esp-mqtt/lib/transport_ssl.c

#include <string.h>
#include <stdlib.h>

#include "mbedtls/platform.h"
#include "mbedtls/net_sockets.h"
#include "mbedtls/esp_debug.h"
#include "mbedtls/ssl.h"
#include "mbedtls/entropy.h"
#include "mbedtls/ctr_drbg.h"
#include "mbedtls/error.h"
#include "mbedtls/certs.h"


#include "esp_log.h"
#include "esp_system.h"

#include "platform.h"
#include "transport.h"
#include "transport_ssl.h"

static const char *TAG = "TRANSPORT_SSL";
/**
 *  mbedtls specific transport data
 */
typedef struct {
    mbedtls_entropy_context  entropy;
    mbedtls_ctr_drbg_context ctr_drbg;
    mbedtls_ssl_context      ctx;
    mbedtls_x509_crt         cacert;
    mbedtls_ssl_config       conf;
    mbedtls_net_context      client_fd;
    void                     *cert_pem_data;
    int                      cert_pem_len;
    bool                     ssl_initialized;
} transport_ssl_t;

static int ssl_connect(transport_handle_t t, const char *host, int port, int timeout_ms)
{
    int ret = -1, flags;
    struct timeval tv;
    transport_ssl_t *ssl = transport_get_data(t);

    if (!ssl) {
        return -1;
    }
    ssl->ssl_initialized = true;
    mbedtls_ssl_init(&ssl->ctx);
    mbedtls_ctr_drbg_init(&ssl->ctr_drbg);
    mbedtls_ssl_config_init(&ssl->conf);
    mbedtls_entropy_init(&ssl->entropy);

    if ((ret = mbedtls_ssl_config_defaults(&ssl->conf,
                                           MBEDTLS_SSL_IS_CLIENT,
                                           MBEDTLS_SSL_TRANSPORT_STREAM,
                                           MBEDTLS_SSL_PRESET_DEFAULT)) != 0) {
        ESP_LOGE(TAG, "mbedtls_ssl_config_defaults returned %d", ret);
        goto exit;
    }

    if ((ret = mbedtls_ctr_drbg_seed(&ssl->ctr_drbg, mbedtls_entropy_func, &ssl->entropy, NULL, 0)) != 0) {
        ESP_LOGE(TAG, "mbedtls_ctr_drbg_seed returned %d", ret);
        goto exit;
    }

    if (ssl->cert_pem_data) {
        mbedtls_x509_crt_init(&ssl->cacert);
        if ((ret = mbedtls_x509_crt_parse(&ssl->cacert, ssl->cert_pem_data, ssl->cert_pem_len + 1)) < 0) {
            ESP_LOGE(TAG, "mbedtls_x509_crt_parse returned -0x%x\n\nDATA=%s,len=%d", -ret, (char*)ssl->cert_pem_data, ssl->cert_pem_len);
            goto exit;
        }
        mbedtls_ssl_conf_ca_chain(&ssl->conf, &ssl->cacert, NULL);
        mbedtls_ssl_conf_authmode(&ssl->conf, MBEDTLS_SSL_VERIFY_REQUIRED);

        if ((ret = mbedtls_ssl_set_hostname(&ssl->ctx, host)) != 0) {
            ESP_LOGE(TAG, "mbedtls_ssl_set_hostname returned -0x%x", -ret);
            goto exit;
        }
    } else {
        mbedtls_ssl_conf_authmode(&ssl->conf, MBEDTLS_SSL_VERIFY_NONE);
    }


    mbedtls_ssl_conf_rng(&ssl->conf, mbedtls_ctr_drbg_random, &ssl->ctr_drbg);

#ifdef CONFIG_MBEDTLS_DEBUG
    mbedtls_esp_enable_debug_log(&ssl->conf, 4);
#endif

    if ((ret = mbedtls_ssl_setup(&ssl->ctx, &ssl->conf)) != 0) {
        ESP_LOGE(TAG, "mbedtls_ssl_setup returned -0x%x\n\n", -ret);
        goto exit;
    }

    mbedtls_net_init(&ssl->client_fd);

    tv.tv_sec = 10; //default timeout is 10 seconds

    if (timeout_ms) {
        tv.tv_sec = timeout_ms;
    }
    tv.tv_usec = 0;
    setsockopt(ssl->client_fd.fd, SOL_SOCKET, SO_RCVTIMEO, &tv, sizeof(tv));
    ESP_LOGD(TAG, "Connect to %s:%d", host, port);
    char port_str[8] = {0};
    sprintf(port_str, "%d", port);
    if ((ret = mbedtls_net_connect(&ssl->client_fd, host, port_str, MBEDTLS_NET_PROTO_TCP)) != 0) {
        ESP_LOGE(TAG, "mbedtls_net_connect returned -%x", -ret);
        goto exit;
    }

    mbedtls_ssl_set_bio(&ssl->ctx, &ssl->client_fd, mbedtls_net_send, mbedtls_net_recv, NULL);

    ESP_LOGD(TAG, "Performing the SSL/TLS handshake...");

    while ((ret = mbedtls_ssl_handshake(&ssl->ctx)) != 0) {
        if (ret != MBEDTLS_ERR_SSL_WANT_READ && ret != MBEDTLS_ERR_SSL_WANT_WRITE) {
            ESP_LOGE(TAG, "mbedtls_ssl_handshake returned -0x%x", -ret);
            goto exit;
        }
    }

    ESP_LOGD(TAG, "Verifying peer X.509 certificate...");

    if ((flags = mbedtls_ssl_get_verify_result(&ssl->ctx)) != 0) {
        /* In real life, we probably want to close connection if ret != 0 */
        ESP_LOGW(TAG, "Failed to verify peer certificate!");
        if (ssl->cert_pem_data) {
            return -1;
        }
        // bzero(buf, sizeof(buf));
        // mbedtls_x509_crt_verify_info(buf, sizeof(buf), "  ! ", flags);
        // ESP_LOGW(TAG, "verification info: %s", buf);
    } else {
        ESP_LOGD(TAG, "Certificate verified.");
    }

    ESP_LOGD(TAG, "Cipher suite is %s", mbedtls_ssl_get_ciphersuite(&ssl->ctx));
exit:

    return ret;
}

static int ssl_poll_read(transport_handle_t t, int timeout_ms)
{
    transport_ssl_t *ssl = transport_get_data(t);
    fd_set readset;
    FD_ZERO(&readset);
    FD_SET(ssl->client_fd.fd, &readset);
    struct timeval timeout;

    timeout.tv_sec = timeout_ms / 1000;
    timeout.tv_usec = (timeout_ms % 1000) * 1000;

    return select(ssl->client_fd.fd + 1, &readset, NULL, NULL, &timeout);
}

static int ssl_poll_write(transport_handle_t t, int timeout_ms)
{
    transport_ssl_t *ssl = transport_get_data(t);
    fd_set writeset;
    FD_ZERO(&writeset);
    FD_SET(ssl->client_fd.fd, &writeset);
    struct timeval timeout;

    timeout.tv_sec = timeout_ms / 1000;
    timeout.tv_usec = (timeout_ms % 1000) * 1000;
    return select(ssl->client_fd.fd + 1, NULL, &writeset, NULL, &timeout);
}

static int ssl_write(transport_handle_t t, char *buffer, int len, int timeout_ms)
{
    int poll, ret;
    transport_ssl_t *ssl = transport_get_data(t);

    if ((poll = transport_poll_write(t, timeout_ms)) <= 0) {
        return poll;
    }
    ret = mbedtls_ssl_write(&ssl->ctx, (const unsigned char *) buffer, len);
    //TODO: Debug here
    return ret;
}

static int ssl_read(transport_handle_t t, char *buffer, int len, int timeout_ms)
{
    int poll = -1, ret;
    transport_ssl_t *ssl = transport_get_data(t);
    if ((poll = transport_poll_read(t, timeout_ms)) <= 0) {
        return poll;
    }
    ret = mbedtls_ssl_read(&ssl->ctx, (unsigned char *)buffer, len);
    if (ret == 0) {
        return -1;
    }
    return ret;
}

static int ssl_close(transport_handle_t t)
{
    int ret = -1;
    transport_ssl_t *ssl = transport_get_data(t);
    if (ssl->ssl_initialized) {
        ESP_LOGD(TAG, "Cleanup mbedtls");
        mbedtls_ssl_close_notify(&ssl->ctx);
        mbedtls_ssl_session_reset(&ssl->ctx);
        mbedtls_net_free(&ssl->client_fd);
        mbedtls_ssl_config_free(&ssl->conf);
        mbedtls_x509_crt_free(&ssl->cacert);
        mbedtls_ctr_drbg_free(&ssl->ctr_drbg);
        mbedtls_entropy_free(&ssl->entropy);
        mbedtls_ssl_free(&ssl->ctx);
        ssl->ssl_initialized = false;
    }
    return ret;
}


static int ssl_destroy(transport_handle_t t)
{
    transport_ssl_t *ssl = transport_get_data(t);
    transport_close(t);
    free(ssl);
    return 0;
}

void transport_ssl_set_cert_data(transport_handle_t t, const char *data, int len)
{
    transport_ssl_t *ssl = transport_get_data(t);
    if (t) {
        if (t && ssl) {
            ssl->cert_pem_data = (void *)data;
            ssl->cert_pem_len = len;
        }
    }
}

transport_handle_t transport_ssl_init()
{
    transport_handle_t t = transport_init();
    transport_ssl_t *ssl = calloc(1, sizeof(transport_ssl_t));
    assert(ssl);
    mbedtls_net_init(&ssl->client_fd);
    transport_set_data(t, ssl);
    transport_set_func(t, ssl_connect, ssl_read, ssl_write, ssl_close, ssl_poll_read, ssl_poll_write, ssl_destroy);
    return t;
}