1/*************************************************************************** 2 * _ _ ____ _ 3 * Project ___| | | | _ \| | 4 * / __| | | | |_) | | 5 * | (__| |_| | _ <| |___ 6 * \___|\___/|_| \_\_____| 7 * 8 * Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al. 9 * 10 * This software is licensed as described in the file COPYING, which 11 * you should have received as part of this distribution. The terms 12 * are also available at https://curl.se/docs/copyright.html. 13 * 14 * You may opt to use, copy, modify, merge, publish, distribute and/or sell 15 * copies of the Software, and permit persons to whom the Software is 16 * furnished to do so, under the terms of the COPYING file. 17 * 18 * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY 19 * KIND, either express or implied. 20 * 21 * SPDX-License-Identifier: curl 22 * 23 ***************************************************************************/ 24 25/* <DESC> 26 * Send SMTP email using implicit TLS 27 * </DESC> 28 */ 29 30#include <stdio.h> 31#include <string.h> 32#include <curl/curl.h> 33 34/* This is a simple example showing how to send mail using libcurl's SMTP 35 * capabilities. It builds on the smtp-mail.c example to add authentication 36 * and, more importantly, transport security to protect the authentication 37 * details from being snooped. 38 * 39 * Note that this example requires libcurl 7.20.0 or above. 40 */ 41 42#define FROM_MAIL "<sender@example.com>" 43#define TO_MAIL "<recipient@example.com>" 44#define CC_MAIL "<info@example.com>" 45 46static const char *payload_text = 47 "Date: Mon, 29 Nov 2010 21:54:29 +1100\r\n" 48 "To: " TO_MAIL "\r\n" 49 "From: " FROM_MAIL "\r\n" 50 "Cc: " CC_MAIL "\r\n" 51 "Message-ID: <dcd7cb36-11db-487a-9f3a-e652a9458efd@" 52 "rfcpedant.example.org>\r\n" 53 "Subject: SMTP example message\r\n" 54 "\r\n" /* empty line to divide headers from body, see RFC 5322 */ 55 "The body of the message starts here.\r\n" 56 "\r\n" 57 "It could be a lot of lines, could be MIME encoded, whatever.\r\n" 58 "Check RFC 5322.\r\n"; 59 60struct upload_status { 61 size_t bytes_read; 62}; 63 64static size_t payload_source(char *ptr, size_t size, size_t nmemb, void *userp) 65{ 66 struct upload_status *upload_ctx = (struct upload_status *)userp; 67 const char *data; 68 size_t room = size * nmemb; 69 70 if((size == 0) || (nmemb == 0) || ((size*nmemb) < 1)) { 71 return 0; 72 } 73 74 data = &payload_text[upload_ctx->bytes_read]; 75 76 if(data) { 77 size_t len = strlen(data); 78 if(room < len) 79 len = room; 80 memcpy(ptr, data, len); 81 upload_ctx->bytes_read += len; 82 83 return len; 84 } 85 86 return 0; 87} 88 89int main(void) 90{ 91 CURL *curl; 92 CURLcode res = CURLE_OK; 93 struct curl_slist *recipients = NULL; 94 struct upload_status upload_ctx = { 0 }; 95 96 curl = curl_easy_init(); 97 if(curl) { 98 /* Set username and password */ 99 curl_easy_setopt(curl, CURLOPT_USERNAME, "user"); 100 curl_easy_setopt(curl, CURLOPT_PASSWORD, "secret"); 101 102 /* This is the URL for your mailserver. Note the use of port 587 here, 103 * instead of the normal SMTP port (25). Port 587 is commonly used for 104 * secure mail submission (see RFC 4403), but you should use whatever 105 * matches your server configuration. */ 106 curl_easy_setopt(curl, CURLOPT_URL, "smtp://mainserver.example.net:587"); 107 108 /* In this example, we will start with a plain text connection, and upgrade 109 * to Transport Layer Security (TLS) using the STARTTLS command. Be careful 110 * of using CURLUSESSL_TRY here, because if TLS upgrade fails, the transfer 111 * will continue anyway - see the security discussion in the libcurl 112 * tutorial for more details. */ 113 curl_easy_setopt(curl, CURLOPT_USE_SSL, (long)CURLUSESSL_ALL); 114 115 /* If your server does not have a valid certificate, then you can disable 116 * part of the Transport Layer Security protection by setting the 117 * CURLOPT_SSL_VERIFYPEER and CURLOPT_SSL_VERIFYHOST options to 0 (false). 118 * curl_easy_setopt(curl, CURLOPT_SSL_VERIFYPEER, 0L); 119 * curl_easy_setopt(curl, CURLOPT_SSL_VERIFYHOST, 0L); 120 * That is, in general, a bad idea. It is still better than sending your 121 * authentication details in plain text though. Instead, you should get 122 * the issuer certificate (or the host certificate if the certificate is 123 * self-signed) and add it to the set of certificates that are known to 124 * libcurl using CURLOPT_CAINFO and/or CURLOPT_CAPATH. See docs/SSLCERTS 125 * for more information. */ 126 curl_easy_setopt(curl, CURLOPT_CAINFO, "/path/to/certificate.pem"); 127 128 /* Note that this option is not strictly required, omitting it will result 129 * in libcurl sending the MAIL FROM command with empty sender data. All 130 * autoresponses should have an empty reverse-path, and should be directed 131 * to the address in the reverse-path which triggered them. Otherwise, 132 * they could cause an endless loop. See RFC 5321 Section 4.5.5 for more 133 * details. 134 */ 135 curl_easy_setopt(curl, CURLOPT_MAIL_FROM, FROM_MAIL); 136 137 /* Add two recipients, in this particular case they correspond to the 138 * To: and Cc: addressees in the header, but they could be any kind of 139 * recipient. */ 140 recipients = curl_slist_append(recipients, TO_MAIL); 141 recipients = curl_slist_append(recipients, CC_MAIL); 142 curl_easy_setopt(curl, CURLOPT_MAIL_RCPT, recipients); 143 144 /* We are using a callback function to specify the payload (the headers and 145 * body of the message). You could just use the CURLOPT_READDATA option to 146 * specify a FILE pointer to read from. */ 147 curl_easy_setopt(curl, CURLOPT_READFUNCTION, payload_source); 148 curl_easy_setopt(curl, CURLOPT_READDATA, &upload_ctx); 149 curl_easy_setopt(curl, CURLOPT_UPLOAD, 1L); 150 151 /* Since the traffic will be encrypted, it is useful to turn on debug 152 * information within libcurl to see what is happening during the 153 * transfer. 154 */ 155 curl_easy_setopt(curl, CURLOPT_VERBOSE, 1L); 156 157 /* Send the message */ 158 res = curl_easy_perform(curl); 159 160 /* Check for errors */ 161 if(res != CURLE_OK) 162 fprintf(stderr, "curl_easy_perform() failed: %s\n", 163 curl_easy_strerror(res)); 164 165 /* Free the list of recipients */ 166 curl_slist_free_all(recipients); 167 168 /* Always cleanup */ 169 curl_easy_cleanup(curl); 170 } 171 172 return (int)res; 173} 174