Pass value to C binary through cURL (or FTP) - c

I've got a web application that I know to be written in C, that's running on a specified IP address and port. I can access the application either with telnet or nc. With each of those, once connecting I'm prompted for input.
Since I've got a copy of the binary, running it through strings and hd showed me that the application is looking for a particular string to validate.
There's a file sitting on that domain that I'd like to access, which I can't seem to do with telnet or nc, so I'm thinking that either cURL or ftp would be the better bet here.
However, since the string validation that happens with this running service isn't really a password, I'm not sure how to pass this string value into the service with cURL or ftp. My gut tells me that I probably need to structure the command as a POST, but since this definitely isn't an HTTP service, I'm not sure how to proceed.
Any ideas?


(not an answer, but too long to post as a comment)
when dealing with undocumented custom protocols, telnet/curl/wget is definitely not suitable, and nc is not practical. write your own client.
you say the server is expecting a string? well, maybe you could run a dictionary attack on it, make a client that tries everything in a large dictionary (like this?), looking for any non-standard response, and go from there. add any strings you find in the binary too, ofc
if that gets you nowhere, maybe the binary is vulnerable to timing attacks? maybe you can extract a string that it is looking for, through a timing attack
and because you already have the binary, you could run it through a disassembler and study the assembly code, it should reveal both whether or not it's timing-attack vulnerable, and, if the strings are hardcoded, what string it is looking for, albeit, reading compiled assembly code is really difficult.. (game crackers does this all the time for cracking video game copy protections)

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While reading on ZMQ, I encountered this link - A Web Server in 30 Lines of C. Highly motivated, I tried running the code and it does indeed print "Hello, World!"
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response would change with sprintf of the name.
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Am I missing something obvious here?

I agree it's pretty neat, but it's not an HTTP server - it doesn't understand anything about HTTP, especially not how to parse a query string.
You can certainly use 0MQ to send messages very simply. The zguide has examples of many patterns in many languages - should be everything you need. You need to write both a client and server (really a sender and a receiver) to send anything meaningful over 0MQ. If you're hoping to use a generic http client like curl or wget, then use a real HTTP server instead of 0MQ. Many scripting languages let you launch an HTTP listener in a single line of code. Choose what best fits your needs. If you do use 0MQ, there is an IRC channel on Freenode where you can get help.

Storing passwords in a client-side application in C

I'm writing a client-side program (in C) to access a certain web site, and I'd like to implement a 'remember password' feature in it. I don't think storing it in plain text is a good idea (what if the user's running malicious software which might find the password?), so I'm wondering. what's the best way of storing a password in such a case? I need to be able to recover it verbatim (a hash/salt won't do, the server needs the entire password), and the solution needs to be somewhat portable (it has to work at least on GNU/Linux).

You can use the lib openssl and write the password crypted with aes in a file. The location of the file may be only know by user.
Else, you can use a system variable as key.
If the user compile the program, you can generate a key and compile with (so store it in the executable)

Protecting PHP CLI scripts

I'm currently writing a little commercial PHP Script which would be a VPN (PPTP) manager, in command line.
Actually, it's a socket server which is waiting for commands like "create", "suspend", "unsuspend", "changepassword"... Then it parses the PPTP files and modify them.
The thing is that I will have to give the PHP files which are so simple that they ONLY need php5-cli to be installed (and no apache, nothing else), I need to protect it from being read (actually, it's only 1 file, which is an entire class. The rest can be clear).
I want the system to be lightest as possible, that's why there is no need of GUI, web-server, curl, *sql...
I thought about IonCube, but it's very expensive and can't be used on with cli scripts because it needs a loader, which is loaded by apache. This is the problem of every encoder I think.
I thought about HipHop PHP (From Facebook), but it's hard to understand how to use (because I can compile my sources, but the user guide says how to launch our clear source with it :/ ).
So, I'm here to get help about that. I have some PHP-cli scripts, which must run in command line, which don't need a webserver to work, and I only need (as it's a commercial product) to protect my sources from reading and illegal ditribution (it will be easy to bypass the licence system). This file is simply a PHP class.
Thanks.
-- Edit --
Precisly, I want to make it paid by month, 6 months, year. If it's clear, then everybody will be able to comment the licence check, and have it for free. I love the opensource, for proof, I've written 3 classes for this project, a debug/warning/error manager with output handling (stdout/stderr/logfile) and a Socket class, which you just have to include and extends from, and you have a complete server (and you just have to implement needed functions, the server will call the "received commmand"(), and I don't want to obfuscate these 2 classes.

As to ionCube, there is an online encoder available that does a one-time encode of your script for just a few bucks, depending on the size of your codebase. If you write your own licensing mechanism, you could be able to use that. Besides, your statement about the ionclube loader is incorrect, no apache necessary, it's just a module that can be loaded in php.ini. IonCube is - in my opinion - a good choice.
Do take your time to really ask how much protection you need. A computer will always understand how to interpret your code, so eventually a human being will be able to peek inside, if he really wants to.
If the ionCube loader isn't an option on your clients, there are several 'obfuscators' for PHP out there that will probably stop the "quick peekers" from understanding the code in less than one hour. These obfuscaters won't encrypt your code, but they will make it less readable by changing all your variables, functions and class names into some arbitrary hashes, and remove all your comments and whitespace. They don't need anything on the server to be run, but in the end your PHP code will still be just the same.

Connect to a website via HTTP in C

I have some C code that parses a file and generates another file of processed data. I now need to post these files to a website on a web server. I guess there is a way to do a HTTP POST but I have never done this in c (using GCC on Ubuntu). Does anyone know how to do this? I need a starting point as I have no clue of doing this in C. I also need to be able to authenticate with the website.

libcurl is probably a good place to start.

I think Hank Gay's suggestion of using a library to handle the details is the best one, but if you want to "do it yourself", you need to open a socket to the web server and then send your data in the HTTP POST format which is described here. Authentication can mean a variety of different things, so you need to be more specific.
Unfortunately, all of the above three jobs involve a fair bit of complexity, so you need to break the question down into stages and come back and ask about each bit separately.

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