smtp-tls.c 6.2 KB

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  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. /* <DESC>
  25. * Send SMTP email using implicit TLS
  26. * </DESC>
  27. */
  28. #include <stdio.h>
  29. #include <string.h>
  30. #include <curl/curl.h>
  31. /* This is a simple example showing how to send mail using libcurl's SMTP
  32. * capabilities. It builds on the smtp-mail.c example to add authentication
  33. * and, more importantly, transport security to protect the authentication
  34. * details from being snooped.
  35. *
  36. * Note that this example requires libcurl 7.20.0 or above.
  37. */
  38. #define FROM_MAIL "<sender@example.com>"
  39. #define TO_MAIL "<recipient@example.com>"
  40. #define CC_MAIL "<info@example.com>"
  41. static const char *payload_text =
  42. "Date: Mon, 29 Nov 2010 21:54:29 +1100\r\n"
  43. "To: " TO_MAIL "\r\n"
  44. "From: " FROM_MAIL "\r\n"
  45. "Cc: " CC_MAIL "\r\n"
  46. "Message-ID: <dcd7cb36-11db-487a-9f3a-e652a9458efd@"
  47. "rfcpedant.example.org>\r\n"
  48. "Subject: SMTP example message\r\n"
  49. "\r\n" /* empty line to divide headers from body, see RFC 5322 */
  50. "The body of the message starts here.\r\n"
  51. "\r\n"
  52. "It could be a lot of lines, could be MIME encoded, whatever.\r\n"
  53. "Check RFC 5322.\r\n";
  54. struct upload_status {
  55. size_t bytes_read;
  56. };
  57. static size_t payload_source(char *ptr, size_t size, size_t nmemb, void *userp)
  58. {
  59. struct upload_status *upload_ctx = (struct upload_status *)userp;
  60. const char *data;
  61. size_t room = size * nmemb;
  62. if((size == 0) || (nmemb == 0) || ((size*nmemb) < 1)) {
  63. return 0;
  64. }
  65. data = &payload_text[upload_ctx->bytes_read];
  66. if(data) {
  67. size_t len = strlen(data);
  68. if(room < len)
  69. len = room;
  70. memcpy(ptr, data, len);
  71. upload_ctx->bytes_read += len;
  72. return len;
  73. }
  74. return 0;
  75. }
  76. int main(void)
  77. {
  78. CURL *curl;
  79. CURLcode res = CURLE_OK;
  80. struct curl_slist *recipients = NULL;
  81. struct upload_status upload_ctx = { 0 };
  82. curl = curl_easy_init();
  83. if(curl) {
  84. /* Set username and password */
  85. curl_easy_setopt(curl, CURLOPT_USERNAME, "user");
  86. curl_easy_setopt(curl, CURLOPT_PASSWORD, "secret");
  87. /* This is the URL for your mailserver. Note the use of port 587 here,
  88. * instead of the normal SMTP port (25). Port 587 is commonly used for
  89. * secure mail submission (see RFC 4403), but you should use whatever
  90. * matches your server configuration. */
  91. curl_easy_setopt(curl, CURLOPT_URL, "smtp://mainserver.example.net:587");
  92. /* In this example, we start with a plain text connection, and upgrade to
  93. * Transport Layer Security (TLS) using the STARTTLS command. Be careful
  94. * of using CURLUSESSL_TRY here, because if TLS upgrade fails, the
  95. * transfer continues anyway - see the security discussion in the libcurl
  96. * tutorial for more details. */
  97. curl_easy_setopt(curl, CURLOPT_USE_SSL, (long)CURLUSESSL_ALL);
  98. /* If your server does not have a valid certificate, then you can disable
  99. * part of the Transport Layer Security protection by setting the
  100. * CURLOPT_SSL_VERIFYPEER and CURLOPT_SSL_VERIFYHOST options to 0 (false).
  101. * curl_easy_setopt(curl, CURLOPT_SSL_VERIFYPEER, 0L);
  102. * curl_easy_setopt(curl, CURLOPT_SSL_VERIFYHOST, 0L);
  103. * That is, in general, a bad idea. It is still better than sending your
  104. * authentication details in plain text though. Instead, you should get
  105. * the issuer certificate (or the host certificate if the certificate is
  106. * self-signed) and add it to the set of certificates that are known to
  107. * libcurl using CURLOPT_CAINFO and/or CURLOPT_CAPATH. See docs/SSLCERTS
  108. * for more information. */
  109. curl_easy_setopt(curl, CURLOPT_CAINFO, "/path/to/certificate.pem");
  110. /* Note that this option is not strictly required, omitting it results in
  111. * libcurl sending the MAIL FROM command with empty sender data. All
  112. * autoresponses should have an empty reverse-path, and should be directed
  113. * to the address in the reverse-path which triggered them. Otherwise,
  114. * they could cause an endless loop. See RFC 5321 Section 4.5.5 for more
  115. * details.
  116. */
  117. curl_easy_setopt(curl, CURLOPT_MAIL_FROM, FROM_MAIL);
  118. /* Add two recipients, in this particular case they correspond to the
  119. * To: and Cc: addressees in the header, but they could be any kind of
  120. * recipient. */
  121. recipients = curl_slist_append(recipients, TO_MAIL);
  122. recipients = curl_slist_append(recipients, CC_MAIL);
  123. curl_easy_setopt(curl, CURLOPT_MAIL_RCPT, recipients);
  124. /* We are using a callback function to specify the payload (the headers and
  125. * body of the message). You could just use the CURLOPT_READDATA option to
  126. * specify a FILE pointer to read from. */
  127. curl_easy_setopt(curl, CURLOPT_READFUNCTION, payload_source);
  128. curl_easy_setopt(curl, CURLOPT_READDATA, &upload_ctx);
  129. curl_easy_setopt(curl, CURLOPT_UPLOAD, 1L);
  130. /* Since the traffic is encrypted, it is useful to turn on debug
  131. * information within libcurl to see what is happening during the
  132. * transfer.
  133. */
  134. curl_easy_setopt(curl, CURLOPT_VERBOSE, 1L);
  135. /* Send the message */
  136. res = curl_easy_perform(curl);
  137. /* Check for errors */
  138. if(res != CURLE_OK)
  139. fprintf(stderr, "curl_easy_perform() failed: %s\n",
  140. curl_easy_strerror(res));
  141. /* Free the list of recipients */
  142. curl_slist_free_all(recipients);
  143. /* Always cleanup */
  144. curl_easy_cleanup(curl);
  145. }
  146. return (int)res;
  147. }