OAuth Diagnostic Tool

A cross-platform desktop application for running local OAuth servers and testing OAuth client configurations. Built with Tauri 2 (Rust) and Elm 0.19.

Installation

Pre-built binaries are available on the Releases page. Download the appropriate installer for your platform and install.

macOS Note

The app is not signed with an Apple Developer certificate. After installing, you need to remove the quarantine attribute before it will run:

xattr -cr "/Applications/OAuth Diagnostic Tool.app"

Usage

The app has a split-panel layout. The left side manages OAuth Servers, the right side manages OAuth Client Configurations.

OAuth Servers

OAuth Servers let you spin up local OAuth authorization servers for testing.

Creating a server:

1. Click the create button on the left panel.
2. Enter a name and port (ports auto-assign starting at 9500).
3. Authorization and token URLs are derived automatically from the port.

Managing clients on a server:

• Expand a server card to see its clients section.
• Add clients to a server — each gets an auto-generated client ID (24 chars) and secret (48 chars).
• Delete clients individually; all clients are cascade-deleted when a server is removed.

Starting/stopping a server:

• Use the start/stop controls on each server card.
• Running servers expose the following endpoints:
  • GET /authorize — Authorization endpoint (renders a consent page for authorization_code flow)
  • POST /authorize — Processes approve/deny, issues auth codes
  • POST /token — Token endpoint (supports client_credentials and authorization_code grants)
  • GET /.well-known/openid-configuration — Discovery document
• Client authentication supports both client_secret_post and client_secret_basic.
• Access tokens are opaque UUIDs.
• All running servers are automatically stopped when the app closes.
• A server cannot be deleted while it is running.

OAuth Client Configurations

Client Configurations let you store and test OAuth client details against any OAuth server (local or external).

Creating a configuration:

• Click the create button on the right panel and fill in the OAuth details: issuer, authorization URL, token URL, client ID, client secret, scopes, grant type, and any extra query parameters.
• Alternatively, click "Import" on a server client to pre-fill a configuration from a local server's client.

Editing a configuration:

• Click edit on any existing configuration to modify its details.

Authorizing:

• Click "Authorize" on a client configuration to initiate the OAuth flow.
• For client_credentials, the token request is made directly.
• For authorization_code, the app starts a local callback server on port 5757, opens the authorization URL in Google Chrome, and exchanges the received code for tokens. PKCE (S256) is used automatically. Requires Chrome to be installed.
• Auth results appear in an expandable section on the configuration card.

Development Setup

Prerequisites

• Rust (1.77.2+) — rustup.rs
• Tauri CLI — cargo install tauri-cli
• Elm (0.19.1) — guide.elm-lang.org/install
• Google Chrome — required for authorization_code flows (the app opens Chrome with dev tools directly for the browser-based consent step)

macOS

# Install Xcode Command Line Tools
xcode-select --install

# Install Rust
curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh

# Install Elm (via Homebrew)
brew install elm

# Install Tauri CLI
cargo install tauri-cli

Linux (Debian/Ubuntu)

# System dependencies for Tauri
sudo apt update
sudo apt install -y libwebkit2gtk-4.1-dev build-essential curl wget file \
  libxdo-dev libssl-dev libayatana-appindicator3-dev librsvg2-dev

# Install Rust
curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh

# Install Elm
curl -L -o elm.gz https://github.com/elm/compiler/releases/download/0.19.1/binary-for-linux-64-bit.gz
gunzip elm.gz
chmod +x elm
sudo mv elm /usr/local/bin/

# Install Tauri CLI
cargo install tauri-cli

Windows

# Install Microsoft C++ Build Tools
# Download and run https://visualstudio.microsoft.com/visual-cpp-build-tools/
# Select "Desktop development with C++" workload

# Install WebView2 (pre-installed on Windows 10 1803+ and Windows 11)
# If needed: https://developer.microsoft.com/en-us/microsoft-edge/webview2/

# Install Rust
# Download and run https://rustup.rs

# Install Elm
# Download from https://github.com/elm/compiler/releases/download/0.19.1/installer-for-windows.exe

# Install Tauri CLI
cargo install tauri-cli

Running in Development

cargo tauri dev

This compiles the Elm frontend automatically before launching the app.

Building

cargo tauri build

Compiling the Frontend Only

cd ui && elm make src/Main.elm --output dist/main.js

Tech Stack

• Backend: Rust, Tauri 2, Axum, SQLite (via rusqlite)
• Frontend: Elm 0.19, vanilla CSS
• IPC: Elm ports to Tauri invoke() calls via a JavaScript bridge