Messaging-system with E2E encryption

This project is a simple tcp client-server messaging system with E2E encryption support. The server is implemented with python, and the client is implemented with C++ with Boost and Crypto++.

General architecture

This is a simple implementation of a client-server TCP based messaging system with end-2-end encryption of messages. Each client has a PKI pair, and will negotiate a symmetric key with each additional client it wish to communicate with. This implementation also fully supports files (including big files).

Communication spec

Request format

The request has the following format:

• Client ID - 16 bytes - the client ID
• Version - 1 byte - the version of the client
• Request code - 1 byte - the request code
• Payload size - 4 bytes - the size of the payload
• Payload - dynamic size - the payload data

Response format

The response has the following format:

• Version - 1 byte - the version of the server
• Response code - 2 bytes - the server response code
• Payload size - 4 bytes - the size of the payload
• Payload - dynamic size - the payload data

Requests and responses

Register request

Code = 100 Payload = Name(255 bytes), Public key(160 bytes)

Success response : Code = 1000 Payload = Client ID(16 bytes)

Get client list request

Code = 101 Payload = NONE

Success response: Code = 1001 Payload = For each client: Client ID(16 bytes), Client name (255 bytes)

Get public key request

Code = 102 Payload = Client ID(16 bytes)

Success response: Code = 1002 Payload = Client ID(16 bytes), Public key (160 bytes)

Send message request

Code = 103 Payload = Client ID(16 bytes), Msg type(1 byte), Msg size(4 bytes), Msg content(Dynamic)

Message types:

1. Public key request
2. Public key
3. Text message
4. File message

Success response: Code = 1003 Payload = Client ID(16 bytes), Msg ID (4 bytes)

Get messages request

Code = 104 Payload = NONE

Success response: Code = 1004 Payload = For each message: Client ID(16 bytes), Msg ID(4 bytes), Msg type(1 byte), Msg size(4 bytes), Msg content(Dynamic)

Failure response

Code = 9000

The server

Main logical units

Name	Responsibility
server_main.py	The main entry point for the server
bytes_buffer.py	A set of classes to implement large size capable bits stream from various sources
model.py	Implementation of basic model classes
storage_manager.py	Storage management which is responsible for storing the clients and messages of the messaging system
db_storage_manager.py	An SQLite implementation of the StorageManager class
request_handler.py	Logic handler for the server. responsible for processing the requests and returning the responses
request_reader.py, response_writer.py, request_payload_parser.py, response_payload_writer.py	Reading and writing requests and responses

How to run the server

The server requires python version 3.x to run.

To run the server:

1. Create a file named "port.info" with the port number information
2. Run the command "python server_main.py"

On the first run the SQLite DB will be created by the name "server.db".

The client

Main classes

Name	Responsibility
MessagingSystemClient	The main entry point for the client application
TestingManager	Running the test suite
ByteBuffer, BinaryByteBuffer, FileByteBuffer, SocketByteBuffer	A set of classes to implement large size capable bits stream from various sources
ClientLogicHandler	Responsible for the implementation of the client actions
InteractiveMenuManager	Responsible for showing the menu and running the user selected commands
Request, RequestReader, Response, ResponseWriter	Set of classes for request and response and reading and writing them from the socket
EncryptionUtils	Facade implementation for all encryption related operations in this project, e.g. generation of keys, and decryption and encryption

How to build the client

Windows

Using Visual studio you will need to set up Boost and Crypto++ and then compile the code.

Linux

The client was tested on Linux x64 / Ubuntu OS.

Using eclipse, set up Boost and Crypto++, and compile the project

How to run the client

To run the automatic tests for the client, simply run it with the "test" argument.

To run the client normally:

1. Create a file named "server.info" on the running directory with the HOST:PORT information of the server
2. Run the "client" command
3. Register yourself to start working