DEV Community: Chan Aethiopicus

passkey-go: WebAuthn/passkey assertion verification in pure Go

Chan Aethiopicus — Thu, 12 Jun 2025 03:11:26 +0000

Hey all 👋

I've released passkey-go, a Go library for handling server-side passkey (WebAuthn) assertion verification.

It provides both low-level building blocks (CBOR, COSE, authData parsing) and a high-level VerifyAssertion() function compatible with the output of navigator.credentials.get().

🔐 Key Features

✅ Pure Go – No CGO or OpenSSL dependency
🔒 End-to-end passkey (FIDO2/WebAuthn) support
🔧 High-level API: VerifyAssertion(...) to validate client responses
🧱 Low-level parsing: AttestationObject, AuthenticatorData, COSE key → ECDSA
🧪 Strong error types for HTTP mapping PasskeyError
📎 Base64URL-compatible and ES256-only (per WebAuthn spec)
🗂 Example code included for both registration and login

💡 Why?

Most WebAuthn libraries in Go are tightly coupled to frontend flows or rely on external dependencies.

passkey-go aims to be:

🔹 Lightweight
🔹 Backend-only
🔹 Easy to integrate into your own auth logic

You can issue challenges, parse assertions, and verify signatures—all within your own backend service.

📦 Repo:

https://github.com/aethiopicuschan/passkey-go

I'd love any feedback, bug reports, or feature suggestions (e.g., support for EdDSA, Android quirks, etc). Contributions welcome!

Thanks 🙌

FlashKV - compatible with memcached and is slightly faster.

Chan Aethiopicus — Mon, 31 Mar 2025 11:25:59 +0000

Hello! Recently, I wanted to create a KVS for learning purposes, and I’ve been steadily working on developing one that’s compatible with memcached.
Now, it’s finally reached a stage where I can consider it ready for public release, so I’d like to introduce it.

FlashKV

As mentioned in the README, benchmark results show that it’s about 1.1 times faster than memcached. Although there are still many TODOs and it will take some more time before it’s production-ready, I hope you find it interesting.
Also, issues and PRs are very welcome!
Thank you for reading.

Unofficial Live2D Cubism SDK for Golang

Chan Aethiopicus — Wed, 25 Dec 2024 23:58:00 +0000

Introduction

Q. What is Live2D?
A. See Official Site.

Main Topic

If you want to use Live2D, you’ll need the Cubism Framework and Cubism Core. The former has official open-source releases for various environments and programming languages, but the latter is closed and has no alternatives. (For detailed configuration, please refer to the Cubism Core API Reference.)

Now, looking at the Cubism Framework, you can find available versions for Unity, Native, Web and Java.

But I’m really into Golang and Ebitengine!

Deliverables

In the end, I wrote my own code that replicates the Cubism Framework’s functionality and turned it into a library: github.com/aethiopicuschan/cubism-go.

The library also includes a reference renderer for Ebitengine, so if you’re using Ebitengine for development, you can easily incorporate it into your project.

About Cubism Core

Cubism Core is provided as a dynamic library (such as a .dylib).

Let's consider how to use it from Golang. We could use cgo, of course, but this time I employed a library called purego.

You'll need to grapple with a storm of unsafe and uintptr, but it's still much better than using cgo.

In this case, there's an implementation related to the following. Feel free to take a look and experience the storm for yourself!

core.go

I did say you'd have to battle a storm, but purego is a fantastic library, so I encourage everyone to try it out.

That's all. Thank you for reading.

Wasm3 + TinyGo on PSP

Chan Aethiopicus — Fri, 20 Dec 2024 01:59:01 +0000

I will attach the GitHub repository first: wasm3-tinygo-psp.

Main Topic

For some time now, I have wanted to run Golang on the PSP.

However, native compilation to the PSP is impossible (probably).

Certainly, Golang does support GOARCH=mipsle, but it assumes the presence of an operating system. If you attempt to achieve this, you would likely have to navigate a very difficult and thorny path.

So, I chose another way. In other words, the approach is to convert it into WASM using TinyGo.

Now, let's take a look at the actual code.

package main

import "unsafe"

//go:wasmimport debug println
func println(ptr unsafe.Pointer, len int32)

//export start
func start() {
    main()
}

func main() {
    message := "Hello, WebAssembly, from Golang!"
    println(unsafe.Pointer(unsafe.StringData(message)), int32(len(message)))
}

Essentially, we are simply calling the functions provided by the runtime. It's just a Hello World example.

About runtime

There was also an option to use Rust and wasmi for the runtime, but although it worked on emulators like PPSSPP, errors occurred on the actual hardware (as shown in the screenshot below).

I suspect it may be related to kernel mode, but since I ultimately couldn't resolve it, I took a different approach.

Ultimately, the combination of C and Wasm3 worked successfully.

Regarding println, which was mentioned in the earlier code, it is defined on the runtime side as follows.

#define printf pspDebugScreenPrintf

static const void* host_debug_println(IM3Runtime runtime, IM3ImportContext ctx, uint64_t *stack, void *mem)
{
    uint32_t ptr = (uint32_t) stack[0];
    uint32_t length = (uint32_t) stack[1];

    uint8_t* bytes = (uint8_t*)mem + ptr;

    char buffer[256];
    if (length >= sizeof(buffer)) {
        length = sizeof(buffer)-1;
    }
    memcpy(buffer, bytes, length);
    buffer[length] = '\0';

    printf("%s\n", buffer);

    return NULL;
}

Since this is just a demo, this is all for now. However, if you also wrap other functions and make them callable from WASM, you should be able to develop full-fledged applications.

Challenges Faced

Cross-compiling Wasm3

It was necessary to compile Wasm3 using the PSP toolchain.

I created a forked repository to make it easy for everyone to set up the environment, so please take a look for reference: wasm3-for-psp.

TinyGo build options

In the end, I ended up with the command tinygo build -o hello.wasm -target=wasm -no-debug main.go, but it took me quite a bit of time just to arrive at such a simple command. I still have a lot to learn.

Export `main` function

If you are using -target=wasi, TinyGo exports the main function as _start. But in this case, I had to define and export a separate start function.

And then...

This time, I used TinyGo to compile Golang code into WASM, but if other languages can also be compiled into WASM, I believe they can be executed using a similar method. I am passionate about Golang, so I would be happy if someone could give it a try.

That's all. Thank you for reading.

DEV Community: Chan Aethiopicus

passkey-go: WebAuthn/passkey assertion verification in pure Go

🔐 Key Features

💡 Why?

📦 Repo:

FlashKV - compatible with memcached and is slightly faster.

Unofficial Live2D Cubism SDK for Golang

Introduction

Main Topic

Deliverables

About Cubism Core

Wasm3 + TinyGo on PSP

Main Topic

About runtime

Challenges Faced

Cross-compiling Wasm3

TinyGo build options

Export main function

And then...

Export `main` function