OVMS3-idf/components/esp-tls/esp_tls_mbedtls.c

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// Copyright 2019 Espressif Systems (Shanghai) PTE LTD
//
// 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 <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netdb.h>
#include <http_parser.h>
#include "esp_tls_mbedtls.h"
#include "esp_tls_error_capture_internal.h"
#include <errno.h>
#include "esp_log.h"
#ifdef CONFIG_MBEDTLS_CERTIFICATE_BUNDLE
#include "esp_crt_bundle.h"
#endif
static const char *TAG = "esp-tls-mbedtls";
static mbedtls_x509_crt *global_cacert = NULL;
typedef struct esp_tls_pki_t {
mbedtls_x509_crt *public_cert;
mbedtls_pk_context *pk_key;
const unsigned char *publiccert_pem_buf;
unsigned int publiccert_pem_bytes;
const unsigned char *privkey_pem_buf;
unsigned int privkey_pem_bytes;
const unsigned char *privkey_password;
unsigned int privkey_password_len;
} esp_tls_pki_t;
esp_err_t esp_create_mbedtls_handle(const char *hostname, size_t hostlen, const void *cfg, esp_tls_t *tls)
{
assert(cfg != NULL);
assert(tls != NULL);
int ret;
esp_err_t esp_ret = ESP_FAIL;
tls->server_fd.fd = tls->sockfd;
mbedtls_ssl_init(&tls->ssl);
mbedtls_ctr_drbg_init(&tls->ctr_drbg);
mbedtls_ssl_config_init(&tls->conf);
mbedtls_entropy_init(&tls->entropy);
if (tls->role == ESP_TLS_CLIENT) {
esp_ret = set_client_config(hostname, hostlen, (esp_tls_cfg_t *)cfg, tls);
if (esp_ret != ESP_OK) {
ESP_LOGE(TAG, "Failed to set client configurations");
goto exit;
}
} else if (tls->role == ESP_TLS_SERVER) {
#ifdef CONFIG_ESP_TLS_SERVER
esp_ret = set_server_config((esp_tls_cfg_server_t *) cfg, tls);
if (esp_ret != 0) {
ESP_LOGE(TAG, "Failed to set server configurations");
goto exit;
}
#else
ESP_LOGE(TAG, "ESP_TLS_SERVER Not enabled in Kconfig");
goto exit;
#endif
}
if ((ret = mbedtls_ctr_drbg_seed(&tls->ctr_drbg,
mbedtls_entropy_func, &tls->entropy, NULL, 0)) != 0) {
ESP_LOGE(TAG, "mbedtls_ctr_drbg_seed returned -0x%x", -ret);
ESP_INT_EVENT_TRACKER_CAPTURE(tls->error_handle, ERR_TYPE_MBEDTLS, -ret);
esp_ret = ESP_ERR_MBEDTLS_CTR_DRBG_SEED_FAILED;
goto exit;
}
mbedtls_ssl_conf_rng(&tls->conf, mbedtls_ctr_drbg_random, &tls->ctr_drbg);
#ifdef CONFIG_MBEDTLS_DEBUG
mbedtls_esp_enable_debug_log(&tls->conf, CONFIG_MBEDTLS_DEBUG_LEVEL);
#endif
if ((ret = mbedtls_ssl_setup(&tls->ssl, &tls->conf)) != 0) {
ESP_LOGE(TAG, "mbedtls_ssl_setup returned -0x%x", -ret);
ESP_INT_EVENT_TRACKER_CAPTURE(tls->error_handle, ERR_TYPE_MBEDTLS, -ret);
esp_ret = ESP_ERR_MBEDTLS_SSL_SETUP_FAILED;
goto exit;
}
mbedtls_ssl_set_bio(&tls->ssl, &tls->server_fd, mbedtls_net_send, mbedtls_net_recv, NULL);
return ESP_OK;
exit:
esp_mbedtls_cleanup(tls);
return esp_ret;
}
int esp_mbedtls_handshake(esp_tls_t *tls, const esp_tls_cfg_t *cfg)
{
int ret;
ret = mbedtls_ssl_handshake(&tls->ssl);
if (ret == 0) {
tls->conn_state = ESP_TLS_DONE;
return 1;
} else {
if (ret != ESP_TLS_ERR_SSL_WANT_READ && ret != ESP_TLS_ERR_SSL_WANT_WRITE) {
ESP_LOGE(TAG, "mbedtls_ssl_handshake returned -0x%x", -ret);
ESP_INT_EVENT_TRACKER_CAPTURE(tls->error_handle, ERR_TYPE_MBEDTLS, -ret);
ESP_INT_EVENT_TRACKER_CAPTURE(tls->error_handle, ERR_TYPE_ESP, ESP_ERR_MBEDTLS_SSL_HANDSHAKE_FAILED);
if (cfg->cacert_buf != NULL || cfg->use_global_ca_store == true) {
/* This is to check whether handshake failed due to invalid certificate*/
esp_mbedtls_verify_certificate(tls);
}
tls->conn_state = ESP_TLS_FAIL;
return -1;
}
/* Irrespective of blocking or non-blocking I/O, we return on getting ESP_TLS_ERR_SSL_WANT_READ
or ESP_TLS_ERR_SSL_WANT_WRITE during handshake */
return 0;
}
}
ssize_t esp_mbedtls_read(esp_tls_t *tls, char *data, size_t datalen)
{
ssize_t ret = mbedtls_ssl_read(&tls->ssl, (unsigned char *)data, datalen);
if (ret < 0) {
if (ret == MBEDTLS_ERR_SSL_PEER_CLOSE_NOTIFY) {
return 0;
}
if (ret != ESP_TLS_ERR_SSL_WANT_READ && ret != ESP_TLS_ERR_SSL_WANT_WRITE) {
ESP_INT_EVENT_TRACKER_CAPTURE(tls->error_handle, ERR_TYPE_MBEDTLS, -ret);
ESP_LOGE(TAG, "read error :%d:", ret);
}
}
return ret;
}
ssize_t esp_mbedtls_write(esp_tls_t *tls, const char *data, size_t datalen)
{
size_t written = 0;
size_t write_len = datalen;
while (written < datalen) {
if (write_len > MBEDTLS_SSL_OUT_CONTENT_LEN) {
write_len = MBEDTLS_SSL_OUT_CONTENT_LEN;
}
if (datalen > MBEDTLS_SSL_OUT_CONTENT_LEN) {
ESP_LOGD(TAG, "Fragmenting data of excessive size :%d, offset: %d, size %d", datalen, written, write_len);
}
ssize_t ret = mbedtls_ssl_write(&tls->ssl, (unsigned char*) data + written, write_len);
if (ret <= 0) {
if (ret != ESP_TLS_ERR_SSL_WANT_READ && ret != ESP_TLS_ERR_SSL_WANT_WRITE && ret != 0) {
ESP_INT_EVENT_TRACKER_CAPTURE(tls->error_handle, ERR_TYPE_MBEDTLS, -ret);
ESP_INT_EVENT_TRACKER_CAPTURE(tls->error_handle, ERR_TYPE_ESP, ESP_ERR_MBEDTLS_SSL_WRITE_FAILED);
ESP_LOGE(TAG, "write error :%d:", ret);
return ret;
} else {
// Exitting the tls-write process as less than desired datalen are writable
ESP_LOGD(TAG, "mbedtls_ssl_write() returned %d, already written %d, exitting...", ret, written);
return written;
}
}
written += ret;
write_len = datalen - written;
}
return written;
}
void esp_mbedtls_conn_delete(esp_tls_t *tls)
{
if (tls != NULL) {
esp_mbedtls_cleanup(tls);
if (tls->is_tls) {
mbedtls_net_free(&tls->server_fd);
}
}
}
void esp_mbedtls_verify_certificate(esp_tls_t *tls)
{
int flags;
char buf[100];
if ((flags = mbedtls_ssl_get_verify_result(&tls->ssl)) != 0) {
ESP_LOGI(TAG, "Failed to verify peer certificate!");
ESP_INT_EVENT_TRACKER_CAPTURE(tls->error_handle, ERR_TYPE_MBEDTLS_CERT_FLAGS, flags);
bzero(buf, sizeof(buf));
mbedtls_x509_crt_verify_info(buf, sizeof(buf), " ! ", flags);
ESP_LOGI(TAG, "verification info: %s", buf);
} else {
ESP_LOGI(TAG, "Certificate verified.");
}
}
ssize_t esp_mbedtls_get_bytes_avail(esp_tls_t *tls)
{
if (!tls) {
ESP_LOGE(TAG, "empty arg passed to esp_tls_get_bytes_avail()");
return ESP_FAIL;
}
return mbedtls_ssl_get_bytes_avail(&tls->ssl);
}
void esp_mbedtls_cleanup(esp_tls_t *tls)
{
if (!tls) {
return;
}
if (tls->cacert_ptr != global_cacert) {
mbedtls_x509_crt_free(tls->cacert_ptr);
}
tls->cacert_ptr = NULL;
#ifdef CONFIG_ESP_TLS_SERVER
mbedtls_x509_crt_free(&tls->servercert);
mbedtls_pk_free(&tls->serverkey);
#endif
mbedtls_x509_crt_free(&tls->cacert);
mbedtls_x509_crt_free(&tls->clientcert);
mbedtls_pk_free(&tls->clientkey);
mbedtls_entropy_free(&tls->entropy);
mbedtls_ssl_config_free(&tls->conf);
mbedtls_ctr_drbg_free(&tls->ctr_drbg);
mbedtls_ssl_free(&tls->ssl);
}
static esp_err_t set_ca_cert(esp_tls_t *tls, const unsigned char *cacert, size_t cacert_len)
{
assert(tls);
tls->cacert_ptr = &tls->cacert;
mbedtls_x509_crt_init(tls->cacert_ptr);
int ret = mbedtls_x509_crt_parse(tls->cacert_ptr, cacert, cacert_len);
if (ret < 0) {
ESP_LOGE(TAG, "mbedtls_x509_crt_parse returned -0x%x", -ret);
ESP_INT_EVENT_TRACKER_CAPTURE(tls->error_handle, ERR_TYPE_MBEDTLS, -ret);
return ESP_ERR_MBEDTLS_X509_CRT_PARSE_FAILED;
}
mbedtls_ssl_conf_authmode(&tls->conf, MBEDTLS_SSL_VERIFY_REQUIRED);
mbedtls_ssl_conf_ca_chain(&tls->conf, tls->cacert_ptr, NULL);
return ESP_OK;
}
static esp_err_t set_pki_context(esp_tls_t *tls, const esp_tls_pki_t *pki)
{
assert(tls);
assert(pki);
int ret;
if (pki->publiccert_pem_buf != NULL &&
pki->privkey_pem_buf != NULL &&
pki->public_cert != NULL &&
pki->pk_key != NULL) {
mbedtls_x509_crt_init(pki->public_cert);
mbedtls_pk_init(pki->pk_key);
ret = mbedtls_x509_crt_parse(pki->public_cert, pki->publiccert_pem_buf, pki->publiccert_pem_bytes);
if (ret < 0) {
ESP_LOGE(TAG, "mbedtls_x509_crt_parse returned -0x%x", -ret);
ESP_INT_EVENT_TRACKER_CAPTURE(tls->error_handle, ERR_TYPE_MBEDTLS, -ret);
return ESP_ERR_MBEDTLS_X509_CRT_PARSE_FAILED;
}
ret = mbedtls_pk_parse_key(pki->pk_key, pki->privkey_pem_buf, pki->privkey_pem_bytes,
pki->privkey_password, pki->privkey_password_len);
if (ret < 0) {
ESP_LOGE(TAG, "mbedtls_pk_parse_keyfile returned -0x%x", -ret);
ESP_INT_EVENT_TRACKER_CAPTURE(tls->error_handle, ERR_TYPE_MBEDTLS, -ret);
return ESP_ERR_MBEDTLS_PK_PARSE_KEY_FAILED;
}
ret = mbedtls_ssl_conf_own_cert(&tls->conf, pki->public_cert, pki->pk_key);
if (ret < 0) {
ESP_LOGE(TAG, "mbedtls_ssl_conf_own_cert returned -0x%x", -ret);
ESP_INT_EVENT_TRACKER_CAPTURE(tls->error_handle, ERR_TYPE_MBEDTLS, -ret);
return ESP_ERR_MBEDTLS_SSL_CONF_OWN_CERT_FAILED;
}
} else {
return ESP_ERR_INVALID_ARG;
}
return ESP_OK;
}
static esp_err_t set_global_ca_store(esp_tls_t *tls)
{
assert(tls);
if (global_cacert == NULL) {
ESP_LOGE(TAG, "global_cacert is NULL");
return ESP_ERR_INVALID_STATE;
}
tls->cacert_ptr = global_cacert;
mbedtls_ssl_conf_authmode(&tls->conf, MBEDTLS_SSL_VERIFY_REQUIRED);
mbedtls_ssl_conf_ca_chain(&tls->conf, tls->cacert_ptr, NULL);
return ESP_OK;
}
#ifdef CONFIG_ESP_TLS_SERVER
esp_err_t set_server_config(esp_tls_cfg_server_t *cfg, esp_tls_t *tls)
{
assert(cfg != NULL);
assert(tls != NULL);
int ret;
esp_err_t esp_ret;
if ((ret = mbedtls_ssl_config_defaults(&tls->conf,
MBEDTLS_SSL_IS_SERVER,
MBEDTLS_SSL_TRANSPORT_STREAM,
MBEDTLS_SSL_PRESET_DEFAULT)) != 0) {
ESP_LOGE(TAG, "mbedtls_ssl_config_defaults returned %d", ret);
ESP_INT_EVENT_TRACKER_CAPTURE(tls->error_handle, ERR_TYPE_MBEDTLS, -ret);
return ESP_ERR_MBEDTLS_SSL_CONFIG_DEFAULTS_FAILED;
}
#ifdef CONFIG_MBEDTLS_SSL_ALPN
if (cfg->alpn_protos) {
mbedtls_ssl_conf_alpn_protocols(&tls->conf, cfg->alpn_protos);
}
#endif
if (cfg->cacert_buf != NULL) {
esp_ret = set_ca_cert(tls, cfg->cacert_buf, cfg->cacert_bytes);
if (esp_ret != ESP_OK) {
return esp_ret;
}
} else {
mbedtls_ssl_conf_authmode(&tls->conf, MBEDTLS_SSL_VERIFY_NONE);
}
if (cfg->servercert_buf != NULL && cfg->serverkey_buf != NULL) {
esp_tls_pki_t pki = {
.public_cert = &tls->servercert,
.pk_key = &tls->serverkey,
.publiccert_pem_buf = cfg->servercert_buf,
.publiccert_pem_bytes = cfg->servercert_bytes,
.privkey_pem_buf = cfg->serverkey_buf,
.privkey_pem_bytes = cfg->serverkey_bytes,
.privkey_password = cfg->serverkey_password,
.privkey_password_len = cfg->serverkey_password_len,
};
esp_ret = set_pki_context(tls, &pki);
if (esp_ret != ESP_OK) {
ESP_LOGE(TAG, "Failed to set server pki context");
return esp_ret;
}
} else {
ESP_LOGE(TAG, "Missing server certificate and/or key");
return ESP_ERR_INVALID_STATE;
}
return ESP_OK;
}
#endif /* ! CONFIG_ESP_TLS_SERVER */
esp_err_t set_client_config(const char *hostname, size_t hostlen, esp_tls_cfg_t *cfg, esp_tls_t *tls)
{
assert(cfg != NULL);
assert(tls != NULL);
int ret;
if (!cfg->skip_common_name) {
char *use_host = NULL;
if (cfg->common_name != NULL) {
use_host = strndup(cfg->common_name, strlen(cfg->common_name));
} else {
use_host = strndup(hostname, hostlen);
}
if (use_host == NULL) {
return ESP_ERR_NO_MEM;
}
/* Hostname set here should match CN in server certificate */
if ((ret = mbedtls_ssl_set_hostname(&tls->ssl, use_host)) != 0) {
ESP_LOGE(TAG, "mbedtls_ssl_set_hostname returned -0x%x", -ret);
ESP_INT_EVENT_TRACKER_CAPTURE(tls->error_handle, ERR_TYPE_MBEDTLS, -ret);
free(use_host);
return ESP_ERR_MBEDTLS_SSL_SET_HOSTNAME_FAILED;
}
free(use_host);
}
if ((ret = mbedtls_ssl_config_defaults(&tls->conf,
MBEDTLS_SSL_IS_CLIENT,
MBEDTLS_SSL_TRANSPORT_STREAM,
MBEDTLS_SSL_PRESET_DEFAULT)) != 0) {
ESP_LOGE(TAG, "mbedtls_ssl_config_defaults returned -0x%x", -ret);
ESP_INT_EVENT_TRACKER_CAPTURE(tls->error_handle, ERR_TYPE_MBEDTLS, -ret);
return ESP_ERR_MBEDTLS_SSL_CONFIG_DEFAULTS_FAILED;
}
if (cfg->alpn_protos) {
#ifdef CONFIG_MBEDTLS_SSL_ALPN
if ((ret = mbedtls_ssl_conf_alpn_protocols(&tls->conf, cfg->alpn_protos) != 0)) {
ESP_LOGE(TAG, "mbedtls_ssl_conf_alpn_protocols returned -0x%x", -ret);
ESP_INT_EVENT_TRACKER_CAPTURE(tls->error_handle, ERR_TYPE_MBEDTLS, -ret);
return ESP_ERR_MBEDTLS_SSL_CONF_ALPN_PROTOCOLS_FAILED;
}
#else
ESP_LOGE(TAG, "alpn_protos configured but not enabled in menuconfig: Please enable MBEDTLS_SSL_ALPN option");
return ESP_ERR_INVALID_STATE;
#endif
}
if (cfg->crt_bundle_attach != NULL) {
#ifdef CONFIG_MBEDTLS_CERTIFICATE_BUNDLE
ESP_LOGD(TAG, "Use certificate bundle");
mbedtls_ssl_conf_authmode(&tls->conf, MBEDTLS_SSL_VERIFY_REQUIRED);
cfg->crt_bundle_attach(&tls->conf);
#else //CONFIG_MBEDTLS_CERTIFICATE_BUNDLE
ESP_LOGE(TAG, "use_crt_bundle configured but not enabled in menuconfig: Please enable MBEDTLS_CERTIFICATE_BUNDLE option");
return ESP_ERR_INVALID_STATE;
#endif
} else if (cfg->use_global_ca_store == true) {
esp_err_t esp_ret = set_global_ca_store(tls);
if (esp_ret != ESP_OK) {
return esp_ret;
}
} else if (cfg->cacert_buf != NULL) {
esp_err_t esp_ret = set_ca_cert(tls, cfg->cacert_buf, cfg->cacert_bytes);
if (esp_ret != ESP_OK) {
return esp_ret;
}
mbedtls_ssl_conf_ca_chain(&tls->conf, tls->cacert_ptr, NULL);
} else if (cfg->psk_hint_key) {
#if defined(CONFIG_ESP_TLS_PSK_VERIFICATION)
//
// PSK encryption mode is configured only if no certificate supplied and psk pointer not null
ESP_LOGD(TAG, "ssl psk authentication");
ret = mbedtls_ssl_conf_psk(&tls->conf, cfg->psk_hint_key->key, cfg->psk_hint_key->key_size,
(const unsigned char *)cfg->psk_hint_key->hint, strlen(cfg->psk_hint_key->hint));
if (ret != 0) {
ESP_LOGE(TAG, "mbedtls_ssl_conf_psk returned -0x%x", -ret);
ESP_INT_EVENT_TRACKER_CAPTURE(tls->error_handle, ERR_TYPE_MBEDTLS, -ret);
return ESP_ERR_MBEDTLS_SSL_CONF_PSK_FAILED;
}
#else
ESP_LOGE(TAG, "psk_hint_key configured but not enabled in menuconfig: Please enable ESP_TLS_PSK_VERIFICATION option");
return ESP_ERR_INVALID_STATE;
#endif
} else {
mbedtls_ssl_conf_authmode(&tls->conf, MBEDTLS_SSL_VERIFY_NONE);
}
if (cfg->clientcert_buf != NULL && cfg->clientkey_buf != NULL) {
esp_tls_pki_t pki = {
.public_cert = &tls->clientcert,
.pk_key = &tls->clientkey,
.publiccert_pem_buf = cfg->clientcert_buf,
.publiccert_pem_bytes = cfg->clientcert_bytes,
.privkey_pem_buf = cfg->clientkey_buf,
.privkey_pem_bytes = cfg->clientkey_bytes,
.privkey_password = cfg->clientkey_password,
.privkey_password_len = cfg->clientkey_password_len,
};
esp_err_t esp_ret = set_pki_context(tls, &pki);
if (esp_ret != ESP_OK) {
ESP_LOGE(TAG, "Failed to set client pki context");
return esp_ret;
}
} else if (cfg->clientcert_buf != NULL || cfg->clientkey_buf != NULL) {
ESP_LOGE(TAG, "You have to provide both clientcert_buf and clientkey_buf for mutual authentication");
return ESP_ERR_INVALID_STATE;
}
return ESP_OK;
}
#ifdef CONFIG_ESP_TLS_SERVER
/**
* @brief Create TLS/SSL server session
*/
int esp_mbedtls_server_session_create(esp_tls_cfg_server_t *cfg, int sockfd, esp_tls_t *tls)
{
if (tls == NULL || cfg == NULL) {
return -1;
}
tls->role = ESP_TLS_SERVER;
tls->sockfd = sockfd;
esp_err_t esp_ret = esp_create_mbedtls_handle(NULL, 0, cfg, tls);
if (esp_ret != ESP_OK) {
ESP_LOGE(TAG, "create_ssl_handle failed");
ESP_INT_EVENT_TRACKER_CAPTURE(tls->error_handle, ERR_TYPE_ESP, esp_ret);
tls->conn_state = ESP_TLS_FAIL;
return -1;
}
tls->read = esp_mbedtls_read;
tls->write = esp_mbedtls_write;
int ret;
while ((ret = mbedtls_ssl_handshake(&tls->ssl)) != 0) {
if (ret != ESP_TLS_ERR_SSL_WANT_READ && ret != ESP_TLS_ERR_SSL_WANT_WRITE) {
ESP_LOGE(TAG, "mbedtls_ssl_handshake returned %d", ret);
tls->conn_state = ESP_TLS_FAIL;
return ret;
}
}
return 0;
}
/**
* @brief Close the server side TLS/SSL connection and free any allocated resources.
*/
void esp_mbedtls_server_session_delete(esp_tls_t *tls)
{
if (tls != NULL) {
esp_mbedtls_cleanup(tls);
free(tls);
}
};
#endif /* ! CONFIG_ESP_TLS_SERVER */
esp_err_t esp_mbedtls_init_global_ca_store(void)
{
if (global_cacert == NULL) {
global_cacert = (mbedtls_x509_crt *)calloc(1, sizeof(mbedtls_x509_crt));
if (global_cacert == NULL) {
ESP_LOGE(TAG, "global_cacert not allocated");
return ESP_ERR_NO_MEM;
}
mbedtls_x509_crt_init(global_cacert);
}
return ESP_OK;
}
esp_err_t esp_mbedtls_set_global_ca_store(const unsigned char *cacert_pem_buf, const unsigned int cacert_pem_bytes)
{
if (cacert_pem_buf == NULL) {
ESP_LOGE(TAG, "cacert_pem_buf is null");
return ESP_ERR_INVALID_ARG;
}
int ret;
if (global_cacert == NULL) {
ret = esp_mbedtls_init_global_ca_store();
if (ret != ESP_OK) {
return ret;
}
}
ret = mbedtls_x509_crt_parse(global_cacert, cacert_pem_buf, cacert_pem_bytes);
if (ret < 0) {
ESP_LOGE(TAG, "mbedtls_x509_crt_parse returned -0x%x", -ret);
mbedtls_x509_crt_free(global_cacert);
global_cacert = NULL;
return ESP_FAIL;
} else if (ret > 0) {
ESP_LOGE(TAG, "mbedtls_x509_crt_parse was partly successful. No. of failed certificates: %d", ret);
return ESP_ERR_MBEDTLS_CERT_PARTLY_OK;
}
return ESP_OK;
}
mbedtls_x509_crt *esp_mbedtls_get_global_ca_store(void)
{
return global_cacert;
}
void esp_mbedtls_free_global_ca_store(void)
{
if (global_cacert) {
mbedtls_x509_crt_free(global_cacert);
global_cacert = NULL;
}
}