Crate embedded_mbedtls

An Mbed TLS Rust wrapper for constrained embedded devices.

Currently, this project is developed with no_std CoAPs and LwM2M devices in mind, though usage is not limited to these use cases. Targeting CoAPs and LwM2M, it uses a static Mbed TLS configuration:

• DTLS support
• (D)TLS 1.2
• Client-only
• TLS_PSK_WITH_AES_128_CCM_8 cipher suite support
• CTR_DRBG pseudo-random number generator support

In the future, a dynamic configuration using Rust features might be implemented, but there is currently no roadmap to do so.

Platform abstraction

• Networking with embedded_nal
• Timing with embedded_timers
• Random Number Generation with rand_core

Usage Example

In addition to the following example code, also have a look at the example directory in the git repository. Due to the strong focus on no_std environments, the repository contains working examples for no_std hardware.

use embedded_mbedtls::ssl::{SslConnection, SslContext, Preset};
use nb::block;

// Assuming the variables in use contain a valid hardware abstraction and the server address
// Create the hardware context
let mut ctx = SslContext::new_udp_client_side(net_stack, clock, rng, server_addr);
// Create and configure the connection instance
let mut connection = SslConnection::new_dtls_client(&mut ctx, Preset::Default).unwrap();
connection
    .configure_psk(&[1, 2, 3, 4], "embedded-mbedtls".as_bytes())
    .unwrap();

// Set up connection
block!(connection.handshake()).unwrap();

// Send data
block!(connection.write("Hello, embedded-mbedtls".as_bytes())).unwrap();

// Receive data
let mut buf = [0u8; 1024];
let len = block!(connection.read(&mut buf)).unwrap();

// Close connection
block!(connection.close_notify()).unwrap();

Features

• alloc: enables use of heap allocated contexts, see the explanation in SslConnection

License

Open Logistics License
Version 1.3, January 2023

See the LICENSE file in the top-level directory.

Contact

Fraunhofer IML Embedded Rust Group - embedded-rust@iml.fraunhofer.de

Modules

error

Error type module which defines the MbedtlsError type which describes known Mbed TLS error codes and the Error type for all errors in this library

rng

Random number generation module which defines the CtrDrbg RNG type

ssl

TLS and DTLS interface module which defines the SslConnection type which is the main type to interact with this library and the underlying SslContext type which contains all hardware abstractions

udp

UDP module which defines the UdpContext which is used internally in the SslContext for DTLS connections