#tls #ssl #tcp #crypto


A drop-in replacement for the Rust standard library TCP listener with TLSv1.2 enabled

2 unstable releases

Uses old Rust 2015

0.2.0 Mar 25, 2016
0.1.0 Mar 9, 2016

#881 in Cryptography

23 downloads per month

MIT license

156 lines


A drop-in replacement for the Rust standard library TCP listener with TLSv1.2 enabled.

Note: This library hasn't been tested.


This library abstracts over a regular TCP listener from the Rust standard library, and provides a drop-in* interface replacement that layers TLSv1.2 with a set of strong cipher suites on top of the connection.

It uses the OpenSSL library Rust bindings by Steven Fackler for the underlying TLS functionality. If you don't trust OpenSSL (I don't), you can compile this crate against LibreSSL (instructions provided below).

* It's only necessary to prepend Tls to the regular types (e.g. TlsTcpListener), and write error handling code for the new error types.



  • OpenSSL/LibreSSL headers

How and where you install these headers depends on your platform. A quick Google search should do the trick.


As described in the README for the Rust OpenSSL bindings, there are various ways of compiling this crate, depending on your platform. However, the most universal route, is to configure your build manually with environment variables (and this is required anyway for compiling against LibreSSL). There are only three:

  • OPENSSL_LIB_DIR: Use this to specify the path to the lib dir of your SSL library of choice
  • OPENSSL_INCLUDE_DIR: Use this to specify the path to the include dir of your SSL library of choice
  • OPENSSL_STATIC: [optional] This is a boolean variable specifying whether to statically link against your SSL library

The complete command might look something like this:

$ env OPENSSL_LIB_DIR="/usr/local/opt/libressl/lib" \
        OPENSSL_INCLUDE_DIR="/usr/local/opt/libressl/include" \
        OPENSSL_STATIC=true cargo build


Caesar provides a CaesarError enum type, with a variant for I/O errors and another one for SSL errors. You can find the specifics in the library docs.

extern crate caesar;

use caesar::{TlsTcpListener, TlsTcpStream};
use std::thread;

let key_path = "path_to_certs/key.pem";
let cert_path = "path_to_certs/cert.pem";

let listener = TlsTcpListener::bind("", key_path, cert_path).unwrap()

fn handle_client(stream: TlsTcpStream) {
    // ...

// accept connections and process them, spawning a new thread for each one
for stream in listener.incoming() {
    match stream {
        Ok(stream) => {
            thread::spawn(move || {
                // connection succeeded
        Err(e) => { /* connection failed */ }

// close the socket server


This crate was written to satisfy my needs while writing Postage. As such, only a minimal set of functions was ported over from the TcpListener interface. I might continue to expand this set of functions as the need arises; if you need the functionality earlier, and I haven't implemented it yet, you are welcome to contribute.

To Do

  • Write tests
  • Write proper documentation
  • Code review


This code is licensed under the MIT License. See LICENSE.


~59K SLoC