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jhchat

UPDATE

haven't taken security course when I made this. If I were to make such app now, a few changes would have been made:

  • Instead of plain TCP connection, I would look for TLS libraries
  • Dilemma below could be solved by either
    • trust a Certificate Authority
    • adopt DPKI, make use of block chain to exchange key pairs
  • Use thiserror to define my error types
  • Use tonic (grpc) or axum (http) instead of making my own protocol
  • Replace the encryption library by openssl bindings
  • Avoid some silly code in my current perspective

Goals

  • Users do trust Client (They build it from source)

  • Client can decide not to trust Server (By default public keys are exchanged through server)

    • User may manually set other's public key via third party communication
    • A pre-configured dummy message is sent if the key delivered by server is not identical
      • with warnings on client side
      • dummy message is encrypted by server's public key
        • Client behaves as if it hasn't discovered Server's fraud

  • Client can decide not to trust user's device

    • Private key is encrypted on local disk and decrypted by server during connection

In short, this project assumes that the server and the current computer user are malicious. Our goal is to have each potential hostile hold one piece of the puzzle, so that information leaks only if they refer to the same individual.

Dilemma

It is quite inconvenient to manually exchange public keys when users don't trust the server, but for now I am not aware of any alternative solution.

Ideally, users expect the following would happen when they send a message expected

However, no one can prevent the server from doing this

unexpected

MileStone

Feature Status Source Path Lib
Application Protocol Done core/src/codec/msg_codec.rs tokio-util
Message Delivery Done server/src/process.rs N/A
Log Done server/src/init.rs tracing
Config Done core/src/config.rs serde + toml
Client Encryption Done core/encryption/rsa_impl.rs RustCrypto/rsa
Customizable Encryption Done core/traits/encrypt.rs N/A
Exchange Public Key Done server/src/process.rs N/A
Offline Pubkey Mode Coming Next N/A
Update Key Strategy Coming Next N/A
Authentication To Do TBD
Unsafe Group Chat To Do N/A
Expensive Group Chat (e2ee) To Do N/A
File Server (RSA + AES) To Do RustCrypto/aes
Encrypt Private Keys on Client To Do TBD
Chat History Persistence To Do diesel
Horizontal Scaling To Do TBD

Build From Source

Prerequisit: rustc 1.71

git clone https://github.com/realzhujunhao/jhchat.git cd jhchat cargo build --release