openprocess

OpenProcess is a Windows API function that opens an existing process object and returns a handle that can be used to perform operations on that process. It is provided by the Kernel32.dll library and is commonly used by system utilities, debuggers, and profiling tools to interact with a running process.

Prototype and parameters:

The function signature is HANDLE OpenProcess(DWORD dwDesiredAccess, BOOL bInheritHandle, DWORD dwProcessId). The dwDesiredAccess parameter specifies the access rights requested for the process, such as PROCESS_QUERY_INFORMATION, PROCESS_VM_READ, PROCESS_VM_WRITE, PROCESS_CREATE_THREAD, and PROCESS_TERMINATE. PROCESS_ALL_ACCESS exists but is restricted for security reasons. The bInheritHandle parameter indicates whether the returned handle should be inherited by child processes. The dwProcessId is the identifier of the target process.

Return value:

On success, OpenProcess returns a valid handle to the target process with the requested access. On failure, it returns NULL, and extended error information can be obtained with GetLastError a facility used to diagnose issues such as insufficient privileges or an invalid process ID.

Security and usage considerations:

Opening a process may require appropriate privileges, such as SeDebugPrivilege or elevated permissions, especially when targeting system or protected processes. Some processes may deny access due to security mitigations or protection mechanisms. Handles obtained from OpenProcess must be closed with CloseHandle to avoid resource leaks; the handle does not grant ongoing rights beyond the scope of the returned access mask.

See also:

Related functions include OpenProcessToken, ReadProcessMemory, WriteProcessMemory, VirtualAllocEx, CreateRemoteThread, SuspendThread, and TerminateProcess.