/*************************************************************************** * _ _ ____ _ * Project ___| | | | _ \| | * / __| | | | |_) | | * | (__| |_| | _ <| |___ * \___|\___/|_| \_\_____| * * Copyright (C) 1998 - 2020, Daniel Stenberg, <daniel@haxx.se>, et al. * * This software is licensed as described in the file COPYING, which * you should have received as part of this distribution. The terms * are also available at https://curl.se/docs/copyright.html. * * You may opt to use, copy, modify, merge, publish, distribute and/or sell * copies of the Software, and permit persons to whom the Software is * furnished to do so, under the terms of the COPYING file. * * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY * KIND, either express or implied. * ***************************************************************************/ /* <DESC> * SMTP example using TLS * </DESC> */ #include <stdio.h> #include <string.h> #include <curl/curl.h> /* This is a simple example showing how to send mail using libcurl's SMTP * capabilities. It builds on the smtp-mail.c example to add authentication * and, more importantly, transport security to protect the authentication * details from being snooped. * * Note that this example requires libcurl 7.20.0 or above. */ #define FROM "<sender@example.org>" #define TO "<addressee@example.net>" #define CC "<info@example.org>" static const char *payload_text[] = { "Date: Mon, 29 Nov 2010 21:54:29 +1100\r\n", "To: " TO "\r\n", "From: " FROM " (Example User)\r\n", "Cc: " CC " (Another example User)\r\n", "Message-ID: <dcd7cb36-11db-487a-9f3a-e652a9458efd@" "rfcpedant.example.org>\r\n", "Subject: SMTP TLS example message\r\n", "\r\n", /* empty line to divide headers from body, see RFC5322 */ "The body of the message starts here.\r\n", "\r\n", "It could be a lot of lines, could be MIME encoded, whatever.\r\n", "Check RFC5322.\r\n", NULL }; struct upload_status { int lines_read; }; static size_t payload_source(char *ptr, size_t size, size_t nmemb, void *userp) { struct upload_status *upload_ctx = (struct upload_status *)userp; const char *data; if((size == 0) || (nmemb == 0) || ((size*nmemb) < 1)) { return 0; } data = payload_text[upload_ctx->lines_read]; if(data) { size_t len = strlen(data); memcpy(ptr, data, len); upload_ctx->lines_read++; return len; } return 0; } int main(void) { CURL *curl; CURLcode res = CURLE_OK; struct curl_slist *recipients = NULL; struct upload_status upload_ctx; upload_ctx.lines_read = 0; curl = curl_easy_init(); if(curl) { /* Set username and password */ curl_easy_setopt(curl, CURLOPT_USERNAME, "user"); curl_easy_setopt(curl, CURLOPT_PASSWORD, "secret"); /* This is the URL for your mailserver. Note the use of port 587 here, * instead of the normal SMTP port (25). Port 587 is commonly used for * secure mail submission (see RFC4403), but you should use whatever * matches your server configuration. */ curl_easy_setopt(curl, CURLOPT_URL, "smtp://mainserver.example.net:587"); /* In this example, we'll start with a plain text connection, and upgrade * to Transport Layer Security (TLS) using the STARTTLS command. Be careful * of using CURLUSESSL_TRY here, because if TLS upgrade fails, the transfer * will continue anyway - see the security discussion in the libcurl * tutorial for more details. */ curl_easy_setopt(curl, CURLOPT_USE_SSL, (long)CURLUSESSL_ALL); /* If your server doesn't have a valid certificate, then you can disable * part of the Transport Layer Security protection by setting the * CURLOPT_SSL_VERIFYPEER and CURLOPT_SSL_VERIFYHOST options to 0 (false). * curl_easy_setopt(curl, CURLOPT_SSL_VERIFYPEER, 0L); * curl_easy_setopt(curl, CURLOPT_SSL_VERIFYHOST, 0L); * That is, in general, a bad idea. It is still better than sending your * authentication details in plain text though. Instead, you should get * the issuer certificate (or the host certificate if the certificate is * self-signed) and add it to the set of certificates that are known to * libcurl using CURLOPT_CAINFO and/or CURLOPT_CAPATH. See docs/SSLCERTS * for more information. */ curl_easy_setopt(curl, CURLOPT_CAINFO, "/path/to/certificate.pem"); /* Note that this option isn't strictly required, omitting it will result * in libcurl sending the MAIL FROM command with empty sender data. All * autoresponses should have an empty reverse-path, and should be directed * to the address in the reverse-path which triggered them. Otherwise, * they could cause an endless loop. See RFC 5321 Section 4.5.5 for more * details. */ curl_easy_setopt(curl, CURLOPT_MAIL_FROM, FROM); /* Add two recipients, in this particular case they correspond to the * To: and Cc: addressees in the header, but they could be any kind of * recipient. */ recipients = curl_slist_append(recipients, TO); recipients = curl_slist_append(recipients, CC); curl_easy_setopt(curl, CURLOPT_MAIL_RCPT, recipients); /* We're using a callback function to specify the payload (the headers and * body of the message). You could just use the CURLOPT_READDATA option to * specify a FILE pointer to read from. */ curl_easy_setopt(curl, CURLOPT_READFUNCTION, payload_source); curl_easy_setopt(curl, CURLOPT_READDATA, &upload_ctx); curl_easy_setopt(curl, CURLOPT_UPLOAD, 1L); /* Since the traffic will be encrypted, it is very useful to turn on debug * information within libcurl to see what is happening during the transfer. */ curl_easy_setopt(curl, CURLOPT_VERBOSE, 1L); /* Send the message */ res = curl_easy_perform(curl); /* Check for errors */ if(res != CURLE_OK) fprintf(stderr, "curl_easy_perform() failed: %s\n", curl_easy_strerror(res)); /* Free the list of recipients */ curl_slist_free_all(recipients); /* Always cleanup */ curl_easy_cleanup(curl); } return (int)res; }