Annotation of embedaddon/curl/docs/examples/smtp-tls.c, revision 1.1

1.1     ! misho       1: /***************************************************************************
        !             2:  *                                  _   _ ____  _
        !             3:  *  Project                     ___| | | |  _ \| |
        !             4:  *                             / __| | | | |_) | |
        !             5:  *                            | (__| |_| |  _ <| |___
        !             6:  *                             \___|\___/|_| \_\_____|
        !             7:  *
        !             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.
        !            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:  ***************************************************************************/
        !            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: }

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