// Cyphesis Online RPG Server and AI Engine
// Copyright (C) 2000-2004 Alistair Riddoch
//
// 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 2 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, write to the Free Software Foundation,
// Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA

// $Id: system.cpp,v 1.31 2007-12-06 23:50:14 alriddoch Exp $

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include "system.h"

#include "log.h"
#include "debug.h"
#include "globals.h"
#include "compose.hpp"

#include <wfmath/MersenneTwister.h>

#include <gcrypt.h>

#include <cassert>

#include <iostream>

extern "C" {
#ifdef HAVE_SYS_UTSNAME_H
    #include <sys/utsname.h>
#endif // HAVE_SYS_UTSNAME_H
    #include <sys/types.h>
#ifdef HAVE_WINSOCK_H
    #undef DATADIR
    #include <winsock.h>
#endif // HAVE_WINSOCK_H
#ifdef HAVE_SYS_WAIT_H
    #include <sys/wait.h>
#endif // HAVE_SYS_WAIT_H
    #include <signal.h>
    #include <fcntl.h>
    #include <unistd.h>
    #include <stdio.h>
}

static const bool debug_flag = false;

const std::string get_hostname()
{
#ifndef HAVE_UNAME
    char hostname_buf[256];

    if (gethostname(hostname_buf, 256) != 0) {
        return "UNKNOWN";
    }
    return std::string(hostname_buf);
#else // HAVE_UNAME
    struct utsname host_ident;
    if (uname(&host_ident) != 0) {
        return "UNKNOWN";
    }
    return std::string(host_ident.nodename);
#endif // HAVE_UNAME
}

unsigned int security_check()
{
#ifdef HAVE_GETUID
    if (getuid() == 0 || geteuid() == 0) {
        log(CYLOG_ERROR, "Running cyphesis as the superuser is dangerous.");
        return 0;
    }
#endif // HAVE_GETUID
    return SECURITY_OKAY;
}

void reduce_priority(int p)
{
#ifdef HAVE_NICE
    if (nice(p) < 0) {
        log(ERROR, "Unable to increase nice level to reduce priority");
    }
#endif // HAVE_NICE
}

extern "C" void shutdown_on_signal(int signo)
{
    exit_flag = true;

#if defined(HAVE_SIGACTION)
    struct sigaction action;
    sigemptyset(&action.sa_mask);
    action.sa_flags = 0;
    action.sa_handler = SIG_IGN;
    sigaction(signo, &action, NULL);
#else
    signal(signo, SIG_IGN);
#endif
}

extern "C" void report_segfault(int signo)
{
    log(CRITICAL, "Segmentation fault");
    log(NOTICE, "Please report this bug to alriddoch@zepler.org");

#if !defined(HAVE_SIGACTION)
    signal(signo, SIG_DFL);
#endif
}

extern "C" void report_abort(int signo)
{
    log(CRITICAL, "Aborted");
    log(NOTICE, "Please report this bug to alriddoch@zepler.org");

#if !defined(HAVE_SIGACTION)
    signal(signo, SIG_DFL);
#endif
}

extern "C" void report_status(int signo)
{
    if (exit_flag) {
        log(NOTICE, "Shutting down");
    } else {
        log(NOTICE, "Running");
    }
}

extern "C" void rotate_logs(int signo)
{
    rotateLogger();
}

void interactive_signals()
{
#if defined(HAVE_SIGACTION)
    struct sigaction action;

    sigemptyset(&action.sa_mask);
    action.sa_flags = 0;
    action.sa_handler = shutdown_on_signal;
    sigaction(SIGINT, &action, NULL);

    sigemptyset(&action.sa_mask);
    action.sa_flags = 0;
    action.sa_handler = shutdown_on_signal;
    sigaction(SIGTERM, &action, NULL);

    sigemptyset(&action.sa_mask);
    action.sa_flags = 0;
    action.sa_handler = shutdown_on_signal;
    sigaction(SIGQUIT, &action, NULL);

    sigemptyset(&action.sa_mask);
    action.sa_flags = 0;
    action.sa_handler = shutdown_on_signal;
    sigaction(SIGHUP, &action, NULL);

    sigemptyset(&action.sa_mask);
    action.sa_flags = 0;
    action.sa_handler = SIG_IGN;
    sigaction(SIGPIPE, &action, NULL);

    sigemptyset(&action.sa_mask);
    action.sa_flags = SA_RESETHAND;
    action.sa_handler = report_segfault;
    sigaction(SIGSEGV, &action, NULL);

    sigemptyset(&action.sa_mask);
    action.sa_flags = SA_RESETHAND;
    action.sa_handler = report_abort;
    sigaction(SIGABRT, &action, NULL);

#ifdef __APPLE__
#warning Apple
    sigemptyset(&action.sa_mask);
    action.sa_flags = 0;
    action.sa_handler = report_status;
    sigaction(SIGINFO, &action, NULL);
#endif // __APPLE__

#else // defined(HAVE_SIGACTION)
    signal(SIGINT, shutdown_on_signal);
    signal(SIGTERM, shutdown_on_signal);
#ifndef _WIN32
    signal(SIGQUIT, shutdown_on_signal);
    signal(SIGHUP, shutdown_on_signal);
    signal(SIGPIPE, SIG_IGN);
#endif // _WIN32
    signal(SIGSEGV, report_segfault);
    signal(SIGABRT, report_abort);
#endif // defined(HAVE_SIGACTION)
}

void daemon_signals()
{
#if defined(HAVE_SIGACTION)
    struct sigaction action;

    sigemptyset(&action.sa_mask);
    action.sa_flags = 0;
    action.sa_handler = SIG_IGN;
    sigaction(SIGINT, &action, NULL);

    sigemptyset(&action.sa_mask);
    action.sa_flags = 0;
    action.sa_handler = shutdown_on_signal;
    sigaction(SIGTERM, &action, NULL);

    sigemptyset(&action.sa_mask);
    action.sa_flags = 0;
    action.sa_handler = SIG_IGN;
    sigaction(SIGQUIT, &action, NULL);

    sigemptyset(&action.sa_mask);
    action.sa_flags = 0;
    action.sa_handler = rotate_logs;
    sigaction(SIGHUP, &action, NULL);

    sigemptyset(&action.sa_mask);
    action.sa_flags = 0;
    action.sa_handler = SIG_IGN;
    sigaction(SIGPIPE, &action, NULL);

    sigemptyset(&action.sa_mask);
    action.sa_flags = SA_RESETHAND;
    action.sa_handler = report_segfault;
    sigaction(SIGSEGV, &action, NULL);

    sigemptyset(&action.sa_mask);
    action.sa_flags = SA_RESETHAND;
    action.sa_handler = report_abort;
    sigaction(SIGABRT, &action, NULL);
#else
    signal(SIGINT, SIG_IGN);
    signal(SIGTERM, shutdown_on_signal);
#ifndef _WIN32
    signal(SIGQUIT, SIG_IGN);
    signal(SIGHUP, rotate_logs);
    signal(SIGPIPE, SIG_IGN);
#endif // _WIN32
    signal(SIGSEGV, report_segfault);
    signal(SIGABRT, report_abort);
#endif
}

int daemonise()
{
#ifdef HAVE_FORK
    int pid = fork();
    int new_stdio;
    int status = 0;
    int running = false;

    switch (pid) {
        case 0:
            // Child
            // Get rid of controlling tty, and start new session
            setsid();
            // Switch signal behavoir
            daemon_signals();
            // Change current working directory to /
            if (chdir("/") != 0) {
                log(ERROR, "Unable to change current working directory to /");
            }
            // Get rid if stdio
            close(STDIN_FILENO);
            close(STDOUT_FILENO);
            close(STDERR_FILENO);
            // Open /dev/null on the stdio file descriptors to avoid problems
            new_stdio = open("/dev/null", O_RDWR);
            dup2(new_stdio, STDIN_FILENO);
            dup2(new_stdio, STDOUT_FILENO);
            dup2(new_stdio, STDERR_FILENO);
            break;
        case -1:
            // Error

            // We are not the daemon process
            daemon_flag = false;

            log(ERROR, "Failed to fork() to go to the background.");

            break;
        default:
            // Parent

            // We are not the daemon process
            daemon_flag = false;

            // Install handler for SIGUSR1
#if defined(HAVE_SIGACTION)
            struct sigaction action;
            sigemptyset(&action.sa_mask);
            action.sa_flags = 0;
            action.sa_handler = shutdown_on_signal;
            sigaction(SIGUSR1, &action, NULL);
#else
            signal(SIGUSR1, shutdown_on_signal);
#endif

            if (wait4(pid, &status, 0, NULL) < 0) {
                running = true;
            } else {
                pid = -1;
            }

            if (running == true) {
                log(INFO, "Running");
            } else {
                int estatus = WEXITSTATUS(status);
                if (estatus == EXIT_SUCCESS) {
                    log(ERROR, "Cyphesis exited normally at initialisation.");
                } else if (estatus == EXIT_DATABASE_ERROR) {
                    log(ERROR, "Cyphesis was unable to connect to the database.");
                } else if (estatus == EXIT_SOCKET_ERROR) {
                    log(ERROR, "Cyphesis was unable to open a listen socket.");
                } else if (estatus == EXIT_PORT_ERROR) {
                    log(ERROR, "Could not find free client listen socket. "
                               "Init failed.");
                    log(INFO, String::compose("To allocate 8 more ports please"
                                              " run:\n\n    cyconfig "
                                              "--cyphesis:dynamic_port_end=%1"
                                              "\n\n", dynamic_port_end + 8));
                } else {
                    log(ERROR, "Cyphesis exited unexpectedly at initialisation.");
                }
                log(ERROR, "See syslog for details.");
            }

            break;
    }
    return pid;
#else // HAVE_FORK
    // On systems where we can't fork, fool the original process into thinking
    // it is now the child.
    return 0;
#endif // HAVE_FORK
}

void running()
{
#ifdef HAVE_FORK
    if (daemon_flag) {
        kill(getppid(), SIGUSR1);
    }
#endif // HAVE_FORK
}

static const char hex_table[16] = { '0', '1', '2', '3', '4', '5', '6', '7',
                                    '8', '9', 'A', 'B', 'C', 'D', 'E', 'F' };

static const int hash_algorithm = GCRY_MD_MD5;
static const int hash_salt_size = 8;

void hash_password(const std::string & pwd, const std::string & salt,
                   std::string & hash)
{
    unsigned int digest_length = gcry_md_get_algo_dlen(hash_algorithm);
    unsigned char * buf = new unsigned char[digest_length];
    assert(buf != 0);

    std::string passwd_and_salt = pwd + salt;

    // Generate an MD% hash of the password and salt concatenated
    gcry_md_hash_buffer(hash_algorithm, buf,
                        (const unsigned char *)passwd_and_salt.c_str(),
                        passwd_and_salt.size());
    // Build a string containing the salt and hash together
    // hash = String::compose("$1$%1$", salt);
    if (!salt.empty()) {
        hash = "$1$";
        hash += salt;
        hash += "$";
    } else {
        hash.clear();
    }
    for(unsigned int i = 0; i < digest_length; ++i) {
        hash.push_back(hex_table[buf[i] & 0xf]);
        hash.push_back(hex_table[(buf[i] & 0xf0) >> 4]);
    }
    return;
}

void encrypt_password(const std::string & pwd, std::string & hash)
{
    std::string salt;
    WFMath::MTRand rng;

    // Generate 8 bytes of salt
    for (int i = 0; i < hash_salt_size; ++i) {
        unsigned char b = rng.randInt() & 0xff;
        salt.push_back(hex_table[b & 0xf]);
        salt.push_back(hex_table[(b & 0xf0) >> 4]);
    }

    // Get a hash of password and salt
    hash_password(pwd, salt, hash);
}

int check_password(const std::string & pwd, const std::string & hash)
{
    unsigned int digest_length = gcry_md_get_algo_dlen(hash_algorithm);
    std::string new_hash;
    size_t hash_size = hash.size();

    if (hash_size < (digest_length * 2 + 5) || hash.substr(0, 3) != "$1$") {
        // Get a hash of password with no salt
        hash_password(pwd, "", new_hash);
    } else {
        // Extract the salt from the hash string
        size_t dp = hash.find('$', 3);
        if (dp == std::string::npos) {
            log(CYLOG_ERROR, "Password hash has no $ symbol after the salt.");
            return -1;
        }
        assert(dp > 3);
        std::string salt = hash.substr(3, dp - 3);
        // Get a has of password and salt
        hash_password(pwd, salt, new_hash);
    }
    // Check if the generated hash matches the reference hash
    return hash == new_hash ? 0 : -1;
}

#ifndef HAVE_GETTIMEOFDAY

int gettimeofday(struct timeval * tv, struct timezone * tz)
{
    assert(tz == 0);

    SYSTEMTIME localtime;
    struct tm unix_time;

    GetLocalTime(&localtime);

    unix_time.tm_sec = localtime.wSecond;
    unix_time.tm_min = localtime.wMinute;
    unix_time.tm_hour = localtime.wHour;
    unix_time.tm_mday = localtime.wDay;
    unix_time.tm_mon = localtime.wMonth - 1;
    unix_time.tm_year = localtime.wYear - 1900;

    tv->tv_usec = localtime.wMilliseconds * 1000;

    tv->tv_sec = mktime(&unix_time);

    return 0;
}

#endif