/***************************************************************************
 *                                  _   _ ____  _
 *  Project                     ___| | | |  _ \| |
 *                             / __| | | | |_) | |
 *                            | (__| |_| |  _ <| |___
 *                             \___|\___/|_| \_\_____|
 *
 * Copyright (C) 1998 - 2017, 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 https://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.
 *
 ***************************************************************************/
/* <DESC>
 * CA cert in memory with OpenSSL to get a HTTPS page.
 * </DESC>
 */

#include <openssl/err.h>
#include <openssl/ssl.h>
#include <curl/curl.h>
#include <stdio.h>

size_t writefunction(void *ptr, size_t size, size_t nmemb, void *stream)
{
  fwrite(ptr, size, nmemb, (FILE *)stream);
  return (nmemb*size);
}

static CURLcode sslctx_function(CURL *curl, void *sslctx, void *parm)
{
  CURLcode rv = CURLE_ABORTED_BY_CALLBACK;
  X509_STORE *store = NULL;
  X509 *cert = NULL;
  BIO *bio = NULL;
  char *mypem =
    /* CA for example.com. CN = DigiCert High Assurance EV Root CA */
    "-----BEGIN CERTIFICATE-----\n"
    "MIIDxTCCAq2gAwIBAgIQAqxcJmoLQJuPC3nyrkYldzANBgkqhkiG9w0BAQUFADBs\n"
    "MQswCQYDVQQGEwJVUzEVMBMGA1UEChMMRGlnaUNlcnQgSW5jMRkwFwYDVQQLExB3\n"
    "d3cuZGlnaWNlcnQuY29tMSswKQYDVQQDEyJEaWdpQ2VydCBIaWdoIEFzc3VyYW5j\n"
    "ZSBFViBSb290IENBMB4XDTA2MTExMDAwMDAwMFoXDTMxMTExMDAwMDAwMFowbDEL\n"
    "MAkGA1UEBhMCVVMxFTATBgNVBAoTDERpZ2lDZXJ0IEluYzEZMBcGA1UECxMQd3d3\n"
    "LmRpZ2ljZXJ0LmNvbTErMCkGA1UEAxMiRGlnaUNlcnQgSGlnaCBBc3N1cmFuY2Ug\n"
    "RVYgUm9vdCBDQTCCASIwDQYJKoZIhvcNAQEBBQADggEPADCCAQoCggEBAMbM5XPm\n"
    "+9S75S0tMqbf5YE/yc0lSbZxKsPVlDRnogocsF9ppkCxxLeyj9CYpKlBWTrT3JTW\n"
    "PNt0OKRKzE0lgvdKpVMSOO7zSW1xkX5jtqumX8OkhPhPYlG++MXs2ziS4wblCJEM\n"
    "xChBVfvLWokVfnHoNb9Ncgk9vjo4UFt3MRuNs8ckRZqnrG0AFFoEt7oT61EKmEFB\n"
    "Ik5lYYeBQVCmeVyJ3hlKV9Uu5l0cUyx+mM0aBhakaHPQNAQTXKFx01p8VdteZOE3\n"
    "hzBWBOURtCmAEvF5OYiiAhF8J2a3iLd48soKqDirCmTCv2ZdlYTBoSUeh10aUAsg\n"
    "EsxBu24LUTi4S8sCAwEAAaNjMGEwDgYDVR0PAQH/BAQDAgGGMA8GA1UdEwEB/wQF\n"
    "MAMBAf8wHQYDVR0OBBYEFLE+w2kD+L9HAdSYJhoIAu9jZCvDMB8GA1UdIwQYMBaA\n"
    "FLE+w2kD+L9HAdSYJhoIAu9jZCvDMA0GCSqGSIb3DQEBBQUAA4IBAQAcGgaX3Nec\n"
    "nzyIZgYIVyHbIUf4KmeqvxgydkAQV8GK83rZEWWONfqe/EW1ntlMMUu4kehDLI6z\n"
    "eM7b41N5cdblIZQB2lWHmiRk9opmzN6cN82oNLFpmyPInngiK3BD41VHMWEZ71jF\n"
    "hS9OMPagMRYjyOfiZRYzy78aG6A9+MpeizGLYAiJLQwGXFK3xPkKmNEVX58Svnw2\n"
    "Yzi9RKR/5CYrCsSXaQ3pjOLAEFe4yHYSkVXySGnYvCoCWw9E1CAx2/S6cCZdkGCe\n"
    "vEsXCS+0yx5DaMkHJ8HSXPfqIbloEpw8nL+e/IBcm2PN7EeqJSdnoDfzAIJ9VNep\n"
    "+OkuE6N36B9K\n"
    "-----END CERTIFICATE-----\n";

  /* clear the current thread's OpenSSL error queue */
  ERR_clear_error();

  /* get a BIO */
  bio = BIO_new_mem_buf(mypem, -1);
  if(!bio)
    goto err;

  /* use it to read the PEM formatted certificate from memory into an X509
   * structure that SSL can use
   */
  if(!PEM_read_bio_X509(bio, &cert, 0, NULL))
    goto err;

  /* get a pointer to the X509 certificate store (which may be empty!) */
  store = SSL_CTX_get_cert_store((SSL_CTX *)sslctx);
  if(!store)
    goto err;

  /* add our certificate to this store */
  if(!X509_STORE_add_cert(store, cert)) {
    unsigned long error = ERR_peek_last_error();

    /* Ignore error X509_R_CERT_ALREADY_IN_HASH_TABLE which means the
     * certificate is already in the store. That could happen if
     * libcurl already loaded the certificate from a ca cert bundle
     * set at libcurl build-time or runtime.
     */
    if(ERR_GET_LIB(error) != ERR_LIB_X509 ||
       ERR_GET_REASON(error) != X509_R_CERT_ALREADY_IN_HASH_TABLE)
      goto err;

    ERR_clear_error();
  }

  rv = CURLE_OK;

err:
  if(rv != CURLE_OK) {
    char errbuf[256];
    unsigned long error = ERR_peek_last_error();

    fprintf(stderr, "error adding certificate\n");
    if(error) {
      ERR_error_string_n(error, errbuf, sizeof errbuf);
      fprintf(stderr, "%s\n", errbuf);
    }
  }

  X509_free(cert);
  BIO_free(bio);
  ERR_clear_error();

  return rv;
}

int main(void)
{
  CURL *ch;
  CURLcode rv;

  rv = curl_global_init(CURL_GLOBAL_ALL);
  ch = curl_easy_init();
  rv = curl_easy_setopt(ch, CURLOPT_VERBOSE, 0L);
  rv = curl_easy_setopt(ch, CURLOPT_HEADER, 0L);
  rv = curl_easy_setopt(ch, CURLOPT_NOPROGRESS, 1L);
  rv = curl_easy_setopt(ch, CURLOPT_NOSIGNAL, 1L);
  rv = curl_easy_setopt(ch, CURLOPT_WRITEFUNCTION, *writefunction);
  rv = curl_easy_setopt(ch, CURLOPT_WRITEDATA, stdout);
  rv = curl_easy_setopt(ch, CURLOPT_HEADERFUNCTION, *writefunction);
  rv = curl_easy_setopt(ch, CURLOPT_HEADERDATA, stderr);
  rv = curl_easy_setopt(ch, CURLOPT_SSLCERTTYPE, "PEM");
  rv = curl_easy_setopt(ch, CURLOPT_SSL_VERIFYPEER, 1L);
  rv = curl_easy_setopt(ch, CURLOPT_URL, "https://www.example.com/");

  /* turn off the default CA locations (optional)
   * otherwise libcurl will load CA certificates from the locations that
   * were detected/specified at build-time
   */
  rv = curl_easy_setopt(ch, CURLOPT_CAINFO, NULL);
  rv = curl_easy_setopt(ch, CURLOPT_CAPATH, NULL);

  /* first try: retrieve page without ca certificates -> should fail
   * unless libcurl was built --with-ca-fallback enabled at build-time
   */
  rv = curl_easy_perform(ch);
  if(rv == CURLE_OK)
    printf("*** transfer succeeded ***\n");
  else
    printf("*** transfer failed ***\n");

  /* use a fresh connection (optional)
   * this option seriously impacts performance of multiple transfers but
   * it is necessary order to demonstrate this example. recall that the
   * ssl ctx callback is only called _before_ an SSL connection is
   * established, therefore it will not affect existing verified SSL
   * connections already in the connection cache associated with this
   * handle. normally you would set the ssl ctx function before making
   * any transfers, and not use this option.
   */
  rv = curl_easy_setopt(ch, CURLOPT_FRESH_CONNECT, 1L);

  /* second try: retrieve page using cacerts' certificate -> will succeed
   * load the certificate by installing a function doing the necessary
   * "modifications" to the SSL CONTEXT just before link init
   */
  rv = curl_easy_setopt(ch, CURLOPT_SSL_CTX_FUNCTION, *sslctx_function);
  rv = curl_easy_perform(ch);
  if(rv == CURLE_OK)
    printf("*** transfer succeeded ***\n");
  else
    printf("*** transfer failed ***\n");

  curl_easy_cleanup(ch);
  curl_global_cleanup();
  return rv;
}