I have a simple networking program for sending and responding to HTTP requests/responses. However, if I wanted to send a HTTP or another request via a SOCKS5 proxy, how would I go about this? I'm using C Unix sockets.
I could solve this by creating a proxy server in Linux. However, my intention is so that I can send this to a proxy server I do not own so that it can be forwarded to the destination server. I couldn't seem to find a library. I found an RFC for it which I've read https://www.rfc-editor.org/rfc/rfc1928.txt , but i'm still not 100% unsure how to format my request.
Am I supposed to send the segments for the handshakes as hex? If so, would I send a string of hex 0F3504 or \x0F \x35 \x04 or 0x0F3504? Another question is do i need to denote that header = value in the message, or does the SOCKS5 server know what header i am referring to by the position of the byte it is looking at from the message I've sent?
Any clear up would be very much appreciated
Some time ago I wrote an open source C library that may help you: https://github.com/brechtsanders/proxysocket
Maybe you can use the library. Its quite easy, just replace the connect() with stuff from the library and for the rest you can keep the rest of your code that uses the socket that is returned.
Or you can take a peek in the code to see how it's done there.
Related
I'm trying to create a bridge in C Language that uses two protocols : OPC-UA and MODBUS.
Between the client and the bridge I used the protocol open62541 to ask for some data of any type. When the bridge receive the request, the memory requests start, from the brigde with the protocol MODBUS, to the MODBUS server, that should send back those memory variable asked.
My problem is that I cannot find any way to see the point in the code, where the Server recieve the Client request.
I need to find how to send those memory variables back from the server to the Client.
I would be glad if someone has the solution.
By guessing I assume you mean a ReadRequest and you want to find out where this read request is handled in the server?
It could be this one: Service_Read
https://github.com/open62541/open62541/blob/71e9a44d1aec5bc0cce465c8daefe47883b25f6c/src/server/ua_services_attribute.c#L394
Or also the Operation_Read:
https://github.com/open62541/open62541/blob/71e9a44d1aec5bc0cce465c8daefe47883b25f6c/src/server/ua_services_attribute.c#L394
you are looking for?!
I'm writing a port scanner in C and i want to detect what service is running on an open port and its version.I've already wrote the scanner code but now i have no idea about how to detect running service.
What can i do?
If you are determined to do it in your own code, you can connect to the port, see if you get any data on it, if nothing then send a few bytes, and check again.
Then match that against expected response.
to get an idea what you are looking for, you can connect manually to the port with telnet and poke at it. In many cases (a web server is an easy example) you must send some correctly formatted data in order to get a usable response.
nmap has done all this and much more (e.g. extensive checks such as looking for byte order and timing of arp traffic)
UPDATE: several people have mentioned well known ports, but that won't help you discover standard services running on nonstandard ports, such as ssh or http servers running on custom ports.
If server sends something first, use that to identify protocol.
If not, send something according to some protocol, such as http, and see what server sends back (valid response or error). You may need to make several attempts with different protocols, and a good order is important to minimize connection count.
Some protocols may be very hard to identify, and it is easy to make custom server with unique protocol you don't know about, or even hide real server under simple fake server of other proto such as http.
If you just want to know what the port usually is, check "well known ports" and official reserved ports.
Also check nmap source code.
Do you know of any HTTP client library in C (with SSL support) that also allows direct communication with the remote server?
I have a client-server application where the client uses HTTP to start a session in the server and then tells the server to switch the connection from HTTP to a different protocol. All communication is encapsulated in SSL. It is written in Perl and works well, but I'm looking into implementing the client in C.
I know libcurl gives you access to the underlaying socket but it's not enough because of the SSL requirement.
Notice that libcurl doesn't do the SSL part by itself, it uses OpenSSL. So, if you can get the socket handle from libcurl after the first HTTP interactions, AND the session key it uses (some spelunking required) you can go on directly with OpenSSL from that point.
I think that you must be looking for this otherwise you must have to write it yourself, like this
Sounds like you want Web Sockets. Don't know if there's a C library available though. I would assume there is, if you dig.
So, i am assuming that i will need to use sockets(i am a newbie to C).
The program will be for Windows(in pure C). And i shall be using these examples
http://cs.baylor.edu/~donahoo/practical/CSockets/winsock.html
My question is, instead of the client program connecting via TCP, i want the server to accept connections via a web browser i.e via HTTP.
So if the server program is running you type http://yourip:port/?gettemps and the server responds, but how do i do it?
As you might have guessed, this program will be for monitoring temps, remotely, via a web browser. But not for the CPU, for the GPU using AMD's ADL library(so yeah, only AMD cards).
The simplest option that is supported by most web servers is CGI - Common Gateway Interface.
Microsoft, of cource, has their own way of running web apps - ISAPI.
HTTP is quite a big standard, you might want to use some library such as libcurl to handle the details for you.
If you decide to code it yourself, HTTP is running over TCP so you first need to open a TCP socket at the standard HTTP port 80. Then simply listen on the socket and parse the incoming HTTP data - a great summary is given here: http://www.jmarshall.com/easy/http/.
Web browsers sends http get request to the server via tcp. If you are writing a web server from scratch than, you will need to parse data from web browser. http get request are string like for example GET /images/logo.png HTTP/1.1. So tokenize that string as it comes through tcp and get the command.
As you received your commands to the server call appropriate functions to handle your request.
Here is an great example of simple http server. You might want to make server multi-threaded as you may have multiple simultaneous users.
If you have already set up your web server to run the app on the appropriate port you can use getenv("QUERY_STRING") to access the web equivalent of command line parameters.
It would be better to call your program directly rather than just using the server to access a single default program as your example does, thus you could use http://yourip:port/yourprogram?cmd=gettemps. In this example getenv("QUERY_STRING") would return 'cmd=gettemps'.
as part of my project, I'm trying to send IP packets that contain HTTP requests to Google. I'm using Winpcap library and VC++. Currently, I have the TCP three-way handshaing packets done, but I'm stuck on sending the actual HTTP request packet after I send the TCP ACK packet. When I capture the packets using wireshark, this packet is marked "TCP segment of a Reassembled PDU". The protocol column is 'TCP' not 'HTTP' also. What's wrong? How would I send HTTP packets in this way?
You aren't necessarily doing anything wrong.
By default, Wireshark hands the TCP data to a higher level protocol handler - in this case, one that tries to reassemble entire HTTP requests and responses. It attaches the reassembled message to the final packet in the sequence, and labels the other packets with "TCP segment of a reassembled PDU":
You can disable this reassembly feature to examine the individual packets:
Edit -> Preferences -> Protocols -> TCP
Uncheck "Allow subdissector to reassemble TCP streams"
Why are you using WinPCap to send the packets? You should be using normal sockets instead. Better, use a socket library that implements the HTTP protocol for you, such as curl, or even Microsoft's own WinInet or WinHTTP APIs.
I would highly recommend that you learn the basis of the HTTP protocol before you try this if you're planning on extending this. Mess with doing raw sockets and throwing get requests; read some source code.
However, I wouldn't really see the point of pcap. You should be able to use the Wininet library if you don't want to have to code the actual socket:Wininet lib
However, if you're wanting to code raw sockets, I would go ahead and use winsocks. The difference between HTTP and TCP is hard for some to understand; HTTP is BASED on TCP, so they are technically all in the same, TCP is used for quite literally thousands of applications. Most of the connections on your computer are TCP.
If you're trying to intercept a connection as a MITM attack with a pcap program to send an HTTP request, I would probably learn some programming in Pcap. There are numerous tutorials for this, such as this one.
PS: Look up a winsocks tutorial as it's quite hard to understand for beginners. Also, winpcap isn't supported on all systems, and it can be (in some cases) a pain to install. It would honestly be better to use winsocks to do this. Wininet has much more support, and I (don't hold me on this) believe that all of the W2K+ builds all have wininet, so for compatability (which I don't really think is a problem for you) issues I would use wininet or winsocks.
Probably you are not finishing the request with \r\n twice.
If you send the GET / HTTP/1.0\r\n string, you will not receive any packets.
You must send this string: GET / HTTP/1.0\r\n\r\n.