mipt_2024_win_shell_server/server.c

#include "server.h"

#define BUFSIZE 4096
#define DEFAULT_PORT "50113"
#define DEFAULT_BUFLEN 512

// Handles for child process STDIN and STDOUT
HANDLE g_hChildStd_IN_Rd = NULL;
HANDLE g_hChildStd_IN_Wr = NULL;
HANDLE g_hChildStd_OUT_Rd = NULL;
HANDLE g_hChildStd_OUT_Wr = NULL;

SOCKET ClientSocket = INVALID_SOCKET;

//HANDLE g_hInputFile = NULL;

void StartShellServer() {
    printf("\n->Start of shell server execution.\n");

    CreatePipes();
    CreateSocket();

    // Create the child process. 
    CreateChildProcess();

    // TODO: split into threads
    WriteToPipe();
    // Read from pipe that is the standard output for child process. 
    ReadFromPipe();

    printf("\n->End of shell server execution.\n");

    // The remaining open handles are cleaned up when this process terminates. 
    // To avoid resource leaks in a larger application, close handles explicitly. 

}

void CreatePipes() {
    SECURITY_ATTRIBUTES saAttr;

    // Set the bInheritHandle flag so pipe handles are inherited. 

    saAttr.nLength = sizeof(SECURITY_ATTRIBUTES);
    saAttr.bInheritHandle = TRUE;
    saAttr.lpSecurityDescriptor = NULL;

    // Create a pipe for the child process's STDOUT. 

    if (!CreatePipe(&g_hChildStd_OUT_Rd, &g_hChildStd_OUT_Wr, &saAttr, 0))
        ErrorExit(TEXT("StdoutRd CreatePipe"));

    // Ensure the read handle to the pipe for STDOUT is not inherited.

    if (!SetHandleInformation(g_hChildStd_OUT_Rd, HANDLE_FLAG_INHERIT, 0))
        ErrorExit(TEXT("Stdout SetHandleInformation"));

    // Create a pipe for the child process's STDIN. 

    if (!CreatePipe(&g_hChildStd_IN_Rd, &g_hChildStd_IN_Wr, &saAttr, 0))
        ErrorExit(TEXT("Stdin CreatePipe"));

    // Ensure the write handle to the pipe for STDIN is not inherited. 

    if (!SetHandleInformation(g_hChildStd_IN_Wr, HANDLE_FLAG_INHERIT, 0))
        ErrorExit(TEXT("Stdin SetHandleInformation"));
}

// TODO: to review
void CreateSocket() {
    WSADATA wsaData;
    struct addrinfo* result = NULL, * ptr = NULL, hints;
    SOCKET ListenSocket = INVALID_SOCKET;

    int iResult;

    // Initialize Winsock
    iResult = WSAStartup(MAKEWORD(2, 2), &wsaData);
    if (iResult != 0) {
        printf("WSAStartup failed: %d\n", iResult);
        return 1;
    }

    // Creating socket
    ZeroMemory(&hints, sizeof(hints));
    hints.ai_family = AF_INET;
    hints.ai_socktype = SOCK_STREAM;
    hints.ai_protocol = IPPROTO_TCP;
    hints.ai_flags = AI_PASSIVE;

    // Resolve the local address and port to be used by the server
    iResult = getaddrinfo(NULL, DEFAULT_PORT, &hints, &result);
    if (iResult != 0) {
        printf("getaddrinfo failed: %d\n", iResult);
        WSACleanup();
        return 1;
    }

    ListenSocket = socket(result->ai_family, result->ai_socktype, result->ai_protocol);

    if (ListenSocket == INVALID_SOCKET) {
        printf("Error at socket(): %ld\n", WSAGetLastError());
        freeaddrinfo(result);
        WSACleanup();
        return 1;
    }

    // Binding socket
    // Setup the TCP listening socket
    iResult = bind(ListenSocket, result->ai_addr, (int)result->ai_addrlen);
    if (iResult == SOCKET_ERROR) {
        printf("bind failed with error: %d\n", WSAGetLastError());
        freeaddrinfo(result);
        closesocket(ListenSocket);
        WSACleanup();
        return 1;
    }
    // No longer needed
    freeaddrinfo(result);

    // Listening socket
    if (listen(ListenSocket, SOMAXCONN) == SOCKET_ERROR) {
        printf("Listen failed with error: %ld\n", WSAGetLastError());
        closesocket(ListenSocket);
        WSACleanup();
        return 1;
    }

    // Accepting a connection
    ClientSocket = INVALID_SOCKET;

    // Accept a client socket
    ClientSocket = accept(ListenSocket, NULL, NULL);
    if (ClientSocket == INVALID_SOCKET) {
        printf("accept failed: %d\n", WSAGetLastError());
        closesocket(ListenSocket);
        WSACleanup();
        return 1;
    }
    // No longer needed
    closesocket(ListenSocket);
}

void CreateChildProcess()
// Create a child process that uses the previously created pipes for STDIN and STDOUT.
{
    TCHAR szCmdline[] = TEXT("C:\\Windows\\System32\\cmd.exe");
    PROCESS_INFORMATION piProcInfo;
    STARTUPINFO siStartInfo;
    BOOL bSuccess = FALSE;

    // Set up members of the PROCESS_INFORMATION structure. 

    ZeroMemory(&piProcInfo, sizeof(PROCESS_INFORMATION));

    // Set up members of the STARTUPINFO structure. 
    // This structure specifies the STDIN and STDOUT handles for redirection.

    ZeroMemory(&siStartInfo, sizeof(STARTUPINFO));
    siStartInfo.cb = sizeof(STARTUPINFO);
    siStartInfo.hStdError = g_hChildStd_OUT_Wr;
    siStartInfo.hStdOutput = g_hChildStd_OUT_Wr;
    siStartInfo.hStdInput = g_hChildStd_IN_Rd;
    siStartInfo.dwFlags |= STARTF_USESTDHANDLES;

    // Create the child process. 

    bSuccess = CreateProcess(NULL,
        szCmdline,     // command line 
        NULL,          // process security attributes 
        NULL,          // primary thread security attributes 
        TRUE,          // handles are inherited 
        0,             // creation flags 
        NULL,          // use parent's environment 
        NULL,          // use parent's current directory 
        &siStartInfo,  // STARTUPINFO pointer 
        &piProcInfo);  // receives PROCESS_INFORMATION 

    // If an error occurs, exit the application. 
    if (!bSuccess)
        ErrorExit(TEXT("CreateProcess"));
    else
    {
        // Close handles to the child process and its primary thread.
        // Some applications might keep these handles to monitor the status
        // of the child process, for example. 

        CloseHandle(piProcInfo.hProcess);
        CloseHandle(piProcInfo.hThread);

        // Close handles to the stdin and stdout pipes no longer needed by the child process.
        // If they are not explicitly closed, there is no way to recognize that the child process has ended.

        CloseHandle(g_hChildStd_OUT_Wr);
        CloseHandle(g_hChildStd_IN_Rd);
    }
}

void WriteToPipe(void)

// Read from a file and write its contents to the pipe for the child's STDIN.
// Stop when there is no more data. 
{
    DWORD dwRead, dwWritten;
    //CHAR chBuf[BUFSIZE] = "dir\r\n";
    BOOL bSuccess = FALSE;
    int i = 0;

    char recvbuf[DEFAULT_BUFLEN];
    int iResult, iSendResult;
    int recvbuflen = DEFAULT_BUFLEN;
    

    do
    {
        iResult = recv(ClientSocket, recvbuf, recvbuflen, 0);
        if (iResult > 0) {
            printf("Bytes received: %d\n", iResult);

            // Echo the buffer back to the sender
            iSendResult = send(ClientSocket, recvbuf, iResult, 0);
            if (iSendResult == SOCKET_ERROR) {
                printf("send failed: %d\n", WSAGetLastError());
                closesocket(ClientSocket);
                WSACleanup();
                return 1;
            }
            printf("Bytes sent: %d\n", iSendResult);
        }
        else if (iResult == 0)
            printf("Connection closing...\n");
        else {
            printf("recv failed: %d\n", WSAGetLastError());
            closesocket(ClientSocket);
            WSACleanup();
            return 1;
        }

        //dwRead = strlen(chBuf) + 1;
        bSuccess = WriteFile(g_hChildStd_IN_Wr, recvbuf, iResult, &dwWritten, NULL);
        if (!bSuccess) break;
        //break;
        //dwRead = strlen(chBuf) + 1;
        //bSuccess = WriteFile(g_hChildStd_IN_Wr, chBuf, dwRead, &dwWritten, NULL);
        //if (!bSuccess) break;
        ReadFromPipe();
    } while (iResult > 0);

    // Close the pipe handle so the child process stops reading. 

    if (!CloseHandle(g_hChildStd_IN_Wr))
        ErrorExit(TEXT("StdInWr CloseHandle"));
}

void ReadFromPipe(void)

// Read output from the child process's pipe for STDOUT
// and write to the parent process's pipe for STDOUT. 
// Stop when there is no more data. 
{
    DWORD dwRead, dwWritten;
    CHAR chBuf[BUFSIZE];
    BOOL bSuccess = FALSE;
    HANDLE hParentStdOut = GetStdHandle(STD_OUTPUT_HANDLE);

    int iSendResult;

    for (;;)
    {
        bSuccess = ReadFile(g_hChildStd_OUT_Rd, chBuf, BUFSIZE, &dwRead, NULL);
        if (!bSuccess || dwRead == 0) break;

        iSendResult = send(ClientSocket, chBuf, dwRead, 0);
        if (iSendResult == SOCKET_ERROR) {
            printf("send failed: %d\n", WSAGetLastError());
            closesocket(ClientSocket);
            WSACleanup();
            return 1;
        }
        // Write to console
        bSuccess = WriteFile(hParentStdOut, chBuf,
            dwRead, &dwWritten, NULL);
        if (!bSuccess) break;
        break;
    }
}

void ErrorExit(PCTSTR lpszFunction)

// Format a readable error message, display a message box, 
// and exit from the application.
{
    LPVOID lpMsgBuf;
    LPVOID lpDisplayBuf;
    DWORD dw = GetLastError();

    FormatMessage(
        FORMAT_MESSAGE_ALLOCATE_BUFFER |
        FORMAT_MESSAGE_FROM_SYSTEM |
        FORMAT_MESSAGE_IGNORE_INSERTS,
        NULL,
        dw,
        MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
        (LPTSTR)&lpMsgBuf,
        0, NULL);

    lpDisplayBuf = (LPVOID)LocalAlloc(LMEM_ZEROINIT,
        (lstrlen((LPCTSTR)lpMsgBuf) + lstrlen((LPCTSTR)lpszFunction) + 40) * sizeof(TCHAR));
    StringCchPrintf((LPTSTR)lpDisplayBuf,
        LocalSize(lpDisplayBuf) / sizeof(TCHAR),
        TEXT("%s failed with error %d: %s"),
        lpszFunction, dw, lpMsgBuf);
    MessageBox(NULL, (LPCTSTR)lpDisplayBuf, TEXT("Error"), MB_OK);

    LocalFree(lpMsgBuf);
    LocalFree(lpDisplayBuf);
    ExitProcess(1);
}