examples: Added POP3 TLS example

docs/examples/Makefile.inc

@@ -6,9 +6,9 @@ check_PROGRAMS = 10-at-a-time anyauthput cookie_interface debug fileupload \
   sendrecv httpcustomheader certinfo chkspeed ftpgetinfo ftp-wildcard \
   smtp-multi smtp-send smtp-ssl smtp-tls smtp-vrfy smtp-expn rtsp \
   externalsocket resolve progressfunc pop3-retr pop3-list pop3-uidl pop3-dele \
-  pop3-top pop3-stat pop3-noop pop3-ssl imap-list imap-fetch imap-store \
+  pop3-top pop3-stat pop3-noop pop3-ssl pop3-tls imap-list imap-fetch \
-  imap-append imap-examine imap-search imap-create imap-delete imap-copy \
+  imap-store imap-append imap-examine imap-search imap-create imap-delete \
-  imap-noop imap-ssl imap-tls url2file sftpget ftpsget postinmemory
+  imap-copy imap-noop imap-ssl imap-tls url2file sftpget ftpsget postinmemory
 
 # These examples require external dependencies that may not be commonly
 # available on POSIX systems, so don't bother attempting to compile them here.

docs/examples/pop3-ssl.c

@@ -64,6 +64,11 @@ int main(void)
     curl_easy_setopt(curl, CURLOPT_SSL_VERIFYHOST, 0L);
 #endif
 
+    /* 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);
+
     /* Perform the retr */
     res = curl_easy_perform(curl);
 

docs/examples/pop3-tls.c

@@ -0,0 +1,84 @@
+/***************************************************************************
+ *                                  _   _ ____  _
+ *  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 <curl/curl.h>
+
+/* This is a simple example showing how to retrieve mail using libcurl's POP3
+ * capabilities. It builds on the pop3-retr.c example adding transport
+ * security to protect the authentication details from being snooped.
+ *
+ * Note that this example requires libcurl 7.20.0 or above.
+ */
+
+int main(void)
+{
+  CURL *curl;
+  CURLcode res = CURLE_OK;
+
+  curl = curl_easy_init();
+  if(curl) {
+    /* Set username and password */
+    curl_easy_setopt(curl, CURLOPT_USERNAME, "user");
+    curl_easy_setopt(curl, CURLOPT_PASSWORD, "secret");
+
+    /* This will retreive message 1 from the user's mailbox */
+    curl_easy_setopt(curl, CURLOPT_URL, "pop3://pop.example.com/1");
+
+    /* In this example, we'll start with a plain text connection, and upgrade
+     * to Transport Layer Security (TLS) using the STLS 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");
+
+    /* 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);
+
+    /* Perform the retr */
+    res = curl_easy_perform(curl);
+
+    /* Check for errors */
+    if(res != CURLE_OK)
+      fprintf(stderr, "curl_easy_perform() failed: %s\n",
+              curl_easy_strerror(res));
+
+    /* Always cleanup */
+    curl_easy_cleanup(curl);
+  }
+
+  return (int)res;
+}