背景

部分服务器只开80/443端口，那么只往服务器的80/443发送数据，而有的情况下，我们需要在内部监听一个9999端口，怎么让数据能正常通过80然后到9999呢？

利用

驱动使用的是WinDivert，开源，之前的blog有相关的介绍。

代码如下，作为demo只处理80端口。

简单说一下，tcp连接都会先进行三次握手，我们刻意开的9999端口和默认开启的80端口都是基于tcp协议的，怎么分辨我们的特殊数据呢？这里比较随意（改成异或或者位移不难吧？），当第一位是字符1的时候，就认为是需要转发到9999的数据，这里不能直接转发到9999，必须要先给80发一个rst中止连接。

为什么？因为我们收到特殊数据的时候80和你的客户端已经完成了三次握手，你和9999都完全没有握手。tcp是可靠的协议，在没有和9999握手的前提下，直接发数据9999是不会理你的，所以我们先中止和80的连接，记录下src的ip，当你下一次来的时候，直接发往9999进行三次握手和数据传输。

#include <winsock2.h>
#include <windows.h>
#include <ctype.h>
#include <stdio.h>
#include <stdlib.h>
#include "windivert.h"#define MAXBUF          WINDIVERT_MTU_MAXtypedef struct
{WINDIVERT_IPHDR  ip;WINDIVERT_TCPHDR tcp;
} PACKET, * PPACKET;void PacketInit(PPACKET packet)
{memset(packet, 0, sizeof(PACKET));packet->ip.Version = 4;packet->ip.HdrLength = sizeof(WINDIVERT_IPHDR) / sizeof(UINT32);packet->ip.Length = htons(sizeof(PACKET));packet->ip.TTL = 64;packet->ip.Protocol = IPPROTO_TCP;packet->tcp.HdrLength = sizeof(WINDIVERT_TCPHDR) / sizeof(UINT32);
}BOOLEAN g_ok = FALSE;
int main()
{PACKET reset0;PPACKET reset = &reset0;PacketInit(reset);reset->tcp.Rst = 1;reset->tcp.Ack = 1;UINT32 pyloadIP = NULL;PVOID payload = NULL;UINT payload_len = NULL;UINT packet_len = NULL;unsigned char packet[MAXBUF];WINDIVERT_ADDRESS addr = { 0 };PWINDIVERT_IPHDR ip_header = NULL;PWINDIVERT_TCPHDR tcp_header = NULL;HANDLE handle = WinDivertOpen(" tcp.DstPort == 80 or tcp.SrcPort == 9999", WINDIVERT_LAYER_NETWORK, 0, 0);if (handle == INVALID_HANDLE_VALUE)return 0;while (1){//这里一直在接收数据包if (!WinDivertRecv(handle, packet, sizeof(packet), &packet_len, &addr)){printf("failed to read packet (%d) \n", GetLastError());continue;}WinDivertHelperParsePacket(packet, packet_len, &ip_header, NULL, NULL, NULL, NULL, &tcp_header, NULL, &payload, &payload_len, NULL, NULL);if (ip_header == NULL || tcp_header == NULL){printf("failed to parse packet (%d) \n", GetLastError());continue;}char* buf = (char*)payload;if (payload && buf[0] == '1' &&  !pyloadIP){if (!addr.Outbound){//首先中止第一个连接    -->告诉80端口已经结束了reset->ip.SrcAddr = ip_header->SrcAddr;reset->ip.DstAddr = ip_header->DstAddr;reset->tcp.SrcPort = tcp_header->SrcPort;reset->tcp.DstPort = htons(80);reset->tcp.SeqNum = tcp_header->SeqNum;reset->tcp.AckNum = tcp_header->AckNum;WinDivertHelperCalcChecksums((PVOID)reset, sizeof(PACKET), &addr, 0);if (!WinDivertSend(handle, (PVOID)reset, sizeof(PACKET), NULL, &addr)){printf("error reset\n");}pyloadIP = ip_header->SrcAddr;}continue;}//这里将端口重定向if (pyloadIP && (pyloadIP == ip_header->SrcAddr || pyloadIP == ip_header->DstAddr)){if (addr.Outbound){if (tcp_header->SrcPort == htons(9999)){tcp_header->SrcPort = htons(80);}}else{if (tcp_header->DstPort == htons(80)){tcp_header->DstPort = htons(9999);}}}WinDivertHelperCalcChecksums(packet, packet_len, &addr, 0);UINT writeLen = NULL;if (!WinDivertSend(handle, packet, packet_len, &writeLen, &addr)){printf("failed to send packet (%d) \n", GetLastError());continue;}}return 0;
}

client测试代码

#include<stdio.h>
#include<windows.h>
#include<winsock.h>#define SERVERPORT 80
#define SERVERIP "192.168.1.2"
#pragma comment(lib,"ws2_32.lib")int main(int argc, char* argv[])
{struct sockaddr_in serAddr;SOCKET cliSocket;int conn;WSADATA Ws;char sendBuf[1024];int sen;int recvR;fd_set rfds;/struct timeval time;///int maxrd = 0;int ret;/if (WSAStartup(MAKEWORD(2, 2), &Ws) != 0){printf("init windows socket failed:%d\n", GetLastError());return -1;}cliSocket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);if (cliSocket == INVALID_SOCKET){printf("window socket failed:%d\n", GetLastError());return -1;}serAddr.sin_family = AF_INET;serAddr.sin_addr.s_addr = inet_addr(SERVERIP);serAddr.sin_port = htons(SERVERPORT);memset(serAddr.sin_zero, 0x00, 8);conn = connect(cliSocket, (struct sockaddr*) & serAddr, sizeof(serAddr));if (conn == SOCKET_ERROR){printf("connect socket failed:%d\n", GetLastError());return -1;}else{printf("connect successfully!\n");}while (true){FD_ZERO(&rfds);/FD_SET(0, &rfds);/FD_SET(cliSocket, &rfds);/time.tv_sec = 1;/time.tv_usec = 0;//maxrd = ((maxrd > cliSocket) ? maxrd : cliSocket);ret = select(maxrd + 1, &rfds, NULL, NULL, &time);if (ret == 0)continue;else {if (FD_ISSET(0, &rfds)){memset(sendBuf, 0x00, sizeof(sendBuf));system("pause");sen = send(cliSocket, "111111199999", (int)strlen("111111199999"), 0);if (sen == SOCKET_ERROR){printf("send info error:%d\n", GetLastError());break;}}if (FD_ISSET(cliSocket, &rfds)){memset(sendBuf, 0x00, sizeof(sendBuf));recvR = recv(cliSocket, sendBuf, 1024, 0);printf("recieve from server:%s\n", sendBuf);}}}closesocket(cliSocket);WSACleanup();return 0;
}

server的测试代码

#include<windows.h>
#include<stdio.h>
#include<winsock.h>#define SERVER_PORT 80
#define SERVER_IP  "0.0.0.0"
#pragma comment(lib,"ws2_32.lib")DWORD Demo()
{SOCKET serSocket, cliSocket;struct sockaddr_in localAddr, clientAddr;WSADATA Ws;int Bit;int Lit;char recvBuf[1024];int recvR, sen;int cliLen;fd_set rfds;//struct timeval time;//int maxrd = 0;//int ret;//if (WSAStartup(MAKEWORD(2, 2), &Ws) != 0){printf("init windows socket failed:%d\n", GetLastError());return -1;}serSocket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);if (serSocket == INVALID_SOCKET){printf("create socket failed:%d\n", GetLastError());return -1;}localAddr.sin_family = AF_INET;localAddr.sin_port = htons(SERVER_PORT);localAddr.sin_addr.s_addr = inet_addr(SERVER_IP);memset(localAddr.sin_zero, 0x00, 8);Bit = bind(serSocket, (struct sockaddr*) & localAddr, sizeof(localAddr));if (Bit != 0){printf("bind failed:%d\n", GetLastError());return -1;}Lit = listen(serSocket, 5);if (Lit != 0){printf("listen failed:%d\n", GetLastError());return -1;}printf("server has been startup\n");while (true){cliLen = sizeof(clientAddr);cliSocket = accept(serSocket, (struct sockaddr*) & clientAddr, &cliLen);if (cliSocket == INVALID_SOCKET){printf("accept failed:%d\n", GetLastError());return -1;}//printf("client connect%d:%d\n", inet_ntoa(clientAddr.sin_addr), clientAddr.sin_port);/while (true){FD_ZERO(&rfds);///FD_SET(0, &rfds);FD_SET(cliSocket, &rfds);time.tv_sec = 1;time.tv_usec = 0;/maxrd = (maxrd > cliSocket ? maxrd : cliSocket);/ret = select(maxrd + 1, &rfds, NULL, NULL, &time);if (ret == 0)//continue;else {if (FD_ISSET(0, &rfds)){ /memset(recvBuf, 0x00, sizeof(recvBuf));recvR = recv(cliSocket, recvBuf, 1024, 0);if (recvR == 0 || recvR == SOCKET_ERROR){printf("the client had quit\n");break;}printf("recieve message:%s\n", recvBuf);}if (FD_ISSET(cliSocket, &rfds)){memset(recvBuf, 0x00, sizeof(recvBuf));//gets(recvBuf);sen = send(cliSocket, "19999", sizeof("19999"), 0);}}}return 0;}closesocket(serSocket);closesocket(cliSocket);WSACleanup();return 0;
}int main()
{Demo();
}

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WFP实现的端口复用

背景

利用

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