I was looking to create a http2 streaming client in C which is able to connect to server, create stream and keep listening for messages from server on that stream without cancelling the stream unless explicitly cancelled or network issue.
I was trying to implement it via libcurl but seems there is no such support in libcurl, at best what I can do is just make a request with curl and not have a timeout. Then curl will just sit there waiting for the transfer to start or complete, until the server does that. And when one transfer is done, the client can just issue another request and go back to waiting...
But I just want to maintain the stream rather than issuing another request to server after receiving message.
I don't want to use GRPC which provides similar functionality but along with it comes lots of complexity of libs and platform dependencies to be resolved.
Is there any other C based library or any http2 stream reference which I should have a look at?
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I am implementing a Web proxy (in C), with the end goal of implementing some simple caching and adblocking. Currently, the proxy supports normal HTTP sites, and also supports HTTPS sites by implementing tunneling with HTTP CONNECT. The proxy works great running from localhost and configured with my browser.
Despite all of this, I'll never be able to implement my desired features as long as the proxy can not decrypt HTTPS traffic. The essence of my question is: what general steps do I need to take to be able to decrypt this traffic and implement what I would like? I've been researching this, and there seems to be a good amount of information on existing proxies that are capable of this, such as Squid.
Currently, my server uses select() and keeps all client ids in an fd_set. When a CONNECT request is made, it makes a TCP connection to the specified host, and places the file descriptor of both the client and the host into the fd_set. It also places the tuple of fd's into a list, and the list is scanned whenever more data is ready from select() to see if data is coming from an existing tunnel. The data is then read and forwarded blindly. I am struggling to see how to intercept this data at all, due to the nature of the CONNECT verb requiring opening a simple TCP socket to the desired host, and then "staying out of it" while the client and host set up their own SSL sockets. I am simply asking for the right direction for how I can go about using the proxy as a MITM attacker in order to read and manipulate the data coming in.
As a brief aside, this project is solely for my own use, so no security or advanced functionality is needed. I just need it to work for one browser, and I am happy to get any warnings from the browser if certificate-spoofing is the best approach.
proxy can not decrypt HTTPS traffic
You are trying to mount a man-in-the-middle attack. SSL is designed to prevent that. But - there is a weak point - a list of trusted certificate authorities.
I am simply asking for the right direction for how I can go about using the proxy as a MITM attacker in order to read and manipulate the data coming in.
You can get inspiration from Fiddler. The Fiddler has its own CA certificate (certification authority) and once you add this CA certificate as trusted, then Fiddler generates server certificates for each connection you use on the fly.
It comes with serious security consideration, your browser will trust any site. I've even seen using the Fiddler core inside a malware, so be careful
I am trying to design a Client Server kind of application in which my Server is a daemon that accepts client requests, send client's data over a serial channel to the other side(which is an MCU and its firmware will reply to the Server request over the same serial channel). My client can be a CLI application or any other system program.
My idea of design is -
Use message queues for communication between Client and Server since this is a local application and message queues are bidirectional and fast.
Implement a LIBRARY that acts as an interface between multiple clients and the server. This basically does the stuff of packetizing client data into a message(own defined protocol), create message queues, connect to server, send/receive data and then pass it to the respective client(using call backs). This library also exposes API that can be used by clients. Thus this library gives me the flexibility to add support for any new clients keeping the server program unchanged.
Server gets the data over serial from other side and passes it to the library over message queue. The library uses callbacks to send data to the client.
EDIT:
I am thinking of creating Message queues on the fly when any client requests arrive. If I do this, how does the Server daemon(which has already started at linux boot up) gets information about this message queue? Does the message queue has a name that is persistent across and used by other programs? I want to implement clients that will be blocked until it gets response from the server.
Could you guys please review this design and tell me whether my approach is correct. Please reply if you have any other recommendations.
Thanks in advance.
I'm trying to design a client program that connects to a remote server and sends various messages / request to it and expects responses based on the requests sent (for e.g. send a join message and wait for a response, then either query for some resource or ask for some info etc. in no particular order).
I would like to design the client such that the user can choose any of the possible requests to send after joining the server (after completing one request and getting a response if any it should allow them to carry out further requests or quit). Something like a menu of actions that it returns to each time (while also waiting for any data from the server)? However I can't seem to figure out how to this could be done. Is there a way to do this (preferably without getting into forking/threads)?
Any inputs on this would be really great. TIA
I would start off with a simple chat server to get your feel for socket programming. Google Example TCP Chat Server or something, you'll end up with simple examples like this: http://www.cs.ucsb.edu/~almeroth/classes/W01.176B/hw2/examples/tcp-server.c .. once you are able to telnet to your server and read/write to your clients, you should be able to progress from there and perform actions when your clients issue a specific command and that sort of thing.
Can anyone think of a good way to allow the server to notify the client based upon server processing? For example, consider the following events:
A user requests a deletion of data, however, due to it's long-running time, we kick it off to a queue.
The client receives a "Yes we completed your transaction successfully".
The server deletes the item and now wants to update any local structures any clients may be using (I'd also like to notify the user).
I know this can be done by client-side polling. Is there a event bus type way to do this? Any suggestions are welcome, but please keep in mind I am using GWT with App Engine.
The standard AJAX interaction is that the client sends requests to the server and expects some sort of response back fairly quickly.
In order for the server to initiate a request to the client, you will need to use WebSockets, and experimental HTML5 feature currently only supported by Chrome.
Or, to simulate this kind of interaction, you can use Comet (long-polling), made available in GWT by the rocket-gwt project.
You want server events for GWT? Have a look at GwtEventService (they couldn't have chosen a better name): http://code.google.com/p/gwteventservice/wiki/StartPage
Of course, it uses a Comet implementation, but you can't do any different when using HTTP, the client always initiates the communication. Request, response.
I want to implement proxy support (SOCKS5 and HTTP CONNECT method) in my application. There are two parts that needs to be implemented:
Detection of proxy details (protocol, host, port): I am using libproxy for that.
Connecting to the the proxy server and telling it to relay the packets. Get the connected socket and then use it in your application.
Is there library for the #2 part?
You might be able to hack libmicrohttpd into doing what you want without too much effort, at least as far as the user end. I'm not aware of anything that does what you want straight out of the box.
Now there is proxysocket (https://github.com/brechtsanders/proxysocket/) to do exactly that.
Supports SOCKS4, SOCKS5 and HTTP CONNECT.
The result is a normal connected socket so you don't have to rewrite the rest of your application.
libcurl can receive webpage via proxy. You can send raw http header to it, and let it talk to the proxy