libssh/libssh/socket.c

/* socket.c */
/* the Socket class */
/*
 * Copyright (c) 2008 Aris Adamantiadis
 *
 * This file is part of the SSH Library
 *
 * 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 <unistd.h>
#include <errno.h>
#include <string.h>
#include <stdlib.h>
#include <stdio.h>
#ifdef _WIN32
#include <winsock2.h>
#else
#include <fcntl.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/un.h>
#endif
#include "libssh/priv.h"

#if !defined(HAVE_SELECT) && !defined(HAVE_POLL)
#error Your system must have either select() or poll()
#endif

#if !defined(HAVE_POLL) && !defined(_WIN32)
#warning your system does not have poll. Select has known limitations
#define SELECT_LIMIT_CHECK
#endif

#ifdef HAVE_POLL
#define USE_POLL
#include <poll.h>
#else
#define USE_SELECT
#endif

/** \defgroup ssh_socket Sockets
 * \addtogroup ssh_socket
 * @{
 */

struct socket {
	socket_t fd;
	int last_errno;
    int data_to_read; /* reading now on socket will
                         not block */
    int data_to_write;
    int data_except;
    BUFFER *out_buffer;
    BUFFER *in_buffer;
    SSH_SESSION *session;
};

/*
 * \internal
 * \brief inits the socket system (windows specific)
 */
void ssh_socket_init(void) {
#ifdef _WIN32
  struct WSAData wsaData;

  if (WSAStartup(MAKEWORD(2, 0), &wsaData)) {
    /* FIXME print error */
  }
#endif
}
/*
 * \internal
 * \brief creates a new Socket object
 */
struct socket *ssh_socket_new(SSH_SESSION *session){
	struct socket *s=malloc(sizeof(struct socket));
	s->fd=-1;
	s->last_errno=-1;
	s->session=session;
	s->in_buffer=buffer_new();
	s->out_buffer=buffer_new();
	s->data_to_read=0;
	s->data_to_write=0;
	s->data_except=0;
	return s;
}

/* \internal
 * \brief Deletes a socket object
 */
void ssh_socket_free(struct socket *s){
    ssh_socket_close(s);
    buffer_free(s->in_buffer);
    buffer_free(s->out_buffer);
	free(s);
}

#ifndef _WIN32
int ssh_socket_unix(struct socket *s, const char *path) {
  struct sockaddr_un sunaddr;

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

  s->fd = socket(AF_UNIX, SOCK_STREAM, 0);
  if (s->fd < 0) {
    return -1;
  }

  if (fcntl(s->fd, F_SETFD, 1) == -1) {
    close(s->fd);
    s->fd = -1;
    return -1;
  }

  if (connect(s->fd, (struct sockaddr *) &sunaddr,
        sizeof(sunaddr)) < 0) {
    close(s->fd);
    s->fd = -1;
    return -1;
  }

  return 0;
}
#endif

/* \internal
 * \brief closes a socket
 */
void ssh_socket_close(struct socket *s){
	if(ssh_socket_is_open(s)){
#ifdef _WIN32
		closesocket(s->fd);
		s->last_errno=WSAGetLastError();
#else
		close(s->fd);
		s->last_errno=errno;
#endif
		s->fd=-1;
	}
}

/* \internal
 * \brief sets the file descriptor of the socket
 */
void ssh_socket_set_fd(struct socket *s, socket_t fd){
	s->fd=fd;
}

/* \internal
 * \brief returns the file descriptor of the socket
 */
socket_t ssh_socket_get_fd(struct socket *s){
	return s->fd;
}

/* \internal
 * \brief returns nonzero if the socket is open
 */
int ssh_socket_is_open(struct socket *s){
	return s->fd != -1;
}

/* \internal
 * \brief read len bytes from socket into buffer
 */
static int ssh_socket_unbuffered_read(struct socket *s, void *buffer, u32 len) {
	int r;
	if(s->data_except)
		return -1;
	r=recv(s->fd,buffer,len,0);
#ifndef _WIN32
    s->last_errno=errno;
#else
    s->last_errno=WSAGetLastError();
#endif
    s->data_to_read=0;
    if(r<0)
    	s->data_except=1;
	return r;
}

/* \internal
 * \brief writes len bytes from buffer to socket
 */
static int ssh_socket_unbuffered_write(struct socket *s,const void *buffer,
    u32 len) {
	int w;
	if(s->data_except)
		return -1;
	w=send(s->fd,buffer,len,0);
#ifndef _WIN32
    s->last_errno=errno;
#else
    s->last_errno=WSAGetLastError();
#endif
    s->data_to_write=0;
    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(struct socket *s, fd_set *set){
	if(s->fd==-1)
		return 0;
	return FD_ISSET(s->fd,set);
}

/* \internal
 * \brief sets the current fd in a fd_set and updates the fd_max
 */

void ssh_socket_fd_set(struct socket *s, fd_set *set, int *fd_max){
	if(s->fd==-1)
		return;
	FD_SET(s->fd,set);
	if(s->fd>= *fd_max){
		*fd_max=s->fd+1;
	}
}

/** \internal
 * \brief reads blocking until len bytes have been read
 */
int ssh_socket_completeread(struct socket *s, void *buffer, u32 len){
    int r;
    u32 total=0;
    u32 toread=len;
    if(!ssh_socket_is_open(s))
        return SSH_ERROR;
    while((r=ssh_socket_unbuffered_read(s,buffer+total,toread))){
        if(r==-1)
            return SSH_ERROR;
        total += r;
        toread-=r;
        if(total==len)
            return len;
        if(r==0)
            return 0;
    }
    return total ; /* connection closed */
}

/** \internal
 * \brief Blocking write of len bytes
 */

int ssh_socket_completewrite(struct socket *s, void *buffer, u32 len){
    SSH_SESSION *session=s->session;
    int written;

    enter_function();
    if(!ssh_socket_is_open(s)){
        leave_function();
    	return SSH_ERROR;
    }
    while(len >0) {
        written=ssh_socket_unbuffered_write(s,buffer,len);
        if(written==0 || written==-1){
        	leave_function();
            return SSH_ERROR;
        }
        len-=written;
        buffer+=written;
    }
    leave_function();
    return SSH_OK;
}

/** \internal
 * \brief buffered read of data (complete)
 * \returns SSH_OK or SSH_ERROR.
 * \returns SSH_AGAIN in nonblocking mode
 */
int ssh_socket_read(struct socket *s, void *buffer, int len){
	SSH_SESSION *session=s->session;
	int ret;

	enter_function();
	ret = ssh_socket_wait_for_data(s, s->session, len);
	if(ret != SSH_OK){
		leave_function();
		return ret;
	}
	memcpy(buffer,buffer_get_rest(s->in_buffer),len);
	buffer_pass_bytes(s->in_buffer,len);
	leave_function();
	return SSH_OK;
}

#define WRITE_BUFFERING_THRESHOLD 65536
/** \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(struct socket *s,const void *buffer, int len){
	SSH_SESSION *session=s->session;
	int ret;

	enter_function();
	buffer_add_data(s->out_buffer,buffer,len);
	if(buffer_get_rest_len(s->out_buffer) > WRITE_BUFFERING_THRESHOLD)
		ret=ssh_socket_nonblocking_flush(s);
	else
		ret=len;
	leave_function();
	return ret;
}


/** \internal
 * \brief wait for data on socket
 * \param s socket
 * \param session the ssh session
 * \param len number of bytes to be read
 * \returns SSH_OK bytes are available on socket
 * \returns SSH_AGAIN need to call later for data
 * \returns SSH_ERROR error happened
 */
int ssh_socket_wait_for_data(struct socket *s, SSH_SESSION *session, u32 len){
    int except, can_write;
    int to_read;
    int r;
    char *buf;
    char buffer[4096];
    enter_function();
    to_read=len - buffer_get_rest_len(s->in_buffer);
    if(to_read <= 0){
    	leave_function();
        return SSH_OK;
    }
    if(session->blocking){
        buf=malloc(to_read);
        r=ssh_socket_completeread(session->socket,buf,to_read);
        if(r==SSH_ERROR || r ==0){
            ssh_set_error(session,SSH_FATAL,
                (r==0)?"Connection closed by remote host" : "Error reading socket");
            ssh_socket_close(session->socket);
            session->alive=0;
            free(buf);
            leave_function();
            return SSH_ERROR;
        }

        buffer_add_data(s->in_buffer,buf,to_read);
        free(buf);
        leave_function();
        return SSH_OK;
    }
    /* nonblocking read */
    do {
        ssh_socket_poll(s,&can_write,&except); /* internally sets data_to_read */
        if(!s->data_to_read){
            leave_function();
        	return SSH_AGAIN;
        }

        /* read as much as we can */
        if(ssh_socket_is_open(session->socket))
            r=ssh_socket_unbuffered_read(session->socket,buffer,sizeof(buffer));
        else
            r=-1;
        if(r<=0){
            ssh_set_error(session,SSH_FATAL,
                (r==0)?"Connection closed by remote host" : "Error reading socket");
            ssh_socket_close(session->socket);
            session->alive=0;
            leave_function();
            return SSH_ERROR;
        }
        buffer_add_data(s->in_buffer,buffer, (u32) r);
    } while(buffer_get_rest_len(s->in_buffer)<len);
    leave_function();
    return SSH_OK;
}

#ifdef USE_SELECT
/* ssh_socket_poll, select() version */

/* \internal
 * \brief polls the socket for data
 * \param session ssh session
 * \param write value pointed to set to 1 if it is possible to write
 * \param except value pointed to set to 1 if there is an exception
 * \return 1 if it is possible to read, 0 otherwise, -1 on error
 */
int ssh_socket_poll(struct socket *s, int *write, int *except){
	SSH_SESSION *session=s->session;
    struct timeval sometime;
    fd_set rdes; // read set
    fd_set wdes; // writing set
    fd_set edes; // exception set
    int fdmax=-1;

    enter_function();
    FD_ZERO(&rdes);
    FD_ZERO(&wdes);
    FD_ZERO(&edes);

    if(!ssh_socket_is_open(s)){
        *except=1;
        *write=0;
        return 0;
    }
#ifdef SELECT_LIMIT_CHECK
    // some systems don't handle the fds > FD_SETSIZE
    if(s->fd > FD_SETSIZE){
    	ssh_set_error(session, SSH_REQUEST_DENIED, "File descriptor out of range for select : %d",s->fd);
    	leave_function();
    	return -1;
    }
#endif
    if(!s->data_to_read)
        ssh_socket_fd_set(s,&rdes,&fdmax);
    if(!s->data_to_write)
        ssh_socket_fd_set(s,&wdes,&fdmax);
    ssh_socket_fd_set(s,&edes,&fdmax);

    /* Set to return immediately (no blocking) */
    sometime.tv_sec = 0;
    sometime.tv_usec = 0;

    /* Make the call, and listen for errors */
    if (select(fdmax, &rdes,&wdes,&edes, &sometime) < 0) {
    	ssh_set_error(session,SSH_FATAL, "select: %s", strerror(errno));
    	leave_function();
    	return -1;
    }
    if(!s->data_to_read)
        s->data_to_read=ssh_socket_fd_isset(s,&rdes);
    if(!s->data_to_write)
        s->data_to_write=ssh_socket_fd_isset(s,&wdes);
    if(!s->data_except)
    	s->data_except=ssh_socket_fd_isset(s,&edes);
    *except=s->data_except;
    *write=s->data_to_write;
    leave_function();
    return s->data_to_read || (buffer_get_rest_len(s->in_buffer)>0);
}
#endif

#ifdef USE_POLL
/* ssh_socket_poll, poll() version */
int ssh_socket_poll(struct socket *s, int *write, int *except){
	SSH_SESSION *session=s->session;
	struct pollfd fd[1];
	int err;

	enter_function();
    if(!ssh_socket_is_open(s)){
        *except=1;
        *write=0;
        return 0;
    }
    fd->fd=s->fd;
    fd->events=0;
    if(!s->data_to_read)
        fd->events |= POLLIN;
    if(!s->data_to_write)
        fd->events |= POLLOUT;

    /* Make the call, and listen for errors */
    err=poll(fd,1,0);
    if(err<0){
    	ssh_set_error(session,SSH_FATAL, "select: %s", strerror(errno));
    	leave_function();
    	return -1;
    }
    if(!s->data_to_read)
        s->data_to_read=fd->revents & POLLIN;
    if(!s->data_to_write)
        s->data_to_write=fd->revents & POLLOUT;
    if(!s->data_except)
    	s->data_except=fd->revents & POLLERR;
    *except=s->data_except;
    *write=s->data_to_write;
    leave_function();
    return s->data_to_read || (buffer_get_rest_len(s->in_buffer)>0);
}
#endif

/** \internal
 * \brief nonblocking flush of the output buffer
 */
int ssh_socket_nonblocking_flush(struct socket *s){
    int except, can_write;
    int w;
    SSH_SESSION *session=s->session;
    enter_function();
    ssh_socket_poll(s,&can_write,&except); /* internally sets data_to_write */
    if(!ssh_socket_is_open(s)){
        session->alive=0;
        // FIXME use ssh_socket_get_errno
        ssh_set_error(session,SSH_FATAL,"Writing packet : error on socket (or connection closed): %s",strerror(errno));
        leave_function();
        return SSH_ERROR;
    }
    while(s->data_to_write && buffer_get_rest_len(s->out_buffer)>0){
        if(ssh_socket_is_open(s)){
            w=ssh_socket_unbuffered_write(s,buffer_get_rest(s->out_buffer),
                buffer_get_rest_len(s->out_buffer));
        } else
            w=-1; /* write failed */
        if(w<0){
            session->alive=0;
            ssh_socket_close(s);
            // FIXME use ssh_socket_get_errno()
            ssh_set_error(session,SSH_FATAL,"Writing packet : error on socket (or connection closed): %s",
                          strerror(errno));
            leave_function();
            return SSH_ERROR;
        }
        buffer_pass_bytes(s->out_buffer,w);
        /* refresh the socket status */
        ssh_socket_poll(session->socket,&can_write,&except);
    }
    if(buffer_get_rest_len(s->out_buffer)>0){
        leave_function();
    	return SSH_AGAIN;  /* there is data pending */
    }
    leave_function();
    return SSH_OK; // all data written
}


/** \internal
 * \brief locking flush of the output packet buffer
 */
int ssh_socket_blocking_flush(struct socket *s){
	SSH_SESSION *session=s->session;
	enter_function();
    if(!ssh_socket_is_open(s)) {
        session->alive=0;
        leave_function();
        return SSH_ERROR;
    }
    if(s->data_except){
        leave_function();
    	return SSH_ERROR;
    }
    if(buffer_get_rest_len(s->out_buffer)==0){
    	leave_function();
        return SSH_OK;
    }
    if(ssh_socket_completewrite(s,buffer_get_rest(s->out_buffer),
       buffer_get_rest_len(s->out_buffer))){
        session->alive=0;
        ssh_socket_close(s);
        // FIXME use the proper errno
        ssh_set_error(session,SSH_FATAL,"Writing packet : error on socket (or connection closed): %s",
                         strerror(errno));
        leave_function();
        return SSH_ERROR;
    }
    buffer_reinit(s->out_buffer);
    leave_function();
    return SSH_OK; // no data pending
}

void ssh_socket_set_towrite(struct socket *s){
	s->data_to_write=1;
}

void ssh_socket_set_toread(struct socket *s){
	s->data_to_read=1;
}

void ssh_socket_set_except(struct socket *s){
	s->data_except=1;
}

int ssh_socket_data_available(struct socket *s){
	return s->data_to_read;
}

int ssh_socket_data_writable(struct socket *s){
	return s->data_to_write;
}

int ssh_socket_get_status(struct socket *s){
	int r=0;
	if(s->data_to_read)
		r |= SSH_READ_PENDING;
	if(s->data_except)
		r|= SSH_CLOSED_ERROR;
	return r;
}

/** @}
 */