libssh/src/connect.c

/*
 * connect.c - handles connections to ssh servers
 *
 * This file is part of the SSH Library
 *
 * Copyright (c) 2003-2013 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 <fcntl.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#ifdef HAVE_SYS_TIME_H
#include <sys/time.h>
#endif /* HAVE_SYS_TIME_H */

#include "libssh/libssh.h"
#include "libssh/misc.h"

#ifdef _WIN32
/*
 * Only use Windows API functions available on Windows 2000 SP4 or later.
 * The available constants are in <sdkddkver.h>.
 *  http://msdn.microsoft.com/en-us/library/aa383745.aspx
 *  http://blogs.msdn.com/oldnewthing/archive/2007/04/11/2079137.aspx
 */
#undef _WIN32_WINNT
#ifdef HAVE_WSPIAPI_H
#define _WIN32_WINNT 0x0500 /* _WIN32_WINNT_WIN2K */
#undef NTDDI_VERSION
#define NTDDI_VERSION 0x05000400 /* NTDDI_WIN2KSP4 */
#else
#define _WIN32_WINNT 0x0501 /* _WIN32_WINNT_WINXP */
#undef NTDDI_VERSION
#define NTDDI_VERSION 0x05010000 /* NTDDI_WINXP */
#endif

#if _MSC_VER >= 1400
#include <io.h>
#undef close
#define close _close
#endif /* _MSC_VER */
#include <winsock2.h>
#include <ws2tcpip.h>

/* <wspiapi.h> is necessary for getaddrinfo before Windows XP, but it isn't
 * available on some platforms like MinGW. */
#ifdef HAVE_WSPIAPI_H
#include <wspiapi.h>
#endif

#ifndef EINPROGRESS
#define EINPROGRESS WSAEINPROGRESS
#endif

#else /* _WIN32 */

#include <netdb.h>
#include <sys/socket.h>
#include <sys/select.h>
#include <netinet/in.h>
#include <netinet/tcp.h>

#endif /* _WIN32 */

#include "libssh/priv.h"
#include "libssh/socket.h"
#include "libssh/channels.h"
#include "libssh/session.h"
#include "libssh/poll.h"

#ifndef HAVE_GETADDRINFO
#error "Your system must have getaddrinfo()"
#endif

#ifdef _WIN32
#ifndef gai_strerror
char WSAAPI *gai_strerrorA(int code)
{
    static char buf[256];

    snprintf(buf, sizeof(buf), "Undetermined error code (%d)", code);

    return buf;
}
#endif /* gai_strerror */
#endif /* _WIN32 */

static int ssh_connect_socket_close(socket_t s)
{
#ifdef _WIN32
    return closesocket(s);
#else
    return close(s);
#endif
}

static int getai(const char *host, int port, struct addrinfo **ai)
{
    const char *service = NULL;
    struct addrinfo hints;
    char s_port[10];

    ZERO_STRUCT(hints);

    hints.ai_protocol = IPPROTO_TCP;
    hints.ai_family = PF_UNSPEC;
    hints.ai_socktype = SOCK_STREAM;

    if (port == 0) {
        hints.ai_flags = AI_PASSIVE;
    } else {
        snprintf(s_port, sizeof(s_port), "%hu", (unsigned short)port);
        service = s_port;
#ifdef AI_NUMERICSERV
        hints.ai_flags = AI_NUMERICSERV;
#endif
    }

    if (ssh_is_ipaddr(host)) {
        /* this is an IP address */
        SSH_LOG(SSH_LOG_PACKET, "host %s matches an IP address", host);
        hints.ai_flags |= AI_NUMERICHOST;
    }

    return getaddrinfo(host, service, &hints, ai);
}

static int set_tcp_nodelay(socket_t socket)
{
    int opt = 1;

    return setsockopt(socket,
                      IPPROTO_TCP,
                      TCP_NODELAY,
                      (void *)&opt,
                      sizeof(opt));
}

/**
 * @internal
 *
 * @brief Launches a nonblocking connect to an IPv4 or IPv6 host
 * specified by its IP address or hostname.
 *
 * @returns A file descriptor, < 0 on error.
 * @warning very ugly !!!
 */
socket_t ssh_connect_host_nonblocking(ssh_session session, const char *host,
                                      const char *bind_addr, int port)
{
    socket_t s = -1, first = -1;
    int rc;
    struct addrinfo *ai = NULL;
    struct addrinfo *itr = NULL;

    rc = getai(host, port, &ai);
    if (rc != 0) {
        ssh_set_error(session, SSH_FATAL,
                      "Failed to resolve hostname %s (%s)",
                      host, gai_strerror(rc));

        return -1;
    }

    for (itr = ai; itr != NULL; itr = itr->ai_next) {
        char err_msg[SSH_ERRNO_MSG_MAX] = {0};
        /* create socket */
        s = socket(itr->ai_family, itr->ai_socktype, itr->ai_protocol);
        if (s < 0) {
            ssh_set_error(session, SSH_FATAL,
                          "Socket create failed: %s",
                          ssh_strerror(errno, err_msg, SSH_ERRNO_MSG_MAX));
            continue;
        }

        if (bind_addr) {
            struct addrinfo *bind_ai;
            struct addrinfo *bind_itr;

            SSH_LOG(SSH_LOG_PACKET, "Resolving %s", bind_addr);

            rc = getai(bind_addr, 0, &bind_ai);
            if (rc != 0) {
                ssh_set_error(session, SSH_FATAL,
                              "Failed to resolve bind address %s (%s)",
                              bind_addr,
                              gai_strerror(rc));
                ssh_connect_socket_close(s);
                s = -1;
                break;
            }

            for (bind_itr = bind_ai;
                 bind_itr != NULL;
                 bind_itr = bind_itr->ai_next)
            {
                if (bind(s, bind_itr->ai_addr, bind_itr->ai_addrlen) < 0) {
                    ssh_set_error(session, SSH_FATAL,
                                  "Binding local address: %s",
                                  ssh_strerror(errno, err_msg, SSH_ERRNO_MSG_MAX));
                    continue;
                } else {
                    break;
                }
            }
            freeaddrinfo(bind_ai);

            /* Cannot bind to any local addresses */
            if (bind_itr == NULL) {
                ssh_connect_socket_close(s);
                s = -1;
                continue;
            }
        }

        rc = ssh_socket_set_nonblocking(s);
        if (rc < 0) {
            ssh_set_error(session, SSH_FATAL,
                          "Failed to set socket non-blocking for %s:%d",
                          host, port);
            ssh_connect_socket_close(s);
            s = -1;
            continue;
        }

        if (session->opts.nodelay) {
            /* For winsock, socket options are only effective before connect */
            rc = set_tcp_nodelay(s);
            if (rc < 0) {
                ssh_set_error(session, SSH_FATAL,
                              "Failed to set TCP_NODELAY on socket: %s",
                              ssh_strerror(errno, err_msg, SSH_ERRNO_MSG_MAX));
                ssh_connect_socket_close(s);
                s = -1;
                continue;
            }
        }

        errno = 0;
        rc = connect(s, itr->ai_addr, itr->ai_addrlen);
        if (rc == -1) {
            if ((errno != 0) && (errno != EINPROGRESS)) {
                ssh_set_error(session, SSH_FATAL,
                              "Failed to connect: %s",
                              ssh_strerror(errno, err_msg, SSH_ERRNO_MSG_MAX));
                ssh_connect_socket_close(s);
                s = -1;
            } else {
                if (first == -1) {
                    first = s;
                } else { /* errno == EINPROGRESS */
                    /* save only the first "working" socket */
                    ssh_connect_socket_close(s);
                    s = -1;
                }
            }
            continue;
        }

        break;
    }

    freeaddrinfo(ai);

    /* first let's go through all the addresses looking for immediate
     * connection, otherwise return the first address without error or error */
    if (s == -1) {
        s = first;
    }

    return s;
}

/**
 * @addtogroup libssh_session
 *
 * @{
 */

static int ssh_select_cb (socket_t fd, int revents, void *userdata)
{
    fd_set *set = (fd_set *)userdata;
    if (revents & POLLIN) {
        FD_SET(fd, set);
    }
    return 0;
}

/**
 * @brief A wrapper for the select syscall
 *
 * This function acts more or less like the select(2) syscall.\n
 * There is no support for writing or exceptions.\n
 *
 * @param[in]  channels Arrays of channels pointers terminated by a NULL.
 *                      It is never rewritten.
 *
 * @param[out] outchannels Arrays of the same size as "channels", there is no
 *                         need to initialize it.
 *
 * @param[in]  maxfd    Maximum +1 file descriptor from readfds.
 *
 * @param[in]  readfds  A fd_set of file descriptors to be select'ed for
 *                      reading.
 *
 * @param[in]  timeout  The timeout in milliseconds.
 *
 * @return              SSH_OK on success,
 *                      SSH_ERROR on error,
 *                      SSH_EINTR if it was interrupted. In that case,
 *                      just restart it.
 *
 * @warning libssh is not reentrant here. That means that if a signal is caught
 *          during the processing of this function, you cannot call libssh
 *          functions on sessions that are busy with ssh_select().
 *
 * @see select(2)
 */
int ssh_select(ssh_channel *channels, ssh_channel *outchannels, socket_t maxfd,
               fd_set *readfds, struct timeval *timeout)
{
    fd_set origfds;
    socket_t fd;
    size_t i, j;
    int rc;
    int base_tm, tm;
    struct ssh_timestamp ts;
    ssh_event event = ssh_event_new();
    int firstround = 1;

    base_tm = tm = (timeout->tv_sec * 1000) + (timeout->tv_usec / 1000);
    for (i = 0 ; channels[i] != NULL; ++i) {
        ssh_event_add_session(event, channels[i]->session);
    }

    ZERO_STRUCT(origfds);
    FD_ZERO(&origfds);
    for (fd = 0; fd < maxfd ; fd++) {
        if (FD_ISSET(fd, readfds)) {
            ssh_event_add_fd(event, fd, POLLIN, ssh_select_cb, readfds);
            FD_SET(fd, &origfds);
        }
    }
    outchannels[0] = NULL;
    FD_ZERO(readfds);
    ssh_timestamp_init(&ts);
    do {
        /* Poll every channel */
        j = 0;
        for (i = 0; channels[i]; i++) {
            rc = ssh_channel_poll(channels[i], 0);
            if (rc != 0) {
                outchannels[j] = channels[i];
                j++;
            } else {
                rc = ssh_channel_poll(channels[i], 1);
                if (rc != 0) {
                    outchannels[j] = channels[i];
                    j++;
                }
            }
        }

        outchannels[j] = NULL;
        if (j != 0) {
            break;
        }

        /* watch if a user socket was triggered */
        for (fd = 0; fd < maxfd; fd++) {
            if (FD_ISSET(fd, readfds)) {
                goto out;
            }
        }

        /* If the timeout is elapsed, we should go out */
        if (!firstround && ssh_timeout_elapsed(&ts, base_tm)) {
            goto out;
        }

        /* since there's nothing, let's fire the polling */
        rc = ssh_event_dopoll(event,tm);
        if (rc == SSH_ERROR) {
            goto out;
        }

        tm = ssh_timeout_update(&ts, base_tm);
        firstround = 0;
    } while (1);
out:
    for (fd = 0; fd < maxfd; fd++) {
        if (FD_ISSET(fd, &origfds)) {
            ssh_event_remove_fd(event, fd);
        }
    }
    ssh_event_free(event);
    return SSH_OK;
}

/** @} */