Add hardware algo support for ESP32

This enables hardware support for AES,AES-GCM,SHA-256, and SHA-512 on
the ESP32 in the example program.

examples/esp32/CMakeLists.txt

@@ -6,3 +6,7 @@ cmake_minimum_required(VERSION 3.16)
 
 include($ENV{IDF_PATH}/tools/cmake/project.cmake)
 project(esp32-libmicrofido2)
+
+if (CONFIG_MBEDTLS_HARDWARE_AES STREQUAL "y")
+    idf_build_set_property(COMPILE_DEFINITIONS "-DUSE_HW_CRYPTO" APPEND)
+endif()

examples/esp32/README.md

@@ -16,3 +16,9 @@ A small ESP-IDF app for the ESP32 using the libmicrofido2.
 
 1. Connect the ESP32 to your computer and find its device node at `/dev/ttyUSBX` (note the value of `X` and replace it in the following command).
 1. Run `docker run --rm -v $PWD/../../:/project -w /project/examples/esp32 --device /dev/ttyUSBX espressif/idf idf.py flash`.
+
+## Hardware Cryptography
+
+By default, hardware accelerated AES, partially AES-GCM, SHA-256, and SHA-512 are enabled.
+As of now (2022), the ESP32C3 does not have hardware support for Ed25519.
+To disable these, set `CONFIG_USE_HW_CRYPTO=n` in your `sdkconfig`.

examples/esp32/main/CMakeLists.txt

@@ -1,5 +1,5 @@
 idf_component_register(
     SRCS "esp32-libmicrofido2.c"
     INCLUDE_DIRS "."
-    PRIV_REQUIRES libmicrofido2
+    PRIV_REQUIRES libmicrofido2 mbedtls
 )

examples/esp32/main/Kconfig.projbuild

@@ -0,0 +1,5 @@
+config USE_HW_CRYPTO
+	bool "Use hardware acceleration for cryptography and hashing"
+	default n
+	help
+		Decides whether FIDO operations will use hardware acceleration for cryptography and hashing (if possible)

examples/esp32/main/esp32-libmicrofido2.c

@@ -11,6 +11,114 @@
 #include <assert.h>
 #include <stdio.h>
 #include <string.h>
+#include <sdkconfig.h>
+
+#ifdef CONFIG_USE_HW_CRYPTO
+#include <mbedtls/aes.h>
+#include <mbedtls/gcm.h>
+#include <mbedtls/sha256.h>
+#include <mbedtls/sha512.h>
+#endif
+
+#ifdef CONFIG_USE_HW_CRYPTO
+int sha256(const uint8_t *data, size_t data_len, uint8_t *hash) {
+    int r = mbedtls_sha256(data, data_len, hash, 0);
+    if (r != 0) {
+        printf("sha256 failed with %d\n", r);
+    }
+    return r;
+}
+
+int sha512(const uint8_t *data, size_t data_len, uint8_t *hash) {
+    int r = mbedtls_sha512(data, data_len, hash, 0);
+    if (r != 0) {
+        printf("sha512 failed with %d\n", r);
+    }
+    return r;
+}
+
+int aes_gcm_encrypt(
+    const uint8_t *key, size_t key_len,
+    const uint8_t *iv, size_t iv_len,
+    const uint8_t *plaintext, size_t plaintext_len,
+    const uint8_t *aad, size_t aad_len,
+    uint8_t *ciphertext, uint8_t *tag
+) {
+    mbedtls_gcm_context ctx;
+    int r;
+
+    mbedtls_gcm_init(&ctx);
+
+    r = mbedtls_gcm_setkey(&ctx, MBEDTLS_CIPHER_ID_AES, key, key_len * 8);
+    if (r != 0) {
+        printf("[%s] mbedtls_gcm_setkey failed with %d\n", __func__, r);
+        return r;
+    }
+
+    r = mbedtls_gcm_crypt_and_tag(
+        &ctx,
+        MBEDTLS_ENCRYPT,
+        plaintext_len,
+        iv, iv_len,
+        aad, aad_len,
+        ciphertext, plaintext,
+        16, tag
+    );
+    if (r != 0) {
+        printf("[%s] mbedtls_gcm_crypt_and_tag failed with %d\n", __func__, r);
+        return r;
+    }
+
+    mbedtls_gcm_free(&ctx);
+
+    return 0;
+}
+
+int aes_gcm_decrypt(
+    const uint8_t *key, size_t key_len,
+    const uint8_t *iv, size_t iv_len,
+    const uint8_t *ciphertext, size_t ciphertext_len,
+    const uint8_t *aad, size_t aad_len,
+    const uint8_t *tag,
+    uint8_t *plaintext
+) {
+    mbedtls_gcm_context ctx;
+    int r;
+
+    mbedtls_gcm_init(&ctx);
+
+    r = mbedtls_gcm_setkey(&ctx, MBEDTLS_CIPHER_ID_AES, key, key_len * 8);
+    if (r != 0) {
+        printf("[%s] mbedtls_gcm_setkey failed with %d\n", __func__, r);
+        return r;
+    }
+
+    r = mbedtls_gcm_crypt_and_tag(
+        &ctx,
+        MBEDTLS_DECRYPT,
+        ciphertext_len,
+        iv, iv_len,
+        aad, aad_len,
+        ciphertext, plaintext,
+        16, tag
+    );
+    if (r != 0) {
+        printf("[%s] mbedtls_gcm_crypt_and_tag failed with %d\n", __func__, r);
+        return r;
+    }
+
+    mbedtls_gcm_free(&ctx);
+
+    return 0;
+}
+
+void init_crypto() {
+    fido_sha256 = &sha256;
+    fido_sha512 = &sha512;
+    fido_aes_gcm_encrypt = &aes_gcm_encrypt;
+    fido_aes_gcm_decrypt = &aes_gcm_decrypt;
+}
+#endif
 
 static void *example_open() {
     printf("open\n");
@@ -115,6 +223,10 @@ static const fido_dev_io_t nfc_io = {
 };
 
 int app_main(void) {
+    #ifdef CONFIG_USE_HW_CRYPTO
+    init_crypto();
+    #endif
+
     fido_dev_t dev;
     if (fido_init_nfc_device(&dev, &nfc_io) != FIDO_OK) {
         return 1;

examples/esp32/sdkconfig.defaults

@@ -4,3 +4,9 @@ CONFIG_ESP_MAIN_TASK_STACK_SIZE=10240
 # Set target to ESP32-C3
 CONFIG_IDF_TARGET="esp32c3"
 CONFIG_IDF_TARGET_ESP32C3=y
+
+# Enable HW support for crypto and hashing
+CONFIG_USE_HW_CRYPTO=y
+CONFIG_MBEDTLS_HARDWARE_AES=y
+CONFIG_MBEDTLS_HARDWARE_GCM=y
+CONFIG_MBEDTLS_HARDWARE_SHA=y