Researching on how a server can figure out a client's IP address, I see that one needs to inspect the X-Forwarded-For header chain.
I understand that the client, ISP, and then routers and proxies declare their IP addresses there.
However, the server handler also has access to req.RemoteAddr field to read the client's IP address. How is that RemoteAddr determined exactly? Is it based on a specific header in the request? If yes, which one(s)?
I have tried inspecting the usage of the field and how it is set but the implementation details are hidden behind an interface.
The net/http server sets RemoteAddr to the string form of the network connection's remote address. The string is typically in the format "IP:port".
In the case of a TCP connection (the typical scenario), the network connection remote address is taken from the IP source address and the TCP source port.
The address can be the address of the client or a proxy.
The net/http server does not consider the headers when setting RemoteAddr.
Related
I have a Go service, deployed on Heroku, which pulls the IPv4 address from the request header successfully.
ip := net.ParseIP(strings.Split(r.Header.Get("X-Forwarded-For"), ",")[0]).String()
I have deployed the identical code as a service to Google Cloud, and the IP addresses are frequently IPv6 in about 25% of the time. After examining the full Request Header, there is no IPv4 address available anywhere, only IPv6.
Heroku's Request Header X-Forwarded-For ALWAYS contains the IPv4 address, yet Google Cloud doesn't. Does anyone know a way to force the IPv4 format for Request Headers in Google Cloud?
Clients can connect via IPv4 or IPv6 but not both. Only one address family will be used by the client and only one IP address will be recorded by the proxy.
Additional information:
Heroku does not support IPv6 so clients are forced to connect using IPv4. reference
If you only want IPv4 connections, do not enable the IPv6 frontends. However, I recommend using IPv6 where possible.
Say I have a list of proxies - I pull out of one of these proxies. It's nothing but ip and port. From a programming level, you need to know the protocol to use such as socks5, socks5h, http, https... etc etc. Is there a way to retrieve what kind of protocol a proxy uses from the information given?
If you are using Node.js you can try check-proxy library, though it does much more than just checking protocol.
Your proxy server identify the port number for example 6080,9180,etc so you can easily identify the proxy server.
Your id address also private or public you can use 'proxy server ip address' that automatically create a virtual proxy network.
Example: Your private ip address is 172.16.10.158 you can use proxy server, your ip address will be 136.56.89.210. You can use public ip ex 125.124.85.69 change in to 179.68.36.49.
When source address field is empty, all runs fine. When I put in an IP, even if it is my actual IP, I get an error:
Response code: Non HTTP response code: java.net.SocketException
Response message: Non HTTP response message: Network is unreachable: connect
I run Windows... Also I have already tried all the Implementations.
There should be few pre-requisites met:
You need to have HTTPClient implementation (see HTTP Request sampler documentation)
Source address field[Only for HTTP Request with HTTPClient implementation]
In case of single IP address:
The IP address needs to be available in the underlying operating system, it may be either IP associated with NIC or an IP alias
Relevant Source address type needs to be specified, in case of single IP it should be IP/Hostname
See Using IP Spoofing to Simulate Requests from Different IP Addresses with JMeter guide for more detailed information on the domain.
I have a ruby server based on TCPSocket (non-HTTP).
I have 2 different domains, both pointing with an A-Record to my servers IP Address (the same one). So, there are clients connecting to one of those domains.
Is it possible to tell which domain a client was connecting to?
I saw that this is possible in other protocols, but I'm not sure if this is based on manually added headers or really extracted from the basic tcp/ip connection. E.g. in PHP there is $_SERVER["HTTP_HOST"] which shows to which domain a client was connecting.
At the TCP socket level, the only things that are known are the source and destination IP addresses (and ports) of the connection. How the IP address was resolved via DNS is not possible to know at this layer. Even though HTTP works on top of TCP, HTTP servers have to look at the HTTP headers from the client to know which domain they are making a request to. (That's how the HTTP_HOST value gets filled in.)
One possible solution is to configure your server to have an additional IP address. This can be by assigning an additional IP address to the NIC or adding an additional NIC. Then have each domain use a different IP address. Otherwise, this is not possible and you may want to consider your application protocol on top of TCP to convey this information.
http://ipfuck.paulds.fr/
We've been recently getting hammered by this Firefox plug-in. It sends a fake IP in the headers so when our nginx web server picks up the IP it is a fake one.
Is there any way to get a real IP address or block out requests that have this plug-in installed?
There is actually no client IP entries in any HTTP Headers. There are only some un-official proxy headers which are added to a request, so that a proxy server can tell you the real ip of the connecting client (since the tcp socket will only reveal the IP address of the proxy server).
The plugin you linked to adds those proxy headers, to "fake" a proxy request, by adding a X-Real-IP: 1.2.3.4 or X-Forwarded-For: 1.2.3.4 header to the request. But no one forces you to use that IP address (which can be fake, like the 1.2.3.4 example here), you can always use the IP address of the socket that initiated the connection - which will be the client's real IP address if he uses the mentioned plugin.
Within the location section of your nginx configuration, you get the socket IP address through the $remote_addr variable. To retrieve the "fake" IP address, you can use $http_x_forwarded_for or $http_x_real_ip variable.
If you are using any application/cgi backend, you usually can examine the full headers and the socket IP address (i.e. in PHP you should check $_REQUEST and $_HEADERS variables)