libssh2-tunnel/reverse-tunnel.c

#include "reverse-tunnel.h"
#include <pthread.h>
#include <libssh2.h>
#include <netinet/in.h>
#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>

const char *keyfile1 = "/home/aixiao/.ssh/id_rsa.pub";
const char *keyfile2 = "/home/aixiao/.ssh/id_rsa";
const char *username = "aixiao";
const char *password = "12345";

const char *server_ip = "127.0.0.1";

const char *remote_listenhost = "0.0.0.0"; /* 由远程服务器解析 */
int remote_wantport = 33;
int remote_listenport;

const char *local_destip = "0.0.0.0";
int local_destport = 22;

struct tunnel_args {
    LIBSSH2_CHANNEL *channel;
    LIBSSH2_SESSION *session;
};

enum {
    AUTH_NONE = 0,
    AUTH_PASSWORD,
    AUTH_PUBLICKEY
};

int forward_tunnel(LIBSSH2_SESSION *session, LIBSSH2_CHANNEL *channel)
{
    int i, rc = 0;
    struct sockaddr_in sin;
    fd_set fds;
    struct timeval tv;
    ssize_t len, wr;
    char buf[16384];
    int forwardsock = -1;

    fprintf(stdout, "接受到远程连接。连接到本地服务器 %s:%d\n", local_destip, local_destport);
    forwardsock = socket(PF_INET, SOCK_STREAM, IPPROTO_TCP);
    if (forwardsock == -1) {
        fprintf(stderr, "打开socket错误\n");
        goto shutdown;
    }

    sin.sin_family = AF_INET;
    sin.sin_port = htons(local_destport);
    if (INADDR_NONE == (sin.sin_addr.s_addr = inet_addr(local_destip))) {
        fprintf(stderr, "无效的本地IP地址\n");
        goto shutdown;
    }

    if (-1 == connect(forwardsock, (struct sockaddr *)&sin, sizeof(struct sockaddr_in))) {
        fprintf(stderr, "连接失败！\n");
        goto shutdown;
    }

    fprintf(stdout, "将连接从远程 %s:%d 转发到本地 %s:%d\n", remote_listenhost, remote_listenport, local_destip, local_destport);

    /* 设置会话为非阻塞IO */
    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) {
            fprintf(stderr, "socket未准备好！\n");
            goto shutdown;
        }
        if (rc && FD_ISSET(forwardsock, &fds)) {
            len = recv(forwardsock, buf, sizeof(buf), 0);
            if (len < 0) {
                fprintf(stderr, "从forwardsock读取时出错！\n");
                goto shutdown;
            } else if (0 == len) {
                fprintf(stderr, "本地服务器 %s:%d 断开连接！\n", local_destip, local_destport);
                goto shutdown;
            }
            wr = 0;
            do {
                i = libssh2_channel_write(channel, buf, len);
                if (i < 0) {
                    fprintf(stderr, "在SSH通道上写入时出错: %d\n", i);
                    goto shutdown;
                }
                wr += i;
            } while (i > 0 && wr < len);
        }
        while (1) {
            len = libssh2_channel_read(channel, buf, sizeof(buf));
            if (LIBSSH2_ERROR_EAGAIN == len)
                break;
            else if (len < 0) {
                fprintf(stderr, "从SSH通道读取时出错: %d\n", (int)len);
                goto shutdown;
            }
            wr = 0;
            while (wr < len) {
                i = send(forwardsock, buf + wr, len - wr, 0);
                if (i <= 0) {
                    fprintf(stderr, "在forwardsock上写入时出错！\n");
                    goto shutdown;
                }
                wr += i;
            }
            if (libssh2_channel_eof(channel)) {
                fprintf(stderr, "远程客户端 %s:%d 断开连接！\n", remote_listenhost, remote_listenport);
                goto shutdown;
            }
        }
    }

shutdown:
    close(forwardsock);
    /* 将会话设置回阻塞IO */
    libssh2_session_set_blocking(session, 1);
    return rc;
}

void *handle_tunnel(void *arg)
{
    LIBSSH2_CHANNEL *channel = ((struct tunnel_args *)arg)->channel;
    LIBSSH2_SESSION *session = ((struct tunnel_args *)arg)->session;
    forward_tunnel(session, channel);
    libssh2_channel_free(channel);
    free(arg); // 释放为参数分配的内存
    return NULL;
}

int main(int argc, char *argv[])
{
    int rc, i, auth = AUTH_NONE;
    struct sockaddr_in sin;
    const char *fingerprint;
    char *userauthlist;
    LIBSSH2_SESSION *session;
    LIBSSH2_LISTENER *listener = NULL;
    LIBSSH2_CHANNEL *channel = NULL;

    int sock = -1;

    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 != 0) {
        fprintf(stderr, "libssh2初始化失败 (%d)\n", rc);
        return 1;
    }

    /* 连接到SSH服务器 */
    sock = socket(PF_INET, SOCK_STREAM, IPPROTO_TCP);
    if (sock == -1) {
        fprintf(stderr, "打开socket错误\n");
        return -1;
    }

    sin.sin_family = AF_INET;
    if (INADDR_NONE == (sin.sin_addr.s_addr = inet_addr(server_ip))) {
        fprintf(stderr, "无效的远程IP地址\n");
        return -1;
    }

    int optval = 1;
    if (setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, &optval, sizeof(optval)) < 0)
    {
        perror("setsockopt");
        exit(1);
    }

    sin.sin_port = htons(22);   /* SSH端口 */
    if (connect(sock, (struct sockaddr *)(&sin), sizeof(struct sockaddr_in)) != 0) {
        fprintf(stderr, "连接失败！\n");
        return -1;
    }

    /* 创建会话实例 */
    session = libssh2_session_init();
    if (!session) {
        fprintf(stderr, "无法初始化SSH会话！\n");
        return -1;
    }

    /* 启动会话。这将交换欢迎消息，交换密钥，并设置加密、压缩和MAC层 */

    rc = libssh2_session_handshake(session, sock);
    if (rc) {
        fprintf(stderr, "启动SSH会话时出错: %d\n", rc);
        return -1;
    }

    /* 此时我们还没有进行身份验证。首先要做的是检查主机密钥的指纹是否与我们的已知主机匹配。你的应用程序可以硬编码它，可以去文件中读取，可以向用户展示，这取决于你。 */
    fingerprint = libssh2_hostkey_hash(session, LIBSSH2_HOSTKEY_HASH_SHA1);
    fprintf(stdout, "指纹: ");
    for (i = 0; i < 20; i++)
        fprintf(stdout, "%02X ", (unsigned char)fingerprint[i]);
    fprintf(stdout, "\n");

    /* 检查可用的身份验证方法 */
    userauthlist = libssh2_userauth_list(session, username, strlen(username));
    fprintf(stderr, "身份验证方法: %s\n", userauthlist);
    if (strstr(userauthlist, "password"))
        auth |= AUTH_PASSWORD;
    if (strstr(userauthlist, "publickey"))
        auth |= AUTH_PUBLICKEY;

    /* 检查选项 */
    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, "密码认证失败。\n");
            goto shutdown;
        }
    } else if (auth & AUTH_PUBLICKEY) {
        if (libssh2_userauth_publickey_fromfile(session, username, keyfile1, keyfile2, password)) {
            fprintf(stderr, "公钥认证失败！\n");
            goto shutdown;
        }
        fprintf(stderr, "公钥认证成功。\n");
    } else {
        fprintf(stderr, "未找到支持的认证方法！\n");
        goto shutdown;
    }

    fprintf(stdout, "请求服务器监听远程 %s:%d\n", remote_listenhost, remote_wantport);

    listener = libssh2_channel_forward_listen_ex(session, NULL, remote_wantport, &remote_listenport, 2);
    if (!listener) {
        fprintf(stderr, "无法启动tcpip-forward监听器！\n" "(请注意，这可能是服务器的问题！请查看服务器日志。）\n");
        goto shutdown;
    }

    fprintf(stdout, "服务器正在监听 %s:%d\n", remote_listenhost, remote_listenport);

    while (1) {
        fprintf(stdout, "等待远程连接\n");
        channel = libssh2_channel_forward_accept(listener);
        if (!channel) {
            fprintf(stderr, "libssh2_channel_forward_accept() 无法接受连接！\n" "(请注意，这可能是服务器的问题！请查看服务器日志。）\n");
            goto shutdown;
        }

        forward_tunnel(session, channel);
        libssh2_channel_free(channel);
        
    }

shutdown:
    if (channel)
        libssh2_channel_free(channel);
    if (listener)
        libssh2_channel_forward_cancel(listener);
    libssh2_session_disconnect(session, "客户端正常断开连接");
    libssh2_session_free(session);
    close(sock);
    libssh2_exit();
    return 0;
}