AL 26 OTTOBRE, SU DUE MACCHINE LINUX, VA TUTTO TRANNE LA FUNZIA DI DECRYPT

secure_p2p_chat

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• What is secure_p2p_chat?
• But how does it work?
• Installation
• Documentation
  • Tracker
  • Peer

What is secure_p2p_chat?

secure_p2p_chat is a safe way to chat with a peer without a centralized server that routes the messages. The tracker server is theere only to assign a private ipv4 address to confiure the VPN and to store data useful for the connection.

But how does it work?

First of all, the peer connects to the tracker and retrieves the private ip address assigend by it. Then it generates a RSA private key and its realtive public one and the first part of the wireguard configuration.

After this, it uploads to the tracker server the public key for the RSA encryption (used for encrypting messages) and the Peer configuration for wireguard (aka, what others should wirte in theeir own config file in order to connect to this host) in a specific folder, named .-files

This gets us to the first checkpoint.

Now we have the second part, conneceting to the peer. The program prompts us the public ipv4 of the peer we wanna chat with (the ONLY info we need). Then it downloads all the needed stuff to connect to the peer and auto adds them to the respective configuration files.

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Installation

In the future we are adding a dialog base configuration to facilitatee the process.

PRE-REQUISITES: gcc make

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Dependencies:

• libssl (sudo apt-get install libssl-dev)
• wget (sudo apt-get install wget)
• wireguard (sudo apt install wireguard)
• curl (sudo apt install curl)

Run

make dep

to install them.

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Documentation

1. Tracker

The Tracker file is a unique source file, with all the necessary parts built in. Just compile it with

gcc tracker.c -o tracker

THE TRACKER ASSUMES THAT:

    const int available_ports[NUM_PORTS] = {6969, 51810, 51812, 51811, 8080};
    http://<pub ip>:<port>/home/ubuntu/apple/ existis

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2. Peer

Let's now talk about the big part.

2.1 Compiling

Makefiles are used to simplify the compilation process.

• To compile and run the code, use

make compile
run

• If you want to compile and run with debug information printed to console, use

make compile_debug
run_debug

Once used, use

make clean

• to clean the diretory (also remember to delete the hidden folders!)

2.2 main.c

- 2.2.1 Headers

• First we include all the libraries, both the 'classics' and the custom written ones.

#include <sys/stat.h>
#include <unistd.h>
#include <stdio.h>
#include <sys/socket.h>
#include <stdlib.h>
#include <netinet/in.h>
#include <string.h>
#include <arpa/inet.h>
#include <pthread.h>
#include <openssl/ssl.h>
#include <openssl/err.h>
#include <openssl/err.h>
#include <curl/curl.h>
#include "librerie/configuringVpn.h"
#include "librerie/readFile.h"
#include "librerie/file_sender_new.h"
#include "librerie/miaLibVarie.h"
#include "librerie/new_version_p2p_chat.h"

• Then we define costants

#define MAX_IP_LENGTH 18
#define PORT 51810
#define MAX_BUF_SIZE 1024

• Last, but not least, we define the IP and the DIR of the tracker (this should be customizeed accordingly - in the future will write a setupper to aumatically do this when building from source)

#define PATH_TRACKER_DIRECTORY "http://13.53.40.109:8080/home/ubuntu/apple/"
#define TRACKER_SERVER_IP "13.53.40.109"

• We later define the conditional debug stuff

#ifdef DEBUG
    #define DEBUG_PRINT(fmt, args...)    fprintf(stderr, "DEBUG: " fmt, ## args)
#else
    #define DEBUG_PRINT(fmt, args...)    /* Don't do anything in release builds */
#endif

2.2.2 - Functions

• The "retrieve_assigend_private_ip" function retrives the assgned private ip from the tracker server
• The "download_file" functions downloads a file using wget.

char* retrieve_assigend_private_ip(const char* host, int port);  // -> from the tracker server
void download_file(const char *base_url, const char *ip_folder, const char *filename); // -> from the tracker server

2.2.3 - Main

• We begin by finding the current working directory (cwd)

char cwd[1024];
getcwd(cwd, sizeof(cwd));
DEBUG_PRINT("%s", cwd); //this will print only if you compiled with debug. 

• Now we concatenate the cwd with the needed folders in order to create and access them later.

char *pathVPNconfiguration = concatenateStrings(cwd, "/.vpn-secrets/wg0_vpn.conf");
char *pathWireguardPrivateKey = concatenateStrings(cwd, "/.vpn-secrets/privatekey");