/*
 Derived from source code of TrueCrypt 7.1a, which is
 Copyright (c) 2008-2012 TrueCrypt Developers Association and which is governed
 by the TrueCrypt License 3.0.

 Modifications and additions to the original source code (contained in this file)
 and all other portions of this file are Copyright (c) 2013-2017 IDRIX
 and are governed by the Apache License 2.0 the full text of which is
 contained in the file License.txt included in VeraCrypt binary and source
 code distribution packages.
*/

#define FUSE_USE_VERSION  25
#include <errno.h>
#include <fcntl.h>
#include <fuse.h>
#include <iostream>
#include <signal.h>
#include <string.h>
#include <stdio.h>
#include <unistd.h>
#include <time.h>
#include <sys/mman.h>
#include <sys/time.h>
#include <sys/wait.h>

#include "FuseService.h"
#include "Platform/FileStream.h"
#include "Platform/MemoryStream.h"
#include "Platform/Serializable.h"
#include "Platform/SystemLog.h"
#include "Platform/Unix/Pipe.h"
#include "Platform/Unix/Poller.h"
#include "Volume/EncryptionThreadPool.h"
#include "Core/Core.h"

namespace VeraCrypt
{
	static int fuse_service_access (const char *path, int mask)
	{
		try
		{
			if (!FuseService::CheckAccessRights())
				return -EACCES;
		}
		catch (...)
		{
			return FuseService::ExceptionToErrorCode();
		}

		return 0;
	}

	static void *fuse_service_init ()
	{
		try
		{
			// Termination signals are handled by a separate process to allow clean dismount on shutdown
			struct sigaction action;
			Memory::Zero (&action, sizeof (action));
			action.sa_handler = SIG_IGN;

			sigaction (SIGINT, &action, nullptr);
			sigaction (SIGQUIT, &action, nullptr);
			sigaction (SIGTERM, &action, nullptr);

			if (!EncryptionThreadPool::IsRunning())
				EncryptionThreadPool::Start();
		}
		catch (exception &e)
		{
			SystemLog::WriteException (e);
		}
		catch (...)
		{
			SystemLog::WriteException (UnknownException (SRC_POS));
		}

		return nullptr;
	}

	static void fuse_service_destroy (void *userdata)
	{
		try
		{
			FuseService::Dismount();
		}
		catch (exception &e)
		{
			SystemLog::WriteException (e);
		}
		catch (...)
		{
			SystemLog::WriteException (UnknownException (SRC_POS));
		}
	}

	static int fuse_service_getattr (const char *path, struct stat *statData)
	{
		try
		{
			Memory::Zero (statData, sizeof(*statData));

			statData->st_uid = FuseService::GetUserId();
			statData->st_gid = FuseService::GetGroupId();
			statData->st_atime = time (NULL);
			statData->st_ctime = time (NULL);
			statData->st_mtime = time (NULL);

			if (strcmp (path, "/") == 0)
			{
				statData->st_mode = S_IFDIR | 0500;
				statData->st_nlink = 2;
			}
			else
			{
				if (!FuseService::CheckAccessRights())
					return -EACCES;

				if (strcmp (path, FuseService::GetVolumeImagePath()) == 0)
				{
					statData->st_mode = S_IFREG | 0600;
					statData->st_nlink = 1;
					statData->st_size = FuseService::GetVolumeSize();
				}
				else if (strcmp (path, FuseService::GetControlPath()) == 0)
				{
					statData->st_mode = S_IFREG | 0600;
					statData->st_nlink = 1;
					statData->st_size = FuseService::GetVolumeInfo()->Size();
				}
				else
				{
					return -ENOENT;
				}
			}
		}
		catch (...)
		{
			return FuseService::ExceptionToErrorCode();
		}

		return 0;
	}

	static int fuse_service_opendir (const char *path, struct fuse_file_info *fi)
	{
		try
		{
			if (!FuseService::CheckAccessRights())
				return -EACCES;

			if (strcmp (path, "/") != 0)
				return -ENOENT;
		}
		catch (...)
		{
			return FuseService::ExceptionToErrorCode();
		}

		return 0;
	}

	static int fuse_service_open (const char *path, struct fuse_file_info *fi)
	{
		try
		{
			if (!FuseService::CheckAccessRights())
				return -EACCES;

			if (strcmp (path, FuseService::GetVolumeImagePath()) == 0)
				return 0;

			if (strcmp (path, FuseService::GetControlPath()) == 0)
			{
				fi->direct_io = 1;
				return 0;
			}
		}
		catch (...)
		{
			return FuseService::ExceptionToErrorCode();
		}
		return -ENOENT;
	}

	static int fuse_service_read (const char *path, char *buf, size_t size, off_t offset, struct fuse_file_info *fi)
	{
		try
		{
			if (!FuseService::CheckAccessRights())
				return -EACCES;

			if (strcmp (path, FuseService::GetVolumeImagePath()) == 0)
			{
				try
				{
					// Test for read beyond the end of the volume
					if ((uint64) offset + size > FuseService::GetVolumeSize())
						size = FuseService::GetVolumeSize() - offset;

					size_t sectorSize = FuseService::GetVolumeSectorSize();
					if (size % sectorSize != 0 || offset % sectorSize != 0)
					{
						// Support for non-sector-aligned read operations is required by some loop device tools
						// which may analyze the volume image before attaching it as a device

						uint64 alignedOffset = offset - (offset % sectorSize);
						uint64 alignedSize = size + (offset % sectorSize);

						if (alignedSize % sectorSize != 0)
							alignedSize += sectorSize - (alignedSize % sectorSize);

						SecureBuffer alignedBuffer (alignedSize);

						FuseService::ReadVolumeSectors (alignedBuffer, alignedOffset);
						BufferPtr ((byte *) buf, size).CopyFrom (alignedBuffer.GetRange (offset % sectorSize, size));
					}
					else
					{
						FuseService::ReadVolumeSectors (BufferPtr ((byte *) buf, size), offset);
					}
				}
				catch (MissingVolumeData)
				{
					return 0;
				}

				return size;
			}

			if (strcmp (path, FuseService::GetControlPath()) == 0)
			{
				shared_ptr <Buffer> infoBuf = FuseService::GetVolumeInfo();
				BufferPtr outBuf ((byte *)buf, size);

				if (offset >= (off_t) infoBuf->Size())
					return 0;

				if (offset + size > infoBuf->Size())
					size = infoBuf->Size () - offset;

				outBuf.CopyFrom (infoBuf->GetRange (offset, size));
				return size;
			}
		}
		catch (...)
		{
			return FuseService::ExceptionToErrorCode();
		}

		return -ENOENT;
	}

	static int fuse_service_readdir (const char *path, void *buf, fuse_fill_dir_t filler, off_t offset, struct fuse_file_info *fi)
	{
		try
		{
			if (!FuseService::CheckAccessRights())
				return -EACCES;

			if (strcmp (path, "/") != 0)
				return -ENOENT;

			filler (buf, ".", NULL, 0);
			filler (buf, "..", NULL, 0);
			filler (buf, FuseService::GetVolumeImagePath() + 1, NULL, 0);
			filler (buf, FuseService::GetControlPath() + 1, NULL, 0);
		}
		catch (...)
		{
			return FuseService::ExceptionToErrorCode();
		}

		return 0;
	}

	static int fuse_service_write (const char *path, const char *buf, size_t size, off_t offset, struct fuse_file_info *fi)
	{
		try
		{
			if (!FuseService::CheckAccessRights())
				return -EACCES;

			if (strcmp (path, FuseService::GetVolumeImagePath()) == 0)
			{
				FuseService::WriteVolumeSectors (BufferPtr ((byte *) buf, size), offset);
				return size;
			}

			if (strcmp (path, FuseService::GetControlPath()) == 0)
			{
				if (FuseService::AuxDeviceInfoReceived())
					return -EACCES;

				FuseService::ReceiveAuxDeviceInfo (ConstBufferPtr ((const byte *)buf, size));
				return size;
			}
		}
#ifdef TC_FREEBSD
		// FreeBSD apparently retries failed write operations forever, which may lead to a system crash.
		catch (VolumeReadOnly&)
		{
			return size;
		}
		catch (VolumeProtected&)
		{
			return size;
		}
#endif
		catch (...)
		{
			return FuseService::ExceptionToErrorCode();
		}

		return -ENOENT;
	}

	bool FuseService::CheckAccessRights ()
	{
		return fuse_get_context()->uid == 0 || fuse_get_context()->uid == UserId;
	}

	void FuseService::CloseMountedVolume ()
	{
		if (MountedVolume)
		{
			// This process will exit before the use count of MountedVolume reaches zero
			if (MountedVolume->GetFile().use_count() > 1)
				MountedVolume->GetFile()->Close();

			if (MountedVolume.use_count() > 1)
				delete MountedVolume.get();

			MountedVolume.reset();
		}
	}

	void FuseService::Dismount ()
	{
		CloseMountedVolume();

		if (EncryptionThreadPool::IsRunning())
			EncryptionThreadPool::Stop();
	}

	int FuseService::ExceptionToErrorCode ()
	{
		try
		{
			throw;
		}
		catch (std::bad_alloc)
		{
			return -ENOMEM;
		}
		catch (ParameterIncorrect &e)
		{
			SystemLog::WriteException (e);
			return -EINVAL;
		}
		catch (VolumeProtected&)
		{
			return -EPERM;
		}
		catch (VolumeReadOnly&)
		{
			return -EPERM;
		}
		catch (SystemException &e)
		{
			SystemLog::WriteException (e);
			return -static_cast <int> (e.GetErrorCode());
		}
		catch (std::exception &e)
		{
			SystemLog::WriteException (e);
			return -EINTR;
		}
		catch (...)
		{
			SystemLog::WriteException (UnknownException (SRC_POS));
			return -EINTR;
		}
	}

	shared_ptr <Buffer> FuseService::GetVolumeInfo ()
	{
		shared_ptr <Stream> stream (new MemoryStream);

		{
			ScopeLock lock (OpenVolumeInfoMutex);

			OpenVolumeInfo.Set (*MountedVolume);
			OpenVolumeInfo.SlotNumber = SlotNumber;

			OpenVolumeInfo.Serialize (stream);
		}

		ConstBufferPtr infoBuf = dynamic_cast <MemoryStream&> (*stream);
		shared_ptr <Buffer> outBuf (new Buffer (infoBuf.Size()));
		outBuf->CopyFrom (infoBuf);

		return outBuf;
	}

	const char *FuseService::GetVolumeImagePath ()
	{
#ifdef TC_MACOSX
		return "/volume.dmg";
#else
		return "/volume";
#endif
	}

	uint64 FuseService::GetVolumeSize ()
	{
		if (!MountedVolume)
			throw NotInitialized (SRC_POS);

		return MountedVolume->GetSize();
	}

	void FuseService::Mount (shared_ptr <Volume> openVolume, VolumeSlotNumber slotNumber, const string &fuseMountPoint)
	{
		list <string> args;
		args.push_back (FuseService::GetDeviceType());
		args.push_back (fuseMountPoint);

#ifdef TC_MACOSX
		args.push_back ("-o");
		args.push_back ("noping_diskarb");
		args.push_back ("-o");
		args.push_back ("nobrowse");

		if (getuid() == 0 || geteuid() == 0)
#endif
		{
			args.push_back ("-o");
			args.push_back ("allow_other");
		}

		ExecFunctor execFunctor (openVolume, slotNumber);
		Process::Execute ("fuse", args, -1, &execFunctor);

		for (int t = 0; true; t++)
		{
			try
			{
				if (FilesystemPath (fuseMountPoint + FuseService::GetControlPath()).GetType() == FilesystemPathType::File)
					break;
			}
			catch (...)
			{
				if (t > 50)
					throw;

				Thread::Sleep (100);
			}
		}
	}

	void FuseService::ReadVolumeSectors (const BufferPtr &buffer, uint64 byteOffset)
	{
		if (!MountedVolume)
			throw NotInitialized (SRC_POS);

		MountedVolume->ReadSectors (buffer, byteOffset);
	}

	void FuseService::ReceiveAuxDeviceInfo (const ConstBufferPtr &buffer)
	{
		shared_ptr <Stream> stream (new MemoryStream (buffer));
		Serializer sr (stream);

		ScopeLock lock (OpenVolumeInfoMutex);
		OpenVolumeInfo.VirtualDevice = sr.DeserializeString ("VirtualDevice");
		OpenVolumeInfo.LoopDevice = sr.DeserializeString ("LoopDevice");
	}

	void FuseService::SendAuxDeviceInfo (const DirectoryPath &fuseMountPoint, const DevicePath &virtualDevice, const DevicePath &loopDevice)
	{
		File fuseServiceControl;
		fuseServiceControl.Open (string (fuseMountPoint) + GetControlPath(), File::OpenWrite);

		shared_ptr <Stream> stream (new MemoryStream);
		Serializer sr (stream);

		sr.Serialize ("VirtualDevice", string (virtualDevice));
		sr.Serialize ("LoopDevice", string (loopDevice));
		fuseServiceControl.Write (dynamic_cast <MemoryStream&> (*stream));
	}

	void FuseService::WriteVolumeSectors (const ConstBufferPtr &buffer, uint64 byteOffset)
	{
		if (!MountedVolume)
			throw NotInitialized (SRC_POS);

		MountedVolume->WriteSectors (buffer, byteOffset);
	}

	void FuseService::OnSignal (int signal)
	{
		try
		{
			shared_ptr <VolumeInfo> volume = Core->GetMountedVolume (SlotNumber);

			if (volume)
				Core->DismountVolume (volume, true);
		}
		catch (...) { }

		_exit (0);
	}

	void FuseService::ExecFunctor::operator() (int argc, char *argv[])
	{
		struct timeval tv;
		gettimeofday (&tv, NULL);
		FuseService::OpenVolumeInfo.SerialInstanceNumber = (uint64)tv.tv_sec * 1000000ULL + tv.tv_usec;

		FuseService::MountedVolume = MountedVolume;
		FuseService::SlotNumber = SlotNumber;

		FuseService::UserId = getuid();
		FuseService::GroupId = getgid();

		if (getenv ("SUDO_UID"))
		{
			try
			{
				string s (getenv ("SUDO_UID"));
				FuseService::UserId = static_cast <uid_t> (StringConverter::ToUInt64 (s));

				if (getenv ("SUDO_GID"))
				{
					s = getenv ("SUDO_GID");
					FuseService::GroupId = static_cast <gid_t> (StringConverter::ToUInt64 (s));
				}
			}
			catch (...) { }
		}

		static fuse_operations fuse_service_oper;

		fuse_service_oper.access = fuse_service_access;
		fuse_service_oper.destroy = fuse_service_destroy;
		fuse_service_oper.getattr = fuse_service_getattr;
		fuse_service_oper.init = fuse_service_init;
		fuse_service_oper.open = fuse_service_open;
		fuse_service_oper.opendir = fuse_service_opendir;
		fuse_service_oper.read = fuse_service_read;
		fuse_service_oper.readdir = fuse_service_readdir;
		fuse_service_oper.write = fuse_service_write;

		// Create a new session
		setsid ();

		// Fork handler of termination signals
		SignalHandlerPipe.reset (new Pipe);

		int forkedPid = fork();
		throw_sys_if (forkedPid == -1);

		if (forkedPid == 0)
		{
			CloseMountedVolume();

			struct sigaction action;
			Memory::Zero (&action, sizeof (action));
			action.sa_handler = OnSignal;

			sigaction (SIGINT, &action, nullptr);
			sigaction (SIGQUIT, &action, nullptr);
			sigaction (SIGTERM, &action, nullptr);

			// Wait for the exit of the main service
			byte buf[1];
			if (read (SignalHandlerPipe->GetReadFD(), buf, sizeof (buf))) { } // Errors ignored

			_exit (0);
		}

		SignalHandlerPipe->GetWriteFD();

		_exit (fuse_main (argc, argv, &fuse_service_oper));
	}

	VolumeInfo FuseService::OpenVolumeInfo;
	Mutex FuseService::OpenVolumeInfoMutex;
	shared_ptr <Volume> FuseService::MountedVolume;
	VolumeSlotNumber FuseService::SlotNumber;
	uid_t FuseService::UserId;
	gid_t FuseService::GroupId;
	auto_ptr <Pipe> FuseService::SignalHandlerPipe;
}
