Incognito_RCM/source/storage/nx_emmc_bis.c

/*
 * eMMC BIS driver for Nintendo Switch
 *
 * Copyright (c) 2019 shchmue
 * Copyright (c) 2019-2020 CTCaer
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms and conditions of the GNU General Public License,
 * version 2, as published by the Free Software Foundation.
 *
 * This program is distributed in the hope it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
 * more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#include <string.h>

#include <memory_map.h>

#include <sec/se.h>
#include "../storage/nx_emmc.h"
#include <storage/sdmmc.h>
#include <utils/types.h>

#define MAX_CLUSTER_CACHE_ENTRIES 128
#define CLUSTER_LOOKUP_EMPTY_ENTRY 0xFFFFFFFF
#define XTS_CLUSTER_SIZE 0x4000
#define SECTORS_PER_CLUSTER 0x20

typedef struct
{
	u32 cluster_num;                // index of the cluster in the partition
	u32 visit_count;                // used for debugging/access analysis
	u8  dirty;                      // has been modified without writeback flag
	u8  align[7];
	u8  cluster[XTS_CLUSTER_SIZE];  // the cached cluster itself
} cluster_cache_t;

static u8 ks_crypt = 0;
static u8 ks_tweak = 0;
static u32 cluster_cache_end_index = 0;
static emmc_part_t *system_part = NULL;
static u8 *emmc_buffer = (u8 *)NX_BIS_CACHE_ADDR;
static cluster_cache_t *cluster_cache = (cluster_cache_t *)(NX_BIS_CACHE_ADDR + XTS_CLUSTER_SIZE);
static u32 *cluster_lookup = (u32 *)(NX_BIS_CACHE_ADDR + XTS_CLUSTER_SIZE + MAX_CLUSTER_CACHE_ENTRIES * sizeof(cluster_cache_t));
static bool lock_cluster_cache = false;

static void _gf256_mul_x_le(void *block)
{
	u32 *pdata = (u32 *)block;
	u32 carry = 0;

	for (u32 i = 0; i < 4; i++) {
		u32 b = pdata[i];
		pdata[i] = (b << 1) | carry;
		carry = b >> 31;
	}

	if (carry)
		pdata[0x0] ^= 0x87;
}

static int _nx_aes_xts_crypt_sec(u32 tweak_ks, u32 crypt_ks, u32 enc, u8 *tweak, bool regen_tweak, u32 tweak_exp, u32 sec, void *dst, const void *src, u32 sec_size)
{
	u32 *pdst = (u32 *)dst;
	u32 *psrc = (u32 *)src;
	u32 *ptweak = (u32 *)tweak;

	if (regen_tweak)
	{
		for (int i = 0xF; i >= 0; i--)
		{
			tweak[i] = sec & 0xFF;
			sec >>= 8;
		}
		if (!se_aes_crypt_block_ecb(tweak_ks, 1, tweak, tweak))
			return 0;
	}

	// tweak_exp allows us to use a saved tweak to reduce _gf256_mul_x_le calls.
	for (u32 i = 0; i < (tweak_exp << 5); i++)
		_gf256_mul_x_le(tweak);

	u8 orig_tweak[0x10];
	memcpy(orig_tweak, tweak, 0x10);

	// We are assuming a 0x10-aligned sector size in this implementation.
	for (u32 i = 0; i < (sec_size >> 4); i++)
	{
		for (u32 j = 0; j < 4; j++)
			pdst[j] = psrc[j] ^ ptweak[j];

		_gf256_mul_x_le(tweak);
		psrc += 4;
		pdst += 4;
	}

	if (!se_aes_crypt_ecb(crypt_ks, enc, dst, sec_size, dst, sec_size))
		return 0;

	pdst = (u32 *)dst;
	ptweak = (u32 *)orig_tweak;
	for (u32 i = 0; i < (sec_size >> 4); i++)
	{
		for (u32 j = 0; j < 4; j++)
			pdst[j] = pdst[j] ^ ptweak[j];

		_gf256_mul_x_le(orig_tweak);
		pdst += 4;
	}

	return 1;
}

static int nx_emmc_bis_read_block(u32 sector, u32 count, void *buff)
{
	if (!system_part)
		return 3; // Not ready.

	static u32 prev_cluster = -1;
	static u32 prev_sector = 0;
	static u8 tweak[0x10];

	u32 tweak_exp = 0;
	bool regen_tweak = true;

	u32 cluster = sector / SECTORS_PER_CLUSTER;
	u32 aligned_sector = cluster * SECTORS_PER_CLUSTER;
	u32 sector_index_in_cluster = sector % SECTORS_PER_CLUSTER;
	u32 cluster_lookup_index = cluster_lookup[cluster];

	if (cluster_lookup_index != CLUSTER_LOOKUP_EMPTY_ENTRY)
	{
		memcpy(buff, cluster_cache[cluster_lookup_index].cluster + sector_index_in_cluster * NX_EMMC_BLOCKSIZE, count * NX_EMMC_BLOCKSIZE);
		cluster_cache[cluster_lookup_index].visit_count++;
		prev_sector = sector + count - 1;
		prev_cluster = cluster;
		return 0; // Success.
	}

	// Only cache single-sector reads as these are most likely to be repeated, such as boot block and FAT directory tables.
	if (count == 1 &&
		!lock_cluster_cache &&
		cluster_cache_end_index < MAX_CLUSTER_CACHE_ENTRIES &&
		cluster_lookup_index == CLUSTER_LOOKUP_EMPTY_ENTRY)
	{
		cluster_cache[cluster_cache_end_index].cluster_num = cluster;
		cluster_cache[cluster_cache_end_index].visit_count = 1;
		cluster_cache[cluster_cache_end_index].dirty = 0;
		cluster_lookup[cluster] = cluster_cache_end_index;

		// Read and decrypt the whole cluster the sector resides in.
		if (!nx_emmc_part_read(&emmc_storage, system_part, aligned_sector, SECTORS_PER_CLUSTER, emmc_buffer))
			return 1; // R/W error.
		if (!_nx_aes_xts_crypt_sec(ks_tweak, ks_crypt, 0, tweak, true, 0, cluster, emmc_buffer, emmc_buffer, XTS_CLUSTER_SIZE))
			return 1; // R/W error.

		// Copy to cluster cache.
		memcpy(cluster_cache[cluster_cache_end_index].cluster, emmc_buffer, XTS_CLUSTER_SIZE);
		memcpy(buff, emmc_buffer + sector_index_in_cluster * NX_EMMC_BLOCKSIZE, NX_EMMC_BLOCKSIZE);
		prev_cluster = -1;
		prev_sector = 0;
		cluster_cache_end_index++;
		return 0; // Success.
	}

	// If not reading from or writing to cache, do a regular read and decrypt.
	if (!nx_emmc_part_read(&emmc_storage, system_part, sector, count, buff))
		return 1; // R/W error.

	if (prev_cluster != cluster) // Sector in different cluster than last read.
	{
		prev_cluster = cluster;
		tweak_exp = sector_index_in_cluster;
	}
	else if (sector > prev_sector) // Sector in same cluster and past last sector.
	{
		// Calculates the new tweak using the saved one, reducing expensive _gf256_mul_x_le calls.
		tweak_exp = sector - prev_sector - 1;
		regen_tweak = false;
	}
	else // Sector in same cluster and before or same as last sector.
		tweak_exp = sector_index_in_cluster;

	// Maximum one cluster (1 XTS crypto block 16KB).
	if (!_nx_aes_xts_crypt_sec(ks_tweak, ks_crypt, 0, tweak, regen_tweak, tweak_exp, prev_cluster, buff, buff, count * NX_EMMC_BLOCKSIZE))
		return 1; // R/W error.
	prev_sector = sector + count - 1;

	return 0; // Success.
}

int nx_emmc_bis_read(u32 sector, u32 count, void *buff)
{
	int res = 1;
	u8 *buf = (u8 *)buff;
	u32 curr_sct = sector;

	while (count)
	{
		u32 sct_cnt = MIN(count, 0x20);
		res = nx_emmc_bis_read_block(curr_sct, sct_cnt, buf);
		if (res)
			return 1;

		count -= sct_cnt;
		curr_sct += sct_cnt;
		buf += NX_EMMC_BLOCKSIZE * sct_cnt;
	}

	return res;
}

void nx_emmc_bis_cluster_cache_init() {
	// Clear cluster lookup table and reset end index.
	memset(cluster_lookup, -1, (system_part->lba_end - system_part->lba_start + 1) / SECTORS_PER_CLUSTER * sizeof(*cluster_lookup));
	cluster_cache_end_index = 0;
	lock_cluster_cache = false;
}

void nx_emmc_bis_init(emmc_part_t *part)
{
	system_part = part;

	nx_emmc_bis_cluster_cache_init();
	
	switch (part->index)
	{
	case 0:  // PRODINFO.
	case 1:  // PRODINFOF.
		ks_crypt = 0;
		ks_tweak = 1;
		break;
	case 8:  // SAFE.
		ks_crypt = 2;
		ks_tweak = 3;
		break;
	case 9:  // SYSTEM.
	case 10: // USER.
		ks_crypt = 4;
		ks_tweak = 5;
		break;
	}
}

// Set cluster cache lock according to arg.
void nx_emmc_bis_cache_lock(bool lock)
{
	lock_cluster_cache = lock;
}