This is based on `ssl_mail_client` from mbedtls. The client also adds functionality to send attachments. Signed-off-by: Vikram Dattu <vikram.dattu@espressif.com>
513 lines
17 KiB
C
513 lines
17 KiB
C
/**
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* SMTP email client
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*
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* Adapted from the `ssl_mail_client` example in mbedtls.
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*
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* Original Copyright (C) 2006-2016, ARM Limited, All Rights Reserved, Apache 2.0 License.
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* Additions Copyright (C) Copyright 2015-2020 Espressif Systems (Shanghai) PTE LTD, Apache 2.0 License.
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*
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#include <string.h>
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#include <stdlib.h>
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#include "freertos/FreeRTOS.h"
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#include "freertos/task.h"
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#include "esp_event.h"
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#include "esp_log.h"
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#include "esp_system.h"
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#include "nvs_flash.h"
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#include "protocol_examples_common.h"
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#include "mbedtls/platform.h"
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#include "mbedtls/net_sockets.h"
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#include "mbedtls/esp_debug.h"
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#include "mbedtls/ssl.h"
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#include "mbedtls/entropy.h"
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#include "mbedtls/ctr_drbg.h"
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#include "mbedtls/error.h"
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#include "mbedtls/certs.h"
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#include <mbedtls/base64.h>
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#include <sys/param.h>
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/* Constants that are configurable in menuconfig */
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#define MAIL_SERVER CONFIG_SMTP_SERVER
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#define MAIL_PORT CONFIG_SMTP_PORT_NUMBER
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#define SENDER_MAIL CONFIG_SMTP_SENDER_MAIL
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#define SENDER_PASSWORD CONFIG_SMTP_SENDER_PASSWORD
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#define RECIPIENT_MAIL CONFIG_SMTP_RECIPIENT_MAIL
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#define SERVER_USES_STARTSSL 1
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static const char *TAG = "smtp_example";
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#define TASK_STACK_SIZE (8 * 1024)
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#define BUF_SIZE 512
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#define VALIDATE_MBEDTLS_RETURN(ret, min_valid_ret, max_valid_ret, goto_label) \
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do { \
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if (ret < min_valid_ret || ret > max_valid_ret) { \
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goto goto_label; \
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} \
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} while (0) \
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/**
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* Root cert for smtp.googlemail.com, taken from server_root_cert.pem
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*
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* The PEM file was extracted from the output of this command:
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* openssl s_client -showcerts -connect smtp.googlemail.com:587 -starttls smtp
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*
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* The CA root cert is the last cert given in the chain of certs.
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*
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* To embed it in the app binary, the PEM file is named
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* in the component.mk COMPONENT_EMBED_TXTFILES variable.
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*/
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extern const uint8_t server_root_cert_pem_start[] asm("_binary_server_root_cert_pem_start");
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extern const uint8_t server_root_cert_pem_end[] asm("_binary_server_root_cert_pem_end");
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extern const uint8_t esp_logo_png_start[] asm("_binary_esp_logo_png_start");
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extern const uint8_t esp_logo_png_end[] asm("_binary_esp_logo_png_end");
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static int write_and_get_response(mbedtls_net_context *sock_fd, unsigned char *buf, size_t len)
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{
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int ret;
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const size_t DATA_SIZE = 128;
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unsigned char data[DATA_SIZE];
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char code[4];
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size_t i, idx = 0;
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if (len) {
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ESP_LOGD(TAG, "%s", buf);
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}
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if (len && (ret = mbedtls_net_send(sock_fd, buf, len)) <= 0) {
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ESP_LOGE(TAG, "mbedtls_net_send failed with error -0x%x", -ret);
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return ret;
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}
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do {
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len = DATA_SIZE - 1;
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ret = mbedtls_net_recv(sock_fd, data, len);
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if (ret <= 0) {
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ESP_LOGE(TAG, "mbedtls_net_recv failed with error -0x%x", -ret);
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goto exit;
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}
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data[len] = '\0';
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printf("\n%s", data);
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len = ret;
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for (i = 0; i < len; i++) {
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if (data[i] != '\n') {
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if (idx < 4) {
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code[idx++] = data[i];
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}
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continue;
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}
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if (idx == 4 && code[0] >= '0' && code[0] <= '9' && code[3] == ' ') {
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code[3] = '\0';
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ret = atoi(code);
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goto exit;
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}
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idx = 0;
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}
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} while (1);
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exit:
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return ret;
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}
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static int write_ssl_and_get_response(mbedtls_ssl_context *ssl, unsigned char *buf, size_t len)
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{
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int ret;
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const size_t DATA_SIZE = 128;
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unsigned char data[DATA_SIZE];
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char code[4];
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size_t i, idx = 0;
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if (len) {
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ESP_LOGD(TAG, "%s", buf);
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}
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while (len && (ret = mbedtls_ssl_write(ssl, buf, len)) <= 0) {
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if (ret != MBEDTLS_ERR_SSL_WANT_READ && ret != MBEDTLS_ERR_SSL_WANT_WRITE) {
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ESP_LOGE(TAG, "mbedtls_ssl_write failed with error -0x%x", -ret);
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goto exit;
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}
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}
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do {
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len = DATA_SIZE - 1;
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ret = mbedtls_ssl_read(ssl, data, len);
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if (ret == MBEDTLS_ERR_SSL_WANT_READ || ret == MBEDTLS_ERR_SSL_WANT_WRITE) {
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continue;
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}
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if (ret <= 0) {
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ESP_LOGE(TAG, "mbedtls_ssl_read failed with error -0x%x", -ret);
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goto exit;
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}
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ESP_LOGD(TAG, "%s", data);
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len = ret;
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for (i = 0; i < len; i++) {
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if (data[i] != '\n') {
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if (idx < 4) {
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code[idx++] = data[i];
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}
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continue;
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}
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if (idx == 4 && code[0] >= '0' && code[0] <= '9' && code[3] == ' ') {
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code[3] = '\0';
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ret = atoi(code);
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goto exit;
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}
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idx = 0;
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}
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} while (1);
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exit:
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return ret;
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}
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static int write_ssl_data(mbedtls_ssl_context *ssl, unsigned char *buf, size_t len)
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{
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int ret;
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if (len) {
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ESP_LOGD(TAG, "%s", buf);
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}
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while (len && (ret = mbedtls_ssl_write(ssl, buf, len)) <= 0) {
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if (ret != MBEDTLS_ERR_SSL_WANT_READ && ret != MBEDTLS_ERR_SSL_WANT_WRITE) {
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ESP_LOGE(TAG, "mbedtls_ssl_write failed with error -0x%x", -ret);
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return ret;
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}
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}
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return 0;
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}
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static int perform_tls_handshake(mbedtls_ssl_context *ssl)
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{
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int ret = -1;
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uint32_t flags;
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char *buf = NULL;
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buf = (char *) calloc(1, BUF_SIZE);
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if (buf == NULL) {
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ESP_LOGE(TAG, "calloc failed for size %d", BUF_SIZE);
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goto exit;
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}
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ESP_LOGI(TAG, "Performing the SSL/TLS handshake...");
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fflush(stdout);
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while ((ret = mbedtls_ssl_handshake(ssl)) != 0) {
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if (ret != MBEDTLS_ERR_SSL_WANT_READ && ret != MBEDTLS_ERR_SSL_WANT_WRITE) {
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ESP_LOGE(TAG, "mbedtls_ssl_handshake returned -0x%x", -ret);
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goto exit;
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}
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}
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ESP_LOGI(TAG, "Verifying peer X.509 certificate...");
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if ((flags = mbedtls_ssl_get_verify_result(ssl)) != 0) {
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/* In real life, we probably want to close connection if ret != 0 */
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ESP_LOGW(TAG, "Failed to verify peer certificate!");
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mbedtls_x509_crt_verify_info(buf, BUF_SIZE, " ! ", flags);
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ESP_LOGW(TAG, "verification info: %s", buf);
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} else {
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ESP_LOGI(TAG, "Certificate verified.");
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}
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ESP_LOGI(TAG, "Cipher suite is %s", mbedtls_ssl_get_ciphersuite(ssl));
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ret = 0; /* No error */
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exit:
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if (buf) {
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free(buf);
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}
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return ret;
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}
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static void smtp_client_task(void *pvParameters)
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{
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char *buf = NULL;
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unsigned char base64_buffer[128];
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int ret, len;
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size_t base64_len;
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mbedtls_entropy_context entropy;
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mbedtls_ctr_drbg_context ctr_drbg;
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mbedtls_ssl_context ssl;
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mbedtls_x509_crt cacert;
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mbedtls_ssl_config conf;
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mbedtls_net_context server_fd;
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mbedtls_ssl_init(&ssl);
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mbedtls_x509_crt_init(&cacert);
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mbedtls_ctr_drbg_init(&ctr_drbg);
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ESP_LOGI(TAG, "Seeding the random number generator");
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mbedtls_ssl_config_init(&conf);
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mbedtls_entropy_init(&entropy);
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if ((ret = mbedtls_ctr_drbg_seed(&ctr_drbg, mbedtls_entropy_func, &entropy,
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NULL, 0)) != 0) {
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ESP_LOGE(TAG, "mbedtls_ctr_drbg_seed returned -0x%x", -ret);
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goto exit;
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}
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ESP_LOGI(TAG, "Loading the CA root certificate...");
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ret = mbedtls_x509_crt_parse(&cacert, server_root_cert_pem_start,
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server_root_cert_pem_end - server_root_cert_pem_start);
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if (ret < 0) {
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ESP_LOGE(TAG, "mbedtls_x509_crt_parse returned -0x%x", -ret);
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goto exit;
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}
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ESP_LOGI(TAG, "Setting hostname for TLS session...");
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/* Hostname set here should match CN in server certificate */
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if ((ret = mbedtls_ssl_set_hostname(&ssl, MAIL_SERVER)) != 0) {
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ESP_LOGE(TAG, "mbedtls_ssl_set_hostname returned -0x%x", -ret);
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goto exit;
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}
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ESP_LOGI(TAG, "Setting up the SSL/TLS structure...");
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if ((ret = mbedtls_ssl_config_defaults(&conf,
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MBEDTLS_SSL_IS_CLIENT,
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MBEDTLS_SSL_TRANSPORT_STREAM,
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MBEDTLS_SSL_PRESET_DEFAULT)) != 0) {
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ESP_LOGE(TAG, "mbedtls_ssl_config_defaults returned -0x%x", -ret);
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goto exit;
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}
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mbedtls_ssl_conf_authmode(&conf, MBEDTLS_SSL_VERIFY_REQUIRED);
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mbedtls_ssl_conf_ca_chain(&conf, &cacert, NULL);
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mbedtls_ssl_conf_rng(&conf, mbedtls_ctr_drbg_random, &ctr_drbg);
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#ifdef CONFIG_MBEDTLS_DEBUG
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mbedtls_esp_enable_debug_log(&conf, 4);
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#endif
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if ((ret = mbedtls_ssl_setup(&ssl, &conf)) != 0) {
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ESP_LOGE(TAG, "mbedtls_ssl_setup returned -0x%x", -ret);
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goto exit;
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}
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mbedtls_net_init(&server_fd);
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ESP_LOGI(TAG, "Connecting to %s:%s...", MAIL_SERVER, MAIL_PORT);
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if ((ret = mbedtls_net_connect(&server_fd, MAIL_SERVER,
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MAIL_PORT, MBEDTLS_NET_PROTO_TCP)) != 0) {
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ESP_LOGE(TAG, "mbedtls_net_connect returned -0x%x", -ret);
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goto exit;
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}
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ESP_LOGI(TAG, "Connected.");
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mbedtls_ssl_set_bio(&ssl, &server_fd, mbedtls_net_send, mbedtls_net_recv, NULL);
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buf = (char *) calloc(1, BUF_SIZE);
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if (buf == NULL) {
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ESP_LOGE(TAG, "calloc failed for size %d", BUF_SIZE);
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goto exit;
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}
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#if SERVER_USES_STARTSSL
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/* Get response */
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ret = write_and_get_response(&server_fd, (unsigned char *) buf, 0);
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VALIDATE_MBEDTLS_RETURN(ret, 200, 299, exit);
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ESP_LOGI(TAG, "Writing EHLO to server...");
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len = snprintf((char *) buf, BUF_SIZE, "EHLO %s\r\n", "ESP32");
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ret = write_and_get_response(&server_fd, (unsigned char *) buf, len);
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VALIDATE_MBEDTLS_RETURN(ret, 200, 299, exit);
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ESP_LOGI(TAG, "Writing STARTTLS to server...");
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len = snprintf((char *) buf, BUF_SIZE, "STARTTLS\r\n");
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ret = write_and_get_response(&server_fd, (unsigned char *) buf, len);
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VALIDATE_MBEDTLS_RETURN(ret, 200, 299, exit);
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ret = perform_tls_handshake(&ssl);
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if (ret != 0) {
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goto exit;
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}
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#else /* SERVER_USES_STARTSSL */
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ret = perform_tls_handshake(&ssl);
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if (ret != 0) {
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goto exit;
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}
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/* Get response */
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ret = write_ssl_and_get_response(&ssl, (unsigned char *) buf, 0);
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VALIDATE_MBEDTLS_RETURN(ret, 200, 299, exit);
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ESP_LOGI(TAG, "Writing EHLO to server...");
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len = snprintf((char *) buf, BUF_SIZE, "EHLO %s\r\n", "ESP32");
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ret = write_ssl_and_get_response(&ssl, (unsigned char *) buf, len);
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VALIDATE_MBEDTLS_RETURN(ret, 200, 299, exit);
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#endif /* SERVER_USES_STARTSSL */
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/* Authentication */
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ESP_LOGI(TAG, "Authentication...");
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ESP_LOGI(TAG, "Write AUTH LOGIN");
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len = snprintf( (char *) buf, BUF_SIZE, "AUTH LOGIN\r\n" );
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ret = write_ssl_and_get_response(&ssl, (unsigned char *) buf, len);
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VALIDATE_MBEDTLS_RETURN(ret, 200, 399, exit);
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ESP_LOGI(TAG, "Write USER NAME");
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ret = mbedtls_base64_encode((unsigned char *) base64_buffer, sizeof(base64_buffer),
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&base64_len, (unsigned char *) SENDER_MAIL, strlen(SENDER_MAIL));
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if (ret != 0) {
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ESP_LOGE(TAG, "Error in mbedtls encode! ret = -0x%x", -ret);
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goto exit;
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}
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len = snprintf((char *) buf, BUF_SIZE, "%s\r\n", base64_buffer);
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ret = write_ssl_and_get_response(&ssl, (unsigned char *) buf, len);
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VALIDATE_MBEDTLS_RETURN(ret, 300, 399, exit);
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ESP_LOGI(TAG, "Write PASSWORD");
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ret = mbedtls_base64_encode((unsigned char *) base64_buffer, sizeof(base64_buffer),
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&base64_len, (unsigned char *) SENDER_PASSWORD, strlen(SENDER_PASSWORD));
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if (ret != 0) {
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ESP_LOGE(TAG, "Error in mbedtls encode! ret = -0x%x", -ret);
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goto exit;
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}
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len = snprintf((char *) buf, BUF_SIZE, "%s\r\n", base64_buffer);
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ret = write_ssl_and_get_response(&ssl, (unsigned char *) buf, len);
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VALIDATE_MBEDTLS_RETURN(ret, 200, 399, exit);
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/* Compose email */
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ESP_LOGI(TAG, "Write MAIL FROM");
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len = snprintf((char *) buf, BUF_SIZE, "MAIL FROM:<%s>\r\n", SENDER_MAIL);
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ret = write_ssl_and_get_response(&ssl, (unsigned char *) buf, len);
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VALIDATE_MBEDTLS_RETURN(ret, 200, 299, exit);
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ESP_LOGI(TAG, "Write RCPT");
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len = snprintf((char *) buf, BUF_SIZE, "RCPT TO:<%s>\r\n", RECIPIENT_MAIL);
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ret = write_ssl_and_get_response(&ssl, (unsigned char *) buf, len);
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VALIDATE_MBEDTLS_RETURN(ret, 200, 299, exit);
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ESP_LOGI(TAG, "Write DATA");
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len = snprintf((char *) buf, BUF_SIZE, "DATA\r\n");
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ret = write_ssl_and_get_response(&ssl, (unsigned char *) buf, len);
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VALIDATE_MBEDTLS_RETURN(ret, 300, 399, exit);
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ESP_LOGI(TAG, "Write Content");
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/* We do not take action if message sending is partly failed. */
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len = snprintf((char *) buf, BUF_SIZE,
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"From: %s\r\nSubject: mbed TLS Test mail\r\n"
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"To: %s\r\n"
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"MIME-Version: 1.0 (mime-construct 1.9)\n",
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"ESP32 SMTP Client", RECIPIENT_MAIL);
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/**
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* Note: We are not validating return for some ssl_writes.
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* If by chance, it's failed; at worst email will be incomplete!
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*/
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ret = write_ssl_data(&ssl, (unsigned char *) buf, len);
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/* Multipart boundary */
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len = snprintf((char *) buf, BUF_SIZE,
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"Content-Type: multipart/mixed;boundary=XYZabcd1234\n"
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"--XYZabcd1234\n");
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ret = write_ssl_data(&ssl, (unsigned char *) buf, len);
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/* Text */
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len = snprintf((char *) buf, BUF_SIZE,
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"Content-Type: text/plain\n"
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"This is a simple test mail from the SMTP client example.\r\n"
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"\r\n"
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"Enjoy!\n\n--XYZabcd1234\n");
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ret = write_ssl_data(&ssl, (unsigned char *) buf, len);
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/* Attachment */
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len = snprintf((char *) buf, BUF_SIZE,
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"Content-Type: image/image/png;name=esp_logo.png\n"
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"Content-Transfer-Encoding: base64\n"
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"Content-Disposition:attachment;filename=\"esp_logo.png\"\n");
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ret = write_ssl_data(&ssl, (unsigned char *) buf, len);
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/* Image contents... */
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const uint8_t *offset = esp_logo_png_start;
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while (offset < esp_logo_png_end - 1) {
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int read_bytes = MIN(((sizeof (base64_buffer) - 1) / 4) * 3, esp_logo_png_end - offset - 1);
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|
ret = mbedtls_base64_encode((unsigned char *) base64_buffer, sizeof(base64_buffer),
|
|
&base64_len, (unsigned char *) offset, read_bytes);
|
|
if (ret != 0) {
|
|
ESP_LOGE(TAG, "Error in mbedtls encode! ret = -0x%x", -ret);
|
|
goto exit;
|
|
}
|
|
offset += read_bytes;
|
|
len = snprintf((char *) buf, BUF_SIZE, "%s\r\n", base64_buffer);
|
|
ret = write_ssl_data(&ssl, (unsigned char *) buf, len);
|
|
}
|
|
|
|
len = snprintf((char *) buf, BUF_SIZE, "\n--XYZabcd1234\n");
|
|
ret = write_ssl_data(&ssl, (unsigned char *) buf, len);
|
|
|
|
len = snprintf((char *) buf, BUF_SIZE, "\r\n.\r\n");
|
|
ret = write_ssl_and_get_response(&ssl, (unsigned char *) buf, len);
|
|
VALIDATE_MBEDTLS_RETURN(ret, 200, 299, exit);
|
|
ESP_LOGI(TAG, "Email sent!");
|
|
|
|
/* Close connection */
|
|
mbedtls_ssl_close_notify(&ssl);
|
|
ret = 0; /* No errors */
|
|
|
|
exit:
|
|
mbedtls_ssl_session_reset(&ssl);
|
|
mbedtls_net_free(&server_fd);
|
|
|
|
if (ret != 0) {
|
|
mbedtls_strerror(ret, buf, 100);
|
|
ESP_LOGE(TAG, "Last error was: -0x%x - %s", -ret, buf);
|
|
}
|
|
|
|
putchar('\n'); /* Just a new line */
|
|
if (buf) {
|
|
free(buf);
|
|
}
|
|
vTaskDelete(NULL);
|
|
}
|
|
|
|
void app_main()
|
|
{
|
|
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(&smtp_client_task, "smtp_client_task", TASK_STACK_SIZE, NULL, 5, NULL);
|
|
}
|