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 * SMTP example using SSL
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_MAIL "<sender@example.com>"
41 #define TO_MAIL "<recipient@example.com>"
42 #define CC_MAIL "<info@example.com>"
43
44 static const char *payload_text =
45 "Date: Mon, 29 Nov 2010 21:54:29 +1100\r\n"
46 "To: " TO_MAIL "\r\n"
47 "From: " FROM_MAIL "\r\n"
48 "Cc: " CC_MAIL "\r\n"
49 "Message-ID: <dcd7cb36-11db-487a-9f3a-e652a9458efd@"
50 "rfcpedant.example.org>\r\n"
51 "Subject: SMTP 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
58 struct upload_status {
59 size_t bytes_read;
60 };
61
payload_source(char * ptr,size_t size,size_t nmemb,void * userp)62 static size_t payload_source(char *ptr, size_t size, size_t nmemb, void *userp)
63 {
64 struct upload_status *upload_ctx = (struct upload_status *)userp;
65 const char *data;
66 size_t room = size * nmemb;
67
68 if((size == 0) || (nmemb == 0) || ((size*nmemb) < 1)) {
69 return 0;
70 }
71
72 data = &payload_text[upload_ctx->bytes_read];
73
74 if(data) {
75 size_t len = strlen(data);
76 if(room < len)
77 len = room;
78 memcpy(ptr, data, len);
79 upload_ctx->bytes_read += len;
80
81 return len;
82 }
83
84 return 0;
85 }
86
main(void)87 int main(void)
88 {
89 CURL *curl;
90 CURLcode res = CURLE_OK;
91 struct curl_slist *recipients = NULL;
92 struct upload_status upload_ctx = { 0 };
93
94 curl = curl_easy_init();
95 if(curl) {
96 /* Set username and password */
97 curl_easy_setopt(curl, CURLOPT_USERNAME, "user");
98 curl_easy_setopt(curl, CURLOPT_PASSWORD, "secret");
99
100 /* This is the URL for your mailserver. Note the use of smtps:// rather
101 * than smtp:// to request a SSL based connection. */
102 curl_easy_setopt(curl, CURLOPT_URL, "smtps://mainserver.example.net");
103
104 /* If you want to connect to a site who isn't using a certificate that is
105 * signed by one of the certs in the CA bundle you have, you can skip the
106 * verification of the server's certificate. This makes the connection
107 * A LOT LESS SECURE.
108 *
109 * If you have a CA cert for the server stored someplace else than in the
110 * default bundle, then the CURLOPT_CAPATH option might come handy for
111 * you. */
112 #ifdef SKIP_PEER_VERIFICATION
113 curl_easy_setopt(curl, CURLOPT_SSL_VERIFYPEER, 0L);
114 #endif
115
116 /* If the site you're connecting to uses a different host name that what
117 * they have mentioned in their server certificate's commonName (or
118 * subjectAltName) fields, libcurl will refuse to connect. You can skip
119 * this check, but this will make the connection less secure. */
120 #ifdef SKIP_HOSTNAME_VERIFICATION
121 curl_easy_setopt(curl, CURLOPT_SSL_VERIFYHOST, 0L);
122 #endif
123
124 /* Note that this option isn't strictly required, omitting it will result
125 * in libcurl sending the MAIL FROM command with empty sender data. All
126 * autoresponses should have an empty reverse-path, and should be directed
127 * to the address in the reverse-path which triggered them. Otherwise,
128 * they could cause an endless loop. See RFC 5321 Section 4.5.5 for more
129 * details.
130 */
131 curl_easy_setopt(curl, CURLOPT_MAIL_FROM, FROM_MAIL);
132
133 /* Add two recipients, in this particular case they correspond to the
134 * To: and Cc: addressees in the header, but they could be any kind of
135 * recipient. */
136 recipients = curl_slist_append(recipients, TO_MAIL);
137 recipients = curl_slist_append(recipients, CC_MAIL);
138 curl_easy_setopt(curl, CURLOPT_MAIL_RCPT, recipients);
139
140 /* We're using a callback function to specify the payload (the headers and
141 * body of the message). You could just use the CURLOPT_READDATA option to
142 * specify a FILE pointer to read from. */
143 curl_easy_setopt(curl, CURLOPT_READFUNCTION, payload_source);
144 curl_easy_setopt(curl, CURLOPT_READDATA, &upload_ctx);
145 curl_easy_setopt(curl, CURLOPT_UPLOAD, 1L);
146
147 /* Since the traffic will be encrypted, it is very useful to turn on debug
148 * information within libcurl to see what is happening during the
149 * transfer */
150 curl_easy_setopt(curl, CURLOPT_VERBOSE, 1L);
151
152 /* Send the message */
153 res = curl_easy_perform(curl);
154
155 /* Check for errors */
156 if(res != CURLE_OK)
157 fprintf(stderr, "curl_easy_perform() failed: %s\n",
158 curl_easy_strerror(res));
159
160 /* Free the list of recipients */
161 curl_slist_free_all(recipients);
162
163 /* Always cleanup */
164 curl_easy_cleanup(curl);
165 }
166
167 return (int)res;
168 }
169