esp32c3/Digital Signature: mbedtls integration through ESP-TLS

components/esp-tls/Kconfig

@@ -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

components/esp32c3/include/esp_ds.h

@@ -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

components/mbedtls/CMakeLists.txt

@@ -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.

components/mbedtls/port/esp_ds/esp_rsa_sign_alt.c

@@ -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"

components/mbedtls/port/include/rsa_sign_alt.h

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

examples/protocols/mqtt/ssl_ds/README.md

@@ -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 -
 

examples/protocols/mqtt/ssl_ds/configure_ds.py

@@ -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[idf_target]:
-    if key_size not in supported_key_size:
+        print("ERROR: Private key size {0} not supported for the target {1},\nthe supported key sizes are {2}"
-        print("Key size not supported, supported sizes are" + str(supported_key_size))
+              .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) + \
+    md_in = number_as_bytes(Y, max_len) + \
-        number_as_bytes(M, 4096) + \
+        number_as_bytes(M, max_len) + \
-        number_as_bytes(rinv, 4096) + \
+        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) + \
+    # In case of ESP32-C3
-        number_as_bytes(M, 4096) + \
+    # Y3072 || M3072 || Rb3072 || M_prime32 || LENGTH32 || MD256 || 0x08*8
-        number_as_bytes(rinv, 4096) + \
+    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)

examples/protocols/mqtt/ssl_ds/main/CMakeLists.txt

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

examples/protocols/mqtt/ssl_ds/main/app_main.c

@@ -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;
     }