Discord Authentication (SimHub / C# WPF)

Quick Start

Default to OAuth2 Authorization Code with PKCE for desktop plugins. Use the system browser, a loopback redirect URI, and minimal scopes.

Implementation Checklist (Least Privilege)

• Confirm required features and map to the minimum Discord scopes.
• Create/locate the Discord application in the developer portal.
• Configure redirect URIs for loopback (e.g., http://127.0.0.1:{PORT}/callback).
• Choose flow:
  • Public client (desktop): Authorization Code + PKCE (no client secret)
  • Confidential client (if applicable): Authorization Code with client secret
• Generate PKCE code_verifier and code_challenge (S256).
• Generate a cryptographically strong state value.
• Launch the system browser to the Discord authorize URL.
• Run a local HTTP listener to receive the redirect and extract code + state.
• Validate state before exchanging the code.
• Exchange code for tokens using HttpClient.
• Store tokens securely using Windows DPAPI (ProtectedData).
• Implement refresh token flow and token expiry checks.
• Add logout flow (revoke tokens and clear local storage).
• Log authentication failures with safe, non-sensitive messages.

Scope Guidance

Only request what the plugin truly needs. Prefer identify alone unless you need more:

• identify: basic user identity
• guilds: list of user guilds
• email: only if email is a strict requirement
• connections: only if you must access linked accounts

Security Guardrails

• Never embed a client secret in a desktop plugin.
• Prefer system browser over embedded web views.
• Use PKCE S256; do not use plain challenge method.
• Use a short-lived, random port for loopback redirect.
• Use HTTPS for non-loopback redirects.
• Protect tokens at rest with DPAPI and keep them out of logs.
• Avoid long-lived refresh tokens if they are not required.

Troubleshooting Workflow

• If redirect never arrives, confirm the listener is running and the redirect URI matches exactly.
• If token exchange fails, verify code_verifier, redirect_uri, and client ID.
• If the user is repeatedly prompted, check refresh flow and token expiry.

Bot Token Flow (Separate from User OAuth2)

Use user OAuth2 when the plugin acts on behalf of a signed-in user (e.g. "Log in with Discord"). Use a bot token when the plugin acts as a bot (e.g. posting to a channel, managing a server). Do not mix the two: different identity, different permissions, different storage.

When to use bot token: User asks for "bot", "post to Discord", "send messages as a bot", or server/channel management without a user login.

Bot token checklist:

• Create or use an existing application in the Discord Developer Portal.
• In the application, open Bot and create a bot (or copy the existing token).
• Copy the bot token once; treat it as a secret (like a password).
• Store the token securely (e.g. DPAPI, user config); never embed in source or expose to the client.
• Call the Discord API with Authorization: Bot <token> (not Bearer).
• Request only the bot permissions the plugin needs (invite URL / OAuth2 URL with bot scope and minimal permissions).
• Isolate bot token storage and usage from user OAuth2 tokens; use separate config/key names.

ContextStream (when available)

• Before adding or changing auth code, use ContextStream search (mode=hybrid) for "Discord OAuth", "token exchange", "PKCE", "plugin auth" to find existing flows in apps/api/ and apps/plugin/. After auth-related decisions (e.g. scopes, PKCE, redirect URI), capture in ContextStream (event_type=decision) with path to Worker or plugin file.

Additional Notes

• Always confirm current Discord OAuth2 endpoints and required parameters in the official docs.

SimHub path (this repo)

The only SimHub path this repo supports is C:\Program Files (x86)\SimHub\. Use it everywhere:

• SimHub install root: C:\Program Files (x86)\SimHub
• Plugins folder: C:\Program Files (x86)\SimHub\Plugins

Do not use placeholders (e.g. SIMHUB_INSTALL_DIR), env overrides, or other install locations in repo docs and skills.

Additional Resources

• Minimal C# snippets: examples.md