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Feature: Support for global CA store.

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Added a new API esp_tls_set_global_ca_store(esp_tls_cfg_t *cfg) which creates a global_cacert which can be used by multiple connections by setting the use_global_ca_store variable to true in their respective structure of esp_tls_cfg_t. Also changed the cacert in the structure of esp_tls_t to a pointer.
This commit is contained in:
Chirag Atal 2018-10-04 16:05:02 +05:30
parent 3977d4b565
commit b7cca3c414
2 changed files with 103 additions and 6 deletions
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65
components/esp-tls/esp_tls.c
View file

@ -25,6 +25,7 @@
#include <errno.h>
static const char *TAG = "esp-tls";
static mbedtls_x509_crt *global_cacert = NULL;
#ifdef ESP_PLATFORM
#include <esp_log.h>
@ -140,6 +141,46 @@ err_freeaddr:
return ret;
}
esp_err_t esp_tls_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;
}
if (global_cacert != NULL) {
mbedtls_x509_crt_free(global_cacert);
}
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);
int 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\n\n", -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_OK;
}
mbedtls_x509_crt *esp_tls_get_global_ca_store()
{
return global_cacert;
}
void esp_tls_free_global_ca_store()
{
if (global_cacert) {
mbedtls_x509_crt_free(global_cacert);
global_cacert = NULL;
}
}
static void verify_certificate(esp_tls_t *tls)
{
int flags;
@ -159,7 +200,10 @@ static void mbedtls_cleanup(esp_tls_t *tls)
if (!tls) {
return;
}
mbedtls_x509_crt_free(&tls->cacert);
if (tls->cacert_ptr != global_cacert) {
mbedtls_x509_crt_free(tls->cacert_ptr);
}
tls->cacert_ptr = NULL;
mbedtls_entropy_free(&tls->entropy);
mbedtls_ssl_config_free(&tls->conf);
mbedtls_ctr_drbg_free(&tls->ctr_drbg);
@ -209,15 +253,24 @@ static int create_ssl_handle(esp_tls_t *tls, const char *hostname, size_t hostle
mbedtls_ssl_conf_alpn_protocols(&tls->conf, cfg->alpn_protos);
}
if (cfg->cacert_pem_buf != NULL) {
mbedtls_x509_crt_init(&tls->cacert);
ret = mbedtls_x509_crt_parse(&tls->cacert, cfg->cacert_pem_buf, cfg->cacert_pem_bytes);
if (cfg->use_global_ca_store == true) {
if (global_cacert == NULL) {
ESP_LOGE(TAG, "global_cacert is NULL");
goto exit;
}
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);
} else if (cfg->cacert_pem_buf != NULL) {
tls->cacert_ptr = &tls->cacert;
mbedtls_x509_crt_init(tls->cacert_ptr);
ret = mbedtls_x509_crt_parse(tls->cacert_ptr, cfg->cacert_pem_buf, cfg->cacert_pem_bytes);
if (ret < 0) {
ESP_LOGE(TAG, "mbedtls_x509_crt_parse returned -0x%x\n\n", -ret);
goto exit;
}
mbedtls_ssl_conf_authmode(&tls->conf, MBEDTLS_SSL_VERIFY_REQUIRED);
mbedtls_ssl_conf_ca_chain(&tls->conf, &tls->cacert, NULL);
mbedtls_ssl_conf_ca_chain(&tls->conf, tls->cacert_ptr, NULL);
} else {
mbedtls_ssl_conf_authmode(&tls->conf, MBEDTLS_SSL_VERIFY_NONE);
}
@ -344,7 +397,7 @@ static int esp_tls_low_level_conn(const char *hostname, int hostlen, int port, c
} else {
if (ret != MBEDTLS_ERR_SSL_WANT_READ && ret != MBEDTLS_ERR_SSL_WANT_WRITE) {
ESP_LOGE(TAG, "mbedtls_ssl_handshake returned -0x%x", -ret);
if (cfg->cacert_pem_buf != NULL) {
if (cfg->cacert_pem_buf != NULL || cfg->use_global_ca_store == true) {
/* This is to check whether handshake failed due to invalid certificate*/
verify_certificate(tls);
}

44
components/esp-tls/esp_tls.h
View file

@ -66,6 +66,9 @@ typedef struct esp_tls_cfg {
blocking mode after tls session is established */
int timeout_ms; /*!< Network timeout in milliseconds */
bool use_global_ca_store; /*!< Use a global ca_store for all the connections in which
this bool is set. */
} esp_tls_cfg_t;
/**
@ -88,6 +91,8 @@ typedef struct esp_tls {
mbedtls_x509_crt cacert; /*!< Container for an X.509 certificate */
mbedtls_x509_crt *cacert_ptr; /*!< Pointer to the cacert being used. */
int sockfd; /*!< Underlying socket file descriptor. */
ssize_t (*read)(struct esp_tls *tls, char *data, size_t datalen); /*!< Callback function for reading data from TLS/SSL
@ -232,6 +237,45 @@ void esp_tls_conn_delete(esp_tls_t *tls);
*/
size_t esp_tls_get_bytes_avail(esp_tls_t *tls);
/**
* @brief Create a global CA store with the buffer provided in cfg.
*
* This function should be called if the application wants to use the same CA store for
* multiple connections. The application must call this function before calling esp_tls_conn_new().
*
* @param[in] cacert_pem_buf Buffer which has certificates in pem format. This buffer
* is used for creating a global CA store, which can be used
* by other tls connections.
* @param[in] cacert_pem_bytes Length of the buffer.
*
* @return
* - ESP_OK if creating global CA store was successful.
* - Other if an error occured or an action must be taken by the calling process.
*/
esp_err_t esp_tls_set_global_ca_store(const unsigned char *cacert_pem_buf, const unsigned int cacert_pem_bytes);
/**
* @brief Get the pointer to the global CA store currently being used.
*
* The application must first call esp_tls_set_global_ca_store(). Then the same
* CA store could be used by the application for APIs other than esp_tls.
*
* @note Modifying the pointer might cause a failure in verifying the certificates.
*
* @return
* - Pointer to the global CA store currently being used if successful.
* - NULL if there is no global CA store set.
*/
mbedtls_x509_crt *esp_tls_get_global_ca_store();
/**
* @brief Free the global CA store currently being used.
*
* The memory being used by the global CA store to store all the parsed certificates is
* freed up. The application can call this API if it no longer needs the global CA store.
*/
void esp_tls_free_global_ca_store();
#ifdef __cplusplus
}