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feat(esp_security): Config to forcefully enable ECC constant-time operations during bootup

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This commit is contained in:
harshal.patil
2024-07-04 09:31:07 +05:30
parent 46cbaa7d4d
commit 39872a5575
2 changed files with 29 additions and 0 deletions
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13
components/esp_security/Kconfig
View File

@@ -37,4 +37,17 @@ menu "ESP Security Specific"
default 3 if ESP_CRYPTO_DPA_PROTECTION_LEVEL_HIGH
endmenu
config ESP_CRYPTO_FORCE_ECC_CONSTANT_TIME_POINT_MUL
bool "Forcfully enable ECC constant time point multiplication operations"
depends on SOC_ECC_CONSTANT_TIME_POINT_MUL
default N
help
If enabled, the app startup code will burn the ECC_FORCE_CONST_TIME efuse bit to force the
ECC peripheral to always perform constant time point multiplication operations,
irrespective of the ECC_MULT_SECURITY_MODE status bit that is present in the ECC_MULT_CONF_REG
register. By default, ESP-IDF configures the ECC peripheral to perform constant time point
multiplication operations, so enabling this config would provide security enhancement only in
the cases when trusted boot is not enabled and the attacker tries carrying out non-constant
time point multiplication operations by changing the default ESP-IDF configurations.
Performing constant time operations protect the ECC multiplication operations from timing attacks.
endmenu

16
components/esp_security/src/init.c
View File

@@ -7,7 +7,12 @@
#include "esp_private/startup_internal.h"
#include "sdkconfig.h"
#include "esp_crypto_clk.h"
#include "esp_efuse.h"
#include "esp_efuse_table.h"
#include "esp_security_priv.h"
#include "esp_err.h"
__attribute__((unused)) static const char *TAG = "esp_security";
ESP_SYSTEM_INIT_FN(esp_security_init, SECONDARY, BIT(0), 103)
{
@@ -15,6 +20,17 @@ ESP_SYSTEM_INIT_FN(esp_security_init, SECONDARY, BIT(0), 103)
#if CONFIG_ESP_CRYPTO_DPA_PROTECTION_AT_STARTUP
esp_crypto_dpa_protection_startup();
#endif
#ifdef CONFIG_ESP_CRYPTO_FORCE_ECC_CONSTANT_TIME_POINT_MUL
if (!esp_efuse_read_field_bit(ESP_EFUSE_ECC_FORCE_CONST_TIME)) {
ESP_EARLY_LOGD(TAG, "Forcefully enabling ECC constant time operations");
esp_err_t err = esp_efuse_write_field_bit(ESP_EFUSE_ECC_FORCE_CONST_TIME);
if (err != ESP_OK) {
ESP_EARLY_LOGE(TAG, "Enabling ECC constant time operations forcefully failed.");
return err;
}
}
#endif
return ESP_OK;
}