1 /***************************************************************************
2 * _ _ ____ _
3 * Project ___| | | | _ \| |
4 * / __| | | | |_) | |
5 * | (__| |_| | _ <| |___
6 * \___|\___/|_| \_\_____|
7 *
8 * Copyright (C) 1998 - 2021, 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 ***************************************************************************/
22
23 /* <DESC>
24 * Send e-mail on behalf of another user with SMTP
25 * </DESC>
26 */
27
28 #include <stdio.h>
29 #include <string.h>
30 #include <curl/curl.h>
31
32 /*
33 * This is a simple example show how to send an email using libcurl's SMTP
34 * capabilities.
35 *
36 * Note that this example requires libcurl 7.66.0 or above.
37 */
38
39 /* The libcurl options want plain addresses, the viewable headers in the mail
40 * can very well get a full name as well.
41 */
42 #define FROM_ADDR "<ursel@example.org>"
43 #define SENDER_ADDR "<kurt@example.org>"
44 #define TO_ADDR "<addressee@example.net>"
45
46 #define FROM_MAIL "Ursel " FROM_ADDR
47 #define SENDER_MAIL "Kurt " SENDER_ADDR
48 #define TO_MAIL "A Receiver " TO_ADDR
49
50 static const char *payload_text =
51 "Date: Mon, 29 Nov 2010 21:54:29 +1100\r\n"
52 "To: " TO_MAIL "\r\n"
53 "From: " FROM_MAIL "\r\n"
54 "Sender: " SENDER_MAIL "\r\n"
55 "Message-ID: <dcd7cb36-11db-487a-9f3a-e652a9458efd@"
56 "rfcpedant.example.org>\r\n"
57 "Subject: SMTP example message\r\n"
58 "\r\n" /* empty line to divide headers from body, see RFC5322 */
59 "The body of the message starts here.\r\n"
60 "\r\n"
61 "It could be a lot of lines, could be MIME encoded, whatever.\r\n"
62 "Check RFC5322.\r\n";
63
64 struct upload_status {
65 size_t bytes_read;
66 };
67
payload_source(char * ptr,size_t size,size_t nmemb,void * userp)68 static size_t payload_source(char *ptr, size_t size, size_t nmemb, void *userp)
69 {
70 struct upload_status *upload_ctx = (struct upload_status *)userp;
71 const char *data;
72 size_t room = size * nmemb;
73
74 if((size == 0) || (nmemb == 0) || ((size*nmemb) < 1)) {
75 return 0;
76 }
77
78 data = &payload_text[upload_ctx->bytes_read];
79
80 if(data) {
81 size_t len = strlen(data);
82 if(room < len)
83 len = room;
84 memcpy(ptr, data, len);
85 upload_ctx->bytes_read += len;
86
87 return len;
88 }
89
90 return 0;
91 }
92
main(void)93 int main(void)
94 {
95 CURL *curl;
96 CURLcode res = CURLE_OK;
97 struct curl_slist *recipients = NULL;
98 struct upload_status upload_ctx = { 0 };
99
100 curl = curl_easy_init();
101 if(curl) {
102 /* This is the URL for your mailserver. In this example we connect to the
103 smtp-submission port as we require an authenticated connection. */
104 curl_easy_setopt(curl, CURLOPT_URL, "smtp://mail.example.com:587");
105
106 /* Set the username and password */
107 curl_easy_setopt(curl, CURLOPT_USERNAME, "kurt");
108 curl_easy_setopt(curl, CURLOPT_PASSWORD, "xipj3plmq");
109
110 /* Set the authorisation identity (identity to act as) */
111 curl_easy_setopt(curl, CURLOPT_SASL_AUTHZID, "ursel");
112
113 /* Force PLAIN authentication */
114 curl_easy_setopt(curl, CURLOPT_LOGIN_OPTIONS, "AUTH=PLAIN");
115
116 /* Note that this option isn't strictly required, omitting it will result
117 * in libcurl sending the MAIL FROM command with empty sender data. All
118 * autoresponses should have an empty reverse-path, and should be directed
119 * to the address in the reverse-path which triggered them. Otherwise,
120 * they could cause an endless loop. See RFC 5321 Section 4.5.5 for more
121 * details.
122 */
123 curl_easy_setopt(curl, CURLOPT_MAIL_FROM, FROM_ADDR);
124
125 /* Add a recipient, in this particular case it corresponds to the
126 * To: addressee in the header. */
127 recipients = curl_slist_append(recipients, TO_ADDR);
128 curl_easy_setopt(curl, CURLOPT_MAIL_RCPT, recipients);
129
130 /* We're using a callback function to specify the payload (the headers and
131 * body of the message). You could just use the CURLOPT_READDATA option to
132 * specify a FILE pointer to read from. */
133 curl_easy_setopt(curl, CURLOPT_READFUNCTION, payload_source);
134 curl_easy_setopt(curl, CURLOPT_READDATA, &upload_ctx);
135 curl_easy_setopt(curl, CURLOPT_UPLOAD, 1L);
136
137 /* Send the message */
138 res = curl_easy_perform(curl);
139
140 /* Check for errors */
141 if(res != CURLE_OK)
142 fprintf(stderr, "curl_easy_perform() failed: %s\n",
143 curl_easy_strerror(res));
144
145 /* Free the list of recipients */
146 curl_slist_free_all(recipients);
147
148 /* curl won't send the QUIT command until you call cleanup, so you should
149 * be able to re-use this connection for additional messages (setting
150 * CURLOPT_MAIL_FROM and CURLOPT_MAIL_RCPT as required, and calling
151 * curl_easy_perform() again. It may not be a good idea to keep the
152 * connection open for a very long time though (more than a few minutes
153 * may result in the server timing out the connection), and you do want to
154 * clean up in the end.
155 */
156 curl_easy_cleanup(curl);
157 }
158
159 return (int)res;
160 }
161