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Filename : threaded-ssl.c
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/***************************************************************************
 *                                  _   _ ____  _
 *  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>
 * Show the required mutex callback setups for GnuTLS and OpenSSL when using
 * libcurl multi-threaded.
 * </DESC>
 */
/* A multi-threaded example that uses pthreads and fetches 4 remote files at
 * once over HTTPS. The lock callbacks and stuff assume OpenSSL <1.1 or GnuTLS
 * (libgcrypt) so far.
 *
 * OpenSSL docs for this:
 *   https://www.openssl.org/docs/crypto/threads.html
 * gcrypt docs for this:
 *   https://gnupg.org/documentation/manuals/gcrypt/Multi_002dThreading.html
 */

#define USE_OPENSSL /* or USE_GNUTLS accordingly */

#include <stdio.h>
#include <pthread.h>
#include <curl/curl.h>

#define NUMT 4

/* we have this global to let the callback get easy access to it */
static pthread_mutex_t *lockarray;

#ifdef USE_OPENSSL
#include <openssl/crypto.h>
static void lock_callback(int mode, int type, char *file, int line)
{
  (void)file;
  (void)line;
  if(mode & CRYPTO_LOCK) {
    pthread_mutex_lock(&(lockarray[type]));
  }
  else {
    pthread_mutex_unlock(&(lockarray[type]));
  }
}

static unsigned long thread_id(void)
{
  unsigned long ret;

  ret = (unsigned long)pthread_self();
  return ret;
}

static void init_locks(void)
{
  int i;

  lockarray = (pthread_mutex_t *)OPENSSL_malloc(CRYPTO_num_locks() *
                                                sizeof(pthread_mutex_t));
  for(i = 0; i<CRYPTO_num_locks(); i++) {
    pthread_mutex_init(&(lockarray[i]), NULL);
  }

  CRYPTO_set_id_callback((unsigned long (*)())thread_id);
  CRYPTO_set_locking_callback((void (*)())lock_callback);
}

static void kill_locks(void)
{
  int i;

  CRYPTO_set_locking_callback(NULL);
  for(i = 0; i<CRYPTO_num_locks(); i++)
    pthread_mutex_destroy(&(lockarray[i]));

  OPENSSL_free(lockarray);
}
#endif

#ifdef USE_GNUTLS
#include <gcrypt.h>
#include <errno.h>

GCRY_THREAD_OPTION_PTHREAD_IMPL;

void init_locks(void)
{
  gcry_control(GCRYCTL_SET_THREAD_CBS);
}

#define kill_locks()
#endif

/* List of URLs to fetch.*/
const char * const urls[]= {
  "https://www.example.com/",
  "https://www2.example.com/",
  "https://www3.example.com/",
  "https://www4.example.com/",
};

static void *pull_one_url(void *url)
{
  CURL *curl;

  curl = curl_easy_init();
  curl_easy_setopt(curl, CURLOPT_URL, url);
  /* this example doesn't verify the server's certificate, which means we
     might be downloading stuff from an impostor */
  curl_easy_setopt(curl, CURLOPT_SSL_VERIFYPEER, 0L);
  curl_easy_setopt(curl, CURLOPT_SSL_VERIFYHOST, 0L);
  curl_easy_perform(curl); /* ignores error */
  curl_easy_cleanup(curl);

  return NULL;
}

int main(int argc, char **argv)
{
  pthread_t tid[NUMT];
  int i;
  int error;
  (void)argc; /* we don't use any arguments in this example */
  (void)argv;

  /* Must initialize libcurl before any threads are started */
  curl_global_init(CURL_GLOBAL_ALL);

  init_locks();

  for(i = 0; i< NUMT; i++) {
    error = pthread_create(&tid[i],
                           NULL, /* default attributes please */
                           pull_one_url,
                           (void *)urls[i]);
    if(0 != error)
      fprintf(stderr, "Couldn't run thread number %d, errno %d\n", i, error);
    else
      fprintf(stderr, "Thread %d, gets %s\n", i, urls[i]);
  }

  /* now wait for all threads to terminate */
  for(i = 0; i< NUMT; i++) {
    error = pthread_join(tid[i], NULL);
    fprintf(stderr, "Thread %d terminated\n", i);
  }

  kill_locks();

  return 0;
}