/*
 *      shttpd.cpp
 *      Simple HTTP Server
 *      Copyright 2009 Marcin Biernacki <phisikus@platinum.linux.pl>
 *      
 *      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.
 */

/*
 * 
 *  Include what we need: network stuff, string...
 * 
 */

#include <iostream> /* clear */
#include <cstdlib>
#include <sys/types.h>
#include <sys/stat.h> // to use umask function....
#include <syslog.h> /* syslog logging.... */ 
#include <string.h>
#include <fstream>
#include <sys/socket.h>         /* bind(), listen(), accept()      */
#include <sys/wait.h>           /* waitpid()                       */
#include <unistd.h>             /* fork()                          */
#include <signal.h>             /* signal()                        */
#include <arpa/inet.h>
#include <string>
#include <sys/select.h>
using namespace std;

/*
 *  Configuration variables
 * 
 */
#define VERSION 0.1
#define AUTHOR "Marcin Biernacki"
#define banner "shttpd 0.1 (Unix)"
string root_dir="/home/shttpd/public_html/";
int port=7777;
int max_conn=100;


/*
 * 
 *  Other variables
 * 
 */
int sock;
int sock_client;
int size_of_saddr;
struct sockaddr_in saddr,client_addr;
int error_fork;

// INFO
string message; 
string *http_variables; // variables from client
string *http_values; // values from client
string http_host; // result of "Host:"
string proto;	// protocol info
string user_agent; // User-Agent: ...
int no_variables; // number of variables

/*
 * Our functions
 * 
 */
bool make_daemon(); // makes that program a daemon
void sigchld(int not_used); 
void sigterm(int not_used);
void sigusrone(int not_used);
void sigkill(int not_used);
int main();
int talk(); // communication with client
bool security(string &to_check); // check if there are any harmful characters
bool http_head_get(string &adres,string &question,string &virtualhost); // GET+HEAD request support
 

/*
 *  make me a daemon!
 */
bool make_daemon()
{
		pid_t child,sid_of_child; /* process id of Child */
	        child = fork(); // Create new process.
	
        if (child < 0) { syslog(LOG_ERR,"could not create daemon process. PID=%d",getpid()); return false; };
        if (child > 0)
	{ 
		// Success!
		syslog(LOG_INFO,"daemon process created. PID=%d",getpid());
		exit(EXIT_SUCCESS);
		// end of parent process....
	};
		/*
		 * making process independent.
		 */
        umask(0);
        sid_of_child = setsid();
        if (sid_of_child < 0) {
         syslog(LOG_ERR,"setsid() failed in phttpd daemon. PID=%d",getpid());
         return false;
        };
        if(chdir(root_dir.c_str())){ syslog(LOG_ERR,"chdir() failure. Can't change directory to root_dir");
	 	exit(EXIT_FAILURE); };
	    close(STDERR_FILENO);
        close(STDIN_FILENO);
        close(STDOUT_FILENO); // close file descriptors.
      	signal(SIGCHLD, sigchld); //to check `zombie processes`
		signal(SIGKILL, sigkill);
		signal(SIGTERM, sigterm);
		signal(SIGUSR1, sigusrone); 
		return true;

};

/*
 * The most important - HTTP talk
 *
 */
int talk()
{
	/*
	 *  Get first part of request (GET | HEAD)
	 */
	cin >> message;
	security(message); 
	if((message=="GET")||(message=="HEAD"))
	{
		/*
		 * Get location, check corectness.
		 */
		string request=message; // copy request name (GET | HEAD)
		cin >> message; // read location
		cin >> proto; // get protocol info
		if(!security(message)) return false; 
		/*
	 	*  Get information from client
	 	*  
	 	*/
	 	char info[100],info2[100];
	 	cin.ignore(1,'\n');
	 	while(true)
	 	{
	 		cin.get(info,98,' ');
	 		cin.ignore(1,' ');
	 		cin.get(info2,98);
	 		/*
			 *  get useful information from client
			 *
			 */
	 		if(!strcmp(info,"Host:"))http_host=info2;
	 		if(!strcmp(info,"User-Agent:"))user_agent=info2;
	 		cin.ignore(1,'\n');
	 		
	 		if((cin.peek()==10)||(cin.peek()==13))break;
	 		
		};
		
	 	
		/*
		 * Show the file
		 */
		http_head_get(message,request,http_host);
	};

	return true;
};

/*
 *  Security input analyzer
 * 
 */
bool security(string &to_check)
{
	// check length (414 error?)
	if(to_check.length()>254)
	{
		cout << "HTTP/1.1 414 Request Too Long" << endl;
		cout << "Server: " << banner << endl;
		cout << "Connection: close" << endl;
		cout << "Content-Type: text/html" << endl;
		cout << "\n<h1>414 Error</h1><p>Your browser sent too long request.</p>" << endl;
		cout << endl;
		return false;
	};
		// check if there are any "/../" constructions.
		// prevents changing workdir
		for(int i=0;i<=(signed int)to_check.length();i++)
		{
			
			if((i>=1)&&(to_check[i]=='.')&&(to_check[i-1]=='.'))
			{
			cout << "HTTP/1.1 400 Bad request" << endl;
			cout << "Server: " << banner << endl;
			cout << "Connection: close" << endl;
			cout << "Content-Type: text/html" << endl;
			cout << endl;
			cout << "<h1>400 Error</h1><p>Invalid request.</p>" << endl;
			cout << endl;
			return false;
			}
		};
	
	return true;
};

/*
 * HTTP GET REQUEST
 */

bool http_head_get(string &adres,string &question,string &virtualhost)
{
	/*
	 * Get information from request
	 */
	string extension,filename;
	
	
	// "/" rootdir?
	if(adres.length()==1)
	{
		filename="index.html";
		extension="html";
		filename=root_dir+filename;
	}else
	{
		/*
		 * Get extension, number of variables, some pointers
		 */
		int qs_point=0; // adres of "?"
		int coma=0; // begining of extension
		no_variables=0; // number of http variables
		
		for(int i=0;i<=(signed int)adres.length();i++)
		{
			if(adres[i]=='?')qs_point=i;
			if((!no_variables)&&(adres[i]=='.'))coma=i;
			if(adres[i]=='&')no_variables++;
			
		};
		if(!qs_point)qs_point=(adres.length()+1);; // in case of no "?" sign

		/*
		 * Set filename and extension
		 */
		for(int i=(coma+1);i<qs_point;i++)extension=extension+adres[i];
		for(int i=1;i<qs_point;i++)filename=filename+adres[i];
		filename=root_dir+filename; // absolute path
		
		/*
		 *  Get the variables
		 */
		if(qs_point!=(signed int)adres.length())
		{
			
			http_variables = new string[no_variables+1];
			http_values = new string[no_variables+1];
			int nuof=0;
			bool switcher=false; // false - variable ; true - value
			for(int i=(qs_point+1);i<=(signed int)adres.length();i++)
			{
				if(adres[i]=='&'){ nuof++; switcher=(switcher ? false : true);;continue; };
				if(adres[i]=='='){ switcher=(switcher ? false : true);;continue; };
				if(switcher) http_values[nuof]+=adres[i];
					else  http_variables[nuof]+=adres[i];
			};
				
				
		};
		
		
	};
	/*
	 *  The most important - sending file.
	 */	
	ifstream plik(filename.c_str(),ios::binary);
	if(!plik) {
		cout << "HTTP/1.1 404 Not Found" << endl;
		cout << "Server: " << banner << endl;
		cout << "Connection: close" << endl;
		cout << "Content-Type: text/html" << endl;
		cout << endl;
		cout << "<h1>404 Error</h1><p>File that you are looking for is not avaliable.</p>" << endl;
		cout << endl;
		return false; };
		cout << "HTTP/1.1 200 OK" << endl;
		cout << "Server: " << banner << endl;
		cout << "Connection: close" << endl;
		/*
		 * Checking Content-Type using "file"
		 */
		string arguments = "`which file` --mime-type -b "+filename;
		char mime_type[100];
		FILE *file_program = popen(arguments.c_str(), "r");
		fgets(mime_type,50,file_program);
		cout << "Content-Type: " << mime_type << endl;
		pclose(file_program);
	if(question!="GET") return true;	
	/*
	 *  Send file!
	 */
	char znak;
	while(!plik.eof())
	{
		plik.read(&znak,1);
		cout << znak;
	};
	plik.close();
	return true;
};



/*
 *  Signals? No problem.
 * 
 */
void sigchld(int not_used)
{
    int p_id;
    while((p_id = waitpid (-1, NULL, WNOHANG)) > 0);
};

void sigkill(int not_used)
{	
		syslog(LOG_ERR,"daemon terminated using SIGKILL, PID=%d",getpid());
		exit(EXIT_SUCCESS);
};


void sigterm(int not_used)
{
	syslog(LOG_ERR,"daemon terminated using SIGTERM, PID=%d",getpid());
	exit(EXIT_SUCCESS);
};

void sigusrone(int not_used)
{
};	



/*
 *  Let's do it!
 *  main function.
 */

int main()
{
	/*
	 * Show welcome banner
	 */
	cout << "shttpd " << VERSION << " [build: " << __DATE__ << " " << __TIME__ << "]";
	cout << " (" << AUTHOR << ")" << endl;
	/*
	 * become a daemon
	 */
	if(!make_daemon()){syslog(LOG_ERR,"make_daemon() failed! Exiting.");exit(EXIT_FAILURE);};
	// We are independent here.
	
	
	/*
 	 *	Prepare network socket
 	 */
	sock=socket(PF_INET, SOCK_STREAM, 0);
	if(sock<0) {syslog(LOG_ERR,"socket() failed!");exit(EXIT_FAILURE);}
	saddr.sin_family=PF_INET;
	saddr.sin_port=htons(port);
	saddr.sin_addr.s_addr=INADDR_ANY;
	/*
	 * Bind, Listen
	 */
	if (bind(sock,(struct sockaddr *)&saddr,sizeof(saddr))) {syslog(LOG_ERR,"bind() on port %d failed!",port); exit(EXIT_FAILURE);};
	if (listen (sock,max_conn)) {syslog(LOG_ERR,"listen() failed!"); exit(EXIT_FAILURE);};
	
	
	/*
	 * Main part
	 */
	while(true) // will work forever
	{
		/*
		 * Accept new connection
		 */
		size_of_saddr = sizeof(saddr);
		sock_client = accept(sock, (struct sockaddr *)&client_addr,(socklen_t *) &size_of_saddr);
		syslog(LOG_NOTICE,"new connection accepted : %s",inet_ntoa (client_addr.sin_addr));
		/*
		 * Create new process for connection
		 */
		if((error_fork=fork())==0)
		{	
				dup2 (sock_client, 0);
            	dup2 (sock_client, 1);   // close socket, but set as new STDIN,STDOUT,STDERR
            	dup2 (sock_client, 2);
            	/*
            	 * Let's talk with client ;-)
            	 */           	
            	exit(talk()); 
            	
		};
		close(sock_client);		

		
		
	};
	
	exit(EXIT_SUCCESS);

	
};