nss.c

  if(cert_dir) {
    char *certpath = aprintf("sql:%s", cert_dir);
    if(!certpath)
      return CURLE_OUT_OF_MEMORY;

    infof(data, "Initializing NSS with certpath: %s\n", certpath);
    nss_context = NSS_InitContext(certpath, "", "", "", &initparams,
            NSS_INIT_READONLY | NSS_INIT_PK11RELOAD);
    free(certpath);

    if(nss_context != NULL)
      return CURLE_OK;

    infof(data, "Unable to initialize NSS database\n");
  }

  infof(data, "Initializing NSS with certpath: none\n");
  nss_context = NSS_InitContext("", "", "", "", &initparams, NSS_INIT_READONLY
         | NSS_INIT_NOCERTDB   | NSS_INIT_NOMODDB       | NSS_INIT_FORCEOPEN
         | NSS_INIT_NOROOTINIT | NSS_INIT_OPTIMIZESPACE | NSS_INIT_PK11RELOAD);
  if(nss_context != NULL)
    return CURLE_OK;

  infof(data, "Unable to initialize NSS\n");
  return CURLE_SSL_CACERT_BADFILE;
}

static CURLcode nss_init(struct SessionHandle *data)
{
  char *cert_dir;
  struct_stat st;
  CURLcode rv;

  if(initialized)
    return CURLE_OK;

  /* list of all CRL items we need to destroy in Curl_nss_cleanup() */
  nss_crl_list = Curl_llist_alloc(nss_destroy_crl_item);
  if(!nss_crl_list)
    return CURLE_OUT_OF_MEMORY;

  /* First we check if $SSL_DIR points to a valid dir */
  cert_dir = getenv("SSL_DIR");
  if(cert_dir) {
    if((stat(cert_dir, &st) != 0) ||
        (!S_ISDIR(st.st_mode))) {
      cert_dir = NULL;
    }
  }

  /* Now we check if the default location is a valid dir */
  if(!cert_dir) {
    if((stat(SSL_DIR, &st) == 0) &&
        (S_ISDIR(st.st_mode))) {
      cert_dir = (char *)SSL_DIR;
    }
  }

  if(nspr_io_identity == PR_INVALID_IO_LAYER) {
    /* allocate an identity for our own NSPR I/O layer */
    nspr_io_identity = PR_GetUniqueIdentity("libcurl");
    if(nspr_io_identity == PR_INVALID_IO_LAYER)
      return CURLE_OUT_OF_MEMORY;

    /* the default methods just call down to the lower I/O layer */
    memcpy(&nspr_io_methods, PR_GetDefaultIOMethods(), sizeof nspr_io_methods);

    /* override certain methods in the table by our wrappers */
    nspr_io_methods.recv  = nspr_io_recv;
    nspr_io_methods.send  = nspr_io_send;
    nspr_io_methods.close = nspr_io_close;
  }

  rv = nss_init_core(data, cert_dir);
  if(rv)
    return rv;

  if(num_enabled_ciphers() == 0)
    NSS_SetDomesticPolicy();

  initialized = 1;
  return CURLE_OK;
}

/**
 * Global SSL init
 *
 * @retval 0 error initializing SSL
 * @retval 1 SSL initialized successfully
 */
int Curl_nss_init(void)
{
  /* curl_global_init() is not thread-safe so this test is ok */
  if(nss_initlock == NULL) {
    PR_Init(PR_USER_THREAD, PR_PRIORITY_NORMAL, 256);
    nss_initlock = PR_NewLock();
    nss_crllock = PR_NewLock();
  }

  /* We will actually initialize NSS later */

  return 1;
}

CURLcode Curl_nss_force_init(struct SessionHandle *data)
{
  CURLcode rv;
  if(!nss_initlock) {
    failf(data,
          "unable to initialize NSS, curl_global_init() should have been "
          "called with CURL_GLOBAL_SSL or CURL_GLOBAL_ALL");
    return CURLE_FAILED_INIT;
  }

  PR_Lock(nss_initlock);
  rv = nss_init(data);
  PR_Unlock(nss_initlock);
  return rv;
}

/* Global cleanup */
void Curl_nss_cleanup(void)
{
  /* This function isn't required to be threadsafe and this is only done
   * as a safety feature.
   */
  PR_Lock(nss_initlock);
  if(initialized) {
    /* Free references to client certificates held in the SSL session cache.
     * Omitting this hampers destruction of the security module owning
     * the certificates. */
    SSL_ClearSessionCache();

    if(mod && SECSuccess == SECMOD_UnloadUserModule(mod)) {
      SECMOD_DestroyModule(mod);
      mod = NULL;
    }
    NSS_ShutdownContext(nss_context);
    nss_context = NULL;
  }

  /* destroy all CRL items */
  Curl_llist_destroy(nss_crl_list, NULL);
  nss_crl_list = NULL;

  PR_Unlock(nss_initlock);

  PR_DestroyLock(nss_initlock);
  PR_DestroyLock(nss_crllock);
  nss_initlock = NULL;

  initialized = 0;
}

/*
 * 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_nss_check_cxn(struct connectdata *conn)
{
  int rc;
  char buf;

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

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

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

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

  if(connssl->handle) {
    /* NSS closes the socket we previously handed to it, so we must mark it
       as closed to avoid double close */
    fake_sclose(conn->sock[sockindex]);
    conn->sock[sockindex] = CURL_SOCKET_BAD;

    if((connssl->client_nickname != NULL) || (connssl->obj_clicert != NULL))
      /* A server might require different authentication based on the
       * particular path being requested by the client.  To support this
       * scenario, we must ensure that a connection will never reuse the
       * authentication data from a previous connection. */
      SSL_InvalidateSession(connssl->handle);

    if(connssl->client_nickname != NULL) {
      free(connssl->client_nickname);
      connssl->client_nickname = NULL;
    }
    /* destroy all NSS objects in order to avoid failure of NSS shutdown */
    Curl_llist_destroy(connssl->obj_list, NULL);
    connssl->obj_list = NULL;
    connssl->obj_clicert = NULL;

    PR_Close(connssl->handle);
    connssl->handle = NULL;
  }
}

/*
 * This function is called when the 'data' struct is going away. Close
 * down everything and free all resources!
 */
int Curl_nss_close_all(struct SessionHandle *data)
{
  (void)data;
  return 0;
}

/* return true if NSS can provide error code (and possibly msg) for the
   error */
static bool is_nss_error(CURLcode err)
{
  switch(err) {
  case CURLE_PEER_FAILED_VERIFICATION:
  case CURLE_SSL_CACERT:
  case CURLE_SSL_CERTPROBLEM:
  case CURLE_SSL_CONNECT_ERROR:
  case CURLE_SSL_ISSUER_ERROR:
    return true;

  default:
    return false;
  }
}

/* return true if the given error code is related to a client certificate */
static bool is_cc_error(PRInt32 err)
{
  switch(err) {
  case SSL_ERROR_BAD_CERT_ALERT:
  case SSL_ERROR_EXPIRED_CERT_ALERT:
  case SSL_ERROR_REVOKED_CERT_ALERT:
    return true;

  default:
    return false;
  }
}

static Curl_recv nss_recv;
static Curl_send nss_send;

static CURLcode nss_load_ca_certificates(struct connectdata *conn,
                                         int sockindex)
{
  struct SessionHandle *data = conn->data;
  const char *cafile = data->set.ssl.CAfile;
  const char *capath = data->set.ssl.CApath;

  if(cafile) {
    CURLcode rv = nss_load_cert(&conn->ssl[sockindex], cafile, PR_TRUE);
    if(CURLE_OK != rv)
      return rv;
  }

  if(capath) {
    struct_stat st;
    if(stat(capath, &st) == -1)
      return CURLE_SSL_CACERT_BADFILE;

    if(S_ISDIR(st.st_mode)) {
      PRDirEntry *entry;
      PRDir *dir = PR_OpenDir(capath);
      if(!dir)
        return CURLE_SSL_CACERT_BADFILE;

      while((entry = PR_ReadDir(dir, PR_SKIP_BOTH | PR_SKIP_HIDDEN))) {
        char *fullpath = aprintf("%s/%s", capath, entry->name);
        if(!fullpath) {
          PR_CloseDir(dir);
          return CURLE_OUT_OF_MEMORY;
        }

        if(CURLE_OK != nss_load_cert(&conn->ssl[sockindex], fullpath, PR_TRUE))
          /* This is purposefully tolerant of errors so non-PEM files can
           * be in the same directory */
          infof(data, "failed to load '%s' from CURLOPT_CAPATH\n", fullpath);

        free(fullpath);
      }

      PR_CloseDir(dir);
    }
    else
      infof(data, "warning: CURLOPT_CAPATH not a directory (%s)\n", capath);
  }

  infof(data, "  CAfile: %s\n  CApath: %s\n",
      cafile ? cafile : "none",
      capath ? capath : "none");

  return CURLE_OK;
}

static CURLcode nss_init_sslver(SSLVersionRange *sslver,
                                struct SessionHandle *data)
{
  switch (data->set.ssl.version) {
  default:
  case CURL_SSLVERSION_DEFAULT:
  case CURL_SSLVERSION_TLSv1:
    sslver->min = SSL_LIBRARY_VERSION_TLS_1_0;
#ifdef SSL_LIBRARY_VERSION_TLS_1_2
    sslver->max = SSL_LIBRARY_VERSION_TLS_1_2;
#elif defined SSL_LIBRARY_VERSION_TLS_1_1
    sslver->max = SSL_LIBRARY_VERSION_TLS_1_1;
#else
    sslver->max = SSL_LIBRARY_VERSION_TLS_1_0;
#endif
    return CURLE_OK;

  case CURL_SSLVERSION_SSLv2:
    sslver->min = SSL_LIBRARY_VERSION_2;
    sslver->max = SSL_LIBRARY_VERSION_2;
    return CURLE_OK;

  case CURL_SSLVERSION_SSLv3:
    sslver->min = SSL_LIBRARY_VERSION_3_0;
    sslver->max = SSL_LIBRARY_VERSION_3_0;
    return CURLE_OK;

  case CURL_SSLVERSION_TLSv1_0:
    sslver->min = SSL_LIBRARY_VERSION_TLS_1_0;
    sslver->max = SSL_LIBRARY_VERSION_TLS_1_0;
    return CURLE_OK;

  case CURL_SSLVERSION_TLSv1_1:
#ifdef SSL_LIBRARY_VERSION_TLS_1_1
    sslver->min = SSL_LIBRARY_VERSION_TLS_1_1;
    sslver->max = SSL_LIBRARY_VERSION_TLS_1_1;
    return CURLE_OK;
#endif
    break;

  case CURL_SSLVERSION_TLSv1_2:
#ifdef SSL_LIBRARY_VERSION_TLS_1_2
    sslver->min = SSL_LIBRARY_VERSION_TLS_1_2;
    sslver->max = SSL_LIBRARY_VERSION_TLS_1_2;
    return CURLE_OK;
#endif
    break;
  }

  failf(data, "TLS minor version cannot be set");
  return CURLE_SSL_CONNECT_ERROR;
}

static CURLcode nss_fail_connect(struct ssl_connect_data *connssl,
                                 struct SessionHandle *data,
                                 CURLcode curlerr)
{
  PRErrorCode err = 0;

  if(is_nss_error(curlerr)) {
    /* read NSPR error code */
    err = PR_GetError();
    if(is_cc_error(err))
      curlerr = CURLE_SSL_CERTPROBLEM;

    /* print the error number and error string */
    infof(data, "NSS error %d (%s)\n", err, nss_error_to_name(err));

    /* print a human-readable message describing the error if available */
    nss_print_error_message(data, err);
  }

  /* cleanup on connection failure */
  Curl_llist_destroy(connssl->obj_list, NULL);
  connssl->obj_list = NULL;
  return curlerr;
}

/* Switch the SSL socket into non-blocking mode. */
static CURLcode nss_set_nonblock(struct ssl_connect_data *connssl,
                                 struct SessionHandle *data)
{
  static PRSocketOptionData sock_opt;
  sock_opt.option = PR_SockOpt_Nonblocking;
  sock_opt.value.non_blocking = PR_TRUE;

  if(PR_SetSocketOption(connssl->handle, &sock_opt) != PR_SUCCESS)
    return nss_fail_connect(connssl, data, CURLE_SSL_CONNECT_ERROR);

  return CURLE_OK;
}

static CURLcode nss_setup_connect(struct connectdata *conn, int sockindex)
{
  PRFileDesc *model = NULL;
  PRFileDesc *nspr_io = NULL;
  PRFileDesc *nspr_io_stub = NULL;
  PRBool ssl_no_cache;
  PRBool ssl_cbc_random_iv;
  struct SessionHandle *data = conn->data;
  curl_socket_t sockfd = conn->sock[sockindex];
  struct ssl_connect_data *connssl = &conn->ssl[sockindex];
  CURLcode curlerr;

  SSLVersionRange sslver = {
    SSL_LIBRARY_VERSION_TLS_1_0,  /* min */
    SSL_LIBRARY_VERSION_TLS_1_0   /* max */
  };

#ifdef USE_NGHTTP2
#if defined(SSL_ENABLE_NPN) || defined(SSL_ENABLE_ALPN)
  unsigned int alpn_protos_len = NGHTTP2_PROTO_VERSION_ID_LEN +
      ALPN_HTTP_1_1_LENGTH + 2;
  unsigned char alpn_protos[NGHTTP2_PROTO_VERSION_ID_LEN + ALPN_HTTP_1_1_LENGTH
      + 2];
  int cur = 0;
#endif
#endif


  connssl->data = data;

  /* list of all NSS objects we need to destroy in Curl_nss_close() */
  connssl->obj_list = Curl_llist_alloc(nss_destroy_object);
  if(!connssl->obj_list)
    return CURLE_OUT_OF_MEMORY;

  /* FIXME. NSS doesn't support multiple databases open at the same time. */
  PR_Lock(nss_initlock);
  curlerr = nss_init(conn->data);
  if(CURLE_OK != curlerr) {
    PR_Unlock(nss_initlock);
    goto error;
  }

  curlerr = CURLE_SSL_CONNECT_ERROR;

  if(!mod) {
    char *configstring = aprintf("library=%s name=PEM", pem_library);
    if(!configstring) {
      PR_Unlock(nss_initlock);
      goto error;
    }
    mod = SECMOD_LoadUserModule(configstring, NULL, PR_FALSE);
    free(configstring);

    if(!mod || !mod->loaded) {
      if(mod) {
        SECMOD_DestroyModule(mod);
        mod = NULL;
      }
      infof(data, "WARNING: failed to load NSS PEM library %s. Using "
            "OpenSSL PEM certificates will not work.\n", pem_library);
    }
  }

  PK11_SetPasswordFunc(nss_get_password);
  PR_Unlock(nss_initlock);

  model = PR_NewTCPSocket();
  if(!model)
    goto error;
  model = SSL_ImportFD(NULL, model);

  if(SSL_OptionSet(model, SSL_SECURITY, PR_TRUE) != SECSuccess)
    goto error;
  if(SSL_OptionSet(model, SSL_HANDSHAKE_AS_SERVER, PR_FALSE) != SECSuccess)
    goto error;
  if(SSL_OptionSet(model, SSL_HANDSHAKE_AS_CLIENT, PR_TRUE) != SECSuccess)
    goto error;

  /* do not use SSL cache if disabled or we are not going to verify peer */
  ssl_no_cache = (conn->ssl_config.sessionid && data->set.ssl.verifypeer) ?
    PR_FALSE : PR_TRUE;
  if(SSL_OptionSet(model, SSL_NO_CACHE, ssl_no_cache) != SECSuccess)
    goto error;

  /* enable/disable the requested SSL version(s) */
  if(nss_init_sslver(&sslver, data) != CURLE_OK)
    goto error;
  if(SSL_VersionRangeSet(model, &sslver) != SECSuccess)
    goto error;

  ssl_cbc_random_iv = !data->set.ssl_enable_beast;
#ifdef SSL_CBC_RANDOM_IV
  /* unless the user explicitly asks to allow the protocol vulnerability, we
     use the work-around */
  if(SSL_OptionSet(model, SSL_CBC_RANDOM_IV, ssl_cbc_random_iv) != SECSuccess)
    infof(data, "warning: failed to set SSL_CBC_RANDOM_IV = %d\n",
          ssl_cbc_random_iv);
#else
  if(ssl_cbc_random_iv)
    infof(data, "warning: support for SSL_CBC_RANDOM_IV not compiled in\n");
#endif

  if(data->set.ssl.cipher_list) {
    if(set_ciphers(data, model, data->set.ssl.cipher_list) != SECSuccess) {
      curlerr = CURLE_SSL_CIPHER;
      goto error;
    }
  }

  if(!data->set.ssl.verifypeer && data->set.ssl.verifyhost)
    infof(data, "warning: ignoring value of ssl.verifyhost\n");

  /* bypass the default SSL_AuthCertificate() hook in case we do not want to
   * verify peer */
  if(SSL_AuthCertificateHook(model, nss_auth_cert_hook, conn) != SECSuccess)
    goto error;

  data->set.ssl.certverifyresult=0; /* not checked yet */
  if(SSL_BadCertHook(model, BadCertHandler, conn) != SECSuccess)
    goto error;

  if(SSL_HandshakeCallback(model, HandshakeCallback, conn) != SECSuccess)
    goto error;

  if(data->set.ssl.verifypeer) {
    const CURLcode rv = nss_load_ca_certificates(conn, sockindex);
    if(CURLE_OK != rv) {
      curlerr = rv;
      goto error;
    }
  }

  if(data->set.ssl.CRLfile) {
    const CURLcode rv = nss_load_crl(data->set.ssl.CRLfile);
    if(CURLE_OK != rv) {
      curlerr = rv;
      goto error;
    }
    infof(data, "  CRLfile: %s\n", data->set.ssl.CRLfile);
  }

  if(data->set.str[STRING_CERT]) {
    char *nickname = dup_nickname(data, STRING_CERT);
    if(nickname) {
      /* we are not going to use libnsspem.so to read the client cert */
      connssl->obj_clicert = NULL;
    }
    else {
      CURLcode rv = cert_stuff(conn, sockindex, data->set.str[STRING_CERT],
                               data->set.str[STRING_KEY]);
      if(CURLE_OK != rv) {
        /* failf() is already done in cert_stuff() */
        curlerr = rv;
        goto error;
      }
    }

    /* store the nickname for SelectClientCert() called during handshake */
    connssl->client_nickname = nickname;
  }
  else
    connssl->client_nickname = NULL;

  if(SSL_GetClientAuthDataHook(model, SelectClientCert,
                               (void *)connssl) != SECSuccess) {
    curlerr = CURLE_SSL_CERTPROBLEM;
    goto error;
  }

  /* wrap OS file descriptor by NSPR's file descriptor abstraction */
  nspr_io = PR_ImportTCPSocket(sockfd);
  if(!nspr_io)
    goto error;

  /* create our own NSPR I/O layer */
  nspr_io_stub = PR_CreateIOLayerStub(nspr_io_identity, &nspr_io_methods);
  if(!nspr_io_stub) {
    PR_Close(nspr_io);
    goto error;
  }

  /* make the per-connection data accessible from NSPR I/O callbacks */
  nspr_io_stub->secret = (void *)connssl;

  /* push our new layer to the NSPR I/O stack */
  if(PR_PushIOLayer(nspr_io, PR_TOP_IO_LAYER, nspr_io_stub) != PR_SUCCESS) {
    PR_Close(nspr_io);
    PR_Close(nspr_io_stub);
    goto error;
  }

  /* import our model socket onto the current I/O stack */
  connssl->handle = SSL_ImportFD(model, nspr_io);
  if(!connssl->handle) {
    PR_Close(nspr_io);
    goto error;
  }

  PR_Close(model); /* We don't need this any more */
  model = NULL;

  /* This is the password associated with the cert that we're using */
  if(data->set.str[STRING_KEY_PASSWD]) {
    SSL_SetPKCS11PinArg(connssl->handle, data->set.str[STRING_KEY_PASSWD]);
  }

#ifdef USE_NGHTTP2
  if(data->set.httpversion == CURL_HTTP_VERSION_2_0) {
#ifdef SSL_ENABLE_NPN
    if(data->set.ssl_enable_npn) {
      if(SSL_OptionSet(connssl->handle, SSL_ENABLE_NPN, PR_TRUE) != SECSuccess)
        goto error;
    }
#endif

#ifdef SSL_ENABLE_ALPN
    if(data->set.ssl_enable_alpn) {
      if(SSL_OptionSet(connssl->handle, SSL_ENABLE_ALPN, PR_TRUE)
          != SECSuccess)
        goto error;
    }
#endif

#if defined(SSL_ENABLE_NPN) || defined(SSL_ENABLE_ALPN)
    if(data->set.ssl_enable_npn || data->set.ssl_enable_alpn) {
      alpn_protos[cur] = NGHTTP2_PROTO_VERSION_ID_LEN;
      cur++;
      memcpy(&alpn_protos[cur], NGHTTP2_PROTO_VERSION_ID,
          NGHTTP2_PROTO_VERSION_ID_LEN);
      cur += NGHTTP2_PROTO_VERSION_ID_LEN;
      alpn_protos[cur] = ALPN_HTTP_1_1_LENGTH;
      cur++;
      memcpy(&alpn_protos[cur], ALPN_HTTP_1_1, ALPN_HTTP_1_1_LENGTH);

      if(SSL_SetNextProtoNego(connssl->handle, alpn_protos, alpn_protos_len)
          != SECSuccess)
        goto error;
    }
    else {
      infof(data, "SSL, can't negotiate HTTP/2.0 with neither NPN nor ALPN\n");
    }
#endif
  }
#endif


  /* Force handshake on next I/O */
  SSL_ResetHandshake(connssl->handle, /* asServer */ PR_FALSE);

  SSL_SetURL(connssl->handle, conn->host.name);

  return CURLE_OK;

error:
  if(model)
    PR_Close(model);

  return nss_fail_connect(connssl, data, curlerr);
}

static CURLcode nss_do_connect(struct connectdata *conn, int sockindex)
{
  struct ssl_connect_data *connssl = &conn->ssl[sockindex];
  struct SessionHandle *data = conn->data;
  CURLcode curlerr = CURLE_SSL_CONNECT_ERROR;
  PRUint32 timeout;

  /* check timeout situation */
  const long time_left = Curl_timeleft(data, NULL, TRUE);
  if(time_left < 0L) {
    failf(data, "timed out before SSL handshake");
    curlerr = CURLE_OPERATION_TIMEDOUT;
    goto error;
  }

  /* Force the handshake now */
  timeout = PR_MillisecondsToInterval((PRUint32) time_left);
  if(SSL_ForceHandshakeWithTimeout(connssl->handle, timeout) != SECSuccess) {
    if(PR_GetError() == PR_WOULD_BLOCK_ERROR)
      /* blocking direction is updated by nss_update_connecting_state() */
      return CURLE_AGAIN;
    else if(conn->data->set.ssl.certverifyresult == SSL_ERROR_BAD_CERT_DOMAIN)
      curlerr = CURLE_PEER_FAILED_VERIFICATION;
    else if(conn->data->set.ssl.certverifyresult!=0)
      curlerr = CURLE_SSL_CACERT;
    goto error;
  }

  display_conn_info(conn, connssl->handle);

  if(data->set.str[STRING_SSL_ISSUERCERT]) {
    SECStatus ret = SECFailure;
    char *nickname = dup_nickname(data, STRING_SSL_ISSUERCERT);
    if(nickname) {
      /* we support only nicknames in case of STRING_SSL_ISSUERCERT for now */
      ret = check_issuer_cert(connssl->handle, nickname);
      free(nickname);
    }

    if(SECFailure == ret) {
      infof(data,"SSL certificate issuer check failed\n");
      curlerr = CURLE_SSL_ISSUER_ERROR;
      goto error;
    }
    else {
      infof(data, "SSL certificate issuer check ok\n");
    }
  }

  return CURLE_OK;

error:
  return nss_fail_connect(connssl, data, curlerr);
}

static CURLcode nss_connect_common(struct connectdata *conn, int sockindex,
                                   bool *done)
{
  struct ssl_connect_data *connssl = &conn->ssl[sockindex];
  struct SessionHandle *data = conn->data;
  const bool blocking = (done == NULL);
  CURLcode rv;

  if(connssl->state == ssl_connection_complete)
    return CURLE_OK;

  if(connssl->connecting_state == ssl_connect_1) {
    rv = nss_setup_connect(conn, sockindex);
    if(rv)
      /* we do not expect CURLE_AGAIN from nss_setup_connect() */
      return rv;

    if(!blocking) {
      /* in non-blocking mode, set NSS non-blocking mode before handshake */
      rv = nss_set_nonblock(connssl, data);
      if(rv)
        return rv;
    }

    connssl->connecting_state = ssl_connect_2;
  }

  rv = nss_do_connect(conn, sockindex);
  switch(rv) {
  case CURLE_OK:
    break;
  case CURLE_AGAIN:
    if(!blocking)
      /* CURLE_AGAIN in non-blocking mode is not an error */
      return CURLE_OK;
    /* fall through */
  default:
    return rv;
  }

  if(blocking) {
    /* in blocking mode, set NSS non-blocking mode _after_ SSL handshake */
    rv = nss_set_nonblock(connssl, data);
    if(rv)
      return rv;
  }
  else
    /* signal completed SSL handshake */
    *done = TRUE;

  connssl->state = ssl_connection_complete;
  conn->recv[sockindex] = nss_recv;
  conn->send[sockindex] = nss_send;

  /* ssl_connect_done is never used outside, go back to the initial state */
  connssl->connecting_state = ssl_connect_1;
  return CURLE_OK;
}

CURLcode Curl_nss_connect(struct connectdata *conn, int sockindex)
{
  return nss_connect_common(conn, sockindex, /* blocking */ NULL);
}

CURLcode Curl_nss_connect_nonblocking(struct connectdata *conn,
                                      int sockindex, bool *done)
{
  return nss_connect_common(conn, sockindex, done);
}

static ssize_t nss_send(struct connectdata *conn,  /* connection data */
                        int sockindex,             /* socketindex */
                        const void *mem,           /* send this data */
                        size_t len,                /* amount to write */
                        CURLcode *curlcode)
{
  ssize_t rc = PR_Send(conn->ssl[sockindex].handle, mem, (int)len, 0,
                       PR_INTERVAL_NO_WAIT);
  if(rc < 0) {
    PRInt32 err = PR_GetError();
    if(err == PR_WOULD_BLOCK_ERROR)
      *curlcode = CURLE_AGAIN;
    else {
      /* print the error number and error string */
      const char *err_name = nss_error_to_name(err);
      infof(conn->data, "SSL write: error %d (%s)\n", err, err_name);

      /* print a human-readable message describing the error if available */
      nss_print_error_message(conn->data, err);

      *curlcode = (is_cc_error(err))
        ? CURLE_SSL_CERTPROBLEM
        : CURLE_SEND_ERROR;
    }
    return -1;
  }
  return rc; /* number of bytes */
}

static ssize_t nss_recv(struct connectdata * conn, /* connection data */
                        int num,                   /* socketindex */
                        char *buf,                 /* store read data here */
                        size_t buffersize,         /* max amount to read */
                        CURLcode *curlcode)
{
  ssize_t nread = PR_Recv(conn->ssl[num].handle, buf, (int)buffersize, 0,
                          PR_INTERVAL_NO_WAIT);
  if(nread < 0) {
    /* failed SSL read */
    PRInt32 err = PR_GetError();

    if(err == PR_WOULD_BLOCK_ERROR)
      *curlcode = CURLE_AGAIN;
    else {
      /* print the error number and error string */
      const char *err_name = nss_error_to_name(err);
      infof(conn->data, "SSL read: errno %d (%s)\n", err, err_name);

      /* print a human-readable message describing the error if available */
      nss_print_error_message(conn->data, err);

      *curlcode = (is_cc_error(err))
        ? CURLE_SSL_CERTPROBLEM
        : CURLE_RECV_ERROR;
    }
    return -1;
  }
  return nread;
}

size_t Curl_nss_version(char *buffer, size_t size)
{
  return snprintf(buffer, size, "NSS/%s", NSS_VERSION);
}

int Curl_nss_seed(struct SessionHandle *data)
{
  /* make sure that NSS is initialized */
  return !!Curl_nss_force_init(data);
}

/* data might be NULL */
int Curl_nss_random(struct SessionHandle *data,
                    unsigned char *entropy,
                    size_t length)
{
  if(data)
    Curl_nss_seed(data);  /* Initiate the seed if not already done */
  if(SECSuccess != PK11_GenerateRandom(entropy, curlx_uztosi(length))) {
    /* no way to signal a failure from here, we have to abort */
    failf(data, "PK11_GenerateRandom() failed, calling abort()...");
    abort();
  }
  return 0;
}

void Curl_nss_md5sum(unsigned char *tmp, /* input */
                     size_t tmplen,
                     unsigned char *md5sum, /* output */
                     size_t md5len)
{
  PK11Context *MD5pw = PK11_CreateDigestContext(SEC_OID_MD5);
  unsigned int MD5out;
  PK11_DigestOp(MD5pw, tmp, curlx_uztoui(tmplen));
  PK11_DigestFinal(MD5pw, md5sum, &MD5out, curlx_uztoui(md5len));
  PK11_DestroyContext(MD5pw, PR_TRUE);
}

#endif /* USE_NSS */