openssl.c

Wget很好的处理了http和ftp的下载,很值得学习的经典代码

/* SSL support via OpenSSL library.
   Copyright (C) 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007,
   2008 Free Software Foundation, Inc.
   Originally contributed by Christian Fraenkel.

This file is part of GNU Wget.

GNU Wget is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3 of the License, or
(at your option) any later version.

GNU Wget is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with Wget.  If not, see <http://www.gnu.org/licenses/>.

Additional permission under GNU GPL version 3 section 7

If you modify this program, or any covered work, by linking or
combining it with the OpenSSL project's OpenSSL library (or a
modified version of that library), containing parts covered by the
terms of the OpenSSL or SSLeay licenses, the Free Software Foundation
grants you additional permission to convey the resulting work.
Corresponding Source for a non-source form of such a combination
shall include the source code for the parts of OpenSSL used as well
as that of the covered work.  */

#include <config.h>

#include <assert.h>
#include <errno.h>
#ifdef HAVE_UNISTD_H
# include <unistd.h>
#endif
#include <string.h>

#include <openssl/ssl.h>
#include <openssl/x509.h>
#include <openssl/err.h>
#include <openssl/rand.h>

#include "wget.h"
#include "utils.h"
#include "connect.h"
#include "url.h"
#include "ssl.h"

/* Application-wide SSL context.  This is common to all SSL
   connections.  */
static SSL_CTX *ssl_ctx;

/* Initialize the SSL's PRNG using various methods. */

static void
init_prng (void)
{
  char namebuf[256];
  const char *random_file;

  if (RAND_status ())
    /* The PRNG has been seeded; no further action is necessary. */
    return;

  /* Seed from a file specified by the user.  This will be the file
     specified with --random-file, $RANDFILE, if set, or ~/.rnd, if it
     exists.  */
  if (opt.random_file)
    random_file = opt.random_file;
  else
    {
      /* Get the random file name using RAND_file_name. */
      namebuf[0] = '\0';
      random_file = RAND_file_name (namebuf, sizeof (namebuf));
    }

  if (random_file && *random_file)
    /* Seed at most 16k (apparently arbitrary value borrowed from
       curl) from random file. */
    RAND_load_file (random_file, 16384);

  if (RAND_status ())
    return;

  /* Get random data from EGD if opt.egd_file was used.  */
  if (opt.egd_file && *opt.egd_file)
    RAND_egd (opt.egd_file);

  if (RAND_status ())
    return;

#ifdef WINDOWS
  /* Under Windows, we can try to seed the PRNG using screen content.
     This may or may not work, depending on whether we'll calling Wget
     interactively.  */

  RAND_screen ();
  if (RAND_status ())
    return;
#endif

#if 0 /* don't do this by default */
  {
    int maxrand = 500;

    /* Still not random enough, presumably because neither /dev/random
       nor EGD were available.  Try to seed OpenSSL's PRNG with libc
       PRNG.  This is cryptographically weak and defeats the purpose
       of using OpenSSL, which is why it is highly discouraged.  */

    logprintf (LOG_NOTQUIET, _("WARNING: using a weak random seed.\n"));

    while (RAND_status () == 0 && maxrand-- > 0)
      {
        unsigned char rnd = random_number (256);
        RAND_seed (&rnd, sizeof (rnd));
      }
  }
#endif
}

/* Print errors in the OpenSSL error stack. */

static void
print_errors (void) 
{
  unsigned long err;
  while ((err = ERR_get_error ()) != 0)
    logprintf (LOG_NOTQUIET, "OpenSSL: %s\n", ERR_error_string (err, NULL));
}

/* Convert keyfile type as used by options.h to a type as accepted by
   SSL_CTX_use_certificate_file and SSL_CTX_use_PrivateKey_file.

   (options.h intentionally doesn't use values from openssl/ssl.h so
   it doesn't depend specifically on OpenSSL for SSL functionality.)  */

static int
key_type_to_ssl_type (enum keyfile_type type)
{
  switch (type)
    {
    case keyfile_pem:
      return SSL_FILETYPE_PEM;
    case keyfile_asn1:
      return SSL_FILETYPE_ASN1;
    default:
      abort ();
    }
}

/* Create an SSL Context and set default paths etc.  Called the first
   time an HTTP download is attempted.

   Returns true on success, false otherwise.  */

bool
ssl_init ()
{
  SSL_METHOD *meth;

  if (ssl_ctx)
    /* The SSL has already been initialized. */
    return true;

  /* Init the PRNG.  If that fails, bail out.  */
  init_prng ();
  if (RAND_status () != 1)
    {
      logprintf (LOG_NOTQUIET,
                 _("Could not seed PRNG; consider using --random-file.\n"));
      goto error;
    }

  SSL_library_init ();
  SSL_load_error_strings ();
  SSLeay_add_all_algorithms ();
  SSLeay_add_ssl_algorithms ();

  switch (opt.secure_protocol)
    {
    case secure_protocol_auto:
      meth = SSLv23_client_method ();
      break;
    case secure_protocol_sslv2:
      meth = SSLv2_client_method ();
      break;
    case secure_protocol_sslv3:
      meth = SSLv3_client_method ();
      break;
    case secure_protocol_tlsv1:
      meth = TLSv1_client_method ();
      break;
    default:
      abort ();
    }

  ssl_ctx = SSL_CTX_new (meth);
  if (!ssl_ctx)
    goto error;

  SSL_CTX_set_default_verify_paths (ssl_ctx);
  SSL_CTX_load_verify_locations (ssl_ctx, opt.ca_cert, opt.ca_directory);

  /* SSL_VERIFY_NONE instructs OpenSSL not to abort SSL_connect if the
     certificate is invalid.  We verify the certificate separately in
     ssl_check_certificate, which provides much better diagnostics
     than examining the error stack after a failed SSL_connect.  */
  SSL_CTX_set_verify (ssl_ctx, SSL_VERIFY_NONE, NULL);

  if (opt.cert_file)
    if (SSL_CTX_use_certificate_file (ssl_ctx, opt.cert_file,
                                      key_type_to_ssl_type (opt.cert_type))
        != 1)
      goto error;
  if (opt.private_key)
    if (SSL_CTX_use_PrivateKey_file (ssl_ctx, opt.private_key,
                                     key_type_to_ssl_type (opt.private_key_type))
        != 1)
      goto error;

  /* Since fd_write unconditionally assumes partial writes (and
     handles them correctly), allow them in OpenSSL.  */
  SSL_CTX_set_mode (ssl_ctx, SSL_MODE_ENABLE_PARTIAL_WRITE);

  /* The OpenSSL library can handle renegotiations automatically, so
     tell it to do so.  */
  SSL_CTX_set_mode (ssl_ctx, SSL_MODE_AUTO_RETRY);

  return true;

 error:
  if (ssl_ctx)
    SSL_CTX_free (ssl_ctx);
  print_errors ();
  return false;
}

struct openssl_transport_context {
  SSL *conn;                    /* SSL connection handle */
  char *last_error;             /* last error printed with openssl_errstr */
};

static int
openssl_read (int fd, char *buf, int bufsize, void *arg)
{
  int ret;
  struct openssl_transport_context *ctx = arg;
  SSL *conn = ctx->conn;
  do
    ret = SSL_read (conn, buf, bufsize);
  while (ret == -1
         && SSL_get_error (conn, ret) == SSL_ERROR_SYSCALL
         && errno == EINTR);
  return ret;
}

static int
openssl_write (int fd, char *buf, int bufsize, void *arg)
{
  int ret = 0;
  struct openssl_transport_context *ctx = arg;
  SSL *conn = ctx->conn;
  do
    ret = SSL_write (conn, buf, bufsize);
  while (ret == -1
         && SSL_get_error (conn, ret) == SSL_ERROR_SYSCALL
         && errno == EINTR);
  return ret;
}

static int
openssl_poll (int fd, double timeout, int wait_for, void *arg)
{
  struct openssl_transport_context *ctx = arg;
  SSL *conn = ctx->conn;
  if (timeout == 0)
    return 1;
  if (SSL_pending (conn))
    return 1;
  return select_fd (fd, timeout, wait_for);
}

static int
openssl_peek (int fd, char *buf, int bufsize, void *arg)
{
  int ret;
  struct openssl_transport_context *ctx = arg;
  SSL *conn = ctx->conn;
  do
    ret = SSL_peek (conn, buf, bufsize);
  while (ret == -1