/** * Copyright (c) 2016 - 2020, Nordic Semiconductor ASA * * All rights reserved. * * Redistribution and use in source and binary forms, with or without modification, * are permitted provided that the following conditions are met: * * 1. Redistributions of source code must retain the above copyright notice, this * list of conditions and the following disclaimer. * * 2. Redistributions in binary form, except as embedded into a Nordic * Semiconductor ASA integrated circuit in a product or a software update for * such product, must reproduce the above copyright notice, this list of * conditions and the following disclaimer in the documentation and/or other * materials provided with the distribution. * * 3. Neither the name of Nordic Semiconductor ASA nor the names of its * contributors may be used to endorse or promote products derived from this * software without specific prior written permission. * * 4. This software, with or without modification, must only be used with a * Nordic Semiconductor ASA integrated circuit. * * 5. Any software provided in binary form under this license must not be reverse * engineered, decompiled, modified and/or disassembled. * * THIS SOFTWARE IS PROVIDED BY NORDIC SEMICONDUCTOR ASA "AS IS" AND ANY EXPRESS * OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES * OF MERCHANTABILITY, NONINFRINGEMENT, AND FITNESS FOR A PARTICULAR PURPOSE ARE * DISCLAIMED. IN NO EVENT SHALL NORDIC SEMICONDUCTOR ASA OR CONTRIBUTORS BE * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE * GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. * */ #include #include #include "es_security.h" #include "app_timer.h" #include "es_flash.h" #include "es_stopwatch.h" #include "fds.h" #include "modes.h" #include "nrf_crypto.h" #include "nrf_soc.h" #define NONCE_SIZE (6) #define TAG_SIZE (2) #define SALT_SIZE (2) #define TLM_DATA_SIZE (ES_TLM_LENGTH - 2) #define EIK_SIZE (ESCS_AES_KEY_SIZE) #define AES_ECB_CIPHERTEXT_LENGTH (16) #define AES_ECB_CLEARTEXT_LENGTH (16) /**@brief Timing structure. */ typedef struct { uint32_t time_counter; uint8_t k_scaler; } es_security_timing_t; /**@brief Security slot structure. */ typedef struct { nrf_ecb_hal_data_t aes_ecb_ik; nrf_ecb_hal_data_t aes_ecb_tk; uint8_t eid[ES_EID_ID_LENGTH]; es_security_timing_t timing; bool is_occupied; } es_security_slot_t; /**@brief Key pair structure. */ typedef struct { nrf_crypto_ecc_private_key_t private; nrf_crypto_ecc_public_key_t public; } ecdh_key_pair_t; /**@brief ECDH structure. */ typedef struct { ecdh_key_pair_t ecdh_key_pair; } es_security_ecdh_t; static nrf_ecb_hal_data_t m_aes_ecb_lk; static es_security_slot_t m_security_slot[APP_MAX_EID_SLOTS]; static es_security_ecdh_t m_ecdh; static es_security_msg_cb_t m_security_callback; static es_stopwatch_id_t m_seconds_passed_sw_id; // Use static context variables to avoid stack allocation. static nrf_crypto_aes_context_t m_aes_context; static nrf_crypto_hmac_context_t m_hmac_context; static nrf_crypto_aead_context_t m_aead_context; static nrf_crypto_ecc_key_pair_generate_context_t ecc_key_pair_generate_context; static nrf_crypto_ecdh_context_t ecdh_context; /**@brief Generates a temporary key with the Identity key. */ static void temp_key_generate(uint8_t slot_no); /**@brief Generates a EID with the Temporary Key*/ static void eid_generate(uint8_t slot_no) { ret_code_t err_code; size_t ciphertext_size = AES_ECB_CIPHERTEXT_LENGTH; temp_key_generate(slot_no); memset(m_security_slot[slot_no].aes_ecb_tk.cleartext, 0, ESCS_AES_KEY_SIZE); m_security_slot[slot_no].aes_ecb_tk.cleartext[11] = m_security_slot[slot_no].timing.k_scaler; uint32_t k_bits_cleared_time = (m_security_slot[slot_no].timing.time_counter >> m_security_slot[slot_no].timing.k_scaler) << m_security_slot[slot_no].timing.k_scaler; m_security_slot[slot_no].aes_ecb_tk.cleartext[12] = (uint8_t)((k_bits_cleared_time >> 24) & 0xff); m_security_slot[slot_no].aes_ecb_tk.cleartext[13] = (uint8_t)((k_bits_cleared_time >> 16) & 0xff); m_security_slot[slot_no].aes_ecb_tk.cleartext[14] = (uint8_t)((k_bits_cleared_time >> 8) & 0xff); m_security_slot[slot_no].aes_ecb_tk.cleartext[15] = (uint8_t)((k_bits_cleared_time) & 0xff); err_code = nrf_crypto_aes_crypt(&m_aes_context, &g_nrf_crypto_aes_ecb_128_info, NRF_CRYPTO_ENCRYPT, // Operation m_security_slot[slot_no].aes_ecb_tk.key, // Key NULL, // IV m_security_slot[slot_no].aes_ecb_tk.cleartext, // Data in AES_ECB_CLEARTEXT_LENGTH, // Data in size m_security_slot[slot_no].aes_ecb_tk.ciphertext, // Data out &ciphertext_size); // Data out size APP_ERROR_CHECK(err_code); memcpy(m_security_slot[slot_no].eid, m_security_slot[slot_no].aes_ecb_tk.ciphertext, ES_EID_ID_LENGTH); m_security_callback(slot_no, ES_SECURITY_MSG_EID); } /**@brief Generates a temporary key with the Identity key. */ static void temp_key_generate(uint8_t slot_no) { ret_code_t err_code; size_t ciphertext_size = AES_ECB_CIPHERTEXT_LENGTH; memset(m_security_slot[slot_no].aes_ecb_ik.cleartext, 0, ESCS_AES_KEY_SIZE); m_security_slot[slot_no].aes_ecb_ik.cleartext[11] = 0xFF; m_security_slot[slot_no].aes_ecb_ik.cleartext[14] = (uint8_t)((m_security_slot[slot_no].timing.time_counter >> 24) & 0xff); m_security_slot[slot_no].aes_ecb_ik.cleartext[15] = (uint8_t)((m_security_slot[slot_no].timing.time_counter >> 16) & 0xff); err_code = nrf_crypto_aes_crypt(&m_aes_context, &g_nrf_crypto_aes_ecb_128_info, NRF_CRYPTO_ENCRYPT, // Operation m_security_slot[slot_no].aes_ecb_ik.key, // Key NULL, // IV m_security_slot[slot_no].aes_ecb_ik.cleartext, // Data in AES_ECB_CLEARTEXT_LENGTH, // Data in size m_security_slot[slot_no].aes_ecb_ik.ciphertext, // Data out &ciphertext_size); // Data out size APP_ERROR_CHECK(err_code); memcpy(m_security_slot[slot_no].aes_ecb_tk.key, m_security_slot[slot_no].aes_ecb_ik.ciphertext, ESCS_AES_KEY_SIZE); } /**@brief See if EID should be re-calculated. */ static void check_rollovers_and_update_eid(uint8_t slot_no) { static uint32_t last_invocation_time_counter = 0; uint32_t scaler = 2 << (m_security_slot[slot_no].timing.k_scaler - 1); uint32_t diff; if (last_invocation_time_counter == 0) { last_invocation_time_counter = m_security_slot[slot_no].timing.time_counter; } diff = m_security_slot[slot_no].timing.time_counter - last_invocation_time_counter; if (diff >= scaler) { // Store to last scaler-aligned time. last_invocation_time_counter = (m_security_slot[slot_no].timing.time_counter / scaler) * scaler; eid_generate(slot_no); } } /**@brief Initialize lock code from flash. If it does not exist, copy from APP_CONFIG_LOCK_CODE. */ static void lock_code_init(uint8_t * p_lock_buff) { ret_code_t err_code; err_code = es_flash_access_lock_key(p_lock_buff, ES_FLASH_ACCESS_READ); FLASH_ACCES_ERROR_CHECK_ALLOW_NOT_FOUND(err_code); // If no lock keys exist, then generate one and copy it to buffer. if (err_code == FDS_ERR_NOT_FOUND) { uint8_t lock_code[16] = APP_CONFIG_LOCK_CODE; memcpy(p_lock_buff, lock_code, sizeof(lock_code)); err_code = es_flash_access_lock_key(p_lock_buff, ES_FLASH_ACCESS_WRITE); APP_ERROR_CHECK(err_code); } } void es_security_update_time(void) { static uint32_t timer_persist; uint32_t second_since_last_invocation = es_stopwatch_check(m_seconds_passed_sw_id); if (second_since_last_invocation > 0) { for (uint32_t i = 0; i < APP_MAX_EID_SLOTS; ++i) { if (m_security_slot[i].is_occupied) { m_security_slot[i].timing.time_counter += second_since_last_invocation; check_rollovers_and_update_eid(i); } } // Every 24 hr, write the new EID timer to flash. timer_persist += second_since_last_invocation; const uint32_t TWENTY_FOUR_HOURS = 60 * 60 * 24; if (timer_persist >= TWENTY_FOUR_HOURS) { for (uint32_t i = 0; i < APP_MAX_EID_SLOTS; ++i) { if (m_security_slot[i].is_occupied) { m_security_callback(i, ES_SECURITY_MSG_STORE_TIME); } } timer_persist = 0; } } } void es_security_eid_slots_restore(uint8_t slot_no, uint8_t k_scaler, uint32_t time_counter, const uint8_t * p_ik) { m_security_slot[slot_no].timing.k_scaler = k_scaler; m_security_slot[slot_no].timing.time_counter = time_counter; memcpy(m_security_slot[slot_no].aes_ecb_ik.key, p_ik, ESCS_AES_KEY_SIZE); m_security_slot[slot_no].is_occupied = true; m_security_callback(slot_no, ES_SECURITY_MSG_IK); eid_generate(slot_no); } ret_code_t es_security_lock_code_update(uint8_t * p_ecrypted_key) { ret_code_t err_code; uint8_t temp_buff[ESCS_AES_KEY_SIZE] = {0}; size_t temp_buff_size = sizeof(temp_buff); err_code = nrf_crypto_aes_crypt(&m_aes_context, &g_nrf_crypto_aes_ecb_128_info, NRF_CRYPTO_DECRYPT, // Operation m_aes_ecb_lk.key, // Key NULL, // IV p_ecrypted_key, // Data in 16, // Data in size temp_buff, // Data out &temp_buff_size); // Data out size VERIFY_SUCCESS(err_code); memcpy(m_aes_ecb_lk.key, temp_buff, ESCS_AES_KEY_SIZE); return es_flash_access_lock_key(m_aes_ecb_lk.key, ES_FLASH_ACCESS_WRITE); } void es_security_unlock_prepare(uint8_t * p_challenge) { ret_code_t err_code; size_t ciphertext_size = AES_ECB_CIPHERTEXT_LENGTH; memcpy(m_aes_ecb_lk.cleartext, p_challenge, ESCS_AES_KEY_SIZE); err_code = nrf_crypto_aes_crypt(&m_aes_context, &g_nrf_crypto_aes_ecb_128_info, NRF_CRYPTO_ENCRYPT, // Operation m_aes_ecb_lk.key, // Key NULL, // IV m_aes_ecb_lk.cleartext, // Data in AES_ECB_CLEARTEXT_LENGTH, // Data in size m_aes_ecb_lk.ciphertext, // Data out &ciphertext_size); // Data out size APP_ERROR_CHECK(err_code); } void es_security_unlock_verify(uint8_t * p_unlock_token) { if (memcmp(p_unlock_token, m_aes_ecb_lk.ciphertext, ESCS_AES_KEY_SIZE) == 0) { m_security_callback(0, ES_SECURITY_MSG_UNLOCKED); } } ret_code_t es_security_random_challenge_generate(uint8_t * p_rand_chlg_buff) { return nrf_crypto_rng_vector_generate(p_rand_chlg_buff, ESCS_AES_KEY_SIZE); } void es_security_shared_ik_receive(uint8_t slot_no, uint8_t * p_encrypted_ik, uint8_t scaler_k) { ret_code_t err_code; size_t cleartext_size = AES_ECB_CLEARTEXT_LENGTH; m_security_slot[slot_no].is_occupied = true; m_security_slot[slot_no].timing.k_scaler = scaler_k; m_security_slot[slot_no].timing.time_counter = APP_CONFIG_TIMING_INIT_VALUE; err_code = nrf_crypto_aes_crypt(&m_aes_context, &g_nrf_crypto_aes_ecb_128_info, NRF_CRYPTO_DECRYPT, // Operation m_aes_ecb_lk.key, // Key NULL, // IV p_encrypted_ik, // Data in 16, // Data in size m_security_slot[slot_no].aes_ecb_ik.key, // Data out &cleartext_size); // Data out size APP_ERROR_CHECK(err_code); eid_generate(slot_no); m_security_callback(slot_no, ES_SECURITY_MSG_IK); } void es_security_client_pub_ecdh_receive(uint8_t slot_no, uint8_t * p_pub_ecdh, uint8_t scaler_k) { ret_code_t err_code; nrf_crypto_ecc_public_key_t phone_public; // Phone public ECDH key uint8_t beacon_public[ESCS_ECDH_KEY_SIZE]; // Beacon public ECDH key uint8_t shared[ESCS_ECDH_KEY_SIZE]; // Shared secret ECDH key uint8_t public_keys[64]; // Buffer for concatenated public keys uint8_t key_material[64]; // Buffer for holding key material uint8_t empty_check[ESCS_ECDH_KEY_SIZE] = {0}; size_t beacon_public_size = sizeof(beacon_public); size_t shared_size = sizeof(shared); size_t key_material_size = sizeof(key_material); m_security_slot[slot_no].is_occupied = true; m_security_slot[slot_no].timing.k_scaler = scaler_k; m_security_slot[slot_no].timing.time_counter = APP_CONFIG_TIMING_INIT_VALUE; // Get public 32-byte service ECDH key from phone. err_code = nrf_crypto_ecc_public_key_from_raw(&g_nrf_crypto_ecc_curve25519_curve_info, &phone_public, p_pub_ecdh, ESCS_ECDH_KEY_SIZE); APP_ERROR_CHECK(err_code); // Generate key pair. err_code = nrf_crypto_ecc_key_pair_generate(&ecc_key_pair_generate_context, &g_nrf_crypto_ecc_curve25519_curve_info, &m_ecdh.ecdh_key_pair.private, &m_ecdh.ecdh_key_pair.public); APP_ERROR_CHECK(err_code); // Generate shared 32-byte ECDH secret from beacon private service ECDH key and phone public ECDH key. err_code = nrf_crypto_ecdh_compute(&ecdh_context, &m_ecdh.ecdh_key_pair.private, &phone_public, shared, &shared_size); APP_ERROR_CHECK(err_code); // Verify that the shared secret is not zero at this point, and report an error/reset if it is. if (memcmp(empty_check, shared, ESCS_ECDH_KEY_SIZE) == 0) { APP_ERROR_CHECK(NRF_ERROR_INTERNAL); } // Concatenate the resolver's public key and beacon's public key err_code = nrf_crypto_ecc_public_key_to_raw(&m_ecdh.ecdh_key_pair.public, beacon_public, &beacon_public_size); APP_ERROR_CHECK(err_code); memcpy(public_keys, p_pub_ecdh, 32); memcpy(public_keys + 32, beacon_public, 32); // Convert the shared secret to key material using HKDF-SHA256. HKDF is used with the salt set // to a concatenation of the resolver's public key and beacon's public key err_code = nrf_crypto_hkdf_calculate(&m_hmac_context, &g_nrf_crypto_hmac_sha256_info, key_material, // Output key &key_material_size, // Output key size shared, // Input key sizeof(shared), // Input key size public_keys, // Salt sizeof(public_keys), // Salt size NULL, // Additional info 0, // Additional info size NRF_CRYPTO_HKDF_EXTRACT_AND_EXPAND); // Mode APP_ERROR_CHECK(err_code); // Truncate the key material to 128 bits to convert it to an AES-128 secret key (Identity key). memcpy(m_security_slot[slot_no].aes_ecb_ik.key, key_material, ESCS_AES_KEY_SIZE); eid_generate(slot_no); m_security_callback(slot_no, ES_SECURITY_MSG_ECDH); m_security_callback(slot_no, ES_SECURITY_MSG_IK); } void es_security_pub_ecdh_get(uint8_t slot_no, uint8_t * p_edch_buffer) { ret_code_t err_code; size_t buffer_size = ESCS_ECDH_KEY_SIZE; err_code = nrf_crypto_ecc_public_key_to_raw(&m_ecdh.ecdh_key_pair.public, p_edch_buffer, &buffer_size); APP_ERROR_CHECK(err_code); } uint32_t es_security_clock_get(uint8_t slot_no) { return m_security_slot[slot_no].timing.time_counter; } void es_security_eid_slot_destroy(uint8_t slot_no) { memset(&m_security_slot[slot_no], 0, sizeof(es_security_slot_t)); } uint8_t es_security_scaler_get(uint8_t slot_no) { return m_security_slot[slot_no].timing.k_scaler; } void es_security_eid_get(uint8_t slot_no, uint8_t * p_eid_buffer) { memcpy(p_eid_buffer, m_security_slot[slot_no].eid, ES_EID_ID_LENGTH); } void es_security_encrypted_eid_id_key_get(uint8_t slot_no, uint8_t * p_key_buffer) { ret_code_t err_code; size_t ciphertext_size = AES_ECB_CIPHERTEXT_LENGTH; memcpy(m_aes_ecb_lk.cleartext, m_security_slot[slot_no].aes_ecb_ik.key, ESCS_AES_KEY_SIZE); err_code = nrf_crypto_aes_crypt(&m_aes_context, &g_nrf_crypto_aes_ecb_128_info, NRF_CRYPTO_ENCRYPT, // Operation m_aes_ecb_lk.key, // Key NULL, // IV m_aes_ecb_lk.cleartext, // Data in AES_ECB_CLEARTEXT_LENGTH, // Data in size m_aes_ecb_lk.ciphertext, // Data out &ciphertext_size); // Data out size APP_ERROR_CHECK(err_code); memcpy(p_key_buffer, m_aes_ecb_lk.ciphertext, ESCS_AES_KEY_SIZE); } void es_security_plain_eid_id_key_get(uint8_t slot_no, uint8_t * p_key_buffer) { memcpy(p_key_buffer, m_security_slot[slot_no].aes_ecb_ik.key, ESCS_AES_KEY_SIZE); } void es_security_tlm_to_etlm(uint8_t ik_slot_no, es_tlm_frame_t * p_tlm, es_etlm_frame_t * p_etlm) { ret_code_t err_code; uint8_t plain[TLM_DATA_SIZE] = {0}; // Plaintext tlm, without the frame byte and version. size_t nplain = TLM_DATA_SIZE; // Length of message plaintext. /*lint -save -e420 */ memcpy(plain, &p_tlm->vbatt[0], sizeof(plain)); uint8_t key[EIK_SIZE] = {0}; // Encryption/decryption key: EIK. memcpy(key, &m_security_slot[ik_slot_no].aes_ecb_ik.key[0], EIK_SIZE); /*lint -restore */ uint8_t nonce[NONCE_SIZE] = {0}; // Nonce. This must not repeat for a given key. size_t nnonce = NONCE_SIZE; // Length of nonce.First 4 bytes are beacon time base with k-bits cleared. // Last two bits are randomly generated // Take the current timestamp and clear the lowest K bits, use it as nonce. uint32_t k_bits_cleared_time = (m_security_slot[ik_slot_no].timing.time_counter >> m_security_slot[ik_slot_no].timing.k_scaler) << m_security_slot[ik_slot_no].timing.k_scaler; nonce[0] = (uint8_t)((k_bits_cleared_time >> 24) & 0xff); nonce[1] = (uint8_t)((k_bits_cleared_time >> 16) & 0xff); nonce[2] = (uint8_t)((k_bits_cleared_time >> 8) & 0xff); nonce[3] = (uint8_t)((k_bits_cleared_time) & 0xff); // Generate random salt. uint8_t salt[SALT_SIZE] = {0}; err_code = nrf_crypto_rng_vector_generate(salt, SALT_SIZE); APP_ERROR_CHECK(err_code); memcpy(&nonce[4], salt, SALT_SIZE); uint8_t cipher[ES_ETLM_ECRYPTED_LENGTH]; // Ciphertext output. nplain bytes are written. uint8_t tag[TAG_SIZE] = {0}; // Authentication tag. ntag bytes are written. size_t ntag = TAG_SIZE; // Length of authentication tag. // Encryption // -------------------------------------------------------------------------- err_code = nrf_crypto_aead_init(&m_aead_context, &g_nrf_crypto_aes_eax_128_info, key); APP_ERROR_CHECK(err_code); err_code = nrf_crypto_aead_crypt(&m_aead_context, NRF_CRYPTO_ENCRYPT, // Operation nonce, // Nonce nnonce, // Nonce size NULL, // Additional authenticated data (adata) 0, // Additional authenticated data size plain, // Input data nplain, // Input data size cipher, // Output data tag, // MAC result output ntag); // MAC size APP_ERROR_CHECK(err_code); err_code = nrf_crypto_aead_uninit(&m_aead_context); APP_ERROR_CHECK(err_code); // Construct the eTLM. // -------------------------------------------------------------------------- p_etlm->frame_type = p_tlm->frame_type; p_etlm->version = ES_TLM_VERSION_ETLM; memcpy(p_etlm->encrypted_tlm, cipher, ES_ETLM_ECRYPTED_LENGTH); memcpy((uint8_t *)&p_etlm->random_salt, salt, SALT_SIZE); memcpy((uint8_t *)&p_etlm->msg_integrity_check, tag, TAG_SIZE); } ret_code_t es_security_init(es_security_msg_cb_t security_callback) { ret_code_t err_code; if (security_callback == NULL) { return NRF_ERROR_INVALID_PARAM; } // Get lock code from 'es_app_config.h', or fetch it from flash if exists. lock_code_init(m_aes_ecb_lk.key); m_security_callback = security_callback; memset(&m_ecdh, 0, sizeof(es_security_ecdh_t)); for (uint32_t i = 0; i < APP_MAX_EID_SLOTS; ++i) { m_security_slot[i].timing.time_counter = APP_CONFIG_TIMING_INIT_VALUE; } err_code = es_stopwatch_create(&m_seconds_passed_sw_id, APP_TIMER_TICKS(1000)); APP_ERROR_CHECK(err_code); err_code = nrf_crypto_init(); APP_ERROR_CHECK(err_code); return NRF_SUCCESS; }