esp-idf/examples/protocols/https_request/main/https_request_example_main.c

/* HTTPS GET Example using plain mbedTLS sockets
 *
 * Contacts the howsmyssl.com API via TLS v1.2 and reads a JSON
 * response.
 *
 * Adapted from the ssl_client1 example in mbedtls.
 *
 * SPDX-FileCopyrightText: 2006-2016 ARM Limited, All Rights Reserved
 *
 * SPDX-License-Identifier: Apache-2.0
 *
 * SPDX-FileContributor: 2015-2022 Espressif Systems (Shanghai) CO LTD
 */

#include <string.h>
#include <stdlib.h>
#include "freertos/FreeRTOS.h"
#include "freertos/task.h"
#include "freertos/event_groups.h"
#include "esp_wifi.h"
#include "esp_event.h"
#include "esp_log.h"
#include "esp_system.h"
#include "nvs_flash.h"
#include "protocol_examples_common.h"
#include "esp_netif.h"

#include "lwip/err.h"
#include "lwip/sockets.h"
#include "lwip/sys.h"
#include "lwip/netdb.h"
#include "lwip/dns.h"

#include "esp_tls.h"
#if CONFIG_MBEDTLS_CERTIFICATE_BUNDLE
#include "esp_crt_bundle.h"
#endif

/* Constants that aren't configurable in menuconfig */
#define WEB_SERVER "www.howsmyssl.com"
#define WEB_PORT "443"
#define WEB_URL "https://www.howsmyssl.com/a/check"

static const char *TAG = "example";

static const char REQUEST[] = "GET " WEB_URL " HTTP/1.1\r\n"
                             "Host: "WEB_SERVER"\r\n"
                             "User-Agent: esp-idf/1.0 esp32\r\n"
                             "\r\n";

/* Root cert for howsmyssl.com, taken from server_root_cert.pem

   The PEM file was extracted from the output of this command:
   openssl s_client -showcerts -connect www.howsmyssl.com:443 </dev/null

   The CA root cert is the last cert given in the chain of certs.

   To embed it in the app binary, the PEM file is named
   in the component.mk COMPONENT_EMBED_TXTFILES variable.
*/
extern const uint8_t server_root_cert_pem_start[] asm("_binary_server_root_cert_pem_start");
extern const uint8_t server_root_cert_pem_end[]   asm("_binary_server_root_cert_pem_end");

static void https_get_request(esp_tls_cfg_t cfg)
{
    char buf[512];
    int ret, len;

    struct esp_tls *tls = esp_tls_conn_http_new(WEB_URL, &cfg);

    if (tls != NULL) {
        ESP_LOGI(TAG, "Connection established...");
    } else {
        ESP_LOGE(TAG, "Connection failed...");
        goto exit;
    }

    size_t written_bytes = 0;
    do {
        ret = esp_tls_conn_write(tls,
                                 REQUEST + written_bytes,
                                 sizeof(REQUEST) - written_bytes);
        if (ret >= 0) {
            ESP_LOGI(TAG, "%d bytes written", ret);
            written_bytes += ret;
        } else if (ret != ESP_TLS_ERR_SSL_WANT_READ  && ret != ESP_TLS_ERR_SSL_WANT_WRITE) {
            ESP_LOGE(TAG, "esp_tls_conn_write  returned: [0x%02X](%s)", ret, esp_err_to_name(ret));
            goto exit;
        }
    } while (written_bytes < sizeof(REQUEST));

    ESP_LOGI(TAG, "Reading HTTP response...");

    do {
        len = sizeof(buf) - 1;
        bzero(buf, sizeof(buf));
        ret = esp_tls_conn_read(tls, (char *)buf, len);

        if (ret == ESP_TLS_ERR_SSL_WANT_WRITE  || ret == ESP_TLS_ERR_SSL_WANT_READ) {
            continue;
        }

        if (ret < 0) {
            ESP_LOGE(TAG, "esp_tls_conn_read  returned [-0x%02X](%s)", -ret, esp_err_to_name(ret));
            break;
        }

        if (ret == 0) {
            ESP_LOGI(TAG, "connection closed");
            break;
        }

        len = ret;
        ESP_LOGD(TAG, "%d bytes read", len);
        /* Print response directly to stdout as it is read */
        for (int i = 0; i < len; i++) {
            putchar(buf[i]);
        }
        putchar('\n'); // JSON output doesn't have a newline at end
    } while (1);

exit:
    esp_tls_conn_delete(tls);
    for (int countdown = 10; countdown >= 0; countdown--) {
        ESP_LOGI(TAG, "%d...", countdown);
        vTaskDelay(1000 / portTICK_PERIOD_MS);
    }
}

#if CONFIG_MBEDTLS_CERTIFICATE_BUNDLE
static void https_get_request_using_crt_bundle(void)
{
    ESP_LOGI(TAG, "https_request using crt bundle");
    esp_tls_cfg_t cfg = {
        .crt_bundle_attach = esp_crt_bundle_attach,
    };
    https_get_request(cfg);
}
#endif // CONFIG_MBEDTLS_CERTIFICATE_BUNDLE

static void https_get_request_using_cacert_buf(void)
{
    ESP_LOGI(TAG, "https_request using cacert_buf");
    esp_tls_cfg_t cfg = {
        .cacert_buf = (const unsigned char *) server_root_cert_pem_start,
        .cacert_bytes = server_root_cert_pem_end - server_root_cert_pem_start,
    };
    https_get_request(cfg);
}

static void https_get_request_using_global_ca_store(void)
{
    esp_err_t esp_ret = ESP_FAIL;
    ESP_LOGI(TAG, "https_request using global ca_store");
    esp_ret = esp_tls_set_global_ca_store(server_root_cert_pem_start, server_root_cert_pem_end - server_root_cert_pem_start);
    if (esp_ret != ESP_OK) {
        ESP_LOGE(TAG, "Error in setting the global ca store: [%02X] (%s),could not complete the https_request using global_ca_store", esp_ret, esp_err_to_name(esp_ret));
        return;
    }
    esp_tls_cfg_t cfg = {
        .use_global_ca_store = true,
    };
    https_get_request(cfg);
    esp_tls_free_global_ca_store();
}

static void https_request_task(void *pvparameters)
{
    ESP_LOGI(TAG, "Start https_request example");

#if CONFIG_MBEDTLS_CERTIFICATE_BUNDLE
    https_get_request_using_crt_bundle();
#endif
    https_get_request_using_cacert_buf();
    https_get_request_using_global_ca_store();

    ESP_LOGI(TAG, "Finish https_request example");
    vTaskDelete(NULL);
}

void app_main(void)
{
    ESP_ERROR_CHECK( nvs_flash_init() );
    ESP_ERROR_CHECK(esp_netif_init());
    ESP_ERROR_CHECK(esp_event_loop_create_default());

    /* This helper function configures Wi-Fi or Ethernet, as selected in menuconfig.
     * Read "Establishing Wi-Fi or Ethernet Connection" section in
     * examples/protocols/README.md for more information about this function.
     */
    ESP_ERROR_CHECK(example_connect());

    xTaskCreate(&https_request_task, "https_get_task", 8192, NULL, 5, NULL);
}