<?
	/*Author: Nitesh Dhanjani [ email: nitesh at dhanjani dot com]

	This PHP script acts as a simple web-proxy server. It allows for POST
	requests to be intercepted and altered.

	At this time, this program does not support HTTPS, but support for this
	can be added by handling HTTP CONNECT requests. It is not multi-threaded.

	NOTE: If you get an error about undefined socket functions, your PHP
		installation probably does not have support for PHP's latest
		socket API. You will need to recompile your PHP
		installation by running ./configure with the
		--enable-sockets flag.

	PHP >= 4.1.0 required
	*/


	/* port to listen on */
	$port=8000;

	/*favorite editor - give full path if not in $PATH*/
	$editor = "vi";

	/* create socket*/
	$socket=socket_create(AF_INET, SOCK_STREAM, 0);

	/* bind socket to port*/
	socket_bind($socket, "127.0.0.1", $port) or die ('Cannot bind');

	/* begin listening */
	socket_listen($socket);

	print "Configure your browser's proxy setting to point to 127.0.0.1 port $port\n\n";
	flush();

	/*while loop - keep accepting incoming connections*/	
	while (true)
	{
		/* accept request*/
		$incoming = socket_accept($socket);	
	
		$data = "";

		$checkonce=1;

		$ispost=0;
		
		/*this loop is stores the browser request (GET or POST) into $data*/
		while(($incoming_data = socket_read($incoming, 2048))!=false)
		{

			/*append $data with $incoming_data at every iteration*/
			$data .= $incoming_data;
		
			/*check if request is POST. No need to do this more than once*/	
			if($checkonce)
			{
				if(strtolower(substr($data,0,4))=="post")
					$ispost=1;

				$checkonce=0;
			}

			
			$pos=strpos($data,"\r\n\r\n");

			/*if there is \r\n\r\n in $data*/
			if($pos!=false)
			{
				/*if this isn't a POST request, then the browser is done sending the request*/
				if($ispost==0)
				{
					break;
				}

				/*otherwise, the data section of the POST request will follow after \r\n\r\n*/
				else
				{
					/* find value of Content-Length: */
					list($pre_length,$rest_header)=explode("Content-Length: ",$data,2);
					list($content_length,$remaining)=explode("\r\n",$rest_header,2);
					
					if(is_numeric($content_length)==true)
					{

						list($header,$rest)=explode("\r\n\r\n",$data);

						/*remaining length of data to be read is the difference
						between the value of Content-Length and the amount of
						data that has already been read after \r\n\r\n*/
					       	$remaining_n=$content_length-strlen($rest);

	
						if($remaining_n>=0)
						{
							$incoming_data=socket_read($incoming,$remaining_n);
							$data.=$incoming_data;
							
							break;
						}
					}
				}
			}
		}

		/*create temporary file in /tmp and write contents of incoming data to it*/
		$filename = "/tmp/proxy_".rand();

		$file_handle = fopen ($filename,"w");

		if(!$file_handle)
			die ("Unable to create $filename for writing.");

		fputs($file_handle,$data);

		fclose($file_handle);

		
		/* get value of URL submitted by browser into the $url variable*/
		list($request,$url,$http)=explode(" ",$data,3);
	
		/*open in editor only if the request is POST*/
		/*NOTE: Remove the if condition if you want to intercept GET requests also*/
		if($ispost==1)
		{
				passthru ("$editor $filename > /dev/tty < /dev/tty");
		}
		

		/*after the user is done editing the request, re-read the temporary file*/
		$file_handle = fopen ($filename,"r");
	
		if(!$file_handle)
        		die ("Unable to open $filename for reading.");

		$data="";

		/*store data in file into $data*/
		do
		{
			$databuf = fread($file_handle,4096);
		
			if(strlen($databuf)==0)
				break;

			$data .= $databuf;

		}while (true);

		fclose($file_handle);

		/*remove temp file*/
		unlink($filename);

		/*get the request(GET or POST), the target url, and the rest of the request*/
		list($request,$url,$rest_header)=explode(" ",$data,3);


		/*replace HTTP/1.x with HTTP/1.0. This way we can avoid the Keep-Alive requests*/
		list($http_ver,$rest_rest_header)=explode("\r\n",$rest_header,2);
		$rest_header="HTTP/1.0\r\n".$rest_rest_header;

		print "\n\nURL: $url\n";
		flush();

		/*$url should contain the string http://x so it should be greater than 7 in length*/
		if(strlen($url)<=7)
		{
			print "Unknown request from web browser.\n";
			flush();
			close($incoming);
			continue;
		}

		/*change $url to $host, ie strip everything after the /*/
		list($host,$rest)=explode("/",substr($url,7),2);	

		/*is this a POST request?*/
		if($ispost)
		{
			/*re-calculate length from data obtained in temporary file*/
			list($realheader,$realdata)=explode("\r\n\r\n",$data,2);

			list($pre_length,$rest_header)=explode("Content-Length: ",$rest_header,2);
			
			list($actual_length,$rest_rest_header)=explode("\r\n",$rest_header,2);

				$rest=" /".$rest." ".$pre_length."Content-Length: ".(strlen($realdata))."\r\n".$rest_rest_header;
	
			$data=$request.$rest;
		}
			
		else
			$data=$request." /".$rest." ".$rest_header;


		/*connect to target host*/
		print "Connectiong to $host..";
		flush();

		$fsocket=fsockopen($host,80);
		if(!$fsocket)
		{
			print "Could not connect to $host\n";
			flush();
			close($incoming);
			continue;

		}

		print "Connected!..Writing request...";
		flush();

		/*Remove Proxy-Connection: line*/
		list($pre,$proxy_connection)=explode("Proxy-Connection: ",$data,2);
		list($until_eol,$rest)=explode("\r\n",$proxy_connection,2);
		$data=$pre.$rest;

		/*write outgoing request*/
		fwrite($fsocket,$data,strlen($data));

		$response="";

		print "Reading Response...";
		flush();

		/*read response from server*/

		while (!feof($fsocket))
		{
			$response_buf=fread($fsocket,1024);
			$response.=$response_buf;

		}
		fclose($fsocket);

		/*send resposne from server to the browser*/
		socket_write($incoming,$response,strlen($response));

		/*ok we are done here, close browser connection*/
		socket_close($incoming);	
		print "Done serving $url\n";
		flush();

	}
?>