Add injector

Implements classic DLL injection via CreateRemoteThread. Opens the target process, allocates remote memory for the DLL path, writes it, then spawns a remote thread pointing to LoadLibraryA.

injector.c

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+// injector.c
+// Classic DLL injection via CreateRemoteThread.
+//
+// Technique overview:
+//   1. Open a handle to the target process
+//   2. Allocate memory in the target process for the DLL path string
+//   3. Write the DLL path into that memory
+//   4. Spawn a remote thread in the target that calls LoadLibraryA(<dll path>)
+//      -> Windows loads the DLL into the target process
+//      -> DllMain is called automatically by the loader
+
+#include <stdio.h>
+#include <windows.h>
+
+int main(int argc, char* argv[])
+{
+    if (argc != 3) {
+        printf("Usage: injector.exe <PID> <full path to DLL>\n");
+        printf("Example: injector.exe 1234 C:\\path\\to\\MyDll.dll\n");
+        return 1;
+    }
+
+    DWORD targetPID = (DWORD)atoi(argv[1]);
+    char* dllPath   = argv[2];
+    size_t pathLen  = strlen(dllPath) + 1;
+
+    printf("[*] Target PID : %lu\n", targetPID);
+    printf("[*] DLL path   : %s\n", dllPath);
+
+    // Step 1: Open a handle to the target process
+    HANDLE hProcess = OpenProcess(PROCESS_ALL_ACCESS, FALSE, targetPID);
+    if (hProcess == NULL) {
+        printf("[-] OpenProcess failed. Error: %lu\n", GetLastError());
+        return 1;
+    }
+    printf("[+] Opened process handle: 0x%p\n", hProcess);
+
+    // Step 2: Allocate memory inside the target process for the DLL path string.
+    //         Only needs RW permissions — it holds data, not code.
+    LPVOID remoteBuffer = VirtualAllocEx(
+        hProcess,
+        NULL,
+        pathLen,
+        MEM_COMMIT | MEM_RESERVE,
+        PAGE_READWRITE
+    );
+    if (remoteBuffer == NULL) {
+        printf("[-] VirtualAllocEx failed. Error: %lu\n", GetLastError());
+        CloseHandle(hProcess);
+        return 1;
+    }
+    printf("[+] Allocated remote buffer at: 0x%p\n", remoteBuffer);
+
+    // Step 3: Write the DLL path into the allocated buffer
+    if (!WriteProcessMemory(hProcess, remoteBuffer, dllPath, pathLen, NULL)) {
+        printf("[-] WriteProcessMemory failed. Error: %lu\n", GetLastError());
+        VirtualFreeEx(hProcess, remoteBuffer, 0, MEM_RELEASE);
+        CloseHandle(hProcess);
+        return 1;
+    }
+    printf("[+] DLL path written to remote buffer\n");
+
+    // Step 4: Create a remote thread that calls LoadLibraryA with our DLL path.
+    //         LoadLibraryA is in kernel32.dll which is mapped at the same address
+    //         in every process, so we can resolve it locally and use it remotely.
+    LPTHREAD_START_ROUTINE loadLibraryAddr =
+        (LPTHREAD_START_ROUTINE)GetProcAddress(GetModuleHandle("kernel32.dll"), "LoadLibraryA");
+
+    HANDLE hThread = CreateRemoteThread(
+        hProcess,
+        NULL,
+        0,
+        loadLibraryAddr,
+        remoteBuffer, // argument passed to LoadLibraryA = the DLL path
+        0,
+        NULL
+    );
+    if (hThread == NULL) {
+        printf("[-] CreateRemoteThread failed. Error: %lu\n", GetLastError());
+        VirtualFreeEx(hProcess, remoteBuffer, 0, MEM_RELEASE);
+        CloseHandle(hProcess);
+        return 1;
+    }
+    printf("[+] Remote thread created. Thread ID visible in Process Hacker.\n");
+
+    // Wait for LoadLibraryA to finish, then clean up
+    WaitForSingleObject(hThread, INFINITE);
+    printf("[+] Injection complete.\n");
+
+    CloseHandle(hThread);
+    VirtualFreeEx(hProcess, remoteBuffer, 0, MEM_RELEASE);
+    CloseHandle(hProcess);
+
+    return 0;
+}