05) != 0) &&
-        
+        (LoadKeyYFromP9(slot0x05KeyY, slot0x05KeyY_sha256, 0x0EB24C, 0x05) != 0))
-        // section 2 header of FIRM0
+        LoadKeyFromFile(slot0x05KeyY, 0x05, 'Y', NULL);
-        // this is @0x066A00 in FIRM90 & FIRM81
+    
-        static u32 offsetSection2 = 0x066A00;
+    // keyY 0x24 is encrypted @0x0E62DC in the FIRM90
-        ReadNandSectors(header, 0x58980 + (offsetSection2 / 0x200), 1, 0x06, NAND_SYSNAND);
+    // keyY 0x24 is encrypted @0x0E6514 in the FIRM81
-        memcpy(keyY, header + 0x10, 0x10); // 0x15 keyY
+    if ((LoadKeyYFromP9(NULL, slot0x24KeyY_sha256, 0x0E62DC, 0x24) != 0) &&
-        
+        (LoadKeyYFromP9(NULL, slot0x24KeyY_sha256, 0x0E6514, 0x24) != 0))
-        // try FIRM90 & FIRM81 offsets, search for the key
+        LoadKeyFromFile(NULL, 0x24, 'Y', NULL);
-        for (u32 fver = 0; fver < 2; fver++) {
-            static u32 offset0x05KeyY[2] = { 0x0EB014, 0x0EB24C };
-            u32 offset = offset0x05KeyY[fver];
-            u8 sector[0x200];
-        
-            // sector containing the slot0x05 keyY
-            // key is encrypted @0x0EB014 in the FIRM90
-            // key is encrypted @0x0EB24C in the FIRM81
-            ReadNandSectors(sector, 0x58980 + (offset / 0x200), 1, 0x06, NAND_SYSNAND);
-            
-            // decrypt the sector, get the key
-            memcpy(ctr, header + 0x20, 0x10); // 0x15 counter
-            add_ctr(ctr, (offset - (offset % 0x200) - (offsetSection2 + 0x800)) / 16);
-            for (u32 i = 0x0; i < 0x200; i += 0x10) {
-                setup_aeskeyY(0x15, keyY);
-                use_aeskey(0x15);
-                set_ctr(ctr);
-                aes_decrypt(sector + i, sector + i, 1, AES_CNT_CTRNAND_MODE);
-                add_ctr(ctr, 0x1);
-            }
-            memcpy(slot0x05KeyY, sector + (offset % 0x200), 16);
-            
-            // check the key
-            sha_quick(shasum, slot0x05KeyY, 16, SHA256_MODE);
-            if (memcmp(shasum, slot0x05KeyY_sha256, 32) == 0) {
-                setup_aeskeyY(0x05, slot0x05KeyY);
-                use_aeskey(0x05);
-                break;
-            }
-        }
-        
-        if ((memcmp(shasum, slot0x05KeyY_sha256, 32) != 0) && // last resort
-            (LoadKeyFromFile(slot0x05KeyY, 0x05, 'Y', NULL) != 0)) {};
-    }
     
     return true;
 }
@@ -191,13 +198,13 @@ bool CheckA9lh(void)
 
 void CryptNand(u8* buffer, u32 sector, u32 count, u32 keyslot)
 {
-    u32 mode = (sector >= (0x0B100000 / 0x200)) ? AES_CNT_CTRNAND_MODE : AES_CNT_TWLNAND_MODE;
+    u32 mode = (sector >= SECTOR_TWL + SIZE_TWL) ? AES_CNT_CTRNAND_MODE : AES_CNT_TWLNAND_MODE;
     u8 ctr[16] __attribute__((aligned(32)));
     u32 blocks = count * (0x200 / 0x10);
     
     // copy NAND CTR and increment it
-    memcpy(ctr, (sector >= (0x0B100000 / 0x200)) ? CtrNandCtr : TwlNandCtr, 16);
+    memcpy(ctr, (sector >= SECTOR_TWL + SIZE_TWL) ? CtrNandCtr : TwlNandCtr, 16);
-    add_ctr(ctr, sector * (0x200/0x10));
+    add_ctr(ctr, sector * (0x200 / 0x10));
     
     // decrypt the data
     use_aeskey(keyslot);
@@ -214,8 +221,7 @@ void CryptSector0x96(u8* buffer, bool encrypt)
     
     // decrypt the sector
     use_aeskey(0x11);
-    for (u32 b = 0x0; b < 0x200; b += 0x10, buffer += 0x10)
+    ecb_decrypt((void*) buffer, (void*) buffer, 0x200 / AES_BLOCK_SIZE, mode);
-        aes_decrypt((void*) buffer, (void*) buffer, 1, mode);
 }
 
 int ReadNandBytes(u8* buffer, u32 offset, u32 count, u32 keyslot, u32 nand_src)

source/nand/nand.h

@@ -10,9 +10,30 @@
 #define NAND_TYPE_N3DS  (1<<5)
 #define NAND_TYPE_NO3DS (1<<6)
 
+// minimum size of NAND memory
 #define NAND_MIN_SECTORS_O3DS 0x1D7800
 #define NAND_MIN_SECTORS_N3DS 0x26C000
 
+// start sectors of partitions
+#define SECTOR_TWL      0x000000
+#define SECTOR_SECRET   0x000096
+#define SECTOR_TWLN     0x000097
+#define SECTOR_TWLP     0x04808D
+#define SECTOR_AGBSAVE  0x058800
+#define SECTOR_FIRM0    0x058980
+#define SECTOR_FIRM1    0x05A980
+#define SECTOR_CTR      0x05C980
+
+// sizes of partitions (in sectors)
+#define SIZE_TWL        0x058800
+#define SIZE_TWLN       0x047DA9
+#define SIZE_TWLP       0x0105B3
+#define SIZE_AGBSAVE    0x000180
+#define SIZE_FIRM0      0x002000
+#define SIZE_FIRM1      0x002000
+#define SIZE_CTR_O3DS   0x17AE80
+#define SIZE_CTR_N3DS   0x20F680
+
 bool InitNandCrypto(void);
 bool CheckSlot0x05Crypto(void);
 bool CheckSector0x96Crypto(void);

source/nand/nandutil.c

@@ -20,8 +20,8 @@ u32 ReadNandFile(FIL* file, void* buffer, u32 sector, u32 count, u32 keyslot) {
 }
 
 u32 ValidateNandDump(const char* path) {
-    const u32 mbr_sectors[] = { TWL_OFFSET, CTR_OFFSET };
+    const u32 mbr_sectors[] = { SECTOR_TWL, SECTOR_CTR };
-    const u32 firm_sectors[] = { FIRM_OFFSETS };
+    const u32 firm_sectors[] = { SECTOR_FIRM0, SECTOR_FIRM1 };
     u8 buffer[0x200];
     FirmHeader firm;
     MbrHeader mbr;

source/nand/nandutil.h

@@ -2,11 +2,8 @@
 
 #include "common.h"
 
-#define TWL_OFFSET      0x000000
+#define SAFE_SECTORS    0x000000 + 0x1, SECTOR_SECRET, SECTOR_SECRET + 0x1, \
-#define CTR_OFFSET      0x05C980
+                        SECTOR_FIRM0, SECTOR_CTR, 0x000000 // last one is a placeholder
-#define FIRM_OFFSETS    0x058980, 0x05A980
-
-#define SAFE_SECTORS    0x000001, 0x000096, 0x000097, 0x058980, 0x05C980, 0x000000 // last one is a placeholder
 
 u32 ValidateNandDump(const char* path);
 u32 SafeRestoreNandDump(const char* path);

source/virtual/vnand.c

@@ -1,15 +1,18 @@
 #include "vnand.h"
 #include "nand.h"
+#include "agbsave.h"
 #include "platform.h"
 
 #define VFLAG_ON_O3DS       NAND_TYPE_O3DS
 #define VFLAG_ON_N3DS       NAND_TYPE_N3DS
 #define VFLAG_ON_NO3DS      NAND_TYPE_NO3DS
 #define VFLAG_ON_NAND       (VFLAG_ON_O3DS | VFLAG_ON_N3DS | VFLAG_ON_NO3DS)
+#define VFLAG_GBA_VC        (1<<29)
 #define VFLAG_NEEDS_OTP     (1<<30)
 #define VFLAG_NAND_SIZE     (1<<31)
 
 // see: http://3dbrew.org/wiki/Flash_Filesystem#NAND_structure
+// too much hardcoding, but more readable this way
 static const VirtualFile vNandFileTemplates[] = {
     { "twln.bin"         , 0x00012E00, 0x08FB5200, 0x03, VFLAG_ON_NAND },
     { "twlp.bin"         , 0x09011A00, 0x020B6600, 0x03, VFLAG_ON_NAND },
@@ -28,7 +31,8 @@ static const VirtualFile vNandFileTemplates[] = {
     { "nand_minsize.bin" , 0x00000000, 0x4D800000, 0xFF, VFLAG_ON_N3DS | VFLAG_ON_NO3DS | VFLAG_A9LH_AREA },
     { "nand_hdr.bin"     , 0x00000000, 0x00000200, 0xFF, VFLAG_ON_NAND | VFLAG_A9LH_AREA },
     { "twlmbr.bin"       , 0x000001BE, 0x00000042, 0x03, VFLAG_ON_NAND | VFLAG_A9LH_AREA },
-    { "unused.bin"       , 0x00000200, 0x00012A00, 0xFF, VFLAG_ON_NAND }
+    { "unused.bin"       , 0x00000200, 0x00012A00, 0xFF, VFLAG_ON_NAND },
+    { "gbavc.sav"        , 0x0B100200, 0x00000000, 0x07, VFLAG_ON_NAND | VFLAG_GBA_VC },
 };
 
 bool CheckVNandDrive(u32 nand_src) {
@@ -51,7 +55,8 @@ bool ReadVNandDir(VirtualFile* vfile, VirtualDir* vdir) { // uses a generic vdir
         // XORpad drive handling
         if (nand_src == VRT_XORPAD) {
             snprintf(vfile->name, 32, "%s.xorpad", templates[vdir->index].name);
-            if ((vfile->keyslot == 0x11) || (vfile->keyslot >= 0x40)) continue;
+            if ((vfile->keyslot == 0x11) || (vfile->keyslot >= 0x40) || (vfile->flags & VFLAG_GBA_VC))
+                continue;
         }
         
         // process / check special flags
@@ -68,6 +73,10 @@ bool ReadVNandDir(VirtualFile* vfile, VirtualDir* vdir) { // uses a generic vdir
                 continue; // EmuNAND/ImgNAND is too small
             vfile->size = GetNandSizeSectors(NAND_SYSNAND) * 0x200;
         }
+        if (vfile->flags & VFLAG_GBA_VC) {
+            if (CheckAgbSaveCmac(nand_src) != 0) continue;
+            vfile->size = GetAgbSaveSize(nand_src);
+        }
         
         // found if arriving here
         vfile->flags |= nand_src;
@@ -84,5 +93,7 @@ int ReadVNandFile(const VirtualFile* vfile, u8* buffer, u32 offset, u32 count) {
 
 int WriteVNandFile(const VirtualFile* vfile, const u8* buffer, u32 offset, u32 count) {
     u32 nand_dst = vfile->flags & (VRT_SYSNAND|VRT_EMUNAND|VRT_IMGNAND|VRT_XORPAD);
-    return WriteNandBytes(buffer, vfile->offset + offset, count, vfile->keyslot, nand_dst);
+    int res = WriteNandBytes(buffer, vfile->offset + offset, count, vfile->keyslot, nand_dst);
+    if ((res == 0) && (vfile->flags & VFLAG_GBA_VC)) res = FixAgbSaveCmac(nand_dst);
+    return res;
 }