1 /*
2 * SPDX-FileCopyrightText: 2015-2021 Espressif Systems (Shanghai) CO LTD
3 *
4 * SPDX-License-Identifier: Apache-2.0
5 */
6
7 #include <strings.h>
8 #include "sdkconfig.h"
9 #include "esp_log.h"
10 #include "esp_efuse.h"
11 #include "esp_efuse_table.h"
12 #include "esp_secure_boot.h"
13
14 #ifndef BOOTLOADER_BUILD
15 static __attribute__((unused)) const char *TAG = "secure_boot";
16
17 #ifdef CONFIG_SECURE_BOOT
efuse_batch_write_begin(bool * need_fix)18 static void efuse_batch_write_begin(bool *need_fix)
19 {
20 if (*need_fix == false) {
21 esp_efuse_batch_write_begin();
22 }
23 *need_fix = true;
24 }
25
update_efuses(bool need_fix,esp_err_t err)26 static void update_efuses(bool need_fix, esp_err_t err)
27 {
28 if (need_fix) {
29 if (err != ESP_OK) {
30 ESP_LOGE(TAG, "Can not be fixed (err=0x%x).", err);
31 esp_efuse_batch_write_cancel();
32 } else {
33 err = esp_efuse_batch_write_commit();
34 if (err != ESP_OK) {
35 ESP_LOGE(TAG, "Error programming eFuses (err=0x%x)", err);
36 return;
37 } else {
38 ESP_LOGI(TAG, "Fixed");
39 }
40 }
41 }
42 }
43 #ifdef CONFIG_SECURE_BOOT_V1_ENABLED
secure_boot_v1_check(bool * need_fix)44 static esp_err_t secure_boot_v1_check(bool *need_fix)
45 {
46 esp_err_t err = ESP_OK;
47 esp_efuse_block_t block = EFUSE_BLK_SECURE_BOOT;
48 if (!esp_efuse_get_key_dis_read(block)) {
49 efuse_batch_write_begin(need_fix);
50 ESP_LOGW(TAG, "eFuse BLOCK%d should not be readable. Fixing..", block);
51 err = esp_efuse_set_key_dis_read(block);
52 }
53 if (!esp_efuse_get_key_dis_write(block)) {
54 efuse_batch_write_begin(need_fix);
55 ESP_LOGW(TAG, "eFuse BLOCK%d should not be writeable. Fixing..", block);
56 if (err == ESP_OK) {
57 err = esp_efuse_set_key_dis_write(block);
58 }
59 }
60 return err;
61 }
62 #elif SOC_EFUSE_SECURE_BOOT_KEY_DIGESTS == 1 && CONFIG_SECURE_BOOT_V2_ENABLED
secure_boot_v2_check(bool * need_fix)63 static esp_err_t secure_boot_v2_check(bool *need_fix)
64 {
65 esp_err_t err = ESP_OK;
66 esp_efuse_block_t block = EFUSE_BLK_SECURE_BOOT;
67 if (esp_efuse_get_key_dis_read(block)) {
68 ESP_LOGE(TAG, "eFuse BLOCK%d should be readable", block);
69 abort();
70 // This code is not achievable because the bootloader will not boot an app in this state.
71 // But we keep it here just in case (any unexpected behavior).
72 }
73 if (esp_efuse_block_is_empty(block)) {
74 ESP_LOGE(TAG, "eFuse BLOCK%d should not be empty", block);
75 abort();
76 // This code is not achievable because the bootloader will not boot an app in this state.
77 // But we keep it here just in case (any unexpected behavior).
78 }
79 if (!esp_efuse_get_key_dis_write(block)) {
80 efuse_batch_write_begin(need_fix);
81 ESP_LOGW(TAG, "eFuse BLOCK%d should not be writeable. Fixing..", block);
82 err = esp_efuse_set_key_dis_write(block);
83 }
84 return err;
85 }
86 #elif SOC_EFUSE_SECURE_BOOT_KEY_DIGESTS > 1 && CONFIG_SECURE_BOOT_V2_ENABLED
secure_boot_v2_check(bool * need_fix)87 static esp_err_t secure_boot_v2_check(bool *need_fix)
88 {
89 esp_err_t err = ESP_OK;
90 esp_efuse_purpose_t purpose[SOC_EFUSE_SECURE_BOOT_KEY_DIGESTS] = {
91 ESP_EFUSE_KEY_PURPOSE_SECURE_BOOT_DIGEST0,
92 ESP_EFUSE_KEY_PURPOSE_SECURE_BOOT_DIGEST1,
93 ESP_EFUSE_KEY_PURPOSE_SECURE_BOOT_DIGEST2,
94 };
95
96 for (unsigned i = 0; i < SOC_EFUSE_SECURE_BOOT_KEY_DIGESTS; ++i) {
97 esp_efuse_block_t block;
98 if (esp_efuse_find_purpose(purpose[i], &block)) {
99 if (!esp_efuse_get_digest_revoke(i)) {
100 if (esp_efuse_get_key_dis_read(block)) {
101 ESP_LOGE(TAG, "eFuse BLOCK%d should be readable", block);
102 abort();
103 // This state is not expected unless the eFuses have been manually misconfigured.
104 }
105 if (esp_efuse_block_is_empty(block)) {
106 ESP_LOGE(TAG, "eFuse BLOCK%d should not be empty", block);
107 abort();
108 // This state is not expected unless the eFuses have been manually misconfigured.
109 }
110 if (!esp_efuse_get_key_dis_write(block)) {
111 efuse_batch_write_begin(need_fix);
112 ESP_LOGW(TAG, "eFuse BLOCK%d should not be writeable. Fixing..", block);
113 if (err == ESP_OK) {
114 err = esp_efuse_set_key_dis_write(block);
115 }
116 }
117 }
118 if (!esp_efuse_get_keypurpose_dis_write(block)) {
119 efuse_batch_write_begin(need_fix);
120 ESP_LOGW(TAG, "The KEY_PURPOSE_SECURE_BOOT_DIGEST%d should be write-protected. Fixing..", block);
121 if (err == ESP_OK) {
122 err = esp_efuse_set_keypurpose_dis_write(block);
123 }
124 }
125 } else {
126 if (!esp_efuse_get_digest_revoke(i)) {
127 #ifndef CONFIG_SECURE_BOOT_ALLOW_UNUSED_DIGEST_SLOTS
128 efuse_batch_write_begin(need_fix);
129 ESP_LOGW(TAG, "Unused SECURE_BOOT_DIGEST%d should be revoked. Fixing..", i);
130 if (err == ESP_OK) {
131 err = esp_efuse_set_digest_revoke(i);
132 }
133 #else
134 ESP_LOGW(TAG, "Unused SECURE_BOOT_DIGEST%d should be revoked. It will not be fixed due to the config", i);
135 #endif
136 }
137 }
138 }
139 return err;
140 }
141 #endif
142 #endif // CONFIG_SECURE_BOOT
143
144 #if CONFIG_SECURE_SIGNED_APPS_RSA_SCHEME && CONFIG_SECURE_SIGNED_ON_UPDATE_NO_SECURE_BOOT
145
rsa_check_signature_on_update_check(void)146 static void rsa_check_signature_on_update_check(void)
147 {
148 // We rely on the keys used to sign this app to verify the next app on OTA, so make sure there is at
149 // least one to avoid a stuck firmware
150 esp_image_sig_public_key_digests_t digests = { 0 };
151
152 esp_err_t err = esp_secure_boot_get_signature_blocks_for_running_app(false, &digests);
153
154 if (err != ESP_OK || digests.num_digests == 0) {
155 ESP_LOGE(TAG, "This app is not signed, but check signature on update is enabled in config. It won't be possible to verify any update.");
156 abort();
157 }
158 #if CONFIG_SECURE_SIGNED_ON_UPDATE_NO_SECURE_BOOT && SECURE_BOOT_NUM_BLOCKS > 1
159 if (digests.num_digests > 1) {
160 ESP_LOGW(TAG, "App has %d signatures. Only the first position of signature blocks is used to verify any update", digests.num_digests);
161 }
162 #endif
163 }
164 #endif // CONFIG_SECURE_SIGNED_APPS_RSA_SCHEME && CONFIG_SECURE_SIGNED_ON_UPDATE_NO_SECURE_BOOT
165
esp_secure_boot_init_checks(void)166 void esp_secure_boot_init_checks(void)
167 {
168 #ifdef CONFIG_SECURE_BOOT
169
170 if (esp_secure_boot_enabled()) {
171 bool need_fix = false;
172 #ifdef CONFIG_SECURE_BOOT_V1_ENABLED
173 esp_err_t err = secure_boot_v1_check(&need_fix);
174 #else
175 esp_err_t err = secure_boot_v2_check(&need_fix);
176 #endif
177 update_efuses(need_fix, err);
178 } else {
179 ESP_LOGE(TAG, "Mismatch in secure boot settings: the app config is enabled but eFuse not");
180 }
181 #endif // CONFIG_SECURE_BOOT
182
183
184 #if CONFIG_SECURE_SIGNED_APPS_RSA_SCHEME && CONFIG_SECURE_SIGNED_ON_UPDATE_NO_SECURE_BOOT
185 rsa_check_signature_on_update_check();
186 #endif // CONFIG_SECURE_SIGNED_APPS_RSA_SCHEME && CONFIG_SECURE_SIGNED_ON_UPDATE_NO_SECURE_BOOT
187
188 }
189 #endif // not BOOTLOADER_BUILD
190
