/*
 # Copyright (c) 2009 - OpenSLX Project, Computer Center University of Freiburg
 #
 # This program is free software distributed under the GPL version 2.
 # See http://openslx.org/COPYING
 #
 # If you have any feedback please consult http://openslx.org/feedback and
 # send your suggestions, praise, or complaints to feedback@openslx.org
 #
 # General information about OpenSLX can be found at http://openslx.org/
 # --------------------------------------------------------------------------
 # pvsCheckPrivileges.cpp:
 #  - A small program that checks whether or not it is called from
 #    a physical seat and conditionally executes the pvs input daemon.
 #    Additional security-relevant conditions should be checked here.
 #
 #    The program is called with exactly one parameter, specifying the
 #    number of the file descriptor which is to be passed to its child.
 # --------------------------------------------------------------------------
 */

#include <unistd.h>
#include <iostream>
#include <cerrno>
#include <cstdlib>
#include <QCoreApplication>
#include <QDir>
#include <QFileInfo>
#include <QTimer>
#include <QtDBus/QDBusArgument>
#include <QtDBus/QDBusConnection>
#include <QtDBus/QDBusInterface>
#include <QtDBus/QDBusMetaType>
#include <QtDBus/QDBusReply>
#include <QtGlobal>
#include <QDebug>
#include <QUuid>
#include "pvsCheckPrivileges.h"

using namespace std;

#define TIMEOUT_VALUE 10000 /* Wait for max. 10 seconds */

// We need these classes for PolicyKit access:
struct PolKitSubject {
	QString subject_kind;
	QMap<QString, QVariant> subject_details;
};
Q_DECLARE_METATYPE(PolKitSubject);

QDBusArgument& operator<<(QDBusArgument& arg, PolKitSubject const& subj)
{
	arg.beginStructure();
	arg << subj.subject_kind << subj.subject_details;
	arg.endStructure();
	return arg;
}

QDBusArgument const& operator>>(QDBusArgument const& arg, PolKitSubject& subj)
{
	arg.beginStructure();
	arg >> subj.subject_kind >> subj.subject_details;
	arg.endStructure();
	return arg;
}

struct PolKitAuthReply {
	bool isAuthorized;
	bool isChallenge;
	QMap<QString, QString> details;
};
Q_DECLARE_METATYPE(PolKitAuthReply);

QDBusArgument& operator<<(QDBusArgument& arg, PolKitAuthReply const& reply)
{
	arg.beginStructure();
	arg << reply.isAuthorized << reply.isChallenge << reply.details;
	arg.endStructure();
	return arg;
}

QDBusArgument const& operator>>(QDBusArgument const& arg, PolKitAuthReply& reply)
{
	arg.beginStructure();
	arg >> reply.isAuthorized >> reply.isChallenge >> reply.details;
	arg.endStructure();
	return arg;
}

// We need to pass QMap<QString, QString> to QVariant:
typedef QMap<QString, QString> QStringStringMap;
Q_DECLARE_METATYPE(QStringStringMap)

PVSCheckPrivileges* PVSCheckPrivileges::instance()
{
	static PVSCheckPrivileges static_instance;
	return &static_instance;
}

PVSCheckPrivileges::PVSCheckPrivileges()
{
}

PVSCheckPrivileges::~PVSCheckPrivileges()
{
}

QString PVSCheckPrivileges::getSessionReference(CachedInputContext const& sender)
{
	if(!sender.isValid())
	{
		return QString();
	}

	QString sessionReference = _savedConsoleKitSession.value(sender, QString());
	if(sessionReference.isNull())
	{
		QDBusConnection conn = QDBusConnection::systemBus();
		// Find the name of the current session:
		QDBusInterface manager("org.freedesktop.ConsoleKit", "/org/freedesktop/ConsoleKit/Manager", "org.freedesktop.ConsoleKit.Manager", conn);
		QDBusReply<QDBusObjectPath> replyGetSession = manager.call(QDBus::Block, "GetSessionForUnixProcess", (quint32)sender.pid);
		if(!replyGetSession.isValid())
		{
			qWarning("Reply to GetSessionForUnixProcess is invalid: %s: %s", replyGetSession.error().name().toLocal8Bit().constData(), replyGetSession.error().message().toLocal8Bit().constData());
			return QString();
		}
		_savedConsoleKitSession[sender] = sessionReference = replyGetSession.value().path();
	}
	return sessionReference;
}

PVSCheckPrivileges::SessionKind PVSCheckPrivileges::getSessionKind(CachedInputContext const& sender)
{
	if(!sender.isValid())
	{
		return SESSION_UNKNOWN;
	}

	// if the sender is root, we always suppose he works locally.
	if(sender.uid == 0)
	{
		return SESSION_LOCAL;
	}

	QString sessionReference = getSessionReference(sender);
	if(sessionReference.isNull())
	{
		return SESSION_LOOKUP_FAILURE;
	}

	QDBusConnection conn = QDBusConnection::systemBus();
	QDBusInterface session("org.freedesktop.ConsoleKit", sessionReference, "org.freedesktop.ConsoleKit.Session", conn);
	QDBusReply<bool> replyIsLocal = session.call(QDBus::Block, "IsLocal");

	if(!replyIsLocal.isValid())
	{
		qWarning("Unable to find out whether the current session is local: %s: %s", replyIsLocal.error().name().toLocal8Bit().constData(), replyIsLocal.error().message().toLocal8Bit().constData());
		return SESSION_LOOKUP_FAILURE;
	}
	return replyIsLocal.value() ? SESSION_LOCAL : SESSION_NONLOCAL;
}

PVSCheckPrivileges::UserPrivilege PVSCheckPrivileges::getUserPrivilege(CachedInputContext const& sender)
{
	// Always allow root:
	if(sender.uid == 0)
		return USER_PRIVILEGED;

	// For PolKit, we need the start-time of the process.
	// On Linux, we can get it from /proc:
	QString procStat = QString("/proc/%1/stat").arg(sender.pid);
	QFile procStatFile(procStat);
	if(!procStatFile.exists())
	{
		qWarning("Could not look up any info on process %d, its %s file does not exist", sender.pid, procStat.toLocal8Bit().constData());
		return USER_LOOKUP_FAILURE;
	}
	procStatFile.open(QIODevice::ReadOnly);
	QByteArray procStatBytes = procStatFile.readAll();
	qDebug() << "Read stat file: " << procStatBytes;
	QString procStatLine = QString::fromLocal8Bit(procStatBytes.constData(), procStatBytes.length());
	QStringList procStatFields = procStatLine.split(QRegExp("\\s+"));
	qDebug() << "Found stat fields: " << procStatFields;
	bool ok;
	quint64 startTime = procStatFields[21].toULongLong(&ok);
	if(!ok)
	{
		qWarning("Could not find out start time for process %d", (int)sender.pid);
		return USER_LOOKUP_FAILURE;
	}

	// Okay, we got the startTime. Now ask PolicyKit:

	QDBusConnection conn = QDBusConnection::systemBus();
	QDBusInterface intf("org.freedesktop.PolicyKit1", "/org/freedesktop/PolicyKit1/Authority", "org.freedesktop.PolicyKit1.Authority", conn);
	PolKitSubject subj;
	subj.subject_kind = "unix-process";
	subj.subject_details["pid"] = (quint32)sender.pid;
	subj.subject_details["start-time"] = startTime;
	QDBusReply<PolKitAuthReply> reply = intf.call(QDBus::Block,
			QLatin1String("CheckAuthorization"),
			QVariant::fromValue(subj),
			"org.openslx.pvs.privilegedinput",
			QVariant::fromValue(QMap<QString, QString>()) /* No details */,
			(quint32)1 /* Allow Interaction */,
			QUuid::createUuid().toString() /* Cancellation ID */);
	if(!reply.isValid())
	{
		QDBusError err = reply.error();

		qWarning("Reply to CheckAuthorization is invalid: %s: %s", err.name().toLocal8Bit().constData(), err.message().toLocal8Bit().constData());
		return USER_LOOKUP_FAILURE;
	}
	return reply.value().isAuthorized ? USER_PRIVILEGED : USER_UNPRIVILEGED;
}

QString PVSCheckPrivileges::getX11SessionName(CachedInputContext const& sender)
{
    QString sessionReference = getSessionReference(sender);
    if(sessionReference.isNull())
    {
    	return QString();
    }

	QDBusConnection conn = QDBusConnection::systemBus();
    QDBusInterface intf("org.freedesktop.ConsoleKit", sessionReference, "org.freedesktop.ConsoleKit.Session", conn);
	QDBusReply<QString> reply = intf.call(QDBus::Block, QLatin1String("GetX11Display"));
	if(!reply.isValid())
	{
		QDBusError err = reply.error();

		qWarning("Reply to GetX11Display is invalid: %s: %s", err.name().toLocal8Bit().constData(), err.message().toLocal8Bit().constData());
		return QString();
	}

	return reply.value();
}

QString PVSCheckPrivileges::getX11DisplayDevice(CachedInputContext const& sender)
{
	QString sessionReference = getSessionReference(sender);
	if(sessionReference.isNull())
	{
		return QString();
	}

	QDBusConnection conn = QDBusConnection::systemBus();
	QDBusInterface intf("org.freedesktop.ConsoleKit", sessionReference, "org.freedesktop.ConsoleKit.Session", conn);
	QDBusReply<QString> reply = intf.call(QDBus::Block, QLatin1String("GetX11DisplayDevice"));
	if(!reply.isValid())
	{
		QDBusError err = reply.error();

		qWarning("Reply to GetX11DisplayDevice is invalid: %s: %s", err.name().toLocal8Bit().constData(), err.message().toLocal8Bit().constData());
		return QString();
	}

	return reply.value();
}

bool PVSCheckPrivileges::require(SessionKind sessionKind, CachedInputContext const& sender)
{
	SessionKind cachedSessionKind;

	if(sessionKind < SESSION_NONLOCAL)
	{
		if((cachedSessionKind = _savedSessionKind.value(sender, SESSION_UNKNOWN)) == SESSION_UNKNOWN)
		{
			cachedSessionKind = getSessionKind(sender);
			if(cachedSessionKind != SESSION_LOOKUP_FAILURE)
				_savedSessionKind[sender] = cachedSessionKind;
			qDebug("Got session kind: %s", toString(cachedSessionKind).toLocal8Bit().constData());
		}
		if(cachedSessionKind > sessionKind)
			return false;
	}

	return true;
}

bool PVSCheckPrivileges::require(UserPrivilege userPrivilege, CachedInputContext const& sender)
{
	UserPrivilege cachedUserPrivilege;

	if(userPrivilege < USER_UNPRIVILEGED)
	{
		if((cachedUserPrivilege = _savedUserPrivilege.value(sender, USER_UNKNOWN)) == USER_UNKNOWN)
		{
			cachedUserPrivilege = getUserPrivilege(sender);
			if(cachedUserPrivilege != USER_LOOKUP_FAILURE)
				_savedUserPrivilege[sender] = cachedUserPrivilege;
			qDebug("Got user privilege: %s", toString(cachedUserPrivilege).toLocal8Bit().constData());
		}
		if(cachedUserPrivilege > userPrivilege)
			return false;
	}
	return true;
}

bool PVSCheckPrivileges::require(SessionKind sessionKind,
		UserPrivilege userPrivilege,
		CachedInputContext const& sender)
{
	if(!require(sessionKind, sender))
		return false;
	if(!require(userPrivilege, sender))
		return false;
	return true;
}

uint qHash(CachedInputContext const& p)
{
	return qHash(qMakePair(p.pid, qMakePair(p.uid, p.gid)));
}