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Merge pull request #398 from tropicsquare/ETR01SDK-337-Add-openssl-crypto-backend
ETR01SDK-337: Add OpenSSL crypto backend
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‎CHANGELOG.md‎

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@@ -24,6 +24,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
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- ESP-IDF HAL for Espressif SoCs.
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- Missing secure memory zeroing to `lt_in__session_start()` and `lt_hkdf()` (internal function).
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- Missing check of `lt_handle_t.l3.session_status` in `lt_in__ecc_key_generate()`.
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- CAL: support for OpenSSL.
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### Fixed
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- `lt_print_bytes` function now returns `LT_PARAM_ERR` when incorrect parameters are passed instead of `LT_FAIL`.

‎cal/openssl/CMakeLists.txt‎

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cmake_minimum_required(VERSION 3.21.0)
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set(LT_CAL_SRCS
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${CMAKE_CURRENT_SOURCE_DIR}/lt_openssl_common.c
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${CMAKE_CURRENT_SOURCE_DIR}/lt_openssl_aesgcm.c
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${CMAKE_CURRENT_SOURCE_DIR}/lt_openssl_sha256.c
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${CMAKE_CURRENT_SOURCE_DIR}/lt_openssl_hmac_sha256.c
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${CMAKE_CURRENT_SOURCE_DIR}/lt_openssl_x25519.c
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)
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set(LT_CAL_INC_DIRS
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${CMAKE_CURRENT_SOURCE_DIR}
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)
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# export generic names for parent to consume
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set(LT_CAL_SRCS ${LT_CAL_SRCS} PARENT_SCOPE)
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set(LT_CAL_INC_DIRS ${LT_CAL_INC_DIRS} PARENT_SCOPE)

‎cal/openssl/libtropic_openssl.h‎

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#ifndef LT_OPENSSL_H
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#define LT_OPENSSL_H
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/**
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* @file lt_openssl.h
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* @brief OpenSSL public declarations.
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* @copyright Copyright (c) 2020-2025 Tropic Square s.r.o.
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*
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* @license For the license see LICENSE.md in the root directory of this source tree.
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*/
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#include <openssl/evp.h>
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/**
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* @brief Context structure for OpenSSL.
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*
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*/
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typedef struct lt_ctx_openssl_t {
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/** @private @brief AES-GCM context for encryption. */
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EVP_CIPHER_CTX *aesgcm_encrypt_ctx;
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/** @private @brief AES-GCM context for decryption. */
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EVP_CIPHER_CTX *aesgcm_decrypt_ctx;
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/** @private @brief SHA-256 context. */
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EVP_MD_CTX *sha256_ctx;
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} lt_ctx_openssl_t;
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#endif // LT_OPENSSL_H

‎cal/openssl/lt_openssl_aesgcm.c‎

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/**
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* @file lt_openssl_aesgcm.c
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* @copyright Copyright (c) 2020-2025 Tropic Square s.r.o.
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*
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* @license For the license see LICENSE.md in the root directory of this source tree.
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*/
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#include <inttypes.h>
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#include <openssl/err.h>
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#include <openssl/evp.h>
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#include <stdint.h>
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#include <stdlib.h>
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#include <string.h>
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#include "libtropic_common.h"
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#include "libtropic_logging.h"
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#include "libtropic_openssl.h"
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#include "lt_aesgcm.h"
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lt_ret_t lt_aesgcm_encrypt_init(void *ctx, const uint8_t *key, const uint32_t key_len)
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{
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if (key_len != TR01_AES256_KEY_LEN) {
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LT_LOG_ERROR("Invalid AES-GCM key length: got %" PRIu32 " bytes, expected %d bytes", key_len,
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TR01_AES256_KEY_LEN);
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return LT_PARAM_ERR;
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}
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lt_ctx_openssl_t *_ctx = (lt_ctx_openssl_t *)ctx;
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unsigned long err_code;
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// Initialize AES-GCM encryption context.
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_ctx->aesgcm_encrypt_ctx = EVP_CIPHER_CTX_new();
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if (!_ctx->aesgcm_encrypt_ctx) {
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err_code = ERR_get_error();
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LT_LOG_ERROR("Failed to allocate AES-GCM encryption context, err_code=%lu (%s)", err_code,
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ERR_error_string(err_code, NULL));
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return LT_CRYPTO_ERR;
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}
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// Set cipher type.
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if (!EVP_EncryptInit_ex(_ctx->aesgcm_encrypt_ctx, EVP_aes_256_gcm(), NULL, NULL, NULL)) {
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err_code = ERR_get_error();
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LT_LOG_ERROR("Failed to initialize AES-GCM encryption context with cipher type, err_code=%lu (%s)", err_code,
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ERR_error_string(err_code, NULL));
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return LT_CRYPTO_ERR;
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}
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// Set IV length.
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if (!EVP_CIPHER_CTX_ctrl(_ctx->aesgcm_encrypt_ctx, EVP_CTRL_GCM_SET_IVLEN, TR01_L3_IV_SIZE, NULL)) {
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err_code = ERR_get_error();
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LT_LOG_ERROR("Failed to initialize AES-GCM encryption context with IV length, err_code=%lu (%s)", err_code,
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ERR_error_string(err_code, NULL));
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return LT_CRYPTO_ERR;
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}
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// Set encryption key.
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if (!EVP_EncryptInit_ex(_ctx->aesgcm_encrypt_ctx, NULL, NULL, key, NULL)) {
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err_code = ERR_get_error();
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LT_LOG_ERROR("Failed to initialize AES-GCM encryption context with key, err_code=%lu (%s)", err_code,
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ERR_error_string(err_code, NULL));
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return LT_CRYPTO_ERR;
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}
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return LT_OK;
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}
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lt_ret_t lt_aesgcm_decrypt_init(void *ctx, const uint8_t *key, const uint32_t key_len)
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{
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if (key_len != TR01_AES256_KEY_LEN) {
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LT_LOG_ERROR("Invalid AES-GCM key length: got %" PRIu32 " bytes, expected %d bytes", key_len,
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TR01_AES256_KEY_LEN);
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return LT_PARAM_ERR;
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}
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lt_ctx_openssl_t *_ctx = (lt_ctx_openssl_t *)ctx;
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unsigned long err_code;
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// Initialize AES-GCM decryption context.
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_ctx->aesgcm_decrypt_ctx = EVP_CIPHER_CTX_new();
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if (!_ctx->aesgcm_decrypt_ctx) {
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err_code = ERR_get_error();
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LT_LOG_ERROR("Failed to allocate AES-GCM decryption context, err_code=%lu (%s)", err_code,
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ERR_error_string(err_code, NULL));
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return LT_CRYPTO_ERR;
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}
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// Set cipher type.
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if (!EVP_DecryptInit_ex(_ctx->aesgcm_decrypt_ctx, EVP_aes_256_gcm(), NULL, NULL, NULL)) {
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err_code = ERR_get_error();
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LT_LOG_ERROR("Failed to initialize AES-GCM decryption context with cipher type, err_code=%lu (%s)", err_code,
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ERR_error_string(err_code, NULL));
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return LT_CRYPTO_ERR;
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}
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// Set IV length.
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if (!EVP_CIPHER_CTX_ctrl(_ctx->aesgcm_decrypt_ctx, EVP_CTRL_GCM_SET_IVLEN, TR01_L3_IV_SIZE, NULL)) {
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err_code = ERR_get_error();
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LT_LOG_ERROR("Failed to initialize AES-GCM decryption context with IV length, err_code=%lu (%s)", err_code,
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ERR_error_string(err_code, NULL));
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return LT_CRYPTO_ERR;
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}
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// Set decryption key.
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if (!EVP_DecryptInit_ex(_ctx->aesgcm_decrypt_ctx, NULL, NULL, key, NULL)) {
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err_code = ERR_get_error();
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LT_LOG_ERROR("Failed to initialize AES-GCM decryption context with key, err_code=%lu (%s)", err_code,
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ERR_error_string(err_code, NULL));
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return LT_CRYPTO_ERR;
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}
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return LT_OK;
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}
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lt_ret_t lt_aesgcm_encrypt(void *ctx, const uint8_t *iv, const uint32_t iv_len, const uint8_t *add,
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const uint32_t add_len, const uint8_t *plaintext, const uint32_t plaintext_len,
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uint8_t *ciphertext, const uint32_t ciphertext_len)
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{
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if (iv_len != TR01_L3_IV_SIZE) {
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LT_LOG_ERROR("Invalid AES-GCM IV length: got %" PRIu32 " bytes, expected %d bytes", iv_len, TR01_L3_IV_SIZE);
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return LT_PARAM_ERR;
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}
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lt_ctx_openssl_t *_ctx = (lt_ctx_openssl_t *)ctx;
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unsigned long err_code;
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int out_len;
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// Set IV.
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if (!EVP_EncryptInit_ex(_ctx->aesgcm_encrypt_ctx, NULL, NULL, NULL, iv)) {
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err_code = ERR_get_error();
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LT_LOG_ERROR("Failed to set AES-GCM encryption IV, err_code=%lu (%s)", err_code,
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ERR_error_string(err_code, NULL));
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return LT_CRYPTO_ERR;
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}
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// Process AAD (Additional Authenticated Data).
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if (!EVP_EncryptUpdate(_ctx->aesgcm_encrypt_ctx, NULL, &out_len, add, (int)add_len)) {
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err_code = ERR_get_error();
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LT_LOG_ERROR("Failed to process AES-GCM AAD, err_code=%lu (%s)", err_code, ERR_error_string(err_code, NULL));
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return LT_CRYPTO_ERR;
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}
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// Encrypt plaintext.
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if (!EVP_EncryptUpdate(_ctx->aesgcm_encrypt_ctx, ciphertext, &out_len, plaintext, (int)plaintext_len)) {
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err_code = ERR_get_error();
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LT_LOG_ERROR("Failed to encrypt AES-GCM plaintext, err_code=%lu (%s)", err_code,
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ERR_error_string(err_code, NULL));
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return LT_CRYPTO_ERR;
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}
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// Check that all plaintext data was processed.
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if (out_len != (int)(ciphertext_len - TR01_L3_TAG_SIZE)) {
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LT_LOG_ERROR("AES-GCM encryption length mismatch! Current: %d bytes, expected: %" PRIu32 " bytes", out_len,
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ciphertext_len - TR01_L3_TAG_SIZE);
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return LT_CRYPTO_ERR;
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}
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// Finalize encryption.
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if (!EVP_EncryptFinal_ex(_ctx->aesgcm_encrypt_ctx, ciphertext + out_len, &out_len)) {
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err_code = ERR_get_error();
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LT_LOG_ERROR("Failed to finalize AES-GCM encryption, err_code=%lu (%s)", err_code,
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ERR_error_string(err_code, NULL));
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return LT_CRYPTO_ERR;
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}
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// Get the tag.
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if (!EVP_CIPHER_CTX_ctrl(_ctx->aesgcm_encrypt_ctx, EVP_CTRL_GCM_GET_TAG, TR01_L3_TAG_SIZE,
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ciphertext + plaintext_len)) {
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err_code = ERR_get_error();
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LT_LOG_ERROR("Failed to get AES-GCM encryption tag, err_code=%lu (%s)", err_code,
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ERR_error_string(err_code, NULL));
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return LT_CRYPTO_ERR;
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}
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return LT_OK;
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}
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lt_ret_t lt_aesgcm_decrypt(void *ctx, const uint8_t *iv, const uint32_t iv_len, const uint8_t *add,
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const uint32_t add_len, const uint8_t *ciphertext, const uint32_t ciphertext_len,
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uint8_t *plaintext, const uint32_t plaintext_len)
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{
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if (iv_len != TR01_L3_IV_SIZE) {
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LT_LOG_ERROR("Invalid AES-GCM IV length: got %" PRIu32 " bytes, expected %d bytes", iv_len, TR01_L3_IV_SIZE);
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return LT_PARAM_ERR;
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}
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lt_ctx_openssl_t *_ctx = (lt_ctx_openssl_t *)ctx;
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unsigned long err_code;
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int out_len;
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// Set IV.
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if (!EVP_DecryptInit_ex(_ctx->aesgcm_decrypt_ctx, NULL, NULL, NULL, iv)) {
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err_code = ERR_get_error();
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LT_LOG_ERROR("Failed to set AES-GCM decryption IV, err_code=%lu (%s)", err_code,
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ERR_error_string(err_code, NULL));
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return LT_CRYPTO_ERR;
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}
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// Process AAD (Additional Authenticated Data).
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if (!EVP_DecryptUpdate(_ctx->aesgcm_decrypt_ctx, NULL, &out_len, add, (int)add_len)) {
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err_code = ERR_get_error();
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LT_LOG_ERROR("Failed to process AES-GCM AAD, err_code=%lu (%s)", err_code, ERR_error_string(err_code, NULL));
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return LT_CRYPTO_ERR;
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}
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// Decrypt ciphertext.
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if (!EVP_DecryptUpdate(_ctx->aesgcm_decrypt_ctx, plaintext, &out_len, ciphertext,
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(int)(ciphertext_len - TR01_L3_TAG_SIZE))) {
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err_code = ERR_get_error();
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LT_LOG_ERROR("Failed to decrypt AES-GCM ciphertext, err_code=%lu (%s)", err_code,
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ERR_error_string(err_code, NULL));
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return LT_CRYPTO_ERR;
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}
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// Check that all ciphertext data was processed.
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if (out_len != (int)(plaintext_len)) {
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LT_LOG_ERROR("AES-GCM decryption length mismatch! Current: %d bytes, expected: %" PRIu32 " bytes", out_len,
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plaintext_len);
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return LT_CRYPTO_ERR;
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}
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// Set expected tag value.
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if (!EVP_CIPHER_CTX_ctrl(_ctx->aesgcm_decrypt_ctx, EVP_CTRL_GCM_SET_TAG, TR01_L3_TAG_SIZE,
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(void *)(ciphertext + ciphertext_len - TR01_L3_TAG_SIZE))) {
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err_code = ERR_get_error();
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LT_LOG_ERROR("Failed to set AES-GCM decryption tag, err_code=%lu (%s)", err_code,
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ERR_error_string(err_code, NULL));
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return LT_CRYPTO_ERR;
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}
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// Finalize decryption.
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if (EVP_DecryptFinal_ex(_ctx->aesgcm_decrypt_ctx, plaintext + out_len, &out_len) <= 0) {
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err_code = ERR_get_error();
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LT_LOG_ERROR("Failed to finalize AES-GCM decryption, err_code=%lu (%s)", err_code,
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ERR_error_string(err_code, NULL));
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return LT_CRYPTO_ERR;
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}
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return LT_OK;
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}
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lt_ret_t lt_aesgcm_encrypt_deinit(void *ctx)
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{
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lt_ctx_openssl_t *_ctx = (lt_ctx_openssl_t *)ctx;
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EVP_CIPHER_CTX_free(_ctx->aesgcm_encrypt_ctx);
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_ctx->aesgcm_encrypt_ctx = NULL;
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return LT_OK;
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}
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lt_ret_t lt_aesgcm_decrypt_deinit(void *ctx)
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{
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lt_ctx_openssl_t *_ctx = (lt_ctx_openssl_t *)ctx;
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EVP_CIPHER_CTX_free(_ctx->aesgcm_decrypt_ctx);
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_ctx->aesgcm_decrypt_ctx = NULL;
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return LT_OK;
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}

‎cal/openssl/lt_openssl_common.c‎

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/**
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* @file lt_openssl_common.c
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* @copyright Copyright (c) 2020-2025 Tropic Square s.r.o.
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*
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* @license For the license see LICENSE.md in the root directory of this source tree.
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*/
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#include <openssl/evp.h>
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#include <stdbool.h>
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#include "libtropic_openssl.h"
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#include "lt_aesgcm.h"
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#include "lt_crypto_common.h"
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#include "lt_sha256.h"
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lt_ret_t lt_crypto_ctx_init(void *ctx)
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{
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lt_ctx_openssl_t *_ctx = (lt_ctx_openssl_t *)ctx;
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_ctx->aesgcm_encrypt_ctx = NULL;
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_ctx->aesgcm_decrypt_ctx = NULL;
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_ctx->sha256_ctx = NULL;
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return LT_OK;
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}
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lt_ret_t lt_crypto_ctx_deinit(void *ctx)
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{
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lt_ret_t ret1 = lt_aesgcm_encrypt_deinit(ctx);
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lt_ret_t ret2 = lt_aesgcm_decrypt_deinit(ctx);
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lt_ret_t ret3 = lt_sha256_deinit(ctx);
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if (ret1 != LT_OK) {
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return ret1;
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}
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if (ret2 != LT_OK) {
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return ret2;
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}
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if (ret3 != LT_OK) {
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return ret3;
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}
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return LT_OK;
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}

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