I want a way to allow users to go through my http proxy server (Squid, Privoxy, etc.) without having to type the IP/port in web browser settings. I was hoping I could use a simple web interface.
I'm envisioning this:
User goes to a website on my server (http://proxy.com) and types a URL
into the form.
The user's browser URL looks like (http://proxy.com/url=URL)
All connections to any future links are passed through my http proxy
running on a different port.
And I do NOT want to use existing php/cgi web proxy scripts.
My only reasoning for that is I feel it would be much more efficient re-routing connections through a native proxy server than having many php instances proxy the connections. Please tell me if you think this would not actually be the case.
Are there any simple ways of doing this? Thanks!
You may want to setup a transparent proxy. That way the clients do not know they are using a proxy so they do not have to set the proxy IP in their browsers. This obviously does not work for https. Some information for squid here: http://www.cyberciti.biz/tips/linux-setup-transparent-proxy-squid-howto.html
Related
I'm creating a website which needs do some data gathering anonymously. I ran an Ubuntu server with Apache, and normally when I want to run my script, target websites and servers can determine my server real IP. Is there any solution to hide Apache server IP and use random IPs per each request?
The target website will generally always be able to see your real IP address; you'd have to make each request from a different server, or via a different network connection.
Depending on why and how you're doing this, from where and to whom, it's likely to be an effective way to get banned, sued and/or prosecuted for a DDoS attack (or some other kind of attack).
Please don't do this.
I've been reading this book about PHP and MySQL and at the end of each chapter it asks you some questions for you to research about and one of them I don't really get:
What is a Proxy script? When might a proxy script be necessary?
I hope you could help me answering this question because I don't really know what it is (I do know what a proxy server is though)
From WikiPedia's article on Proxy Servers
In computer networks, a proxy server is a server (a computer system or
an application) that acts as an intermediary for requests from clients
seeking resources from other servers. A client connects to the proxy
server, requesting some service, such as a file, connection, web page,
or other resource available from a different server and the proxy
server evaluates the request as a way to simplify and control its
complexity.
That explains it pretty much. So basically, a PHP proxy script can be used to access the blocked content i.e. websites in a network i.e. a college's WiFi network.
For an example, suppose facebook.com is blocked by your college's WiFi and you want to access it then a PHP proxy script might come in handy. Which will take requests from you and send it to the facebook on your behalf and sends the received data back to you. So you're not directly communicating with the facebook's server but that proxy script is doing that job for you.
Here's a simple PHP proxy script I found from a quick search that you might find helpful : Simple-php-proxy-script
How to change ip address such that it does not reveal our original address when using $_SERVER['REMOTE_ADDR']; in php
You need to use a proxy server if you're trying to access a website from a different IP than your own. Wikipedia has more information.
There are several options I have in mind for this. I will go from the simpler to the more complicated one.
First, you could use a proxy server and ask him through an HTTP request made by your program or your browser, to fetch a resource for you. The proxy server will take the role of querying a resource in your place to the target service.
Example :
You want to retrieve the main page of the domain stackoverflow.com. You ask the proxy server to ask stackoverflow's HTTP server to send him the main page and he will forward it back to you.
To SO webserver, the superglobal $_SERVER['REMOTE_ADDR'] variable will correspond to the proxy server's IP address and not yours. However, the HTTP protocol implements some fields such as HTTP_VIA, HTTP_X_FORWARDED_FOR, or HTTP_FORWARDED which can be used to know if the current HTTP request is made by a proxy or not.
A transparent proxy will not specify those fields and will not modify your request whereas a non-transparent proxy may reveal the original IP address of the original requester. You got to use a reliable proxy which will act as you intends it to act. Another thing to consider is the use of an SSL tunnel between you and the proxy to avoid eavesdropping.
The second solution is to use a VPN (Virtual private network) server. It would be too complicated to fully explains how this works, but remember this, when you are connected to a computer using a VPN service (like l2tpd, pptpd ...) it's like you were on the same LAN with this computer. So you can transparently make requests to a webserver and he will never find out what's your real IP address.
A third solution could be to use linked nodes based network such as TOR. It's a free network you can connect to, and you will be completely anonymous to regular people. The TOR network power is to provide a network of many nodes and each nodes doesn't know anything about other nodes, so even people connected to the TOR network cannot know anything about you. I suggest you to read more about this if you're interested.
There are more complicated other solutions such as TCP session hijacking which is generally used to fake IP addresses and literally steal another computer's TCP connection, but this is out of the scope of this answer.
Is it possible to fake or hijack a content of $_SERVER['REMOTE_ADDR'] variable?
I would like to fake a request with:
$_SERVER['REMOTE_ADDR']='127.0.0.1';
How could I do that with PHP? Can CURL do that somehow?
I assume that you mean faking it remotely. The short answer is yes you can. The long answer about how easy it is depends on how you want to fake it.
If you don't care about receiving a response, it's as trivial as opening a raw socket to the destination and forging the source IP address. I'm not sure if it's really easy to do in PHP since all of PHP's socket implementations are at or above the TCP level. But I'm sure it's possible. Now, since you're not in control of the network, the response will not go back to you. So that means that you cannot (reliably anyway) create a TCP connection via a trivial forged TCP header (since the syn-ack does prevent this by requiring two-way communication).
However, if you can compromise the gateway the IP is off of, you can do whatever you'd like. So if you compromise the wifi router a computer is connected to, you can pretend to be that computer, and the server won't tell the difference. If you compromise the ISP's outbound router, you can (in theory at least) pretend to be the computer and the server won't tell the difference.
For some more info, see these following links:
ServerFault Question
Symantec Article
Linux Security Article
However, you will only be able to forge the 127.0.0.1 loopback address under TCP if you actually compromise the local machine/server. And at that point does it really matter?
Important
If you're using a framework to access this information, be absolutely sure that it does not check the X-HTTP-FORWARDED-FOR header! Otherwise it's trivial to fake the IP address. For example, if you're using Zend Framework's Zend_Controller_Request_Http::getClientIp method, be absolutely sure that you pass false as the parameter! Otherwise someone just needs to send an HTTP header: X-Http-Forwarded-For: 127.0.0.1 and they now appear to be local! This is one case where using a framework without understanding how it works in the backend can really be bad...
Edit: Relevant
I wrote a blog post recently about how I stumbled across a vulnerability in StackOverflow's application. It's very relevant here, since it exploits a very similar mechanism to what this question is looking for (although the circumstances around it are somewhat narrow):
How I Hacked StackOverflow
The remote address is not something added out of courtesy, it's used in the IP protocol to route packages, so if you send a package with a fake address, you will not receive a response, and since you're talking about a HTTP request, which is delivered over a TCP connection, which takes several IP packets (and the matching responses) to set up:
No, that's impossible (except of course by actually sending the request from the same host via the loopback interface).
Apache populates $_SERVER['REMOTE_ADDR'] from a TCP socket that it uses to communicate with your browser. It is IMPOSSIBLE to influence this variable over the open internet because of the three-way-handshake. If the client and the server is on a broadcast network, like wifi, then you can sniff the wire and complete the handshake.
If you browse via a proxy, $_SERVER['REMOTE_ADDR'] may be set to the proxy's IP address rather than the end user's.
There are other headers which you can use instead in this case: This page gives a function which checks all the possibilities and provides the address most likely to be the end user's:
http://roshanbh.com.np/2007/12/getting-real-ip-address-in-php.html
However if the user is proxying using a badly configured proxy, or a malicious one, or one designed to anonymise the end user, then you won't be able to guarantee any of the headers other than REMOTE_ADDR (which would only lead you as far as the proxy).
If your end user is browsing via HTTPS, then REMOTE_ADDR will always be his IP address; you can't use proxy forwarding via HTTPS. Therefore, the one way to be absolutely sure of his address is to get him to open your site in HTTPS.
You can overwrite any item in the $_SERVER array, including the one you mention, in your server; of course, not in someone else's.
However, it won't change your computer's IP address.
REMOTE_ADDR
The IP address from which the user is viewing the current page.
You can request script using proxy, etc. to change IP address but you cannot set there any text you want.
That is a variable set by apache or whatever server you're using. You cannot spoof it.
You may run $_SERVER['REMOTE_ADDR']='127.0.0.1'; at the beginning of the scripts, but i doubt thats what you're trying to do
I'm doing a PHP cURL post, using a complete URL (http://www.mysite.com), from one page to another on the same site. (I know this isn't the best way to do it; but for my purpose this is what I need)
My question is:
Will the cURL post still go out across the internet, do a name lookup and travel a route as though it were a post coming from a different site. Or will the post stay on the servers local network?
There are multiple parts to the request, the dns lookup and the get or post to the site.
DNS Records are usually cached on most OSes, so it's rather unlikely that the server would have to do a dns lookup for it's own external ip, but it's possible.
As for the post, let's assume a basic layout:
Firewall => DMZ Apache PHP Server (www.mysite.com)
222.xxx.xxx.123 => 192.168.0.2
And mysite.com resolves to 222.xxx.xxx.123, then your request will go to your firewall's external interface and bounce back in. That's not terribly public traffic, but it goes out none-the less.
However, if you wanted to bypass that, you could put an entry in the host file of the server to say
127.0.0.1 mysite.com
(assuming you control the server, ie not shared hosting)
No. The post itself (unless you have multiple interfaces and your routing is totally screwed up) will not traverse the internet. Your local host ought to be able to resolve its own name as well, but there is a possibility that a DNS request will be made to determine the IP address corresponding to the name. I would hope that the network stack implementation on your system would prevent the post's packets from even hitting the wire (similar to localhost), but I wouldn't count on it.
It depends on your network setup. Many sites have a domain name pointing to the IP address of a front facing router or load balancer which forward the request to the web server.
If that's the case a request to your own site can make a round-trip to the router. Though it's unlikely that the request will go through the internet unless you have a very unusual setup (such as round robin DNS with multiple datacenters).
You can avoid the round-trip by associating the site FQDN to the loopback interface in your webserver /etc/hosts which will also save you a DNS request.