aboutsummaryrefslogtreecommitdiff
path: root/docs/examples/smtp-tls.c
blob: 1ab7e205bcfd6cc64bb7fa3292fe0922d94c2f39 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
/***************************************************************************
 *                                  _   _ ____  _
 *  Project                     ___| | | |  _ \| |
 *                             / __| | | | |_) | |
 *                            | (__| |_| |  _ <| |___
 *                             \___|\___/|_| \_\_____|
 *
 * Copyright (C) 1998 - 2014, Daniel Stenberg, <daniel@haxx.se>, et al.
 *
 * This software is licensed as described in the file COPYING, which
 * you should have received as part of this distribution. The terms
 * are also available at http://curl.haxx.se/docs/copyright.html.
 *
 * You may opt to use, copy, modify, merge, publish, distribute and/or sell
 * copies of the Software, and permit persons to whom the Software is
 * furnished to do so, under the terms of the COPYING file.
 *
 * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
 * KIND, either express or implied.
 *
 ***************************************************************************/
#include <stdio.h>
#include <string.h>
#include <curl/curl.h>

/* This is a simple example showing how to send mail using libcurl's SMTP
 * capabilities. It builds on the smtp-send.c example, adding some
 * authentication and transport security.
 */

#define FROM    "<sender@example.org>"
#define TO      "<addressee@example.net>"
#define CC      "<info@example.org>"

static const char *payload_text[] = {
  "Date: Mon, 29 Nov 2010 21:54:29 +1100\r\n",
  "To: " TO "\r\n",
  "From: " FROM "(Example User)\r\n",
  "Cc: " CC "(Another example User)\r\n",
  "Message-ID: <dcd7cb36-11db-487a-9f3a-e652a9458efd@rfcpedant.example.org>\r\n",
  "Subject: SMTP TLS example message\r\n",
  "\r\n", /* empty line to divide headers from body, see RFC5322 */
  "The body of the message starts here.\r\n",
  "\r\n",
  "It could be a lot of lines, could be MIME encoded, whatever.\r\n",
  "Check RFC5322.\r\n",
  NULL
};

struct upload_status {
  int lines_read;
};

static size_t payload_source(void *ptr, size_t size, size_t nmemb, void *userp)
{
  struct upload_status *upload_ctx = (struct upload_status *)userp;
  const char *data;

  if((size == 0) || (nmemb == 0) || ((size*nmemb) < 1)) {
    return 0;
  }

  data = payload_text[upload_ctx->lines_read];

  if(data) {
    size_t len = strlen(data);
    memcpy(ptr, data, len);
    upload_ctx->lines_read++;

    return len;
  }

  return 0;
}

int main(void)
{
  CURL *curl;
  CURLcode res = CURLE_OK;
  struct curl_slist *recipients = NULL;
  struct upload_status upload_ctx;

  upload_ctx.lines_read = 0;

  curl = curl_easy_init();
  if(curl) {
    /* This is the URL for your mailserver. Note the use of port 587 here,
     * instead of the normal SMTP port (25). Port 587 is commonly used for
     * secure mail submission (see RFC4403), but you should use whatever
     * matches your server configuration. */
    curl_easy_setopt(curl, CURLOPT_URL, "smtp://mainserver.example.net:587");

    /* In this example, we'll start with a plain text connection, and upgrade
     * to Transport Layer Security (TLS) using the STARTTLS command. Be careful
     * of using CURLUSESSL_TRY here, because if TLS upgrade fails, the transfer
     * will continue anyway - see the security discussion in the libcurl
     * tutorial for more details. */
    curl_easy_setopt(curl, CURLOPT_USE_SSL, (long)CURLUSESSL_ALL);

    /* If your server doesn't have a valid certificate, then you can disable
     * part of the Transport Layer Security protection by setting the
     * CURLOPT_SSL_VERIFYPEER and CURLOPT_SSL_VERIFYHOST options to 0 (false).
     *   curl_easy_setopt(curl, CURLOPT_SSL_VERIFYPEER, 0L);
     *   curl_easy_setopt(curl, CURLOPT_SSL_VERIFYHOST, 0L);
     * That is, in general, a bad idea. It is still better than sending your
     * authentication details in plain text though.
     * Instead, you should get the issuer certificate (or the host certificate
     * if the certificate is self-signed) and add it to the set of certificates
     * that are known to libcurl using CURLOPT_CAINFO and/or CURLOPT_CAPATH. See
     * docs/SSLCERTS for more information. */
    curl_easy_setopt(curl, CURLOPT_CAINFO, "/path/to/certificate.pem");

    /* A common reason for requiring transport security is to protect
     * authentication details (user names and passwords) from being "snooped"
     * on the network. Here is how the user name and password are provided: */
    curl_easy_setopt(curl, CURLOPT_USERNAME, "user@example.net");
    curl_easy_setopt(curl, CURLOPT_PASSWORD, "P@ssw0rd");

    /* Value for envelope reverse-path */
    curl_easy_setopt(curl, CURLOPT_MAIL_FROM, FROM);

    /* Add two recipients, in this particular case they correspond to the
     * To: and Cc: addressees in the header, but they could be any kind of
     * recipient. */
    recipients = curl_slist_append(recipients, TO);
    recipients = curl_slist_append(recipients, CC);
    curl_easy_setopt(curl, CURLOPT_MAIL_RCPT, recipients);

    /* In this case, we're using a callback function to specify the data. You
     * could just use the CURLOPT_READDATA option to specify a FILE pointer to
     * read from. */
    curl_easy_setopt(curl, CURLOPT_READFUNCTION, payload_source);
    curl_easy_setopt(curl, CURLOPT_READDATA, &upload_ctx);
    curl_easy_setopt(curl, CURLOPT_UPLOAD, 1L);

    /* Since the traffic will be encrypted, it is very useful to turn on debug
     * information within libcurl to see what is happening during the transfer.
     */
    curl_easy_setopt(curl, CURLOPT_VERBOSE, 1L);

    /* Send the message */
    res = curl_easy_perform(curl);

    /* Check for errors */
    if(res != CURLE_OK)
      fprintf(stderr, "curl_easy_perform() failed: %s\n",
              curl_easy_strerror(res));

    /* Free the list of recipients */
    curl_slist_free_all(recipients);

    /* Always cleanup */
    curl_easy_cleanup(curl);
  }

  return (int)res;
}