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31ec5a8b55cc90efb0bd1bb2be621e416f1444ef
libssh2/example/tcpip-forward.c
Viktor Szakats 854cfa8292 build: prepare builds for clang-cl, add cmake ossfuzz support 
- cmake: add support to build ossfuzz.
  Enable with `-DBUILD_OSSFUZZ=ON`.
  Also supports `-DLIB_FUZZING_ENGINE=` like autotools does.
- check for `__clang__` when suppressing warnings in source. Necessary
  for clang-cl, which set `__clang__`, but doesn't set `__GNU__`.
- cmake: optimize out 4 picky warning option detections with gcc.
- cmake: bring `-pedantic-error`, `-Wall` use closer to curl's.
- cmake: set `-Wno-language-extension-token` for clang-cl.
- cmake: escape only the necessary `-W` options for clang-cl.
- cmake: apply picky warnings to C++.
- cmake: replace `unset(VAR)` with `set(VAR "")` for init.
- cmake: prefer dash-style MSVC options.
- cmake: simplify `MATCHES` expression.
- cmake: formatting/whitespace.
- ci/GHA: bump `actions/upload-artifact` to v4

Closes #1524
2025-01-30 22:01:49 +01:00

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/* Copyright (C) The libssh2 project and its contributors.
*
* SPDX-License-Identifier: BSD-3-Clause
*/
#include "libssh2_setup.h"
#include <libssh2.h>
#ifdef _WIN32
#include <ws2tcpip.h> /* for socklen_t */
#define recv(s, b, l, f) recv((s), (b), (int)(l), (f))
#define send(s, b, l, f) send((s), (b), (int)(l), (f))
#endif
#ifdef HAVE_SYS_SOCKET_H
#include <sys/socket.h>
#endif
#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif
#ifdef HAVE_NETINET_IN_H
#include <netinet/in.h>
#endif
#ifdef HAVE_ARPA_INET_H
#include <arpa/inet.h>
#endif
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#ifndef INADDR_NONE
#define INADDR_NONE (in_addr_t)~0
#endif
static const char *pubkey = "/home/username/.ssh/id_rsa.pub";
static const char *privkey = "/home/username/.ssh/id_rsa";
static const char *username = "username";
static const char *password = "";
static const char *server_ip = "127.0.0.1";
/* resolved by the server */
static const char *remote_listenhost = "localhost";
static int remote_wantport = 2222;
static int remote_listenport;
static const char *local_destip = "127.0.0.1";
static int local_destport = 22;
enum {
AUTH_NONE = 0,
AUTH_PASSWORD = 1,
AUTH_PUBLICKEY = 2
};
int main(int argc, char *argv[])
{
int i, auth = AUTH_NONE;
struct sockaddr_in sin;
socklen_t sinlen = sizeof(sin);
const char *fingerprint;
char *userauthlist;
int rc;
LIBSSH2_SESSION *session = NULL;
LIBSSH2_LISTENER *listener = NULL;
LIBSSH2_CHANNEL *channel = NULL;
struct timeval tv;
ssize_t len, wr;
char buf[16384];
libssh2_socket_t sock;
libssh2_socket_t forwardsock = LIBSSH2_INVALID_SOCKET;
#ifdef _WIN32
WSADATA wsadata;
rc = WSAStartup(MAKEWORD(2, 0), &wsadata);
if(rc) {
fprintf(stderr, "WSAStartup failed with error: %d\n", rc);
return 1;
}
#endif
if(argc > 1)
server_ip = argv[1];
if(argc > 2)
username = argv[2];
if(argc > 3)
password = argv[3];
if(argc > 4)
remote_listenhost = argv[4];
if(argc > 5)
remote_wantport = atoi(argv[5]);
if(argc > 6)
local_destip = argv[6];
if(argc > 7)
local_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);
if(sock == LIBSSH2_INVALID_SOCKET) {
fprintf(stderr, "failed to open socket.\n");
goto shutdown;
}
sin.sin_family = AF_INET;
sin.sin_addr.s_addr = inet_addr(server_ip);
if(INADDR_NONE == sin.sin_addr.s_addr) {
fprintf(stderr, "inet_addr: Invalid IP address '%s'\n", server_ip);
goto shutdown;
}
sin.sin_port = htons(22);
if(connect(sock, (struct sockaddr*)(&sin), sizeof(struct sockaddr_in))) {
fprintf(stderr, "Failed to connect to %s.\n", inet_ntoa(sin.sin_addr));
goto shutdown;
}
/* Create a session instance */
session = libssh2_session_init();
if(!session) {
fprintf(stderr, "Could not initialize SSH session.\n");
goto shutdown;
}
/* ... 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);
goto shutdown;
}
/* At this point we have not 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,
(unsigned int)strlen(username));
if(userauthlist) {
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) && !strcmp(argv[8], "-p"))
auth = AUTH_PASSWORD;
if((auth & AUTH_PUBLICKEY) && !strcmp(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,
pubkey, privkey,
password)) {
fprintf(stderr, "Authentication by public key failed.\n");
goto shutdown;
}
else {
fprintf(stderr, "Authentication by public key succeeded.\n");
}
}
else {
fprintf(stderr, "No supported authentication methods found.\n");
goto shutdown;
}
}
fprintf(stderr, "Asking server to listen on remote %s:%d\n",
remote_listenhost, remote_wantport);
listener = libssh2_channel_forward_listen_ex(session, remote_listenhost,
remote_wantport,
&remote_listenport, 1);
if(!listener) {
fprintf(stderr, "Could not start the tcpip-forward listener.\n"
"(Note that this can be a problem at the server."
" Please review the server logs.)\n");
goto shutdown;
}
fprintf(stderr, "Server is listening on %s:%d\n", remote_listenhost,
remote_listenport);
fprintf(stderr, "Waiting for remote connection\n");
channel = libssh2_channel_forward_accept(listener);
if(!channel) {
fprintf(stderr, "Could not accept connection.\n"
"(Note that this can be a problem at the server."
" Please review the server logs.)\n");
goto shutdown;
}
fprintf(stderr,
"Accepted remote connection. Connecting to local server %s:%d\n",
local_destip, local_destport);
forwardsock = socket(PF_INET, SOCK_STREAM, IPPROTO_TCP);
if(forwardsock == LIBSSH2_INVALID_SOCKET) {
fprintf(stderr, "failed to open forward socket.\n");
goto shutdown;
}
sin.sin_family = AF_INET;
sin.sin_port = htons((unsigned short)local_destport);
sin.sin_addr.s_addr = inet_addr(local_destip);
if(INADDR_NONE == sin.sin_addr.s_addr) {
fprintf(stderr, "failed in inet_addr().\n");
goto shutdown;
}
if(-1 == connect(forwardsock, (struct sockaddr *)&sin, sinlen)) {
fprintf(stderr, "failed to connect().\n");
goto shutdown;
}
fprintf(stderr, "Forwarding connection from remote %s:%d to local %s:%d\n",
remote_listenhost, remote_listenport,
local_destip, local_destport);
/* Must use non-blocking IO hereafter due to the current libssh2 API */
libssh2_session_set_blocking(session, 0);
for(;;) {
fd_set fds;
FD_ZERO(&fds);
#if defined(__GNUC__) || defined(__clang__)
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wsign-conversion"
#endif
FD_SET(forwardsock, &fds);
#if defined(__GNUC__) || defined(__clang__)
#pragma GCC diagnostic pop
#endif
tv.tv_sec = 0;
tv.tv_usec = 100000;
rc = select((int)(forwardsock + 1), &fds, NULL, NULL, &tv);
if(-1 == rc) {
fprintf(stderr, "failed to select().\n");
goto shutdown;
}
#if defined(__GNUC__) || defined(__clang__)
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wsign-conversion"
#endif
if(rc && FD_ISSET(forwardsock, &fds)) {
#if defined(__GNUC__) || defined(__clang__)
#pragma GCC diagnostic pop
#endif
ssize_t nwritten;
len = recv(forwardsock, buf, sizeof(buf), 0);
if(len < 0) {
fprintf(stderr, "failed to recv().\n");
goto shutdown;
}
else if(len == 0) {
fprintf(stderr, "The local server at %s:%d disconnected.\n",
local_destip, local_destport);
goto shutdown;
}
wr = 0;
do {
nwritten = libssh2_channel_write(channel, buf, (size_t)len);
if(nwritten < 0) {
fprintf(stderr, "libssh2_channel_write: %ld\n",
(long)nwritten);
goto shutdown;
}
wr += nwritten;
} while(nwritten > 0 && wr < len);
}
for(;;) {
ssize_t nsent;
len = libssh2_channel_read(channel, buf, sizeof(buf));
if(LIBSSH2_ERROR_EAGAIN == len)
break;
else if(len < 0) {
fprintf(stderr, "libssh2_channel_read: %ld",
(long)len);
goto shutdown;
}
wr = 0;
while(wr < len) {
nsent = send(forwardsock, buf + wr, (size_t)(len - wr), 0);
if(nsent <= 0) {
fprintf(stderr, "failed to send().\n");
goto shutdown;
}
wr += nsent;
}
if(libssh2_channel_eof(channel)) {
fprintf(stderr, "The remote client at %s:%d disconnected.\n",
remote_listenhost, remote_listenport);
goto shutdown;
}
}
}
shutdown:
if(forwardsock != LIBSSH2_INVALID_SOCKET) {
shutdown(forwardsock, 2);
LIBSSH2_SOCKET_CLOSE(forwardsock);
}
if(channel)
libssh2_channel_free(channel);
if(listener)
libssh2_channel_forward_cancel(listener);
if(session) {
libssh2_session_disconnect(session, "Normal Shutdown");
libssh2_session_free(session);
}
if(sock != LIBSSH2_INVALID_SOCKET) {
shutdown(sock, 2);
LIBSSH2_SOCKET_CLOSE(sock);
}
libssh2_exit();
#ifdef _WIN32
WSACleanup();
#endif
return 0;
}
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