Merge pull request #34 from zhen9910/patch-1

Create user-defined-ciphersuite.md

Author: liydu

README.md

@@ -40,3 +40,8 @@ The Azure RTOS and Azure Sphere better together sample can be found at:
 https://github.com/Azure-Samples/Azure-RTOS-on-Azure-Sphere-Mediatek-MT3620
 
 This sample demonstrates how Azure Sphere and Azure RTOS are able to run together on the MediaTek MT3620 Development Kit.
+
+## User-defined Crypto Ciphersuite
+
+This [guide](./user-defined-ciphersuite.md) demonstrates how to implement user-defined crypto ciphersuite and integrate it with Azure IoT Sample.
+

user-defined-ciphersuite.md

@@ -0,0 +1,73 @@
+# User-defined Crypto Ciphersuite Used by Azure IoT Sample
+
+## Introduction
+
+[Azure RTOS NetX Crypto](https://learn.microsoft.com/azure/rtos/netx/netx-crypto/chapter1) is the default crypto ciphersuite used by [Azure RTOS NetX Secure](https://learn.microsoft.com/azure/rtos/netx-duo/netx-secure-tls/chapter1) TLS stack in [Azure IoT Sample](https://github.com/azure-rtos/samples). If clients want to use different crypto algorithm implementation, such as hardware security engine, TF-M PSA, or PKCS#11 based crypto methods, this user guide will show how to implement user-defined crypto ciphersuite and integrate it with Azure IoT Sample.
+
+## General Process
+
+There are four steps to implement and utilize a user-defined crypto ciphersuite.
+
+1. Declare a [NX_CRYPTO_METHOD](https://github.com/azure-rtos/netxduo/blob/master/crypto_libraries/inc/nx_crypto.h#L320) struct for your crypto algorithm, which contains initialization, cleanup and crypto operations function pointers for the crypto method in use.
+
+2. Define initialization, cleanup and crypto operation functions for this crypto method.
+   
+3. Define a struct to save meta data such as scrtch buffer, algotithm id, etc, which will be passed into above functions as as input parameter.
+
+4. Add this newly defined `NX_CRYPTO_METHOD` into tls crypto array `_nx_azure_iot_tls_supported_crypto[]`, which will be automatically initialized during tls session creation and then utilized by NetX Secure TLS stack.
+
+## Example
+
+[The STMicroelectronics B-U585I-IOT02A sample project](https://github.com/azure-rtos/samples/releases/download/v6.1_rel/Azure_RTOS_6.1_B-U585I-IOT02A_IAR_Samples_Beta_2021_10_01.zip) implements [TF-M PSA](https://www.trustedfirmware.org/projects/tf-m/) based ECDSA crypto ciphersuite for TLS device authentication. We will use it an an example to demonstrate the above process.
+
+All the changed files are under the path *B-U585I-IOT02A\Projects\B-U585I-IOT02A\Applications\TFM\TFM_Appli\NonSecure\Projects\B-U585I-IOT02A\Applications\TFM\TFM_Appli\NonSecure*.
+
+1. In *psa_crypto_ciphersuites/nx_crypto_psa_crypto_ciphersuites.c*, declare NX_CRYPTO_METHOD struct `crypto_method_ecdsa_psa_crypto` for PSA based ECDSA crypto method.
+
+```c
+NX_CRYPTO_METHOD crypto_method_ecdsa_psa_crypto =
+{
+    NX_CRYPTO_DIGITAL_SIGNATURE_ECDSA,           /* ECDSA crypto algorithm   name     */
+    0,                                           /* Key size in bits                       */
+    0,                                           /* IV size in bits                        */
+    0,                                           /* ICV size in bits, not used             */
+    0,                                           /* Block size in bytes                    */
+    sizeof(NX_CRYPTO_ECDSA_PSA_CRYPTO),                 /* Metadata size in bytes                 */
+    _nx_crypto_method_ecdsa_psa_crypto_init,            /* ECDSA initialization routine           */
+    _nx_crypto_method_ecdsa_psa_crypto_cleanup,         /* ECDSA cleanup routine                  */
+    _nx_crypto_method_ecdsa_psa_crypto_operation,       /* ECDSA operation                        */
+};
+```
+
+2. In *psa_crypto_ciphersuites/nx_crypto_ecdsa_psa_crypto.c*, define initialization, cleanup and crypto operations for this crypto method.
+- `_nx_crypto_method_ecdsa_psa_crypto_init()` for parameter check and metadata initialization;
+- `_nx_crypto_method_ecdsa_psa_crypto_cleanup()` for metadata clean up;
+- `_nx_crypto_method_ecdsa_psa_crypto_operation()` to perform ECDSA operations, including ECDSA signature, verify, EC curve setting, with [PSA crypto APIs](https://armmbed.github.io/mbed-crypto/html/index.html).
+
+3. In *psa_crypto_ciphersuites/nx_crypto_ecdsa_psa_crypto.h*, define a struct `NX_CRYPTO_ECDSA_PSA_CRYPTO` to save metadata used by crypto functions, such as scrtch buffer, psa key handle, etc.
+
+4. In *Src/nx_azure_iot_ciphersuites.c*, add this newly defined NX_CRYPTO_METHOD `crypto_method_ecdsa_psa_crypto` into `_nx_azure_iot_tls_supported_crypto[]`.
+
+```c
+const NX_CRYPTO_METHOD *_nx_azure_iot_tls_supported_crypto[] =
+{
+    &crypto_method_hmac,
+    &crypto_method_hmac_sha256,
+    &crypto_method_tls_prf_sha256,
+    &crypto_method_sha256,
+    &crypto_method_aes_cbc_128,
+    &crypto_method_rsa,
+#ifdef NX_SECURE_ENABLE_ECC_CIPHERSUITE
+#ifdef ENABLE_PSA_CRYPTO_CIPHERSUITES
+    &crypto_method_ecdsa_psa_crypto,    /* PSA based ECDSA crypto method */
+#else
+    &crypto_method_ecdsa,
+#endif
+    &crypto_method_ecdhe,
+    &crypto_method_ec_secp384,
+    &crypto_method_ec_secp256,
+#endif /* NX_SECURE_ENABLE_ECC_CIPHERSUITE */
+};
+```
+
+With these changes, the user-defined PSA based ECDSA crypto method will be used by NX secure TLS stack in Azure IoT Sample.