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libssh2
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libssh2/example/direct_tcpip.c

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C
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#include "libssh2_config.h"
#include <libssh2.h>
#ifdef WIN32
#include <windows.h>
#include <winsock2.h>
#include <ws2tcpip.h>
#else
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <sys/time.h>
#endif
#include <fcntl.h>
#include <errno.h>
#include <stdio.h>
#ifdef HAVE_STDLIB_H
#include <stdlib.h>
#endif
#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif
#include <sys/types.h>
#ifdef HAVE_SYS_SELECT_H
#include <sys/select.h>
#endif
#ifndef INADDR_NONE
#define INADDR_NONE (in_addr_t)-1
#endif
const char *keyfile1 = "/home/username/.ssh/id_rsa.pub";
const char *keyfile2 = "/home/username/.ssh/id_rsa";
const char *username = "username";
const char *password = "";
const char *server_ip = "127.0.0.1";
const char *local_listenip = "127.0.0.1";
unsigned int local_listenport = 2222;
const char *remote_desthost = "localhost"; /* resolved by the server */
unsigned int remote_destport = 22;
enum {
AUTH_NONE = 0,
AUTH_PASSWORD,
AUTH_PUBLICKEY
};
int main(int argc, char *argv[])
{
int rc, i, auth = AUTH_NONE;
struct sockaddr_in sin;
socklen_t sinlen;
const char *fingerprint;
char *userauthlist;
LIBSSH2_SESSION *session;
LIBSSH2_CHANNEL *channel = NULL;
const char *shost;
unsigned int sport;
fd_set fds;
struct timeval tv;
ssize_t len, wr;
char buf[16384];
#ifdef WIN32
char sockopt;
SOCKET sock = INVALID_SOCKET;
SOCKET listensock = INVALID_SOCKET, forwardsock = INVALID_SOCKET;
WSADATA wsadata;
int err;
err = WSAStartup(MAKEWORD(2, 0), &wsadata);
if(err != 0) {
fprintf(stderr, "WSAStartup failed with error: %d\n", err);
return 1;
}
#else
int sockopt, sock = -1;
int listensock = -1, forwardsock = -1;
#endif
if(argc > 1)
server_ip = argv[1];
if(argc > 2)
username = argv[2];
if(argc > 3)
password = argv[3];
if(argc > 4)
local_listenip = argv[4];
if(argc > 5)
local_listenport = atoi(argv[5]);
if(argc > 6)
remote_desthost = argv[6];
if(argc > 7)
remote_destport = atoi(argv[7]);
rc = libssh2_init(0);
if(rc) {
fprintf(stderr, "libssh2 initialization failed (%d)\n", rc);
return 1;
}
/* Connect to SSH server */
sock = socket(PF_INET, SOCK_STREAM, IPPROTO_TCP);
#ifdef WIN32
if(sock == INVALID_SOCKET) {
fprintf(stderr, "failed to open socket!\n");
return -1;
}
#else
if(sock == -1) {
perror("socket");
return -1;
}
#endif
sin.sin_family = AF_INET;
sin.sin_addr.s_addr = inet_addr(server_ip);
if(INADDR_NONE == sin.sin_addr.s_addr) {
perror("inet_addr");
return -1;
}
sin.sin_port = htons(22);
if(connect(sock, (struct sockaddr*)(&sin),
sizeof(struct sockaddr_in)) != 0) {
fprintf(stderr, "failed to connect!\n");
return -1;
}
/* Create a session instance */
session = libssh2_session_init();
if(!session) {
fprintf(stderr, "Could not initialize SSH session!\n");
return -1;
}
/* ... start it up. This will trade welcome banners, exchange keys,
* and setup crypto, compression, and MAC layers
*/
rc = libssh2_session_handshake(session, sock);
if(rc) {
fprintf(stderr, "Error when starting up SSH session: %d\n", rc);
return -1;
}
/* At this point we havn't yet authenticated. The first thing to do
* is check the hostkey's fingerprint against our known hosts Your app
* may have it hard coded, may go to a file, may present it to the
* user, that's your call
*/
fingerprint = libssh2_hostkey_hash(session, LIBSSH2_HOSTKEY_HASH_SHA1);
fprintf(stderr, "Fingerprint: ");
for(i = 0; i < 20; i++)
fprintf(stderr, "%02X ", (unsigned char)fingerprint[i]);
fprintf(stderr, "\n");
/* check what authentication methods are available */
userauthlist = libssh2_userauth_list(session, username, strlen(username));
fprintf(stderr, "Authentication methods: %s\n", userauthlist);
if(strstr(userauthlist, "password"))
auth |= AUTH_PASSWORD;
if(strstr(userauthlist, "publickey"))
auth |= AUTH_PUBLICKEY;
/* check for options */
if(argc > 8) {
if((auth & AUTH_PASSWORD) && !strcasecmp(argv[8], "-p"))
auth = AUTH_PASSWORD;
if((auth & AUTH_PUBLICKEY) && !strcasecmp(argv[8], "-k"))
auth = AUTH_PUBLICKEY;
}
if(auth & AUTH_PASSWORD) {
if(libssh2_userauth_password(session, username, password)) {
fprintf(stderr, "Authentication by password failed.\n");
goto shutdown;
}
}
else if(auth & AUTH_PUBLICKEY) {
if(libssh2_userauth_publickey_fromfile(session, username, keyfile1,
keyfile2, password)) {
fprintf(stderr, "\tAuthentication by public key failed!\n");
goto shutdown;
}
fprintf(stderr, "\tAuthentication by public key succeeded.\n");
}
else {
fprintf(stderr, "No supported authentication methods found!\n");
goto shutdown;
}
listensock = socket(PF_INET, SOCK_STREAM, IPPROTO_TCP);
#ifdef WIN32
if(listensock == INVALID_SOCKET) {
fprintf(stderr, "failed to open listen socket!\n");
return -1;
}
#else
if(listensock == -1) {
perror("socket");
return -1;
}
#endif
sin.sin_family = AF_INET;
sin.sin_port = htons(local_listenport);
sin.sin_addr.s_addr = inet_addr(local_listenip);
if(INADDR_NONE == sin.sin_addr.s_addr) {
perror("inet_addr");
goto shutdown;
}
sockopt = 1;
setsockopt(listensock, SOL_SOCKET, SO_REUSEADDR, &sockopt,
sizeof(sockopt));
sinlen = sizeof(sin);
if(-1 == bind(listensock, (struct sockaddr *)&sin, sinlen)) {
perror("bind");
goto shutdown;
}
if(-1 == listen(listensock, 2)) {
perror("listen");
goto shutdown;
}
fprintf(stderr, "Waiting for TCP connection on %s:%d...\n",
inet_ntoa(sin.sin_addr), ntohs(sin.sin_port));
forwardsock = accept(listensock, (struct sockaddr *)&sin, &sinlen);
#ifdef WIN32
if(forwardsock == INVALID_SOCKET) {
fprintf(stderr, "failed to accept forward socket!\n");
goto shutdown;
}
#else
if(forwardsock == -1) {
perror("accept");
goto shutdown;
}
#endif
shost = inet_ntoa(sin.sin_addr);
sport = ntohs(sin.sin_port);
fprintf(stderr, "Forwarding connection from %s:%d here to remote %s:%d\n",
shost, sport, remote_desthost, remote_destport);
channel = libssh2_channel_direct_tcpip_ex(session, remote_desthost,
remote_destport, shost, sport);
if(!channel) {
fprintf(stderr, "Could not open the direct-tcpip channel!\n"
"(Note that this can be a problem at the server!"
" Please review the server logs.)\n");
goto shutdown;
}
/* Must use non-blocking IO hereafter due to the current libssh2 API */
libssh2_session_set_blocking(session, 0);
while(1) {
FD_ZERO(&fds);
FD_SET(forwardsock, &fds);
tv.tv_sec = 0;
tv.tv_usec = 100000;
rc = select(forwardsock + 1, &fds, NULL, NULL, &tv);
if(-1 == rc) {
perror("select");
goto shutdown;
}
if(rc && FD_ISSET(forwardsock, &fds)) {
len = recv(forwardsock, buf, sizeof(buf), 0);
if(len < 0) {
perror("read");
goto shutdown;
}
else if(0 == len) {
fprintf(stderr, "The client at %s:%d disconnected!\n", shost,
sport);
goto shutdown;
}
wr = 0;
while(wr < len) {
i = libssh2_channel_write(channel, buf + wr, len - wr);
if(LIBSSH2_ERROR_EAGAIN == i) {
continue;
}
if(i < 0) {
fprintf(stderr, "libssh2_channel_write: %d\n", i);
goto shutdown;
}
wr += i;
}
}
while(1) {
len = libssh2_channel_read(channel, buf, sizeof(buf));
if(LIBSSH2_ERROR_EAGAIN == len)
break;
else if(len < 0) {
fprintf(stderr, "libssh2_channel_read: %d", (int)len);
goto shutdown;
}
wr = 0;
while(wr < len) {
i = send(forwardsock, buf + wr, len - wr, 0);
if(i <= 0) {
perror("write");
goto shutdown;
}
wr += i;
}
if(libssh2_channel_eof(channel)) {
fprintf(stderr, "The server at %s:%d disconnected!\n",
remote_desthost, remote_destport);
goto shutdown;
}
}
}
shutdown:
#ifdef WIN32
closesocket(forwardsock);
closesocket(listensock);
#else
close(forwardsock);
close(listensock);
#endif
if(channel)
libssh2_channel_free(channel);
libssh2_session_disconnect(session, "Client disconnecting normally");
libssh2_session_free(session);
#ifdef WIN32
closesocket(sock);
#else
close(sock);
#endif
libssh2_exit();
return 0;
}
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