210 lines
7.1 KiB
C
210 lines
7.1 KiB
C
// Copyright 2015-2016 Espressif Systems (Shanghai) PTE LTD
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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#include <string.h>
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#include "esp_attr.h"
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#include "esp_types.h"
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#include "esp_log.h"
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#include "rom/cache.h"
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#include "rom/ets_sys.h"
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#include "rom/secure_boot.h"
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#include "soc/dport_reg.h"
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#include "soc/io_mux_reg.h"
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#include "soc/efuse_reg.h"
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#include "soc/rtc_cntl_reg.h"
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#include "sdkconfig.h"
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#include "bootloader_flash.h"
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#include "bootloader_random.h"
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#include "esp_image_format.h"
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#include "esp_secure_boot.h"
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#include "esp_flash_encrypt.h"
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#include "esp_efuse.h"
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static const char* TAG = "secure_boot";
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/**
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* @function : secure_boot_generate
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* @description: generate boot digest (aka "abstract") & iv
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*
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* @inputs: image_len - length of image to calculate digest for
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*/
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static bool secure_boot_generate(uint32_t image_len){
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esp_err_t err;
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esp_secure_boot_iv_digest_t digest;
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const uint32_t *image;
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/* hardware secure boot engine only takes full blocks, so round up the
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image length. The additional data should all be 0xFF (or the appended SHA, if it falls in the same block).
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*/
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if (image_len % sizeof(digest.iv) != 0) {
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image_len = (image_len / sizeof(digest.iv) + 1) * sizeof(digest.iv);
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}
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ets_secure_boot_start();
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ets_secure_boot_rd_iv((uint32_t *)digest.iv);
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ets_secure_boot_hash(NULL);
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/* iv stored in sec 0 */
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err = bootloader_flash_erase_sector(0);
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if (err != ESP_OK)
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{
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ESP_LOGE(TAG, "SPI erase failed: 0x%x", err);
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return false;
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}
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/* generate digest from image contents */
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image = bootloader_mmap(ESP_BOOTLOADER_OFFSET, image_len);
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if (!image) {
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ESP_LOGE(TAG, "bootloader_mmap(0x1000, 0x%x) failed", image_len);
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return false;
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}
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for (int i = 0; i < image_len; i+= sizeof(digest.iv)) {
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ets_secure_boot_hash(&image[i/sizeof(uint32_t)]);
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}
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bootloader_munmap(image);
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ets_secure_boot_obtain();
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ets_secure_boot_rd_abstract((uint32_t *)digest.digest);
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ets_secure_boot_finish();
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ESP_LOGD(TAG, "write iv+digest to flash");
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err = bootloader_flash_write(FLASH_OFFS_SECURE_BOOT_IV_DIGEST, &digest,
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sizeof(digest), esp_flash_encryption_enabled());
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if (err != ESP_OK) {
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ESP_LOGE(TAG, "SPI write failed: 0x%x", err);
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return false;
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}
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Cache_Read_Enable(0);
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return true;
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}
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/* Burn values written to the efuse write registers */
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static inline void burn_efuses()
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{
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#ifdef CONFIG_SECURE_BOOT_TEST_MODE
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ESP_LOGE(TAG, "SECURE BOOT TEST MODE. Not really burning any efuses! NOT SECURE");
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#else
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esp_efuse_burn_new_values();
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#endif
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}
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esp_err_t esp_secure_boot_permanently_enable(void) {
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esp_err_t err;
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if (esp_secure_boot_enabled())
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{
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ESP_LOGI(TAG, "bootloader secure boot is already enabled, continuing..");
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return ESP_OK;
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}
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uint32_t coding_scheme = REG_GET_FIELD(EFUSE_BLK0_RDATA6_REG, EFUSE_CODING_SCHEME);
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if (coding_scheme != EFUSE_CODING_SCHEME_VAL_NONE && coding_scheme != EFUSE_CODING_SCHEME_VAL_34) {
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ESP_LOGE(TAG, "Unknown/unsupported CODING_SCHEME value 0x%x", coding_scheme);
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return ESP_ERR_NOT_SUPPORTED;
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}
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/* Verify the bootloader */
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esp_image_metadata_t bootloader_data = { 0 };
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err = esp_image_verify_bootloader_data(&bootloader_data);
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if (err != ESP_OK) {
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ESP_LOGE(TAG, "bootloader image appears invalid! error %d", err);
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return err;
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}
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uint32_t dis_reg = REG_READ(EFUSE_BLK0_RDATA0_REG);
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bool efuse_key_read_protected = dis_reg & EFUSE_RD_DIS_BLK2;
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bool efuse_key_write_protected = dis_reg & EFUSE_WR_DIS_BLK2;
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if (efuse_key_read_protected == false
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&& efuse_key_write_protected == false
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&& REG_READ(EFUSE_BLK2_RDATA0_REG) == 0
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&& REG_READ(EFUSE_BLK2_RDATA1_REG) == 0
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&& REG_READ(EFUSE_BLK2_RDATA2_REG) == 0
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&& REG_READ(EFUSE_BLK2_RDATA3_REG) == 0
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&& REG_READ(EFUSE_BLK2_RDATA4_REG) == 0
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&& REG_READ(EFUSE_BLK2_RDATA5_REG) == 0
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&& REG_READ(EFUSE_BLK2_RDATA6_REG) == 0
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&& REG_READ(EFUSE_BLK2_RDATA7_REG) == 0) {
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ESP_LOGI(TAG, "Generating new secure boot key...");
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esp_efuse_write_random_key(EFUSE_BLK2_WDATA0_REG);
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burn_efuses();
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ESP_LOGI(TAG, "Read & write protecting new key...");
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REG_WRITE(EFUSE_BLK0_WDATA0_REG, EFUSE_WR_DIS_BLK2 | EFUSE_RD_DIS_BLK2);
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burn_efuses();
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efuse_key_read_protected = true;
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efuse_key_write_protected = true;
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} else {
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ESP_LOGW(TAG, "Using pre-loaded secure boot key in EFUSE block 2");
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}
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ESP_LOGI(TAG, "Generating secure boot digest...");
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uint32_t image_len = bootloader_data.image_len;
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if(bootloader_data.image.hash_appended) {
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/* Secure boot digest doesn't cover the hash */
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image_len -= ESP_IMAGE_HASH_LEN;
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}
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if (false == secure_boot_generate(image_len)){
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ESP_LOGE(TAG, "secure boot generation failed");
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return ESP_FAIL;
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}
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ESP_LOGI(TAG, "Digest generation complete.");
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#ifndef CONFIG_SECURE_BOOT_TEST_MODE
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if (!efuse_key_read_protected) {
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ESP_LOGE(TAG, "Pre-loaded key is not read protected. Refusing to blow secure boot efuse.");
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return ESP_ERR_INVALID_STATE;
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}
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if (!efuse_key_write_protected) {
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ESP_LOGE(TAG, "Pre-loaded key is not write protected. Refusing to blow secure boot efuse.");
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return ESP_ERR_INVALID_STATE;
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}
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#endif
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ESP_LOGI(TAG, "blowing secure boot efuse...");
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ESP_LOGD(TAG, "before updating, EFUSE_BLK0_RDATA6 %x", REG_READ(EFUSE_BLK0_RDATA6_REG));
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uint32_t new_wdata6 = EFUSE_RD_ABS_DONE_0;
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#ifndef CONFIG_SECURE_BOOT_ALLOW_JTAG
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ESP_LOGI(TAG, "Disable JTAG...");
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new_wdata6 |= EFUSE_RD_DISABLE_JTAG;
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#else
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ESP_LOGW(TAG, "Not disabling JTAG - SECURITY COMPROMISED");
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#endif
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#ifndef CONFIG_SECURE_BOOT_ALLOW_ROM_BASIC
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ESP_LOGI(TAG, "Disable ROM BASIC interpreter fallback...");
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new_wdata6 |= EFUSE_RD_CONSOLE_DEBUG_DISABLE;
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#else
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ESP_LOGW(TAG, "Not disabling ROM BASIC fallback - SECURITY COMPROMISED");
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#endif
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REG_WRITE(EFUSE_BLK0_WDATA6_REG, new_wdata6);
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burn_efuses();
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uint32_t after = REG_READ(EFUSE_BLK0_RDATA6_REG);
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ESP_LOGD(TAG, "after updating, EFUSE_BLK0_RDATA6 %x", after);
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if (after & EFUSE_RD_ABS_DONE_0) {
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ESP_LOGI(TAG, "secure boot is now enabled for bootloader image");
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return ESP_OK;
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} else {
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#ifdef CONFIG_SECURE_BOOT_TEST_MODE
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ESP_LOGE(TAG, "secure boot not enabled due to test mode");
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#else
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ESP_LOGE(TAG, "secure boot not enabled for bootloader image, EFUSE_RD_ABS_DONE_0 is probably write protected!");
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#endif
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return ESP_ERR_INVALID_STATE;
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}
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}
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