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
25/* <DESC>
26 * Send email on behalf of another user with SMTP
27 * </DESC>
28 */
29
30#include <stdio.h>
31#include <string.h>
32#include <curl/curl.h>
33
34/*
35 * This is a simple example show how to send an email using libcurl's SMTP
36 * capabilities.
37 *
38 * Note that this example requires libcurl 7.66.0 or above.
39 */
40
41/* The libcurl options want plain addresses, the viewable headers in the mail
42 * can get a full name as well.
43 */
44#define FROM_ADDR    "<ursel@example.org>"
45#define SENDER_ADDR  "<kurt@example.org>"
46#define TO_ADDR      "<addressee@example.net>"
47
48#define FROM_MAIL    "Ursel " FROM_ADDR
49#define SENDER_MAIL  "Kurt " SENDER_ADDR
50#define TO_MAIL      "A Receiver " TO_ADDR
51
52static const char *payload_text =
53  "Date: Mon, 29 Nov 2010 21:54:29 +1100\r\n"
54  "To: " TO_MAIL "\r\n"
55  "From: " FROM_MAIL "\r\n"
56  "Sender: " SENDER_MAIL "\r\n"
57  "Message-ID: <dcd7cb36-11db-487a-9f3a-e652a9458efd@"
58  "rfcpedant.example.org>\r\n"
59  "Subject: SMTP example message\r\n"
60  "\r\n" /* empty line to divide headers from body, see RFC 5322 */
61  "The body of the message starts here.\r\n"
62  "\r\n"
63  "It could be a lot of lines, could be MIME encoded, whatever.\r\n"
64  "Check RFC 5322.\r\n";
65
66struct upload_status {
67  size_t bytes_read;
68};
69
70static size_t payload_source(char *ptr, size_t size, size_t nmemb, void *userp)
71{
72  struct upload_status *upload_ctx = (struct upload_status *)userp;
73  const char *data;
74  size_t room = size * nmemb;
75
76  if((size == 0) || (nmemb == 0) || ((size*nmemb) < 1)) {
77    return 0;
78  }
79
80  data = &payload_text[upload_ctx->bytes_read];
81
82  if(data) {
83    size_t len = strlen(data);
84    if(room < len)
85      len = room;
86    memcpy(ptr, data, len);
87    upload_ctx->bytes_read += len;
88
89    return len;
90  }
91
92  return 0;
93}
94
95int main(void)
96{
97  CURL *curl;
98  CURLcode res = CURLE_OK;
99  struct curl_slist *recipients = NULL;
100  struct upload_status upload_ctx = { 0 };
101
102  curl = curl_easy_init();
103  if(curl) {
104    /* This is the URL for your mailserver. In this example we connect to the
105       smtp-submission port as we require an authenticated connection. */
106    curl_easy_setopt(curl, CURLOPT_URL, "smtp://mail.example.com:587");
107
108    /* Set the username and password */
109    curl_easy_setopt(curl, CURLOPT_USERNAME, "kurt");
110    curl_easy_setopt(curl, CURLOPT_PASSWORD, "xipj3plmq");
111
112    /* Set the authorization identity (identity to act as) */
113    curl_easy_setopt(curl, CURLOPT_SASL_AUTHZID, "ursel");
114
115    /* Force PLAIN authentication */
116    curl_easy_setopt(curl, CURLOPT_LOGIN_OPTIONS, "AUTH=PLAIN");
117
118    /* Note that this option is not strictly required, omitting it will result
119     * in libcurl sending the MAIL FROM command with empty sender data. All
120     * autoresponses should have an empty reverse-path, and should be directed
121     * to the address in the reverse-path which triggered them. Otherwise,
122     * they could cause an endless loop. See RFC 5321 Section 4.5.5 for more
123     * details.
124     */
125    curl_easy_setopt(curl, CURLOPT_MAIL_FROM, FROM_ADDR);
126
127    /* Add a recipient, in this particular case it corresponds to the
128     * To: addressee in the header. */
129    recipients = curl_slist_append(recipients, TO_ADDR);
130    curl_easy_setopt(curl, CURLOPT_MAIL_RCPT, recipients);
131
132    /* We are using a callback function to specify the payload (the headers and
133     * body of the message). You could just use the CURLOPT_READDATA option to
134     * specify a FILE pointer to read from. */
135    curl_easy_setopt(curl, CURLOPT_READFUNCTION, payload_source);
136    curl_easy_setopt(curl, CURLOPT_READDATA, &upload_ctx);
137    curl_easy_setopt(curl, CURLOPT_UPLOAD, 1L);
138
139    /* Send the message */
140    res = curl_easy_perform(curl);
141
142    /* Check for errors */
143    if(res != CURLE_OK)
144      fprintf(stderr, "curl_easy_perform() failed: %s\n",
145              curl_easy_strerror(res));
146
147    /* Free the list of recipients */
148    curl_slist_free_all(recipients);
149
150    /* curl will not send the QUIT command until you call cleanup, so you
151     * should be able to reuse this connection for additional messages
152     * (setting CURLOPT_MAIL_FROM and CURLOPT_MAIL_RCPT as required, and
153     * calling curl_easy_perform() again. It may not be a good idea to keep
154     * the connection open for a long time though (more than a few minutes may
155     * result in the server timing out the connection), and you do want to
156     * clean up in the end.
157     */
158    curl_easy_cleanup(curl);
159  }
160
161  return (int)res;
162}
163