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OVMS3-idf/components/bootloader_support/src/flash_encrypt.c

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// Copyright 2015-2016 Espressif Systems (Shanghai) PTE LTD
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
#include <strings.h>
#include "bootloader_flash.h"
#include "esp_image_format.h"
#include "esp_flash_encrypt.h"
#include "esp_flash_partitions.h"
#include "esp_flash_data_types.h"
#include "esp_secure_boot.h"
#include "esp_efuse.h"
#include "esp_log.h"
#include "rom/secure_boot.h"
#include "soc/rtc_wdt.h"
#include "rom/cache.h"
#include "rom/spi_flash.h" /* TODO: Remove this */
static const char *TAG = "flash_encrypt";
/* Static functions for stages of flash encryption */
static esp_err_t initialise_flash_encryption(void);
static esp_err_t encrypt_flash_contents(uint32_t flash_crypt_cnt, bool flash_crypt_wr_dis);
static esp_err_t encrypt_bootloader();
static esp_err_t encrypt_and_load_partition_table(esp_partition_info_t *partition_table, int *num_partitions);
static esp_err_t encrypt_partition(int index, const esp_partition_info_t *partition);
esp_err_t esp_flash_encrypt_check_and_update(void)
{
uint32_t efuse_blk0 = REG_READ(EFUSE_BLK0_RDATA0_REG);
ESP_LOGV(TAG, "efuse_blk0 raw value %08x", efuse_blk0);
uint32_t flash_crypt_cnt = (efuse_blk0 & EFUSE_RD_FLASH_CRYPT_CNT_M) >> EFUSE_RD_FLASH_CRYPT_CNT_S;
bool flash_crypt_wr_dis = efuse_blk0 & EFUSE_WR_DIS_FLASH_CRYPT_CNT;
ESP_LOGV(TAG, "efuse FLASH_CRYPT_CNT 0x%x WR_DIS_FLASH_CRYPT_CNT 0x%x", flash_crypt_cnt, flash_crypt_wr_dis);
if (__builtin_parity(flash_crypt_cnt) == 1) {
/* Flash is already encrypted */
int left = (7 - __builtin_popcount(flash_crypt_cnt)) / 2;
if (flash_crypt_wr_dis) {
left = 0; /* can't update FLASH_CRYPT_CNT, no more flashes */
}
ESP_LOGI(TAG, "flash encryption is enabled (%d plaintext flashes left)", left);
return ESP_OK;
}
else {
/* Flash is not encrypted, so encrypt it! */
return encrypt_flash_contents(flash_crypt_cnt, flash_crypt_wr_dis);
}
}
static esp_err_t initialise_flash_encryption(void)
{
uint32_t coding_scheme = REG_GET_FIELD(EFUSE_BLK0_RDATA6_REG, EFUSE_CODING_SCHEME);
if (coding_scheme != EFUSE_CODING_SCHEME_VAL_NONE && coding_scheme != EFUSE_CODING_SCHEME_VAL_34) {
ESP_LOGE(TAG, "Unknown/unsupported CODING_SCHEME value 0x%x", coding_scheme);
return ESP_ERR_NOT_SUPPORTED;
}
/* Before first flash encryption pass, need to initialise key & crypto config */
/* Generate key */
uint32_t dis_reg = REG_READ(EFUSE_BLK0_RDATA0_REG);
bool efuse_key_read_protected = dis_reg & EFUSE_RD_DIS_BLK1;
bool efuse_key_write_protected = dis_reg & EFUSE_WR_DIS_BLK1;
if (efuse_key_read_protected == false
&& efuse_key_write_protected == false
&& REG_READ(EFUSE_BLK1_RDATA0_REG) == 0
&& REG_READ(EFUSE_BLK1_RDATA1_REG) == 0
&& REG_READ(EFUSE_BLK1_RDATA2_REG) == 0
&& REG_READ(EFUSE_BLK1_RDATA3_REG) == 0
&& REG_READ(EFUSE_BLK1_RDATA4_REG) == 0
&& REG_READ(EFUSE_BLK1_RDATA5_REG) == 0
&& REG_READ(EFUSE_BLK1_RDATA6_REG) == 0
&& REG_READ(EFUSE_BLK1_RDATA7_REG) == 0) {
ESP_LOGI(TAG, "Generating new flash encryption key...");
esp_efuse_write_random_key(EFUSE_BLK1_WDATA0_REG);
esp_efuse_burn_new_values();
ESP_LOGI(TAG, "Read & write protecting new key...");
REG_WRITE(EFUSE_BLK0_WDATA0_REG, EFUSE_WR_DIS_BLK1 | EFUSE_RD_DIS_BLK1);
esp_efuse_burn_new_values();
} else {
if(!(efuse_key_read_protected && efuse_key_write_protected)) {
ESP_LOGE(TAG, "Flash encryption key has to be either unset or both read and write protected");
return ESP_ERR_INVALID_STATE;
}
ESP_LOGW(TAG, "Using pre-loaded flash encryption key in EFUSE block 1");
}
/* CRYPT_CONFIG determines which bits of the AES block key are XORed
with bits from the flash address, to provide the key tweak.
CRYPT_CONFIG == 0 is effectively AES ECB mode (NOT SUPPORTED)
For now this is hardcoded to XOR all 256 bits of the key.
If you need to override it, you can pre-burn this efuse to the
desired value and then write-protect it, in which case this
operation does nothing. Please note this is not recommended!
*/
ESP_LOGI(TAG, "Setting CRYPT_CONFIG efuse to 0xF");
REG_WRITE(EFUSE_BLK0_WDATA5_REG, EFUSE_FLASH_CRYPT_CONFIG_M);
esp_efuse_burn_new_values();
uint32_t new_wdata6 = 0;
#ifndef CONFIG_FLASH_ENCRYPTION_UART_BOOTLOADER_ALLOW_ENCRYPT
ESP_LOGI(TAG, "Disable UART bootloader encryption...");
new_wdata6 |= EFUSE_DISABLE_DL_ENCRYPT;
#else
ESP_LOGW(TAG, "Not disabling UART bootloader encryption");
#endif
#ifndef CONFIG_FLASH_ENCRYPTION_UART_BOOTLOADER_ALLOW_DECRYPT
ESP_LOGI(TAG, "Disable UART bootloader decryption...");
new_wdata6 |= EFUSE_DISABLE_DL_DECRYPT;
#else
ESP_LOGW(TAG, "Not disabling UART bootloader decryption - SECURITY COMPROMISED");
#endif
#ifndef CONFIG_FLASH_ENCRYPTION_UART_BOOTLOADER_ALLOW_CACHE
ESP_LOGI(TAG, "Disable UART bootloader MMU cache...");
new_wdata6 |= EFUSE_DISABLE_DL_CACHE;
#else
ESP_LOGW(TAG, "Not disabling UART bootloader MMU cache - SECURITY COMPROMISED");
#endif
#ifndef CONFIG_SECURE_BOOT_ALLOW_JTAG
ESP_LOGI(TAG, "Disable JTAG...");
new_wdata6 |= EFUSE_RD_DISABLE_JTAG;
#else
ESP_LOGW(TAG, "Not disabling JTAG - SECURITY COMPROMISED");
#endif
#ifndef CONFIG_SECURE_BOOT_ALLOW_ROM_BASIC
ESP_LOGI(TAG, "Disable ROM BASIC interpreter fallback...");
new_wdata6 |= EFUSE_RD_CONSOLE_DEBUG_DISABLE;
#else
ESP_LOGW(TAG, "Not disabling ROM BASIC fallback - SECURITY COMPROMISED");
#endif
if (new_wdata6 != 0) {
REG_WRITE(EFUSE_BLK0_WDATA6_REG, new_wdata6);
esp_efuse_burn_new_values();
}
return ESP_OK;
}
/* Encrypt all flash data that should be encrypted */
static esp_err_t encrypt_flash_contents(uint32_t flash_crypt_cnt, bool flash_crypt_wr_dis)
{
esp_err_t err;
esp_partition_info_t partition_table[ESP_PARTITION_TABLE_MAX_ENTRIES];
int num_partitions;
/* If the last flash_crypt_cnt bit is burned or write-disabled, the
device can't re-encrypt itself. */
if (flash_crypt_wr_dis) {
ESP_LOGE(TAG, "Cannot re-encrypt data (FLASH_CRYPT_CNT 0x%02x write disabled %d", flash_crypt_cnt, flash_crypt_wr_dis);
return ESP_FAIL;
}
if (flash_crypt_cnt == 0) {
/* Very first flash of encrypted data: generate keys, etc. */
err = initialise_flash_encryption();
if (err != ESP_OK) {
return err;
}
}
err = encrypt_bootloader();
if (err != ESP_OK) {
return err;
}
err = encrypt_and_load_partition_table(partition_table, &num_partitions);
if (err != ESP_OK) {
return err;
}
/* Now iterate the just-loaded partition table, looking for entries to encrypt
*/
/* Go through each partition and encrypt if necessary */
for (int i = 0; i < num_partitions; i++) {
err = encrypt_partition(i, &partition_table[i]);
if (err != ESP_OK) {
return err;
}
}
ESP_LOGD(TAG, "All flash regions checked for encryption pass");
/* Set least significant 0-bit in flash_crypt_cnt */
int ffs_inv = __builtin_ffs((~flash_crypt_cnt) & EFUSE_RD_FLASH_CRYPT_CNT);
/* ffs_inv shouldn't be zero, as zero implies flash_crypt_cnt == EFUSE_RD_FLASH_CRYPT_CNT (0x7F) */
uint32_t new_flash_crypt_cnt = flash_crypt_cnt + (1 << (ffs_inv - 1));
ESP_LOGD(TAG, "FLASH_CRYPT_CNT 0x%x -> 0x%x", flash_crypt_cnt, new_flash_crypt_cnt);
REG_SET_FIELD(EFUSE_BLK0_WDATA0_REG, EFUSE_FLASH_CRYPT_CNT, new_flash_crypt_cnt);
#ifdef CONFIG_FLASH_ENCRYPTION_DISABLE_PLAINTEXT
ESP_LOGI(TAG, "Write protecting FLASH_CRYPT_CNT efuse...");
REG_SET_BIT(EFUSE_BLK0_WDATA0_REG, EFUSE_WR_DIS_FLASH_CRYPT_CNT);
#else
ESP_LOGW(TAG, "Not disabling FLASH_CRYPT_CNT - plaintext flashing is still possible");
#endif
esp_efuse_burn_new_values();
ESP_LOGI(TAG, "Flash encryption completed");
return ESP_OK;
}
static esp_err_t encrypt_bootloader()
{
esp_err_t err;
uint32_t image_length;
/* Check for plaintext bootloader (verification will fail if it's already encrypted) */
if (esp_image_verify_bootloader(&image_length) == ESP_OK) {
ESP_LOGD(TAG, "bootloader is plaintext. Encrypting...");
err = esp_flash_encrypt_region(ESP_BOOTLOADER_OFFSET, image_length);
if (err != ESP_OK) {
ESP_LOGE(TAG, "Failed to encrypt bootloader in place: 0x%x", err);
return err;
}
#ifdef CONFIG_SECURE_BOOT_ENABLED
/* If secure boot is enabled and bootloader was plaintext, also
* need to encrypt secure boot IV+digest.
*/
ESP_LOGD(TAG, "Encrypting secure bootloader IV & digest...");
err = esp_flash_encrypt_region(FLASH_OFFS_SECURE_BOOT_IV_DIGEST,
FLASH_SECTOR_SIZE);
if (err != ESP_OK) {
ESP_LOGE(TAG, "Failed to encrypt bootloader IV & digest in place: 0x%x", err);
return err;
}
#endif
}
else {
ESP_LOGW(TAG, "no valid bootloader was found");
}
return ESP_OK;
}
static esp_err_t encrypt_and_load_partition_table(esp_partition_info_t *partition_table, int *num_partitions)
{
esp_err_t err;
/* Check for plaintext partition table */
err = bootloader_flash_read(ESP_PARTITION_TABLE_OFFSET, partition_table, ESP_PARTITION_TABLE_MAX_LEN, false);
if (err != ESP_OK) {
ESP_LOGE(TAG, "Failed to read partition table data");
return err;
}
if (esp_partition_table_verify(partition_table, false, num_partitions) == ESP_OK) {
ESP_LOGD(TAG, "partition table is plaintext. Encrypting...");
esp_err_t err = esp_flash_encrypt_region(ESP_PARTITION_TABLE_OFFSET,
FLASH_SECTOR_SIZE);
if (err != ESP_OK) {
ESP_LOGE(TAG, "Failed to encrypt partition table in place. %x", err);
return err;
}
}
else {
ESP_LOGE(TAG, "Failed to read partition table data - not plaintext?");
return ESP_ERR_INVALID_STATE;
}
/* Valid partition table loded */
return ESP_OK;
}
static esp_err_t encrypt_partition(int index, const esp_partition_info_t *partition)
{
esp_err_t err;
bool should_encrypt = (partition->flags & PART_FLAG_ENCRYPTED);
if (partition->type == PART_TYPE_APP) {
/* check if the partition holds a valid unencrypted app */
esp_image_metadata_t data_ignored;
err = esp_image_verify(ESP_IMAGE_VERIFY,
&partition->pos,
&data_ignored);
should_encrypt = (err == ESP_OK);
} else if ((partition->type == PART_TYPE_DATA && partition->subtype == PART_SUBTYPE_DATA_OTA)
|| (partition->type == PART_TYPE_DATA && partition->subtype == PART_SUBTYPE_DATA_NVS_KEYS)) {
/* check if we have ota data partition and the partition should be encrypted unconditionally */
should_encrypt = true;
}
if (!should_encrypt) {
return ESP_OK;
}
else {
/* should_encrypt */
ESP_LOGI(TAG, "Encrypting partition %d at offset 0x%x...", index, partition->pos.offset);
err = esp_flash_encrypt_region(partition->pos.offset, partition->pos.size);
if (err != ESP_OK) {
ESP_LOGE(TAG, "Failed to encrypt partition %d", index);
}
return err;
}
}
esp_err_t esp_flash_encrypt_region(uint32_t src_addr, size_t data_length)
{
esp_err_t err;
uint32_t buf[FLASH_SECTOR_SIZE / sizeof(uint32_t)];
if (src_addr % FLASH_SECTOR_SIZE != 0) {
ESP_LOGE(TAG, "esp_flash_encrypt_region bad src_addr 0x%x",src_addr);
return ESP_FAIL;
}
for (size_t i = 0; i < data_length; i += FLASH_SECTOR_SIZE) {
rtc_wdt_feed();
uint32_t sec_start = i + src_addr;
err = bootloader_flash_read(sec_start, buf, FLASH_SECTOR_SIZE, false);
if (err != ESP_OK) {
goto flash_failed;
}
err = bootloader_flash_erase_sector(sec_start / FLASH_SECTOR_SIZE);
if (err != ESP_OK) {
goto flash_failed;
}
err = bootloader_flash_write(sec_start, buf, FLASH_SECTOR_SIZE, true);
if (err != ESP_OK) {
goto flash_failed;
}
}
return ESP_OK;
flash_failed:
ESP_LOGE(TAG, "flash operation failed: 0x%x", err);
return err;
}
void esp_flash_write_protect_crypt_cnt()
{
uint32_t efuse_blk0 = REG_READ(EFUSE_BLK0_RDATA0_REG);
bool flash_crypt_wr_dis = efuse_blk0 & EFUSE_WR_DIS_FLASH_CRYPT_CNT;
if(!flash_crypt_wr_dis) {
REG_WRITE(EFUSE_BLK0_WDATA0_REG, EFUSE_WR_DIS_FLASH_CRYPT_CNT);
esp_efuse_burn_new_values();
}
}
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