I am developing an application which has one web server and one C# client which posts XML to the web server. The web server needs to know the local IP address of client. I tried methods to retrieve the IP address at the server side, but these methods don't give the IP address of the client when there are proxy servers or NAT in between. So I need to find the local IP of the connection at the client application and send it with the request.
The problem is in HttpWebRequest. I don't see any method by which I can get the local IP address of the connection made while sending HTTP request.
CLARIFICATION:
The client in my case is not browser-based. It is a C# application. My server has specific rules based on local IP, that was are used to connect to the server while sending the HTTP request. In my case, local IPs are fixed. There could be multiple IPs on a local machine -- that's why I want the local IP associated with the Socket used to send the request. This can be solved if I use TcpClient in C# and implement the HTTP protocol on top of it, but I want to avoid that. So, is there any way I can get the socket associated with HttpWebRequest before posting the request?
It is not possible to get the local IPAddress of the connection that HttpWebRequest is going to use. However, you could use Dns or System.Net.NetworkInformation class to get all the local IPaddresses, and send them as a custom header with your request. On the server side you could parse this header, and see if any of the IP's match the one that you are expecting.
However, as Damien has indicated above, this solution is not foolproof, people could spoof the IPaddress to the one the server is expecting. Maybe you need to take a step back and think what security you are trying to achive by this? And see if you could accomplish your goals by a different method - for eg: user Authentication using a supported method like Basic(over HTTPS), Digest, NTLM, Kerberos, Negotiate, or use SSL with client certs?
One possible solution is to tell the client what ip it should use when connecting to the server, and include that ip in a custom header for the server to read.
var srcip = IPAddress.Parse("10.0.0.1");
var request = (HttpWebRequest)HttpWebRequest.Create ("http://example.com/");
request.Headers.Add("X-Original-Client-IP", srcip.ToString());
request.ServicePoint.BindIPEndPointDelegate = delegate { return new IPEndPoint(srcip, 0); };
request.GetResponse();
There's no guaranteed way of doing this. Javascript and server-side code can only see the public address, not the local one. There is a method for getting it using Java (mentioned here), but it relies on both Javascript and Java being available, and the user's browser supporting that particular call.
Given that many local IPs are assigned as needed (my home PC's is assigned using DHCP, my work PC's changes occasonally too), do you think knowing the local IP would actually be any use?
Maybe you should move from HttpWebRequest to SOAP requests/responses if XML is what you send over the line. Implement ASPX web service or WFC webservice. HttpWebRequest are always seen to the server as they are coming from the last IP that issued them so that would be NAT or proxy.
However, I too find it odd enough that you need to know local machine IP on the server side.
Related
I have an ASP.NET MVC web app and I need to get the client IP address.
I researched this and there are two main possibilities:
to retrieve the IP using HTTP headers
to retrieve it using HttpContext.Request.UserHostAddress
The problem with the first method is that the IP can easily be spoofed.
The problem with the second method is that if the client is behind a proxy, it retrieves the client proxy - not the client's own IP.
(See here - this is the best resource I found in SO describing the above problem)
My question: how can I retrieve the client's IP address in a way that cannot be spoofed and to get his own IP address, not his proxy's IP - is it possible?
I want to retrieve the client PC information at the sender end. When a client sends a request/message at client end in simple socket programming lets say, i want that client to retrieve the information of client PC e.g like which windows is client using , what is the name of client's PC etc.
I have retrieved client IP address using
connectionSocekt.RemoteEndPoint.ToString();
I have searched whole internet and YouTube But i couldn't find any where how to retrieve other information of client PC. Kindly help me with this thing.
There are many ways to get information about a remote host on your local network.
You will NOT necessarily get it from some arbitrary "sockets" program: a basic TCP/IP connection simply doesn't have that information .
A client request to a web server, however, might have some of what you're looking for. Look at HTTP headers, particularly the User-Agent header.
Since you're on Windows, you should also look at WMI: https://learn.microsoft.com/en-us/windows/win32/wmisdk/wmi-start-page
I am writing a proxy with TcpListener in C#.
This proxy listens a port that users send request to. And when accepted a user request, it will parse the request header and find the host name. Then it creates a TcpClient to the host server.
Here comes the problem. When http request comes, it should connect the port 80 of the server; while https request comes, it should connect the port 443 of the server. But I have no idea of how to distinguish http request and https request.
Question in one sentence: how to know it is a http request or https request that TcpListener accepted?
Many thanks!
You've stepped in a problem that has flustered web server administrators for a long time.
Here's the process:
Web browser establishes a TCP connection to a particular IP on the web server.
The web server knows what IP it's getting a connection from, knows that that IP is only ever used for secure.example.com, and so loads the SSL certificate for secure.example.com.
The web server and web browser negotiate a SSL connection.
The web browser sends vanilla HTTP headers down the SSL pipe, which include the "HOST: secure.example.com" line that indicates the virtual host to use.
The web server processes the request and sends the response using vanilla HTTP headers sent down the SSL pipe.
The web server has to decide which virtual host to use before it has any HTTP headers. This is because it has to negotiate an SSL connection first, and it has to know which certificate to use first. The vanilla solution is to use IP-based virtual hosts - run the web server on IP address X; whenever the server gets a request sent to address X, it knows the request belongs to the configured vhost for that address.
The problem with that scheme is that the server has to have separate IP addresses for each secure website it runs. That might be many, many IP addresses, and is either costly or impractical.
Step in Server Name Indication. When the web browser is negotiating the SSL connection to the web server, the web browser includes the hostname it wants to connect to in the SSL negotiation information. Now the web server can use that information to do normal name-based virtual hosts, and so the web server can run a thousand different secure websites each with their own SSL certificates all on exactly one IP address. Everything is right in the world again.
You want to get in the middle of this, which means that you have to understand the SSL/TLS negotiation phase, parse the server name information, and forward the request down to the right web server.
Your new flow looks something like this:
Web browser establishes a TCP connection to the proxy.
Proxy begins recording the SSL exchange.
Web browser starts to do SSL negotiation, and as part of such, sends the Server Name Information down.
The proxy parses the Server Name Information, decides which web server should handle the request, and forwards the SSL negotiation information to the web server.
The proxy does not otherwise participate in the negotiation; it reads the SNI, but otherwise is completely "pass-through".
The web browser and server complete the SSL negotiation, the server picks the right vhost, and the browser sends vanilla http headers for a request.
The web server reads the vanilla headers via the SSL connection, and processes the request.
Now that that's been said, you might realize that sticking your nose in the SSL connection negotiation might be more trouble than it's worth. Turns out a few other people have already had the same idea as you and have implemented a few programs that seem to do exactly what you're trying to do - do a search for "http sni proxy" - I came up with this: https://github.com/dlundquist/sniproxy
The headers are entirely encrypted. The only information going over the network 'in the clear' is related to the SSL setup and D/H key exchange. This exchange is carefully designed not to yield any useful information to eavesdroppers, and once it has taken place, all data is encrypted.
Update By the way After the SSL negotiation, normal HTTP headers will travel inside the encrypted stream, so there is really no difference between the two.
I don't think this is duplicate of System.Net.WebRequest not respecting hosts file since I do not believe my issues to be proxy related (and it's making the request to localhost essentially).
So I've got a C# ASP page that makes an HttpWebRequest. Now, on this server I've done some custom mapping of some dev domains to the server's IP address.
HttpWebRequest request = (HttpWebRequest)WebRequest.Create( "http://someproject.dev" );
ERROR:
The remote name could not be resolved: 'someproject.dev' at System.Net.HttpWebRequest.GetResponse()
My Hosts file on the server (and my client) has 10.0.1.115 someproject.dev
I've also tried it with 127.0.0.1 on the server
Another note, both .net apps are running under hosts file/IIS mappings, i.e. one app is making a x-domain request to the other (which is permitted, i know that's not the cause because this works in our production environment).
Also, I'd like to avoid System.Net.Dns, unless you guys agree that's the only way it will work.
I would check your server. Any web calls that are made from the server are checked to see if the DNS is in the hosts file. Sounds like a server problem instead of a programming problem.
Presently I am doing a project on designing and implementing a firewall. Everything is working fine. Here I am filtering all packets going through a TCP port. But I need to send a custom page if a page is being blocked. Like "Your page is blocked by admin". I don't have any idea how to do it. Can I do it using raw sockets? If so please tell me, how to? But as I know raw socket does not work for sending on Windows XP SP2 and later, is there any other solution?
EDIT: I used C++ to create a DLL for an IP address filter. Then I imported it in my C++ program. IP addresses are blocking fine. But my customer needs the custom message when a browser is not finding its page.
If you're selectively allowing access to certain web pages, you're essentially acting like a proxy. And you'll need to act more like one if you want to respond to clients with an error page.
A browser making an HTTP request will expect the response on the same connection it opened. In order to return a "blocked" page, you'll need to determine whether the connection is to someplace you don't want the user to go, and if not, return a valid HTTP response (even if that response is an HTTP error like "403 Forbidden" or something more appropriate to a proxy) on that same connection.
If you're blocking the connection before it's even opened, ie: blocking access to certain IP addresses, then you're kind of stuck. The most you could do is return an ICMP message saying the host isn't available. You need to at least accept the connection if you can, accept the incoming request, and reply with your error message. Anything less, and a browser typically won't know what to do with it.
Hey, Since you're working on that low level
Can't you redirect the request by modifying its HTTP header?