xref: /curl/docs/examples/pop3-tls.c (revision f540e43b)
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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.
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15  * copies of the Software, and permit persons to whom the Software is
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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
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23  ***************************************************************************/
24 
25 /* <DESC>
26  * POP3 using TLS
27  * </DESC>
28  */
29 
30 #include <stdio.h>
31 #include <curl/curl.h>
32 
33 /* This is a simple example showing how to retrieve mail using libcurl's POP3
34  * capabilities. It builds on the pop3-retr.c example adding transport
35  * security to protect the authentication details from being snooped.
36  *
37  * Note that this example requires libcurl 7.20.0 or above.
38  */
39 
main(void)40 int main(void)
41 {
42   CURL *curl;
43   CURLcode res = CURLE_OK;
44 
45   curl = curl_easy_init();
46   if(curl) {
47     /* Set username and password */
48     curl_easy_setopt(curl, CURLOPT_USERNAME, "user");
49     curl_easy_setopt(curl, CURLOPT_PASSWORD, "secret");
50 
51     /* This retrieves message 1 from the user's mailbox */
52     curl_easy_setopt(curl, CURLOPT_URL, "pop3://pop.example.com/1");
53 
54     /* In this example, we start with a plain text connection, and upgrade to
55      * Transport Layer Security (TLS) using the STLS command. Be careful of
56      * using CURLUSESSL_TRY here, because if TLS upgrade fails, the transfer
57      * continues anyway - see the security discussion in the libcurl tutorial
58      * for more details. */
59     curl_easy_setopt(curl, CURLOPT_USE_SSL, (long)CURLUSESSL_ALL);
60 
61     /* If your server does not have a valid certificate, then you can disable
62      * part of the Transport Layer Security protection by setting the
63      * CURLOPT_SSL_VERIFYPEER and CURLOPT_SSL_VERIFYHOST options to 0 (false).
64      *   curl_easy_setopt(curl, CURLOPT_SSL_VERIFYPEER, 0L);
65      *   curl_easy_setopt(curl, CURLOPT_SSL_VERIFYHOST, 0L);
66      *
67      * That is, in general, a bad idea. It is still better than sending your
68      * authentication details in plain text though.  Instead, you should get
69      * the issuer certificate (or the host certificate if the certificate is
70      * self-signed) and add it to the set of certificates that are known to
71      * libcurl using CURLOPT_CAINFO and/or CURLOPT_CAPATH. See docs/SSLCERTS
72      * for more information. */
73     curl_easy_setopt(curl, CURLOPT_CAINFO, "/path/to/certificate.pem");
74 
75     /* Since the traffic is encrypted, it is useful to turn on debug
76      * information within libcurl to see what is happening during the
77      * transfer */
78     curl_easy_setopt(curl, CURLOPT_VERBOSE, 1L);
79 
80     /* Perform the retr */
81     res = curl_easy_perform(curl);
82 
83     /* Check for errors */
84     if(res != CURLE_OK)
85       fprintf(stderr, "curl_easy_perform() failed: %s\n",
86               curl_easy_strerror(res));
87 
88     /* Always cleanup */
89     curl_easy_cleanup(curl);
90   }
91 
92   return (int)res;
93 }
94