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esp32c3/Digital Signature: mbedtls integration through ESP-TLS

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This commit is contained in:
Aditya Patwardhan 2021-01-17 21:38:34 +05:30
parent cf9ac2ef9e
commit 79c23a1886
10 changed files with 59 additions and 38 deletions
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2
components/esp-tls/Kconfig
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@ -26,7 +26,7 @@ menu "ESP-TLS"
config ESP_TLS_USE_DS_PERIPHERAL
bool "Use Digital Signature (DS) Peripheral with ESP-TLS"
depends on IDF_TARGET_ESP32S2 && ESP_TLS_USING_MBEDTLS
depends on (IDF_TARGET_ESP32C3 || IDF_TARGET_ESP32S2) && ESP_TLS_USING_MBEDTLS
default y
help
Enable use of the Digital Signature Peripheral for ESP-TLS.The DS peripheral

1
components/esp32c3/include/esp_ds.h
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@ -30,6 +30,7 @@ extern "C" {
is produced anyway and can be read*/
#define ESP_DS_IV_BIT_LEN 128
#define ESP_DS_IV_LEN (ESP_DS_IV_BIT_LEN / 8)
#define ESP_DS_SIGNATURE_MAX_BIT_LEN 3072
#define ESP_DS_SIGNATURE_MD_BIT_LEN 256
#define ESP_DS_SIGNATURE_M_PRIME_BIT_LEN 32

3
components/mbedtls/CMakeLists.txt
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@ -122,8 +122,9 @@ target_sources(mbedcrypto PRIVATE "${COMPONENT_DIR}/port/esp_hardware.c"
"${AES_DMA_SRCS}"
)
# CONFIG_ESP_TLS_USE_DS_PERIPHERAL can be enabled only for the supported targets.
if(CONFIG_ESP_TLS_USE_DS_PERIPHERAL)
target_sources(mbedcrypto PRIVATE "${COMPONENT_DIR}/port/esp32s2/esp_rsa_sign_alt.c")
target_sources(mbedcrypto PRIVATE "${COMPONENT_DIR}/port/esp_ds/esp_rsa_sign_alt.c")
endif()
# Note: some mbedTLS hardware acceleration can be enabled/disabled by config.

8
components/mbedtls/port/esp32s2/esp_rsa_sign_alt.c → components/mbedtls/port/esp_ds/esp_rsa_sign_alt.c
View File

@ -14,7 +14,15 @@
#include "esp_ds.h"
#include "rsa_sign_alt.h"
#ifdef CONFIG_IDF_TARGET_ESP32S2
#include "esp32s2/rom/digital_signature.h"
#elif CONFIG_IDF_TARGET_ESP32C3
#include "esp32c3/rom/digital_signature.h"
#else
#error "Selected target does not support esp_rsa_sign_alt (for DS)"
#endif
#include "esp_log.h"
#include "esp_heap_caps.h"
#include "freertos/FreeRTOS.h"

0
components/mbedtls/port/include/esp32s2/esp_rsa_sign_alt.h → components/mbedtls/port/include/esp_ds/esp_rsa_sign_alt.h
View File

4
components/mbedtls/port/include/rsa_sign_alt.h
View File

@ -22,9 +22,7 @@ extern "C" {
#endif
#ifdef CONFIG_ESP_TLS_USE_DS_PERIPHERAL
#include "esp32s2/esp_rsa_sign_alt.h"
#include "esp_ds/esp_rsa_sign_alt.h"
#else
#error "DS configuration flags not activated, please enable required menuconfig flags"

14
examples/protocols/mqtt/ssl_ds/README.md
View File

@ -1,8 +1,8 @@
| Supported Targets | ESP32-S2 |
| Supported Targets | ESP32-S2 | ESP32-C3 |
# ESP-MQTT SSL Mutual Authentication with Digital Signature
(See the README.md file in the upper level 'examples' directory for more information about examples.)
Espressif's ESP32-S2 MCU has a built-in Digital Signature (DS) Peripheral, which provides hardware acceleration for RSA signature. More details can be found at [Digital Signature with ESP-TLS](https://docs.espressif.com/projects/esp-idf/en/latest/esp32s2/api-reference/protocols/esp_tls.html#digital-signature-with-esp-tls).
Espressif's ESP32-S2 and ESP32-C3 MCU have a built-in Digital Signature (DS) Peripheral, which provides hardware acceleration for RSA signature. More details can be found at [Digital Signature with ESP-TLS](https://docs.espressif.com/projects/esp-idf/en/latest/esp32s2/api-reference/protocols/esp_tls.html#digital-signature-with-esp-tls).
This example connects to the broker test.mosquitto.org using ssl transport with client certificate(RSA) and as a demonstration subscribes/unsubscribes and sends a message on certain topic.The RSA signature operation required in the ssl connection is performed with help of the Digital Signature (DS) peripheral.
(Please note that the public broker is maintained by the community so may not be always available, for details please visit http://test.mosquitto.org)
@ -12,14 +12,14 @@ It uses ESP-MQTT library which implements mqtt client to connect to mqtt broker.
### Hardware Required
This example can be executed on any ESP32-S2 board (which has a built-in DS peripheral), the only required interface is WiFi and connection to internet.
This example can be executed on any ESP32-S2, ESP32-C3 board (which has a built-in DS peripheral), the only required interface is WiFi and connection to internet.
### Configure the project
#### 1) Selecting the target
As the project is to be built for the target ESP32-S2, it should be selected with the following command
As the project is to be built for the target ESP32-S2, ESP32-C3 it should be selected with the following command
```
idf.py set-target esp32s2
idf.py set-target /* target */
```
More detials can be found at [Selecting the target](https://docs.espressif.com/projects/esp-idf/en/latest/esp32/api-guides/build-system.html#selecting-the-target).
@ -50,7 +50,7 @@ Please note, that the supplied file `client.crt` in the `main` directory is only
python configure_ds.py --port /* USB COM port */ --private-key /* RSA priv key */
```
In the command USB COM port is nothing but the serial port to which the ESP32-S2 chip is connected. see
In the command USB COM port is nothing but the serial port to which the ESP chip is connected. see
[check serial port](https://docs.espressif.com/projects/esp-idf/en/latest/esp32/get-started/establish-serial-connection.html#check-port-on-windows) for more details.
RSA private key is nothing but the client private key ( RSA ) generated in Step 2.
@ -99,7 +99,7 @@ DATA=data
### configure_ds.py
The script [configure_ds.py](./configure_ds.py) is used for configuring the DS peripheral on the ESP32-S2 SoC. The steps in the script are based on technical details of certain operations in the Digital Signature calculation, which can be found at Digital Signature Section of [ESP32-S2 TRM](https://www.espressif.com/sites/default/files/documentation/esp32-s2_technical_reference_manual_en.pdf)
The script [configure_ds.py](./configure_ds.py) is used for configuring the DS peripheral on the ESP32-S2/ESP32-C3 SoC. The steps in the script are based on technical details of certain operations in the Digital Signature calculation, which can be found at Digital Signature Section of [ESP32-S2 TRM](https://www.espressif.com/sites/default/files/documentation/esp32-s2_technical_reference_manual_en.pdf)
The configuration script performs the following steps -

50
examples/protocols/mqtt/ssl_ds/configure_ds.py
View File

@ -12,13 +12,14 @@
# See the License for the specific language governing permissions and
# limitations under the License.
import argparse
import os
import sys
import hashlib
import hmac
import json
import os
import struct
import subprocess
import json
import sys
from cryptography.hazmat.backends import default_backend
from cryptography.hazmat.primitives import serialization
from cryptography.hazmat.primitives.asymmetric import rsa
@ -45,7 +46,8 @@ csv_filename = esp_ds_data_dir + '/pre_prov.csv'
bin_filename = esp_ds_data_dir + '/pre_prov.bin'
expected_json_path = os.path.join('build', 'config', 'sdkconfig.json')
# Targets supported by the script
supported_targets = {'esp32s2'}
supported_targets = {'esp32s2', 'esp32c3'}
supported_key_size = {'esp32s2':[1024, 2048, 3072, 4096], 'esp32c3':[1024, 2048, 3072]}
# @return
@ -87,10 +89,11 @@ def number_as_bytes(number, pad_bits=None):
# privkey : path to the RSA private key
# priv_key_pass : path to the RSA privaete key password
# hmac_key : HMAC key value ( to calculate DS params)
# idf_target : The target chip for the script (e.g. esp32s2, esp32c3)
# @info
# The function calculates the encrypted private key parameters.
# Consult the DS documentation (available for the ESP32-S2) in the esp-idf programming guide for more details about the variables and calculations.
def calculate_ds_parameters(privkey, priv_key_pass, hmac_key):
def calculate_ds_parameters(privkey, priv_key_pass, hmac_key, idf_target):
private_key = load_privatekey(privkey, priv_key_pass)
if not isinstance(private_key, rsa.RSAPrivateKey):
print("ERROR: Only RSA private keys are supported")
@ -104,9 +107,9 @@ def calculate_ds_parameters(privkey, priv_key_pass, hmac_key):
Y = priv_numbers.d
M = pub_numbers.n
key_size = private_key.key_size
supported_key_size = [1024, 2048, 3072, 4096]
if key_size not in supported_key_size:
print("Key size not supported, supported sizes are" + str(supported_key_size))
if key_size not in supported_key_size[idf_target]:
print("ERROR: Private key size {0} not supported for the target {1},\nthe supported key sizes are {2}"
.format(key_size, idf_target, str(supported_key_size[idf_target])))
sys.exit(-1)
iv = os.urandom(16)
@ -117,25 +120,34 @@ def calculate_ds_parameters(privkey, priv_key_pass, hmac_key):
mprime &= 0xFFFFFFFF
length = key_size // 32 - 1
# get max supported key size for the respective target
max_len = max(supported_key_size[idf_target])
aes_key = hmac.HMAC(hmac_key, b"\xFF" * 32, hashlib.sha256).digest()
md_in = number_as_bytes(Y, 4096) + \
number_as_bytes(M, 4096) + \
number_as_bytes(rinv, 4096) + \
md_in = number_as_bytes(Y, max_len) + \
number_as_bytes(M, max_len) + \
number_as_bytes(rinv, max_len) + \
struct.pack("<II", mprime, length) + \
iv
assert len(md_in) == 12480 / 8
md = hashlib.sha256(md_in).digest()
# expected_len = max_len_Y + max_len_M + max_len_rinv + (mprime + length packed (8 bytes))+ iv (16 bytes)
expected_len = (max_len / 8) * 3 + 8 + 16
assert len(md_in) == expected_len
md = hashlib.sha256(md_in).digest()
# In case of ESP32-S2
# Y4096 || M4096 || Rb4096 || M_prime32 || LENGTH32 || MD256 || 0x08*8
p = number_as_bytes(Y, 4096) + \
number_as_bytes(M, 4096) + \
number_as_bytes(rinv, 4096) + \
# In case of ESP32-C3
# Y3072 || M3072 || Rb3072 || M_prime32 || LENGTH32 || MD256 || 0x08*8
p = number_as_bytes(Y, max_len) + \
number_as_bytes(M, max_len) + \
number_as_bytes(rinv, max_len) + \
md + \
struct.pack("<II", mprime, length) + \
b'\x08' * 8
assert len(p) == 12672 / 8
# expected_len = max_len_Y + max_len_M + max_len_rinv + md (32 bytes) + (mprime + length packed (8bytes)) + padding (8 bytes)
expected_len = (max_len / 8) * 3 + 32 + 8 + 8
assert len(p) == expected_len
cipher = Cipher(algorithms.AES(aes_key), modes.CBC(iv), backend=default_backend())
encryptor = cipher.encryptor()
@ -171,7 +183,7 @@ def efuse_burn_key(args, idf_target):
def generate_csv_file(c, iv, hmac_key_id, key_size, csv_file):
with open(csv_file, 'wt', encoding='utf8') as f:
f.write("# This is a generated csv file containing required parameters for the Digital Signature operaiton\n")
f.write("# This is a generated csv file containing required parameters for the Digital Signature operation\n")
f.write("key,type,encoding,value\nesp_ds_ns,namespace,,\n")
f.write("esp_ds_c,data,hex2bin,%s\n" % (c.hex()))
f.write("esp_ds_iv,data,hex2bin,%s\n" % (iv.hex()))
@ -371,7 +383,7 @@ def main():
sys.exit(-1)
# Calculate the encrypted private key data along with all other parameters
c, iv, key_size = calculate_ds_parameters(args.privkey, args.priv_key_pass, hmac_key_read)
c, iv, key_size = calculate_ds_parameters(args.privkey, args.priv_key_pass, hmac_key_read, idf_target)
# Generate csv file for the DS data and generate an NVS partition.
generate_csv_file(c, iv, args.efuse_key_id, key_size, csv_filename)

3
examples/protocols/mqtt/ssl_ds/main/CMakeLists.txt
View File

@ -1,2 +1,3 @@
idf_component_register(SRCS "app_main.c"
INCLUDE_DIRS ".")
INCLUDE_DIRS "."
REQUIRED_IDF_TARGETS esp32s2 esp32c3)

12
examples/protocols/mqtt/ssl_ds/main/app_main.c
View File

@ -117,40 +117,40 @@ void *esp_read_ds_data_from_nvs(void)
esp_err_t esp_ret;
esp_ret = nvs_flash_init_partition(NVS_PARTITION_NAME);
if (esp_ret != ESP_OK) {
ESP_LOGE(TAG, "Error in esp_ds_nvs partition init, returned %02x", esp_ret);
ESP_LOGE(TAG, "Error in esp_ds_nvs partition init,\nreturned %02x (%s)", esp_ret, esp_err_to_name(esp_ret));
goto exit;
}
esp_ret = nvs_open_from_partition(NVS_PARTITION_NAME, NVS_NAMESPACE,
NVS_READONLY, &esp_ds_nvs_handle);
if (esp_ret != ESP_OK) {
ESP_LOGE(TAG, "Error in esp_ds_nvs partition open, returned %02x", esp_ret);
ESP_LOGE(TAG, "Error in esp_ds_nvs partition open,\nreturned %02x (%s)", esp_ret, esp_err_to_name(esp_ret));
goto exit;
}
esp_ret = nvs_get_u8(esp_ds_nvs_handle, NVS_EFUSE_KEY_ID, &ds_data_ctx->efuse_key_id);
if (esp_ret != ESP_OK) {
ESP_LOGE(TAG, "Error in efuse_key_id value from nvs, returned %02x", esp_ret);
ESP_LOGE(TAG, "Error in efuse_key_id value from nvs,\nreturned %02x (%s)", esp_ret, esp_err_to_name(esp_ret));
goto exit;
}
esp_ret = nvs_get_u16(esp_ds_nvs_handle, NVS_RSA_LEN, &ds_data_ctx->rsa_length_bits);
if (esp_ret != ESP_OK) {
ESP_LOGE(TAG, "Error in reading rsa key length value from nvs, returned %02x", esp_ret);
ESP_LOGE(TAG, "Error in reading rsa key length value from nvs,\nreturned %02x (%s)", esp_ret, esp_err_to_name(esp_ret));
goto exit;
}
size_t blob_length = ESP_DS_C_LEN;
esp_ret = nvs_get_blob(esp_ds_nvs_handle, NVS_CIPHER_C, (void *)(ds_data_ctx->esp_ds_data->c), &blob_length);
if ((esp_ret != ESP_OK) || (blob_length != ESP_DS_C_LEN)) {
ESP_LOGE(TAG, "Error in reading initialization vector value from nvs,bytes_read = %d, returned %02x", blob_length, esp_ret);
ESP_LOGE(TAG, "Error in reading ciphertext_c value from nvs,bytes_read = %d,\nreturned %02x (%s)", blob_length, esp_ret, esp_err_to_name(esp_ret));
goto exit;
}
blob_length = ESP_DS_IV_LEN;
esp_ret = nvs_get_blob(esp_ds_nvs_handle, NVS_IV, (void *)(ds_data_ctx->esp_ds_data->iv), &blob_length);
if ((esp_ret != ESP_OK) || (blob_length != ESP_DS_IV_LEN)) {
ESP_LOGE(TAG, "Error in reading initialization vector value from nvs,bytes_read = %d, returned %02x", blob_length, esp_ret);
ESP_LOGE(TAG, "Error in reading initialization vector value from nvs,bytes_read = %d,\nreturned %02x (%s)", blob_length, esp_ret, esp_err_to_name(esp_ret));
goto exit;
}