/*

 * socket.c - socket functions for the library

 *

 * This file is part of the SSH Library

 *

 * Copyright (c) 2008-2010      by Aris Adamantiadis

 *

 * The SSH Library is free software; you can redistribute it and/or modify

 * it under the terms of the GNU Lesser General Public License as published by

 * the Free Software Foundation; either version 2.1 of the License, or (at your

 * option) any later version.

 *

 * The SSH Library 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 Lesser General Public

 * License for more details.

 *

 * You should have received a copy of the GNU Lesser General Public License

 * along with the SSH Library; see the file COPYING.  If not, write to

 * the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,

 * MA 02111-1307, USA.

 */

#include "config.h"

#include <errno.h>

#include <stdio.h>

#ifdef _WIN32

#include <winsock2.h>

#include <ws2tcpip.h>

#if _MSC_VER >= 1400

#include <io.h>

#undef open

#define open _open

#undef close

#define close _close

#undef read

#define read _read

#undef write

#define write _write

#endif /* _MSC_VER */

#else /* _WIN32 */

#include <fcntl.h>

#include <sys/types.h>

#include <sys/wait.h>

#include <sys/socket.h>

#include <sys/un.h>

#include <signal.h>

#endif /* _WIN32 */

#include "libssh/priv.h"

#include "libssh/callbacks.h"

#include "libssh/socket.h"

#include "libssh/buffer.h"

#include "libssh/poll.h"

#include "libssh/session.h"

/**

 * @internal

 *

 * @defgroup libssh_socket The SSH socket functions.

 * @ingroup libssh

 *

 * Functions for handling sockets.

 *

 * @{

 */

enum ssh_socket_states_e {

	SSH_SOCKET_NONE,

	SSH_SOCKET_CONNECTING,

	SSH_SOCKET_CONNECTED,

	SSH_SOCKET_EOF,

	SSH_SOCKET_ERROR,

	SSH_SOCKET_CLOSED

};

struct ssh_socket_struct {

  socket_t fd;

  int fd_is_socket;

  int last_errno;

  int read_wontblock; /* reading now on socket will

                       not block */

  int write_wontblock;

  int data_except;

  enum ssh_socket_states_e state;

  ssh_buffer out_buffer;

  ssh_buffer in_buffer;

  ssh_session session;

  ssh_socket_callbacks callbacks;

  ssh_poll_handle poll_handle;

#ifndef _WIN32

  pid_t proxy_pid;

#endif

};

static int sockets_initialized = 0;

static ssize_t ssh_socket_unbuffered_read(ssh_socket s,

                                          void *buffer,

                                          uint32_t len);

static ssize_t ssh_socket_unbuffered_write(ssh_socket s,

                                           const void *buffer,

                                           uint32_t len);

/**

 * \internal

 * \brief inits the socket system (windows specific)

 */

int ssh_socket_init(void)

{

    if (sockets_initialized == 0) {

#ifdef _WIN32

        struct WSAData wsaData;

        /* Initiates use of the Winsock DLL by a process. */

        if (WSAStartup(MAKEWORD(2, 0), &wsaData) != 0) {

            return -1;

        }

#endif

        ssh_poll_init();

        sockets_initialized = 1;

    }

    return 0;

}

/**

 * @brief Cleanup the socket system.

 */

void ssh_socket_cleanup(void)

{

    if (sockets_initialized == 1) {

        ssh_poll_cleanup();

#ifdef _WIN32

        WSACleanup();

#endif

        sockets_initialized = 0;

    }

}

/**

 * \internal

 * \brief creates a new Socket object

 */

ssh_socket ssh_socket_new(ssh_session session)

{

    ssh_socket s;

    s = calloc(1, sizeof(struct ssh_socket_struct));

    if (s == NULL) {

        ssh_set_error_oom(session);

        return NULL;

    }

    s->fd = SSH_INVALID_SOCKET;

    s->last_errno = -1;

    s->fd_is_socket = 1;

    s->session = session;

    s->in_buffer = ssh_buffer_new();

    if (s->in_buffer == NULL) {

        ssh_set_error_oom(session);

        SAFE_FREE(s);

        return NULL;

    }

    s->out_buffer=ssh_buffer_new();

    if (s->out_buffer == NULL) {

        ssh_set_error_oom(session);

        SSH_BUFFER_FREE(s->in_buffer);

        SAFE_FREE(s);

        return NULL;

    }

    s->read_wontblock = 0;

    s->write_wontblock = 0;

    s->data_except = 0;

    s->poll_handle = NULL;

    s->state=SSH_SOCKET_NONE;

    return s;

}

/**

 * @internal

 * @brief Reset the state of a socket so it looks brand-new

 * @param[in] s socket to rest

 */

void ssh_socket_reset(ssh_socket s)

{

    s->fd = SSH_INVALID_SOCKET;

    s->last_errno = -1;

    s->fd_is_socket = 1;

    ssh_buffer_reinit(s->in_buffer);

    ssh_buffer_reinit(s->out_buffer);

    s->read_wontblock = 0;

    s->write_wontblock = 0;

    s->data_except = 0;

    s->poll_handle = NULL;

    s->state=SSH_SOCKET_NONE;

#ifndef _WIN32

    s->proxy_pid = 0;

#endif

}

/**

 * @internal

 * @brief the socket callbacks, i.e. callbacks to be called

 * upon a socket event.

 * @param s socket to set callbacks on.

 * @param callbacks a ssh_socket_callback object reference.

 */

void ssh_socket_set_callbacks(ssh_socket s, ssh_socket_callbacks callbacks)

{

    s->callbacks = callbacks;

}

/**

 * @brief               SSH poll callback. This callback will be used when an event

 *                      caught on the socket.

 *

 * @param p             Poll object this callback belongs to.

 * @param fd            The raw socket.

 * @param revents       The current poll events on the socket.

 * @param userdata      Userdata to be passed to the callback function,

 *                      in this case the socket object.

 *

 * @return              0 on success, < 0 when the poll object has been removed

 *                      from its poll context.

 */

int ssh_socket_pollcallback(struct ssh_poll_handle_struct *p,

                            socket_t fd,

                            int revents,

                            void *v_s)

{

    ssh_socket s = (ssh_socket)v_s;

    char buffer[MAX_BUF_SIZE];

    ssize_t nread;

    int rc;

    int err = 0;

    socklen_t errlen = sizeof(err);

    /* Do not do anything if this socket was already closed */

    if (!ssh_socket_is_open(s)) {

        return -1;

    }

    SSH_LOG(SSH_LOG_TRACE, "Poll callback on socket %d (%s%s%s), out buffer %d",fd,

            (revents & POLLIN) ? "POLLIN ":"",

            (revents & POLLOUT) ? "POLLOUT ":"",

            (revents & POLLERR) ? "POLLERR":"",

            ssh_buffer_get_len(s->out_buffer));

    if ((revents & POLLERR) || (revents & POLLHUP)) {

        /* Check if we are in a connecting state */

        if (s->state == SSH_SOCKET_CONNECTING) {

            s->state = SSH_SOCKET_ERROR;

            rc = getsockopt(fd, SOL_SOCKET, SO_ERROR, (char *)&err, &errlen);

            if (rc < 0) {

                err = errno;

            }

            ssh_socket_close(s);

            /* Overwrite ssh_socket_close() error with the real socket error */

            s->last_errno = err;

            errno = err;

            if (s->callbacks != NULL && s->callbacks->connected != NULL) {

                s->callbacks->connected(SSH_SOCKET_CONNECTED_ERROR,

                                        err,

                                        s->callbacks->userdata);

            }

            return -1;

        }

        /* Then we are in a more standard kind of error */

        /* force a read to get an explanation */

        revents |= POLLIN;

    }

    if ((revents & POLLIN) && s->state == SSH_SOCKET_CONNECTED) {

        s->read_wontblock = 1;

        nread = ssh_socket_unbuffered_read(s, buffer, sizeof(buffer));

        if (nread < 0) {

            if (p != NULL) {

                ssh_poll_remove_events(p, POLLIN);

            }

            if (s->callbacks != NULL && s->callbacks->exception != NULL) {

                s->callbacks->exception(SSH_SOCKET_EXCEPTION_ERROR,

                                        s->last_errno,

                                        s->callbacks->userdata);

            }

            return -2;

        }

        if (nread == 0) {

            if (p != NULL) {

                ssh_poll_remove_events(p, POLLIN);

            }

            if (s->callbacks != NULL && s->callbacks->exception != NULL) {

                s->callbacks->exception(SSH_SOCKET_EXCEPTION_EOF,

                                        0,

                                        s->callbacks->userdata);

            }

            return -2;

        }

        if (s->session->socket_counter != NULL) {

            s->session->socket_counter->in_bytes += nread;

        }

        /* Bufferize the data and then call the callback */

        rc = ssh_buffer_add_data(s->in_buffer, buffer, nread);

        if (rc < 0) {

            return -1;

        }

        if (s->callbacks != NULL && s->callbacks->data != NULL) {

            do {

                nread = s->callbacks->data(ssh_buffer_get(s->in_buffer),

                                       ssh_buffer_get_len(s->in_buffer),

                                       s->callbacks->userdata);

                ssh_buffer_pass_bytes(s->in_buffer, nread);

            } while ((nread > 0) && (s->state == SSH_SOCKET_CONNECTED));

            /* p may have been freed, so don't use it

             * anymore in this function */

            p = NULL;

        }

    }

#ifdef _WIN32

    if (revents & POLLOUT || revents & POLLWRNORM) {

#else

    if (revents & POLLOUT) {

#endif

        uint32_t len;

        /* First, POLLOUT is a sign we may be connected */

        if (s->state == SSH_SOCKET_CONNECTING) {

            SSH_LOG(SSH_LOG_PACKET, "Received POLLOUT in connecting state");

            s->state = SSH_SOCKET_CONNECTED;

            if (p != NULL) {

                ssh_poll_set_events(p, POLLOUT | POLLIN);

            }

            rc = ssh_socket_set_blocking(ssh_socket_get_fd(s));

            if (rc < 0) {

                return -1;

            }

            if (s->callbacks != NULL && s->callbacks->connected != NULL) {

                s->callbacks->connected(SSH_SOCKET_CONNECTED_OK,

                                        0,

                                        s->callbacks->userdata);

            }

            return 0;

        }

        /* So, we can write data */

        s->write_wontblock = 1;

        if (p != NULL) {

            ssh_poll_remove_events(p, POLLOUT);

        }

        /* If buffered data is pending, write it */

        len = ssh_buffer_get_len(s->out_buffer);

        if (len > 0) {

            ssh_socket_nonblocking_flush(s);

        } else if (s->callbacks != NULL && s->callbacks->controlflow != NULL) {

            /* Otherwise advertise the upper level that write can be done */

            SSH_LOG(SSH_LOG_TRACE,"sending control flow event");

            s->callbacks->controlflow(SSH_SOCKET_FLOW_WRITEWONTBLOCK,

                                      s->callbacks->userdata);

        }

        /* TODO: Find a way to put back POLLOUT when buffering occurs */

    }

    /* Return -1 if the poll handler disappeared */

    if (s->poll_handle == NULL) {

        return -1;

    }

    return 0;

}

/** @internal

 * @brief returns the poll handle corresponding to the socket,

 * creates it if it does not exist.

 * @returns allocated and initialized ssh_poll_handle object

 */

ssh_poll_handle ssh_socket_get_poll_handle(ssh_socket s)

{

    if (s->poll_handle) {

        return s->poll_handle;

    }

    s->poll_handle = ssh_poll_new(s->fd,0,ssh_socket_pollcallback,s);

    return s->poll_handle;

}

/** \internal

 * \brief Deletes a socket object

 */

void ssh_socket_free(ssh_socket s)

{

    if (s == NULL) {

        return;

    }

    ssh_socket_close(s);

    SSH_BUFFER_FREE(s->in_buffer);

    SSH_BUFFER_FREE(s->out_buffer);

    SAFE_FREE(s);

}

#ifndef _WIN32

int ssh_socket_unix(ssh_socket s, const char *path)

{

    struct sockaddr_un sunaddr;

    socket_t fd;

    sunaddr.sun_family = AF_UNIX;

    snprintf(sunaddr.sun_path, sizeof(sunaddr.sun_path), "%s", path);

    fd = socket(AF_UNIX, SOCK_STREAM, 0);

    if (fd == SSH_INVALID_SOCKET) {

        ssh_set_error(s->session, SSH_FATAL,

                      "Error from socket(AF_UNIX, SOCK_STREAM, 0): %s",

                      strerror(errno));

        return -1;

    }

    if (fcntl(fd, F_SETFD, 1) == -1) {

        ssh_set_error(s->session, SSH_FATAL,

                      "Error from fcntl(fd, F_SETFD, 1): %s",

                      strerror(errno));

        close(fd);

        return -1;

    }

    if (connect(fd, (struct sockaddr *) &sunaddr, sizeof(sunaddr)) < 0) {

        ssh_set_error(s->session, SSH_FATAL, "Error from connect(): %s",

                      strerror(errno));

        close(fd);

        return -1;

    }

    ssh_socket_set_fd(s,fd);

    return 0;

}

#endif

/** \internal

 * \brief closes a socket

 */

void ssh_socket_close(ssh_socket s)

{

    if (ssh_socket_is_open(s)) {

#ifdef _WIN32

        CLOSE_SOCKET(s->fd);

        s->last_errno = WSAGetLastError();

#else

        CLOSE_SOCKET(s->fd);

        s->last_errno = errno;

#endif

    }

    if (s->poll_handle != NULL) {

        ssh_poll_free(s->poll_handle);

        s->poll_handle = NULL;

    }

    s->state = SSH_SOCKET_CLOSED;

#ifndef _WIN32

    /* If the proxy command still runs try to kill it */

    if (s->proxy_pid != 0) {

        int status;

        pid_t pid = s->proxy_pid;

        s->proxy_pid = 0;

        kill(pid, SIGTERM);

        while (waitpid(pid, &status, 0) == -1) {

            if (errno != EINTR) {

                SSH_LOG(SSH_LOG_WARN, "waitpid failed: %s", strerror(errno));

                return;

            }

        }

        if (!WIFEXITED(status)) {

            SSH_LOG(SSH_LOG_WARN, "Proxy command exitted abnormally");

            return;

        }

        SSH_LOG(SSH_LOG_TRACE, "Proxy command returned %d", WEXITSTATUS(status));

    }

#endif

}

/**

 * @internal

 * @brief sets the file descriptor of the socket.

 * @param[out] s ssh_socket to update

 * @param[in] fd file descriptor to set

 * @warning this function updates boths the input and output

 * file descriptors

 */

void ssh_socket_set_fd(ssh_socket s, socket_t fd)

{

    s->fd = fd;

    if (s->poll_handle) {

        ssh_poll_set_fd(s->poll_handle,fd);

    } else {

        s->state = SSH_SOCKET_CONNECTING;

        /* POLLOUT is the event to wait for in a nonblocking connect */

        ssh_poll_set_events(ssh_socket_get_poll_handle(s), POLLOUT);

#ifdef _WIN32

        ssh_poll_add_events(ssh_socket_get_poll_handle(s), POLLWRNORM);

#endif

    }

}

/** \internal

 * \brief returns the input file descriptor of the socket

 */

socket_t ssh_socket_get_fd(ssh_socket s)

{

    return s->fd;

}

/** \internal

 * \brief returns nonzero if the socket is open

 */

int ssh_socket_is_open(ssh_socket s)

{

    return s->fd != SSH_INVALID_SOCKET;

}

/** \internal

 * \brief read len bytes from socket into buffer

 */

static ssize_t ssh_socket_unbuffered_read(ssh_socket s,

                                          void *buffer,

                                          uint32_t len)

{

    ssize_t rc = -1;

    if (s->data_except) {

        return -1;

    }

    if (s->fd_is_socket) {

        rc = recv(s->fd,buffer, len, 0);

    } else {

        rc = read(s->fd,buffer, len);

    }

#ifdef _WIN32

    s->last_errno = WSAGetLastError();

#else

    s->last_errno = errno;

#endif

    s->read_wontblock = 0;

    if (rc < 0) {

        s->data_except = 1;

    }

    return rc;

}

/** \internal

 * \brief writes len bytes from buffer to socket

 */

static ssize_t ssh_socket_unbuffered_write(ssh_socket s,

                                           const void *buffer,

                                           uint32_t len)

{

    ssize_t w = -1;

    int flags = 0;

#ifdef MSG_NOSIGNAL

    flags |= MSG_NOSIGNAL;

#endif

    if (s->data_except) {

        return -1;

    }

    if (s->fd_is_socket) {

        w = send(s->fd, buffer, len, flags);

    } else {

        w = write(s->fd, buffer, len);

    }

#ifdef _WIN32

    s->last_errno = WSAGetLastError();

#else

    s->last_errno = errno;

#endif

    s->write_wontblock = 0;

    /* Reactive the POLLOUT detector in the poll multiplexer system */

    if (s->poll_handle) {

        SSH_LOG(SSH_LOG_PACKET, "Enabling POLLOUT for socket");

        ssh_poll_set_events(s->poll_handle,ssh_poll_get_events(s->poll_handle) | POLLOUT);

    }

    if (w < 0) {

        s->data_except = 1;

    }

    return w;

}

/** \internal

 * \brief returns nonzero if the current socket is in the fd_set

 */

int ssh_socket_fd_isset(ssh_socket s, fd_set *set)

{

    if(s->fd == SSH_INVALID_SOCKET) {

        return 0;

    }

    return FD_ISSET(s->fd,set);

}

/** \internal

 * \brief sets the current fd in a fd_set and updates the max_fd

 */

void ssh_socket_fd_set(ssh_socket s, fd_set *set, socket_t *max_fd)

{

    if (s->fd == SSH_INVALID_SOCKET) {

        return;

    }

    FD_SET(s->fd,set);

    if (s->fd >= 0 &&

        s->fd >= *max_fd &&

        s->fd != SSH_INVALID_SOCKET) {

        *max_fd = s->fd + 1;

    }

}

/** \internal

 * \brief buffered write of data

 * \returns SSH_OK, or SSH_ERROR

 * \warning has no effect on socket before a flush

 */

int ssh_socket_write(ssh_socket s, const void *buffer, int len)

{

    if (len > 0) {

        if (ssh_buffer_add_data(s->out_buffer, buffer, len) < 0) {

            ssh_set_error_oom(s->session);

            return SSH_ERROR;

        }

        ssh_socket_nonblocking_flush(s);

    }

    return SSH_OK;

}

/** \internal

 * \brief starts a nonblocking flush of the output buffer

 *

 */

int ssh_socket_nonblocking_flush(ssh_socket s)

{

    ssh_session session = s->session;

    uint32_t len;

    if (!ssh_socket_is_open(s)) {

        session->alive = 0;

        if (s->callbacks && s->callbacks->exception) {

            s->callbacks->exception(SSH_SOCKET_EXCEPTION_ERROR,

                                    s->last_errno,

                                    s->callbacks->userdata);

        } else {

            ssh_set_error(session,

                          SSH_FATAL,

                          "Writing packet: error on socket (or connection "

                          "closed): %s",

                          strerror(s->last_errno));

        }

        return SSH_ERROR;

    }

    len = ssh_buffer_get_len(s->out_buffer);

    if (!s->write_wontblock && s->poll_handle && len > 0) {

        /* force the poll system to catch pollout events */

        ssh_poll_add_events(s->poll_handle, POLLOUT);

        return SSH_AGAIN;

    }

    if (s->write_wontblock && len > 0) {

        ssize_t bwritten;

        bwritten = ssh_socket_unbuffered_write(s,

                                               ssh_buffer_get(s->out_buffer),

                                               len);

        if (bwritten < 0) {

            session->alive = 0;

            ssh_socket_close(s);

            if (s->callbacks && s->callbacks->exception) {

                s->callbacks->exception(SSH_SOCKET_EXCEPTION_ERROR,

                                        s->last_errno,

                                        s->callbacks->userdata);

            } else {

                ssh_set_error(session,

                              SSH_FATAL,

                              "Writing packet: error on socket (or connection "

                              "closed): %s",

                              strerror(s->last_errno));

            }

            return SSH_ERROR;

        }

        ssh_buffer_pass_bytes(s->out_buffer, bwritten);

        if (s->session->socket_counter != NULL) {

            s->session->socket_counter->out_bytes += bwritten;

        }

    }

    /* Is there some data pending? */

    len = ssh_buffer_get_len(s->out_buffer);

    if (s->poll_handle && len > 0) {

        /* force the poll system to catch pollout events */

        ssh_poll_add_events(s->poll_handle, POLLOUT);

        return SSH_AGAIN;

    }

    /* all data written */

    return SSH_OK;

}

void ssh_socket_set_write_wontblock(ssh_socket s)

{

    s->write_wontblock = 1;

}

void ssh_socket_set_read_wontblock(ssh_socket s)

{

    s->read_wontblock = 1;

}

void ssh_socket_set_except(ssh_socket s)

{

    s->data_except = 1;

}

int ssh_socket_data_available(ssh_socket s)

{

    return s->read_wontblock;

}

int ssh_socket_data_writable(ssh_socket s)

{

    return s->write_wontblock;

}

/** @internal

 * @brief returns the number of outgoing bytes currently buffered

 * @param s the socket

 * @returns numbers of bytes buffered, or 0 if the socket isn't connected

 */

int ssh_socket_buffered_write_bytes(ssh_socket s)

{

    if (s==NULL || s->out_buffer == NULL) {

        return 0;

    }

    return ssh_buffer_get_len(s->out_buffer);

}

int ssh_socket_get_status(ssh_socket s)

{

    int r = 0;

    if (ssh_buffer_get_len(s->in_buffer) > 0) {

        r |= SSH_READ_PENDING;

    }

    if (ssh_buffer_get_len(s->out_buffer) > 0) {

        r |= SSH_WRITE_PENDING;

    }

    if (s->data_except) {

        r |= SSH_CLOSED_ERROR;

    }

    return r;

}

int ssh_socket_get_poll_flags(ssh_socket s)

{

    int r = 0;

    if (s->poll_handle != NULL && (ssh_poll_get_events (s->poll_handle) & POLLIN) > 0) {

        r |= SSH_READ_PENDING;

    }

    if (s->poll_handle != NULL && (ssh_poll_get_events (s->poll_handle) & POLLOUT) > 0) {

        r |= SSH_WRITE_PENDING;

    }

    return r;

}

#ifdef _WIN32

int ssh_socket_set_nonblocking(socket_t fd)

{

    u_long nonblocking = 1;

    return ioctlsocket(fd, FIONBIO, &nonblocking);

}

int ssh_socket_set_blocking(socket_t fd)

{

    u_long nonblocking = 0;

    return ioctlsocket(fd, FIONBIO, &nonblocking);

}

#else /* _WIN32 */

int ssh_socket_set_nonblocking(socket_t fd)

{

    return fcntl(fd, F_SETFL, O_NONBLOCK);

}

int ssh_socket_set_blocking(socket_t fd)

{

    return fcntl(fd, F_SETFL, 0);

}

#endif /* _WIN32 */

/**

 * @internal

 * @brief Launches a socket connection

 * If a the socket connected callback has been defined and

 * a poll object exists, this call will be non blocking.

 * @param s    socket to connect.

 * @param host hostname or ip address to connect to.

 * @param port port number to connect to.

 * @param bind_addr address to bind to, or NULL for default.

 * @returns SSH_OK socket is being connected.

 * @returns SSH_ERROR error while connecting to remote host.

 * @bug It only tries connecting to one of the available AI's

 * which is problematic for hosts having DNS fail-over.

 */

int ssh_socket_connect(ssh_socket s,

                       const char *host,

                       uint16_t port,

                       const char *bind_addr)

{

    socket_t fd;

    if (s->state != SSH_SOCKET_NONE) {

        ssh_set_error(s->session, SSH_FATAL,

                      "ssh_socket_connect called on socket not unconnected");

        return SSH_ERROR;

    }

    fd = ssh_connect_host_nonblocking(s->session, host, bind_addr, port);

    SSH_LOG(SSH_LOG_PROTOCOL, "Nonblocking connection socket: %d", fd);

    if (fd == SSH_INVALID_SOCKET) {

        return SSH_ERROR;

    }

    ssh_socket_set_fd(s,fd);

    return SSH_OK;

}

#ifndef _WIN32

/**

 * @internal

 * @brief executes a command and redirect input and outputs

 * @param command command to execute

 * @param in input file descriptor

 * @param out output file descriptor

 */

void

ssh_execute_command(const char *command, socket_t in, socket_t out)

{

    const char *args[] = {"/bin/sh", "-c", command, NULL};

    /* Prepare /dev/null socket for the stderr redirection */

    int devnull = open("/dev/null", O_WRONLY);

    if (devnull == -1) {

        SSH_LOG(SSH_LOG_WARNING, "Failed to open /dev/null");

        exit(1);

    }

    /* redirect in and out to stdin, stdout */