azure-iot-sdk-c VS s2n

I'm trying to send data via an edge gateway device. I have set up my edge device which is a linux machine (https://learn.microsoft.com/en-us/azure/iot-edge/how-to-provision-devices-at-scale-linux-symmetric?view=iotedge-1.4&tabs=individual-enrollment%2Cubuntu), now I need to send data from an esp32 device to the iot hub via the edge gateway device. The example code given in the azure iot edge documentation is in C (https://github.com/Azure/azure-iot-sdk-c/blob/main/iothub_client/samples/iotedge_downstream_device_sample/iotedge_downstream_device_sample.c), I need it in the arduino framework for my esp32 device.

Create CA signed certificate, using ECC algorithm for signing, following this guide - https://github.com/Azure/azure-iot-sdk-c/blob/main/tools/CACertificates/CACertificateOverview.md

Another route is the SDKs provided by the cloud vendors (for example, the Azure c sdk). All of the big ones have it.

It seems to support multiple options but requires you pick at least one of them. https://github.com/aws/s2n-tls/blob/main/docs/BUILD.md#build...

I think GnuTLS is probably the second most popular TLS library, after openssl.

I'll also mentions s2n and rustls-ffi for completeness as C libraries, though the former isn't widely used, and the latter is very experimental still. https://github.com/aws/s2n-tls and https://github.com/rustls/rustls-ffi respectively.

I've seen operating on unauthenticated plaintext enough times to list it as my own pet peeve with AES-GCM. But it's a problem for chunked messages too. A few years ago we released a SCRAM mode that makes very minimal changes to AES-GCM so that it mathematically can't operate on unauthenticated plaintext. https://github.com/aws/s2n-tls/tree/main/scram

> The documentation is kind of vague, but apparently you have to re-enable it regularly.[3]

This is correct. And in the end it means more or less that setting the socket option is more of a way of sending an explicit ACK from userspace than a real setting.

It's not great for common use-cases, because making userspace care about ACKs will obviously degrade efficiency (more syscalls).

However it can make sense for some use-cases. E.g. I saw the s2n TLS library using QUICKACK to avoid the TLS handshake being stuck [1]. Maybe also worthwhile to be set in some specific RPC scenarios where the server might not immediately send a response on receiving the request, and where the client could send additional frames (e.g. gRPC client side streaming, or in pipelined HTTP requests if the server would really process those in parallel and not just let them sit in socket buffers).

[1] https://github.com/aws/s2n-tls/blob/46c47a71e637cabc312ce843...

It looks like by default s2n-quic uses this TLS implementation, which is not based on the ring crate (though it is written in C)

https://github.com/aws/s2n-tls

I would be interested in the other SSL implementations:

- https://github.com/awslabs/s2n

- https://boringssl.googlesource.com/boringssl

- https://bearssl.org/

Are these subpar implementations or there are other reasons not to use these?