feat(esp_tee): Added support for PBKDF2-based (HMAC) ECDSA signing

components/mbedtls/CMakeLists.txt

@@ -280,6 +280,10 @@ target_sources(mbedcrypto PRIVATE
                 "${COMPONENT_DIR}/port/esp_ds/esp_ds_common.c")
 endif()
 
+if(CONFIG_SOC_HMAC_SUPPORTED)
+    target_sources(mbedcrypto PRIVATE "${COMPONENT_DIR}/port/esp_hmac_pbkdf2.c")
+endif()
+
 # Note: some mbedTLS hardware acceleration can be enabled/disabled by config.
 #
 # We don't need to filter aes.c as this uses a different prefix (esp_aes_x) and the

components/mbedtls/esp_tee/esp_tee_mbedtls.cmake

@@ -65,3 +65,6 @@ target_sources(mbedcrypto PRIVATE "${COMPONENT_DIR}/port/sha/core/sha.c"
 
 target_sources(mbedcrypto PRIVATE "${COMPONENT_DIR}/port/ecc/esp_ecc.c"
                                   "${COMPONENT_DIR}/port/ecc/ecc_alt.c")
+
+# HMAC-based PBKDF2 implementation
+target_sources(mbedcrypto PRIVATE "${COMPONENT_DIR}/port/esp_hmac_pbkdf2.c")

components/mbedtls/port/esp_hmac_pbkdf2.c

@@ -0,0 +1,82 @@
+/*
+ * SPDX-FileCopyrightText: 2025 Espressif Systems (Shanghai) CO LTD
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ */
+
+#include <string.h>
+#include "esp_hmac.h"
+#include "sdkconfig.h"
+
+#include "esp_hmac_pbkdf2.h"
+
+#define SHA256_DIGEST_SZ        32
+
+esp_err_t esp_hmac_derive_pbkdf2_key(hmac_key_id_t key_id, const uint8_t *salt, size_t salt_len, int iterations, size_t key_len, uint8_t *out_key)
+{
+    if (!out_key || !salt || key_len == 0 || salt_len == 0 || iterations <= 0) {
+        return ESP_ERR_INVALID_ARG;
+    }
+
+    if (key_id >= HMAC_KEY_MAX) {
+        return ESP_ERR_INVALID_ARG;
+    }
+
+    uint8_t U[SHA256_DIGEST_SZ] = {0};
+    uint8_t T[SHA256_DIGEST_SZ] = {0};
+    uint8_t counter[4] = {0, 0, 0, 1};
+
+    uint8_t *hmac_input = calloc(1, salt_len + sizeof(counter));
+    if (!hmac_input) {
+        return ESP_ERR_NO_MEM;
+    }
+
+    esp_err_t err = ESP_FAIL;
+    size_t remaining = key_len;
+    uint8_t *out_p = out_key;
+
+    while (remaining > 0) {
+        memcpy(hmac_input, salt, salt_len);
+        memcpy(hmac_input + salt_len, counter, sizeof(counter));
+
+        err = esp_hmac_calculate(key_id, hmac_input, salt_len + sizeof(counter), U);
+        if (err != ESP_OK) {
+            goto cleanup;
+        }
+
+        memcpy(T, U, SHA256_DIGEST_SZ);
+        for (int i = 1; i < iterations; i++) {
+            err = esp_hmac_calculate(key_id, U, SHA256_DIGEST_SZ, U);
+            if (err != ESP_OK) {
+                goto cleanup;
+            }
+
+            for (int j = 0; j < SHA256_DIGEST_SZ; j++) {
+                T[j] ^= U[j];
+            }
+        }
+
+        size_t copy_len = (remaining < SHA256_DIGEST_SZ) ? remaining : SHA256_DIGEST_SZ;
+        memcpy(out_p, T, copy_len);
+        out_p += copy_len;
+        remaining -= copy_len;
+
+        for (int i = 3; i >= 0; i--) {
+            if (++counter[i]) {
+                break;
+            }
+        }
+    }
+
+    err = ESP_OK;
+
+cleanup:
+    memset(U, 0x00, sizeof(U));
+    memset(T, 0x00, sizeof(T));
+    if (hmac_input) {
+        memset(hmac_input, 0x00, salt_len + sizeof(counter));
+        free(hmac_input);
+    }
+    return err;
+}

components/mbedtls/port/include/esp_hmac_pbkdf2.h

@@ -0,0 +1,41 @@
+/*
+ * SPDX-FileCopyrightText: 2025 Espressif Systems (Shanghai) CO LTD
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#pragma once
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#include <stdint.h>
+#include "esp_err.h"
+#include "hal/hmac_types.h"
+
+/**
+ * @brief Derive a key using PBKDF2-HMAC-SHA256 algorithm with HMAC peripheral
+ *
+ * This function implements PBKDF2 (Password-Based Key Derivation Function 2) using HMAC-SHA256
+ * to derive a cryptographic key from the efuse key and salt. The function uses the HMAC peripheral
+ * in upstream mode to perform the underlying HMAC calculations.
+ *
+ * @param key_id Determines which of the 6 key blocks in the efuses should be used as the base key.
+ *               The corresponding purpose field of the key block must be set to HMAC upstream purpose.
+ * @param salt Input salt for the PBKDF2 algorithm
+ * @param salt_len Length of the salt in bytes (must be > 0)
+ * @param iterations Number of iterations (recommended >= 2048)
+ * @param key_len Length of the derived key to generate in bytes (must be > 0)
+ * @param[out] out_key Buffer to store the derived key. Must be at least key_len bytes.
+ * @return esp_err_t
+ *         - ESP_OK: Key derivation successful
+ *         - ESP_ERR_INVALID_ARG: Invalid arguments (null pointers, zero lengths, or key_id out of range)
+ *         - ESP_ERR_NO_MEM: Memory allocation failed
+ *         - ESP_FAIL: HMAC calculation failed
+ */
+esp_err_t esp_hmac_derive_pbkdf2_key(hmac_key_id_t key_id, const uint8_t *salt, size_t salt_len, int iterations, size_t key_len, uint8_t *out_key);
+
+#ifdef __cplusplus
+}
+#endif