esp-idf/components/mbedtls/test/test_esp_crt_bundle.c

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/* SSL server using plain mbedTLS sockets
*
* Adapted from the ssl_server example in mbedtls.
*
* Original Copyright (C) 2006-2015, ARM Limited, All Rights Reserved
* Additions Copyright (C) Copyright 2019 Espressif Systems (Shanghai) PTE LTD, Apache 2.0 License.
*
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include "esp_err.h"
#include "esp_log.h"
#include "freertos/FreeRTOS.h"
#include "freertos/task.h"
#include "freertos/semphr.h"
#include "mbedtls/entropy.h"
#include "mbedtls/ctr_drbg.h"
#include "mbedtls/certs.h"
#include "mbedtls/x509.h"
#include "mbedtls/ssl.h"
#include "mbedtls/net_sockets.h"
#include "mbedtls/error.h"
#include "mbedtls/debug.h"
#include "esp_crt_bundle.h"
#include "unity.h"
#include "test_utils.h"
#define SERVER_ADDRESS "localhost"
#define SERVER_PORT "4433"
extern const uint8_t server_cert_chain_pem_start[] asm("_binary_server_cert_chain_pem_start");
extern const uint8_t server_cert_chain_pem_end[] asm("_binary_server_cert_chain_pem_end");
extern const uint8_t server_pk_start[] asm("_binary_prvtkey_pem_start");
extern const uint8_t server_pk_end[] asm("_binary_prvtkey_pem_end");
extern const uint8_t server_cert_bundle_start[] asm("_binary_server_cert_bundle_start");
extern const uint8_t server_cert_bundle_end[] asm("_binary_server_cert_bundle_end");
extern const uint8_t bad_md_crt_pem_start[] asm("_binary_bad_md_crt_pem_start");
extern const uint8_t bad_md_crt_pem_end[] asm("_binary_bad_md_crt_pem_end");
extern const uint8_t wrong_sig_crt_pem_start[] asm("_binary_wrong_sig_crt_esp32_com_pem_start");
extern const uint8_t wrong_sig_crt_pem_end[] asm("_binary_wrong_sig_crt_esp32_com_pem_end");
extern const uint8_t correct_sig_crt_pem_start[] asm("_binary_correct_sig_crt_esp32_com_pem_start");
extern const uint8_t correct_sig_crt_pem_end[] asm("_binary_correct_sig_crt_esp32_com_pem_end");
typedef struct {
mbedtls_ssl_context ssl;
mbedtls_net_context listen_fd;
mbedtls_net_context client_fd;
mbedtls_entropy_context entropy;
mbedtls_ctr_drbg_context ctr_drbg;
mbedtls_ssl_config conf;
mbedtls_x509_crt cert;
mbedtls_pk_context pkey;
} mbedtls_endpoint_t;
typedef enum {
ESP_CRT_VALIDATE_UNKNOWN,
ESP_CRT_VALIDATE_OK,
ESP_CRT_VALIDATE_FAIL,
}esp_crt_validate_res_t;
int esp_crt_verify_callback(void *buf, mbedtls_x509_crt *crt, int data, uint32_t *flags);
static const char *TAG = "cert_bundle_test";
static volatile bool exit_flag;
esp_err_t endpoint_teardown(mbedtls_endpoint_t *endpoint);
esp_err_t server_setup(mbedtls_endpoint_t *server)
{
int ret;
mbedtls_ssl_config_init( &server->conf );
mbedtls_net_init( &server->listen_fd );
mbedtls_net_init( &server->client_fd );
mbedtls_ssl_init( &server->ssl );
mbedtls_x509_crt_init( &server->cert );
mbedtls_pk_init( &server->pkey );
mbedtls_entropy_init( &server->entropy );
mbedtls_ctr_drbg_init( &server->ctr_drbg );
ESP_LOGI(TAG, "Loading the server cert and key");
ret = mbedtls_x509_crt_parse( &server->cert, server_cert_chain_pem_start,
server_cert_chain_pem_end - server_cert_chain_pem_start);
if ( ret != 0 ) {
ESP_LOGE(TAG, "mbedtls_x509_crt_parse returned %d", ret );
return ESP_FAIL;
}
ret = mbedtls_pk_parse_key( &server->pkey, (const unsigned char *)server_pk_start,
server_pk_end - server_pk_start, NULL, 0 );
if ( ret != 0 ) {
ESP_LOGE(TAG, "mbedtls_pk_parse_key returned %d", ret );
return ESP_FAIL;
}
ESP_LOGI(TAG, "Bind on https://%s:%s/", SERVER_ADDRESS, SERVER_PORT );
if ( ( ret = mbedtls_net_bind( &server->listen_fd, NULL, SERVER_PORT, MBEDTLS_NET_PROTO_TCP ) ) != 0 ) {
ESP_LOGE(TAG, "mbedtls_net_bind returned %d", ret );
return ESP_FAIL;
}
mbedtls_net_set_nonblock(&server->listen_fd);
ESP_LOGI(TAG, "Seeding the random number generator");
if ( ( ret = mbedtls_ctr_drbg_seed( &server->ctr_drbg, mbedtls_entropy_func, &server->entropy,
NULL, 0) ) != 0 ) {
ESP_LOGE(TAG, "mbedtls_ctr_drbg_seed returned %d", ret );
return ESP_FAIL;
}
ESP_LOGI(TAG, "Setting up the SSL data");
if ( ( ret = mbedtls_ssl_config_defaults( &server->conf,
MBEDTLS_SSL_IS_SERVER,
MBEDTLS_SSL_TRANSPORT_STREAM,
MBEDTLS_SSL_PRESET_DEFAULT ) ) != 0 ) {
ESP_LOGE(TAG, "mbedtls_ssl_config_defaults returned %d", ret );
return ESP_FAIL;
}
mbedtls_ssl_conf_rng( &server->conf, mbedtls_ctr_drbg_random, &server->ctr_drbg );
if (( ret = mbedtls_ssl_conf_own_cert( &server->conf, &server->cert, &server->pkey ) ) != 0 ) {
ESP_LOGE(TAG, "mbedtls_ssl_conf_own_cert returned %d", ret );
return ESP_FAIL;
}
if (( ret = mbedtls_ssl_setup( &server->ssl, &server->conf ) ) != 0 ) {
ESP_LOGE(TAG, "mbedtls_ssl_setup returned %d", ret );
return ESP_FAIL;
}
return ESP_OK;
}
void server_task(void *pvParameters)
{
int ret;
mbedtls_endpoint_t server;
xSemaphoreHandle *sema = (xSemaphoreHandle *) pvParameters;
if (server_setup(&server) != ESP_OK) {
ESP_LOGE(TAG, "SSL server setup failed");
goto exit;
}
bool connected = false;
while (!exit_flag) {
ret = mbedtls_net_accept( &server.listen_fd, &server.client_fd, NULL, 0, NULL );
if (ret == 0) {
connected = true;
}
if (connected) {
mbedtls_ssl_set_bio( &server.ssl, &server.client_fd, mbedtls_net_send, mbedtls_net_recv, NULL );
ret = mbedtls_ssl_handshake( &server.ssl );
mbedtls_ssl_session_reset(&server.ssl);
connected = false;
}
vTaskDelay(20 / portTICK_PERIOD_MS);
}
ESP_LOGE(TAG, "Server shutdown");
exit:
endpoint_teardown(&server);
xSemaphoreGive(*sema);
vTaskDelete(NULL);
}
esp_err_t endpoint_teardown(mbedtls_endpoint_t *endpoint)
{
mbedtls_net_free( &endpoint->client_fd );
mbedtls_net_free( &endpoint->listen_fd );
mbedtls_x509_crt_free( &endpoint->cert );
mbedtls_pk_free( &endpoint->pkey );
mbedtls_ssl_free( &endpoint->ssl );
mbedtls_ssl_config_free( &endpoint->conf );
mbedtls_ctr_drbg_free( &endpoint->ctr_drbg );
mbedtls_entropy_free( &endpoint->entropy );
return ESP_OK;
}
esp_err_t client_setup(mbedtls_endpoint_t *client)
{
int ret;
mbedtls_ssl_config_init( &client->conf );
mbedtls_net_init( &client->client_fd );
mbedtls_ssl_init( &client->ssl );
mbedtls_x509_crt_init( &client->cert );
mbedtls_pk_init( &client->pkey );
mbedtls_entropy_init( &client->entropy );
mbedtls_ctr_drbg_init( &client->ctr_drbg );
ESP_LOGI(TAG, "Seeding the random number generator");
if ((ret = mbedtls_ctr_drbg_seed(&client->ctr_drbg, mbedtls_entropy_func, &client->entropy,
NULL, 0)) != 0) {
ESP_LOGE(TAG, "mbedtls_ctr_drbg_seed returned %d", ret);
return ESP_FAIL;
}
ESP_LOGI(TAG, "Setting hostname for TLS session...");
/* Hostname set here should match CN in server certificate */
if ((ret = mbedtls_ssl_set_hostname(&client->ssl, SERVER_ADDRESS)) != 0) {
ESP_LOGE(TAG, "mbedtls_ssl_set_hostname returned -0x%x", -ret);
return ESP_FAIL;
}
ESP_LOGI(TAG, "Setting up the SSL/TLS structure...");
if ((ret = mbedtls_ssl_config_defaults(&client->conf,
MBEDTLS_SSL_IS_CLIENT,
MBEDTLS_SSL_TRANSPORT_STREAM,
MBEDTLS_SSL_PRESET_DEFAULT)) != 0) {
ESP_LOGE(TAG, "mbedtls_ssl_config_defaults returned %d", ret);
return ESP_FAIL;
}
mbedtls_ssl_conf_rng(&client->conf, mbedtls_ctr_drbg_random, &client->ctr_drbg);
if ((ret = mbedtls_ssl_setup(&client->ssl, &client->conf)) != 0) {
ESP_LOGE(TAG, "mbedtls_ssl_setup returned -0x%x\n\n", -ret);
return ESP_FAIL;
}
return ESP_OK;
}
int client_task(const uint8_t *bundle, esp_crt_validate_res_t *res)
{
int ret = ESP_FAIL;
mbedtls_endpoint_t client;
*res = ESP_CRT_VALIDATE_UNKNOWN;
if (client_setup(&client) != ESP_OK) {
ESP_LOGE(TAG, "SSL client setup failed");
goto exit;
}
esp_crt_bundle_attach(&client.conf);
if (bundle) {
/* Set a bundle different from the menuconfig bundle */
esp_crt_bundle_set(bundle);
}
ESP_LOGI(TAG, "Connecting to %s:%s...", SERVER_ADDRESS, SERVER_PORT);
if ((ret = mbedtls_net_connect(&client.client_fd, SERVER_ADDRESS, SERVER_PORT, MBEDTLS_NET_PROTO_TCP)) != 0) {
ESP_LOGE(TAG, "mbedtls_net_connect returned -%x", -ret);
goto exit;
}
ESP_LOGI(TAG, "Connected.");
mbedtls_ssl_set_bio(&client.ssl, &client.client_fd, mbedtls_net_send, mbedtls_net_recv, NULL);
ESP_LOGI(TAG, "Performing the SSL/TLS handshake with bundle that is missing the server root certificate");
while ( ( ret = mbedtls_ssl_handshake( &client.ssl ) ) != 0 ) {
if ( ret != MBEDTLS_ERR_SSL_WANT_READ && ret != MBEDTLS_ERR_SSL_WANT_WRITE ) {
printf( "mbedtls_ssl_handshake failed with -0x%x\n", -ret );
break;
}
}
ESP_LOGI(TAG, "Verifying peer X.509 certificate for bundle ...");
ret = mbedtls_ssl_get_verify_result(&client.ssl);
*res = (ret == 0) ? ESP_CRT_VALIDATE_OK : ESP_CRT_VALIDATE_FAIL;
// Reset session before new connection
mbedtls_ssl_close_notify(&client.ssl);
mbedtls_ssl_session_reset(&client.ssl);
mbedtls_net_free( &client.client_fd);
exit:
mbedtls_ssl_close_notify(&client.ssl);
mbedtls_ssl_session_reset(&client.ssl);
esp_crt_bundle_detach(&client.conf);
endpoint_teardown(&client);
return ret;
}
TEST_CASE("custom certificate bundle", "[mbedtls]")
{
esp_crt_validate_res_t validate_res;
test_case_uses_tcpip();
xSemaphoreHandle exit_sema = xSemaphoreCreateBinary();
exit_flag = false;
xTaskCreate(server_task, "server task", 8192, &exit_sema, 10, NULL);
// Wait for the server to start up
vTaskDelay(100 / portTICK_PERIOD_MS);
/* Test with default crt bundle that doesnt contain the ca crt */
client_task(NULL, &validate_res);
TEST_ASSERT(validate_res == ESP_CRT_VALIDATE_FAIL);
/* Test with bundle that does contain the CA crt */
client_task(server_cert_bundle_start, &validate_res);
TEST_ASSERT(validate_res == ESP_CRT_VALIDATE_OK);
exit_flag = true;
if (!xSemaphoreTake(exit_sema, 10000 / portTICK_PERIOD_MS)) {
TEST_FAIL_MESSAGE("exit_sem not released by server task");
}
vSemaphoreDelete(exit_sema);
}
TEST_CASE("custom certificate bundle - weak hash", "[mbedtls]")
{
/* A weak signature hash on the trusted certificate should not stop
us from verifying the chain, since we already trust it a weak signature hash is
not a security issue */
mbedtls_x509_crt crt;
uint32_t flags = 0;
esp_crt_bundle_attach(NULL);
mbedtls_x509_crt_init( &crt );
mbedtls_x509_crt_parse(&crt, bad_md_crt_pem_start, bad_md_crt_pem_end - bad_md_crt_pem_start);
TEST_ASSERT(mbedtls_x509_crt_verify(&crt, NULL, NULL, NULL, &flags, esp_crt_verify_callback, NULL) == 0);
mbedtls_x509_crt_free(&crt);
esp_crt_bundle_detach(NULL);
}
TEST_CASE("custom certificate bundle - wrong signature", "[mbedtls]")
{
/* Check that the bundle will not verify a valid certificate from trusted root where the signature is wrong */
mbedtls_x509_crt crt;
uint32_t flags = 0;
esp_crt_bundle_attach(NULL);
mbedtls_x509_crt_init( &crt );
/* esp32.com cert chain where 1 byte in the signature is changed */
printf("Testing certificate with wrong signature\n");
mbedtls_x509_crt_parse(&crt, wrong_sig_crt_pem_start, wrong_sig_crt_pem_end - wrong_sig_crt_pem_start);
TEST_ASSERT(mbedtls_x509_crt_verify(&crt, NULL, NULL, NULL, &flags, esp_crt_verify_callback, NULL) != 0);
mbedtls_x509_crt_free(&crt);
mbedtls_x509_crt_init( &crt );
/* the correct esp32.com cert chain*/
printf("Testing certificate with correct signature\n");
mbedtls_x509_crt_parse(&crt, correct_sig_crt_pem_start, correct_sig_crt_pem_end - correct_sig_crt_pem_start);
TEST_ASSERT(mbedtls_x509_crt_verify(&crt, NULL, NULL, NULL, &flags, esp_crt_verify_callback, NULL) == 0);
mbedtls_x509_crt_free(&crt);
esp_crt_bundle_detach(NULL);
}