1/***************************************************************************
2 *                                  _   _ ____  _
3 *  Project                     ___| | | |  _ \| |
4 *                             / __| | | | |_) | |
5 *                            | (__| |_| |  _ <| |___
6 *                             \___|\___/|_| \_\_____|
7 *
8 * Copyright (C) 1998 - 2016, 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
44static 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
60struct upload_status {
61  int lines_read;
62};
63
64static 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
86int 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}
172