openssl.c

/***************************************************************************
 *                                  _   _ ____  _
 *  Project                     ___| | | |  _ \| |
 *                             / __| | | | |_) | |
 *                            | (__| |_| |  _ <| |___
 *                             \___|\___/|_| \_\_____|
 *
 * Copyright (C) 1998 - 2016, 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.
 *
 ***************************************************************************/

/*
 * Source file for all OpenSSL-specific code for the TLS/SSL layer. No code
 * but vtls.c should ever call or use these functions.
 */

/*
 * The original SSLeay-using code for curl was written by Linas Vepstas and
 * Sampo Kellomaki 1998.
 */

#include "curl_setup.h"

#ifdef USE_OPENSSL

#ifdef HAVE_LIMITS_H
#include <limits.h>
#endif

#include "urldata.h"
#include "sendf.h"
#include "formdata.h" /* for the boundary function */
#include "url.h" /* for the ssl config check function */
#include "inet_pton.h"
#include "openssl.h"
#include "connect.h"
#include "slist.h"
#include "strequal.h"
#include "select.h"
#include "vtls.h"
#include "rawstr.h"
#include "hostcheck.h"
#include "curl_printf.h"

#include <openssl/ssl.h>
#include <openssl/rand.h>
#include <openssl/x509v3.h>
#include <openssl/dsa.h>
#include <openssl/dh.h>
#include <openssl/err.h>
#include <openssl/md5.h>
#include <openssl/conf.h>
#include <openssl/bn.h>
#include <openssl/rsa.h>

#ifdef HAVE_OPENSSL_PKCS12_H
#include <openssl/pkcs12.h>
#endif

#if (OPENSSL_VERSION_NUMBER >= 0x0090808fL) && !defined(OPENSSL_NO_OCSP)
#include <openssl/ocsp.h>
#endif

#include "warnless.h"
#include "non-ascii.h" /* for Curl_convert_from_utf8 prototype */

/* The last #include files should be: */
#include "curl_memory.h"
#include "memdebug.h"

#ifndef OPENSSL_VERSION_NUMBER
#error "OPENSSL_VERSION_NUMBER not defined"
#endif

#if defined(HAVE_OPENSSL_ENGINE_H)
#include <openssl/ui.h>
#endif

#if OPENSSL_VERSION_NUMBER >= 0x00909000L
#define SSL_METHOD_QUAL const
#else
#define SSL_METHOD_QUAL
#endif

#if (OPENSSL_VERSION_NUMBER >= 0x10000000L)
#define HAVE_ERR_REMOVE_THREAD_STATE 1
#endif

#if !defined(HAVE_SSLV2_CLIENT_METHOD) || \
  OPENSSL_VERSION_NUMBER >= 0x10100000L /* 1.1.0+ has no SSLv2 */
#undef OPENSSL_NO_SSL2 /* undef first to avoid compiler warnings */
#define OPENSSL_NO_SSL2
#endif

#if (OPENSSL_VERSION_NUMBER >= 0x10100000L) && /* OpenSSL 1.1.0+ */ \
  !defined(LIBRESSL_VERSION_NUMBER)
#define SSLeay_add_ssl_algorithms() SSL_library_init()
#define SSLEAY_VERSION_NUMBER OPENSSL_VERSION_NUMBER
#define HAVE_X509_GET0_EXTENSIONS 1 /* added in 1.1.0 -pre1 */
#define HAVE_OPAQUE_EVP_PKEY 1 /* since 1.1.0 -pre3 */
#endif

#if (OPENSSL_VERSION_NUMBER >= 0x1000200fL) && /* 1.0.2 or later */ \
  !defined(LIBRESSL_VERSION_NUMBER)
#define HAVE_X509_GET0_SIGNATURE 1
#endif

#if (OPENSSL_VERSION_NUMBER < 0x0090808fL)
/* not present in older OpenSSL */
#define OPENSSL_load_builtin_modules(x)
#endif

/*
 * Number of bytes to read from the random number seed file. This must be
 * a finite value (because some entropy "files" like /dev/urandom have
 * an infinite length), but must be large enough to provide enough
 * entopy to properly seed OpenSSL's PRNG.
 */
#define RAND_LOAD_LENGTH 1024

static int passwd_callback(char *buf, int num, int encrypting,
                           void *global_passwd)
{
  DEBUGASSERT(0 == encrypting);

  if(!encrypting) {
    int klen = curlx_uztosi(strlen((char *)global_passwd));
    if(num > klen) {
      memcpy(buf, global_passwd, klen+1);
      return klen;
    }
  }
  return 0;
}

/*
 * rand_enough() is a function that returns TRUE if we have seeded the random
 * engine properly. We use some preprocessor magic to provide a seed_enough()
 * macro to use, just to prevent a compiler warning on this function if we
 * pass in an argument that is never used.
 */

#ifdef HAVE_RAND_STATUS
#define seed_enough(x) rand_enough()
static bool rand_enough(void)
{
  return (0 != RAND_status()) ? TRUE : FALSE;
}
#else
#define seed_enough(x) rand_enough(x)
static bool rand_enough(int nread)
{
  /* this is a very silly decision to make */
  return (nread > 500) ? TRUE : FALSE;
}
#endif

static int ossl_seed(struct SessionHandle *data)
{
  char *buf = data->state.buffer; /* point to the big buffer */
  int nread=0;

  /* Q: should we add support for a random file name as a libcurl option?
     A: Yes, it is here */

#ifndef RANDOM_FILE
  /* if RANDOM_FILE isn't defined, we only perform this if an option tells
     us to! */
  if(data->set.ssl.random_file)
#define RANDOM_FILE "" /* doesn't matter won't be used */
#endif
  {
    /* let the option override the define */
    nread += RAND_load_file((data->set.str[STRING_SSL_RANDOM_FILE]?
                             data->set.str[STRING_SSL_RANDOM_FILE]:
                             RANDOM_FILE),
                            RAND_LOAD_LENGTH);
    if(seed_enough(nread))
      return nread;
  }

#if defined(HAVE_RAND_EGD)
  /* only available in OpenSSL 0.9.5 and later */
  /* EGD_SOCKET is set at configure time or not at all */
#ifndef EGD_SOCKET
  /* If we don't have the define set, we only do this if the egd-option
     is set */
  if(data->set.str[STRING_SSL_EGDSOCKET])
#define EGD_SOCKET "" /* doesn't matter won't be used */
#endif
  {
    /* If there's an option and a define, the option overrides the
       define */
    int ret = RAND_egd(data->set.str[STRING_SSL_EGDSOCKET]?
                       data->set.str[STRING_SSL_EGDSOCKET]:EGD_SOCKET);
    if(-1 != ret) {
      nread += ret;
      if(seed_enough(nread))
        return nread;
    }
  }
#endif

  /* If we get here, it means we need to seed the PRNG using a "silly"
     approach! */
  do {
    unsigned char randb[64];
    int len = sizeof(randb);
    RAND_bytes(randb, len);
    RAND_add(randb, len, (len >> 1));
  } while(!RAND_status());

  /* generates a default path for the random seed file */
  buf[0]=0; /* blank it first */
  RAND_file_name(buf, BUFSIZE);
  if(buf[0]) {
    /* we got a file name to try */
    nread += RAND_load_file(buf, RAND_LOAD_LENGTH);
    if(seed_enough(nread))
      return nread;
  }

  infof(data, "libcurl is now using a weak random seed!\n");
  return nread;
}

static void Curl_ossl_seed(struct SessionHandle *data)
{
  /* we have the "SSL is seeded" boolean static to prevent multiple
     time-consuming seedings in vain */
  static bool ssl_seeded = FALSE;

  if(!ssl_seeded || data->set.str[STRING_SSL_RANDOM_FILE] ||
     data->set.str[STRING_SSL_EGDSOCKET]) {
    ossl_seed(data);
    ssl_seeded = TRUE;
  }
}

#ifndef SSL_FILETYPE_ENGINE
#define SSL_FILETYPE_ENGINE 42
#endif
#ifndef SSL_FILETYPE_PKCS12
#define SSL_FILETYPE_PKCS12 43
#endif
static int do_file_type(const char *type)
{
  if(!type || !type[0])
    return SSL_FILETYPE_PEM;
  if(Curl_raw_equal(type, "PEM"))
    return SSL_FILETYPE_PEM;
  if(Curl_raw_equal(type, "DER"))
    return SSL_FILETYPE_ASN1;
  if(Curl_raw_equal(type, "ENG"))
    return SSL_FILETYPE_ENGINE;
  if(Curl_raw_equal(type, "P12"))
    return SSL_FILETYPE_PKCS12;
  return -1;
}

#if defined(HAVE_OPENSSL_ENGINE_H)
/*
 * Supply default password to the engine user interface conversation.
 * The password is passed by OpenSSL engine from ENGINE_load_private_key()
 * last argument to the ui and can be obtained by UI_get0_user_data(ui) here.
 */
static int ssl_ui_reader(UI *ui, UI_STRING *uis)
{
  const char *password;
  switch(UI_get_string_type(uis)) {
  case UIT_PROMPT:
  case UIT_VERIFY:
    password = (const char*)UI_get0_user_data(ui);
    if(password && (UI_get_input_flags(uis) & UI_INPUT_FLAG_DEFAULT_PWD)) {
      UI_set_result(ui, uis, password);
      return 1;
    }
  default:
    break;
  }
  return (UI_method_get_reader(UI_OpenSSL()))(ui, uis);
}

/*
 * Suppress interactive request for a default password if available.
 */
static int ssl_ui_writer(UI *ui, UI_STRING *uis)
{
  switch(UI_get_string_type(uis)) {
  case UIT_PROMPT:
  case UIT_VERIFY:
    if(UI_get0_user_data(ui) &&
       (UI_get_input_flags(uis) & UI_INPUT_FLAG_DEFAULT_PWD)) {
      return 1;
    }
  default:
    break;
  }
  return (UI_method_get_writer(UI_OpenSSL()))(ui, uis);
}
#endif

static
int cert_stuff(struct connectdata *conn,
               SSL_CTX* ctx,
               char *cert_file,
               const char *cert_type,
               char *key_file,
               const char *key_type)
{
  struct SessionHandle *data = conn->data;

  int file_type = do_file_type(cert_type);

  if(cert_file || (file_type == SSL_FILETYPE_ENGINE)) {
    SSL *ssl;
    X509 *x509;
    int cert_done = 0;

    if(data->set.str[STRING_KEY_PASSWD]) {
      /* set the password in the callback userdata */
      SSL_CTX_set_default_passwd_cb_userdata(ctx,
                                             data->set.str[STRING_KEY_PASSWD]);
      /* Set passwd callback: */
      SSL_CTX_set_default_passwd_cb(ctx, passwd_callback);
    }


    switch(file_type) {
    case SSL_FILETYPE_PEM:
      /* SSL_CTX_use_certificate_chain_file() only works on PEM files */
      if(SSL_CTX_use_certificate_chain_file(ctx,
                                            cert_file) != 1) {
        failf(data,
              "could not load PEM client certificate, OpenSSL error %s, "
              "(no key found, wrong pass phrase, or wrong file format?)",
              ERR_error_string(ERR_get_error(), NULL) );
        return 0;
      }
      break;

    case SSL_FILETYPE_ASN1:
      /* SSL_CTX_use_certificate_file() works with either PEM or ASN1, but
         we use the case above for PEM so this can only be performed with
         ASN1 files. */
      if(SSL_CTX_use_certificate_file(ctx,
                                      cert_file,
                                      file_type) != 1) {
        failf(data,
              "could not load ASN1 client certificate, OpenSSL error %s, "
              "(no key found, wrong pass phrase, or wrong file format?)",
              ERR_error_string(ERR_get_error(), NULL) );
        return 0;
      }
      break;
    case SSL_FILETYPE_ENGINE:
#if defined(HAVE_OPENSSL_ENGINE_H) && defined(ENGINE_CTRL_GET_CMD_FROM_NAME)
      {
        if(data->state.engine) {
          const char *cmd_name = "LOAD_CERT_CTRL";
          struct {
            const char *cert_id;
            X509 *cert;
          } params;

          params.cert_id = cert_file;
          params.cert = NULL;

          /* Does the engine supports LOAD_CERT_CTRL ? */
          if(!ENGINE_ctrl(data->state.engine, ENGINE_CTRL_GET_CMD_FROM_NAME,
                          0, (void *)cmd_name, NULL)) {
            failf(data, "ssl engine does not support loading certificates");
            return 0;
          }

          /* Load the certificate from the engine */
          if(!ENGINE_ctrl_cmd(data->state.engine, cmd_name,
                              0, &params, NULL, 1)) {
            failf(data, "ssl engine cannot load client cert with id"
                  " '%s' [%s]", cert_file,
                  ERR_error_string(ERR_get_error(), NULL));
            return 0;
          }

          if(!params.cert) {
            failf(data, "ssl engine didn't initialized the certificate "
                  "properly.");
            return 0;
          }

          if(SSL_CTX_use_certificate(ctx, params.cert) != 1) {
            failf(data, "unable to set client certificate");
            X509_free(params.cert);
            return 0;
          }
          X509_free(params.cert); /* we don't need the handle any more... */
        }
        else {
          failf(data, "crypto engine not set, can't load certificate");
          return 0;
        }
      }
      break;
#else
      failf(data, "file type ENG for certificate not implemented");
      return 0;
#endif

    case SSL_FILETYPE_PKCS12:
    {
#ifdef HAVE_OPENSSL_PKCS12_H
      FILE *f;
      PKCS12 *p12;
      EVP_PKEY *pri;
      STACK_OF(X509) *ca = NULL;

      f = fopen(cert_file, "rb");
      if(!f) {
        failf(data, "could not open PKCS12 file '%s'", cert_file);
        return 0;
      }
      p12 = d2i_PKCS12_fp(f, NULL);
      fclose(f);

      if(!p12) {
        failf(data, "error reading PKCS12 file '%s'", cert_file);
        return 0;
      }

      PKCS12_PBE_add();

      if(!PKCS12_parse(p12, data->set.str[STRING_KEY_PASSWD], &pri, &x509,
                       &ca)) {
        failf(data,
              "could not parse PKCS12 file, check password, OpenSSL error %s",
              ERR_error_string(ERR_get_error(), NULL) );
        PKCS12_free(p12);
        return 0;
      }

      PKCS12_free(p12);

      if(SSL_CTX_use_certificate(ctx, x509) != 1) {
        failf(data,
              "could not load PKCS12 client certificate, OpenSSL error %s",
              ERR_error_string(ERR_get_error(), NULL) );
        goto fail;
      }

      if(SSL_CTX_use_PrivateKey(ctx, pri) != 1) {
        failf(data, "unable to use private key from PKCS12 file '%s'",
              cert_file);
        goto fail;
      }

      if(!SSL_CTX_check_private_key (ctx)) {
        failf(data, "private key from PKCS12 file '%s' "
              "does not match certificate in same file", cert_file);
        goto fail;
      }
      /* Set Certificate Verification chain */
      if(ca) {
        while(sk_X509_num(ca)) {
          /*
           * Note that sk_X509_pop() is used below to make sure the cert is
           * removed from the stack properly before getting passed to
           * SSL_CTX_add_extra_chain_cert(). Previously we used
           * sk_X509_value() instead, but then we'd clean it in the subsequent
           * sk_X509_pop_free() call.
           */
          X509 *x = sk_X509_pop(ca);
          if(!SSL_CTX_add_extra_chain_cert(ctx, x)) {
            X509_free(x);
            failf(data, "cannot add certificate to certificate chain");
            goto fail;
          }
          /* SSL_CTX_add_client_CA() seems to work with either sk_* function,
           * presumably because it duplicates what we pass to it.
           */
          if(!SSL_CTX_add_client_CA(ctx, x)) {
            failf(data, "cannot add certificate to client CA list");
            goto fail;
          }
        }
      }

      cert_done = 1;
  fail:
      EVP_PKEY_free(pri);
      X509_free(x509);
      sk_X509_pop_free(ca, X509_free);

      if(!cert_done)
        return 0; /* failure! */
      break;
#else
      failf(data, "file type P12 for certificate not supported");
      return 0;
#endif
    }
    default:
      failf(data, "not supported file type '%s' for certificate", cert_type);
      return 0;
    }

    file_type = do_file_type(key_type);

    switch(file_type) {
    case SSL_FILETYPE_PEM:
      if(cert_done)
        break;
      if(!key_file)
        /* cert & key can only be in PEM case in the same file */
        key_file=cert_file;
    case SSL_FILETYPE_ASN1:
      if(SSL_CTX_use_PrivateKey_file(ctx, key_file, file_type) != 1) {
        failf(data, "unable to set private key file: '%s' type %s",
              key_file, key_type?key_type:"PEM");
        return 0;
      }
      break;
    case SSL_FILETYPE_ENGINE:
#ifdef HAVE_OPENSSL_ENGINE_H
      {                         /* XXXX still needs some work */
        EVP_PKEY *priv_key = NULL;
        if(data->state.engine) {
          UI_METHOD *ui_method =
            UI_create_method((char *)"cURL user interface");
          if(!ui_method) {
            failf(data, "unable do create OpenSSL user-interface method");
            return 0;
          }
          UI_method_set_opener(ui_method, UI_method_get_opener(UI_OpenSSL()));
          UI_method_set_closer(ui_method, UI_method_get_closer(UI_OpenSSL()));
          UI_method_set_reader(ui_method, ssl_ui_reader);
          UI_method_set_writer(ui_method, ssl_ui_writer);
          /* the typecast below was added to please mingw32 */
          priv_key = (EVP_PKEY *)
            ENGINE_load_private_key(data->state.engine, key_file,
                                    ui_method,
                                    data->set.str[STRING_KEY_PASSWD]);
          UI_destroy_method(ui_method);
          if(!priv_key) {
            failf(data, "failed to load private key from crypto engine");
            return 0;
          }
          if(SSL_CTX_use_PrivateKey(ctx, priv_key) != 1) {
            failf(data, "unable to set private key");
            EVP_PKEY_free(priv_key);
            return 0;
          }
          EVP_PKEY_free(priv_key);  /* we don't need the handle any more... */
        }
        else {
          failf(data, "crypto engine not set, can't load private key");
          return 0;
        }
      }
      break;
#else
      failf(data, "file type ENG for private key not supported");
      return 0;
#endif
    case SSL_FILETYPE_PKCS12:
      if(!cert_done) {
        failf(data, "file type P12 for private key not supported");
        return 0;
      }
      break;
    default:
      failf(data, "not supported file type for private key");
      return 0;
    }

    ssl=SSL_new(ctx);
    if(!ssl) {
      failf(data, "unable to create an SSL structure");
      return 0;
    }

    x509=SSL_get_certificate(ssl);

    /* This version was provided by Evan Jordan and is supposed to not
       leak memory as the previous version: */
    if(x509) {
      EVP_PKEY *pktmp = X509_get_pubkey(x509);
      EVP_PKEY_copy_parameters(pktmp, SSL_get_privatekey(ssl));
      EVP_PKEY_free(pktmp);
    }

    SSL_free(ssl);

    /* If we are using DSA, we can copy the parameters from
     * the private key */


    /* Now we know that a key and cert have been set against
     * the SSL context */
    if(!SSL_CTX_check_private_key(ctx)) {
      failf(data, "Private key does not match the certificate public key");
      return 0;
    }
  }
  return 1;
}

/* returns non-zero on failure */
static int x509_name_oneline(X509_NAME *a, char *buf, size_t size)
{
#if 0
  return X509_NAME_oneline(a, buf, size);
#else
  BIO *bio_out = BIO_new(BIO_s_mem());
  BUF_MEM *biomem;
  int rc;

  if(!bio_out)
    return 1; /* alloc failed! */

  rc = X509_NAME_print_ex(bio_out, a, 0, XN_FLAG_SEP_SPLUS_SPC);
  BIO_get_mem_ptr(bio_out, &biomem);

  if((size_t)biomem->length < size)
    size = biomem->length;
  else
    size--; /* don't overwrite the buffer end */

  memcpy(buf, biomem->data, size);
  buf[size]=0;

  BIO_free(bio_out);

  return !rc;
#endif
}

/* Return error string for last OpenSSL error
 */
static char *SSL_strerror(unsigned long error, char *buf, size_t size)
{
  /* OpenSSL 0.9.6 and later has a function named
     ERR_error_string_n() that takes the size of the buffer as a
     third argument */
  ERR_error_string_n(error, buf, size);
  return buf;
}

/**
 * Global SSL init
 *
 * @retval 0 error initializing SSL
 * @retval 1 SSL initialized successfully
 */
int Curl_ossl_init(void)
{
  OPENSSL_load_builtin_modules();

#ifdef HAVE_ENGINE_LOAD_BUILTIN_ENGINES
  ENGINE_load_builtin_engines();
#endif

  /* OPENSSL_config(NULL); is "strongly recommended" to use but unfortunately
     that function makes an exit() call on wrongly formatted config files
     which makes it hard to use in some situations. OPENSSL_config() itself
     calls CONF_modules_load_file() and we use that instead and we ignore
     its return code! */

  /* CONF_MFLAGS_DEFAULT_SECTION introduced some time between 0.9.8b and
     0.9.8e */
#ifndef CONF_MFLAGS_DEFAULT_SECTION
#define CONF_MFLAGS_DEFAULT_SECTION 0x0
#endif

  CONF_modules_load_file(NULL, NULL,
                         CONF_MFLAGS_DEFAULT_SECTION|
                         CONF_MFLAGS_IGNORE_MISSING_FILE);

  /* Lets get nice error messages */
  SSL_load_error_strings();

  /* Init the global ciphers and digests */
  if(!SSLeay_add_ssl_algorithms())
    return 0;

  OpenSSL_add_all_algorithms();

  return 1;
}

/* Global cleanup */
void Curl_ossl_cleanup(void)
{
  /* Free ciphers and digests lists */
  EVP_cleanup();

#ifdef HAVE_ENGINE_CLEANUP
  /* Free engine list */
  ENGINE_cleanup();
#endif

#ifdef HAVE_CRYPTO_CLEANUP_ALL_EX_DATA
  /* Free OpenSSL ex_data table */
  CRYPTO_cleanup_all_ex_data();
#endif

  /* Free OpenSSL error strings */
  ERR_free_strings();

  /* Free thread local error state, destroying hash upon zero refcount */
#ifdef HAVE_ERR_REMOVE_THREAD_STATE
  ERR_remove_thread_state(NULL);
#else
  ERR_remove_state(0);
#endif

  /* Free all memory allocated by all configuration modules */
  CONF_modules_free();
}

/*
 * This function uses SSL_peek to determine connection status.
 *
 * Return codes:
 *     1 means the connection is still in place
 *     0 means the connection has been closed
 *    -1 means the connection status is unknown
 */
int Curl_ossl_check_cxn(struct connectdata *conn)
{
  int rc;
  char buf;

  rc = SSL_peek(conn->ssl[FIRSTSOCKET].handle, (void*)&buf, 1);
  if(rc > 0)
    return 1; /* connection still in place */

  if(rc == 0)
    return 0; /* connection has been closed */

  return -1; /* connection status unknown */
}

/* Selects an OpenSSL crypto engine
 */
CURLcode Curl_ossl_set_engine(struct SessionHandle *data, const char *engine)
{
#if defined(USE_OPENSSL) && defined(HAVE_OPENSSL_ENGINE_H)
  ENGINE *e;

#if OPENSSL_VERSION_NUMBER >= 0x00909000L
  e = ENGINE_by_id(engine);
#else
  /* avoid memory leak */
  for(e = ENGINE_get_first(); e; e = ENGINE_get_next(e)) {
    const char *e_id = ENGINE_get_id(e);
    if(!strcmp(engine, e_id))
      break;
  }
#endif

  if(!e) {
    failf(data, "SSL Engine '%s' not found", engine);
    return CURLE_SSL_ENGINE_NOTFOUND;
  }

  if(data->state.engine) {
    ENGINE_finish(data->state.engine);
    ENGINE_free(data->state.engine);
    data->state.engine = NULL;
  }
  if(!ENGINE_init(e)) {
    char buf[256];

    ENGINE_free(e);
    failf(data, "Failed to initialise SSL Engine '%s':\n%s",
          engine, SSL_strerror(ERR_get_error(), buf, sizeof(buf)));
    return CURLE_SSL_ENGINE_INITFAILED;
  }
  data->state.engine = e;
  return CURLE_OK;
#else
  (void)engine;
  failf(data, "SSL Engine not supported");
  return CURLE_SSL_ENGINE_NOTFOUND;
#endif
}

/* Sets engine as default for all SSL operations
 */
CURLcode Curl_ossl_set_engine_default(struct SessionHandle *data)
{
#ifdef HAVE_OPENSSL_ENGINE_H
  if(data->state.engine) {
    if(ENGINE_set_default(data->state.engine, ENGINE_METHOD_ALL) > 0) {
      infof(data, "set default crypto engine '%s'\n",
            ENGINE_get_id(data->state.engine));
    }
    else {
      failf(data, "set default crypto engine '%s' failed",
            ENGINE_get_id(data->state.engine));
      return CURLE_SSL_ENGINE_SETFAILED;
    }
  }
#else
  (void) data;
#endif
  return CURLE_OK;
}

/* Return list of OpenSSL crypto engine names.
 */
struct curl_slist *Curl_ossl_engines_list(struct SessionHandle *data)
{
  struct curl_slist *list = NULL;
#if defined(USE_OPENSSL) && defined(HAVE_OPENSSL_ENGINE_H)
  struct curl_slist *beg;
  ENGINE *e;

  for(e = ENGINE_get_first(); e; e = ENGINE_get_next(e)) {
    beg = curl_slist_append(list, ENGINE_get_id(e));
    if(!beg) {
      curl_slist_free_all(list);
      return NULL;
    }
    list = beg;
  }
#endif
  (void) data;
  return list;
}


/*
 * This function is called when an SSL connection is closed.
 */
void Curl_ossl_close(struct connectdata *conn, int sockindex)
{
  struct ssl_connect_data *connssl = &conn->ssl[sockindex];

  if(connssl->handle) {
    (void)SSL_shutdown(connssl->handle);
    SSL_set_connect_state(connssl->handle);

    SSL_free (connssl->handle);
    connssl->handle = NULL;
  }
  if(connssl->ctx) {
    SSL_CTX_free (connssl->ctx);
    connssl->ctx = NULL;
  }
}

/*
 * This function is called to shut down the SSL layer but keep the
 * socket open (CCC - Clear Command Channel)
 */
int Curl_ossl_shutdown(struct connectdata *conn, int sockindex)
{
  int retval = 0;
  struct ssl_connect_data *connssl = &conn->ssl[sockindex];
  struct SessionHandle *data = conn->data;
  char buf[120]; /* We will use this for the OpenSSL error buffer, so it has
                    to be at least 120 bytes long. */
  unsigned long sslerror;
  ssize_t nread;
  int buffsize;
  int err;
  int done = 0;

  /* This has only been tested on the proftpd server, and the mod_tls code
     sends a close notify alert without waiting for a close notify alert in
     response. Thus we wait for a close notify alert from the server, but
     we do not send one. Let's hope other servers do the same... */

  if(data->set.ftp_ccc == CURLFTPSSL_CCC_ACTIVE)
      (void)SSL_shutdown(connssl->handle);

  if(connssl->handle) {
    buffsize = (int)sizeof(buf);
    while(!done) {
      int what = Curl_socket_ready(conn->sock[sockindex],
                                   CURL_SOCKET_BAD, SSL_SHUTDOWN_TIMEOUT);
      if(what > 0) {
        ERR_clear_error();

        /* Something to read, let's do it and hope that it is the close
           notify alert from the server */
        nread = (ssize_t)SSL_read(conn->ssl[sockindex].handle, buf,
                                  buffsize);
        err = SSL_get_error(conn->ssl[sockindex].handle, (int)nread);

        switch(err) {
        case SSL_ERROR_NONE: /* this is not an error */
        case SSL_ERROR_ZERO_RETURN: /* no more data */
          /* This is the expected response. There was no data but only
             the close notify alert */
          done = 1;
          break;
        case SSL_ERROR_WANT_READ:
          /* there's data pending, re-invoke SSL_read() */
          infof(data, "SSL_ERROR_WANT_READ\n");
          break;
        case SSL_ERROR_WANT_WRITE:
          /* SSL wants a write. Really odd. Let's bail out. */
          infof(data, "SSL_ERROR_WANT_WRITE\n");
          done = 1;
          break;
        default:
          /* openssl/ssl.h says "look at error stack/return value/errno" */
          sslerror = ERR_get_error();
          failf(conn->data, "SSL read: %s, errno %d",
                ERR_error_string(sslerror, buf),
                SOCKERRNO);
          done = 1;
          break;
        }
      }
      else if(0 == what) {
        /* timeout */
        failf(data, "SSL shutdown timeout");
        done = 1;
      }
      else {
        /* anything that gets here is fatally bad */
        failf(data, "select/poll on SSL socket, errno: %d", SOCKERRNO);
        retval = -1;
        done = 1;
      }
    } /* while()-loop for the select() */

    if(data->set.verbose) {
#ifdef HAVE_SSL_GET_SHUTDOWN
      switch(SSL_get_shutdown(connssl->handle)) {
      case SSL_SENT_SHUTDOWN:
        infof(data, "SSL_get_shutdown() returned SSL_SENT_SHUTDOWN\n");
        break;
      case SSL_RECEIVED_SHUTDOWN:
        infof(data, "SSL_get_shutdown() returned SSL_RECEIVED_SHUTDOWN\n");
        break;
      case SSL_SENT_SHUTDOWN|SSL_RECEIVED_SHUTDOWN:
        infof(data, "SSL_get_shutdown() returned SSL_SENT_SHUTDOWN|"
              "SSL_RECEIVED__SHUTDOWN\n");
        break;
      }
#endif
    }

    SSL_free (connssl->handle);
    connssl->handle = NULL;
  }
  return retval;
}

void Curl_ossl_session_free(void *ptr)
{
  /* free the ID */
  SSL_SESSION_free(ptr);
}

/*
 * This function is called when the 'data' struct is going away. Close
 * down everything and free all resources!
 */
void Curl_ossl_close_all(struct SessionHandle *data)
{
#ifdef HAVE_OPENSSL_ENGINE_H
  if(data->state.engine) {
    ENGINE_finish(data->state.engine);
    ENGINE_free(data->state.engine);
    data->state.engine = NULL;
  }
#else
  (void)data;
#endif
}

/* ====================================================== */


/* Quote from RFC2818 section 3.1 "Server Identity"

   If a subjectAltName extension of type dNSName is present, that MUST
   be used as the identity. Otherwise, the (most specific) Common Name
   field in the Subject field of the certificate MUST be used. Although
   the use of the Common Name is existing practice, it is deprecated and
   Certification Authorities are encouraged to use the dNSName instead.

   Matching is performed using the matching rules specified by
   [RFC2459].  If more than one identity of a given type is present in