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    8:  * Copyright (C) 1998 - 2019, 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.haxx.se/docs/copyright.html.
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   17:  *
   18:  * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
   19:  * KIND, either express or implied.
   20:  *
   21:  ***************************************************************************/
   22: 
   23: /* <DESC>
   24:  * SMTP example using TLS
   25:  * </DESC>
   26:  */
   27: 
   28: #include <stdio.h>
   29: #include <string.h>
   30: #include <curl/curl.h>
   31: 
   32: /* This is a simple example showing how to send mail using libcurl's SMTP
   33:  * capabilities. It builds on the smtp-mail.c example to add authentication
   34:  * and, more importantly, transport security to protect the authentication
   35:  * details from being snooped.
   36:  *
   37:  * Note that this example requires libcurl 7.20.0 or above.
   38:  */
   39: 
   40: #define FROM    "<sender@example.org>"
   41: #define TO      "<addressee@example.net>"
   42: #define CC      "<info@example.org>"
   43: 
   44: static const char *payload_text[] = {
   45:   "Date: Mon, 29 Nov 2010 21:54:29 +1100\r\n",
   46:   "To: " TO "\r\n",
   47:   "From: " FROM " (Example User)\r\n",
   48:   "Cc: " CC " (Another example User)\r\n",
   49:   "Message-ID: <dcd7cb36-11db-487a-9f3a-e652a9458efd@"
   50:   "rfcpedant.example.org>\r\n",
   51:   "Subject: SMTP TLS example message\r\n",
   52:   "\r\n", /* empty line to divide headers from body, see RFC5322 */
   53:   "The body of the message starts here.\r\n",
   54:   "\r\n",
   55:   "It could be a lot of lines, could be MIME encoded, whatever.\r\n",
   56:   "Check RFC5322.\r\n",
   57:   NULL
   58: };
   59: 
   60: struct upload_status {
   61:   int lines_read;
   62: };
   63: 
   64: static size_t payload_source(void *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: 
   69:   if((size == 0) || (nmemb == 0) || ((size*nmemb) < 1)) {
   70:     return 0;
   71:   }
   72: 
   73:   data = payload_text[upload_ctx->lines_read];
   74: 
   75:   if(data) {
   76:     size_t len = strlen(data);
   77:     memcpy(ptr, data, len);
   78:     upload_ctx->lines_read++;
   79: 
   80:     return len;
   81:   }
   82: 
   83:   return 0;
   84: }
   85: 
   86: int main(void)
   87: {
   88:   CURL *curl;
   89:   CURLcode res = CURLE_OK;
   90:   struct curl_slist *recipients = NULL;
   91:   struct upload_status upload_ctx;
   92: 
   93:   upload_ctx.lines_read = 0;
   94: 
   95:   curl = curl_easy_init();
   96:   if(curl) {
   97:     /* Set username and password */
   98:     curl_easy_setopt(curl, CURLOPT_USERNAME, "user");
   99:     curl_easy_setopt(curl, CURLOPT_PASSWORD, "secret");
  100: 
  101:     /* This is the URL for your mailserver. Note the use of port 587 here,
  102:      * instead of the normal SMTP port (25). Port 587 is commonly used for
  103:      * secure mail submission (see RFC4403), but you should use whatever
  104:      * matches your server configuration. */
  105:     curl_easy_setopt(curl, CURLOPT_URL, "smtp://mainserver.example.net:587");
  106: 
  107:     /* In this example, we'll start with a plain text connection, and upgrade
  108:      * to Transport Layer Security (TLS) using the STARTTLS command. Be careful
  109:      * of using CURLUSESSL_TRY here, because if TLS upgrade fails, the transfer
  110:      * will continue anyway - see the security discussion in the libcurl
  111:      * tutorial for more details. */
  112:     curl_easy_setopt(curl, CURLOPT_USE_SSL, (long)CURLUSESSL_ALL);
  113: 
  114:     /* If your server doesn't have a valid certificate, then you can disable
  115:      * part of the Transport Layer Security protection by setting the
  116:      * CURLOPT_SSL_VERIFYPEER and CURLOPT_SSL_VERIFYHOST options to 0 (false).
  117:      *   curl_easy_setopt(curl, CURLOPT_SSL_VERIFYPEER, 0L);
  118:      *   curl_easy_setopt(curl, CURLOPT_SSL_VERIFYHOST, 0L);
  119:      * That is, in general, a bad idea. It is still better than sending your
  120:      * authentication details in plain text though.  Instead, you should get
  121:      * the issuer certificate (or the host certificate if the certificate is
  122:      * self-signed) and add it to the set of certificates that are known to
  123:      * libcurl using CURLOPT_CAINFO and/or CURLOPT_CAPATH. See docs/SSLCERTS
  124:      * for more information. */
  125:     curl_easy_setopt(curl, CURLOPT_CAINFO, "/path/to/certificate.pem");
  126: 
  127:     /* Note that this option isn't strictly required, omitting it will result
  128:      * in libcurl sending the MAIL FROM command with empty sender data. All
  129:      * autoresponses should have an empty reverse-path, and should be directed
  130:      * to the address in the reverse-path which triggered them. Otherwise,
  131:      * they could cause an endless loop. See RFC 5321 Section 4.5.5 for more
  132:      * details.
  133:      */
  134:     curl_easy_setopt(curl, CURLOPT_MAIL_FROM, FROM);
  135: 
  136:     /* Add two recipients, in this particular case they correspond to the
  137:      * To: and Cc: addressees in the header, but they could be any kind of
  138:      * recipient. */
  139:     recipients = curl_slist_append(recipients, TO);
  140:     recipients = curl_slist_append(recipients, CC);
  141:     curl_easy_setopt(curl, CURLOPT_MAIL_RCPT, recipients);
  142: 
  143:     /* We're using a callback function to specify the payload (the headers and
  144:      * body of the message). You could just use the CURLOPT_READDATA option to
  145:      * specify a FILE pointer to read from. */
  146:     curl_easy_setopt(curl, CURLOPT_READFUNCTION, payload_source);
  147:     curl_easy_setopt(curl, CURLOPT_READDATA, &upload_ctx);
  148:     curl_easy_setopt(curl, CURLOPT_UPLOAD, 1L);
  149: 
  150:     /* Since the traffic will be encrypted, it is very useful to turn on debug
  151:      * information within libcurl to see what is happening during the transfer.
  152:      */
  153:     curl_easy_setopt(curl, CURLOPT_VERBOSE, 1L);
  154: 
  155:     /* Send the message */
  156:     res = curl_easy_perform(curl);
  157: 
  158:     /* Check for errors */
  159:     if(res != CURLE_OK)
  160:       fprintf(stderr, "curl_easy_perform() failed: %s\n",
  161:               curl_easy_strerror(res));
  162: 
  163:     /* Free the list of recipients */
  164:     curl_slist_free_all(recipients);
  165: 
  166:     /* Always cleanup */
  167:     curl_easy_cleanup(curl);
  168:   }
  169: 
  170:   return (int)res;
  171: }