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8  * Copyright (C) 1998 - 2016, Daniel Stenberg, <daniel@haxx.se>, et al.
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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 
payload_source(void * ptr,size_t size,size_t nmemb,void * userp)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 
main(void)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 }
172