A File Transfer Program Using OpenSSL

Overview

This guide outlines the steps to generate a self-signed SSL certificate and key for a server, compile and execute the server code, and set up the client to communicate securely with the server. It also includes some basic security measures.

Server Setup

Generate Private Key and Certificate

Run the following script to generate a self-signed SSL certificate and private key for the server:

bash server.sh

During the generation of the private key, you will be prompted to provide a PEM passphrase. Set it to 123456 unless you want to provide the password each time a new connection is set up.

Compile and Execute the Server Code

On successful gneration of server private key and certificate, compile and execute server.c by linking the associated libraries

gcc -o server server.c -lssl -lcrypto -lpthread
sudo ./server

Security Modifications:

Mod 1: To prevent accidental sharing of the server.key file with the client, delete the file after the SSL context is set up. This is a simple but effective way to ensure the key isn't shared accidentally. Mod 2: For additional security, run the server in a chroot environment. This restricts the server's visibility to the rest of the filesystem. To set up the chroot environment:

bash chroot.sh

Client Setup

Generate Private Key and Certificate (One-Time Process)

On the client's machine, run the following script to generate the private key and certificate:

bash client.sh

Compile and Execute the Client Code

After generating the client's private key and certificate, compile the client.c file:

gcc -o client client.c -lssl -lcrypto
./client

Establishing Connection

Once the connection is successfully established, the client can request any file from the server. If the file resides in a directory other than where server.c is located, please provide the absolute path.

This guide provides a basic setup for a secure server-client communication using SSL. The security measures mentioned, like deleting the server.key and running the server in a chroot environment, are essential for protecting sensitive information.