esp-idf/components/bootloader_support/src/secure_boot.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 <string.h>
#include "esp_attr.h"
#include "esp_types.h"
#include "esp_log.h"
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#include "rom/cache.h"
#include "rom/ets_sys.h"
#include "rom/secure_boot.h"
#include "soc/dport_reg.h"
#include "soc/io_mux_reg.h"
#include "soc/efuse_reg.h"
#include "soc/rtc_cntl_reg.h"
#include "sdkconfig.h"
#include "bootloader_flash.h"
#include "bootloader_random.h"
#include "esp_image_format.h"
#include "esp_secure_boot.h"
#include "esp_flash_encrypt.h"
#include "esp_efuse.h"
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static const char* TAG = "secure_boot";
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/**
* @function : secure_boot_generate
* @description: generate boot digest (aka "abstract") & iv
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*
* @inputs: image_len - length of image to calculate digest for
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*/
static bool secure_boot_generate(uint32_t image_len){
esp_err_t err;
esp_secure_boot_iv_digest_t digest;
const uint32_t *image;
/* hardware secure boot engine only takes full blocks, so round up the
image length. The additional data should all be 0xFF.
*/
if (image_len % sizeof(digest.iv) != 0) {
image_len = (image_len / sizeof(digest.iv) + 1) * sizeof(digest.iv);
}
ets_secure_boot_start();
ets_secure_boot_rd_iv((uint32_t *)digest.iv);
ets_secure_boot_hash(NULL);
/* iv stored in sec 0 */
err = bootloader_flash_erase_sector(0);
if (err != ESP_OK)
{
ESP_LOGE(TAG, "SPI erase failed: 0x%x", err);
return false;
}
/* generate digest from image contents */
image = bootloader_mmap(0x1000, image_len);
if (!image) {
ESP_LOGE(TAG, "bootloader_mmap(0x1000, 0x%x) failed", image_len);
return false;
}
for (int i = 0; i < image_len; i+= sizeof(digest.iv)) {
ets_secure_boot_hash(&image[i/sizeof(uint32_t)]);
}
bootloader_munmap(image);
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ets_secure_boot_obtain();
ets_secure_boot_rd_abstract((uint32_t *)digest.digest);
ets_secure_boot_finish();
ESP_LOGD(TAG, "write iv+digest to flash");
err = bootloader_flash_write(FLASH_OFFS_SECURE_BOOT_IV_DIGEST, &digest,
sizeof(digest), esp_flash_encryption_enabled());
if (err != ESP_OK) {
ESP_LOGE(TAG, "SPI write failed: 0x%x", err);
return false;
}
Cache_Read_Enable(0);
return true;
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}
/* Burn values written to the efuse write registers */
static inline void burn_efuses()
{
#ifdef CONFIG_SECURE_BOOT_TEST_MODE
ESP_LOGE(TAG, "SECURE BOOT TEST MODE. Not really burning any efuses! NOT SECURE");
#else
esp_efuse_burn_new_values();
#endif
}
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esp_err_t esp_secure_boot_permanently_enable(void) {
esp_err_t err;
uint32_t image_len = 0;
if (esp_secure_boot_enabled())
{
ESP_LOGI(TAG, "bootloader secure boot is already enabled, continuing..");
return ESP_OK;
}
err = esp_image_basic_verify(0x1000, true, &image_len);
if (err != ESP_OK) {
ESP_LOGE(TAG, "bootloader image appears invalid! error %d", err);
return err;
}
uint32_t dis_reg = REG_READ(EFUSE_BLK0_RDATA0_REG);
bool efuse_key_read_protected = dis_reg & EFUSE_RD_DIS_BLK2;
bool efuse_key_write_protected = dis_reg & EFUSE_WR_DIS_BLK2;
if (efuse_key_read_protected == false
&& efuse_key_write_protected == false
&& REG_READ(EFUSE_BLK2_RDATA0_REG) == 0
&& REG_READ(EFUSE_BLK2_RDATA1_REG) == 0
&& REG_READ(EFUSE_BLK2_RDATA2_REG) == 0
&& REG_READ(EFUSE_BLK2_RDATA3_REG) == 0
&& REG_READ(EFUSE_BLK2_RDATA4_REG) == 0
&& REG_READ(EFUSE_BLK2_RDATA5_REG) == 0
&& REG_READ(EFUSE_BLK2_RDATA6_REG) == 0
&& REG_READ(EFUSE_BLK2_RDATA7_REG) == 0) {
ESP_LOGI(TAG, "Generating new secure boot key...");
uint32_t buf[8];
bootloader_fill_random(buf, sizeof(buf));
for (int i = 0; i < 8; i++) {
ESP_LOGV(TAG, "EFUSE_BLK2_WDATA%d_REG = 0x%08x", i, buf[i]);
REG_WRITE(EFUSE_BLK2_WDATA0_REG + 4*i, buf[i]);
}
bzero(buf, sizeof(buf));
burn_efuses();
ESP_LOGI(TAG, "Read & write protecting new key...");
REG_WRITE(EFUSE_BLK0_WDATA0_REG, EFUSE_WR_DIS_BLK2 | EFUSE_RD_DIS_BLK2);
burn_efuses();
efuse_key_read_protected = true;
efuse_key_write_protected = true;
} else {
ESP_LOGW(TAG, "Using pre-loaded secure boot key in EFUSE block 2");
}
ESP_LOGI(TAG, "Generating secure boot digest...");
if (false == secure_boot_generate(image_len)){
ESP_LOGE(TAG, "secure boot generation failed");
return ESP_FAIL;
}
ESP_LOGI(TAG, "Digest generation complete.");
#ifndef CONFIG_SECURE_BOOT_TEST_MODE
if (!efuse_key_read_protected) {
ESP_LOGE(TAG, "Pre-loaded key is not read protected. Refusing to blow secure boot efuse.");
return ESP_ERR_INVALID_STATE;
}
if (!efuse_key_write_protected) {
ESP_LOGE(TAG, "Pre-loaded key is not write protected. Refusing to blow secure boot efuse.");
return ESP_ERR_INVALID_STATE;
}
#endif
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ESP_LOGI(TAG, "blowing secure boot efuse...");
ESP_LOGD(TAG, "before updating, EFUSE_BLK0_RDATA6 %x", REG_READ(EFUSE_BLK0_RDATA6_REG));
uint32_t new_wdata6 = EFUSE_RD_ABS_DONE_0;
#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
REG_WRITE(EFUSE_BLK0_WDATA6_REG, new_wdata6);
burn_efuses();
uint32_t after = REG_READ(EFUSE_BLK0_RDATA6_REG);
ESP_LOGD(TAG, "after updating, EFUSE_BLK0_RDATA6 %x", after);
if (after & EFUSE_RD_ABS_DONE_0) {
ESP_LOGI(TAG, "secure boot is now enabled for bootloader image");
return ESP_OK;
} else {
#ifdef CONFIG_SECURE_BOOT_TEST_MODE
ESP_LOGE(TAG, "secure boot not enabled due to test mode");
#else
ESP_LOGE(TAG, "secure boot not enabled for bootloader image, EFUSE_RD_ABS_DONE_0 is probably write protected!");
#endif
return ESP_ERR_INVALID_STATE;
}
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}