Flash encryption / secure boot: Temporarily disable on-device key generation

Will be enabled after seeding of HWRNG in bootloader is fully tested/qualified.

diff --git a/components/bootloader_support/src/flash_encrypt.c b/components/bootloader_support/src/flash_encrypt.c
index 8b9ca60cd1a72a1e95933562d174b06428c4d781..f4fd7e783dfc251e09f8619ce42cd141efe4420d 100644 (file)
--- a/components/bootloader_support/src/flash_encrypt.c
+++ b/components/bootloader_support/src/flash_encrypt.c
@@ -78,19 +78,12 @@ static esp_err_t initialise_flash_encryption(void)
         && 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...");
-        uint32_t buf[8];
-        bootloader_fill_random(buf, sizeof(buf));
-        for (int i = 0; i < 8; i++) {
-            ESP_LOGV(TAG, "EFUSE_BLK1_WDATA%d_REG = 0x%08x", i, buf[i]);
-            REG_WRITE(EFUSE_BLK1_WDATA0_REG + 4*i, buf[i]);
-        }
-        bzero(buf, sizeof(buf));
-        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();
+        /* On-device key generation is temporarily disabled, until
+         * RNG operation during bootloader is qualified.
+         * See docs/security/flash-encryption.rst for details. */
+        ESP_LOGE(TAG, "On-device key generation is not yet available.");
+        return ESP_ERR_NOT_SUPPORTED;
     } else {
 
         if(!(efuse_key_read_protected && efuse_key_write_protected)) {

diff --git a/components/bootloader_support/src/secure_boot.c b/components/bootloader_support/src/secure_boot.c
index 0230e85ad5348b633e2e0d0b4e378d0eabcc2a9b..c5ae1f19ea6ffe59df411c7cc9b21d7984c0310e 100644 (file)
--- a/components/bootloader_support/src/secure_boot.c
+++ b/components/bootloader_support/src/secure_boot.c
@@ -130,21 +130,12 @@ esp_err_t esp_secure_boot_permanently_enable(void) {
         && 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;
 
+        /* On-device key generation is temporarily disabled, until
+         * RNG operation during bootloader is qualified.
+         * See docs/security/secure-boot.rst for details. */
+        ESP_LOGE(TAG, "On-device key generation is not yet available.");
+        return ESP_ERR_NOT_SUPPORTED;
     } else {
         ESP_LOGW(TAG, "Using pre-loaded secure boot key in EFUSE block 2");
     }

diff --git a/docs/security/flash-encryption.rst b/docs/security/flash-encryption.rst
index 298a0a75bf67cd2fe7d05b29e68f96a0a09f2f42..b73d8a9ad35bc8242eb8eb816e41319cd93ab233 100644 (file)
--- a/docs/security/flash-encryption.rst
+++ b/docs/security/flash-encryption.rst
@@ -7,6 +7,9 @@ Flash Encryption is separate from the `Secure Boot` feature, and you can use fla
 
 **IMPORTANT: Enabling flash encryption limits your options for further updates of your ESP32. Make sure to read this document (including `Limitations of Flash Encryption` and understand the implications of enabling flash encryption.**
 
+**IMPORTANT: Flash Encryption feature is currently enabled for development use only, with a key generated on the host. The recommended production configuration, where the flash encryption key is generated by the device on first boot, is currently disabled while final testing is done. This documentation refers to flash encryption keys being generated on first boot, however for now it is necessary to follow the additional steps shown under `Precalculated Flash Encryption Key`.**
+
+
 Background
 ----------
 

diff --git a/docs/security/secure-boot.rst b/docs/security/secure-boot.rst
index ef969538b90c9f4d672345fd86fbf43211856605..65b6bab48f6662c9d13e090d9bc7b1a538f75ffd 100644 (file)
--- a/docs/security/secure-boot.rst
+++ b/docs/security/secure-boot.rst
@@ -5,7 +5,7 @@ Secure Boot is a feature for ensuring only your code can run on the chip. Data l
 
 Secure Boot is separate from the `Flash Encryption` feature, and you can use secure boot without encrypting the flash contents. However we recommend using both features together for a secure environment.
 
-**IMPORTANT: As Encrypted Flash feature and related security features are not yet released, Secure Boot should not be considered sufficient for a secure device and we strongly recommend not enabling the one-time secure bootloader feature until it is mature.**
+**IMPORTANT: Secure Boot feature is currently enabled for development use only, with a key generated on the host. The recommended production configuration, where the secure boot key is generated by the device on first boot, is currently disabled while final testing is done. This documentation refers to "One-Time Flashable" mode (where keys are generated on the device), but for now only the `Re-Flashable Software Bootloader` mode is available.**
 
 Background
 ----------