/*
 * Process Hacker
 * 
 * Copyright (C) 2008 wj32
 * 
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

using System;
using System.Runtime.InteropServices;

namespace ProcessHacker
{
    public partial class Win32
    {
        /// <summary>
        /// Represents a handle to a Windows process.
        /// </summary>
        public class ProcessHandle : Win32Handle, IWithToken
        {
            /// <summary>
            /// Specifies an offset in a process' process environment block (PEB).
            /// </summary>
            public enum PEBOffset
            {
                CurrentDirectoryPath = 0x24,
                DllPath = 0x30,
                ImagePathName = 0x38,
                CommandLine = 0x40,
                WindowTitle = 0x70,
                DesktopName = 0x78,
                ShellInfo = 0x80,
                RuntimeData = 0x88
            }

            [Flags]
            public enum DEPStatus
            {
                Enabled = 0x1, Permanent, ATLThunkEmulationDisabled
            }

            /// <summary>
            /// Creates a process handle using an existing handle. 
            /// The handle will not be closed automatically.
            /// </summary>
            /// <param name="Handle">The handle value.</param>
            /// <returns>The process handle.</returns>
            public static ProcessHandle FromHandle(int Handle)
            {
                return new ProcessHandle(Handle, false);
            }

            internal ProcessHandle(int Handle, bool Owned)
                : base(Handle, Owned)
            { }

            /// <summary>
            /// Creates a new process handle.
            /// </summary>
            /// <param name="PID">The ID of the process to open.</param>
            public ProcessHandle(int PID)
                : this(PID, PROCESS_RIGHTS.PROCESS_ALL_ACCESS)
            { }

            /// <summary>
            /// Creates a new process handle.
            /// </summary>
            /// <param name="PID">The ID of the process to open.</param>
            /// <param name="access">The desired access to the process.</param>
            public ProcessHandle(int PID, PROCESS_RIGHTS access)
            {
                this.Handle = OpenProcess(access, 0, PID);

                if (this.Handle == 0)
                    throw new Exception(GetLastErrorMessage());
            }

            /// <summary>
            /// Creates a remote thread in the process.
            /// </summary>
            /// <param name="startAddress">The address at which to begin execution (e.g. a function).</param>
            /// <param name="parameter">The parameter to pass to the function.</param>
            /// <returns>The ID of the new thread.</returns>
            public int CreateThread(int startAddress, int parameter)
            {
                int threadId;

                if (!CreateRemoteThread(this, 0, 0, startAddress, parameter, 0, out threadId))
                    throw new Exception(GetLastErrorMessage());

                return threadId;
            }

            /// <summary>
            /// Gets the process' basic information through the undocumented Native API function 
            /// ZwQueryInformationProcess. This function requires the PROCESS_QUERY_LIMITED_INFORMATION 
            /// permission.
            /// </summary>
            /// <returns>A PROCESS_BASIC_INFORMATION structure.</returns>
            public PROCESS_BASIC_INFORMATION GetBasicInformation()
            {
                PROCESS_BASIC_INFORMATION pbi = new PROCESS_BASIC_INFORMATION();
                int retLen;

                if (ZwQueryInformationProcess(this, PROCESS_INFORMATION_CLASS.ProcessBasicInformation,
                    ref pbi, Marshal.SizeOf(pbi), out retLen) != 0)
                    throw new Exception(GetLastErrorMessage());

                return pbi;
            }

            /// <summary>
            /// Gets the command line used to start the process. This requires 
            /// the PROCESS_QUERY_LIMITED_INFORMATION and PROCESS_VM_READ permissions.
            /// </summary>
            /// <returns>A string.</returns>
            public string GetCommandLine()
            {
                return this.GetPEBString(PEBOffset.CommandLine);
            }

            /// <summary>
            /// Gets the process' DEP policy.
            /// </summary>
            /// <returns>A DEPStatus enum.</returns>
            public DEPStatus GetDEPStatus()
            {
                DEPFLAGS flags;
                int perm;

                if (!GetProcessDEPPolicy(this, out flags, out perm))
                    throw new Exception(GetLastErrorMessage());

                return
                    ((flags & DEPFLAGS.PROCESS_DEP_ENABLE) != 0 ? DEPStatus.Enabled : 0) |
                    ((flags & DEPFLAGS.PROCESS_DEP_DISABLE_ATL_THUNK_EMULATION) != 0 ? 
                    (DEPStatus.Enabled | DEPStatus.ATLThunkEmulationDisabled) : 0) |
                    ((perm != 0) ? DEPStatus.Permanent : 0);
            }

            /// <summary>
            /// Gets the file name of the process' image. This requires 
            /// the PROCESS_QUERY_LIMITED_INFORMATION and PROCESS_VM_READ permissions.
            /// </summary>
            /// <returns>A file name, in kernel file name format.</returns>
            public string GetImageFileName()
            {
                return this.GetPEBString(PEBOffset.ImagePathName);
            }

            /// <summary>
            /// Gets the process' parent's process ID. This requires 
            /// the PROCESS_QUERY_LIMITED_INFORMATION permission.
            /// </summary>
            /// <returns>The process ID.</returns>
            public int GetParentPID()
            {
                return this.GetBasicInformation().InheritedFromUniqueProcessId;
            }

            /// <summary>
            /// Reads a UNICODE_STRING from the process' process environment block.
            /// </summary>
            /// <param name="offset">The offset to the UNICODE_STRING structure.</param>
            /// <returns>A string.</returns>
            public string GetPEBString(PEBOffset offset)
            {
                int readLen;
                int pebBaseAddress = 0x7ffd7000;

                try
                {
                    pebBaseAddress = this.GetBasicInformation().PebBaseAddress;
                }
                catch
                { }

                byte[] data2 = new byte[4];

                // read address of parameter information block
                if (!ReadProcessMemory(this, pebBaseAddress + 16, data2, 4, out readLen))
                    throw new Exception(GetLastErrorMessage());

                int paramInfoAddrI = Misc.BytesToInt(data2, Misc.Endianness.Little);

                // read length of string
                if (!ReadProcessMemory(this, paramInfoAddrI + (int)offset, data2, 2, out readLen))
                    throw new Exception(GetLastErrorMessage());

                ushort strLength = Misc.BytesToUShort(data2, Misc.Endianness.Little);
                byte[] stringData = new byte[strLength];

                // read address of string
                if (!ReadProcessMemory(this, paramInfoAddrI + (int)offset + 4, data2, 4, out readLen))
                    throw new Exception(GetLastErrorMessage());

                int strAddr = Misc.BytesToInt(data2, Misc.Endianness.Little);

                // read string
                if (!ReadProcessMemory(this, strAddr, stringData, strLength, out readLen))
                    throw new Exception(GetLastErrorMessage());

                // return decoded unicode string
                return System.Text.UnicodeEncoding.Unicode.GetString(stringData).TrimEnd('\0');
            }

            /// <summary>
            /// Gets whether the process is currently being debugged. This requires 
            /// the PROCESS_QUERY_INFORMATION permission.
            /// </summary>
            /// <returns>A boolean value.</returns>
            public bool IsBeingDebugged()
            {
                bool debugged;

                if (!Win32.CheckRemoteDebuggerPresent(this, out debugged))
                    throw new Exception(GetLastErrorMessage());

                return debugged;
            }

            /// <summary>
            /// Waits for the process.
            /// </summary>
            /// <param name="Timeout">The timeout of the wait.</param>
            /// <returns>Either WAIT_OBJECT_0, WAIT_TIMEOUT or WAIT_FAILED.</returns>
            public int Wait(int Timeout)
            {
                return WaitForSingleObject(this.Handle, Timeout);
            }

            /// <summary>
            /// Terminates the process. This requires the PROCESS_TERMINATE permission.
            /// </summary>
            public void Terminate()
            {
                this.Terminate(0);
            }

            /// <summary>
            /// Terminates the process, specifying the exit code. This requires the 
            /// PROCESS_TERMINATE permission.
            /// </summary>
            /// <param name="ExitCode">The exit code.</param>
            public void Terminate(int ExitCode)
            {
                if (!TerminateProcess(this, ExitCode))
                    throw new Exception(GetLastErrorMessage());
            }

            /// <summary>
            /// Opens and returns a handle to the process' token. This requires the 
            /// PROCESS_QUERY_LIMITED_INFORMATION permission.
            /// </summary>
            /// <returns>A handle to the process' token.</returns>
            public TokenHandle GetToken()
            {
                return GetToken(TOKEN_RIGHTS.TOKEN_ALL_ACCESS);
            }

            /// <summary>
            /// Opens and returns a handle to the process' token. This requires the 
            /// PROCESS_QUERY_LIMITED_INFORMATION permission.
            /// </summary>
            /// <param name="access">The desired access to the token.</param>
            /// <returns>A handle to the process' token.</returns>
            public TokenHandle GetToken(TOKEN_RIGHTS access)
            {
                return new TokenHandle(this, access);
            }
        }
    }
}